Patent Application
20090037072
The present disclosure relates generally to a machine system and, more particularly, to control of a machine system power source based on classified tasks of the machine system's work implement.
Mobile machines, including wheel loaders, bulldozers, motor graders, and other types of heavy equipment, are used for a variety of operations. In order to accomplish these operations, the machines typically include a primary mover, such as an internal combustion engine. The primary mover is often coupled to traction devices to propel the machine and can also power a work implement attached to the machine.
Machines often have a “high-idle” mode of operation. During use of the high-idle mode of operation, an output of the primary mover is generally set to a level sufficient to quickly produce the maximum output to the traction devices and/or work implement. In other words, to ensure that the machine has power sufficient to move the machine and/or work implement under all conditions, the primary mover output (i.e., speed, torque, or a combination of speed and torque) is set at a high level, even if the current operation being performed by the machine demands less than the high output level. Although setting the primary mover output to a high level allows for immediately available power, it may be inefficient and result in excessive fuel consumption, exhaust emissions, and engine noise.
One way to control the output of a primary mover is disclosed in U.S. Pat. No. 4,697,418 (the '418 patent) issued to Okabe et al. on Oct. 06, 1987. The '418 patent relates to a control system for a hydraulic excavator. The excavator has a prime mover, a variable displacement hydraulic pump driven by the prime mover, at least one actuator driven by pressurized fluid from the pump, devices for sensing the operation condition of the actuators, and working elements associated with the actuators. The devices for sensing the operation condition of the actuators include a pressure switch for sensing whether travel motors are in operation and a pressure switch for sensing whether a boom cylinder, an arm cylinder, or a bucket cylinder for driving a front attachment and a swing motor for rotating a swing are in operation. The excavator also has a selection means for selecting an operation mode for each working element. The selection means includes a power mode (P-mode) suitable for heavy digging operations and an economy mode (E-mode) suitable for light digging operations.
Based on the output signals from the sensors and the selection means, the controller selects a combination of a prime mover maximum revolution number and a pump maximum displacement volume (e.g., the controller may select different prime mover and pump settings if digging in power mode versus digging in economy mode). The control means then sets the maximum revolution number of the prime mover and the maximum displacement volume of the hydraulic pump. Setting the prime mover maximum revolution number and pump maximum displacement volume according to the selection means and the operation condition of the actuators may help reduce fuel consumption and noise.
Although the construction machine of the '418 patent may improve fuel efficiency and noise by setting the prime mover maximum revolution number and the pump maximum displacement volume according to the selection means and the operation condition of the actuators, it may still be suboptimal. The control system of the '418 patent may only detect whether the actuators are in operation (i.e., on or off) rather than detecting what the actuators are accomplishing while in operation (i.e., raising the bucket, dumping material, digging, etc.). In other words, the control system of the '418 patent may respond to any operation that activates the pressure switch associated with the front attachments by setting the prime mover maximum revolution number and the pump maximum displacement volume at a level that may be either too high or too low for the actual task being performed. Furthermore, the control system of the '418 patent only controls the operation of the prime mover by setting the maximum revolution number, which may limit the ground speed and thus the productivity of the machine for certain tasks.
The disclosed machine system is directed to overcoming one or more of the problems set forth above.
In one aspect, the present disclosure is directed to a machine control system. The control system may include a power source, an operator input device configured to generate a first signal indicative of a desired mode of power source operation, and a work implement driven by the power source. The control system may also include a controller in communication with the power source and the operator input device. The controller may be configured to classify a currently performed work implement task and select an output map based on the classification of the currently performed work implement task and the first signal. The controller may further be configured to control the power source operation using the output map.
In another aspect, the present disclosure is directed to a method of operating a machine. The method may include receiving a user input indicative of a desired mode of power output generation, generating a power output, and directing the power output to actuate a work implement. The method may also include classifying a currently performed work implement task and selecting an output relationship based on the currently performed work implement task and the desired mode of power output generation. The method may further include adjusting the power output generation using the output relationship.
As shown in
Transmission 16 may transmit power from power source 12 to traction device 14. In particular, transmission 16 may embody a multi-speed, bidirectional, mechanical transmission a plurality of forward gear ratios, one or more reverse gear ratios, and one or more clutches (not shown). Transmission 16 may selectively actuate the clutches to engage predetermined combinations of gears (not shown) that produce a desired output gear ratio. Transmission 16 may be an automatic-type transmission, wherein shifting is based on a power source speed, a maximum operator selected gear ratio, and a shift map stored within a controller. Alternatively, transmission 16 may be a manual transmission, wherein the engaged gear is manually selected by an operator. Transmission 16 may connect to power source 12 by way of torque converter 18. An output of transmission 16 may rotatably drive traction device 14 via shaft 23, thereby propelling machine 10.
Referring again to
Work implement 32 may include any device used to perform a particular task, such as a bucket, a blade, a shovel, a ripper, or any other task-performing device known in the art. One or more work implements 32 may be attachable to a single machine 10 and controllable via operator station 20. Work implement 32 may be connected to machine 10 via a direct pivot, via a linkage system, via one or more hydraulic cylinders, via a motor, or in any other appropriate manner. Work implement 32 may pivot, rotate, slide, swing, lift, or move relative to machine 10 in any manner known in the art.
As further shown in
The axial displacement of hydraulic cylinder 24 may be effected by creating an imbalance of force on a piston assembly 25 disposed within a tube 27 of each hydraulic cylinder 24. Specifically, each hydraulic cylinder 24 may include a first chamber and a second chamber separated by piston assembly 25. Piston assembly 25 may include two opposing hydraulic surfaces, one associated with each of the first and second chambers. The first and second chambers may be selectively supplied with a pressurized fluid and drained of the pressurized fluid to create an imbalance of force on the two surfaces. The imbalance of force may cause piston assembly 25 to axially displace within tube 27.
Hydraulic cylinder 24 may be used to provide an actuating force for various components of machine 10, such as, for example, work implement 32. Work implement 32 may be connected to a frame of machine 10 via a direct pivot or a linkage system, with hydraulic cylinder 24 being a member of the pivot or linkage system. As hydraulic cylinder 24 axially displaces, the pivot or linkage system may translate or rotate, thus enabling the operator to perform a desired task with work implement 32. It is contemplated that several hydraulic cylinders 24 may be used in the pivot or linkage system to create additional degrees of freedom in the movement of work implement 32.
Pump 28 may produce a flow of pressurized fluid for use in machine 10. Pump 28 may embody a variable displacement pump, a fixed displacement pump, a variable flow pump, or any other source of pressurized fluid known in the art. Pump 28 may be drivably connected to power source 12 by, for example, a countershaft 36, a belt (not shown), an electric circuit (not shown), or in any other suitable manner. Although
Tank 30 may embody a reservoir configured to hold a supply of fluid. The fluid may include a hydraulic oil or any other hydraulic fluid known in the art. Pump 28 may draw fluid from and return fluid to tank 30. It is contemplated that pump 28 may be connected to multiple separate tanks 30.
Control valve 42 may meter fluid communicated between pump 28 and hydraulic cylinder 24. Control valve 42 may be connected to pump 28 via a supply line 38 and to tank 30 via a drain line 40. Control valve 42 may include at least one valve element that functions to meter pressurized fluid to one of the first and second chambers within hydraulic cylinder 24, and to simultaneously allow fluid from the other of the first and second chambers to drain to tank 30.
Control valve 42 may be pilot actuated against a spring bias to move between several positions. The positions may include a first position at which fluid is allowed to flow into the first chamber while fluid drains from the second chamber to tank 30, a second neutral position at which fluid flow is blocked from both the first and second chambers, and a third position at which the flow directions of the first position are reversed. The location of the valve element between the first, second, and third positions may determine a flow rate of the pressurized fluid into and out of the associated first and second chambers and a corresponding actuation velocity. It is contemplated that control valve 42 may alternatively be replaced with multiple independent metering valves that control the filling and draining functions of each of the first and second chambers for each hydraulic cylinder 24 separately. It is further contemplated that control valve 42 may alternatively be electrically actuated, mechanically actuated, or actuated in any other suitable manner.
Operator station 20 (see
Operation mode selector 45 may be a device that receives input from an operator, indicative of a desired operation mode. In one embodiment, operation mode selector 45 may be a rocker switch with two selectable positions. Each position of the rocker switch may correspond to an operation mode, such as, for example, a normal and an economy mode. The normal mode may allow standard operation of machine 10. The economy mode may provide improved fuel efficiency, exhaust emissions, and engine noise through regulation of power source 12. It is contemplated that operation mode selector 45 may have any number of selectable positions with associated operation modes.
Throttle lock selector 46 may receive input from an operator indicative of a requested throttle setting for power source 12. Throttle lock selector 46 may include a means for activating or deactivating a throttle lock (e.g., on/off switch, button, or dial) and a means for inputting the requested throttle setting (not shown). The throttle setting means may embody a separate device (e.g., a separate pedal, dial, or electronic keypad) or may be integrated into the activating means (e.g., a single dial with a selectable off position and a range of “on” positions associated with the requested throttle setting for power source 12). When throttle lock selector 46 is activated, power source 12 may be maintained at a requested throttle setting. It is contemplated that the requested throttle setting of throttle lock selector 46 may be adjusted automatically in response to one or more inputs.
A control system 34 may monitor and modify the performance of machine 10 and its components. In particular, control system 34 may include a task sensor 44 and a controller 48. Controller 48 may communicate with power source 12 via communication line 52, operation mode selector 45 via communication line 50, throttle lock selector 46 via communication line 58, pump 28 via communication line 54, and task sensor 44 via communication line 56. It is contemplated that controller 48 may also communicate (not shown) with transmission 16, control valve 42, and/or other components of machine 10.
One or more task sensors 44 may provide information to controller 48 that may be used to classify a current task. Each task sensor 44 may embody, for example, a work implement position and/or velocity sensor, a machine travel speed sensor, a transmission gear ratio sensor, a power source speed sensor, an operator input device sensor, a pressure sensor associated with the pressurized fluid driving work implement 32, and any other sensor associated with the performance, operation, and/or productivity of machine 10. The type and number of sensors used may vary with the application. For example, a position and/or velocity task sensor may embody a potentiometer, a tachometer, or an optical encoder. A pressure task sensor may embody a piezoelectric transducer, a capacitive sensor, or a strain gauge. Controller 48 may use the information from one or more task sensors 44 in any combination to classify a currently performed task.
Controller 48 may embody a single microprocessor or multiple microprocessors that include a means for controlling an operation of machine 10. Numerous commercially available microprocessors may be configured to perform the functions of controller 48, and it should be appreciated that controller 48 may readily embody a general machine microprocessor capable of controlling numerous machine functions. Controller 48 may include a memory, a secondary storage device, a processor, and any other components for running an application. Various other circuits may be associated with controller 48, such as, for example, power supply circuitry, signal conditioning circuitry, data acquisition circuitry, signal output circuitry, signal amplification circuitry, and other types of circuitry known in the art.
Controller 48 may use any appropriate control algorithm, such as bang-bang control, proportional control, proportional integral derivative control, adaptive control, model-based control, logic-based control, or any other control method known in the art. Controller 48 may use open loop, feedforward, and/or feedback control.
It is considered that controller 48 may include one or more maps stored within an internal memory of controller 48. Each of these maps may include a collection of data in the form of tables, graphs, and/or equations. Specifically, controller 48 may include task maps that controller 48 may use to identify the currently performed task of work implement 32. Each task map may include preset ranges and/or specific values of data that relate to a pre-programmed work implement task. The data may include, for example, a work implement position, a work implement velocity, a machine travel speed, a transmission gear ratio, a power source speed, an operator input device position, a work implement fluid pressure, and/or any other machine related data known in the art (it is contemplated that the data may be machine dependent). The pre-programmed work implement tasks may include, a digging task, a traversing task, an unloading task, and other work implement tasks. Each pre-programmed work implement task may be a high power task or a low power task. For example, a digging task may be a high power task and an unloading task may be a low power task. It is contemplated that intermediate task levels may also be included (i.e., medium power task).
Controller 48 may include internal logic to compare the preset data within the task maps to the task sensor information and/or other simulated information. The internal logic may correlate the currently performed work implement task with one of the pre-programmed work implement tasks, thus classifying the currently performed work implement task as either a high power task or a low power task. It is contemplated that the preset ranges or values of data may be updated with the task sensor information or supplied by the operator.
As shown in
Controller 48 may select an output map based on the mode selection (e.g., normal or economy mode) and the classified work implement task (e.g., high power task or low power task). Controller 48 may select an output map in order to provide the necessary power required to achieve the currently performed work implement task, yet not create unnecessary fuel consumption. It is contemplated that the output map selected by controller 48 may modify a current throttle lock setting. It is also contemplated that the output map selected by controller 48 may modify the power available to hydraulic system 22. A relationship between the power source output and the power available to hydraulic system 22 may be included in the control logic in order ensure sufficient available power to operate work implement 32. It is contemplated that the displacement of pump 28 may be modulated by controller 48 to increase the available power for the operation of work implement 32. It is also contemplated that the displacement of pump 28 may be modulated to decrease the load on power source 12, and thus decrease fuel consumption.
The disclosed control system may be applicable to any machine where power source control is desired. Particularly, the disclosed control system may provide a plurality of selectable modes of operation, including at least one economy mode. Further, the disclosed control system may automatically adjust the power source output based on the selected mode of power source operation and the classification of low and high power tasks. This adjustment according to the current task may provide an overall reduction in fuel consumption, exhaust emissions, and engine noise. The operation of control system 34 will now be described.
As shown in
When the operator selects the economy mode of operation, controller 48 may communicate with task sensor 44 to receive information regarding the task currently being performed by machine 10. Controller 48 may then, according to the disclosed control algorithm, classify the currently performed work implement task as either a high power task or a low power task (step 130).
For example, machine 10 may be a wheel loader performing a loading cycle. This loading cycle may consist essentially of a digging task, a traversing task, and an unloading task. During the loading cycle, controller 48 may receive measurements from task sensor 44 regarding the work implement position, the work implement velocity, the machine travel speed, the transmission gear ratio, the power source speed and/or load, the operator input device position, and/or the work implement fluid pressure. Controller 48 may reference these measurements with the task maps stored in its memory to classify the currently performed work implement task. For example, a digging task may be identified when work implement 32 is in a lowered position, transmission 16 is in a low forward gear ratio, and power source 12 is loaded. Controller 48 may identify the digging task as a high power task and automatically respond by implementing high power map 60 (step 120). Controller 48 may continue to use high power map 60 until the wheel loader is no longer performing a high power task and/or controller 48 classifies the currently performed work implement task as a low power task, such as, for example, a traversing task or an unloading task (step 140).
Controller 48 may select a low power map 62 that efficiently achieves the classified work implement task. For example, a work implement task that requires high power source torque but only limited power source speed may be accomplished using speed limit map 62a. Alternatively, a work implement task that requires high power source speed (e.g., task requires high run-out speed) but only limited power source torque may be accomplished using torque limit map 62b. A work implement task that requires limited power source torque and power source speed may be accomplished using torque speed limit map 62c.
Several advantages of the disclosed control system may be realized. In particular, the disclosed system may provide a plurality of selectable modes of machine operation and automatically modulate the power source output when a task requires high power operation. The combination of selectable modes of operation and automatic task adjustments, may provide increased efficiency without added operator input complexity. The disclosed system may also selectively control the power source torque and speed based on the currently performed task to enhance machine efficiency without substantially decreasing productivity.
It will be apparent to those skilled in the art that various modifications and variations can be made to the disclosed task-adjusted economy mode system without departing from the scope of the invention. Other embodiments of the machine control system will be apparent to those skilled in the art from consideration of the specification and practice of the machine control system disclosed herein. It is intended that the specification and examples be considered as exemplary only, with a true scope being indicated by the following claims and their equivalents.
