System for operating a vehicle with electric power take-off

Abstract

Electric drive system comprising: a first electrical machine; a second electrical machine; a transmission, the transmission being mechanically coupled to one or more rotatable wheels and the first electric machine; a separating clutch configured to selectively couple the second electric machine to the transmission; a power take-off arranged to supply a device with mechanical rotational energy; a power take-off disconnect clutch configured to selectively couple the second electric machine to the power take-off; and one or more controllers, wherein the one or more controllers include executable, non-transitory instructions that cause the one or more controllers to actuate the power take-off disconnect clutch and the disconnect clutch.

Description

TECHNICAL FIELDThe present disclosure relates to the operation of an electric vehicle that includes a power take-off.BACKGROUND AND SUMMARYInternal combustion engines may be configured to propel a vehicle and power an auxiliary power take-off device. The power take-off device may provide power to a system that is unable to provide power to the wheels of the vehicle. The auxiliary power take-off may, for example, provide mechanical energy to drive a pump that pumps hydraulic fluid to actuate hydraulic cylinders. Further, the power take-off may rotate a mixing device and / or provide power outside the vehicle that includes the power take-off. However, power take-offs for electric vehicles present other challenges than power take-offs that are driven via an internal combustion engine. For example, power take-offs of electric vehicles cannot provide rotational force in the desired direction when an electric vehicle is driving in forward or reverse gear. In addition, a power take-off of an electric vehicle may not rotate at the desired speed when a vehicle including the power take-off device is traveling at low speed. For at least these reasons, it may be desirable to oversee the power take-off for electric vehicles.The present inventors have recognized the above issues and developed an electric drive system comprising: a first electric machine; a second electric machine; a transmission, the transmission mechanically coupled to one or more rotatable wheels and the first electric machine; a disconnect clutch configured to selectively couple the second electric machine to the transmission; a power take-off configured to provide mechanical rotational energy to a device; a power take-off disconnect clutch configured to selectively couple the second electric machine to the power take-off; and one or more controllers, the one or more controllers including executable non-transitory instructions that cause the controller to operate the power take-off disconnect clutch and the disconnect clutch.By constructing a propulsion system that includes a disconnect clutch and a power take-off disconnect clutch, the direction of rotation and speed of the power take-off may be controlled independently of vehicle speed. If the operation of the auxiliary output is not requested or desired, an electric machine that selectively provides mechanical power to an apparatus for the auxiliary output may provide tractive force to a powertrain of a vehicle. Moreover, under certain conditions, the electric machine may provide power to the vehicle's auxiliary power take-off and powertrain. This may improve the capabilities of the electric machine.The present description may provide several advantages. In particular, the approach may enable improved control of the auxiliary output of an electric machine. Moreover, the approach may improve the capabilities of an electric machine and enable independent control of a power take-off that may provide energy to a device external to a vehicle's powertrain. Moreover, the approach enables automatic control of an auxiliary power take-off device depending on the vehicle operating condition.It should be understood that the summary above is provided to introduce in simplified form a selection of concepts that are further discussed in the detailed description. It is not intended to identify key features of the claimed subject matter, the scope of which is clearly defined by the claims that follow the detailed description. Moreover, the claimed subject matter is not limited to implementations that address the shortcomings recited above or in other parts of this disclosure.BRIEF DESCRIPTION OF THE DRAWINGSFIG. 1 is an illustration of an example vehicle that includes an electric vehicle propulsion system. FIG. 2 is a dash line diagram showing an exemplary configuration of a step-variable transmission including an auxiliary power take-off device. FIG. 3 shows the operating modes of the drive train corresponding to the relationship between tractive force and vehicle speed. FIG. 4 shows a block diagram of an example method of operating an electric vehicle. FIG. 5 shows the available tractive effort for an example electric vehicle with a two-step transmission.DETAILED DESCRIPTIONA method and system for providing power take-off and tractive effort to an electric vehicle are described. The electric vehicle may have a two-speed transmission (e.g., a two-forward transmission) or a transmission with more than two ratios. The electric vehicle may include two separate and independent electric machines, as shown in FIGS. 1 and 2. The electric machines and the auxiliary power take-off may operate in different operating modes depending on the relationship between tractive force and vehicle speed, as shown in FIG. 3. The electric machines and transmission may be operated according to the method illustrated in the block diagram of FIG. 4. The electric vehicle may provide tractive force depending on which gears of the transmission are engaged, as shown in FIG. 5.FIG. 1 illustrates an example vehicle propulsion system 199 for the vehicle 10. The front end of the vehicle is indicated at 110 and the rear end of the vehicle at 111. The vehicle 10 is travelling in a forward direction when the front end 110 of the vehicle is beginning to move the vehicle 10. The vehicle 10 travels in the rearward direction when the rear end 111 of the vehicle is beginning to move the vehicle 10. In this example, the vehicle 10 is a rear wheel drive vehicle, but in other examples, the vehicle 10 may be an all wheel drive or front wheel drive vehicle.The vehicle propulsion system 199 includes a first propulsion source 105 (e.g., an electric machine such as an engine) and a second electric machine 132. In one example, the propulsion sources 105 and 132 may be synchronous or inductive electric machines that operate as motors or generators. In other examples, the propulsion sources 105 and 132 may be a direct current (DC) machine. The second electric machine 132 may selectively provide power to a power take-off 129 according to user input at the power take-off interface 128, as further shown in FIG. 2. Vehicle propulsion system 199 also includes a transmission 135. The drive sources 105 and 132 are connected to the transmission 135. The power sources 105 and 132 provide power from their respective rotors 105 aand 132 ato the transmission 135. The transmission 135 may be mechanically connected to differential gears 106. The differential gears 106 may be coupled to two axle shafts, including a first or right axle shaft 190 aand a second or left axle shaft 190 b. The vehicle 10 also includes front wheels 102 and rear wheels 103.The transmission 135 may be referred to as a step-change transmission and may be configured as shown in more detail in FIG. 2. The transmission 135 may include one or more clutch actuators (not shown) to shift one or more clutches. The inverter 115 is electrically coupled to the drive source 105 to convert direct current to alternating current (AC), and vice versa. Similarly, the electric inverter 130 is electrically connected to the drive source 132 to convert direct current to alternating current (AC), and vice versa. The powertrain controller 116 is electrically coupled to sensors 117 and actuators of the vehicle propulsion system 199. The sensors 117 may include, for example, but are not limited to, temperature sensors for inverter switches, temperature sensors for electric machine windings, temperature sensors for bus bars, etc.The transmission 135 may transmit or receive mechanical power to or from the differential gears 106. The differential gears 106 can transmit mechanical power to and receive mechanical power from the rear wheels 103 via the right axle shaft 190 aand the left axle shaft 190 b. The drive sources 105 and 132 may consume alternating current (AC) provided via their respective inverters 115 and 130. Alternatively, the drive sources 105 and 130 may also provide alternating current to their respective inverters 115 and 130. The inverters 115 and 130 may be supplied with high voltage direct current (DC) from the battery 160 (e.g., a traction battery, which may also be referred to as an electrical energy storage device or battery pack). The inverters 115 and 130 may convert the direct electric current from the battery 160 into alternating electric current for the drive sources 105 and 132. Alternatively, the inverters 115 and 130 may be supplied with alternating current from their respective drive sources 105 and 132. The inverters 115 and 130 may convert the alternating current from their respective drive sources 105 and 132 into direct current and store it in the battery 160.The power sources 105 and 132 may transmit or receive mechanical power to or from the transmission 135. Thus, the transmission 135 may be a multi-speed gear set that switches between the transmission ratios upon command of the powertrain controller 116. The powertrain controller 116 includes a processor 116 aand a memory 116 b. The memory 116 b(e.g., storage media) may include read-only memory, random access memory, and diagnostic memory. The memory may be programmed with computer readable data representing instructions executable by a processor for performing the methods and control techniques described herein, as well as other variants that are expected but not expressly listed. Thus, the control techniques, methods, and the like described herein may be stored as instructions in non-transitory memory.The battery 160 may periodically receive electrical energy from a power source, such as a stationary power grid 5, located outside the vehicle (e.g., not part of the vehicle). As a non-limiting example, vehicle propulsion system 199 may be configured as a plug-in electric vehicle (EV), where electrical energy may be provided to battery 160 via stationary grid 5 and charging station 12. The battery 160 can be supplied with electrical charge via the socket 100.The battery 160 may include a BMS controller 139 (e.g., a battery management system controller) and a power distribution box 162. The BMS controller 139 may take over charge balancing between the energy storage elements (e.g., the battery cells) and communication with other vehicle controllers (e.g., the vehicle control unit 152). The BMS controller 139 includes a core processor 139 aand a memory 139 b(e.g., memory, read-only memory, and diagnostic memory).The vehicle 10 may include a vehicle control unit (VCU) 152 that may communicate with the electric inverter 115, the electric inverter 130, the powertrain controller 116, the friction or sliding saddle control 170, the global positioning system (GPS) 188, the BMS controller 139, and the dashboard 186 and the components included therein via the controller area network (CAN) 120. The VCU 152 includes the memory 114, which may include read only memory (ROM or non-volatile memory) and random access memory (RAM). The VCU also includes a digital processor or central processing unit (CPU) 153 and inputs and outputs (I / O) 118 (e.g., digital inputs including counters, timers and discrete inputs, digital outputs, analog inputs and analog outputs). The VCU may receive signals from the sensors 154 and output control signals to the actuators 156. Sensors 154 may include, but are not limited to, lateral accelerometers, longitudinal accelerometers, yaw rate sensors, inclinometers, temperature sensors, battery voltage and current sensors, and other sensors described herein. Additionally, the sensors 154 may include a steering angle sensor 197, a driver pedal position sensor 141, vehicle ranging sensors including radio detection and ranging (RA-DAR), light detection and ranging (LIDAR), sound navigation and ranging (SO-NAR), and a caliper pedal position sensor 151. The actuators include, but are not limited to, inverters, transmission controllers, indicators, human-machine interfaces, friction tong systems, and the battery controller described herein.The driver request pedal position sensor 141 is connected to the driver request pedal 140 to determine a degree of operation of the driver request pedal 140 by the human 142. The caliper pedal position sensor 151 is shown coupled to the caliper pedal 150 to determine the degree of actuation of the caliper pedal 150 by the person 142. The steering angle sensor 197 is configured to determine the steering angle depending on the position of the steering wheel 198.Vehicle propulsion system 199 is shown having a global positioning system 188 that receives time and position data from one or more GPS satellites 189. The global positioning system may also include geographic maps in the ROM to determine the position of the vehicle 10 and the characteristics of the roads on which the vehicle 10 may travel.The vehicle propulsion system 199 may also include an instrument panel 186 with which the driver of the vehicle may interact. The dashboard 186 may include a display system 187 configured to display information to the vehicle operator. The display system 187 may include, by way of non-limiting example, a touch screen or human machine interface (HMI) that enables the vehicle operator to display graphical information and input instructions. In some examples, display system 187 may be wirelessly connected to the Internet (not shown) via a VCU 152. Thus, in some examples, the vehicle operator may communicate with an Internet site or software application (app) as well as the VCU 152 via the display system 187.The instrument panel 186 may also include an operator interface 182 through which the operator may adjust the operating state of the vehicle. In particular, the operator interface 182 may be configured to enable and / or disable operation of the vehicle powertrain (e.g., the propulsion source 105) based on operator input. Additionally, a vehicle operator may request an axle mode (e.g., park, reverse, neutral, drive) via the operator interface. Various examples of the operator interface 182 may include interfaces that use a physical device, such as a key, that may be inserted into the operator interface 182 to activate the vehicle propulsion system 199, including propulsion sources 105 and 132, to turn on the vehicle 10. The device may be removed to deactivate the transmission 135 and the propulsion sources 105 and 132 and shut down the vehicle 10. The drive sources 105 and 130 may be activated by supplying electric power to the drive sources 105 and 132 and the inverters 115 and 130. The drive sources 105 and 132 can be turned off by cutting off the power supply to the drive sources 105 and 132 and the inverters 115 and 132. In other examples, additionally or optionally, a start / stop button may be used that is manually pressed by the operator to start or shut down the propulsion sources 105 and 132 and turn the vehicle on or off. In other examples, a remote electric axle or machine start may be initiated by a remote device (not shown), e.g., a cellular phone or smart phone-based system, where the user's cellular phone sends data to a server and the server communicates with the vehicle controller 152 to activate the inverters 115 and 130 as well as the propulsion sources 105 and 132. The spatial orientation of the vehicle 10 is indicated by the axes 175.The vehicle 10 is also shown with a ground or friction tong controller 170. The friction tong controller 170 may selectively actuate and release friction calipers (e.g., 172 aand 172 b) by flowing hydraulic fluid to the friction calipers. The friction pliers may be actuated and released to reduce locking of the friction pliers to the front wheels 102 and the rear wheels 103. The wheel position or wheel speed sensors 161 may provide wheel speed data to the friction caliper controller 170. The vehicle propulsion system 199 may transmit torque to the rear wheels 103 to propel the vehicle 10.A human or autonomous driver 142 may request a driver demand torque or, alternatively, a driver demand tractive force by actuating the driver demand pedal 140 or providing a driver demand wheel torque / tractive force request to the vehicle control unit 152. The vehicle control unit 152 may then request torque or tractive force from the propulsion sources 105 and 132 via control of the powertrain 116. The powertrain controller 116 may command the converters 115 and 130 to provide the driver demanded wheel torque and tractive force, respectively, via the electrified axle 190 and the propulsion sources 105 and 132. The inverters 115 and 130 may convert DC power from the battery 160 into AC power and supply AC power to the drive sources 105 and 132. The power sources 105 and 132 rotate and transmit torque / power to the transmission 135. The transmission 135 may transmit the torque from the drive sources 105 and 132 to the gears 106, and the gears 106 transmit the torque from the drive sources 105 and 132 to the rear wheels 103 via the axle shafts 190 aand 190 b.When the accelerator pedal is fully released, the vehicle control unit 152 may request low negative or regenerative power to gradually decelerate the vehicle 10 when the speed of the vehicle 10 is greater than a threshold speed. The requested regeneration power may be dependent on the driver pedal position, the state of charge of the battery (SOC), vehicle speed, and other conditions. When the driver demand pedal 140 is fully released and the vehicle speed is below a threshold, the vehicle control unit 152 may demand a low positive torque / power (e.g., drive torque) from the drive source 105, which may be referred to as creep torque or creep power. The creep torque or creep power may allow the vehicle 10 to remain stationary when the vehicle 10 is on a small grade.The human or autonomous driver may also request a negative or regenerative deceleration torque or alternatively deceleration power by actuating the caliper pedal 150 or providing a deceleration power request to the vehicle control unit 152. The vehicle control unit 152 may require, via the powertrain controller 116, a first portion of the driver demanded deceleration power to be generated via the propulsion source 105. Additionally, the vehicle control unit 152 may require a portion of the driver demanded deceleration power to be provided via the friction calipers 172 aand 172 bby instructing the friction caliper controller 170 to provide a second portion of the driver demanded deceleration power.After the vehicle control unit 152 determines the requested deceleration power, the vehicle control unit 152 may instruct control of the powertrain 116 to deliver the portion of the driver requested deceleration power assigned to the propulsion sources 105 and 132. The propulsion sources 105 and 132 may convert the vehicle's kinetic energy to alternating current.The powertrain controller 116 includes predetermined transmission shift schedules for selectively engaging and disengaging the gears of the fixed ratio transmission 135. The shift schedules stored in the powertrain controller 116 may select shift points or events depending on the driver demand wheel torque and vehicle speed.FIG. 2 shows a dash line representation of the vehicle drive system 199. In this example, vehicle propulsion system 199 includes a transmission 135 that is a two-ratio step-change transmission (e.g., a first lower and a second higher). In other examples, transmission 135 may include additional gear ratios.The transmission 135 is mechanically fixedly connected to the first electric machine 105 via the gearwheel 220. Additionally, the transmission 135 is mechanically fixed to the gear 223, but the gear 223 may be selectively mechanically coupled to the second electric machine 132 via the disconnect clutch 224. Specifically, the gear 223 is supported via the shaft 230 but is free to rotate with respect to the shaft 230 and the second electric machine 132 when the disconnect clutch 224 is disengaged. The gear 223 rotates with the shaft 230 and the second electric machine 132 when the disconnect clutch 224 is engaged. Thus, the second electric machine 132 may be mechanically coupled to the transmission 135 when the disconnect clutch 224 is closed. The second electric machine 132 may be mechanically decoupled from the transmission 135 when the disconnect clutch 224 is open.The vehicle propulsion system 199 also includes a mechanical power take-off 204 that may be mechanically connected to a device 202 located external to the vehicle propulsion system 199. In particular, the mechanical device 202 may consume mechanical energy from the auxiliary power take-off 204. Alternatively, the mechanical device 202 may power the power take-off 204. The auxiliary output 204 may be selectively coupled to the gear 222 via the auxiliary output disconnect clutch 206. Gear 222 meshes with gear 208, and gear 208 is mechanically coupled to shaft 230 and second electric machine 132.The auxiliary output 204 may be activated such that the mechanical device 202 rotates at a speed proportional to the rotational speed of the second electric machine 132. The auxiliary output may be activated by closing the auxiliary output disconnect clutch 206. The auxiliary output 204 may be activated while the disconnect clutch 224 is open or closed. When the disconnect clutch 224 is closed, the second electric machine 132 may rotate at a speed proportional to the rotational speed of the first electric machine 105. Thus, the second electric machine 132 may only deliver or receive mechanical power to / from the device 202, only to / from the transmission 135, or both to / from the transmission 135 and to the device 202. The transmission 135 is mechanically connected to the differential gear set 106 of FIG. 1 via the shaft 208.The system of FIGS. 1 and 2 provides an electric drive system comprising: a first electric machine; a second electric machine; a transmission, the transmission mechanically coupled to one or more rotatable wheels and the first electric machine; a disconnect clutch configured to selectively couple the second electric machine to the transmission; a power take-off configured to provide mechanical rotational energy to a device; a power take-off disconnect clutch configured to selectively couple the second electric machine to the power take-off; and one or more controllers, the one or more controllers including executable non-transitory instructions that cause the controller to operate the power take-off disconnect clutch and the disconnect clutch. In a first example, the electric drive system includes a power take-off disconnect clutch and a disconnect clutch that are actuated in response to a ratio between tractive force and vehicle speed. In a second example, which may include the first example, the electric drive system includes a transmission having a first gear and a second gear. In a third example, which may include one or both of the first and second examples, the electric drive system further includes additional executable instructions that cause the one or more controllers to engage the first gear and disengage the second gear in response to a first vehicle operating condition, and additional executable instructions that cause the one or more controllers to engage the second gear and disengage the first gear in response to a second vehicle operating condition. In a fourth example, which may include one or more of the first through third examples, the electric drive system further includes additional executable instructions that cause the one or more controllers to engage power take-off by closing the power take-off disconnect clutch and opening the disconnect clutch in response to a power take-off request and a tractive force request. In a fifth example, which may include one or more of the first through fourth examples, the electric drive system further includes additional executable instructions that cause the one or more controllers to decouple the auxiliary power output by opening the auxiliary power output disconnect clutch and closing the disconnect clutch in response to an auxiliary power output request and a tractive force request. In a sixth example, which may include one or more of the first through fifth examples, the electric drive system further includes additional executable instructions that cause the one or more controllers to fully open the disconnect clutch from a closed position in response to a vehicle speed exceeding a threshold speed. In a seventh example, which may include one or more of the first through sixth examples, the electric drive system further includes additional executable instructions that cause the one or more controllers to fully open the disconnect clutch from a closed position in response to a vehicle speed being below a threshold speed.The system of FIGS. 1 and 2 also provides an electric drive system comprising: a first electric machine; a second electric machine; a transmission, the transmission mechanically coupled to one or more rotatable wheels and the first electric machine; a disconnect clutch configured to selectively couple the second electric machine to the transmission; a power take-off configured to provide rotational mechanical energy to a device; a power take-off disconnect clutch configured to selectively couple the second electric machine to the power take-off; and one or more controllers, wherein the one or more controllers include executable, non-transitory instructions that cause the controller to open the disconnect clutch in response to an increasing driver demand torque when a vehicle speed is greater than a threshold speed, and additional executable instructions that cause the controller to open the disconnect clutch in response to an increasing driver demand torque when the vehicle speed is less than the threshold speed. In a first example, the electric drive system further comprises additional executable instructions that cause the controller to engage a first gear of the transmission in response to the tractive force and the vehicle speed. In a second example, which may include the first example, the electric drive system further comprises additional executable instructions that cause the controller to engage a second gear of the transmission in response to the tractive force and the vehicle speed. In a third example, which may include one or both of the first and second examples, the electric propulsion system further includes additional executable instructions indicating that the auxiliary power take-off is automatically disabled or automatically enabled. In a fourth example, which may include one or more of the first through third examples, the electric drive system further includes additional executable instructions indicating that the second electric machine is automatically deactivated or automatically activated.Referring now to FIG. 3, a graph 300 is shown showing the relationship between tractive force, vehicle speed, and powertrain operating mode. The diagram 300 includes a vertical and a horizontal axis. The vertical axis represents the traction force in the unit kilo-newtons (kN), the horizontal axis represents the vehicle speed in the unit kilometers per hour (km / h).In diagram 300, the operating range of the vehicle is formed from four operating ranges ( 302- 308). The first operating range 302 includes low vehicle speeds and relatively high tractive forces. In the first operating range 302, the auxiliary output is isolated from the second electric machine. Moreover, the first electric machine 105 and the second electric machine 132 are mechanically coupled to the gears of the transmission 135 so that they can both output energy to or receive energy from the transmission 135. Disconnect clutch 224 is fully closed and auxiliary output disconnect clutch 206 is fully open. The vehicle is in the first (e.g., low) gear. A vehicle may operate in the first operating range 302 when it temporarily locks, exits a striking hole, or begins to move a heavy load.The second operating range 304 includes low to medium vehicle speeds and low to medium traction forces. In the second operating range 304, auxiliary power take-off may be enabled and the first electric machine 105 is the only electric machine mechanically coupled to the gear of the transmission 135. The second electric machine 132 is mechanically decoupled from the gears of the transmission 135, so that the first electric machine 105 is the only drive source in this operating range. The auxiliary output disconnect clutch 206 is fully closed and the vehicle is in first (e.g., low) gear. A vehicle may move in the second operating region 304 as it approaches or moves away from an area where the auxiliary power take-off may be deployed (e.g., when raising a container or cargo area), where deployment of the auxiliary power take-off may be desirable. Thus, the auxiliary power take-off can be activated and in operation in the second operating range 304.The third operating range 306 includes medium to high vehicle speeds and low to medium traction forces. In the third operating range 306, the auxiliary power take-off is disconnected and the first electric machine 105 and the second electric machine 132 are mechanically coupled via gears of the transmission 135 such that both the first electric machine 105 and the second electric machine 132 can apply tractive force to the wheels of the vehicle. The auxiliary output disconnect clutch 206 is fully open and the disconnect clutch 224 is fully closed. The vehicle is in second (e.g., high) gear. A vehicle may be operated in the third operating region 306 when traveling at higher speeds, e.g., when traveling in a straight line or on a straight road.The fourth operating range 308 includes medium to high vehicle speeds and low tractive forces. In the fourth operating range 308, the auxiliary power take-off may be enabled and the first electric machine 105 is the only electric machine mechanically coupled to the gear of the transmission 135. The second electric machine 132 is mechanically decoupled from the gears of the transmission 135, so that the first electric machine 105 is the only drive source in this operating range. The auxiliary output disconnect clutch 206 is fully closed and the vehicle is in second (e.g., high) gear. A vehicle may be operated in the fourth operating range 308 when traveling in a straight line and some auxiliary power output is desired, e.g., when a mixer is operating onboard the vehicle and the vehicle is on the way to charge a mixture.FIG. 4 shows a block diagram of a method 400 for operating an electric vehicle with power take-off. The method of FIG. 4 may be integrated with and cooperate with the system of FIGS. 1 and 2. Further, at least portions of the method of FIG. 4 may be included as executable instructions in the non-transitory memory of one or more controllers, while other portions of the method may be executed via the one or more controllers that convert operating states of devices and actuators in the physical world. Block 406 represents a driving mode, and the driving mode includes modes 1-4.At 404, method 400 is in an operating state where the transmission of the vehicle is shifted to neutral or park. The vehicle may not move forward or backward when the transmission of the vehicle is shifted to neutral or park. The vehicle may be activated when in neutral or park.The method 400 may transition from block 404 to a shutdown operating state, as indicated by the operator 450, in response to a vehicle key being subtracted, a vehicle activation device being removed from the vehicle, or another signal indicating the desire or request to shut down or deactivate the vehicle, at block 402. The vehicle can be shut down by interrupting the power supply to the traction motors and converters of the vehicle. Method 400 continues with exiting the vehicle after being turned off. Alternatively, in response to a request for the transmission of the vehicle to transition to driving and a tractive effort request that is above a first threshold tractive effort, method 400 may proceed to block 412, as indicated by the guide post 454.At block 412, the vehicle enters a first operating mode in which the vehicle may be operated in a first operating range 302 as shown in FIG. 3. In the first operating mode, disconnect clutch 224 is fully closed and auxiliary output clutch 206 is fully open. This mode of operation enables the vehicle to operate at low speed and high tractive force. The vehicle may remain in first gear in this mode of operation. The method 400 may exit block 412 and proceed to block 408 in response to a power take-off request or a vehicle speed being greater than a first threshold speed of the vehicle.The method 400 may proceed from block 404 to block 408, as indicated by the control post 452 in response to a request for the transmission of the vehicle to transition to the driving mode, wherein the tractive effort request is below the first tractive effort threshold. At block 408, the vehicle enters a second operating mode in which the vehicle may be operated in a second operating range 304, as shown in FIG. 3. In the second operating mode, disconnect clutch 224 is fully open and auxiliary output clutch 206 may be fully closed when an auxiliary output request is present. This mode of operation allows the vehicle to operate at low speed with the power take-off enabled. The vehicle may remain in first gear in this mode of operation. Block 408 may also be input in response to a power take-off request while the vehicle is operating in the first operating mode or when the vehicle speed is greater than a first threshold speed, as indicated by the head post 458. Further, block 408 may also be input in response to a vehicle speed being below a second threshold speed when the vehicle is in block 410 and operating in a third mode as indicated by guide posts 468. Further, block 408 may be input in response to a vehicle speed being below a second threshold speed when the vehicle is in block 414 and operating in a fourth mode as indicated by guide posts 466.Method 400 may exit block 408 and proceed to block 412 in response to a driver requesting a tractive force (TE) greater than a threshold tractive force and a vehicle speed less than a vehicle speed, as indicated at baseline 456. Method 400 may be in first gear when method 400 is in blocks 408 and 412. Method 400 may also exit block 408 and proceed to block 410 in response to a vehicle speed being greater than a second threshold speed and no power take off request (PTO) as indicated at reference line 460. Method 400 may transition to a second gear when method 400 transitions to 410. Additionally, the method 400 may also exit block 408 and proceed to block 414 in response to a vehicle speed being greater than a second threshold speed and a power take off request (PTO) as indicated at reference line 464. Method 400 may transition to a second gear when method 400 proceeds to 414.At block 410, the vehicle enters a third operating mode in which the vehicle may be operated in a third operating range 306, as shown in FIG. 3. In the third operating mode, disconnect clutch 224 is fully closed and auxiliary output clutch 206 is fully open. In this mode of operation, the vehicle may be operated at higher speed and low to medium tractive effort without the auxiliary power being turned on. In this mode of operation, the vehicle may engage second gear. The method 400 may exit block 410 and proceed to block 414, as indicated by leader 462 in response to the request for power take off (PTO) being indicated as indicated by reference line 462. The method 400 may also exit block 410 and proceed to block 408, as indicated by reference line 468 in response to a vehicle speed being less than a second threshold speed.At block 414, the vehicle enters a fourth operating mode in which the vehicle may be operated in a fourth operating range 308 as shown in FIG. 3. In the fourth operating mode, disconnect clutch 224 is fully open and auxiliary output clutch 206 may be fully closed when an auxiliary output request is present. In this mode of operation, the vehicle may be operated at higher speeds with the auxiliary power output activated. In this mode of operation, the vehicle may engage second gear. Block 414 may be exited in response to no power take-off request being present, as indicated by reference line 461. Further, in response to a vehicle speed being below a second threshold speed, method 400 may exit block 414 and enter block 408, as indicated by reference line 466.In this way, a vehicle may be operated that includes two electric machines and a power take-off. The method of FIG. 4 allows the vehicle to transition operating mode so that both power take-off requirements and tractive effort requirements may be met.Method 400 provides for a method of operating a vehicle, comprising: selectively opening and closing a disconnect clutch and a power take-off disconnect clutch mechanically coupled to a second electric machine in response to a tractive force and a vehicle speed; and propelling the vehicle via a first electric machine. In a first example, the method includes where the disconnect clutch selectively couples the second electric machine to a transmission and the first electric machine, and where the first electric machine is mechanically coupled to the transmission. In a second example, which may include the first example, the method further comprises selectively engaging the power take-off clutch in response to a power take-off request. In a third example, which may include one or both of the first and second examples, the method further includes indicating disengagement of the auxiliary output clutch when the auxiliary output clutch is disengaged in response to vehicle speed. In a fourth example, which may include one or more of the first through third examples, the method further includes indicating engagement of the auxiliary output clutch when the auxiliary output clutch is engaged in response to vehicle speed. In a fifth example, which may include one or more of the first through fourth examples, the method further includes indicating disengagement of the disconnect clutch in response to vehicle speed. In a sixth example, which may include one or more of the first through fifth examples, the method further includes indicating engagement of the disconnect clutch in response to vehicle speed.Referring now to FIG. 5, a graph 500 is shown showing the relationship between the tractive force available while the transmission is engaged in the various gears and the vehicle speed. The diagram 500 includes a vertical and a horizontal axis. The vertical axis represents the traction force in the unit kilo-newtons (kN), the horizontal axis represents the vehicle speed in the unit kilometers per hour (km / h).Diagram 500 shows the maximum tractive force values which are available when the first or second gear wheel of the vehicle transmission is engaged. Specifically, dashed line 502 represents vehicle speeds and the maximum continuous tractive force available from the powertrain of FIGS. 1 and 2 while the vehicle is engaged in the first gear and a single electric machine is mechanically connected to the powertrain and wheels. Solid line 504 represents vehicle speeds and the maximum continuous tractive force available from the powertrain of FIGS. 1 and 2 when the vehicle is engaged with the second gear and a single electric machine is mechanically coupled to the powertrain to generate the tractive force at the wheels. Dashed line 506 represents vehicle speeds and maximum peak or transient tractive force available from the powertrain of FIGS. 1 and 2 when the vehicle is engaged with the first gear and a single electric machine is mechanically coupled to the powertrain to generate the tractive force at the wheels. Dashed line 508 represents vehicle speeds and maximum peak or transient tractive force available from the powertrain of FIGS. 1 and 2 when the vehicle is engaged in the second gear and a single electric machine is mechanically coupled to the powertrain to generate tractive force at the wheels.It can be seen from the lines in FIG. 5 that the transmission can be shifted from first to second gear when the vehicle speed exceeds a maximum achievable vehicle speed (dashed line 506). Additionally, the transmission may be shifted from second to first gear when the demanded tractive force exceeds the maximum tractive force achievable with dashed line 508.It should be appreciated that the example routines included herein may be used for control and estimation with various powertrain and / or vehicle system configurations. The control methods and routines disclosed herein may be stored as executable instructions in non-transitory memory and executed by the control system, including the controller, in combination with the various sensors, actuators, and other transmission and / or vehicle hardware. In addition, portions of the methods may be physical actions taken in the real world to change the state of a device. Thus, the described actions, operations, and / or functions may graphically represent code programmed into the non-transitory memory of the computer readable storage medium in the vehicle and / or transmission control system. The specific routines described herein may represent any one or more processing strategies such as event-driven, interrupt-driven, multi-tasking, multi-threading, and the like. Thus, the various actions, operations, and / or functions depicted may be performed in the order depicted, in parallel, or in some cases, without them. Accordingly, the order of processing is not necessarily required to achieve the features and advantages of the examples described herein, but is for convenience of illustration and description only. One or more of the illustrated actions, operations, and / or functions may be repeatedly performed depending on the strategy being used. One or more of the method steps described herein may also be omitted, if desired.While various embodiments have been described above, these are to be considered as examples and not as limitations. It will be apparent to those skilled in the art that the disclosed subject matter may be embodied in other specific forms without departing from the spirit of the subject matter. The above-described embodiments are therefore to be considered in all respects as illustrative and not restrictive. The configurations and routines disclosed herein are exemplary in nature and these specific examples are not to be considered in a limiting sense as numerous variations are possible. The above-mentioned technology can be used, for example, in electric and hybrid vehicles with induction and synchronous electric machines. The subject matter of the present disclosure includes all novel and non-obvious combinations and sub-combinations of the various systems and configurations, as well as other features, functions, and / or characteristics disclosed herein.The following claims particularly emphasize certain combinations and sub-combinations that are considered novel and not obvious. These claims may refer to "a" element or "a first" element or the equivalent thereof. Such claims are to be understood to include inclusion of one or more such elements, with two or more such elements not being required or excluded. Other combinations and sub-combinations of the disclosed features, functions, elements, and / or characteristics may be claimed by altering the present claims or by filing novel claims in this or a related application. Such claims, whether broader, narrower, equal or different in scope than the original claims, are also considered to be included within the subject matter of the present disclosure.

Claims

An electric drive system comprising: a first electric machine; a second electric machine; a transmission, the transmission mechanically coupled to one or more rotatable wheels and the first electric machine; a disconnect clutch configured to selectively couple the second electric machine to the transmission; a power take-off configured to provide rotational mechanical energy to a device; a power take-off disconnect clutch configured to selectively couple the second electric machine to the power take-off; and one or more controllers, the one or more controllers including executable non-transitory instructions that cause the one or more controllers to actuate the power take-off disconnect clutch and the disconnect clutch.The electric drive system of claim 1, wherein the power take-off disconnect clutch and the disconnect clutch are actuated in response to a ratio between tractive force and vehicle speed.The electric drive system of claim 2, wherein the transmission includes a first gear and a second gear.The electric drive system of claim 3, further comprising additional executable instructions that cause the one or more controllers to engage the first gear and disengage the second gear in response to a first vehicle operating condition, and additional executable instructions that cause the one or more controllers to engage the second gear and disengage the first gear in response to a second vehicle operating condition.The electric drive system of claim 4, further comprising additional executable instructions that cause the one or more controllers to engage the auxiliary power via closing the auxiliary power disconnect clutch and opening the disconnect clutch in response to an auxiliary power output request and a tractive force request.The electric drive system of claim 4 or 5, further comprising additional executable instructions that cause the one or more controllers to disengage the auxiliary power output by opening the auxiliary power output disconnect clutch and closing the disconnect clutch in response to an auxiliary power output request and a tractive force request.The electric drive system of any preceding claim, further comprising additional executable instructions that cause the one or more controllers to fully open the disconnect clutch from a closed position in response to a vehicle speed exceeding a threshold speed.The electric drive system of any preceding claim, further comprising additional executable instructions that cause the one or more controllers to fully open the disconnect clutch from a closed position in response to a vehicle speed being below a threshold speed.An electric drive system comprising: a first electric machine; a second electric machine; a transmission, the transmission mechanically coupled to one or more rotatable wheels and the first electric machine; a disconnect clutch configured to selectively couple the second electric machine to the transmission; a power take-off configured to provide rotational mechanical energy to a device; a power take-off disconnect clutch configured to selectively couple the second electric machine to the power take-off; and one or more controllers, wherein the one or more controllers include executable, non-transitory instructions that cause the one or more controllers to open the disconnect clutch in response to an increasing driver demand torque when a vehicle speed is greater than a threshold speed, and additional executable instructions that cause the one or more controllers to open the disconnect clutch in response to an increasing driver demand torque when the vehicle speed is less than the threshold speed.The electric drive system of claim 9, further comprising additional executable instructions that cause the one or more controllers to engage a first gear of the transmission depending on the tractive force and the vehicle speed.The electric drive system of claim 10, further comprising additional executable instructions that cause the one or more controllers to engage a second gear of the transmission depending on the tractive force and the vehicle speed.The electric propulsion system of any of claims 9 to 11, further comprising additional executable instructions indicating that the power take-off is automatically disabled or automatically enabled.The electric propulsion system of any of claims 9 to 12, further comprising additional executable instructions indicating that the second electric machine is automatically deactivated or automatically activated.

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