Manual torque vectoring

A vehicle includes an axle having left and right wheels. The vehicle further includes left and right torque-vector control devices each having an actuator with a released position, a fully actuated position, and a plurality of intermediate positions. A vehicle controller is programmed to, in response to the vehicle turning and one of the actuators being actuated, command different torques to the left and right wheels to produce torque vectoring between the wheels, wherein a difference between the torques commanded to the wheels increases as the actuator moves toward the fully actuated position and decreases as the actuator moves toward the fully released position.

TECHNICAL FIELD

The present disclosure relates to torque vectoring and more particularly to manually engaging torque vectoring.

BACKGROUND

Vehicles such as fully electric vehicles and hybrid-electric vehicles contain a traction-battery assembly to act as an energy source for the vehicle. The traction battery may include components and systems to assist in managing vehicle performance and operations. The traction battery may also include high-voltage components, and an air or liquid thermal-management system to control the temperature of the battery. The traction battery is electrically connected to an electric machine that provides torque to driven wheels. Electric machines typically include a stator and a rotor that cooperate to convert electrical energy into mechanical motion or vice versa.

SUMMARY

According to one embodiment, a vehicle includes an axle having left and right wheels, a steering wheel, left and right driver-actuatable inputs operable to request left-side and right-side torque vectoring, and a controller. The controller is programmed to, in response to the steering wheel being turned left and a driver requesting left-side torque vectoring via the left input, (i) calculate a first torque differential between the left and right wheels based on steering angle, accelerator-pedal position, vehicle speed, and yaw rate, and (ii) command torque to the left and right wheels based on the first torque differential. The controller is further programmed to, in response to the steering wheel being turned right and the driver requesting right-side torque vectoring via the right input, (i) calculating a second torque differential between the left and right wheels based on steering angle, accelerator-pedal position, vehicle speed, and yaw rate, and (ii) command torque to the left and right wheels based on the second torque differential.

According to another embodiment, a vehicle includes an axle having left and right wheels. The vehicle further includes left and right torque-vector control devices each having an actuator with a released position, a fully actuated position, and a plurality of intermediate positions. A vehicle controller is programmed to, in response to the vehicle turning and one of the actuators being actuated, command different torques to the left and right wheels to produce torque vectoring between the wheels, wherein a difference between the torques commanded to the wheels increases as the actuator moves toward the fully actuated position and decreases as the actuator moves toward the fully released position.

According to yet another embodiment, a vehicle includes a rear axle having wheels, friction brakes associated with the wheels, and a driver-actuatable input. A vehicle controller is programmed to, in response to the vehicle being in drift mode and the driver-actuatable input being actuated: command zero torque to the wheels, regardless of a driver-demanded torque, for a duration of time; command engagement of the friction brakes responsive to the duration of time ending; and command torque to the wheels responsive to a speed of the wheels being less than a threshold.

DETAILED DESCRIPTION

Referring toFIG. 1, an electrified vehicle20is illustrated as a fully electric vehicle but, in other embodiments, the electrified vehicle20may be a hybrid-electric vehicle that includes an internal-combustion engine or a conventional vehicle only having an engine. The vehicle20has electric all-wheel drive (AWD). The vehicle20may include a primary drive axle24and a secondary drive axle22. In the illustrated embodiment, the primary drive axle24is the rear axle and the secondary drive axle22is the front axle. In other embodiments, the front axle may be the primary drive and the rear axle may be the secondary drive. The primary and secondary axles may include their own powerplant, e.g., an engine and/or an electric machine, and are capable of operating independently of each other or in tandem to accelerate (propel) or brake the vehicle20.

The secondary drive axle22may include at least one powerplant, e.g., electric machine26, operable to power the wheels30and31. A gearbox (not shown) may be included to change a speed ratio between the wheels30,31and the powerplant(s). The gearbox may be a one-speed direct drive or a multi-speed gearbox. The primary drive axle24may include at least one powerplant, e.g., an electric machine34, that is operably coupled to the wheels32and33. A gearbox (not shown) may be included change a speed ratio between the powerplant(s)34and the wheels32,33.

The electric machines28,34are capable of acting as motors to propel the vehicle20and are capable of acting as generators to brake the vehicle via regenerative braking. In one or more embodiments, the electric machines28,34are permanent magnet synchronous alternating current (AC) motors or other suitable type.

The electric machines28,34are powered by one or more traction batteries, such as traction battery36. The traction battery36stores energy that can be used by the electric machines28,34. The traction battery36typically provides a high-voltage direct current (DC) output from one or more battery cell arrays, sometimes referred to as battery cell stacks, within the traction battery36. The battery cell arrays include one or more battery cells. The battery cells, such as a prismatic, pouch, cylindrical, or any other type of cell, convert stored chemical energy to electrical energy. The cells may include a housing, a positive electrode (cathode), and a negative electrode (anode). An electrolyte allows ions to move between the anode and cathode during discharge, and then return during recharge. Terminals may allow current to flow out of the cell for use by the vehicle20. Different battery pack configurations may be available to address individual vehicle variables including packaging constraints and power requirements. The battery cells may be thermally regulated with a thermal management system.

The traction battery36may be electrically connected to one or more power-electronics modules through one or more contactors. The module may be electrically connected to the electric machines28,34and may provide the ability to bi-directionally transfer electrical energy between the traction battery36and the electric machines28,34. For example, a typical traction battery36may provide a DC voltage while the electric machines28,34may require a three-phase AC voltage to function. The power-electronics module may convert the DC voltage to a three-phase AC voltage as required by the electric machines. In a regenerative mode, the power-electronics module may convert the three-phase AC voltage from the electric machines28,34acting as generators to the DC voltage required by the traction battery36.

The vehicle20includes a controller40that is in electronic communication with a plurality of vehicle systems and is configured to coordinate functionality of the vehicle. The controller40may be a vehicle-based computing system that includes one or more controllers that communicate via a serial bus (e.g., controller area network (CAN)) or via dedicated electrical conduits. The controller40generally includes any number of microprocessors, ASICs, ICs, memory (e.g., FLASH, ROM, RAM, EPROM and/or EEPROM) and software code to co-act with one another to perform a series of operations. The controller40also includes predetermined data, or “lookup tables” that are based on calculations and test data, and are stored within the memory. The controller40may communicate with other vehicle systems and controllers over one or more wired or wireless vehicle connections using common bus protocols (e.g., CAN and LIN). Used herein, a reference to “a controller” refers to one or more controllers. The controller40, in one or more embodiments, any include any of the follow control modules: a battery energy control module (BECM) that operates at least the traction battery, an engine control module (ECM) that operates at least the engine, a powertrain control module (PCM) that operates at least the electric machines, the gearboxes, and the differential(s), and an ABS control module that controls the anti-lock braking system (ABS)38.

The ABS38, while illustrated as a hydraulic system, may be electronic or a combination of electronic and a hydraulic. The ABS38may include a brake module and a plurality of friction brakes42located at each of the wheels. Modern vehicles typically have disc brakes; however, other types of friction brakes are available, such as drum brakes. Each of the brakes42are in fluid communication with the brake module via a brake line configured to deliver fluid pressure from the module to a caliper of the brakes42. The module may include a plurality of valves configured to provide independent fluid pressure to each of the brakes42. The brake module may be controlled by operation of a brake pedal44and/or by the vehicle controller40without input from the driver. The ABS system38also includes associated wheel-speed sensors46each located on one of the wheels. Each sensor46is configured to output a wheel-speed signal to the controller40indicative of a measured wheel speed.

The vehicle20is configured to slow down using regenerative braking, friction braking, or a combination thereof. The controller40includes programming for aggregating a demanded braking torque between regenerative braking, i.e., the electric machines, and the friction brakes42. The demanded braking torque may be based on driver input, e.g., a position of the brake pedal44or a hand-operated actuator, or by the controller40. The aggregator of the controller40may be programmed to prioritize regenerative braking whenever possible.

The vehicle20includes an accelerator pedal45. The accelerator pedal45includes a range of travel from a released position to a fully depressed position and indeterminate positions therebetween. The accelerator pedal45includes an associated sensor (not shown) that senses the position of the pedal45. The sensor is configured to output a pedal-position signal to the controller40that is indicative of a sensed position of the pedal45. The accelerator pedal45is used by the driver to command a desired speed of the vehicle. Under normal conditions, the accelerator pedal45is used by the driver to set a driver-demanded torque. The controller40may be programmed to receive the pedal-position signal and determine the driver-demanded torque based on pedal position and other factors.

The vehicle20may include one or more sensors48configured to determine accelerations of the vehicle. For example, the sensors48may include a yaw-rate sensor, a lateral-acceleration sensor, and a longitudinal-acceleration sensor. Used herein, “acceleration” refers to both positive acceleration (propulsion) and negative acceleration (braking). The yaw-rate sensor generates a yaw-rate signal corresponding to the yaw rate of the vehicle. Using the yaw-rate sensor, the yaw acceleration may also be determined. The lateral-acceleration sensor outputs a lateral-acceleration signal corresponding to the lateral acceleration of the vehicle. The longitudinal-acceleration sensor generates a longitudinal-acceleration signal corresponding to the longitudinal acceleration of the vehicle. The various sensors are in communication with the controller40. In some embodiments, the yaw rate, lateral acceleration, longitudinal acceleration, and other measurements may be measured by a single sensor.

The vehicle20may also include a steering system49that turns the front wheels30,31. The steering system49may include a steering wheel connected to a steering shaft that actuates a steering box, such as a rack-and-pinion assembly. The steering box is operably coupled to the front wheels30,32and turns the wheels according to inputs from the steering wheel. The steering system49may include one or more sensors configured to output a signal indicative of steering angle to the controller40. The steering sensor may measure rotation of the steering shaft or movement of another component(s).

Electric all-wheel drive vehicles, e.g., vehicle20, utilize independent propulsion devices, e.g., electric machines, at each axle enabling independent control of the torque at each axle. As such, the vehicle can dynamically adjust the front-rear torque split in order to maximize traction, handling performance, and the like. One benefit of electric AWD is that the electric machines can change the torque delivery more quickly and accurately than an internal-combustion engine. As a result, the electric machines can allow for precise control of each axle. The speed of the electric machine directly reflects the average speed of the wheels on each axle. Therefore, the average wheel speed of each axle can be controlled by actively controlling the electric-machine speed at each axle to propel the vehicle at a driver-demanded speed. As will be described in more detail below, the individual wheels of at least one of the axles, or both in some embodiments, can be independently controlled to enable torque vectoring. In the illustrated embodiment, the rear axle24includes a special differential35capable of individually controlling the torque to each wheel between zero and 100 percent. The differential35includes an input operably coupled the electric machine34and a pair of outputs connected the wheels32,33respectively. The differential35may include clutches, for example, each associated with one of the wheels. The clutches are controller to selectively couple the wheels to the input. Capacity of the clutches can be varied to route torque to the wheels between zero and 100 percent. Clutches, are of course, merely one embodiment and any suitable design may be used. The front axle22may also include a differential similar to differential35, or equivalent device, to control torque individually to the wheels30,31. That is, the vehicle20may include torque vectoring for the rear wheels, the front wheels, or both.

FIG. 2illustrates another vehicle architecture contemplated by this disclosure. A vehicle60may be an all-wheel-drive vehicle in which both the front axle62and the rear axle64are powered by electric machines. In the illustrated embodiment, the vehicle60may include four electric machines66,68,70, and72, one associated with each of the wheels74,76,78, and80. The electric machines may be referred to as wheel motors. Each of the electric machines as independently controllable so that the vehicle60can command independent speeds to each of the wheels. This enables the vehicle62to have torque vectoring at both the front and rear axles62,64. Having an electric machine associated with each wheel eliminates the need for complex differentials or similar devices.

In other embodiments, the vehicle60may only be two-wheel drive, such as front-wheel-drive or rear-wheel drive. In a front-wheel drive configuration, the rear motors70and72are eliminated, and in a rear-wheel drive configuration, the front motor66and68are eliminated.

In another embodiment, the vehicle60may be all-wheel-drive but only one axle may include individual wheel motors. For example, the front axle may be powered by a single electric machine (similar to that shown inFIG. 1) whereas the rear axle is powered by electric machine70and72. This could also be switched, with the front axle continuing to include motors66and68and the rear axle including a single motor.

This disclosure also contemplates vehicles with hybrid and conventional powertrains that include, as at least one of the powerplants, an internal combustion engine. These vehicles may include a differential(s), similar to differential35, configured to output torque individually to the wheels of at least one axle.

Torque vectoring is an automotive technology that allows variable torque to be delivered to individual wheels of a common axle. As discussed above, torque vectoring capability can be accomplished through special types of differentials or through wheel motors. Torque vectoring is typically used to facilitate cornering or to enable “drifting.” When a vehicle corners, the outside wheel rotates faster than the inside wheel. Torque vectoring leverages this and intentionally increases the speed differential between the inner and outer wheels allowing the vehicle to corner sharper. The speed differential is induced by changing a torque differential between the wheels, i.e., more torque is applied to the outside wheel and less torque is applied to the inside wheel. The torque differential can be accomplished by increasing the torque to the outside wheel, decreasing the torque to the inside, braking the inside wheel, or combinations thereof.

Referring back toFIG. 1, the controller40is programmed to provide torque vectoring. Relevant controller inputs for torque vectoring may include yaw-rate, lateral acceleration, longitudinal acceleration, vehicle speed, accelerator-pedal position, brake-pedal position, driver demanded torque, torque available, steering wheel angle, coefficient of friction calculation and driver input based on paddle position or force, and the like. Generally, the controller40may include a plurality of lookup tables that output a wheel-torque differential (for all relevant axles) based on sensed conditions. The wheel-torque differential is used to determine the proportion of torque routed to the individual wheels. During a right turn, for example, the controller40may determine a torque split of 60-40 for the rear axle24and the motor34may be producing torque such the input of the differential35receives 100 Newton meters (Nm) of torque. The differential35is controlled to send 60 Nm to the left (outside) wheel32and 40 Nm to the right (inside) wheel33. According to one or more embodiments, the controller40may control the differential35by commanding specific pressures to the clutch packs. In this embodiment, the calculated wheel-torque differential is converted into pressure commands for the clutches of the differential35. In other embodiments, the torque differential is divided between the pair of motors for the axle, i.e., the motor associated with wheel32is commanded to produce 60 Nm of torque in the motor associated with the right wheel33is commanded to produce 40 Nm of torque.

Typically, torque vectoring is controlled solely by the controller(s) of the vehicle and the driver is not permitted to request or deny torque vectoring. To increase driver involvement, the vehicle20is configured to enable the driver to manually control torque vectoring. The vehicle20may also be programmed to automatically control torque vectoring depending upon different operating modes of the vehicle or driver-selectable option. For example, the vehicle may include a normal driving mode in which torque vectoring is automatically controlled by the controller40, and may include another driving mode, such as sport mode or track mode, in which the driver is able to manually control torque vectoring. The driver control of torque vectoring may be ON/OFF or may also include the amount (or aggressiveness) of the torque vectoring. That is, the driver may actuate an ON/OFF input that results in the vehicle activating the torque vectoring controls, or alternatively, the driver may actuate a variable input in which the torque vectoring controls increase or decrease the amount of torque differential based on the position of the variable input. The advent of electrified vehicles has reduced driver interaction, mostly through the elimination of the transmission, and providing manually controlled torque vectoring is one way to increase the driver interaction for electric vehicles. This may provide a more satisfying driving experience on the track or other closed course.

Referring toFIG. 3, the torque-vectoring control devices may be mounted on a steering wheel100or any other location that is easily assessable to the driver. The torque-vectoring controls are driver-actuatable inputs operable to request left-side and right-side torque vectoring, respectively. In the illustrated embodiment, the inputs are paddles102and104. The paddles102and104may be mounted on a backside of the steering wheel100or may be mounted to the steering column (not shown). The paddles102,104each include an associated sensor configured to sense actuation of the paddles and output a signal, e.g., a paddle-position signal, to the controller40indicative of an actuation state, e.g., a position, of the paddle.

In one embodiment, the paddles are ON/OFF switches that the driver can use to request torque vectoring. In response to the driver request, the controller40executes the torque vectoring controls that may be continuously operating behind the scenes. In this embodiment, the driver is only able to ask for torque vectoring, or not, and it is the purview of the vehicle controller to determine the amount of vectoring based on sensed conditions as discussed above.

Referring toFIG. 4, to provide even more driver interaction, the paddles may have a range of positions in other embodiments allowing the driver to not only command activation of torque vectoring but also the amount. Here, an example paddle assembly106includes a paddle (an actuator)108connected to a guide member110that is movable through a range of positions including a fully released position112, a fully actuated position114, and a plurality of intermediate positions108. The sensor116senses movement of the guide member110and outputs a signal to the controller40indicative of the position of the paddle assembly106.

The position of the paddle assembly106may be correlated into a percentage of requested torque vectoring. The vehicle may calculate a baseline torque vectoring value based on sensed conditions. The paddle assembly106, in addition to ON/OFF, operates to scale the amount of torque vectoring up, down, or a combination of both. In one embodiment, the position of the paddle108represents a percentage of the baseline torque vectoring to be applied. When the paddle108is fully pulled, the vehicle commands 100 percent of the baseline torque vectoring. When the paddle108is in an intermediary position, the baseline vectoring is multiplied by a percentage of actuation resulting in less torque vectoring. In another embodiment, the driver may be able to request more torque vectoring than the baseline torque vectoring. Here, one of the intermediate positions represents a request for 100% of the baseline vectoring. Actuation of the paddle100beyond this point results in increased torque vectoring and actuating less than this point produces less torque vectoring compared to the baseline.FIG. 4is merely one embodiment of a variable-position torque-vectoring control device and other forms are contemplated.

FIG. 5illustrates the vehicle60during a left-hand turn. In this example, the driver has pulled the paddle104to request torque vectoring. In response, the controller40calculates a torque differential between the wheel74and76and between the wheels78and80. In this example, the torque vectoring is aggressive resulting in regenerative braking being commanded to the motors66and70and a positive torque being commanded to the motors68and72. In a less aggressive example, the motor66and70may coast or provide positive torque, albeit less than the motors68and72. Torque vectoring does not have to occur at both the front and the rear axles. Depending on the desired vehicle characteristics and vehicle attributes, torque vectoring may occur only at the rear axle or only at the front axle. The inner wheels can also be braked using the friction brakes.

Referring toFIG. 6, the torque-vectoring control devices can also be used by the driver to request regenerative braking. The driver can request regenerative braking by pulling both the left and right torque-vectoring control devices, e.g. pulling both the left to right paddles104,102. In response to both battles being pulled, the controller40commands a negative (regenerative) torque to the electric machine66,68,70, and72. The amount of regenerative torque commanded is a calibrated value and can be tuned to provide more or less aggressive regenerative braking. The amount of regenerative braking may also be based on vehicle speed, battery state of charge, and other sensed conditions as known in the art. If variable position paddles are provided, the driver and modulate the paddles to increase and decrease the negative torque.

FIG. 7illustrates the paddle-requested regenerative braking on a vehicle120with only a rear electric axle. In this embodiment, actuating both the left and right paddles104,102(or other input) results in the controller commanding regenerative braking to the motors122and124and to command friction braking to the front friction brakes126and128.

FIG. 8is a flowchart150of an algorithm for controlling manual torque vectoring according to one or more embodiments. The controls begin in response to one of the torque-vectoring control devices being actuated by the driver. At operation152, the controller determines if the right input is actuated. If yes, control passes operation154, and the controller determines if the left input is actuated. If yes, the driver is requesting regenerative braking and control passes to regenerative-braking controls200. (The regenerated braking controls will be described in detail below.) At operation156, the controller determines if the steering angle is greater than a threshold, i.e., is the driving making a right-hand turn? If the driver is not turning the vehicle to the right, or is not turning by a sufficient amount, torque vectoring does not occur. In other embodiments, operation156may be omitted. A YES at operation156establishes that torque vectoring is going to be commanded. Operations158through164determine the amount of torque vectoring. Similar controls are provided for the left input and will not be discussed for brevity.

At operation158, the controller receives data from various sensors of the vehicle. The data may include steering angle, accelerator-pedal position, brake-pedal position, motor torque, motor speed, engine torque, vehicle speed, yaw rate, lateral and longitudinal acceleration, braking torque, traction control, ABS, electronic stability control, wheel speeds, differential temperature, torque-vectoring paddle position, and others.

Based on this data, the controller, at operation160, calculates a torque differential for each axle in which torque vectoring is to occur. Depending upon the vehicle and sensed conditions, this may include the rear axle, the front axle, or both. The torque differential is the torque difference commanded between the inside and outside wheels of the axle. As discussed above, the torque difference may be effectuated by increasing torque to the outside wheel and decreasing torque to the inside wheel through a reduced motor torque and/or braking (regenerative, friction, or both). Depending upon the embodiment, the controller may calculate multiple torque differentials. For example, in the ON/OFF embodiment the controller may calculate a torque differential that is either commanded or not based on paddle actuation. In the variable torque-vectoring embodiment, the controller may calculate a baseline torque differential and then calculate a final torque differential based on the amount of actuation of the paddle. The final torque differential may be equal to the baseline torque differential multiplied by a multiplier. The multiplier may be less than one for a first range of paddle positions to provide less torque vectoring and may be greater than one for a second range of positions to provide increased torque vectoring based on driver demand.

The calculated torque differential of operation160is then fed to operation162. At operation162, a torque arbitrator module determines how best to effectuate the desired torque differential between the inner and outer wheels. The torque arbitrator module162also receives the sensor data from operation158, and based on the sense conditions, determines the motor-torque commands (both positive and negative) and friction-braking commands. Depending upon the magnitude of the torque differential and the sense conditions, the arbitrator module may command a an increased positive torque to the outside wheel and a negative torque to the inside wheel or may command an increased positive torque to the outside wheel and a reduced positive torque to the inside wheel. When a negative torque is commanded to the inside wheel, the arbitrator module also determines a torque split between the regenerative braking and the friction braking. The arbitrator module may also determine commands for the differential, e.g., commands for the differential35.

At operation164, the commands are issued to the various actuators and components according to the determinations of the torque arbitrator module at operation162. The commands issued at operation164depend upon the components of the vehicle. In the example embodiment ofFIG. 1, the commands may include torque commands to the motors26,34, commands to the differential35, and/or commands to the friction brakes42.

FIG. 9illustrates the regenerative braking controls200according to one or more embodiments. The controls begin in response to the left and right torque-vectoring inputs being actuated at operation202. At operation204, the controller receives sensor data. Based on the sensor data, motor commands are issued at operation206. At operation208, friction brake commands may also be issued depending upon the sensed conditions and the hardware of the vehicle.

The torque-vectoring control devices may also be used to request a drifting mode in one or more embodiments. The drifting mode, which is used on the track or in other closed-course driving, is a mode that produces heavy oversteer. The drift mode may be selected through a human-machine interface such as the main touchscreen or the like. When in drift mode, application of the torque-vectoring control devices results in the vehicle being placed into a drift condition. A vehicle may only include the drift mode and not torque vectoring. Alternatively, a vehicle may include torque vectoring and not drift mode.

FIG. 10illustrates example controls220for drift mode according to one or more embodiments. Control begins at operation222when the driver requests drift mode. In drift mode, the vehicle may operate substantially normally (some systems such as traction control and electronic stability control may be disabled in this mode) until the driver actuates one or more of the inputs, e.g., paddles. The controller monitors for actuation of the inputs at operation224. Control passes to operation226in response to one or more of the inputs being actuated at operation224. In operation226, the controller commands zero torque to at least the rear wheels regardless of the driver-demanded torque from the accelerator pedal. That is, the actuator torque commands are overridden, and the wheel torques are reduced to zero. At operation228, the controller commands engagement of the friction brakes associated with the rear axle to lock-up the rear tires and brake traction with the pavement. The amount of braking commanded at operation228may be a calculated value based on sensed conditions or may be the maximum braking torque. The rear brakes are engaged until the rear tires brake traction, e.g., the rear axles is placed in a skid. The brakes may be commanded for a predetermined amount of time estimated to induce lock-up, or alternatively (as shown), the controller may monitor for wheel speed. At operation230, the controller determines if the wheel speed is less than a threshold value. If no, the rear brakes remain applied until the threshold wheel speed is achieved. If yes at operation230, control passes to operation232and the controller commands torque to the wheels. The torque commanded to the wheels at operation232may be based on the driver-demanded torque.

The above-described manual torque vectoring, manual regenerative braking, and drift mode increase driver involvement with the vehicle to offset the reduced driver interaction associated with electric vehicles. By including one or more of these manual features, driver interaction can be increased to satisfy the needs of some drivers.