SYSTEMS AND METHODS FOR OPERATING EXCAVATION MACHINES

Abstract

An excavation machine is provided. The excavation machine includes an excavation device and an excavation device drive system that powers the excavation device to move cutting tools, wherein the excavation device drive system includes an electric motor and a motor controller, wherein the motor controller is programmed to control the speed of the excavation device drive system. The motor controller sets the speed of the excavation device drive system at a predetermined excavation speed based on a predetermined target power, the predetermined target power being associated with a target torque generated by the electric motor. The speed of the excavation device drive system is set at a predetermined first excavation speed when a power transmitted to the electric motor is below the predetermined target power and at a predetermined second excavation speed to maintain the power transmitted to the electric motor at the predetermined target power.

Description

FIELD OF THE DISCLOSURE

The field of the disclosure relates to excavation machines, and more particularly, to drive arrangements and associated control systems for excavation machines, as well as mechanical arrangements and isolation systems for excavation machines.

BACKGROUND

Control Systems

Various types of excavation machines include a cutter system configured to cut a desired surface, as well as an advancement system configured to advance the cutter system. The cutter system is driven by a cutter drive system, and the advancement system is driven by an advancement drive system. Further, a control system coordinates operation of the cutter device system and the advancement drive system.

Excavation machines may include, for example, chain trenchers, terrain levelers, rocksaws, and underground mining machines. A chain trencher typically includes a trencher boom having cutting tools mounted to a chain that moves around the boom and having a drive sprocket on one end and an idler sprocket on the other end. The chain trencher is configured to cut as the chain is propelled around the boom, moving the cutting tools through a cutter travel path, powered by a cutter drive system. The chain trencher is also configured to cut as the boom is moved along a ground surface, along with the entire machine, by a machine propulsion system, powered by an advancement drive system, or the boom is moved relative to the machine chassis and the ground by a boom positioning system, typically including a hydraulic cylinder. These combined movements result in creating a trench.

A terrain leveler, also referred to as a surface mining machine, may include cutting tools mounted to an outer perimeter of a drum that is a relatively long cylinder. The terrain leveler is configured to cut as the drum is rotated, powered by a cutter drive system, moving the cutting tools through a cutter travel path. The terrain leveler is also configured to cut as the drum is moved along a ground surface, along with the entire machine, by a machine propulsion system, powered by an advancement drive system, or the drum is moved relative to the machine chassis and the ground by a drum positioning system, typically including a hydraulic cylinder. These combined movements result in creating a surface that is parallel to the axis of rotation of the drum.

An underground mining machine, also referred to as a continuous miner or tunneling machine, may include cutting tools mounted to a rotatably driven cutting head mounted to a boom that is in turn pivotally mounted to the machine's main frame. The mining machine is configured to cut as the cutting head is rotated, powered by a cutter drive system, moving the cutting tools through a cutter travel path. The mining machine is further configured to cut as the boom is moved, by a boom positioning system, powered by an advancement drive system. The cutting is performed to excavate material being mined.

Each of these types of excavation machines typically includes a cutter drive system, an advancement drive system, and a control system that coordinates the operation of these systems. Most of the power required for the excavation is used by the cutter drive system. The way the advancement system is controlled affects the power used by the cutting system. Accordingly, there is a relationship between the operation of the advancement system and the power used by the cutter drive system. The material being excavated is often times nonhomogeneous. As a result, in order to optimize performance of the cutting system, the control system needs to have the capability to continuously vary the operation of the advancement drive system in order to compensate for variations in the material being excavated.

Many excavation machines are self-contained mobile machines, typically having a diesel engine that provides power to the cutter drive system, and to the advancement drive system. To optimize production, the control system controls the operation of the advancement drive system in a way to optimize the performance of the cutting system. One way to optimize production is to operate the advancement drive system in a way that the maximum power is drawn from the diesel engine.

The excavation process can result in significant variation in the force required to propel the cutting tools. For instance, the force required to pull a trenching chain of a chain trencher typically varies significantly when the machine is excavating rock. This variation occurs for several reasons. One is the result of the characteristics of the rock and the characteristics of the tools used for excavation.

As an example, FIG. 1 is an illustration of a common cutting tool often referred to as a pick, being pulled in one direction by a cutter drive system while being pushed in a second direction by an advancement drive system. The pick will break material off the face in layers, causing the cutting force to fluctuate as the face is breaking off in these layers. The variation in the force can be significant in relation to the average force. The variation in force required can be different for the different types of excavating machines. Variations in the geometry of the cutting tools, the way that the cutting tools and cutter system engages in the ground, and the way that the cutting structure interacts with the spoils results in variations in the forces required. Thus, the control system has to be flexible to adjust to these variations.

In some systems, a diesel engine provides power to the cutter drive system by converting potential energy in the diesel fuel into mechanical power. The fuel and air systems of the engine can be controlled to vary the power output of the engine by varying the flow rate of fuel and air to the engine. As a result of the variations in the force required to propel the cutting tools, the power required by the cutter drive system for these excavation machines can vary faster than the fuel and air systems of the engine can respond. If the system is being operated at close to the engine's capacity, a sudden increase in the required power can cause the engine to stall. Automated control of the cutter drive system, as is described in U.S. Pat. No. 4,455,770, is a known method that allows machines of this type to operate such that the system can operate at the peak power of the engine with a control system that automatically adjusts the advancement system, as often as every 1/1000^th of a second, as a way to control the excavation process so that the power required by the cutter drive system is close to the maximum power that the engine is capable of producing, while minimizing the potential for stalling the engine. Various control technologies are known for these self-contained machines, including several that monitor the performance of the engine as an indication of the performance of the cutting system, and that make fast adjustments to the advancement system to compensate for the variations in the power required by the cutter drive system.

The cutter drive systems are typically configured to provide a range of operating speeds for the cutting systems. Various drive systems have been utilized to provide the range of operating speeds, each with different performance characteristics. An example is described in U.S. Pat. No. 7,553,258. FIG. 2 is a schematic representation of that prior art chain trencher, shown in a format that will be consistent with the rest of this disclosure. This representation includes a diesel engine, with an associated engine control unit (ECU), mechanically connected to a flywheel. The cutter drive system is illustrated as the drive system for a trencher chain that is mounted on a trencher boom. It is illustrated in FIG. 2 as being driven by the output shaft of a transmission having its input connected to the output shaft of a torque converter. The torque converter is mechanically connected to a flywheel driven by the diesel engine. The advancement drive system is illustrated as a separate drive system for the ground drive. FIG. 2 illustrates this as a ground drive, driven by the output shaft of a hydraulic motor that is fluidly connected to a variable displacement hydraulic pump. Although the hydraulic motor for the advancement drive system is shown as a fixed displacement motor, alternatively, it may be a variable displacement motor. The disclosure of U.S. Pat. No. 7,553,258 describes the ground drive as being comprised of a pair of crawlers, including a pair of pumps and a pair of motors. In operation of the excavation machine, an operator is expected to select a desired speed of the cutter drive system, by selecting a specific gear of the transmission. The control system then monitors the engine speed as I-1, and the output speed of the torque converter as I-2. The control system has an output, O-1, which affects the control of the hydraulic pump that controls the ground drive, the advancement drive system. The controller will have many inputs and outputs that are not shown in this figure, such as those that allow an operator to control engine speed, for instance to select between idle speeds and operating speeds, and to control the speed of the ground drive for steering and general speed control. FIG. 1 is a simplified system diagram, showing only the inputs and outputs associated with controlling load on the cutter drive system during an excavation process, specifically using the engine speed (which is the same as the torque converter input speed) and the output speed of the torque converter as feedback signals.

For the purpose of allowing comparison of various cutter drive systems, five possible operating conditions, and the general response for this prior art system, are described in FIG. 3. The response depicted is intended to describe the potential response of the system to simulated load conditions, and is not intended to represent actual operating conditions. This simulated operating characteristic is intended to demonstrate how the operating characteristics of the engine, and the operating characteristics of the cutter drive system interact. In use, the control system will affect the operation of the advancement drive system, which will affect the cutter drive system. The effect of that control is not considered in this simulation. The overall system response is complex. The following characterizations are intended to illustrate in general how this systems could respond.

FIG. 4 is a plot of a typical diesel engine showing the maximum power and torque that the engine can produce, at various operating speeds. This corresponds to the following operational data at the upper speeds.

Engine Operating Speed,	1700	1800	1900	2000	2100
rev/min
Engine Torque, ft-lbs	1268	1213	1149	1092	1040
Engine Power, Hp	410	416	416	416	416

FIG. 5 is an example operating characteristic of a torque converter, reproduced from FIG. 9 of U.S. Pat. No. 5,337,867.

Assuming that the chain trencher of FIG. 2 has an engine with the operating characteristic described by the torque curve of FIG. 4, and a torque converter having the operating characteristic described by the curve of FIG. 5, and assuming the cutter drive system was able to use all the power generated by this engine, the following scenarios describe how this system could operate in various load conditions. These load conditions are illustrated in FIG. 3, by a series of increases in a variable labeled “Output Torque Required”. This variable is a measurement of the force required to propel the cutting tools. This is not intended to describe a real situation, as the engine would be providing power for the advancement system, and for other systems shown in FIG. 2 as parasitic loads. This is also characterizing the required torque as being relatively consistent, without having short duration variations. In reality, the torque required will have significantly more variation. However, for the purpose of describing the general dynamic response of this system, the required torque is characterized as being relatively consistent. The general response of this system is shown by the speed of the cutting system, and how the speed changes in response to changes to the output torque required.

FIG. 3 illustrates the load on the cutter drive system as the Output Torque Required. With the system illustrated in FIG. 2, the force required to propel the cutting tools will be provided by the trencher chain. A tensile force in the trencher chain, sometimes called line-pull, will be provided by a torque generated in the output shaft of the transmission. The torque generated at the output shaft of the transmission will be provided by the torque generated at the output shaft of the torque converter. The torque requirement that is referenced in FIG. 3 is intended to be the torque at the output shaft of the torque converter, which is a measurement of the force required to propel the cutting tools.

Referring to FIG. 3, during time period A, at the start of operation, the Output Torque Required (output torque at the output shaft of the torque converter) will increase to 1000 ft-lbs. This would occur as the advancement system moves the trencher boom into engagement with the trench face, the torque-load on the output shaft of the torque converter would increase, to the point labeled 9-1 on FIG. 3. At this load condition assume that the engine is operating at 2100 rpm, and the engine's torque output is 1040 ft-lbs. At that condition the characteristics of the torque converter could be adapted to operate, at that load condition, as illustrated at the operating characteristic represented by the point 8-1 in FIG. 5. At that condition, the torque converter would generate 1040 ft-lbs torque, as a result of the torque ratio being 1.0, with an output speed of 2037 rpm as a result of the speed ratio of 0.97. Thus, the system is illustrated as having the capacity to provide the line pull required, with 3% slip, where the output shaft speed is 97% the engine speed.

The force required to move the trencher chain could increase slowly during time period B as the advancement system continues to push the trencher boom and chain harder against the formation being excavated. During this time period the required torque is illustrated at point 9-2 as increasing to 1150 ft-lbs. Assuming the operating characteristic of the torque converter allows it to transfer this torque at the point 8-2 in FIG. 5, the speed ratio will drop to 0.87, while the torque ratio will remain at 1.0. In order to generate the required torque, following the engine torque curve, the engine speed will drop to 1900 rpm. The output speed of the torque converter will drop to 1653 due to the speed ratio dropping to 0.87.

The force required to move the trencher chain could increase rapidly during a time period C as the cutters engage with harder material, as an example. This is illustrated as the point 9-3 where the line pull required for maintaining chain speed is equivalent to 1250 ft-lbs at the output shaft of the torque converter. The operating characteristics of the torque converter could result in operation required for that load condition as represented by point 8-3: with the speed ratio dropping to 0.82 and the torque ratio increasing to 1.05. In order to generate the required torque at the output of the torque converter with the Torque Ratio of 1.05, the engine will need to generate 1190 ft-lbs. In order to generate that torque, the engine speed will be pulled down to 1800. With the resulting torque converter speed ratio of 0.79 the output shaft speed will drop to around 1476 rpm.

The force required to move the trencher chain could increase rapidly during a time period D to where the line pull required for maintaining chain speed is equivalent to 1500 ft-lbs at the output shaft of the torque converter as is represented by point 9-4 in FIG. 3. The operating characteristics of the torque converter could result in operation required for that load condition as represented by point 8-4: with the speed ratio dropping to 0.7 and the torque ratio increasing to 1.2. In order to generate the required torque at the output of the torque converter with the torque ratio of 1.2, the engine will need to generate 1250 ft-lbs. In order to generate that torque, the engine speed will be pulled down to approximately 1700 rpm. With the resulting torque converter speed ratio of 0.70 the output shaft speed will drop to around 1190 rpm.

The force required to move the trencher chain could increase rapidly during a time period E to where the line pull required for maintaining chain speed is equivalent to 1800 ft-lbs at the output shaft of the torque converter as is represented by point 9-5 in FIG. 3. The operating characteristics of the torque converter could result in operation required for that load condition as represented by point 8-5: with the speed ratio dropping to 0.5 and the torque ratio increasing to 1.43. In order to generate the required torque at the output of the torque converter with the Torque Ratio of 1.43, the engine will need to generate 1258 ft-lbs. In order to generate that torque, the engine speed will be pulled down to approximately 1600 rpm. With the resulting torque converter speed ratio of 0.50 the output shaft speed will drop to around 800 rpm. At this operating condition the engine characteristic illustrated in FIG. 4 would result in the engine generating less horsepower, even though the engine's output torque has increased. Thus, this is not an optimal operating condition for the engine.

This representative operating characteristic illustrates how this prior art drive system could respond to increases in the required force, as could occur without a compensating control of the advancement system. It is not intended to represent actual data, but rather to be representative of the expected general dynamic characteristic of a system of this type, when coupled to a representative engine. The operating characteristics of a system like this will be determined by the design of the torque converter, typically by specific physical attributes of the torque converter, where these physical attributes are tailored to provide specific operating characteristics.

The operation of this prior art is expected to include a process where an operator will manually select an operating characteristic of the ground drive system, the controller will generate an output, O-1, that will control the variable displacement pump to achieve a displacement that provides a desired operating characteristic of the ground drive, typically a specific propulsion force generated by the ground drive system. As the excavation process proceeds, the controller is then able to automatically adjust the displacement of the hydraulic pump, by adjusting O-1, to slow-down the ground drive, or to reduce the propulsion force generated by the ground drive, when the system requires excessive power from the cutter drive system. Various ways of controlling the system are described in U.S. Pat. No. 7,553,258.

FIG. 6 illustrates how this prior art drive system could respond with automated control of the advancement system. In this figure the time period A, intended to be the same as was illustrated in FIG. 3, could occur as the trencher boom has engaged the ground, and the power required to keep the trencher chain moving increases. This results in increasing the load on the engine, and moves the performance of the torque converter to the point 8-1 illustrated on FIG. 5. During a time period B the torque required begins to increase. FIG. 6 illustrates the system response assuming that a sensor and control system detects when the output speed of the torque converter is below a 1750 rpm, and subsequently affects the advancement system to reduce the output torque requirement. The required output torque will drop during time period C, as a result of the change to the advancement system. The advancement system will change during time period D resulting in an increase in the required output torque until the output speed of the torque converter drops again to 1750 rpm at the end of time period D. In this way the control system can maintain operation of the system so that the torque converter operates within certain operating characteristics, such as between the points labeled on FIGS. 5 as 8-1 and 8-2.

Another example of related prior art is found in U.S. Pat. No. 7,930,843. FIG. 7 is a schematic representation of that prior art, shown in a format that will be consistent with the rest of this disclosure. This representation includes a diesel engine, with an associated engine control unit (ECU), mechanically connected to a flywheel The cutter drive system is illustrated as the drive system for a trencher chain mounted on a trencher boom. It is illustrated in FIG. 7 as being driven by the output shaft of a hydraulic motor which is fluidly connected to a hydraulic pump that is mechanically connected to a flywheel driven by the diesel engine. This system could have a reduction gearbox, such as a planetary gearbox, positioned between the fixed displacement motor (which could alternatively be a variable displacement motor) and the trencher chain. The advancement drive system of FIG. 7, similar to that of FIG. 2, is intended to describe various possible configurations in a simplified schematic. In this system an operator selects a desired speed of the cutter drive system by selecting a displacement of the variable displacement pump that is controlled by the controller generating an output signal O-1 for controlling the pump. When the displacement increases, the speed of the hydraulic motor will increase. When an operator has selected the desired speed of the cutting system, it will typically not be changed during the short-term periods illustrated in this disclosure to characterize the system's general dynamic response during operation. Although the pump displacement could be changed, the response time of this system is not capable of implementing changes quickly enough to make that practical for the short-term periods that this disclosure is describing. Thus, for this drive arrangement, the pump displacement will be assumed to be fixed during the time periods illustrated, so that there is typically a fixed relationship between the rotational speed of the engine and the rotational speed of the output shaft of the motor. During excavation, the control system monitors the engine speed as I-1.

U.S. Pat. No. 7,930,843 describes the controller also monitoring the output pressure of the hydraulic pump as I-2. The control system has an output, O-2, which affects the control of the hydraulic pump that controls the ground drive, the advancement drive system. FIG. 7 is a simplified system diagram, showing only the inputs and outputs associated with controlling load on the cutter drive system during an excavation process, specifically using the engine speed and the output pressure of the hydraulic pump as feedback signals.

For the purpose of allowing comparison to the drive system having a torque converter, a chain trencher, with an engine having the same operating characteristic, and with a hydrostatic system for the cutter drive system as shown in FIG. 7, could operate in response to the load conditions illustrated in FIG. 8. For this comparison, assume that the trencher chain is propelled by connection to an output shaft of a gearbox, and the input shaft of the gearbox is connected to the output shaft of the fixed displacement motor. Assume that the operator has adjusted the displacement of the variable displacement pump to provide an operating speed where the speed of the output shaft of the fixed displacement motor of the hydrostatic drive system of FIG. 7 matches the output speed of the torque converter system of FIG. 2, when both are operating at an engine speed of 2100 rpm. That load condition that was illustrated at the point 9-1 of FIG. 3, for the system of FIG. 2, was based on an assumption that the engine was operating at 2100 rpm with an output torque of 1040 ft-lbs, resulting in an output speed of the torque converter of 2037. In order to allow comparison between the general system responses, assume that the gearbox of the machine of FIG. 7 has a gear reduction that results in the output speed of the motor of FIG. 8 being equivalent to the output speed of the torque converter of FIG. 2. This gear reduction is not required. The hydrostatic system could use a type of motor where the output shaft speed could be significantly lower. However, for the purposes of comparing possible system response, if the hydrostatic system of FIG. 7 had this gear reduction, then at the operating condition represented by 11-1 of FIG. 8, assume the output shaft of the hydraulic motor is 2037 rpm, the engine speed is 2100, the engine is producing 1040 ft-lbs torque or 416 Hp. In order for a hydrostatic system to provide that operating condition it would be operating at 93% efficiency. In practice this is higher than what a hydrostatic system is expected to be capable of. Hydrostatic systems are often assumed to operate in the 80% to 85% efficiency range. However, for the purposes of this comparison, the assumption will be that the hydrostatic system could be capable of operation at 93% efficiency. With that assumption, it is capable of generating 997 ft-lbs torque, which is assumed to be adequate to meet the torque requirement at this load condition. The following is a description of possible system response to variations in the operating conditions, from starting at the operating point labelled 11-1. The variations in the torque required will be the same as were previously described for the torque converter system, and the response of this system is depicted as the variation of the output speed. This characterization of the performance of a hydrostatic system is greatly simplified. The system's efficiency will vary with changes in operating pressures and speeds, so the assumption of a system efficiency is not representative of exactly how this system would respond. The response depicted in FIG. 8 is intended only to be a general indication of the expected system response.

During time period A the required torque increases relatively slowly to the operating point labelled 11-1 described above. During time period B the torque required to maintain movement of the trencher chain increases relatively slowly to the condition 11-2 where the required torque is 1150 ft lbs. In order to generate that torque the engine will be pulled down to approximately 1800 rpm, which will result in an output speed of 1750 rpm and an output torque capability of 1150 ft-lbs. The variation in the output speed is due to the engine's response to the increasing load. During time period C the torque required to maintain movement of the trencher chain increases faster to the condition 11-3 where the required torque is 1250 ft lbs. In order to generate that torque the engine will be pulled down to approximately 1600 rpm, which will result in an output speed of 1560 rpm. At this operating point the engine is also loaded to the point where it is able to provide the required torque, but its speed is pulled down to a point on its operating curve where it is not capable of generating the same power. Thus, this is not an optimal operating point for the engine. During time period D the torque required to maintain movement of the trencher chain increases to the condition 11-4 where the required torque is 1500 ft lbs. During this time period the exaction machine with a hydrostatic transmission would not be capable of responding. The torque required would exceed that of the maximum engine torque, and the engine would stall.

The operating scenario of FIG. 8 illustrates how the prior art system, of FIG. 7, could respond, in general, to increases in the required force. The operation of this prior art includes a process where an operator manually selects an operating characteristic of the ground drive system to achieve a desired excavation process. The operator control will result in the controller generating an output, O-2, that will control the variable displacement pump to achieve a displacement that provides a desired operating characteristic of the ground drive, typically a specific ground speed, or a propulsion force generated by the ground drive system. The operating scenario shown in FIG. 8 is not intended to illustrate operation wherein this advancement system is controlled in any specific manner. In an actual implementation as the excavation process proceeds, the controller would automatically adjust the displacement of the hydraulic pump, by adjusting the output O-2, such as to slow-down the ground drive, when the system requires excessive power from the cutter drive system, as can be determined by monitoring the engine speed as I-1 or the hydraulic pressure as I-2. Various ways of controlling the system are described in U.S. Pat. No. 7,930,843. None of these automated controls techniques are reflected in the operating characteristic depicted in FIG. 8.

The operating characteristics illustrated in FIGS. 3 and 8 for these two prior art drive systems are intended to illustrate how these systems provide similar performance in operating conditions where the engine is operating at close to maximum power, but as the load increases towards the maximum torque condition that the engine is capable of generating, these systems respond differently.

When operated at close to full load, a system having a torque converter transmission can respond to a sudden increase in load by providing the required torque, but with a significant reduction in output speed.

Further, a system having a hydrostatic transmission can overload the engine. The control systems for the advancement drive systems have been developed to optimize the performance of these transmission systems, wherein the performance characteristics of the transmissions are matched to the control characteristics for the advancement systems.

Accordingly, there is an ongoing need to optimize the drive systems and the associated control systems, particularly in response to advancements in electric drive systems and to advancements in torque converter technologies.

Mechanical Arrangements

Various types of excavation machines include a cutter system configured to cut a desired surface, as well as an advancement system configured to advance the cutter system. For example, a chain trencher typically includes a digging chain that is driven around a boom. The boom may be selectively raised and lowered to dig a trench (e.g., in the earth) using the digging chain. In another example, a surface miner includes a drum having a plurality of teeth. The drum is driven such that the drum rotates and the teeth dig into a surface (e.g., of the earth).

Cutting tools for excavation machines (e.g., a digging chain of a chain trencher and a drum for a surface miner) are typically driven by an electrical and/or mechanical motor. For example, FIG. B5 is a simplified diagram of a known mechanical arrangement B10 for a chain trencher.

As shown in FIG. B5, for at least some known chain trenchers, the mechanical arrangement B10 includes a head shaft B12 driven by a first rotational drive unit B14 and a second rotational drive unit B15. The rotating head shaft B12 drives a digging chain around a boom B16. In the mechanical arrangement B10, the first and second rotational drives units B14 and B15 each include a motor B18 and a gearbox B20.

The gearboxes B20 support the head shaft B12 in the arrangement shown in FIG. B5. Specifically, a pilot portion B22 of each gearbox B20 engages a main frame B24 of the chain trencher. The head shaft B12 is then supported by bearings B26 in the gearboxes B20. With this arrangement, the components within the gearboxes B20 rotate relative to the main frame B24 to rotate the head shaft B12. Further, torque arms B30 holds the gearboxes B20 in place and prevent counter rotation of the gearboxes B20 relative to the main frame B24. In this arrangement, bearings B26 in gearboxes B20 take all of a radial load resulting from cutting action. Further, this arrangement relies on a clearance between a pilot of the main frame B24 and the pilot portion B22 of each gearbox B20 to prevent statically indeterminate loading (i.e., more than two bearings on a shaft). Accordingly, bearing loading may be unpredictable in such arrangements.

FIG. B6 is a simplified diagram of another known mechanical arrangement B40 for a chain trencher. The mechanical arrangement B40 does not include a gearbox. Instead, a motor B42 (e.g., a slow-speed hydraulic motor) is directly mounted to a head shaft B44. The motor B42 is supported by the head shaft B44 via first bearings B46. Further, the head shaft B44 is supported by a main frame B48 via second bearings B50. A torque arm B52 is coupled to the motor B42 to prevent counter rotation of the motor B42. Notably, this arrangement generally requires a motor capable of generating a relatively high torque, as no gearbox is included.

Accordingly, there is a need for alternative mechanical arrangements that avoid the issues associated with at least some known mechanical arrangements. For example, the mechanical arrangement of FIG. B5 requires that the gearbox support the head shaft. Further, the mechanical arrangement of FIG. B6 is not capable of being implemented using lower torque motors.

In addition, in at least some known surface miner excavation machines, the motor for driving the drum is located inside of the drum, which may make accessing the motor (e.g., for repair and/or replacement operations) relatively difficult. Further, as the motor is located inside the drum, the motor may be difficult to cool and is located relatively close to the material being cut by the excavation machine. In addition, the cutting tools of at least some known excavation machines are driven using a single motor and single gearbox. This requires a single motor to generate all the power necessary to operate the cutting tool, instead of generating the power with multiple motors. Further, in the event of failure of one of the single motor and the single gearbox, the cutting tool will fail to operate properly.

Accordingly, there is also a need for alternative mechanical arrangements that enable easily accessing the motor. Further, there is a need for alternative mechanical arrangements that incorporate multiple motors and/or gearboxes to improve operation and reliability of the excavation machine.

Isolation Systems

Various types of excavation machines include a cutter system configured to cut a desired surface, as well as an advancement system configured to advance the cutter system. For example, a chain trencher typically includes a digging chain that is driven around a boom. The boom may be selectively raised and lowered to dig a trench (e.g., in the earth) using the digging chain. In another example, a surface miner includes a drum having a plurality of teeth. The drum is driven such that the drum rotates and the teeth dig into a surface (e.g., of the earth).

Cutting tools for excavation machines (e.g., a digging chain of a chain trencher and a drum for a surface miner) are typically driven by an electrical and/or mechanical motor. In at least some known systems, the motor is coupled to the cutting tool such that vibrations and/or oscillations generated or experienced by the cutting tool are also experienced by the motor. For example, in a chain trencher or surface miner, there may be significant vibrations and/or oscillations of the machine frame during operation of the excavation machine. These vibrations and/or oscillations may result, for example, from the cutting tool impacting the material being excavated, as well as that same material tumbling against the cutting tool.

In some known systems, the motor may also experience vibrations and/or oscillations generated by other components of the excavation machine (e.g., a diesel engine of the excavation machine). These vibrations and/or oscillations may impair operation of the motor, and may ultimately result in damage to the motor or failure of the motor.

Accordingly, there is a need to isolate a motor of an excavation machine from vibrations and/or oscillations generated by other components of the excavation machine.

SUMMARY

In one embodiment, an excavation machine is provided. The excavation machine includes an excavation device having a plurality of cutting tools mounted thereon and an excavation device drive system that powers the excavation device to move at least one of the plurality of cutting tools through a cutter travel path. The excavation device drive system includes an electric motor and a motor controller, the electric motor being powered by a power supply. The motor controller is programmed to control a speed of the excavation device drive system via a control algorithm, wherein, the control algorithm, when executed by the motor controller, causes the motor controller to set the speed of the excavation device drive system at a predetermined excavation speed based on a predetermined target power, the predetermined target power being associated with a target torque generated by the electric motor. The speed of the excavation device drive system is set at a predetermined first excavation speed when a power transmitted to the electric motor is below the predetermined target power and at a predetermined second excavation speed to maintain the power transmitted to the electric motor at the predetermined target power, the predetermined second excavation speed being less than the predetermined first excavation speed and being associated with an increase in the target torque generated by the electric motor. The speed of the excavation device drive system is set at the predetermined second excavation speed when a first force required to propel at least one of the plurality of cutting tools exceeds a second force that the excavation device drive system can generate with the excavation device drive system operating at the predetermined first excavation speed at the predetermined target power.

In another embodiment, an excavation machine is provided. The excavation machine includes a diesel engine having an engine control unit (ECU) that controls and monitors a fuel system and an air intake system that provides diesel fuel and combustion air to the diesel engine, wherein the ECU calculates an engine load parameter at least partially based on a fuel amount and a flow of air. The excavation machine also includes an active cutting system and a power transmission device that transfers power from the diesel engine to the active cutting system at a variable operating speed, wherein the variable operating speed is based on an operating parameter that affects a variable torque and a speed characteristic of the power transmission device. The excavation machine further includes an advancement system that propels the active cutting system during excavation and a control system that controls the advancement system based on the variable operating speed of the power transmission device, and wherein the control system controls the operating parameter of the power transmission device based on the engine load parameter.

In yet another embodiment, a mechanical arrangement for an excavation machine is provided. The mechanical arrangement includes a cutting tool, a head shaft coupled to the cutting tool and defining a longitudinal axis, a gearbox coupled to the head shaft such that the head shaft supports the gearbox, and a motor coupled to the gearbox, wherein the motor is offset from the longitudinal axis of the head shaft, and wherein the motor is configured to drive rotation of the head shaft and the cutting tool via the gearbox.

In still yet another embodiment, a mechanical arrangement for an excavation machine is provided. The mechanical arrangement includes a cutting tool, a head shaft coupled to the cutting tool, at least one gearbox coupled to the head shaft such that the head shaft supports the gearbox, and a plurality of motors, wherein the plurality of motors are configured to drive rotation of the head shaft and the cutting tool, and wherein at least one of the plurality of motors is coupled to the at least one gearbox.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is an illustration of a known cutting tool;

FIG. 2 is a schematic representation of a known chain trencher including a torque converter for the cutter drive;

FIG. 3 is an operating condition diagram for the chain trencher shown in FIG. 2;

FIG. 4 is a plot showing an engine operating curve for a diesel engine;

FIG. 5 is a plot showing an example operating characteristic of a torque converter;

FIG. 6 is an operating condition diagram for the chain trencher shown in FIG. 2 with automated control of the advancement system;

FIG. 7 is a schematic representation of a known chain trencher including a hydrostatic transmission for the cutter drive;

FIG. 8 is an operating condition diagram for the chain trencher shown in FIG. 7;

FIG. 9 is a simplified schematic of a first embodiment of the present disclosure having an electric transmission for the cutter drive;

FIG. 10 is an operating condition diagram for the chain trencher shown in FIG. 9;

FIG. 11 is an operating condition diagram comparing the chain trencher shown in FIG. 9 with the chain trenchers shown in FIGS. 2 and 7;

FIG. 12 illustrates how the system of FIG. 9 may respond when a control system automatically controls an advancement drive system;

FIG. 13 is a flow diagram of one embodiment of a control algorithm in accordance with the present disclosure;

FIG. 14 is a simplified schematic of a second embodiment of the present disclosure with an electric transmission for the cutter drive and for the advancement drive;

FIG. 15 is a simplified schematic of a third embodiment of the present disclosure with a mechanical transmission having a controllable torque converter for the cutter drive;

FIG. 16 is a flow diagram of an example method for operating an excavation machine in accordance with the present disclosure;

FIG. B1 is a perspective view of a chain trencher as one example of an excavation machine in accordance with the present disclosure;

FIG. B2 is a side view of the chain trencher shown in FIG. B1 with the boom in a raised position;

FIG. B3 is a side view of the chain trencher shown in FIG. B1 with the boom in a lowered position;

FIG. B4 is a cross-sectional view of the chain trencher taken along line B4-B4 shown in FIG. B2;

FIG. B5 is a simplified diagram of a known mechanical arrangement for an excavation machine;

FIG. B6 is a simplified diagram of another known mechanical arrangement for an excavation machine;

FIG. B7 is a simplified diagram of one embodiment of the mechanical arrangement for a chain trencher according to the present disclosure;

FIG. B8 is an enlarged view of a portion of the diagram of FIG. B8;

FIG. B9 is an alternative embodiment of a mechanical arrangement for a chain trencher that includes a two-motor drive arrangement;

FIG. B10 is one embodiment of a mechanical arrangement for driving a surface miner;

FIG. B11 is a perspective view of one embodiment of a surface miner;

FIG. B12 is a side view of the surface miner shown in FIG. B11;

FIG. B13 is a top view of the surface miner shown in FIG. B11;

FIG. B14 is a front perspective view of a mechanical arrangement of the surface miner shown in FIG. B11;

FIG. B15 is a rear perspective view of the mechanical arrangement shown in FIG. B14;

FIG. B16 is a simplified diagram of one embodiment of a mechanical arrangement that may be used with a surface miner;

FIG. B17 is a simplified diagram of one embodiment of a mechanical arrangement that may be used with a chain trencher;

FIG. C1 is a perspective view of one embodiment of a surface miner;

FIG. C2 is a side view of the surface miner shown in FIG. C1;

FIG. C3 is a top view of the surface miner shown in FIG. C1;

FIG. C4 is a cross-sectional view of the surface miner taken along line C4-C4 shown in FIG. C3;

FIG. C5 is a simplified schematic diagram of an engine generator mount that may be used with the surface miner shown in FIG. C1;

FIG. C6 is a perspective view of the engine generator mount shown in FIG. C5; and

FIG. C7 is an alternative simplified schematic diagram of the engine generator mount shown in FIG. C5.

Corresponding reference characters indicate corresponding parts throughout the drawings.

DETAILED DESCRIPTION

Control Systems

FIG. 9 is a simplified schematic of a first embodiment of the present disclosure having an electric-mechanical transmission (EMT) for a cutter drive system, as the drive system for a trencher chain mounted on a trencher boom.

Although at least some of the embodiments described herein are described in the context of a chain trencher, those of skill in the art will appreciate that the systems and methods described herein may be implemented in other excavation machines as well (e.g., terrain levelers, underground mining machines, etc.).

The cutter drive system of FIG. 9 is illustrated having a gearbox with an output connected to the trencher boom. This connection will have the output shaft of the gearbox connected to a drive sprocket that the trencher chain wraps around, in a way that the rotation of the drive sprocket, by the output shaft of the gearbox, will pull the trencher chain around the trencher boom, converting torque transferred by the output shaft of the gearbox into line pull, a force pulling the chain along the trencher boom.

The input shaft of the gearbox is connected to the output shaft of an electric motor. In one embodiment, this is a permanent magnet synchronous motor that is electrically connected to a motor controller and inverters. Other suitable types of motors can be used, such as a permanent magnet asynchronous motor or a switched reluctance motor. For example switched reluctance motors are relatively simple from a mechanical standpoint, and may be more reliable than other types of motors.

The motor controller and inverters are electrically connected to a generator. The motor controller and inverters take electrical power created by the generator, in the form of direct current, in one embodiment at 650 Volts, or a range such as 550 to 750 Volts, and apply current to a series of coils in the motor to generate a rotating magnetic field. The motor controller affects the rotational speed of this rotating magnetic field in order to affect the rotational speed of the output shaft of the motor. At the same time the motor controller monitors the level of current and the output speed of the motor, by which it can assess the power transmitted to the electric motor. The motor controller can be programmed to maintain a consistent output speed, and/or to transmit a target, or set power. With the capabilities of the sensing and control electronics that are commercially available, the motor controller is able to make adjustments to affect the rotational speed of the magnetic field, and adjustments to the level of current applied to the coils within the motor, to affect the output speed and the power transferred by the motor in very short periods of time (e.g., in milliseconds).

In the embodiment of FIG. 9, the generator is powered by a diesel engine. However, those of skill in the art will appreciate that the generator (and thus, the motor controller and motor) may be powered using any suitable power source. For example, in some embodiments, power is supplied from one or more energy storage devices (e.g., a battery system), or supplied from an energized power line (e.g., as part of a trolley system that supplies power using overhead power lines).

The generator, motor, power electronics, and the main components of the electric-mechanical transmission form a complex system. The dynamic response of this system, and how it will react to the changes in torque required to drive the cutting system of an excavation machine, such as to propel a trencher chain around the trencher boom, will be influenced by several factors. Those factors may include, for example, the type of cutting tools, the type of ground conditions, and the amount of power available to power the cutting system, which may be affected by ambient temperature (e.g., in a hotter ambient condition, the system will require more power for cooling, which will reduce the power available to the cutting system drive).

In one embodiment, the control logic of the motor controller and the power electronics will include operating parameters, such as a desired operating speed as the primary control parameter, and a target maximum power as a secondary control parameter. The motor controller is able to make adjustments to the electric current transferred to the motor to control the speed, in a no load or low load situation, to equal the desired operating speed. A no-load condition is intended to describe the situation where the trencher chain moves around the trencher boom, while the cutters on the chain are not contacting any material. In this condition, the cutter system will require some power to rotate the trencher chain, but that will be significantly lower than the power required during excavation, when the cutters have engaged the material being excavated. In this no load condition, the motor controller will make adjustments to the timing of the application of current to the motor's coils to achieve a rotational speed of the magnetic field required to achieve the desired output speed of the motor.

The dynamic characteristics of this power transmission system, with the permanent magnet synchronous motor of some embodiments, will be defined by the motor controller, also known as a Variable Frequency Drive (VFD) of this embodiment. There is no mechanical connection between the engine and the cutter drive system. Thus, the operating characteristics of the engine do not affect the dynamic operating characteristics of the cutter drive system. The controller is able to make adjustments to how current is applied to the various components of the motor to influence the rotational speed of the rotating magnetic field, to affect the output speed of the motor, and to control the level of current applied to the components of the motor, in order to influence the torque generated by the motor. These adjustments can be implemented quickly enough to respond to the typical variations in the force required to propel the cutting tools to maintain a consistent maximum power draw. The overall efficiency of the system including the generator, inverter, and motor will remain relatively consistent throughout significant variation in the rotational speed and torque.

In some embodiments, if the torque required to propel the cutting tools increases to a level wherein the current required to produce the resulting torque exceeds the motor's capacity, then the motor controller will continue to reduce speed, and it will hold torque at this maximum torque.

The following is an explanation of how the performance of this power transmission system can respond to variations in conditions similar to those described previously for the torque converter type and the hydrostatic type systems.

The system of FIG. 9 also includes an advancement system as a ground drive system having a variable displacement hydraulic pump and fixed displacement motor. This system controls how the trencher boom is moved through the material being excavated. The advancement system could alternatively be an actuator other than a ground drive system that moves the trencher boom. The ground drive system illustrated specifically in FIG. 9 is intended to be generically representative of an advancement system.

The controller may have many other devices connected to it (not shown) to enable control of speed and direction of travel of the advancement system. The controller may also be connected to one or more input devices that allow an operator to control the engine speed. These are, likewise, not illustrated. FIG. 9 illustrates the inputs and outputs that are involved in controlling the excavation process.

In one embodiment, the operation of system shown in FIG. 9 includes the following processes/steps for a trencher:

• • 1) An operator will position the machine and its boom for an excavation. The operator will then adjust the speed of the cutter drive system. This is controlled by a communication labelled as output O-1 being sent by the controller to the motor controller that allows an operator to select a desired speed of the cutter system. The O-1 communication signal will also contain information that defines other operating parameters of the cutter drive system, such as a target power. As noted above, in the initial no-load condition, the target speed will be the primary control parameter;
  • 2) Once the cutter drive system is operating at the desired speed, an operator is expected to operate a separate control that will result in the control system sending a signal O-2 to the variable displacement hydraulic pump to affect the ground drive system. This is a specific type of advancement system, shown for this embodiment. Other types of advancement systems are typical, including an actuator that can lift or lower the trencher boom. Although FIG. 9 illustrates a ground drive system, specifically, as the advancement system, this disclosure intends this to generically apply to various types of advancement systems.
  • 3) After the advancement system initiates movement, the trencher chain will start to engage with the material being excavated, and the power required to keep the trencher chain moving will increase.

For the purpose of comparison with the prior art systems, the following possible operating conditions are based on assumptions including: an engine having the same operating characteristics is utilized; the gearbox of the machine of FIG. 9 has a gear reduction that results in the output speed of the motor being equal to the output speed of the torque converter of FIG. 2 and the hydraulic motor of FIG. 7; and the efficiency of the generator, the inverter, and the motor results in performance of system at the first operating point equivalent to the performance of the torque converter system and the hydrostatic system described above. Similar to the assumptions made previously for the hydrostatic system, this assumed efficiency is not intended to necessarily be realistic, but is assumed simply to allow comparison with the other two systems. The following operating characteristics would be expected with the overall system efficiency for the electric-mechanical transmission of 93%.

With these assumptions, the possible performance conditions of the system of FIG. 9 are illustrated in FIG. 10.

During a first time period A, at the start of operation, the line pull required for maintaining chain speed may gradually increase to a level equivalent to 1000 ft-lbs at the output shaft of the motor, as the advancement system moves the trencher boom into engagement with the trench wall, the load on the output shaft of the motor would increase, to the point labeled 12-1 on FIG. 10, where the output speed is 2037 rpm.

The force required to propel the trencher chain could increase slowly during time period B as the advancement system continues to push the trencher boom and chain harder against the formation being excavated. During this time period the required torque is illustrated at point 12-2 as increasing to 1150 ft-lbs. Assuming a system efficiency of 93% and an engine output power of 416 hp, the motor would be capable of maintaining an output speed of 1765 rpm at that required load. The dynamic response of the electric-mechanical transmission to this increase in required torque will result in the system's ability to adjust its operation to provide this output speed, while providing the required torque within a very short response time.

Since the power used at this operating point is still 416 Hp, the load on the engine would be the same, and the engine could be operating at the same speed as noted for the load condition of point 12-1. The engine speed could also be operating at a lower speed. With the electric-mechanical transmission of this embodiment there is no definite relationship between the speed of the engine and the output speed of the motor. The power produced by the engine remains the same across various engine speeds. The engine will be capable of providing the required power, regardless of its output speed, while that the power electronics of the electric-mechanical transmission is able to compensate.

The force required to move the trencher chain could increase rapidly during a time period C as the cutters engage with harder material, as an example. This is illustrated as the point 12-3 where the line pull required for maintaining chain speed is equivalent to 1250 ft-lbs at the output shaft of the motor. Assuming a system efficiency of 93% and an engine input power of 416 hp, the motor would be capable of maintaining an out speed of 1624 rpm at that required load.

Since the power used at this operating point is still 416 Hp, the load on the engine would be the same, in terms of power required. As noted above, the engine speed could be different, but the assumption is the engine will be capable of providing the required power regardless of its output speed, and that the power electronics of the electric-mechanical transmission are able to compensate.

The force required to move the trencher chain could increase rapidly during a time period D to where the line pull required for maintaining chain speed is equivalent to 1500 ft-lbs at the output shaft of the electric motor as is represented by point 12-4 in FIG. 10. Assuming a system efficiency of 93% and an engine input power of 416 hp, the motor would be capable of maintaining an out speed of 1353 rpm at that required load.

Since the power used at this operating point is still 416 Hp, the load on the engine would be the same, in terms of power required. As noted above, the engine speed could be different, but the assumption is the engine will be capable of providing the required power regardless of its output speed, and that the power electronics of the electric-mechanical transmission are able to compensate.

The force required to move the trencher chain could increase rapidly during a time period E to where the line pull required for maintaining chain speed is equivalent to 1800 ft-lbs at the output shaft of the electric motor as is represented by point 12-5 in FIG. 10. Assuming a system efficiency of 93% and an engine input power of 416 hp, the motor would be capable of maintaining an output speed of 1128 rpm at that required load.

Since the power used at this operating point is still 416 Hp, the load on the engine would be the same, in terms of power required. As noted above, the engine speed could be different, but the assumption is the engine will be capable of providing the required power regardless of its output speed, and that the power electronics of the electric-mechanical transmission are able to compensate.

These operating characteristics illustrate an advantage that the electric driveline has, in the ability to control the torque and speed output of the motor separately from the torque applied to the engine, with a system that has a relatively consistent operating efficiency throughout the range of operating conditions. These theoretical operating characteristics illustrate how the systems may respond, in steady state operations, after the systems have adjusted to the different torque requirements for these various conditions. These operating characteristics are not intended to characterize the dynamic response of the various drive systems nor the resulting impact on the operation of the engine, to fluctuations in the load.

For comparison purposes, FIG. 11 combines the operating characteristics of the three different systems that are illustrated in FIGS. 3, 8, and 10 into a single graph. This shows that with operating characteristics at the load conditions characterized as 13-1 and 13-2, the systems all provide roughly equivalent performance. As the required load increases, however, the comparison changes. At the load conditions characterized by 13-3 and 13-4, these performance curves illustrate that a torque converter transmission could theoretically meet the load requirements, but that the speed is reduced due to reduction in the speed ratio that is inherent with a torque converter. The effect is that there is more slippage at those operating conditions which results in reduced efficiency in the power transfer, and heating-up of the torque converter. Further, the hydrostatic transmission results in a risk of overloading the engine, and of not being capable of meeting the required load.

Notably, the electric-mechanical transmission is capable adjusting to the required increasing load, while maintaining a maximum power draw, by reducing speed. The speed reduction for the electric-mechanical transmission is less than that for the torque converter transmission because the electric-mechanical system will have a consistent system efficiency.

This illustrates an advantage that the electric-mechanical transmission has, in the ability to adapt to variations in the load, to provide the capability to operate at slower speed and higher torque than is possible with either a traditional torque converter based system, or a hydrostatic system. The example illustrated in FIG. 11 demonstrates an initial operating point where the system is utilizing full power at 2037 rpm, requiring 1000 ft-lbs torque. With the hydrostatic system, if the required torque were to increase 1.5 times that, to 15000 ft-lbs, the engine is expected to stall. With a torque-converter system, the speed is expected to drop to 1190 rpm, 58% of the speed at the initial condition. This would not be a desirable operating condition as the torque converter would be generating excessive waste heat. With the electric-mechanical system, the speed is expected to drop to 1353 rpm, 66% of the speed of the initial condition.

Since there is no mechanical connection between the engine and the cutter drive systems with the electric-mechanical transmission, the engine is able to operate within its optimized operating condition. Thus, the electric-mechanical transmission is able to maintain consistent efficiency of power transfer throughout.

For the electric-mechanical transmission shown in FIG. 9, as noted earlier, there is no mechanical connection between the engine and the cutter drive system. The motor controller contains logic that affects the dynamic response characteristics of the cutter drive system. In one embodiment the motor controller logic includes a set target motor speed, and a target motor output power. Described as the operating characteristic above, as an example, the motor controller could define the target motor speed to be 2037 rpm. In the previous example of operating characteristics it was assumed that an operator selected the target speed of 2037, so that it was equivalent to the operation for the other systems. In that example a second operating parameter, the target power for the cutter drive system, was assumed to be set at 416 hp. That is not realistic, as it was assumed that the engine had a maximum power of 416 hp. In reality, some of the engine power would be required for operating the advancement drive system, and some would be required for parasitic loads such as cooling systems. Thus, FIGS. 3, 8, 10, and 11 are not intended to illustrate expected performance of an excavation machine. These graphs are only intended to illustrate how the operating characteristic of one system will compare to the others, in a simulated situation. In addition, these simulated load conditions assume that the control system is not automatically adjusting the advancement drive system.

In operation it is expected that the system will include a process where an operator will select an operating characteristic of the advancement drive system, such as the ground drive system shown in FIG. 9. The controller will generate an output, O-2, that will control the variable displacement pump to achieve a displacement that provides a desired operating characteristic of the ground drive, typically a specific propulsion force generated by the ground drive system, or a specific speed. As the excavation process proceeds, the controller is then able to automatically adjust the displacement of the hydraulic pump, by adjusting O-2, to slow-down the ground drive, or to reduce the propulsion force generated by the ground drive, when the system requires excessive power from the cutter drive system.

FIG. 12 illustrates how the system of FIG. 9 may respond when the control system automatically controls the advancement drive system. The expected system performance is depicted in this figure for two different sets of operating parameters. The expected operating curves for a first set of operating parameters, having a first power level, are depicted to start with an output speed of 2037. The output torque required starts at point 14-1, with a relatively slow increase towards the point 14-2. This increase could be the result of the advancement drive system generating an increasing force, pushing the cutting tools harder against the material being excavated. The first set of operating parameters is depicted as having another operating parameter defined as a minimum speed of 1750 rpm. As the output torque required increases from point 14-1 to 14-2, the motor controller reduces the output speed to maintain a first power, until the output speed drops to the minimum speed. At that time, the advancement drive system will be adjusted, to reduce the output torque required. In this example, once the output speed reaches a predetermined speed of, for instance, 2100 rpm, the advancement drive system is controlled to again force the cutting tools harder against the material being cut, and the output torque required will increase again. This operating curve depicts the output torque required as fluctuating between 700 ft-lbs and 1,000 ft-lbs with the first set of operating parameters including a first cutter drive system power level, and a minimum speed of 1750 rpm, and a maximum speed of 2100 rpm.

A second set of operating curves is also depicted in FIG. 12, with a set of operating parameters including a second power level, where the power level is higher than the first power level, the same minimum speed of 1750 rpm, and the same maximum speed of 2100 rpm. With this second set of operating parameters, as the output torque required increases from point 14-1 towards 14-2, the speed will slow-down at a slower rate, due to the fact that the control system is allowing the cutter drive system to draw more power. With this second set of operating parameters, the speed does not drop to 1750 until the output torque is higher than what the maximum torque was for the first set of operating parameters. At point 14-2 the advancement control system operation is affected, allowing the required torque to drop. The output speed will increase, as the motor controller adjusts to maintain a consistent power draw. With this second set of operating parameters, the system is depicted with the output torque fluctuating between 1000 ft-lbs and 1250 ft-lbs. The average output torque required with this second set of operating parameters is higher than what the average output torque required was for the first set of operating parameters.

The area under the output torque required curve is proportional to the power required by the cutter drive system. FIG. 12 is intended to illustrate that this power required by the cutter drive will be affected by the operating parameters set for the control system, by comparing the output torque required curve for the first power level to the output torque required curve for the second power level.

The engine depicted in the system illustrated in FIG. 9 includes an ECU, the Engine Control Unit. The ECU generates data to calculate the average power load on the engine, based on various operating parameters such as average fuel flow, and air flow. This calculated data can be used in a new way to control the excavation machine. One way to optimize the productivity of the machine is to operate it in a manner to automatically adjust the operating parameters so that the machine is operated in a manner that the average engine power is as close as possible to 100%. The average engine power will react slower than the instantaneous power drawn by the excavation motor, thus there is an opportunity to use both the instantaneous power drawn by the excavation motor and the average engine power, in a control algorithm to automatically optimize the excavation machine's performance.

FIG. 13 illustrates an embodiment of a control algorithm designed to provide this function: starting at an initial operating point 13-1 where an operator has started an excavation process by selecting an operating speed of the cutter drive system, and an initial set of operating parameters has been defined. The operating speed of the cutter drive system will be affected by the type of cutting tools installed on the active cutting system, and the type of material being excavated. The operator will then initiate excavation by activating the advancement system with an initial operating parameter. As an example, the initial operating parameter of the advancement system for a chain trencher, such as is illustrated in FIG. 9, could be a propel pressure of the ground drive system. This parameter would be the pressure generated by the variable displacement hydraulic pump(s), that is applied to the fixed displacement hydraulic motor(s), to generate a propel force pushing the trencher boom and chain into engagement with the material being excavated, with a set, controlled, force. This parameter is controlled by the Output O-2 that is sent from the controller to the variable displacement hydraulic pump.

A set of operating parameters for the cutter drive system could include a first power level as was described in the explanation of the first power level in reference to FIG. 12.

The control process of 13-2 illustrates the control of the advancement system that results in the required torque fluctuating between a maximum and a minimum level, through several cycles. This is intended to illustrate the traditional or typical, control for a chain trencher. In some prior art this control referenced the engine speed, and/or the output speed of a torque converter. For the system described FIG. 9, with an electric-mechanical transmission, there is no definite correlation between the engine speed and the speed of the motor. With a permanent magnet synchronous motor and the power electronics of the electric-mechanical transmission, the control system illustrated in FIG. 9 is shown with a sensor that measures the speed of the motor as Input-2, I-2. At the step 13-2, whenever this speed drops below a predetermined speed, the control system will automatically restrict the advancement system. Adjustments to the advancement system may occur in thousandths of seconds, in other words the advancement system could be adjusted hundreds of times each second. The system may operate in this mode for a period of time, for instance one second, or two or more seconds.

The control process further includes the step 13-3 at which the control system will monitor the power level data, which is data generated by the ECU, during this period of time, and that is included in the data stream labelled I-1. The controller monitors Input signal, I-1, which contains the engine power data which is calculated by the ECU, based on the fuel and air systems, and is communicated as part of an industry-standard CAN message. The controller monitors this power level over a period of time, which could be over a period of time comprising one second, or up to a period of time comprising ten seconds. The specific period of time is not important, however it is longer than the periods during which the control system automatically restricts the advancement system.

At the control process of 13-4 the controller will consider the average power level data, and if the average power level is less than a desired threshold, for instance less than 95%, then the system will move to process 13-4b. At this step the control system will change the operating parameter in a way expected to cause an increase in the average power drawn. For example, that could be to adjust the power level to the second power level depicted in FIG. 14, where the power drawn by the cutter drive system is increased to a second, higher, power level which is expected to result in an increase in the power drawn from the engine.

After control process 13-4b changes this operating parameter, the process would revert back to step 13-2 where the machine would be operated for a period of time during which the average power level is again determined.

If at step 13-4a the average power is not less than 95%, the system advances to step 13-4c. If the power level is more than, for example, 100% at this step, then it advances to step 13-4d during which the system automatically adjusts the system's operating parameters in a way to decrease the average engine power.

Step 13-2 describes the process where-in the system automatically restricts the advancement system in response to a measurement of the operation of the cutter drive system. The advancement system may be restricted if the operating speed of the cutter system drops below the initial operating speed, or below some percentage of the initial operating speed. The advancement system is shown as a hydraulically actuated system in the systems for FIGS. 2, 7, and 9.

However, the advancement system could be actuated by a separate electric-mechanical system as shown in FIG. 14 which illustrates an alternative embodiment of the system as shown in FIG. 9, wherein the advancement system is comprised of a ground drive with an electric-mechanical transmission. This system could be operated/controlled in ways that are very similar to those described for the system of FIG. 9, except that the Output 2, O-2 signal, would be configured to control the power electronics of the advancement drive system's electric-mechanical transmission. Further, FIG. 14 shows a separate generator as providing power to a motor controller/inverter for the ground drive. This generator is shown in dashed lines, which are intended to indicate that this could be a separate generator, or this electric power could be drawn from the same generator that is shown connected to the motor controller/inverter for the cutter drive system.

In some embodiments, the cutter system (e.g., the speed of the chain) responds more rapidly than the advancement system (e.g., the speed of the tracks propelling the machine), such that draw down transients will occur as the machine changes speeds for the advancement system. Also, the cutter system speed may be adjusted manually. The speed that the VFD can react at relative to a swash plate of a hydraulic system is the reason for this. There may be several transients in the cutter system, and the VFD can react more quickly to the transients than a hydraulic system.

Further, in some embodiments, there is an averaging filter between the reaction of the advancement system and the slowdown of the cutter system. As the chain slows down, it decreases the average advancement system speed that is applied, but the chain can react more quickly than the advancement system. This feedback loop generally stabilizes when the tracks reach an average speed that is fairly close to the commanded change speed, with some offset (e.g., commanding the chain speed to 35 rpm may result in operation at an average of 32 rpm.

When cutting into a homogeneous material, relatively little slowdown may occur. The drawn down transients generally occur more often when transitions between materials cause the machine to adapt quickly. As noted above, the VFD allows the chain speed to react quicker than the track speed, which may result in a rapid draw down of the chain as the chain encounters a new material and finds a new speed to approach the commanded chain speed. In this situation, the commanded track speed may be at a standstill. To get the tracks moving again, the chain speed may be lowered to cause the tracks to push more aggressively and maintain power on the chain.

The control algorithm shown in FIG. 13 has been described as applied to control an electric-mechanical drive. That control algorithm can also be applied to an alternative system as shown in FIG. 15, with the cutter drive having a variable torque converter. A variable torque converter could be one where the pitch of a stator, or the performance of a bypass clutch can be controlled. Torque converters of this type are described in U.S. Pat. Nos. 9,689,492 and 10,118,624 which are hereby incorporated by reference. This system can be operated in a similar way, as described in reference to FIG. 13, where an operating parameter of the torque converter is automatically adjusted. With this system, a sensor could measure the output speed of the torque converter at Input 2, I-2. The controller would use that signal to control the ground drive system. The ECU will communicate with the controller through the Input-1, I-1. This will include information regarding the engine power. The operating parameter of the torque converter will be controlled by Output 1, O-1. In the embodiment of FIG. 15, engine power (as calculated by the ECU) may be used as a variable to automatically change an operating parameter of the torque converter to improve performance of the engine.

FIG. 16 is a flow diagram of an example method for operating an excavation machine, that may be implemented in combination with the other embodiments described herein.

Mechanical Arrangements

FIG. B1 is a perspective view of an example excavation machine B100 (here, a chain trencher) that may incorporate at least some of the embodiments described herein. FIG. B2 is a side view of the excavation machine B100 shown in FIG. B1 with the boom B102 in a raised position, and FIG. B3 is a side view of the excavation machine B100 shown in FIG. B1 with the boom B102 in a lowered position. FIG. B4 is a cross-sectional view of the excavation machine B100 taken along line B4-B4 (shown in FIG. B2).

The mechanical arrangement between a gearbox and a head shaft in the excavation machine shown in FIGS. B1-B4 will now be described.

FIG. B7 is a simplified diagram of one embodiment of a mechanical arrangement B200 for a chain trencher according to the present disclosure. FIG. B8 is an enlarged view of a portion of the mechanical arrangement B200 shown in FIG. B7.

As shown in FIGS. B7 and B8, the mechanical arrangement B200 includes a head shaft B202 driven by a rotational drive unit B204. The rotating head shaft B202 drives a digging chain around a boom B206 (such as boom B102). In the mechanical arrangement B200, the rotational drive unit B204 includes a motor B208 and a gearbox B210. The motor B208 may be any type of motor suitable for driving the head shaft B202 via the gearbox B210. For example, in some embodiments, the motor B208 may be an electric motor. In other embodiments, the motor B208 may be a hydraulic motor.

In the mechanical arrangement B200, the head shaft B202 is mounted to a main frame B212 via first bearings B214. Notably, in contrast to the mechanical arrangement B10 (shown in FIG. B5), the gearbox B210 is not directly coupled to the main frame B212. Further, the gearbox B210 does not support the head shaft B202. Instead, in the embodiment of FIGS. B7 and B8, the head shaft B202 supports the gearbox B210. That is, the output of the gearbox B210 is a hollow shaft (i.e., a tube) that is mounted to the head shaft B202 with seals and a splined connection. Further, the head shaft B202 supports the gearbox B210 via second bearings B216. A torque arm B218 holds the gearbox B210 in place and prevents counter rotation of the gearbox B210 relative to the main frame B212.

FIG. B9 is an alternative embodiment of a mechanical arrangement B300 for a chain trencher.

The mechanical arrangement B300 includes a head shaft B302 driven by a first rotational drive unit B304 and a second rotational drive unit B305. The rotating head shaft B302 drives a digging chain around a boom B306 (such as boom B102). The first and second rotational drive units B304 and B306 are located on opposite sides of the boom B306. In the mechanical arrangement B300, the first rotational drive unit B304 includes a first motor B308 and a first gearbox B310, and the second rotational drive unit B305 includes a second motor B309 and a second gearbox B310.

The first and second motors B308 and B309 may each be any type of motor suitable for driving the head shaft B302 via the first and second gearboxes B310 and B311. For example, in some embodiments, at least one of the first and second motors B308 and B309 may be an electric motor. In other embodiments, at least one of the first and second motors B308 and B309 may be a hydraulic motor.

In the mechanical arrangement B300, the head shaft B302 is mounted to a main frame B312 via first bearings B314. Similar to the mechanical arrangement B200 (shown in FIGS. B7 and B8), the head shaft B302 supports the first and second gearboxes B310 and B311. That is, the output of each of the first and second gearboxes B310 and B311 is a hollow shaft (i.e., a tube) that is mounted to the head shaft B202 with seals and a splined connection. Further, the head shaft B302 supports the first gearbox B310 via second bearings B316, and supports the second gearbox B311 via third bearings B317. A first torque arm B318 holds the first gearbox B310 in place and prevents counter rotation of the first gearbox B310 relative to the main frame B312. Similarly, a second torque arm B319 holds the second gearbox B311 in place and prevents counter rotation of the second gearbox B311 relative to the main frame B312.

FIG. B10 is a simplified diagram of one embodiment of a mechanical arrangement B400 for a surface miner according to the present disclosure.

As shown in FIG. B10, the mechanical arrangement B400 includes a head shaft B402 driven by a rotational drive unit B404. The head shaft B402 is coupled to a drum B406 such that driving rotation of the head shaft B402 causes the drum B406 to rotate as well. The head shaft B402 and the drum B406 rotate about a longitudinal axis B408.

In the mechanical arrangement B400, the rotational drive unit B404 includes a motor B410 and a gearbox B412. The motor B410 may be any type of motor suitable for driving the head shaft B402 via the gearbox B412. For example, in some embodiments, the motor B410 may be an electric motor. In other embodiments, the motor B410 may be a hydraulic motor. As shown in FIG. B10, the motor B410 is located outside of the drum B406. Further, the motor B410 is offset from the longitudinal axis B408 (i.e., the motor is not coaxial with the longitudinal axis B408). The offset location of the motor B410 facilitates easier access to the motor B410 (e.g., for replacement or repair operations), and also facilitates improving cooling of the motor B410 (as the motor B410 is external to the drum B406 and spaced apart from the material being cut by the drum B406).

In the mechanical arrangement B400, the head shaft B402 is mounted to a main frame B414 via bearings B416 that enable the head shaft B402 and the drum B406 to rotate relative to the main frame B414. A torque arm B418 holds the gearbox B412 in place and prevents counter rotation of the gearbox B412 relative to the main frame B414.

The embodiment of FIG. B10 includes a single motor B410. However, in accordance with the present disclosure, in other embodiments, mechanical arrangements may include multiple motors. Further, motors may be located on the same side of the drum, or on opposite sides of the drum.

For example, FIG. B11 is a perspective view of a surface miner B500 including an alternative mechanical arrangement B502. The mechanical arrangement B502 includes a gearbox B506 configured for use with one or more motors B504. Specifically, the mechanical arrangement B502 includes two motors B504. By using multiple motors B504 instead of a single motor, for a given total power, each motor B504 can provide a fraction of the total power, instead of requiring a single motor to supply the total power. Further, using multiple motors B504 provides redundancy (e.g., in the event one motor B504 fails, the other motor B504 can continue to drive rotation of a drum B508 via the gearbox B506). As in the mechanical arrangement B400 (shown in FIG. B11), in this embodiment, both motors B504 are offset from a longitudinal axis B510 of the drum B508. Further, in this embodiment, the mechanical arrangement B502 forms at least a portion of a boom that can be selectively raised and lowered with respect to the remainder of the surface miner B500.

FIG. B12 is a side view of the surface miner B500 shown in FIG. B11. FIG. B13 is a top view of the surface miner B500 shown in FIG. B11. FIG. B14 is a front perspective view of the mechanical arrangement B502, and FIG. B15 is a rear perspective view of the mechanical arrangement B502.

Although not shown, in some embodiments, a mechanical arrangement for a surface miner may include two gearboxes located on opposite sides of the drum. Each gearbox may by drive by one or more motors. For example, a mechanical arrangement similar to that shown in FIG. B9 (for a chain trencher) could be implemented for a surface miner.

Further, in the excavation machines described herein, it may be desirable to isolate the motor from the associated gearbox to avoid the motor experiencing vibrations and/or oscillations generated or experienced by the gearbox and/or cutting tool.

For example, FIG. B16 is a simplified schematic diagram of an alternative mechanical arrangement B600 for a surface miner. The mechanical arrangement B600 is somewhat similar to the mechanical arrangement B400 (shown in FIG. B10). However, in this mechanical arrangement B600, a motor B602 is not directly coupled to a gearbox B604. Instead, the motor B602 is coupled to the gearbox B604 through a flexible coupling B606, such as a cardan shaft. Using the flexible coupling B606 enables the motor B602 to move relative to the gearbox 604. Accordingly, vibrations and/or oscillations experienced by the gearbox B604 are not imparted onto the motor B602. Further, the motor B602 may be mounted to one or more isolators (not shown) to further dampen any vibrations and/or oscillations.

As another example, FIG. B17 shows a simplified schematic diagram of an alternative mechanical arrangement B700 for a chain trencher. The mechanical arrangement B700 is somewhat similar to the mechanical arrangement B200 (shown in FIG. B7). However, in this mechanical arrangement B700, a motor B702 is not directly coupled to a gearbox B704. Instead, the motor B702 is coupled to the gearbox B704 through a flexible coupling B706, such as a cardan shaft. Using the flexible coupling B706 enables the motor B702 to move relative to the gearbox B704. Accordingly, vibrations and/or oscillations experienced by the gearbox B704 are not imparted onto the motor B702. In this embodiment, the motor B702 is mounted to a main frame B708 of the chain trencher, and may be mounted via one or more isolators (not shown) to further dampen any vibrations and/or oscillations.

Isolation Systems

FIG. C1 is a perspective view of an example surface miner C100 that may incorporate at least some of the embodiments described herein. Alternatively, the systems and methods described herein may be incorporated in other excavation machines (e.g., a chain trencher).

A mechanical arrangement C102 for the surface miner C100 includes two motors C104 coupled to a gearbox C106. Motors C104 drive rotation of a drum C108 of the surface miner C100 to dig or cut into a material (e.g., earth).

FIG. C2 is a side view of the surface miner C100 shown in FIG. C1. FIG. C3 is a top view of the surface miner C100 shown in FIG. C1. FIG. C4 is a cross-sectional view of the surface miner C100 taken along line C4-C4 shown in FIG. C3.

FIG. C5 is a simplified schematic diagram of an engine generator mount C200 that may be used with the surface miner C100 (shown in FIG. C1). FIG. C6 is a perspective view of the engine generator mount C200. FIG. C7 is an alternative simplified schematic diagram of the engine generator mount C200.

The engine generator mount C200 includes a generator C202 and an engine C204 mounted to a frame C206 of an excavation machine (e.g., a surface miner or chain trencher). To reduce vibrations and/or oscillations that would otherwise be experienced by the generator C202, the generator C202 is mounted to the frame C206 via one or more first isolators C208. In this embodiment, at least some of the first isolators C208 are generally oriented at a 45° angle relative to a longitudinal axis C210 of the generator C202. Alternatively, the first isolators 208 may have any suitable configuration. Further, the engine C204 may also be mounted to the frame C206 via one or more second isolators C212. In addition, in this embodiment, the generator C202 is coupled to the engine C204 through a flexible coupling C214, such as a cardan shaft. Using the flexible coupling C214 enables the generator C202 to move relative to the engine C204 (e.g., when experiencing forces from vibration and/or oscillations).

The systems and methods described herein include a mechanical arrangement for an electric drive for a chain trencher, the mechanical arrangement including a generator powered by a diesel engine, an electric motor (e.g., a permanent magnet asynchronous motor connected to, or mounted to, a gear box that is mounted to the head shaft of a trencher, with a torque arm that holds the gearbox from rotating about the head shaft axis), and a control system that controls the electrical power (e.g., current and voltage) generated by the generator to control the operating characteristics of the motor.

The systems and methods described herein also include a control system for an excavation machine having a cutter drive system including a “torque converter” as a drive system that does not have a direct mechanical connection between an input and an output, and that permits slip between the input and the output wherein the torque at the output can increase during periods of slip. The control system automatically controls the speed of a ground drive system and automatically controls the slip characteristics of the torque converter based on feedback signals including the engine power as calculated by an electronic control unit. The “torque converter” may include an electric-mechanical transmission. Alternatively, the “torque converter” may be a hydrodynamic torque converter.

The systems and methods described herein also include a flexible configuration for a trencher, for providing either an electric drive or a hydraulic drive.

In the present disclosure, an excavation machine with an electric motor and a control system is provided. The control system includes an algorithm that controls power applied to maintain a constant maximum power by automatically controlling the speed and torque. This allows the excavation machine to slow down by more than 30%, in order to apply an increasing force to the material that is being excavated, as the required force increases, while maintaining a consistent power draw. This is unique to an electric-mechanical device, and wouldn't be possible with a mechanical (e.g., hydrostatic or torque converter) system.

With a hydrostatic system, the torque increases as the speed increases, but only up to a point. Typical engine operating curves have max power from about 2000 to 2400 rpm, with a max torque occurring at around 1600 to 1800 rpm. Thus, once the engine rpm drops below 2000 rpm, the power generated by the engine decreases. With a torque converter system, as the torque increases, the slip also increases. The power transferred to the excavation device will decrease, as the torque increase is possible by operation with reduced efficiency that is inherent to a torque converter. Using an electric-mechanical drive, as described herein, provides advantages over both of these approaches.

In the present disclosure, an excavation machine is provided. The excavation machine includes an excavation device having cutting tools mounted thereon (e.g., a trencher has cutting teeth mounted to a trenching chain that is mounted to a trencher boom with the chain routed around a drive sprocket and an end-idler sprocket, a terrain leveler has cutting teeth mounted to drum, etc.). The excavation machine further includes an excavation device drive system that powers the excavation device to move the cutting tools through a cutter travel path (e.g., for a trencher the excavation device drive system is the head shaft to which a pair of drive sprockets are mounted, where the sprockets engage with the trencher chain to propel the chain around the trencher boom. As another example, a direct drive terrain leveler has a motor directly connected to the drum, or a chain-driven terrain leveler has a pair of drums that are mounted in-line with the end-idler of a trencher boom-note: this travel path is different than the movement that will be caused by a separate drive to move the entire boom, or to move the entire machine). The excavation device drive system includes an electric motor and motor control wherein a control system includes a control algorithm configured to control the speed of the excavation device drive system to a predetermined first excavation speed when the power drawn for that system is below a predetermined target power, or to automatically reduce the speed of, and increase the torque generated by, the electric motor, in order to maintain the predetermined target power, when the force required to propel the cutting tools exceeds the force that the excavation device drive system can generate with the excavation device drive system operating at the first excavation speed at the predetermined target power.

In one embodiment, the excavation machine further includes an internal combustion engine that powers a generator, wherein the generator provides power to the electric motor powering the excavation device drive system and the control system configured to manage the power draw created by the generator so that the engine will operate in an optimum operating condition (such as by allowing the engine to operate between 1900 and 2100 rpm) while the speed and torque generated by the electric motor powering the excavation device drive system varies independently to provide the force required to propel the cutting tools.

In one embodiment, the control system automatically adjusts the target power applied to excavation device drive system as a function of an engine power data stream generated by an engine controller.

In one embodiment, the excavation machine further includes an advancement system for moving the excavation device wherein the control system further includes an algorithm that automatically controls the advancement system: i) as a function of the excavation system speed (e.g., if the excavation speed drops below a predetermined percentage of the predetermined first excavation speed, the advancement system will slow down or reduce the force propelling the cutting system); or ii) as a function of the torque generated by the electric motor (e.g., if the torque exceeds a predetermined percentage of the maximum torque that was required to generate the predetermined target power at the predetermined first excavation speed, the advancement system will slow down or reduce the force propelling the cutting system).

In one embodiment, the advancement system will slow down or reduce the force propelling the cutting system only after i) the excavation system speed is equal to or less than 0.7 times the predetermined first excavation speed; or ii) the torque generated by the electric motor is equal to more than 1.4 times the motor.

In the present disclosure, an excavation machine including a diesel engine, a cutting system drive, and an associate control system is provided. The excavation machine includes an advancement system, and a power transmission device that is may include at least one of i) a torque converter that transfers power from an engine to an active cutting system drive, the torque converter being a system without a direct mechanical link, that permits slip between the input connected to the engine and the output connected to the active cutting system, wherein the torque increases with an increase in slip, with variable slip characteristics, a variable torque and speed characteristic; and ii) an electric-mechanical transmission comprising a generator, motor and power electronics where the power electronics can control the variable torque and speed characteristic. The control system uses engine load calculated by the engine as a control parameter to control the torque and speed characteristic of the power transmission device and that uses the output speed of the power transmission device to control the advancement system.

In the present disclosure, an excavation machine is provided. The excavation machine includes a diesel engine having an engine control unit (ECU) that controls and monitors a fuel system and an air intake system to provide diesel fuel and combustion air to the engine, the ECM calculates an engine load parameter at least partially based on the fuel and air flow, and an active cutting system. The excavation machine further includes a power transmission device that transfers power from the diesel engine to the active cutting system at a variable operating speed having an operating parameter that affects a variable torque and speed characteristic of the power transmission device (e.g., a system without a direct mechanical link, that permits slip between the input connected to the engine and the output connected to the active cutting system, wherein the torque increases with an increase in slip). The excavation machine further includes an advancement system that propels the active cutting system during excavation, and a control system that controls the advancement system based on the operating speed of the power transmission device, and that controls the operating parameter of the power transmission device based on the engine load parameter. The advancement system may be controlled at a first frequency on the order of thousandths of a second, for example, and the operating parameter may be controlled at a second frequency on the order of tenths of seconds, for example.

In one embodiment, the power transmission device is an electric-mechanical transmission having a generator physically coupled to the engine, a motor physically coupled to the active cutting system, and power electronics electrically coupling the generator with the motor. Further, the control system may control a target power that is defined as an operating parameter of the power electronics, increasing the target power when the engine load parameter is below a predefined target, and reducing the target power when the engine load parameter is above a predefined target.

In one embodiment, the power transmission device is a torque converter type transmission having an adjustable operating parameter. Further, the control system may control one of the pitch of a stator and a bypass clutch to increase or decrease load on the engine.

The embodiments described herein involve the use of one or more electronic or computing devices. Such devices typically include a processor, processing device, or controller, such as a general purpose central processing unit (CPU), a graphics processing unit (GPU), a microcontroller, a reduced instruction set computer (RISC) processor, an application specific integrated circuit (ASIC), a programmable logic circuit (PLC), a field programmable gate array (FPGA), a digital signal processing (DSP) device, and/or any other circuit or processing device capable of executing the functions described herein. The methods described herein may be encoded as executable instructions embodied in a computer readable medium, including, without limitation, a storage device and/or a memory device. Such instructions, when executed by a processing device, cause the processing device to perform at least a portion of the methods described herein. The above examples are not intended to limit in any way the definition and/or meaning of the term processor and processing device.

As used herein, the terms “about,” “substantially,” “essentially” and “approximately” when used in conjunction with ranges of dimensions, concentrations, temperatures or other physical or chemical properties or characteristics is meant to cover variations that may exist in the upper and/or lower limits of the ranges of the properties or characteristics, including, for example, variations resulting from rounding, measurement methodology or other statistical variation.

When introducing elements of the present disclosure or the embodiment(s) thereof, the articles “a”, “an”, “the” and “said” are intended to mean that there are one or more of the elements. The terms “comprising,” “including,” “containing” and “having” are intended to be inclusive and mean that there may be additional elements other than the listed elements. The use of terms indicating a particular orientation (e.g., “top”, “bottom”, “side”, etc.) is for convenience of description and does not require any particular orientation of the item described.

As various changes could be made in the above constructions and methods without departing from the scope of the disclosure, it is intended that all matter contained in the above description and shown in the accompanying drawing[s] shall be interpreted as illustrative and not in a limiting sense.

Claims

1. An excavation machine comprising: an excavation device having a plurality of cutting tools mounted thereon; andan excavation device drive system that powers the excavation device to move at least one of the plurality of cutting tools through a cutter travel path, wherein the excavation device drive system comprises an electric motor and a motor controller, the electric motor being powered by a power supply,wherein the motor controller is programmed to control a speed of the excavation device drive system via a control algorithm, wherein, the control algorithm, when executed by the motor controller, causes the motor controller to set the speed of the excavation device drive system at a predetermined excavation speed based on a predetermined target power, the predetermined target power being associated with a target torque generated by the electric motor, andwherein the speed of the excavation device drive system is set at a predetermined first excavation speed when a power transmitted to the electric motor is below the predetermined target power, and wherein the speed of the excavation device drive system is set at a predetermined second excavation speed to maintain the power transmitted to the electric motor at the predetermined target power, the predetermined second excavation speed being less than the predetermined first excavation speed and being associated with an increase in the target torque generated by the electric motor, the speed of the excavation device drive system being set at the predetermined second excavation speed when a first force required to propel at least one of the plurality of cutting tools exceeds a second force that the excavation device drive system can generate with the excavation device drive system operating at the predetermined first excavation speed at the predetermined target power.

2. The excavation machine of claim 1, wherein the power supply includes at least one of an energy storage device, an energized power line, and an engine.

3. The excavation machine of claim 1, wherein the power supply includes an internal combustion engine that powers a generator, wherein the generator provides power to the electric motor powering the excavation device drive system and the motor controller is configured to manage the power transmitted to the electric motor to operate the internal combustion engine at an optimum operating condition, the optimum operating condition including varying values of the speed and the torque generated by the electric motor powering the excavation device drive system, wherein the varying values of the speed and the target torque vary independently to provide the first force required to propel at least one of the plurality of cutting tools.

4. The excavation machine of claim 3, wherein the motor controller automatically adjusts the predetermined target power applied to the excavation device drive system as a function of an engine power data stream generated by an engine controller.

5. The excavation machine of claim 1, further comprising an advancement system for moving the excavation device, wherein the motor controller is further programmed to automatically control the advancement system via a second control algorithm, wherein, the second control algorithm, when executed by the motor controller, causes the motor controller to control the advancement system as a function of at least one of the speed and the torque generated by the electric motor.

6. The excavation machine of claim 5, wherein the motor controller will reduce an advancement system speed or reduce the first force propelling at least one of the plurality of cutting tools when at least one of the speed is equal to or less than 0.7 times the predetermined first excavation speed and the torque is equal to more than 1.4 times the target torque.

7. An excavation machine comprising: a diesel engine having an engine control unit (ECU) that controls and monitors a fuel system and an air intake system that provides diesel fuel and combustion air to the diesel engine, wherein the ECU calculates an engine load parameter at least partially based on a fuel amount and a flow of air;an active cutting system;a power transmission device that transfers power from the diesel engine to the active cutting system at a variable operating speed, wherein the variable operating speed is based on an operating parameter that affects a variable torque and a speed characteristic of the power transmission device; andan advancement system that propels the active cutting system during excavation; anda control system that controls the advancement system based on the variable operating speed of the power transmission device, and wherein the control system controls the operating parameter of the power transmission device based on the engine load parameter.

8. The excavation machine of claim 7, wherein the power transmission device is an electric-mechanical transmission having a generator physically coupled to the diesel engine, a motor physically coupled to the active cutting system, and power electronics electrically coupling the generator with the motor.

9. The excavation machine of claim 8, wherein the control system controls a target power of the power electronics based on a predefined target of the engine load parameter, the target power being increased when the engine load parameter is below the predefined target and the target power being decreased when the engine load parameter is above the predefined target.

10. The excavation machine of claim 7, wherein the power transmission device is a torque converter type transmission having an adjustable operating parameter.

11. The excavation machine of claim 10, wherein the control system controls at least one of a pitch of a stator and a bypass clutch as the operating parameter of the power transmission device.

12. A mechanical arrangement for an excavation machine, the mechanical arrangement comprising: a cutting tool;a head shaft coupled to the cutting tool and defining a longitudinal axis;a gearbox coupled to the head shaft such that the head shaft supports the gearbox; anda motor coupled to the gearbox, wherein the motor is offset from the longitudinal axis of the head shaft, and wherein the motor is configured to drive rotation of the head shaft and the cutting tool via the gearbox.

13. The mechanical arrangement of claim 12, wherein the motor is an electric motor.

14. The mechanical arrangement of claim 12, wherein the motor is a hydraulic motor.

15. The mechanical arrangement of claim 12, wherein the cutting tool is a chain of a chain trencher.

16. The mechanical arrangement of claim 12, wherein the cutting tool is a drum of a surface miner.

17. The mechanical arrangement of claim 12, wherein the motor is coupled to the gearbox using a flexible coupling.

18. The mechanical arrangement of claim 12, wherein the motor is mounted to a frame of the excavation machine via at least one isolator.

19. A mechanical arrangement for an excavation machine, the mechanical arrangement comprising: a cutting tool;a head shaft coupled to the cutting tool;at least one gearbox coupled to the head shaft such that the head shaft supports the gearbox; anda plurality of motors, wherein the plurality of motors are configured to drive rotation of the head shaft and the cutting tool, and wherein at least one of the plurality of motors is coupled to the at least one gearbox.

20. The mechanical arrangement of claim 19, wherein the at least one gearbox comprises a single gearbox, and wherein the plurality of motors comprises a first motor and a second motor, each of the first motor and the second motor being coupled to the single gearbox.

21. The mechanical arrangement of claim 19, wherein the at least one gearbox comprises a first gearbox and a second gearbox, the first and second gearboxes being located on opposite sides of the cutting tool, and wherein the plurality of motors comprises a first motor coupled to the first gearbox and a second motor coupled to the second gearbox.

22. The mechanical arrangement of claim 19, wherein at least one of the plurality of motors is an electric motor.

23. The mechanical arrangement of claim 19, wherein at least one of the plurality of motors is a hydraulic motor.

24. The mechanical arrangement of claim 19, wherein the cutting tool is a chain of a chain trencher.

25. The mechanical arrangement of claim 19, wherein the cutting tool is a drum of a surface miner.

26. The mechanical arrangement of claim 19, wherein at least one of the plurality of motors is coupled to the at least one gearbox using a flexible coupling.

27. The mechanical arrangement of claim 19, wherein at least one of the plurality of motors is mounted to a frame of the excavation machine via at least one isolator.

28. The mechanical arrangement of claim 19, wherein at least one of the plurality of motors is offset from a longitudinal axis of the head shaft.