Electric vehicle with anti-rollback control

Abstract

A method of reducing rollback of an electric vehicle is provided, the method comprising the steps of: determining a position baseline of the electric vehicle; determining a position compensation speed of the electric vehicle based on the position baseline; determining a holding torque as a function of the position compensation speed; and generating a command to apply the holding torque to an electric generator of the electric vehicle.

Description

[0001] Cross-references to related applications

[0002] This application claims the benefit and priority of U.S. Provisional Patent Application No. 62 / 942,031, filed November 29, 2019, the entire contents of which are incorporated herein by reference. Technical Field

[0003] This disclosure relates to vehicles having a motor-generator, and more particularly to vehicles powered by a motor-generator without a torque converter. Background Technology

[0004] Conventional vehicles equipped with internal combustion engines and fully automatic transmissions mitigate rollback when starting from a standstill on an uphill slope via a torque converter that generates continuous driveline torque. Although less efficient, the continuous driveline torque tends to counteract the effects of gravity when starting on a slope.

[0005] The goal is for electric vehicles to offer customers greater transparency regarding driving performance compared to conventional vehicles. Summary of the Invention

[0006] This article provides an electric vehicle, a drivetrain controller, and a method for reducing rollback in an electric vehicle. The method can be implemented using a drivetrain controller installed in the electric vehicle.

[0007] [1] In a first aspect of this disclosure, a method for reducing the rollback of an electric vehicle includes the steps of: determining a position baseline of the vehicle; determining a position compensation speed of the vehicle based on the position baseline; determining a holding torque based on the position compensation speed; and generating a command to apply the holding torque to the electric generator of the vehicle.

[0008] [2] According to the method described in [1], the step of determining the position baseline includes: determining the vehicle’s stopping condition or speed polarity change, wherein the position baseline is the position of the vehicle when the stopping condition or speed polarity change is determined.

[0009] [3] According to the method described in [2], the step of determining the stopping status of the vehicle includes: determining the time when the vehicle’s speed is less than or equal to the absolute zero speed tolerance and the zero speed dwell time.

[0010] [4] According to the method described in [1], the step of determining the position compensation speed of the vehicle includes: adding the position baseline component to the attenuation speed component, wherein the attenuation speed component includes the product of the vehicle speed and the speed coefficient.

[0011] [5] According to the method described in [4], the holding torque is based on the product of the position compensation speed and the speed coefficient.

[0012] [6] According to the method described in [1], the holding torque is based on the product of the position compensation speed and the speed coefficient.

[0013] [7] According to the method described in [6], the vehicle's position compensation speed includes: the sum of the position baseline component and the attenuation speed component, wherein the attenuation speed component includes the product of the vehicle's speed and the speed coefficient.

[0014] [8] According to the method of [7], wherein maintaining torque includes canceling the rate limit.

[0015] [9] According to the method described in [8], the rate limit cancellation is reduced over time.

[0016]

[10] The method according to any one of [4] to [9], wherein the speed coefficient includes a normalized dwell time based on a brake release event or the vehicle speed being less than the absolute zero speed tolerance.

[0017]

[11] According to the method described in

[10] , the velocity coefficient varies between 0 and 1.

[0018]

[12] According to the method of

[10] , the normalized dwell time includes the ratio of dwell time based on the brake release event or the vehicle speed being less than the absolute zero speed tolerance.

[0019]

[13] According to the method of

[10] , the speed coefficient is reduced if the speed is greater than the absolute zero speed tolerance or if the brake is reapplied.

[0020]

[14] The method according to any one of [4] to [9], wherein the speed coefficient is proportional to the dwell time that begins when the vehicle's brakes are released or the vehicle's speed is less than the absolute zero speed tolerance.

[0021]

[15] According to the method of [1], the method further includes the step of disengaging the holding torque if the speed of the vehicle exceeds the cancellation speed.

[0022]

[16] According to the method of

[15] , the step of disengaging the holding torque includes: reducing the holding torque to zero.

[0023]

[17] According to the method of

[16] , the step of disengaging the holding torque includes: rate limiting the rate at which the holding torque decreases to zero.

[0024]

[18] According to the method of [1], the method further includes the step of determining the slope of the vehicle, wherein the holding torque function further includes a slope component including the slope and the slope gain.

[0025]

[19] According to the method of [1], the method further includes the step of determining the mass of the vehicle, wherein the torque holding function further includes a mass component including the mass and the mass gain.

[0026]

[20] According to the method described in [1], the method further includes the step of determining the inclination and mass of the vehicle, wherein the torque holding function further includes components of inclination and mass.

[0027]

[21] According to the method of [1], the method further includes the step of: brake pressure feedback, wherein the holding torque function includes a brake pressure feedback component.

[0028]

[22] According to the method described in [1], the method further includes the steps of: determining the slope and determining the mass of the vehicle based on the slope, wherein the holding torque function further includes a mass component based on the mass.

[0029]

[23] In a second aspect of this disclosure, a controller for a vehicle is provided, the vehicle including an electric generator operable to drive the wheels of the vehicle, the controller including: processing instructions that, when executed, implement the method according to any one of [1] to

[22] .

[0030]

[24] In a third aspect of this disclosure, an electric vehicle is provided, the electric vehicle comprising: a wheel, a wheel support frame; an electric generator operable to drive the wheel; and a controller comprising processing instructions which, when executed, implement the method according to any one of [1] to

[22] .

[0031]

[25] The vehicle according to

[24] further includes a sensor that is communicatively connected to the controller and operable to sense the movement of the vehicle.

[0032]

[26] The vehicle according to

[24] further includes a brake pedal and a brake sensor, which is communicatively connected to a controller and operable to determine the pressure applied to the brake pedal. Attached Figure Description

[0033] The above-mentioned and other disclosed features, ways of obtaining them, and their advantages will become more apparent and better understood by referring to the following description of the disclosed embodiments in conjunction with the accompanying drawings, wherein:

[0034] Figure 1 This is a schematic diagram of an electric vehicle;

[0035] Figure 2 yes Figure 1 A schematic diagram of the powertrain of an electric vehicle, including a traction motor connected to a drive shaft;

[0036] Figure 3 This is a flowchart illustrating the implementation of the rollback control method;

[0037] Figures 4 to 14 Simulink simulations jointly representing the implementation of the rollback control method; and

[0038] Figure 15 yes Figure 1 A block diagram illustrating an implementation of a drivetrain controller in an electric vehicle, which is operable to achieve... Figures 4 to 14 Rollback control methods;

[0039] Figure 16 and Figure 17 It is to realize the reference Figures 4 to 14 The described implementation of the rollback method includes a variation of the electric vehicle's position and torque versus time graphs; and

[0040] Figure 18 It is to realize the reference Figures 4 to 14 A graph of the position versus time of an electric vehicle, representing another variation of the described rollback method implementation.

[0041] Throughout these views, corresponding labels indicate the corresponding parts. The examples described herein illustrate embodiments of the invention, and these examples should not be construed as limiting the scope of the invention in any way. Detailed Implementation

[0042] For the purpose of promoting understanding of the principles of the invention, embodiments illustrated in the accompanying drawings are now described below. The embodiments disclosed below are not intended to be exclusive or to limit the invention to the precise forms disclosed in the following detailed description. Rather, these embodiments were chosen and described so that others skilled in the art can utilize their teachings. The selection of the disclosed embodiments is not intended to limit the scope of the invention.

[0043] As used herein, electric vehicles include vehicles that have an electric generator or electric motor. Typically, the powertrain or drivetrain is an electric motor directly or indirectly connected to a traction system. The traction system may include, for example, wheels. Wheels may drive continuous tire treads or tracks. The powertrain may be entirely electric (e.g., a fully electric vehicle) or may include an internal combustion engine in addition to an electric motor (e.g., a hybrid vehicle). Therefore, hybrid vehicles and fully electric vehicles are types of electric vehicles.

[0044] Example electric vehicles include: cars, trucks, forklifts, buses, straddle carriers, reach stackers, empty container loaders, etc. As used herein, vehicle weight includes both unloaded weight or tare weight and loaded weight. The loaded weight of an electric vehicle can vary significantly during use. The weight of a bus changes as passengers board and alight. Trucks can be configured to detachably attach trailers or containers, therefore their loaded weight includes the weight of the trailer or container, which can be empty, partially loaded, or fully loaded. For example, a shipyard truck may have an unloaded weight of 25,000 lbs and a loaded weight of 75,000 lbs, thus significantly altering drivetrain torque and braking requirements between the loaded and unloaded states of the electric vehicle.

[0045] Figure 1 This is a schematic diagram of an electric vehicle 100 including an electric traction system 101, which includes: an electric generator 102 and wheels 110 connected to the electric generator 102 via an axle (not shown) or directly; an inverter 118 operable to generate motor voltage for the electric motor 102; a battery 20 connected to a bus 30 to power the electric traction system 101; and a drivetrain controller 40. Drivetrain logic 42 (alternatively referred to as processing instructions) of the drivetrain controller 40 establishes communication (as known in the art) between the drivetrain controller, the battery, and the inverter via communication lines 21 and 51. Preferably, the communication lines transmit digital data between the components. A CAN bus can be implemented to provide the communication lines. The drivetrain controller monitors sensor signals from sensor 44, performs safety and performance checks, determines faults based on these checks, and monitors operator controls such as mode selectors (e.g., drive / reverse), brake pedal position, and accelerator pedal position. (See reference...) Figure 15 This describes the additional sensors and signals. Electric vehicle 100 does not include a torque converter.

[0046] Battery 20 may include one or more battery packs, which include a battery management unit (BMU) 22 and battery modules 24. BMUs are generally known. Temperature sensors, voltage sensors, and other sensors may be provided to enable BMU 22 to manage the charging and discharging of battery modules 24 without exceeding their limits, to detect and manage faults, and to perform other known functions. BMU 22 may transmit information about the battery, including battery charging power limits, temperature, faults, etc., to drivetrain controller 40 via communication lines. Battery 20 may include a current sensor 26 to provide the BMU with measured current values.

[0047] Drivetrain logic 42 is operable to determine commands for the inverter to supply motor voltage to motor 102. As is known in the art, the motor voltage is configured to cause motor 102 to generate a desired amount of torque. The desired torque is configured taking into account the gear ratio and the number of motors that can be engaged (including varying motor sizes). Drivetrain controller 40 may include functions known in the field of electric vehicles. If an internal combustion engine is provided in a hybrid vehicle or the like, such functions may include those for range extension, regeneration, and torque ratio control.

[0048] Electric vehicles are expected to offer customers greater transparency in driving performance compared to conventional vehicles, including features to counteract rollback. Different approaches have been considered based on detected motion, which can be susceptible to various limitations. For example, response time may prevent electric vehicles from generating sufficient torque in time to prevent significant rollback. Additionally, the naturally underdamped kinematics of the vehicle's drivetrain can be susceptible to large, sudden torque applications that can cause drivetrain speed / torque oscillations. Algorithms that generate counteracting torque solely based on speed tend to generate oscillations based on sudden, high-gain reactions. Algorithms that are solely based on position may tend to overshoot the desired maximum position because they must generate torque to offset both gravity and the kinetic energy of the already moving vehicle. Therefore, even when these algorithms mitigate drivetrain speed oscillations, if such oscillations do occur, the controller often uses the counteracting torque to "track" the changing speed, thus perpetuating the oscillations. The tendency to induce drivetrain instability also complicates rollback detection. If negative velocity indicates a rollback, it can also be observed during a sudden stop, where the measured velocity may exhibit underdamped stability at zero, thus generating multiple excursions within the negative velocity range. The challenge becomes distinguishing between negative velocity caused by a rollback and negative velocity caused by an undershoot.

[0049] Now, referring to Figure 2The kinematics of the vehicle drivetrain 101 are described below. The drivetrain 101 includes a traction motor or electric generator 102 connected to a drive shaft 104 to rotate a differential 106 connected to drive wheels 110. The torque applied by the traction motor 102 torsional the drive shaft 104. When the vehicle stops, drivetrain oscillation occurs when the potential energy caused by the torsion of the drive shaft is rapidly released. If the energy of the shaft torsion is little or nonexistent, there is no discernible oscillation. The way to distinguish between actual rollback and failure to reach the target due to oscillation is to identify the factors generating torsion in the shaft, i.e., applying the vehicle brakes to a moving vehicle. If the vehicle has stopped or the brakes have been released for a certain period, any observed negative speed is almost certainly rollback. The rollback control methods described below rely on these characteristics.

[0050] In the following text, reference will be made to Figure 3 The flowchart 120 depicts an implementation of the rollback control method. Typically, the method includes the steps of: generating a holding torque based on a position-compensated speed; and commanding the vehicle's electric generator to apply this holding torque to mitigate rollback. This method is particularly advantageous in large vehicles such as buses and trucks, which require considerable holding torque to counteract gravity on uneven terrain. The method is even more advantageous in buses because a slow response to rollback would require a larger holding torque, which could significantly impact passengers when applied.

[0051] Still refer to Figure 3 In section 124, the method begins by determining a position baseline for the vehicle. The step of determining the position baseline may include: determining a stopping state or a speed polarity change of the vehicle, wherein the position baseline is the position of the vehicle when the stopping state or speed polarity change is determined. A speed polarity change is an indication of an instantaneous stopping state. In other words, on a positive slope, when the vehicle stops moving forward, it stops for a very brief amount of time before beginning to move backward. The position baseline can be determined relative to the angular position of the flywheel or gear or other components of the vehicle's drivetrain. The position baseline is used to determine distances from the baseline.

[0052] The steps for determining a vehicle's stopping status may include: determining the time the vehicle's speed is less than or equal to the absolute zero speed tolerance until it reaches zero speed. The absolute zero speed tolerance defines a range of speeds relative to zero. If the vehicle's speed falls within this range, the vehicle is considered to be stopped.

[0053] In step 126, the method continues to determine the distance from the baseline. If the baseline position is determined from the angular position of the rotating component, this distance can be calculated by tracking the movement of the rotating component since the time when the baseline position was determined.

[0054] At 128, the vehicle's speed is determined. Speed ​​can be determined from angular position or from other sensors that indicate speed. Taking into account the reduction ratio, angular position can be sensed by sensing gear teeth or other detectable features in rotating components. The same sensor can be used to determine speed by counting signals sensed over a certain period of time.

[0055] At 130, the speed coefficient is determined. The speed coefficient is used to decrease the speed inversely proportional to the indication of the torsional potential energy of the drive shaft. In one example, the time since the brakes were released or the vehicle remained stationary can be used to determine the speed coefficient.

[0056] The speed coefficient can include a normalized dwell time based on the stopping condition. The speed coefficient can be normalized to a range between 0 and 1, where 0 represents complete decay and 1 represents no decay. The speed coefficient can be reduced if the speed exceeds the absolute zero speed tolerance or if the brakes are reapplied.

[0057] At 132, the holding torque is determined. The holding torque is determined by considering distance, speed, and speed coefficient. The product of speed and speed coefficient can be called the decay speed. The sum of the components representing both decay speed and distance can be called the position compensation speed. A table or mapping relating position compensation speed to torque can be used to determine the holding torque based on the position compensation speed. In a variant of this embodiment, the speed coefficient is omitted. Multiple tables can be used instead of the speed coefficient to describe the torsional potential energy. It should be understood that the speed, speed coefficient, and distance parameters can be determined in any order or simultaneously.

[0058] At 136, the holding torque command is determined. The holding torque command is determined based on the value of the holding torque. When the application of the holding torque is cancelled, a cancellation rate limit can be applied to limit the rate at which the holding torque is reduced to zero. Cancellation may be due to the application of the brakes or a change to a different drive mode.

[0059] For example, if the vehicle's speed exceeds the disengagement speed or the drive mode is switched, the holding torque can be disengaged. Disengaging the holding torque can include reducing the holding torque to zero. The rate at which the holding torque is reduced to zero can be limited.

[0060] In some implementations, the slope of the terrain is determined, and a holding torque is generated based on the position-compensated speed and that slope. The slope represents the inclination of the terrain where the vehicle is situated and can be obtained from a topographic map and GPS location, or from a slope sensor located within the vehicle, indicating the vehicle's relationship to a vertical or horizontal axis. Example slope sensors include accelerometers, inertial sensors, tilt sensors, and gravity sensors. A six-axis inertial sensor can be used as a slope sensor. Inertial sensors can be integrated into microelectromechanical systems (MEMS) integrated circuits.

[0061] Accelerometers can be used to determine acceleration. Accelerometers can also be integrated into MEMS integrated circuits. MEMS integrated circuits typically contain circuitry that converts mechanical movement into an analog or digital voltage output representing that movement. Acceleration can also be obtained from the drivetrain control unit or other onboard systems. The gradient component of the holding torque can be determined based on the expected rollback amount, further improving rollback control. Alternatively, if the vehicle's power / acceleration ratio is tracked over time, the mass indication is provided by that ratio, and the gradient can be obtained as the vehicle travels based on the mass.

[0062] In some implementations, the mass of the vehicle is determined, and the torque is maintained by including a component representing the mass. The mass of the vehicle can be determined by monitoring power and acceleration over time, where power is related to the product of mass and acceleration. An indication of the vehicle's mass can be characterized based on measurements of various power and acceleration levels obtained during vehicle operation. The power / acceleration ratio when the vehicle is loaded compared to when it is empty will indicate the mass due to the load. Other methods for determining the mass based on the vehicle's performance parameters are known and can be used herein. The mass can be determined substantially continuously to account for weight changes, for example, due to passengers getting on and off the vehicle.

[0063] In some implementations, the slope of the terrain and the mass of the vehicle are determined, and holding torque is generated based on position-compensated speed, slope, and mass. The slope component and mass component are determined based on the expected rollback amount according to the slope and mass to further improve rollback control, as described in the preceding paragraphs.

[0064] Another aspect of this disclosure includes a drivetrain controller for a vehicle, the vehicle including an electric generator operable to drive the wheels of the vehicle. The drivetrain controller includes processing instructions that, when executed, implement the above-described... Figure 3 The methods described and their variations.

[0065] Another aspect of this disclosure includes an electric vehicle comprising wheels powered by an electric generator. The electric vehicle includes a drivetrain controller communicatively coupled to various sensors and outputs a holding torque command implemented using an inverter to power the electric generator to generate the commanded torque. The sensors may include: speed sensors, motion sensors, brake sensors, brake pedal sensors, incline or gradient sensors, and any other sensors operable to determine the vehicle's position and speed, and optionally determine one or more of mass and gradient.

[0066] Electric vehicles may also include a brake pedal and a brake sensor that is communicatively connected to the drivetrain controller and operable to determine the desired amount of braking (e.g., pedal position). For example, the desired amount of braking to bring the vehicle to a stop from a low speed can be used to determine mass and gradient.

[0067] Electric vehicles may also include an accelerator pedal and an accelerator sensor that communicatively connects to the drivetrain controller and is operable to determine a desired acceleration metric based on pedal position. The desired acceleration metric can be used to determine a desired torque amount (positive or negative) in "one-pedal" mode. Therefore, positive acceleration and torque are desired when the pedal is depressed, while negative acceleration and torque are desired when the pedal is released, even if the brake pedal is not actuated. This gives the driver the ability to control vehicle speed using a single pedal.

[0068] Now, refer to Figures 4 to 14 This describes the implementation of the algorithm for the rollback control method. The algorithm uses proportional-plus-derivative control based on a combination of position and velocity to dispatch the reaction torque. Position alone generates the reaction torque to resist movement, where the permitted movement is a function of gradient and vehicle mass; however, since the torque must compensate for the movement plus vehicle momentum, it tends to fall short of the target. The velocity component addresses momentum. The velocity component is added earlier with the torque to stop the vehicle, and then the torque is added to hold the vehicle. Position is measured from a baseline sampling position. The baseline position can be sampled when the vehicle has been stopped for a certain period or when the vehicle's speed changes from positive to negative.

[0069] When the negative velocity is likely caused by oscillation rather than rollback, the algorithm disables the reaction torque. It should be understood that while the aforementioned and other examples are described with reference to a vehicle that wants to move forward but tends to roll backward due to gravity uphill, the same principle applies to a vehicle that wants to move in the opposite direction but tends to roll forward due to gravity downhill.

[0070] The algorithm determines the conditions indicating the probability of speed oscillations in an underdamped drivetrain. If there is a high probability of oscillating behavior, the algorithm reduces or disables the speed element for determining the reaction torque, since negative speed cannot be distinguished from failure to reach the target. If there is a low probability of oscillating behavior, the algorithm uses the full speed effect when determining the reaction torque. The algorithm can ramp up the gain component as a way to moderately switch between the two conditions. Then, using the position and the adjusted speed element from above, the algorithm determines the appropriate reaction torque to prevent or mitigate vehicle rollback.

[0071] On the controller side, this is equivalent to using position feedback with lead-compensation. The algorithm allows for unconstrained torque increases in response to detected rollback. Rate limiting is applied to zero torque as a way to interrupt the natural sine curve of the speed generated by the underdamped oscillation.

[0072] Now, the implementation will be described. Figures 4 to 14 Simulink simulation of the described algorithm. As is well known in the art, Simulink simulation can generate executable processing instructions for a controller. The controller generates commands for the electric generator to achieve the desired hill hold torque. Various logic sequences will be described in detail below to illustrate the operation of logic symbols in the Simulink simulator software. The following figures will be described solely based on their functionality, unless further clarification may aid understanding.

[0073] Reference Figure 4 Typically, the simulation includes: block 202, enabling ramp holding; block 204, disabling ramp holding; and 206, ramp holding torque (“HHT”). Ramp holding is also known as anti-rollback. Enabling ramp holding is a function that determines when the conditions for enabling HHT are met and refers to... Figure 5 The logic block 220 in the text is used to describe this. Figure 6 The function to disable ramp holding torque is described. Canceling ramp holding is a function that determines when the conditions for canceling HHT are met, and refers to... Figure 7 Describe it. The ramp holding torque is the function that determines the HHT, and refer to... Figures 8 to 14 The description is as follows: When HHT is disabled to prevent its generation, the cancellation of HHT means that the amount of generated HHT is reduced to zero.

[0074] The speed factor of the anti-rollback function is attenuated based on the possibility that negative speed is indeed due to oscillation rather than actual rollback. This attenuation is indicated by brake pedal activity and speed. Oscillation is caused by applying traction motor torque at one end of the drivetrain of a moving vehicle and applying a counterforce using the brakes at the other end. If the brakes are applied while the vehicle is moving or have recently been applied, negative speed is significantly more likely to indicate a failure to achieve the target. However, if the brakes are not applied or the vehicle was initially stationary, negative speed is more likely to indicate actual rollback. The speed attenuation factor is calculated based on the time since the brakes were released or the vehicle came to a stop. The time is an incrementing / decrementing counter timer without reset.

[0075] Reference Figure 5 Enabling hill hold includes: hill hold enable logic 220, and logic 228 configured to determine a speed coefficient or speed decay coefficient. A dwell timer 224 increments and decrements. This dwell timer increments when hill hold enable logic 220 is true, either when the brakes are released or during a stopped state of the vehicle as determined by stop vehicle logic 222. The `mcah_base_service_brake` parameter is provided by a brake sensor indicating when the brakes are on. The output of the "NOT" box indicates when the brakes are released, e.g., not "on". The output of stop vehicle logic 222 is true when the absolute speed of the vehicle is less than or equal to the zero speed tolerance. The `mcah_base_mach_int_speed` parameter indicates the speed. The `C_HLSI_HillHld_ZeroSpdTolerance` parameter indicates how much speed is acceptable still considered zero speed. Therefore, the speed sensing system can have a certain variation, and the zero speed tolerance determines when that variation is small enough to be insignificant. When any logic sequence is true, the OR box outputs a signal that causes the dwell timer 224 to increment. If the OR output is false, it causes the dwell timer 224 to decrement.

[0076] The speed coefficient 228 is normalized based on the maximum dwell time, which is the maximum output of the dwell timer 224, so that the timer's output varies from 0 to the maximum dwell time. Dividing the output by the maximum dwell time, the speed coefficient thus varies between 0 and 1.

[0077] Reference Figure 6 The disabling of the hill hold function describes the logic configured to disable the HHT. The hill hold torque is disabled if the function is (1) off, (2) the vehicle is not in direct drive mode, or (2) the speed exceeds the rollback range of interest (high).

[0078] The C_HLSI_HillHld_Torque_Priority parameter indicates whether the hill-holding torque function is enabled or disabled. If C_HLSI_HillHld_Torque_Priority is set to IGNORE, the hill-holding torque function is disabled. In the accompanying diagram, the symbol "~=" indicates the Boolean value "No", and the symbol "==" indicates the Boolean value "Yes". C_HLSI_HillHld_Torque_Priority can be determined by a switch operable by the vehicle operator.

[0079] The `mcah_base_vss_transmission` parameter indicates which drive mode the vehicle is set to. If `mcah_base_vss_transmission` is not set to `DIRECT_DRIVE`, hill-hold torque can be disabled. The `mcah_base_vss_transmission` parameter can be determined via a transmission mode selection switch that can be operated by the vehicle operator.

[0080] The `mcah_base_mach_int_speed` parameter is provided by the sensor to indicate speed. The `C_HLSI_HillHld_Disabl_RefSpeed` parameter indicates a reference speed at which the hill-hold torque function can be disabled; this reference speed is fast enough to indicate that rollback is impossible. Therefore, if `mcah_base_mach_int_speed` is greater than `C_HLSI_HillHld_Disabl_RefSpeed`, the hill-hold torque function can be disabled. If any of the three logic sequences input to the "OR" logic box is true, the HHT disable function outputs a disable signal 230.

[0081] Once the vehicle's speed exceeds the vehicle's reference speed, a rate limit reset signal is output to disable torque rate limiting.

[0082] Reference Figure 7The hill hold cancellation function describes the logic configured to cancel the HHT when it is no longer needed, such as during a rollback stop and when the brakes are reapplied. If the brakes are applied, battery power is not required to stop the vehicle. When the HHT is cancelled, the applied HHT hill is reduced to zero. The HHT cancellation timer 240 increments when certain conditions are met. These conditions are met when the holding torque is greater than zero, the vehicle stop logic 222 is true, and the brakes have been applied. If the conditions are met, the AND logic block is true, allowing the HHT cancellation timer 240 to increment until the C_HLSI_HillHold_Cancel_Time limit. When the HHT cancellation timer 240 times out at C_HLSI_HillHold_Cancel_Time, the HHT cancellation logic outputs a true HHT cancellation signal 242.

[0083] Figure 8 The position-compensated velocity 258, based on a velocity coefficient 228 attenuation, is depicted (see [reference]). Figure 9 The logic calculates the ramp holding torque and outputs the HHT 208 signal. The speed-torque mapping is provided to lookup table 254. Attenuation position compensation speed determines the torque in the lookup table. The lookup table can be determined empirically. For example, the table can be provided with information about the driven vehicle and the impact of the HHT sensed by the vehicle's occupant, indicating whether the response is too aggressive or could be more aggressive. The lookup table is then updated. Different lookup tables can be determined and used for different vehicle types, weights, road slopes, etc. The output of this table is HHT 255.

[0084] If HHT cancellation signal 242 is true, then the rate limiting logic 256 will be cancelled (see reference). Figure 13 This can be applied to HHT255 to remove rate limiting (HHT 257). The rate limiting logic 258 can also be used (see...). Figure 14 Apply to HHT 255 or 257 to generate HHT 208.

[0085] HHT is scheduled based on the combined motor position and speed. This roughly corresponds to advance compensation position (the faster the rollback, the lower the position before applying reverse torque). The position gain determines the relative contribution of the two components. Furthermore, the speed component carries a decay coefficient based on the most recent brake pedal activity. Lack of braking or movement will generate a speed coefficient of 1.0. Current active braking will generate a speed coefficient of 0.0.

[0086] Figure 9 The position compensation velocity logic is described, which is based on position baseline 256 (see Figure 10The position compensation speed 258 is determined by the vehicle's speed and position baseline 256. This value is calibrated or scaled by multiplying the position baseline 256 by a gain factor. The vehicle's speed is attenuated by multiplying by a speed factor 228. The products of the calibrated position baseline and the attenuation speed are added together, and the sum is output as the position compensation speed 258 until the HHT cancellation signal 242 is true, in which case the position compensation speed 258 is set to zero.

[0087] Figure 10 The position baseline logic is described, which is based on vehicle movement and vehicle stopping, or stop confirmation parameter 280 (see Figure 11 The position baseline 270 is determined by measuring the position from the position baseline. The position is determined when the vehicle stops. In this embodiment, the position is determined based on the motor angle (e.g., by counting gear teeth). The position baseline logic includes a latch that latches when 1) the vehicle stop parameter 280 is true, or 2) the motor speed is negative and the previous speed was positive. If 1) the motor moves and senses speed, or causes the gear to shift so that the vehicle is no longer in direct drive, or HHT cancellation 242 is true, the latch is reset. A logic switch is connected to the latch output.

[0088] When the latch is set, the switch output is the previous value, which is the value of the motor angle captured when the vehicle stops and the motor speed changes from positive to negative. When the latch is reset, the switch output is the current value of the motor angle. In other words, the position baseline changes constantly until the latch is set, at which point the position is captured and maintained until the latch is reset.

[0089] Because the position baseline is determined based on the motor angle, which changes from 360 degrees to 0 degrees per revolution, wrap-around logic 290 is used to convert the angle into position (see...). Figure 12 If the location baseline is tracked by other means, then wrap logic is not necessary.

[0090] Figure 11A stop detection logic is described, which determines the stop confirmation parameter 280 based on a dwell timer 278 provided to avoid adding another calibration. A 100ms timer is used to determine if the speed is zero or close to zero. The speed tolerance is calibrable because the motor speed may oscillate when stopped, even if the wheels appear not to be moving. The counter increments when the speed is zero or close to zero and decrements when the speed is not zero or close to zero, and a stop has not yet been confirmed. The counter is reset only when the speed is within a predetermined range, where rollback is of interest. The speed is zero or close to zero when the zero speed tolerance parameter exceeds the vehicle's speed. The dwell timer 278 is incremented until it reaches its limit, for example, 0.1 seconds, at which point the stop confirmation parameter 280 becomes true.

[0091] Figure 12 A wraparound logic 290 is described to determine the compensated position parameter 271 based on the angular position of the motor. The motor angle is measured in revolutions and is defined only for a single revolution. To prevent discontinuities, the wraparound logic checks for sudden changes between values ​​close to 1 and maintains a revolution counter. For very low speeds, it may be possible to count only a small number of revolutions. The wraparound logic identifies an increase or decrease in wraparound by comparing the motor angle to a previous value. For example, if the angle is less than 0.2 and the previous angle is greater than 0.8, an increase in wraparound is determined, and the increase wraparound switch output is set to 1. If the angle is greater than 0.8 and the previous angle is less than 0.2, a decrease in wraparound is determined, and the decrease wraparound switch output is set to -1. If the wraparound is not decreased, the decrease wraparound switch output is set to the output of the increase wraparound switch output, which is set to 1 if the wraparound is increased, or 0 if the wraparound is not increased. Therefore, the position parameter 271 is generated by incrementing by 1 each time the gear completes one revolution in the positive direction (an angle varying between [0, 1]) and by incrementing by -1 each time the gear completes one revolution in the negative direction. Since the motor position is critical only for anti-rollback capability, the bookkeeping is limited to its associated lower speed. For the remainder of this time, the rev counter is reset to zero. If anti-rollback is never enabled or is disabled, the baseline position tracks the actual position, and the unwinding logic is reset to zero. Therefore, the compensated position becomes zero and HHT becomes zero.

[0092] Rollback control limits the rate at which the ramp-holding torque returns to zero. This is intended to mitigate the possibility of applied torque contributing to drivetrain oscillations by limiting the rate at which any sinusoidal oscillations are interrupted on one side. Increases in output are unrestricted (input > output).

[0093] Figure 13 HHT cancellation rate limiting logic 256 is described, which limits the rate at which the HHT returns to zero when it is cancelled. The rate limiting can be faster than the normal torque rate limiting and is designed to smoothly transition the HHT from its positive value (HHT cancellation 242) to zero. A rate limiting timer is used to limit the torque. The timer's decreasing input is set according to a torque cancellation rate parameter. Logic is added to ensure that the input receives a negative value. The timer's output follows the torque until the torque decreases faster than the torque cancellation rate parameter, at which point the output is the value of the torque cancellation rate parameter. Similarly, if the torque increases, the timer's output follows the torque until the torque increases faster than a rate equal to 20,000, which does not impose a limitation in practical applications.

[0094] Figure 14 HHT disengagement rate limiting logic 258 is described, which limits the rate at which the HHT returns to zero when the HHT is disengaged but not cancelled. This logic is the same as the HHT cancellation rate limiting logic, but the limit is set based on a torque disengagement rate parameter instead of a torque cancellation rate parameter. The HHT disengagement rate limiting logic is used to mitigate the possibility that the HHT may contribute to drivetrain oscillations when disengaged.

[0095] Figure 15 A block diagram of a vehicle 100 with a drivetrain 101 and an electric generator 102 is depicted. As previously mentioned, the drivetrain controller 40 has drivetrain logic or processing instructions 42 consistent with the embodiments described above for controlling rollback, and a brake sensor 44, which are operable to process inputs from various speeds, transmission modes, gradients, motor movements, and angles. The processing instructions may be embedded in the drivetrain controller 42 or may be embedded in a memory accessible by the drivetrain controller 42. An inverter 118 is also shown. The torque command generated by the processing instructions 42 is used by the inverter 42 to generate a motor voltage so that the electric generator 102 generates a command torque. The electric generator 102 and the inverter 118 can also convert the vehicle's kinetic energy into electrical energy during braking (deceleration or rollback relief). The converted electrical energy is stored in energy storage devices (such as a battery 20, a supercapacitor, and a high-speed flywheel) to extend the vehicle's driving range. Therefore, it is desirable to apply regenerative braking whenever possible. The vehicle also includes a hydraulic or pneumatic braking system that works in conjunction with regenerative braking.

[0096] Maintaining holding torque indefinitely may be a concern. For example, prolonged motor torque without movement can cause the motor to overheat. Phases of the motor may be damaged, and consequently, the motor may be derated and impair driving performance. Furthermore, it is advantageous to remind the driver that holding torque is not braking, so that they do not treat it in this way and leave the driver's seat without taking more permanent safety measures, such as applying the manual brakes.

[0097] One option for maintaining the holding torque indefinitely (provided the conditions are right) is to maintain the holding torque for a fixed period of time and then release it. This solution has some potential drawbacks. For example, a complete release of the holding torque can lead to uncontrolled rollback, which can be problematic in congested areas. Partial or gradual release of the holding torque can have a similar effect, differing only in the slower timescale.

[0098] In some implementations, the holding torque is maintained for a predetermined time and then released. Release can be managed in the same manner as the cancellation of the holding torque (as previously discussed), including reducing the holding torque to zero torque and imposing a limit on the rate of decrease of the holding torque to provide a smooth transition. Release includes, according to reference... Figures 4 to 14 The described holding torque algorithm controls the reset of the control variables. After release, the holding torque can be applied repeatedly by detecting rollback and generating a new holding torque based on the characteristics sensed during the rollback detection after release.

[0099] Figure 16This is a graph depicting the vehicle's position over time. Events E1 to E6 are shown on curve 300 to illustrate the effect of the holding torque during the first application or cycle 310 of the holding torque. A second holding torque cycle 312 and a third holding torque cycle 314 are also shown; in this embodiment, the second and third holding torque cycles are equal to the first cycle 310, with a constant predetermined holding duration between them. At 2.5 seconds, the first event (E1) corresponds to the vehicle rolling back from a first position 301, characterized by a negative vehicle position. At 5.0 seconds, the second event (E2) indicates the effect of applying the holding torque: resisting rearward movement at the second position 302, and at E3, reversing that rollback distance by returning the vehicle to the third position 303. The fourth event (E4) indicates the predetermined duration of the holding torque after the vehicle moves to the third position 303, and is subsequently released at event five (E5) from the fourth position 304, allowing the vehicle to roll back to the fifth position 305. The sixth event E6 corresponds to the reapplication of the holding torque to move the vehicle to the sixth position 306, at which point the process is repeated, and in the seventh position 307, the holding torque is released. In the eighth position 308, the holding torque is reapplied and the vehicle moves to the ninth position 309.

[0100] In the preceding description, positions 302, 305, and 308 are the same. In the variant of this embodiment described below, positions 302, 305, and 308 are different. In this variant, positions 303, 306, and 309 are also different.

[0101] In the preceding description, positions 303 and 304, as well as 306 and 307, are identical, indicating that the torque is kept constant during a predetermined period of time. In a variant of this embodiment, by allowing a small amount of rollback and potentially changing the power supply phase of the motor, the vehicle is allowed to move slightly from position 303 to position 304, and from position 306 to position 307.

[0102] Figure 17 It is a graph depicting the vehicle's position over time (shown as follows) Figure 16 Curve 300 is shown in the diagram, and curve 320 is also shown depicting the amount of holding torque required to hold the vehicle and achieve the vehicle position depicted by curve 300. At 322, the holding torque reaches its maximum value, reflecting the energy required to stop the vehicle. At 324, the holding torque decreases from its maximum value but is sufficient to keep the vehicle stationary. Then, at 326, the holding torque is released, which allows the vehicle to roll back.

[0103] although Figure 16The plotted graph illustrates events E3 and E4, but it can also trigger the release of holding torque from event E2, as well as the application of holding torque from E2 for a predetermined time.

[0104] The preset time can also be varied between cycles. The preset time can be changed based on the amount of holding torque initially applied at E2 or E3. For example, the preset time can be decreased or increased.

[0105] Furthermore, it is not necessary to apply the same amount of holding torque each time. The amount of holding torque in the second cycle after the first release can be adjusted based on data obtained during the application of the first holding torque. Therefore, it may be desirable to apply the holding torque required to stop the vehicle more quickly to reduce the amount of torque required to stop the vehicle, which will reduce heat generation in the motor. The amount of holding torque used to maintain a stationary position will be the same because the mass and gradient do not change. The same effect can be achieved by applying the holding torque based on the start of the first cycle without waiting to measure the position or acceleration, because the vehicle's mass, gradient, and reaction force will be the same. Applying the holding torque more quickly than in the previous cycle will also have the effect that the vehicle will roll back less than in the previous cycle, which can cause different phases of the motor to be energized to hold the vehicle, thus distributing heat to different phases in different cycles. The degree of fasterness and rollback that allows this effect to be achieved can be determined empirically and mapped or calculated based on the transmission ratio of the vehicle's drivetrain and the configuration of the motor. Essentially, the inches of wheel rotation are related to the rotation of the motor, which can be related to the position of the motor's magnetic poles, thus making the wheel movement related to the position of the magnetic poles.

[0106] Furthermore, the vehicle can be allowed to slow down after maintaining a stationary position. Unlike maintaining a stationary position for a predetermined time, a more gradual change in position can be allowed during the predetermined time period, compared to the removal of holding torque. The slowing amount can be designed to allow a transition from one pole of the motor to another, thereby distributing heat.

[0107] As described above, considering the motor heating caused by repeatedly returning to the same stationary position, the initial position can be changed (incremented / decremented) at the end of each rollback cycle / event (e.g., 304, 306, 309). The position increment can be positive (always moving slightly forward for each event) or negative (always slightly less than returning to the original position for each event). Figure 18 This is a graph depicting curve 340, which shows the change of the vehicle's position over time, including: three holding cycles 342, 344, and 346, and three holding positions decreasing from the initial position 343, 345, and 347. These holding positions illustrate the holding torque relative to... Figure 16 and Figure 17The reduction in holding torque is shown to bring the vehicle to a stop before reaching the initial position 341. Holding position 343 is one inch less than position 341, holding position 345 is one inch less than holding position 343, and holding position 347 is one inch less than holding position 345. The change in holding position should result in power being supplied to different motor phases for the holding torque once the vehicle is stationary. A one-inch position change may seem small, but given tire size and drivetrain ratios, it can be equivalent to an amplified rotation of the drive motor (typically one inch can be 10° or more of a rotation of the drive motor).

[0108] As described above, the vehicle rollback is constrained while allowing it to roll back an unlimited number of times. Advantageously, this movement is constrained to back-and-forth movement within the same confined space, and there is no continuous operation while the stationary motor provides significant torque. The torque is sustained for no more than a set number of seconds. Afterward, the torque is released, and the motor windings are allowed to cool.

[0109] The operator was not given permanent instructions. With limited rollback allowed at fixed but rather short repetition intervals, for more persistent operating modes, the operator will never let their guard down and misunderstand the anti-rollback holding force.

[0110] For ease of explanation, the embodiments, figures, and examples suggest the expected forward movement, and rollback is "moving backward." These directions are relative to the expected direction of movement. If the vehicle is in drive mode, the expected direction is forward, and rollback means moving backward. On the other hand, if the vehicle is in reverse mode and stopped on a downhill slope, all the concepts described herein apply, and rollback means moving forward. In other words, rollback means moving in the opposite direction to the vehicle's expected movement.

[0111] The torque, as described in the rollback description, can be cancelled and then re-enabled for other situations, such as low-speed vehicle easing logic, where the applied easing torque is sufficient to hold the vehicle against gravity on a slope but insufficient to propel it forward. Similarly, the easing torque can be disabled and re-enabled for a predetermined time.

[0112] Many aspects of this disclosure are described in terms of sequences of actions to be performed by a controller or other hardware capable of executing programmable instructions. These components may be implemented in a controller of a drivetrain system, such as a drivetrain control module or unit (DCM or DCU), or in a controller separate from and communicating with the DCM / DCU. In embodiments, the drivetrain controller and / or DCM / DCU may be part of a controller area network (CAN), in which controllers, sensors, and actuators communicate via digital CAN messages. It will be appreciated that, in various embodiments described, the various actions for implementing the control strategy may be performed by dedicated circuitry (e.g., discrete logic gates interconnected to perform dedicated functions), program instructions such as program modules executed by one or more processors (e.g., a central processing unit (CPU) or microprocessor), or a combination of both, all of which may be implemented in the hardware and / or non-transitory computer-readable instructions of the ECM / ECU and / or other controllers or multiple controllers. The logic of embodiments consistent with this disclosure can be implemented using any type of appropriate hardware and / or non-transitory computer-readable instructions, some of which reside in the form of a computer-readable storage medium on which control algorithms (such as the executable logic and instructions disclosed herein) are recorded, and can be programmed, for example, to include one or more one-dimensional or multi-dimensional lookup tables and / or calibration parameters. Therefore, as used herein, the term "logic" includes software and / or firmware comprising processing instructions that execute on one or more programmable processors, application-specific integrated circuits, field-programmable gate arrays, digital signal processors, hardwired logic, or combinations thereof, which may be referred to as a "controller." Non-transitory machine-readable media including logic can also be considered to be embodied within any tangible form of computer-readable carrier (such as solid-state memory), containing a set of appropriate computer instructions and data structures that will cause the processor to perform the techniques described herein. Computer-readable media may include: random access memory (RAM), read-only memory (ROM), erasable programmable read-only memory (EPROM or flash memory), optical fiber and portable optical disc read-only memory (CD-ROM), or any other solid-state, magnetic, and / or optical disc media capable of storing information. Therefore, the various aspects can be implemented in many different forms, and all of these forms are conceived to be consistent with this disclosure.

[0113] In some embodiments, the drivetrain controller 40 forms part of a processing subsystem that includes one or more computing devices having memory, processing, and communication hardware. The drivetrain controller 40 and its functions can be implemented in any known manner. For example, the drivetrain controller 40 can be a single device or a distributed device, and the controller's functions can be executed by hardware and / or as computer instructions on a non-transitory computer-readable storage medium.

[0114] In some embodiments, the drivetrain controller 40 includes one or more modules that functionally perform the operations of the controller. The description herein, including modules, emphasizes the structural independence of certain aspects of the controller 40 and illustrates a grouping of the controller's operations and responsibilities. Other groups performing similar overall operations are understood to be within the scope of this application. Modules may be implemented in hardware and / or implemented as computer instructions on a non-transitory computer-readable medium, and modules may be distributed across various hardware or computer-based components.

[0115] Examples and non-limiting module implementation components include: sensors that provide any value as defined herein, sensors that provide any value as a precursor to the value defined herein, data link and / or network hardware (including communication chips, oscillating crystals, communication links, cables, twisted pairs, coaxial cables, shielded cables, transmitters, receivers, and / or transceivers), logic circuits, hardwired logic circuits, reconfigurable logic circuits in a specific non-transient state configured according to the module specification, any actuators (including at least electric actuators, hydraulic actuators, or pneumatic actuators), solenoids, operational amplifiers, analog control components (springs, filters, integrators, adders, dividers, gain components), and / or digital control components.

[0116] As used herein, the transitional term "comprising" or "containing" is inclusive or open-ended and does not exclude additional, unspecified components or method steps. In contrast, the transitional term "consisting of" is a closed term that does not allow the addition of unspecified terms.

[0117] While this disclosure has been described as having an exemplary design, further modifications may be made to this disclosure within its spirit and scope. Therefore, this application is intended to cover any variations, uses, and alterations of this disclosure utilizing its general principles. Furthermore, this application is intended to cover such modifications to this disclosure that fall within the known or customary practice in the art to which this disclosure pertains and fall within the limitations of the appended claims.

Claims

1. A method for reducing the rollback of an electric vehicle, the method comprising the following steps: Determine the position baseline of the electric vehicle; The position compensation speed of the electric vehicle is determined based on the position baseline. The holding torque is determined based on the position compensation speed; and Generate a command to apply the holding torque to the electric generator of the electric vehicle. Wherein, the position baseline includes the first position of the electric vehicle; The method further includes allowing the electric vehicle to roll to a second position, stopping the rolling at the second position by the holding torque, and continuing to apply the holding torque to counteract the rolling until the electric vehicle stops at a third position; and The third position is equal to the first position.

2. The method according to claim 1, wherein, The step of determining the position baseline includes: determining the stopping state or speed polarity change of the electric vehicle, wherein the position baseline is the position of the electric vehicle when the stopping state or speed polarity change is determined.

3. The method according to claim 2, wherein, The step of determining the stopping status of the electric vehicle includes: determining the time the electric vehicle's speed is less than or equal to the absolute zero speed tolerance and reaches zero speed dwell time.

4. The method according to claim 1, wherein, The holding torque is based on the product of the position compensation speed and the speed coefficient.

5. The method according to claim 4, wherein, The position compensation speed of the electric vehicle includes the sum of a position baseline component and a decay speed component, wherein the decay speed component includes the product of the electric vehicle's speed and the speed coefficient.

6. The method according to claim 5, wherein, The holding torque includes canceling the rate limit.

7. The method according to claim 6, wherein, The cancellation rate limit decreases over time.

8. The method according to any one of claims 4 to 7, wherein, The speed coefficient includes a normalized dwell time based on a brake release event or when the speed of the electric vehicle is less than the absolute zero speed tolerance.

9. The method according to claim 8, wherein, The velocity coefficient varies between 0 and 1.

10. The method according to claim 8, wherein, The normalized dwell time includes the ratio of dwell time based on the brake release event or the electric vehicle's speed being less than the absolute zero speed tolerance.

11. The method according to claim 8, wherein, The speed coefficient decreases if the speed exceeds the absolute zero speed tolerance or if the brake is reapplied.

12. The method according to any one of claims 4 to 7, wherein, The speed coefficient is proportional to the dwell time that begins when the brakes of the electric vehicle are released or when the speed of the electric vehicle is less than the absolute zero speed tolerance.

13. The method according to claim 1, further comprising the following steps: If the speed of the electric vehicle exceeds the cancellation speed, the holding torque is disengaged.

14. The method according to claim 13, wherein, The step of disengaging the holding torque includes reducing the holding torque to zero.

15. The method according to claim 14, wherein, The step of disengaging from the holding torque includes: rate limiting the rate at which the holding torque decreases to zero.

16. The method according to claim 1, further comprising the following step: The inclination of the electric vehicle is determined, wherein the holding torque is also related to the inclination gain corresponding to the inclination.

17. The method according to claim 1, further comprising the following steps: The mass of the electric vehicle is determined, wherein the holding torque is also related to the mass gain corresponding to the mass.

18. The method according to claim 1, further comprising the following step: The inclination and mass of the electric vehicle are determined, wherein the holding torque is also related to the mass gain corresponding to the mass and the inclination gain corresponding to the inclination.

19. The method according to claim 1, further comprising the following step: Brake pressure feedback, wherein the holding torque is related to the brake pressure feedback component.

20. The method according to claim 1, further comprising the following steps: The slope is determined, and the mass of the electric vehicle is determined based on the slope, wherein the holding torque is also related to a mass component based on the mass.

21. A method for reducing the rollback of an electric vehicle, the method comprising the following steps: Determine the position baseline of the electric vehicle; The position compensation speed of the electric vehicle is determined based on the position baseline. The holding torque is determined based on the position compensation speed. as well as Generate a command to apply the holding torque to the electric generator of the electric vehicle. The step of determining the position compensation speed of the electric vehicle includes: adding the position baseline component to the attenuation speed component. The attenuation speed component includes the product of the electric vehicle's speed and speed coefficient.

22. The method according to claim 21, wherein, The holding torque is based on the product of the position compensation speed and the speed coefficient.

23. The method according to claim 21 or 22, wherein, The speed coefficient includes a normalized dwell time based on a brake release event or when the speed of the electric vehicle is less than the absolute zero speed tolerance.

24. The method according to claim 23, wherein, The velocity coefficient varies between 0 and 1.

25. The method according to claim 23, wherein, The normalized dwell time includes the ratio of dwell time based on the brake release event or the electric vehicle's speed being less than the absolute zero speed tolerance.

26. The method according to claim 23, wherein, The speed coefficient decreases if the speed exceeds the absolute zero speed tolerance or if the brake is reapplied.

27. The method according to claim 21 or 22, wherein, The speed coefficient is proportional to the dwell time that begins when the brakes of the electric vehicle are released or when the speed of the electric vehicle is less than the absolute zero speed tolerance.

28. The method according to claim 21 or 22, wherein, The position baseline includes a first position of the electric vehicle, and the method further includes the steps of: allowing the electric vehicle to roll to a second position, stopping the rolling at the second position using the holding torque, and continuing to apply the holding torque to resist the rolling until the vehicle stops at a third position.

29. The method according to claim 28, wherein, The third position is different from the first position.

30. The method according to claim 28, wherein, The third position is the same as the first position.

31. The method according to claim 28, wherein, The holding torque changes between the first position and the third position.

32. The method according to claim 28, further comprising the following step: The holding torque is applied for a predetermined time, wherein the electric vehicle is in the third position at the beginning of the predetermined time and in the fourth position at the end of the predetermined time.

33. The method according to claim 32, wherein, The scheduled time varies between rollback cycles.

34. The method according to claim 32, wherein, The third position is the same as the fourth position.

35. The method according to claim 32, wherein, The third position is different from the fourth position.

36. The method according to claim 35, wherein, In the third position, one phase of the electric generator is energized, and the method further includes the step of determining that the difference between the third position and the fourth position is sufficient to de-energize the phase and energize different phases of the electric generator.

37. A drivetrain controller for an electric vehicle, the electric vehicle including an electric generator operable to drive the wheels of the electric vehicle, the drivetrain controller including processing instructions that, when executed, implement the method according to any one of claims 1 to 36.

38. An electric vehicle, the electric vehicle comprising: Wheel, wheel support frame; An electric generator, which is operable to drive the wheels; as well as The drivetrain controller according to claim 37.

39. The electric vehicle of claim 38, further comprising a sensor communicatively connected to the drivetrain controller and operable to sense movement of the electric vehicle.

40. The electric vehicle of claim 38, further comprising a brake pedal and a brake sensor, the brake sensor being communicatively connected to the drivetrain controller and operable to determine the pressure applied to the brake pedal.

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