Patent Application
20140277877
This invention relates to an apparatus, system and method for driving a combine harvester with a battery electric hybrid drive.
The engine load on an internal combustion engine in a combine harvester or “combine” may increase as the vegetation density or yield increases in certain zones in a field. Internal Combustion (“IC”) engines are used to power combines under a wide variety of load conditions and must be able to accept sudden changes in load. When the combine is in a transport mode, sudden increases in power and torque are required from the engine when negotiating the terrain between fields. Tillage in the field also presents conditions where there are sudden increases in load due to changes in soil condition, where the resistance of the tillage tool increases significantly or the field has steep inclines. Engines of this type are expected to respond to these conditions by increasing output torque with relatively small variations of engine speed.
Combine harvesters currently have a basic engine torque curve to provide a nominal rated power at a power level approximately 14% below the power capability envelope of the engine. Experience has shown that a 14% power bulge with a 200 RPM droop in engine RPM provides good slug handling capability and enhanced drivability for the operator. This enables the use of a power boost for unloading or a power bulge for additional power to handle gradual increases in a load or to handle slugs or other operational overloads without excessive loss of functional engine speed or the stalling of the engine. Traditional engine torque curves for combines have been developed to use this high level of power bulge above the normal rated power in order to enhance the ability of the power train and threshing system to handle the slugs and transient overloads during the harvesting operation. Such an overload may occur when clumps of moist material suddenly enter the threshing system causing higher, short duration overloads.
At the lower power end of the operational spectrum, combines also spend significant time at very light loads, such as idling or traveling down hills. In these cases, the high end torque curves that work well for performance, such as slug acceptance, high threshing loads, unloading grain on the go, etc., do not return as good fuel economy as an engine torque curve optimized for a lower power level operation.
One approach to providing a boost in power is to provide a battery electric motor drive to supplement the IC engine power. Battery electric hybrid drives for combine harvesters are known, such as described in U.S. Pat. No. 7,949,442, herein incorporated by reference.
The present inventors have recognized that one issue with electric hybrid harvesters that are enabled by energy storage is managing the charge of the battery pack to maximize its life while at the same time achieving a useful increase in power. In this particular context, a hybrid electric system is desired to store energy in a battery pack and uses this energy when the harvester is in need of additional power.
The present inventors have also recognized the desirability to make the operator aware of the interaction between power consumption of the harvester and the charging of the battery pack. If the operator runs the combine at capacity such that the battery pack is always being drained, eventually the extra boost provided by the battery pack will be dissipated. Conversely, if the operator does not know the upper limits of the combine, then he may not take advantage of the electric boost available.
The invention provides a control of a hybrid electric hybrid drive for a combine. The invention also provides an operator interface for the drive.
A first method is an automatic control with limited operator involvement. A control algorithm would automatically adjust available combine power to add power when needed, without direction from the operator.
According to the first method, the control utilizes a control algorithm to automatically control state-of-charge (SOC) of an electrical energy storage device such as a battery pack, by either increasing power demand by increasing ground speed or decreasing power demand such as by reducing combine ground speed.
The operator will be able to input a maximum engine power percentage that he wants to utilize or a default value can automatically be used. After a short time delay, the algorithm will determine the battery pack state-of-charge along with charge level trends. Based on this information, the control algorithm adjusts engine load accordingly. This can be accomplished by adjusting ground speed which increases or decreases the propulsion power and threshing power which brings the engine power to the correct percentage to allow recharging or increased discharging of the battery pack. This algorithm is implemented to ensure that when more power is demanded by the operator, the battery pack has the power available to meet that request.
According to a first method, a control algorithm can calculate a running average of the battery pack SOC.
A target battery pack SOC is set, it can be pre-determined. If the running SOC average is above the target, then the machine loading (combine power) can be increased. If the running SOC average is below the target, the machine loading can be decreased. If the running SOC average is on the target, then the machine loading can be maintained. Changes in machine loading can be accomplished by varying the ground speed of the combine.
By using the running average of battery pack SOC, momentary swings due to transient loads can be dampened out. The system will “learn” over time what the tendency of the harvest cycle is and can modify as time progresses. The time period for averaging could be a modifiable term or adjustable by the operator. For example, setting the system to “high” sensitivity might force averaging over a short time period (10 sec or 20 sec, for example). Setting to “low” sensitivity might raise this averaging time to 10 min, 20 min or more.
By using a running average SOC, variations are filtered and unnecessary adjustments are reduced.
A second method uses mean and standard deviation to gauge SOC and make necessary adjustments. According to this approach, the actual SOC is monitored over a time interval and the values of actual SOC are associated with time durations for those values of SOC. As one example, the time interval can be the immediately prior ten minutes refreshed every minute. The mean and standard deviation of SOC values versus time duration are calculated over the selected time interval. The combine power demand, such as the combine ground speed, is adjusted when the actual SOC falls outside a selected standard deviation, and the mean is thus shifted over time to line up with the target SOC.
If the instantaneous SOC is within the “desired” histogram or bell curve area: target SOC+/−Kσ, where σ is the standard deviation calculated over the time interval, then the combine speed is maintained. If instantaneous SOC is outside the bell curve area, then the combine speed is adjusted accordingly. For example, the target SOC can be set at 50% SOC and the K value can be selected to be 3. Alternately, the K value can be selected by the operator or can be a variable, such as varying with the value of the SOC.
Over time, the mean SOC will shift toward the target SOC, but instantaneous values of SOC can be to the right or left of the target as long as within the bell-shaped target region.
A third method of the invention includes operator involvement. The operator would gain active feedback regarding the hybrid drive and the SOC of the battery pack and would be able to input a percentage of maximum engine power to utilize.
According to this aspect of the invention, a user interface for a hybrid drive for a combine is provided. The user interface can be integrated with the aforementioned automatic controls or correspond to manual, operator control of the hybrid drive. It not only displays the battery pack state-of-charge, it also shows the operator when he is benefitting from the extra power afforded to him from battery pack power. The interface includes a hybrid system power gauge, a tachometer and an adjacent SOC gauge. The SOC gauge depicts whether the battery pack is charging or discharging, which is depicted through the small arrows going to and from the hybrid system power gauge. In times of light load, the battery pack will be recharged and increase its state of charge (shown as green). During unloading on the go, slugs, or needs of transient response, the interface will tell the operator that the battery pack is being discharged (shown in orange). The operator can reduce combine power to increase battery pack SOC or increase combine power to decrease battery pack SOC, to utilize maximum combine power during operation.
Numerous other advantages and features of the present invention will become readily apparent from the following detailed description of the invention and the embodiments thereof, from the claims and from the accompanying drawings.
While this invention is susceptible of embodiment in many different forms, there are shown in the drawings, and will be described herein in detail, specific embodiments thereof with the understanding that the present disclosure is to be considered as an exemplification of the principles of the invention and is not intended to limit the invention to the specific embodiments illustrated.
In accordance with one embodiment,
An output 16 (e.g., output shaft) of the gearbox 12 provides rotational energy for propelling the vehicle, operating implements, or both. The IC engine and the electric motor generator can both propel rotation of the output 16 via the gearbox. Alternatively, the IC engine 11 can propel rotation of the motor/generator 14 via the gearbox, especially when the motor/generator functions as a generator.
An electronic control unit (ECU) 20 is signal-connected to engine controls and sensors.
An engine speed sensor 21 (e.g., revolution per minute (RPM) sensor) is associated with the internal combustion engine 11. The output of the engine speed sensor is provided directly or indirectly to the ECU 20. If the engine speed sensor provides an analog output signal, an analog-to-digital (ND) converter may be interposed between the engine speed sensor and the data processor.
The ECU 20 communicates with one or more of the following devices: the IC engine 11, an energy storage device 24, and a motor/generator control 26.
The lines interconnecting the foregoing devices 11, 24, 26 with the ECU 20 may represent one or more logical data paths, physical data paths, or both. For example, the interconnections may be realized as a databus such as an industry known CAN bus 30.
The energy storage device 24 can comprise a battery control unit 31 and a battery pack 32. The databus 30 is signal-connected to the battery control unit 31.
The motor control 26 can comprise an inverter control unit 35 that is signal-connected to a three-phase inverter 36. The databus 30 is signal connected to the inverter control unit 35.
The electric motor/generator 14 may operate in at least two modes: an electric propulsion mode and a power generation mode. In the electric propulsion mode, the electric motor/generator 14 acts as a motor where both an electric motor 14 and the engine 11 are active and propel the vehicle.
In the power generation mode, the electric motor/generator 14 acts as a generator. For example, in the power generation mode the engine 11 may drive the electric motor/generator 14.
In one configuration, the electric motor/generator 14 may comprise a direct current (DC) motor and a direct current (DC) generator.
In an alternative embodiment, the electric motor/generator 14 may comprise an alternating current (AC) motor/alternator that consumes and generates alternating current. If the electric motor/generator 14 or generator produces alternating current, a rectifier (e.g., full wave bridge rectifier or diode circuit) may be positioned between the electric motor/generator 14 and the energy storage device 24.
The motor control 26 (e.g., inverter or variable voltage source) is capable of providing a motor control signal to the electric motor/generator 14. The motor control signal may be used to control any of the following: motor rotational speed, motor torque, motor rotational direction, motor active or inactive status, and motor duty cycle.
The electric motor/generator 14 described has an alternating current configuration and the motor controller 26 comprises an inverter control unit 35 and three phase inverter 36 that converts direct current electric energy from the energy storage device 24 into alternating current. The inverter may comprise a chopper circuit, a switching circuit, or a variable frequency oscillator for controlling the frequency, phase, or pulse duration of the motor control signal to regulate or adjust an electric motor speed of the electric motor/generator 14.
Alternately, if the electric motor/generator 14 is a direct current configuration, the motor controller 26 may comprise a variable voltage source. The variable voltage source controls the voltage level or current level of the control signal to regulator or adjusts an electric motor speed of the electric motor/generator 14.
The energy storage device 24 comprises a battery pack 32. Alternately it could comprise an ultra-capacitor, a network of capacitors, a combination of the foregoing devices, or another storage device.
The energy storage device 24 receives and stores electrical energy generated by the electric motor/generator 14 in a power generation mode. The energy storage device 24 supplies stored electrical energy to the motor controller 26 in an electric propulsion mode.
The ECU 20 may comprise a microcontroller, a microprocessor, a digital signal processor, a programmable logic array, a logic device, or another device for processing data (e.g., sensor data provided by the engine speed sensor, the battery control unit 31, the inverter control unit 26, or a torque sensor). The ECU 20 may include a data storage device and data storage and retrieval software or instructions for retrieving or accessing reference data stored in the data storage device. The ECU 20 comprises an evaluator for evaluating or comparing engine speed data, engine torque data, energy storage status data (e.g., state-of-charge data), or other sensor data to reference data stored in the data storage device. The reference data may comprise baseline torque curve data, supplemental torque curve data, and engine speed data, for example.
The battery control unit 31 comprises a system for monitoring the energy storage status or state of charge (SOC) of the energy storage device 24 (e.g., battery pack). The battery control unit 31 may comprise one or more of the following components: a data processing device (e.g., microcontroller) or logic device, an ammeter or current meter, a volt meter, a thermometer, and a clock. The SOC represents the remaining capacity of a battery or battery pack in a charge/discharge cycle. The SOC may be expressed as the percentage of the remaining capacity to the full charge capacity of a cycle-aged battery pack. In one embodiment, the SOC of the battery pack may be estimated by measuring current drain and voltage levels at regular time intervals. In another embodiment, the SOC may be based on a battery model that takes into account one or more of the following: charging voltage, charging time, charging temperature, discharge rate, discharge temperature, charge recovery, cycle aging, electrochemical composition factors, and an electrical equivalent circuit. The state-of-charge data may be time-stamped or associated with a temporal indicator.
The invention provides a control of a battery electric hybrid drive for a combine. The invention also provides an operator interface for the drive.
A first method is an automatic control with limited operator involvement. A control algorithm would automatically adjust available combine power to add power when needed, without direction from the operator.
According to the first method, the control utilizes a control algorithm to automatically control a battery pack state-of-charge by either increasing or decreasing combine speed.
As shown in
In step S112, the control algorithm calculates a running average of the battery pack SOC.
A target SOC is set, or pre-determined, for example 50% of maximum SOC for the battery pack. In step S118, the algorithm compares the running average SOC with the target SOC. In step S122, if the running SOC average is above the target SOC, then the machine loading can be increased. In step S126, if the running SOC average is below the target, the machine loading can be decreased. In step S128, if the running SOC average is above the target SOC, then the machine loading can be maintained. Changes in machine loading are accomplished by varying the ground speed of the combine.
The actual values of SOC can be compared with the running average of AOC by comparing
By using a running average SOC to compare to the target SOC, variations are filtered and unnecessary adjustments are reduced.
A second method uses statistical mean and standard deviation to control SOC and make necessary adjustments as illustrated in
If instantaneous SOC is outside the bell curve area, then the system speed is adjusted accordingly.
In step S222, if the actual SOC is greater than the target range SOC+/−Kσ then the combine power demand, such as ground speed, is increased. In other words, the SOC is high enough that the combine power is underutilized and can be increased. In step S226, if the actual SOC is less than the target range SOC+/−Kσ then the combine power demand, such as ground speed, is decreased. In other words, the SOC is low enough that the combine power is over utilized and should be decreased to ensure that sufficient battery power is available when needed. In step S228, if the actual SOC is within the target range SOC+/−Kσ then the combine power demand, such as ground speed, need not be changed.
Over time, the mean SOC will shift toward the target SOC, as shown in
The third method is one where the operator is involved. The operator would gain active feedback regarding the hybrid drive and would be able to input a percentage of maximum engine power he wants to utilize.
According to this method, a user interface 300 for a hybrid drive for a combine is provided. The user interface is illustrated in
In times of light load, the battery pack will be recharged and increase its state of charge. During unloading on the go, slugs, or needs of transient response, the interface will tell the operator that the battery pack is being discharged. The interface allows an operator to manually adjust the combine load, such as to increase ground speed while monitoring the SOC drop, or to decrease speed, while monitoring the SOC gain. Alternately, the above described control algorithms can be automatically initiated to control engine speed and power to maintain the SOC at a target amount.
The useful charge range illustrated by the SOC gauge 312 need not be calibrated to exactly match the SOC percentages, in other words, a 75% on the gauge 312 doesn't have to correlate to a 75% SOC. Particularly, since the SOC may be controlled to not deviate too greatly from 50% SOC, the range displayed on the gauge 312 may show a smaller overall range of SOC values. For example, a 100% on the SOC gauge 312 can correspond to a 70% SOC and a 0% on the SOC gauge 312 can correspond to a 30% SOC gauge.
The operator interface 300 for the hybrid combine shows the driver when the combine is benefitting from the power increase provided by the battery pack, and shows live feedback of the battery pack state of charge.
From the foregoing, it will be observed that numerous variations and modifications may be effected without departing from the spirit and scope of the invention. It is to be understood that no limitation with respect to the specific apparatus illustrated herein is intended or should be inferred.
