CONTROL OF TRANSMISSION WITH ACTIVATED POWER TAKE-OFF

A method and system for operating a powertrain that includes a transmission with two power take-off outputs and transmission output shaft is described. In one example, the powertrain is operated in a speed control mode whereby vehicle speed is controlled so that powertrain control may be simplified when a vehicle is moving and a power take-off is supplying power to an external device.

TECHNICAL FIELD

The present disclosure relates to a transmission that includes power take-off ports for driving loads that may be coupled directly to a vehicle powertrain via gears. The loads may include loads that are driven while the vehicle is traveling.

BACKGROUND AND SUMMARY

A vehicle may include a transmission that includes an output shaft that is coupled to vehicle wheels and a power take-off that is coupled to an output shaft of the transmission via a planetary gear set. The power take-off may transfer torque from an internal combustion engine, or other power source (e.g., an electric machine, fuel cell, etc.), to a device that is coupled to a transmission but does not aid in motion of the vehicle. For example, the power take-off may provide mechanical power to a pump that supplies pressurized fluid to a pump in a hydraulic circuit. The power take-off may rotate at a requested speed when the vehicle is stationary and not traveling on a road with its wheels rotating. The requested speed may be based on the device that is coupled to the power take-off. However, if the vehicle is traveling on a road with its wheels rotating, the power take-off may be deactivated (e.g., adjusted to zero rotational speed) because maintaining a requested wheel torque may be difficult when load on the power take-off changes. For example, because torque at the transmission output shaft and torque at the power take-off output are coupled, it may be possible to provide torque to the transmission output shaft or the power take-off in an unintended rotational direction and/or at an unintended rate of speed change. Further, driving while the wheels and power take-off are engaged may lead to a vehicle's human driver having to learn unnatural driving behaviors to operate the vehicle in an intended way. While it may be possible to dynamically estimate torque that is delivered to the power take-off and the vehicle's wheels, or to estimate torque at an input shaft of the transmission and a power take-off that is coupled to the input shaft of the transmission, generating these estimates may be financial prohibitive. In addition, the system complexity may be greater and there may be greater possibility of sensor degradation. Therefore, it may be desirable to provide a way of controlling a power take-off output and transmission shaft output in a way that reduces the possibility of unintended directional rotation without having to accurately estimate torque at the transmission output shaft and the power take-off.

The inventors herein have recognized the above-mentioned issues and have developed a powertrain, comprising: a transmission including a power take-off and an output shaft that delivers torque to vehicle wheels, where the power take-off is coupled to the output shaft via a planetary gear set; and a controller including executable instructions that cause the controller to operate the powertrain in a first speed control mode where a speed of the output shaft is controlled via the controller in response to a vehicle that includes the powertrain traveling with rotating wheels while delivering power to the power take-off.

By operating the powertrain in a speed control mode where vehicle speed is controlled while a vehicle is moving and a power take-off of the vehicle is activated, it may be possible to avoid unintended movement of the vehicle and operate the power take-off device. Further, it may be possible to avoid additional financial expenses of estimating torque at various locations along the powertrain. In particular, since a speed controller uses feedback of vehicle speed instead of an estimated torque at a particular location along the driveline, the vehicle may be controlled with a readily available speed feedback signal without having to estimate torque at the transmission output shaft and at the power take-off.

The present description may provide several advantages. In particular, the approach may increase powertrain functionality by allowing a vehicle that includes a second power take-off to operate in a desired way when a vehicle is moving. In addition, the approach may reduce a possibility of a vehicle traveling in an unintended direction and unintended rates of speed change for a vehicle. Further, the approach may allow a vehicle operator to operate the vehicle in a natural or expected way.

The accompanying drawings are incorporated herein as part of the specification. The drawings described herein illustrate embodiments of the presently disclosed subject matter, and are illustrative of selected principles and teachings of the present disclosure. However, the drawings do not illustrate all possible implementations of the presently disclosed subject matter, and are not intended to constrain the scope of the present disclosure in any way.

DETAILED DESCRIPTION

The following description relates to systems and methods for operating a moving vehicle that includes a power take-off device to drive external loads. The vehicle may include a transmission with two power take-off ports that may be driven via an external power source or via an electric machine that is included in the transmission. The transmission may be included in a two or four wheel drive vehicle as shown inFIG.1. The transmission may be configured as shown inFIG.2, and the transmission may include the components that are shown inFIG.3. The transmission may be operated according to the control block diagram that is shown in the block diagram ofFIG.4. The transmission controller may constrain wheel torque between two thresholds as shown inFIG.5. In one example, the controller may be a proportional/integral/derivative (PID) controller as shown inFIG.6.

FIG.1illustrates an example vehicle powertrain199included in vehicle10. Vehicle10includes a front side110and a rear side111. Vehicle10includes front wheels102and rear wheels103. Vehicle10includes a propulsion source12(e.g., internal combustion engine or electric machine) that may selectively provide propulsive effort to front axle191and rear axle190. In other examples, the propulsion source12may provide propulsive effort solely to front axle191or solely to rear axle190. Propulsion source12is shown mechanically coupled to transmission14via transmission input shaft129. In some examples, the engine's crankshaft (not shown) may be coupled to transmission input shaft129. Transfer case193routes mechanical power from transmission output shaft130to front axle191and rear axle190.

Electric energy storage device16(e.g., a traction battery or capacitor) may provide electric power to electric machines included in transmission14. Transmission14may supply mechanical power to mechanically driven accessories18and20. Transmission14may be operated via controller15. In this example, controller15is configured to command electric machines (not shown), clutches (not shown), and brakes (not shown) within transmission14. Controller15may switch operating modes of transmission14via adjusting states of clutches and brakes as indicated inFIG.4. Controller15may also receive a position of a driver demand pedal100from driver demand pedal position sensor108, which may be an input for determining the operating state of transmission14. The driver demand pedal100and the driver demand pedal position sensor108may react to movement caused by human driver109. Brake pedal122may be applied by human driver109and brake pedal sensor120provides an indication of brake pedal position to controller15. Controller15may receive data from sensors177. Sensors177may include, but are not constrained to a vehicle speed sensor, a transmission temperature sensor, transmission input shaft speed sensor, transmission output shaft speed sensor, wheel speed sensors, and an ambient temperature sensor. Controller15may adjust operating states of the vehicle powertrain199via adjusting operating states of actuators178. Actuators178may include but are not constrained to electric machines, inverters, clutches (C0-C2), brakes (B1/B2), and engine torque actuators (throttle, cams, fuel injectors, spark actuator). Controller15includes a processor15afor executing instructions, read-only memory15b, and random access memory15c. In this example, a single controller15is shown, but in other examples several controllers may operate together in a distributed system to perform the methods described herein. Controller15may receive input from and provide output to human/machine interface195(e.g., touch screen display, pushbuttons, etc.).

Referring now toFIG.2, a block diagram of transmission14is shown. Transmission14is shown with5ports that are labeled P1-P5. Port1(P1) is configured to receive mechanical energy from propulsion source12(e.g., internal combustion engine or electric machine). Alternatively, port1may deliver mechanical energy to external power source12. Port2(P2) is a port that receives electrical power from electric energy storage device16. Alternatively, port2may provide electrical power to electric energy storage device1. Electrical ports2are shown directly electrically coupled to a first inverter206and a second inverter204. First inverter206may convert direct current (DC) to alternating current (AC). AC may be delivered from first inverter206to first electric machine210. Likewise, AC may be delivered from second inverter204to second electric machine208. Alternatively, first and second electric machines210and208may deliver AC power to inverters206and204. Electric machines210and208may supply mechanical power to gears, clutches, and brakes202. As such, electric machines210and208may also be referred to as propulsion sources. Gears, clutches, and brakes202may transfer mechanical power to output ports P3-P5. Output port P3may transfer mechanical power to wheels103. Output port P4may transfer mechanical power to power take-off (PTO1)212and accessories18, the accessories18not including vehicle wheels. Output port P5may transfer mechanical power to power take-off (PTO2)214and accessories20, the accessories20not including vehicle wheels.

Turning now toFIG.3, a detailed view of one example of transmission14is shown. In this example, propulsion source12is shown coupled to transmission input shaft129. Transmission input shaft129is coupled to clutch C0and clutch C0may selectively couple transmission input shaft129to connecting shaft304. Clutch C0is directly coupled to ring gear326of first planetary gear set PT1and PTO1gear360via connecting shaft304. PTO1gear360may be coupled to accessories18via PTO1shaft362. First planetary gear set PT1also includes planetary gears316and a sun gear322. Sun gear322is shown coupled to PTO2gear340and electric machine210. Planetary gears316couple sun gear322to ring gear326. Carrier328supports planetary gears316. PTO2gear340may be selectively coupled to PTO2output shaft342via PTO2clutch C2. PTO2output shaft342may be directly coupled to accessories20, and accessories20are not coupled to vehicle wheels.

Connecting shaft304may be selectively coupled to electric machine208and sun gear306of third planetary gear set PT3via closing input coupled clutch C1. Sun gear306of third planetary gear set PT3is coupled to planetary gears308. Planetary gears308are coupled to ring gear310, and planetary gears308are supported via carrier312. Planetary gears308are coupled to ring gear318of second planetary gear set PT2and planetary gears316of first planetary gear set PT1via carrier312of third planetary gear set PT3and carrier328of first planetary gear set PT1. Carrier328of first planetary gear set PT1is coupled to wheels103via transmission output shaft130. Brake B1may be closed to ground or couple ring gear310of third planetary gear set PT3to transmission housing399.

Second planetary gear set PT2includes a sun gear314that is coupled to ring gear310of first planetary gear set PT1. Planetary gears308of second planetary gear set PT2are coupled to sun gear314of planetary gear set PT2and ring gear318of second planetary gear set PT2. Brake B2may be closed to ground or couple carrier320of second planetary gear set PT2to transmission housing399.

PTO1is directly coupled to connecting shaft304. Therefore, whenever connecting shaft304is rotating, PTO1output shaft362rotates. PTO1output shaft362may be rotated via closing clutch C0when propulsion source12is rotating. PTO1may also be rotated via electric machine208by closing clutch C1. PTO1may rotate in any of the modes that are shown in the table ofFIG.4.

PTO2may rotate and provide mechanical power to accessories20during three modes as indicated inFIG.4. In a hill hold mode, brakes B1and B2may be closed to lock rotation of transmission output shaft130and PTO2output shaft342may be rotated via torque generated via electric machine210and/or propulsion source12. In this way, PTO2output shaft342may rotate at a speed that is a multiple of a rotational speed of propulsion source12and connecting shaft304.

PTO2output shaft342may be rotated when clutch C1is open, C2is closed, and C0is open or closed. PTO2output shaft342may also provide mechanical torque to accessories20when brake B1is open, B2is closed, C1is open, C2is closed and C0is open or closed. Applying brake B2prevents rotation of carrier320so that when propulsion source12or electric machine208drive the transmission output shaft130via connecting shaft304, second planetary gear set PT2, and first planetary gear set PT1, PTO2gear340may rotate. Energy may flow from propulsion source12to connecting shaft304via clutch C0, connecting shaft304may transfer torque to ring gear326causing planetary gears316to rotate along with sun gear322so that carrier328and transmission output shaft130may rotate. Rotating sun gear322allows PTO2gear340to rotate. PTO2output shaft342may rotate when clutch C2is closed.

Thus the system ofFIGS.1-3may provide for a powertrain, comprising: a transmission including a power take-off and an output shaft that delivers torque to vehicle wheels, where the power take-off is coupled to the output shaft via a planetary gear set; and a controller including executable instructions that cause the controller to operate the powertrain in a first speed control mode where a speed of the output shaft is controlled via the controller in response to a vehicle that includes the powertrain traveling with rotating wheels while delivering power to the power take-off. In a first example, the powertrain further comprises operating the power take-off in a second speed control mode while operating the powertrain in the first speed control mode. In a second example that may include the first example, the powertrain includes where a first speed controller of the controller controls the output shaft speed, and where a second speed controller of the controller controls the power take-off. In a third example that may include one or more of the first and second examples, the powertrain includes where the first speed controller controls the output shaft to a first speed, where the second speed controller controls the power take-off speed to a second speed, and where the second speed is different than the first speed. In a fourth example that may include one or more of the first through third examples, the powertrain includes where the first speed controller adjusts torque of a propulsion source in response to a difference between a requested vehicle speed and an actual vehicle speed. In a fifth example that may include one or more of the first through fourth examples, the powertrain includes where the requested vehicle speed is based on a position of a driver demand pedal. In a sixth example that may include one or more of the first through fifth examples, the powertrain includes where the second speed controller adjusts torque of an electric machine in response to a difference between a requested power take-off speed and an actual power take-off speed.

Thus, the system ofFIGS.1-3also provides for a powertrain, comprising: a transmission including a first power take-off port including a power take-off shaft that rotates at a multiple of a rotational rate of a first shaft, the first shaft coupled to a ring gear of first planetary gear set, a second shaft configured to deliver power to vehicle wheels, the second shaft coupled to carrier planetary gears of the first planetary gear set; and a second power take-off port, the second power take-off port coupled to a sun gear of the first planetary gear set, the first power take-off port and the second power take-off port not configured to be coupled to the second shaft, except via the first planetary gear set; and a controller including executable instructions that cause the controller to operate the powertrain in a speed control mode in response to a vehicle that includes the powertrain traveling with rotating wheels while delivering power to the second power take-off port. In a first example, the powertrain includes where the speed control mode includes controlling a vehicle speed, and further comprising: additional instructions to control the vehicle speed via vehicle speed feedback. In a second example that may include the first example, the powertrain further comprises additional instructions to control the vehicle speed in response to a requested vehicle speed, and where the requested vehicle speed is based on a position of a driver demand pedal. In a third example that may include one or both of the first and second examples, the powertrain further comprises additional instructions to control a speed of a shaft of the second power take-off port. In a four example that may include one or more of the first through third examples, the powertrain further comprises additional instructions to confine wheel torque output to be between a first threshold wheel torque and a second threshold wheel torque.

Referring now toFIG.4, an example block diagram400of a vehicle speed controller402and a power take-off speed controller403for a second power take-off (P5ofFIG.1) for the powertrain199ofFIG.1is shown. The vehicle speed controller402and the power take-off speed controller403may be included in controller15ofFIG.1as executable instructions stored in non-transitory memory. Further, block diagram400in cooperation with the system ofFIGS.1-3may include taking actions taken in the physical world to transform an operating state of the system ofFIGS.1-3via adjusting positions of the various actuators.

The vehicle speed controller402may receive input via a driver demand pedal100and a brake pedal. The driver demand pedal position and the brake pedal position are input to block418. Block418converts the brake pedal position and driver demand pedal position in a requested vehicle speed. In one example, block418may include a function or table419that is referenced or indexed via driver demand pedal position and brake pedal position. The function or table outputs an empirically determined requested vehicle speed. The requested vehicle speed values may be determined via applying the driver demand pedal and brake pedal and adjusting the requested vehicle speed until vehicle performance objectives are met. The requested vehicle speed is input to block416.

Block416represents a vehicle speed controller. In one example, the vehicle speed controller is a proportional/integral/derivative (PID) controller as described inFIG.6. Alternatively, the vehicle speed controller may be a linear quadratic controller or other known type of controller. Block416outputs a requested wheel torque to block414. The controller of block416may receive vehicle speed feedback and adjust the requested wheel torque according to a vehicle speed error that is a difference between the requested vehicle speed and the actual vehicle speed. The controller of block416may adjust actual vehicle speed to follow a requested vehicle speed that is a function of wheel speed via adjusting wheel torque, such that wheel torque is allowed to vary so that the actual vehicle speed meets the requested vehicle speed. In this way, powertrain119is operated in a speed control mode.

At block414, the requested wheel torque may be constrained to be within an upper torque threshold and a lower torque threshold via a filter as shown inFIG.5. The output of block414is a filtered requested wheel torque and the powertrain119may be commanded to the filtered requested wheel torque. The powertrain119may respond to the filtered requested wheel torque via generating wheel torque via a propulsion source of the powertrain119. The wheel speed which may indicate vehicle speed is fed back to block416where it is applied to correct the requested wheel torque.

Blocks420and422are optional as indicated by the dashed lines. If block420is present, it receives input of driver demand pedal position and brake pedal position. A table or function421may be referenced or indexed via driver demand pedal position and brake pedal position. The table or function421outputs a requested wheel torque and the requested wheel torque is input to block422.

If block422is present, the powertrain119may be operated in torque control mode or in vehicle speed control mode. If human driver109requests operation of PTO2and the vehicle is traveling with its wheels rotating, block422may switch such that the filtered wheel torque output from block414is commanded of the powertrain119. On the other hand, if human driver109is not requesting operation of PTO2, block422may switch such that requested wheel torque output from block420is commanded of the powertrain119. If block422is not present, the filtered requested vehicle speed is directly commanded of the powertrain119. Additionally, if block422is not present, the vehicle may operate solely in vehicle speed control mode. Powertrain119may adjust torque output of one or more propulsion sources (e.g., electric machine or internal combustion engine) to generate the torque that produces the requested vehicle speed, wheel torque, and PTO speed.

In addition to vehicle speed controller402, a speed controller403for PTO2is included to control the rotational speed of PTO2. Human driver109may request a rotational speed for PTO2via human/machine interface404. The human/machine interface may output a requested rotational speed for PTO2to block406.

Block406represents a PTO rotational speed controller for PTO2. In one example, the vehicle speed controller is a proportional/integral/derivative (PID) controller similar to the speed controller that is described inFIG.6. Alternatively, the PTO rotational speed controller may be a linear quadratic controller or other known type of controller. Block406outputs a requested rotational PTO speed (e.g., a PTO that has been requested via a human operator or via a controller) to block408. The controller of block406may receive rotational speed feedback from PTO2and adjust the requested PTO2torque according to a PTO2rotational speed error that is a difference between the requested rotational PTO2speed and the actual rotational PTO2speed. The controller of block506may adjust actual rotational PTO2speed to follow a requested rotational PTO2speed via adjusting a PTO2torque command, such that PTO2torque is allowed to vary so that the actual rotational PTO2speed meets the requested rotational PTO2speed. In this way, powertrain119may operate PTO2in a rotational speed control mode.

At block408, the requested rotational PTO2speed may be constrained to be within an upper torque threshold and a lower torque threshold via a filter. The output of block408is a filtered requested rotational PTO2speed and the powertrain119may be commanded to the filtered requested rotational PTO2speed. The powertrain119may respond to the filtered requested rotational PTO2speed via generating PTO2via a propulsion source of the powertrain119. The rotational PTO2speed is fed back to block406where it is applied to correct the requested rotational PTO2speed. The filtered requested rotational PTO2speed is commanded of the powertrain119. Powertrain119may rotate accessories20(e.g., a pump) at the requested rotational PTO2speed.

Thus, the control block diagram ofFIG.4provides for a method for operating a powertrain, comprising: operating the powertrain in a speed control mode where a speed of a vehicle speed is controlled to a requested vehicle speed via a controller and in response to a power take-off supplying power to a device external to a transmission and a vehicle that includes the transmission traveling with rotating wheels. In a first example, the method for operating the powertrain includes where the speed control mode includes adjusting the speed of the vehicle to the requested vehicle speed while torque supplied via the powertrain is varied. In a second example that may include the first example, the method for operating the powertrain further comprises torque supplied via the powertrain in response to a difference between the requested vehicle speed and the vehicle speed. In a third method that may include one or more of the first and second methods, the method for operating the powertrain includes where the controller is a proportional, integral, derivative controller. In a fourth method that may include one or more of the first through third methods, the method for operating the powertrain further comprises operating the power take-off in a speed control mode via a second controller. In a fifth method that may include one or more of the first through fourth methods, the method for operating the powertrain includes where the second controller is a proportional, integral, derivative controller. In a sixth method that may include one or more of the first through fifth methods, the method for operating the powertrain includes where operating the powertrain in the speed control mode includes adjusting a wheel torque output of the powertrain, and further comprising: confining the wheel torque output to be between a first threshold torque and a second threshold torque. In a seventh method that may include one or more of the first through sixth methods, the method for operating the powertrain includes where the first threshold torque and the second threshold torque vary with the vehicle speed.

In another representation, the method ofFIG.4provides for a method for operating a powertrain, comprising: operating the powertrain in a speed control mode where a speed of a vehicle speed is controlled to a requested vehicle speed via a controller and in response to a power take-off supplying power to a device external to a transmission and a vehicle that includes the transmission traveling with rotating wheels; and not operating the powertrain in the speed control mode and operating the powertrain in a torque control mode in response to the power take-off not supplying power to the device external to the transmission and the vehicle that includes the transmission traveling with rotating wheels. In torque control mode, torque of the vehicle (e.g., wheel torque) is adjusted to follow a target or requested torque and vehicle speed is allowed to vary. In speed control mode, vehicle speed is adjusted to follow a target or requested vehicle speed and vehicle torque (e.g., wheel torque) is allowed to vary.

Referring now toFIG.5, a plot that shows an allowable torque range for a powertrain that is operating with PTO2active (e.g., rotating and providing torque to an external accessory and not the vehicle's wheels) in a vehicle that is traveling with its wheels rolling is presented. The horizontal axis represents vehicle speed and vehicle speed increases in the direction to the right of the vertical axis. Vehicle speed magnitude increases in the direction to the left of the vertical axis. The vertical axis represents wheel torque and wheel torque is positive and increasing in the direction of the vertical axis arrow above the horizontal axis. Wheel is negative below the horizontal line and the magnitude of negative wheel increases in the direction of the vertical axis arrow that is below the horizontal line.

Solid line502represents an upper torque threshold that is not to be exceeded by wheel torque when operating the powertrain with PTO2active and the vehicle traveling with its wheels rotating. Dashed line504represents a negative torque threshold with a magnitude that is not to be exceeded by wheel torque when operating the powertrain with PTO2active and the vehicle traveling with its wheels rotating. Thus, the allowable range for wheel torque is between threshold502and threshold504. The commanded or final wheel torque may vary between the thresholds (502and504), but its magnitude is constrained not to be in the area that is above threshold502and constrained not to be in the area that is below threshold504.

The vehicle speeds between vertical line550and vertical line551represent a range where wheel torque increases as a magnitude of negative vehicle speed (e.g., travel in reverse) decreases. The vehicle speeds between vertical line552and vertical line553represent a range where wheel torque decreases as a magnitude of positive vehicle speed (e.g., travel in a forward direction) increases.

Thus, it may be observed that for lower vehicle speeds, larger amounts of wheel torque may be generated via the powertrain in forward (positive) and reverse (negative) directions. This allows for a low requested vehicle speed (e.g., zero) via adjusting vehicle brakes while PTO2is active. At higher vehicle speeds, regenerative braking torque is constrained to a small value such that when actual vehicle speed is greater than the requested vehicle speed, the vehicle coasts (e.g., moves without sending powertrain torque to the wheels).

Turning now toFIG.6, a block diagram600of an example PID controller is shown. The PID controller ofFIG.6may be applied as a vehicle speed controller and/or a PTO speed controller by simply adjusting the signals that are input to the PID controller and directing the output of the PID controller to a proper system or actuator.

At summing junction606, actual or measured vehicle speed is subtracted from a requested vehicle speed to generate a vehicle speed error. The vehicle speed error is delivered to blocks608-612. At block608, a proportional scalar or gain (e.g., a real number) variable Kpis multiplied by the vehicle speed error (e) that is a function of time to generate a proportional component of the PID controller output. Block608outputs the proportional component of the PID controller to summing junction614. At block610, an integral scalar or gain (e.g., a real number) variable Kiis multiplied by the integral of the vehicle speed error (e) to generate an integral component of the PID controller output. Block610outputs the integral component of the PID controller to summing junction614. At block612, a derivative scalar or gain (e.g., a real number) variable Kdis multiplied by the derivative of vehicle speed error (e) to generate a derivative component of the PID controller output. Block612outputs the proportional component of the PID controller to summing junction614. The PID control adjustment to generator torque is output from summing junction614to the powertrain119(not shown).

It will be appreciated that the configurations and routines disclosed herein are exemplary in nature, and that these specific examples are not to be considered in a constrained sense, because numerous variations are possible. For example, the above technology can be applied to powertrains that include different types of propulsion sources including different types of electric machines and transmissions. The subject matter of the present disclosure includes all novel and non-obvious combinations and sub-combinations of the various systems and configurations, and other features, functions, and/or properties disclosed herein.