Active loss generation using a disengaged engine

Abstract

A power module includes inverter switches configured to control the current supply to multiple stator coils of a motor. A control module of the power module is configured to direct a quantity of current to the motor through the inverter switches according to a current command, while one rotor of the motor is essentially held stationary. For example, the control module may be configured to generate a ripple torque command that alternates between positive and negative over a predefined period. The control module further generates a feedback torque command according to a feedback rotor speed to drive the rotor speed toward zero. The feedback torque command can be combined with the ripple torque command to produce a total torque command.

Description

RELATED REGISTRATION

[0001] This application claims priority over the preliminary US patent application with serial number 63 / 688,802, filed on August 29, 2024, entitled ACTIVE LOSS GENERATION USING DISENGAGED MOTOR. INTRODUCTION

[0002] The present disclosure relates to the active generation of losses using a disengaged motor. SUMMARY

[0003] The present disclosure describes an approach for inducing losses in a disengaged motor. In one aspect, inverter switches are configured to regulate the current supply to a plurality of stator coils of a motor. A control module is configured to cause the inverter switches to supply a specified amount of current to the motor according to a current command, while the motor rotor is essentially held stationary. For example, the control module can be configured to generate a ripple torque command that alternates between positive and negative over a predefined period. BRIEF DESCRIPTION OF THE DRAWINGS Fig. Figure 1A illustrates an exemplary vehicle that can be operated according to certain embodiments. Fig. Figure 1B illustrates a vehicle chassis with multiple drive units that can be operated according to certain embodiments. Fig. Figure 2 is a schematic block diagram of components for operating the vehicle according to certain embodiments. Fig. Figure 3 is a schematic block diagram illustrating a power module of a vehicle according to certain embodiments. Fig. Figure 4 is a schematic block diagram of components of a drive unit according to certain embodiments. Fig. Figure 5 is a schematic block diagram illustrating the distribution of recuperative current according to certain embodiments. Fig. Figure 6 is a schematic block diagram of components for controlling the current supplied to a disengaged motor in order to achieve active loss generation according to certain embodiments. DETAILED DESCRIPTION

[0004] A vehicle incorporates multiple motors, one of which can be disengaged when not in use. The disengaged motor can still be used to generate active losses, such as absorbing regenerative power when the battery cannot absorb it, and generating heat to condition the battery. A power module for controlling the current supply to the disengaged motor generates a ripple torque command that alternates between positive and negative over a predefined period. A total torque command can be obtained by adding the ripple torque command to a feedback torque command based on a detected motor speed, with the feedback torque command being selected to control the motor speed towards zero. The total torque command and a current command are used to control the inverter switches that supply power to the motor.The current command is a quantity of current to be received by the disengaged motor in order to absorb recuperative current and / or generate heat.

[0005] Fig. Figure 1A illustrates an exemplary vehicle 100 in which the approach described herein can be implemented. As in Fig. As can be seen in Figure 1A, the vehicle 100 has several external cameras 102 and one or more front displays 104. Each of these external cameras 102 can capture a particular view or perspective of the exterior of the vehicle 100. The images or videos captured by the external cameras 102 can then be displayed on one or more displays in the vehicle 100, for example, the one or more front displays 104, for viewing by a driver.

[0006] How Fig. As can be seen from 1B, the vehicle 100 can include a chassis 106 which includes a frame 108 that provides a primary structural element of the vehicle 100. The frame 108 can be formed from one or more struts or other structural elements, or it can be integral with the body of the vehicle (e.g., unibody construction).

[0007] In embodiments where the vehicle 100 is a battery electric vehicle (BEV) or possibly a hybrid vehicle, a large battery 110 is mounted on the chassis 106 and can occupy a considerable area within the frame 108 (e.g., at least 80 percent of it). For example, the battery 110 can store between 100 and 200 kilowatt-hours (kWh). The battery 110 can be a lithium-ion battery or another type of rechargeable battery. The battery can essentially have a planar shape.

[0008] The power of the battery 110 can be supplied to one or more drive units 112. Each drive unit 112 can consist of an electric motor and possibly a gear train that provides a reduction gear. In some embodiments, there is a single drive unit 112 that drives either the front wheels or the rear wheels of the vehicle 100. In another embodiment, there are two drive units 112, each driving either the front wheels or the rear wheels of the vehicle 100. In yet another embodiment, there are four drive units 112, each driving one of the four wheels of the vehicle 100.

[0009] The drive units 112 can be powered by one or more power modules 114 from the battery 110, for example, by one power module for each drive unit 112 or for each pair of drive units 112. The power module 114 can include inverters configured to convert direct current (DC) from the battery 110 into alternating current (AC), which is supplied to the motors of the drive units 112. The power module 114 also enables the motors of the drive units to operate as generators to provide regenerative braking. Furthermore, the power module 114 enables the transfer of the regenerative power to the battery 110.

[0010] The drive units 112 are connected to two or more hubs 116, to which wheels can be mounted. Each hub 116 includes a corresponding brake 118, such as the illustrated disc brakes. Each hub 116 is further connected to the frame 108 via a suspension 120. The suspension 120 may include metal or air springs for shock absorption. The suspension 120 may be designed as a pneumatic or hydraulic suspension, allowing the ride height of the chassis 106 relative to a support surface to be adjusted. The suspension 120 may include a damper, the damper's characteristics being either fixed or electronically adjustable.

[0011] In the embodiment of Fig. In 1B and in the discussion below, vehicle 100 is a battery-powered electric vehicle. However, a hybrid electric vehicle can also benefit from the approach described herein. Likewise, applications outside of vehicles that use an inverter or other relevant power component can also benefit from the approach described herein.

[0012] Fig. Figure 2 illustrates exemplary components of vehicle 100. Fig. 1A. As in Fig. As shown in Figure 2, the vehicle 100 includes the cameras 102, one or more front displays 104, a user interface 200, one or more sensors 202, a motion sensor 204, and a tracking system 206. The one or more sensors 202 may include ultrasonic sensors, radio detection and range measurement sensors (RADAR sensors), light detection and range measurement sensors (LIDAR sensors), or other sensor types. The tracking system 206 may be implemented as a GPS receiver (Global Positioning System receiver). The user interface 200 allows a user, such as a driver or passenger in the vehicle 100, to provide input.

[0013] The components of the vehicle 100 may include one or more temperature sensors 208. The temperature sensors 208 may include sensors configured to detect ambient air temperature, battery 110 temperature, a power module 114 temperature, each drive unit 112 temperature and / or each motor of each drive unit 112 temperature, the temperature of the coolant entering or leaving a cooling system, the oil temperature in a drive unit 112 temperature, or the temperature of any other component of the vehicle 100. The temperature sensors 208 may include a temperature sensor mounted directly on a microprocessor of the power module 114, as described in more detail below.

[0014] A control system 214 executes instructions to perform at least some of the actions or functions of the vehicle 100. For example, the control system 214, as shown in Fig. 2 shown, including one or more electronic control units (ECUs) configured to perform at least some of the actions or functions of the vehicle 100, including those relating to the Fig. The functions described in sections 3 to 6. In certain embodiments, each ECU is responsible for a specific group of functions.

[0015] Certain features of the embodiments described herein may be controlled by a telematics control module ECU (TCM-ECU). The TCM-ECU may provide a wireless vehicle communication gateway to support functions such as, but not limited to, over-the-air (OTA) software updates, vehicle-to-the-Internet communication, vehicle-to-a-computer communication, on-board navigation, vehicle-to-vehicle communication, vehicle-to-landscape feature communication (e.g., automated toll road sensors, automated toll plazas, power delivery devices at charging stations), or automated calling functionality.

[0016] Certain features of the embodiments described herein can be controlled by a central gateway module ECU (CGM-ECU). The CGM-ECU can serve as the vehicle's communication hub, connecting and transmitting data to and from the various ECUs, sensors, cameras, microphones, motors, displays, and other vehicle components. The CGM-ECU can include a network switch that provides connectivity via Controller Area Network (CAN) ports, Local Interconnect Network (LIN) ports, and Ethernet ports. The CGM-ECU can also act as the master controller over the various vehicle modes (e.g., road mode, park mode, off-road mode, towing mode, camping mode) and thereby control certain vehicle components related to switching the vehicle into one of the vehicle modes.

[0017] In various configurations, the CGM-ECU collects sensor signals from one or more sensors of the vehicle 100. For example, the CGM-ECU can collect data from cameras 102, sensors 202, motion sensors 204, positioning systems 206, and temperature sensors 208. The sensor signals acquired by the CGM-ECU are then transmitted to the corresponding ECUs for processing.

[0018] The control system 214 may also include one or more additional ECUs, such as, for example and without limitation: a Vehicle Dynamics Module ECU (VDM ECU), an Experience Management Module ECU (XMM ECU), a Vehicle Access System ECU (VAS ECU), a Near Field Communication ECU (NFC ECU), a Body Control Module ECU (BCM ECU), a Seat Control Module ECU (SCM ECU), a Door Control Module ECU (DCM ECU), a Rear Zone Control ECU (RZC ECU), an Autonomy Control Module ECU (ACM ECU), an Autonomous Safety Module ECU (ASM ECU), a Driver Monitoring System ECU (DMS ECU) and / or a Winch Control Module ECU (WCM ECU).

[0019] If the vehicle 100 is an electric vehicle, one or more ECUs can provide functions related to the vehicle's battery pack, such as a battery management system ECU (BMS-ECU), a battery power isolation ECU (BPI-ECU), a balancing voltage temperature ECU (BVT-ECU), and / or a thermal management module ECU (TMM-ECU). In various configurations, the XMM-ECU transmits data to the TCM-ECU (e.g., via Ethernet, etc.). Additionally or alternatively, the XMM-ECU can transmit other data (e.g., audio data from microphones 216, etc.) to the TCM-ECU.

[0020] How Fig. As can be seen from Figure 3, the power module 114 can be contained in a housing 300, such as an aluminum or steel housing. The power module 114 can include a variety of components configured to convert direct current (DC) from the battery 110 into alternating current (AC), such as three-phase AC, which is supplied to one or more motors 302 of the drive unit 112, including the power module 114.

[0021] The power module 114 can receive power from the battery 110 via an intermediate circuit capacitor 304, which is coupled to the positive and negative terminals (Batt+, Batt-) of the battery 110 and serves to smooth the current received from the battery 110 as part of the process by which the direct current from the battery 110 is converted into an approximately sinusoidal alternating current. The intermediate circuit capacitor 304 can also serve to dampen any voltage spikes. The intermediate circuit capacitor 304 can be located inside or outside the housing 300.

[0022] The power module 114 can include inverter switches 306, which are coupled to the outputs of the DC link capacitor 304. The inverter switches 306 can include a variety of switches that are selectively opened and closed to transmit current to the outputs of the power module 114 at a suitable frequency to drive one or more motors 302. For example, the inverter switches 306 can output three-phase current via lines 308 that connect the inverter switches 306 to the motor 302. The opening and closing of the switches of the inverter switches 306 can be controlled by a control module 310. The control module 310 can include a circuit board with various electronic components configured to generate the control signals for the inverter switches 306.In some embodiments, the power module 114 drives two drive units 112 and has separate circuit boards for supplying power to the motors 302 of the separate drive units.

[0023] The control module 310 can further comprise a microprocessor 312, which is programmed to control the operation of the control module 310 and thus the inverter switch 306. The microprocessor 312 can be implemented as a silicon chip mounted on the circuit board of the control module 310. The microprocessor 312 can include a temperature sensor 314 mounted directly to it.

[0024] The control module 310 can be coupled to the control system 214 and implement instructions from the control system 214 to control the current supplied to the motor 302 and to cause the motor 302 to generate regenerative power. The control system 214 can generate such instructions as part of an automated driving algorithm (e.g., automatic cruise control), a safety algorithm (e.g., traction control, stability control, automated emergency braking), or in response to input from a driver via an accelerator pedal 316 and / or a brake pedal 318.

[0025] The motor 302 can include a rotor 322a and stator coils 322b. The stator coils 322b include wire loops through which current flows to induce stator magnetic fields that act on the rotor 322a. The rotor 322a includes either (a) permanent magnets, on which the stator magnetic fields act to induce a torque on the shaft 322c of the motor 302, or (b) conductive rods in which current is induced by the stator magnetic fields, thereby generating a corresponding rotor magnetic field that interacts with the stator magnetic fields to induce a torque on the shaft 322c.

[0026] If the rotor 322a includes permanent magnets, the rotation of the rotor 322a, when the motor 302 is not in use, induces currents in the stator coils 322b and corresponding magnetic fields that oppose the rotation of the rotor 322a. Therefore, it is advantageous to disconnect the shaft 322c from the wheels of the vehicle 100 when the motor 302 is not in use.

[0027] For example, with reference to Fig. 4. The drive unit 112 can include a disconnector 400 arranged between the motor 302 and the drive gears 402. The drive gears 402 transmit torque to an axle 404, which is coupled to one or more wheels of the vehicle 100. A vehicle dynamics module (VDM) 406 of the control system 214 is configured to control the power supply to the motor 302 and to control the state of the disconnector 400, i.e., to connect the motor 302 to the drive gears 402 or to disconnect the motor 302 from the drive gears 402. The disconnector 400 can also be arranged between the drive gears 402 and the axle 404 or between the axle 404 and one or more wheels of the vehicle 100.

[0028] With reference to Fig. 5. The vehicle 100 can be operated in the illustrated configuration in which one motor 302a is engaged, e.g., coupled to one or more of the first wheels of the vehicle 100, and another motor 302b is disengaged, e.g., not coupled to one or more of the second wheels of the vehicle 100. This configuration can be useful if the torque of both motors 302a and 302b is not required to achieve a target speed of the vehicle 100, or if the vehicle 100 is operated in an energy-saving mode.

[0029] The drive unit 112, including the motor 302a, can be configured such that the motor 302a is always engaged. In one example, the motor 302a is engaged with the two front wheels of the vehicle 100, and the motor 302b is selectively engaged with the two rear wheels of the vehicle 100. In some embodiments, the engaged motor 302a can be an induction motor, while the disengaged motor 302b is a permanent magnet motor.

[0030] The motors 302a, 302b can be coupled to the battery 110 to send regenerative current to the battery 110 or to receive current from the battery 110. In the illustrated embodiments, the motors 302a, 302b are coupled to the battery 110 via a capacitor 500, such as a high-voltage direct current (HVDC) capacitor. The HVDC capacitor 500 can be a single capacitor to which both motors 302a, 302b are connected, or there can be separate HVDC capacitors 500 for each motor 302a, 302b (e.g., the DC link capacitor 304 of each drive unit 112).

[0031] During normal driving, the engaged motor 302a can periodically generate recuperative current, such as during regenerative braking. In some scenarios, the battery 110 is unable to absorb the recuperative current or the full amount of it. This can occur when the battery 110 has reached or is nearing full state of charge (SOC), or when the battery temperature is too low or too high to accept current without damaging the battery 110. It may be desirable to maintain the amount of recuperative current higher than the capacity of the battery 110 to provide a constant stopping force regardless of the battery 110's state of charge (e.g., a constant stopping force with a force applied to the brake pedal 318).

[0032] In such a scenario, the disengaged motor 302b can be operated in a lossy manner to convert the electricity into heat. The heat can be dissipated by a coolant circulating through a cooling system 502. The coolant can circulate in thermal contact with the motors 302a, 302b, and the battery 110. The cooling system 502 can include a radiator for heat exchange with the ambient air and possibly a radiator that is part of a vapor compression cooling system.

[0033] In another scenario, battery 110 is below a desired temperature, either for supplying power to the engaged motor 302a or for receiving power during charging. In this scenario, the disengaged motor 302b can also be operated in a lossy manner to convert the power into heat, which is then transferred from the cooling system 502 to battery 110.

[0034] When using the approach described herein, the disengaged motor 302b is operated in a lossy manner, while the rotor 322a is held essentially stationary, e.g., within a position range of 1, 0.1, or 0.01 degrees. Operating the disengaged motor 302b in this way facilitates, when necessary, the re-engagement of the motor 302b by the VDM 406 using the isolator 400. For example, the VDM 406 can assume that the rotor 322a is not rotating (e.g., at a speed of less than 10, 5, or 1 revolution per minute (rpm)) and / or is within a tolerance (e.g., 5, 1, or 0.1 degrees) of a known position when the motor 302b is re-engaged.

[0035] Fig.Figure 6 illustrates an exemplary control architecture 600 for operating the disengaged motor 302b in a lossy manner in one of the scenarios described above. The illustrated control architecture 600 can be implemented by a power module 114, such as the control module 310, wherein the power module 114 is part of a drive unit 112 that includes the disengaged motor 302b, and wherein the inverter switches 306 are also used as described below. The control architecture 600 can implement commands that it receives from the control system 214, such as a command to consume a certain amount of current while the motor 302b of the drive unit 112 is essentially held stationary, as defined above.

[0036] The control architecture 600 can generally be described as commanding an alternating torque (“ripple torque”) and a zero speed for the disengaged motor 302b, while simultaneously commanding a current draw equal to the amount of current required to (a) consume excess recuperative current that cannot be absorbed by the battery 110, and / or (b) generate heat to condition the battery 110.

[0037] For example, a ripple torque command 602 can alternately apply positive and negative torques over a predefined period. The ripple torque command 602 can be generated by the control module 310 itself. The durations of the positive and negative torque periods can be substantially equal (within the tolerances achievable by the components used, e.g., within 2% equality) and together constitute 100% of the duration of the ripple torque command 602, e.g., a 50% duty cycle for positive torque interleaved with a 50% duty cycle for negative torque. The magnitudes of the positive torque and negative torque periods can also be substantially equal (e.g., within the tolerances achievable by the components used, e.g., within 2% equality).

[0038] The magnitude and duration of the periods with positive torque and the periods with negative torque can be based on a frequency response of the motor 302. For example, the magnitude and duration can be selected such that when the torque of the motor 302 is controlled solely according to the ripple torque command 602, the motor 302 experiences oscillations with a magnitude of less than 1 degree, 0.5 degrees, 0.1 degrees, or 0.01 degrees. In one example, the magnitude is selected to be between 20 newton-meters (Nm) and 1 Nm, between 10 Nm and 1 Nm, or between 5 Nm and 1 Nm. The duration of each positive and negative period can be selected to be less than 100 milliseconds, 10 milliseconds, or 1 millisecond. In some embodiments, the duration is selected based on the switching speed of the components used, e.g., the switching speed of the inverter switches 306 or a multiple thereof (e.g.,less than 4, 2, or a smaller multiple thereof). The duration can be chosen based on the maximum rotational speed of the motor 302b, e.g., a limit specified by components that control the rotational speed of the motor 302b. For example, the duration can be 1 / (M*R), where R is the maximum rotational speed in revolutions per second and M is a multiple such as a value greater than 1, greater than 2, greater than 10, or greater than 100. In some embodiments, for example, the duration of the predefined period of the ripple current can be less than 1 / M, where M is the maximum rotational speed of the motor in revolutions per second.

[0039] In some embodiments, speed feedback is used in conjunction with the ripple torque command 602 to compensate for inaccuracies in the generation and / or implementation of the torque command and to prevent the motor 302 from starting to rotate. For example, a motor speed feedback signal 606 and a zero speed command 608 can be input into a feedback controller 604, such as a proportional-integral differential controller (PID controller). The feedback controller 604 selects a feedback torque command according to a transfer function that regulates the motor speed feedback signal 606 towards zero over time. When the disengaged motor 302b is engaged, the zero speed command 608 can be replaced by a speed command from the control system 214, which may be based on input from the user (e.g., position of the accelerator pedal 316) or an automated system (e.g., a speed sensor).Cruise control or another automated driving system).

[0040] The feedback torque command issued by the feedback controller 604 can then be combined with the ripple torque command 602, for example by summing the ripple torque command 602 and the feedback torque command in a summing stage 610 to obtain a total torque command. Using the ripple torque command 602 together with speed feedback can help prevent rotor 302c from spinning freely during a delay in the implementation of the speed feedback, such as transmission delays or the finite frequency response of the feedback controller 604.

[0041] A desired loss amount can be determined from a DC command 612 and an HVDC voltage 614. The DC command 612 is the amount of recuperative current currently generated in excess of the current-absorbing capacity of battery 110, or is dependent on this. The DC command 612 can additionally or alternatively be dependent on the required amount of heating of battery 110, e.g., a value obtained based on a detected temperature of battery 110, such as by a temperature feedback controller. The HVDC voltage 614 can be a detected value of the voltage at the output of battery 110 (e.g., Batt+) or at the input terminals of the disengaged motor 302b.

[0042] The DC command 612 and the HVDC voltage 614 can be multiplied together as by the multiplier stage 616 to obtain a power command, e.g. the amount of power that the disengaged motor 302b is to consume.

[0043] The power command can be input into a motor controller 618, which outputs a corresponding input current command. For example, the motor controller 618 can be a controller used to convert a commanded power quantity (e.g., according to a position of the accelerator pedal 316) into a current demand. The motor controller 618 can be implemented using a lookup table or another control algorithm. In other embodiments, the DC command 612 is used as the input current command, bypassing the motor controller 618. Using the motor controller 618 has the advantage of utilizing an existing programmable component of the control module 310. However, in other embodiments, another component can implement the functions attributed herein to the motor controller 618, which relate to generating losses while the motor 302 is essentially kept stationary, as defined above.For example, instead of the motor controller 618, a separate control module can be used within the control module 310, the power module 114 or the control system 214.

[0044] The total torque command and the input current command can be input into a vector current stage 620. The vector current stage 620 determines the timing and amount of current applied to each coil of the stator coils 322b, according to the total torque command and the input current command. The output of the vector current stage 620 can therefore be a signal for each stator coil 322b, with each signal specifying a time-varying current target for that stator coil 322b. The vector current stage 620 can be implemented as any vector current controller known in engineering (e.g., a direct quadrature controller (DQ controller)).

[0045] The output signals of the vector current stage 620 can be fed into a current controller 622, which controls switches that supply current to the stator coils 322b in order to achieve the current targets specified in the output signals within the limits of the current controller 622. The current controller 622 can be implemented as an inverter switch 306 or as another component of the power module 114.

[0046] The feedback controller, based on the motor speed feedback signal 606 together with the ripple torque command 602, ensures that the rotor 302c remains essentially stationary. The control of the motor controller 618 according to the DC command 612 ensures that the current drawn by the motor 302 (e.g., RMS current) substantially corresponds to the DC command 612 (e.g., is within 10, 5, or 1 percent of it).

[0047] As can be seen, the control architecture 600 allows a specific current draw by the disengaged motor 302b while simultaneously performing a feedback control to prevent the rotation of the rotor 302c. The control architecture 600 can achieve this with only one input from the VDM 406 of the control system 214: the DC command 612. The control architecture 600 itself can be implemented within the control module 310 or by another component within the power module 114 that is separate from the control system 214. For example, the control module 310 can implement the control architecture 600 in response to receiving the DC command 612 while the motor 302b is disengaged.

[0048] Using the approach described above, the disengaged motor 302b can, for example, provide an additional 10 Nm of regenerative braking or generate 10 kilowatts of heat for battery conditioning. The approach described above may be limited by a temperature limit of the disengaged motor 302b. For example, if a temperature sensor indicates that the temperature of the disengaged motor 302b is above a threshold, the control module 310 can notify the VDM, which can then reduce the DC command 612 in response to the notification. The VDM can take other actions in response to the notification, such as reducing regenerative braking, increasing friction braking, or drawing heat from another source to condition the battery (e.g., a resistance heater).

[0049] The descriptions of the various embodiments of this disclosure are presented for illustrative purposes. Many modifications and variations will be apparent to the person skilled in the art without affecting the scope of protection or the spirit of the described embodiments. The terminology used herein has been chosen to explain the principles of the embodiments, their practical application, or the technical improvement over technologies available on the market, or to enable other persons skilled in the art to understand the embodiments disclosed herein.

[0050] The foregoing refers to the embodiments presented in this disclosure. However, the scope of this disclosure may extend beyond the specifically described embodiments. Instead, any combination of features and elements, regardless of whether they relate to different embodiments, is considered for implementing and practicing the presented embodiments. Furthermore, while the embodiments disclosed herein may have advantages over other possible solutions or over the prior art, the embodiments may have some advantages or no particular advantage at all. Therefore, the considerations, features, embodiments, and advantages discussed herein are merely illustrative.

[0051] While the foregoing relates to embodiments of the present disclosure, other and further embodiments may be elaborated without deviating from the basic scope of protection, and the scope of protection is determined by the following claims. QUOTES INCLUDED IN THE DESCRIPTION

[0000] This list of documents cited by the applicant was automatically generated and is included solely for the reader's convenience. The list is not part of the German patent or utility model application. The DPMA accepts no liability for any errors or omissions. Cited patent literature

[0000] US 63 / 688,802

[0001]

Claims

[1] Performance module, comprising: Inverter switches configured to regulate the power supply to a plurality of stator coils of a motor; and a control module configured to cause the inverter switches to supply a quantity of current to the motor in accordance with a current command and a torque command, in order to substantially hold a rotor of the motor stationary, wherein the torque command includes a ripple torque command that alternates between positive and negative over a predefined period. [2] Power module according to claim 1, wherein the predetermined period is less than 10 milliseconds. [3] Power module according to claim 1, wherein the torque command includes a feedback torque command and the control module is further configured to: Receiving a speed feedback signal that indicates the speed of the motor; Generating the feedback torque command, which regulates the motor speed towards zero; Combining the ripple torque command and the feedback torque command to obtain the torque command; and Controlling the inverter switches based on the torque command. [4] Power module according to claim 3, wherein the control module is further configured to generate the feedback torque command according to the speed feedback signal using a proportional integrator differential feedback controller. [5] Power module according to claim 3, wherein the control module is further configured to control the inverter switches according to the current command and the torque command, such that the amount of current drawn by the motor substantially corresponds to the current command, while the rotor of the motor is substantially held stationary. [6] Power module according to claim 3, wherein the control module is further configured to control the inverter switches according to the current command and the torque command such that the current quantity is within 10 percent of the current command, while maintaining the movement of a rotor of the motor within a position range of 1 degree. [7] Power module according to claim 3, wherein the control module is further configured to: Determining an input current according to the current command and a voltage of a battery coupled to the power module; and Generating a vector current according to the torque command and the input current, wherein the vector current defines a time and an amount of current to be applied to each stator coil of the plurality of stator coils using the inverter switches. [8] Vehicle, comprising: a large number of wheels; an engine; a separator configured to selectively engage the motor with one or more of the first wheels of the plurality of wheels; a power module configured to control the motor; and a control system configured to: Instructing the separator to disengage the engine from one or more first wheels; and While the motor is disengaged from one or more first wheels, a current command is sent to the power module; wherein the power module is configured to supply a quantity of current to the motor in accordance with the current command, while one rotor of the motor is essentially held stationary. [9] Vehicle according to claim 8, wherein: the engine is a first engine, the vehicle further comprising a second engine coupled to one or more second wheels of the plurality of wheels; and the control system is configured to determine the current command according to the amount of recuperative current generated by the second motor. [10] Vehicle according to claim 9, further comprising a battery; the control system is configured to determine the current command according to the amount of recuperative current generated by the second motor and the current absorption capacity of the battery. [11] Vehicle according to claim 10, wherein the control system is configured to determine the current-accepting capacity of the battery according to a state of charge and temperature of the battery. [12] Vehicle according to claim 8, further comprising a battery and a cooling system connected to the battery and the engine; the control system is configured to determine the current command according to the battery temperature. [13] Vehicle according to claim 12, wherein the cooling system is configured to circulate coolant in thermal contact with the battery and the engine. [14] Vehicle according to claim 8, wherein the power module further comprises inverter switches, wherein the power module is further configured to generate a ripple torque command that alternates between positive and negative over a predefined period. [15] Vehicle according to claim 14, wherein the predefined period is less than 10 milliseconds. [16] Vehicle according to claim 14, wherein the power module is further configured to: Receiving a speed feedback signal that indicates the speed of the motor; Generating a feedback torque command designed to control the motor speed towards zero; Combining the ripple torque command and the feedback torque command to obtain the overall torque command; and Controlling the inverter switches based on the total torque command. [17] Vehicle according to claim 16, wherein the power module is configured to generate the feedback torque command according to the speed feedback signal using a proportional integrator differential feedback controller. [18] Vehicle according to claim 16, wherein the power module is further configured to control the inverter switches according to the current command and the total torque command such that the current quantity substantially corresponds to the current command while the rotor of the motor is substantially held stationary. [19] Vehicle according to claim 16, wherein the power module is further configured to control the inverter switches according to the current command and the total torque command, such that the current quantity is within 10 percent of the current command, while maintaining the movement of a rotor of the motor within a position range of 1 degree. [20] Vehicle according to claim 16, wherein the power module is further configured to: Determining an input current according to the current command and a voltage of a battery coupled to the power module; and Generating a vector current according to the torque command and the input current, wherein the vector current defines a time and amount of current to be applied to each stator coil of the motor using the inverter switches.

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