Torque vectoring control system and method for in-wheel-motor four-wheel-drive vehicle

Abstract

Disclosed in the present application is a torque vectoring control system for an in-wheel-motor four-wheel-drive vehicle. In the torque vectoring control system, a driving style identification module determines the driving style of a driver during the travel of an in-wheel-motor four-wheel-drive vehicle; a vehicle state sensing module acquires a steering wheel angle and a longitudinal vehicle speed in real time, and performs fault state monitoring on the in-wheel-motor four-wheel-drive vehicle; a vehicle motion control module calculates an ideal yaw rate target of the in-wheel-motor four-wheel-drive vehicle; and a torque vectoring control module calculates an additional yaw moment on the basis of the ideal yaw rate target and an actual yaw rate, executes a corresponding fault handling strategy on the basis of a fault state monitoring result, and then performs torque distribution on the basis of the additional yaw moment combined with the fault state monitoring result to generate an additional driving torque and an additional braking torque of each wheel. The present application realizes self-adaptive yaw stability control for drivers having different driving styles.

Description

Torque vector control system and method for four-wheel drive vehicles with in-wheel motors CROSS-REFERENCE TO RELATED APPLICATIONS

[0001] This application claims priority to Chinese patent application No. 202410206186.X filed on February 26, 2024, the entire contents of which are incorporated herein by reference. Technical Field

[0002] The present application relates to the field of pure electric vehicle control technology, and specifically to a torque vector control system and method for a four-wheel drive vehicle with a hub motor. Background Art

[0003] The driving process can generally be broken down into a series of typical driving events. A driver's driving style refers to their behavioral preferences within this set. Because driver behavior is influenced by numerous subjective factors, research methods are complex. Currently, driving style classification criteria generally include those based on energy consumption and those based on driver misbehavior.

[0004] Currently, for pure electric vehicles powered by four-wheel hub motors, each in-wheel motor can be independently controlled, distributing different driving and braking torques to the corresponding wheel. Torque vectoring significantly improves vehicle stability by actively controlling the torque distribution between wheels, generating a yaw moment without sacrificing longitudinal speed.

[0005] Currently, the yaw stability control of pure electric vehicles driven by four-wheel hub motors is mainly vehicle stability control, without taking maneuverability as an optimization goal to cater to the driving needs of drivers with different driving styles, making it impossible to achieve adaptive yaw stability control of pure electric vehicles driven by four-wheel hub motors. Summary of the Invention

[0006] The purpose of this application is to provide a torque vector control system and method for a four-wheel-drive vehicle driven by a hub motor. This application implements adaptive yaw stability control for drivers with different driving styles by performing yaw stability control on a pure electric vehicle driven by four hub motors taking into account the driving style, thereby making the yaw stability control of the pure electric vehicle driven by four hub motors intelligent.

[0007] To achieve this purpose, the in-wheel motor four-wheel drive vehicle torque vector control system designed in this application includes: a driving style identification module for determining the driver's driving style during the driving of the in-wheel motor four-wheel drive vehicle;

[0008] The vehicle status perception module is used to obtain the steering wheel angle, vehicle longitudinal speed and vehicle lateral acceleration in real time, and to monitor the fault status of hub motor four-wheel drive vehicles;

[0009] The vehicle motion control module is used to select a target stability factor based on the determined driver's driving style, and calculate the ideal yaw rate target of the hub motor four-wheel drive vehicle based on the target stability factor, the real-time steering wheel angle and the vehicle's longitudinal speed;

[0010] The torque vector control module is used to calculate the additional yaw torque based on the ideal yaw rate target and the actual yaw rate, and to execute the corresponding fault handling strategy according to the results of the fault status monitoring. Then, the torque is distributed based on the additional yaw torque combined with the fault status monitoring results to generate the additional driving torque and additional braking torque for each wheel.

[0011] The driving style identification module selects driving feature quantities and uses a BP neural network to classify the driving feature quantities to obtain the current driver's driving style. The driving feature quantities include: maximum lateral acceleration, variance of the product of steering wheel angle and vehicle speed, and maximum product of steering wheel angle and vehicle speed.

[0012] The specific method of the driving style identification module using the BP (Back Propagation Neural Network) neural network to classify driving styles based on driving feature quantities is as follows:

[0013] Based on fuzzy C-means clustering, the driving characteristics are used to classify the driving styles, including a stable driving style, a standard driving style, an aggressive driving style, and a sporty driving style;

[0014] Select a single hidden layer BP neural network to build a driving style recognition model;

[0015] Determine the number of neurons in the input layer, output layer, and hidden layer of the driving style recognition model;

[0016] The softmax function is selected as the activation function of the output layer of the driving style recognition model. The driving feature quantity is transmitted to the driving style recognition model for driving style recognition, and the driving style with the maximum probability is output as the final recognition result.

[0017] The specific method for the vehicle motion control module to select the target stability factor based on the determined driver's driving style is as follows:

[0018] If the driving style recognition module determines that the current driver's driving style is a stable driving style or a standard driving style, the stability factor is determined. for:

[0019]

[0020] Where: m is the total mass of the hub motor four-wheel drive vehicle; a and b are the distances from the center of mass of the hub motor four-wheel drive vehicle to the front and rear axles respectively; 、 are the front and rear axle lateral stiffness of the hub motor four-wheel drive vehicle respectively; L is the wheelbase of the hub motor four-wheel drive vehicle;

[0021] If the driving style recognition module determines that the current driver's driving style is an aggressive driving style or a sporty driving style, the stability factor is determined. for:

[0022]

[0023] Where C k0 and C k1 are the gains of the transfer function when the driver enters and exits the curve, respectively; τ0 and τ1 are the time constants of the transfer function when entering and exiting the curve, respectively; When it is greater than 0, it means exiting the curve. When it is less than 0, it means entering a curve; represents the steering wheel angular velocity, δ sw Indicates the steering wheel angle.

[0024] The vehicle motion control module is based on the stability factor And the steering wheel angle obtained in real time by the vehicle state perception module and vehicle longitudinal speed Calculate the ideal yaw rate target for a hub motor 4WD vehicle The specific method is:

[0025] Determining different driver control objectives based on different driver driving styles includes: when the driving style identification module determines that the current driver driving style is a smooth driving style or a standard driving style, determining the control objective to be a torque vectoring control strategy with stability as the primary objective; or when the driving style identification module determines that the current driver driving style is an aggressive driving style or a sporty driving style, determining the control objective to be a torque vectoring control strategy with maneuverability as the primary objective and stability as the secondary objective;

[0026] The torque vector control strategy based on the stability objective includes: solving the ideal yaw rate target based on the understeering characteristic ;

[0027]

[0028] in, and are the front and rear wheel cornering stiffness, is the moment of inertia of the vehicle around the Z axis, a and b are the distances from the center of mass to the front and rear axles, respectively. is the vehicle's natural frequency, is the vehicle's damping ratio, m is the total mass of the hub motor four-wheel drive vehicle, L is the vehicle's wheelbase, is the longitudinal speed, is the lead correction amount, is the vehicle's natural frequency, represents the transfer function, is the front wheel turning angle;

[0029] The torque vectoring control strategy, which focuses on maneuverability and also takes stability into consideration, includes: stability factors corresponding to the cornering and exiting characteristics of professional drivers Use the above formula to solve the ideal yaw rate target ;

[0030] Stability factor based on the cornering and exiting characteristics of professional drivers Solving for the ideal yaw rate target When the driver with the aggressive and sporty driving style increases the oversteer degree when the hub motor four-wheel drive vehicle enters the corner;

[0031] Maintaining neutral steering characteristics when a driver with an aggressive or sporty driving style controls a hub motor four-wheel drive vehicle during a turn;

[0032] Increases understeer when a driver with an aggressive or sporty driving style maneuvers a hub motor 4WD vehicle out of a corner.

[0033] Beneficial effects of this application:

[0034] This application uses a driving style identification module to determine the current driver's driving style. Based on the driving style identification results, the vehicle motion control module implements a torque vector control strategy for the in-wheel motor four-wheel drive vehicle that prioritizes stability to meet the needs of smooth and standard drivers, or a torque vector control strategy that prioritizes maneuverability while also ensuring safety to meet the needs of aggressive and sporty drivers. This improves the adaptability of the in-wheel motor four-wheel drive vehicle's torque vector control. Furthermore, this application enhances the fault tolerance and robustness of the torque vector control system by providing a fault handling module. BRIEF DESCRIPTION OF THE DRAWINGS

[0035] Figure 1 is a schematic diagram of the structure of this application; DETAILED DESCRIPTION

[0036] The following is a further detailed description of this application in conjunction with the accompanying drawings and specific technical solutions:

[0037] Technical Solution 1

[0038] As shown in FIG1 , the torque vector control system of the in-wheel motor four-wheel drive vehicle includes: a driving style identification module for determining the driver's driving style during the driving process of the in-wheel motor four-wheel drive vehicle, and adjusting the control method accordingly to improve the adaptability of the torque vector control of the in-wheel motor four-wheel drive vehicle;

[0039] The vehicle status perception module is used to obtain the steering wheel angle, vehicle longitudinal speed and vehicle lateral acceleration in real time, and to monitor the fault status of hub motor four-wheel drive vehicles;

[0040] The vehicle motion control module is used to select a target stability factor based on the determined driver's driving style, and calculate the ideal yaw rate target of the hub motor four-wheel drive vehicle based on the target stability factor, the real-time steering wheel angle and the vehicle's longitudinal speed;

[0041] The torque vectoring control module is used to calculate the additional yaw torque based on the ideal yaw rate target and the actual yaw rate, and to implement the corresponding fault handling strategy based on the results of the fault status monitoring. Then, the torque is distributed based on the additional yaw torque and the fault status monitoring results to generate the additional driving torque and additional braking torque for each wheel. The above-mentioned actual yaw rate is obtained in real time by the vehicle status perception module.

[0042] In the above technical solution, the driving style identification module selects driving characteristics and uses a BP neural network to classify the driving characteristics to determine the current driver's driving style. The driving characteristics include: maximum lateral acceleration, the variance of the steering wheel angle and vehicle speed product, and the maximum steering wheel angle and vehicle speed product. After selecting the driving characteristics, the BP neural network can identify the current driving style online in real time based on the driving characteristics and implement corresponding control strategies to achieve dynamic decision-making. The BP neural network is selected because it can better handle nonlinear problems than other clustering methods, making it more suitable for online driving style identification.

[0043] In the above technical solution, the specific method of the driving style identification module using the BP neural network to classify the driving style based on the driving feature quantity is:

[0044] Based on fuzzy C-means clustering, the driving characteristics are used to classify the driving styles, including a stable driving style, a standard driving style, an aggressive driving style, and a sporty driving style;

[0045] Select a single hidden layer BP neural network to build a driving style recognition model;

[0046] Determine the number of input layer neurons, output layer neurons, and hidden layer neurons for the driving style recognition model. In this technical solution, the number of input layer neurons is 3, corresponding to three driving characteristics (maximum lateral acceleration, variance of the product of steering wheel angle and vehicle speed, and maximum product of steering wheel angle and vehicle speed). The number of output layer neurons is 4, corresponding to four driving styles (smooth driving style, standard driving style, aggressive driving style, and sporty driving style). The number of hidden layer neurons is 10, determined based on relevant empirical formulas and ranging from 3 to 11. After actual parameter adjustment, it was determined to be 10.

[0047] The softmax function is selected as the activation function for the output layer of the driving style recognition model. Driving characteristics are fed into the model for driving style recognition, and the driving style with the highest probability is output as the final recognition result. The larger the maximum lateral acceleration, the maximum steering wheel angle and vehicle speed product, and the variance of the steering wheel angle and vehicle speed product, the more aggressive the driving style. Using a BP neural network for online recognition reduces the number of objective function iterations, enabling better real-time recognition of driving styles and subsequent dynamic control.

[0048] For both the stable and standard driving styles, the control strategies are based on a reference model of understeering characteristics to solve for the ideal yaw rate target. For both the aggressive and sporty driving styles, the control strategies are based on a reference model of the steering characteristics of professional drivers to solve for the ideal yaw rate target, thereby improving vehicle handling performance while ensuring vehicle stability.

[0049] When it is judged that the current driver has a smooth or standard driving style, the present technical solution uses the vehicle motion control module to implement a torque vector control strategy for the hub motor four-wheel drive vehicle with stability as the main goal, so that the hub motor four-wheel drive vehicle is more in line with the driving style of smooth and standard drivers; or when it is judged that the current driver has an aggressive or sporty driving style, the present technical solution uses the vehicle motion control module to implement a torque appropriate control strategy for the hub motor four-wheel drive vehicle with maneuverability as the main goal and safety as the main goal, so that the hub motor four-wheel drive vehicle is more in line with the driving style of aggressive and sporty drivers, thereby effectively improving the adaptability of the hub motor four-wheel drive vehicle to different driver driving styles and improving the adaptability of the torque vector control of the hub motor four-wheel drive vehicle.

[0050] In the above technical solution, the specific method for the vehicle motion control module to select the target stability factor according to the determined driving style of the driver is:

[0051] If the driving style recognition module determines that the current driver's driving style is a stable driving style or a standard driving style, the stability factor is determined. for:

[0052] Where: m is the total mass of the hub motor four-wheel drive vehicle; a and b are the distances from the center of mass of the hub motor four-wheel drive vehicle to the front and rear axles respectively; 、 are the front and rear axle lateral stiffness of the hub motor four-wheel drive vehicle respectively; L is the wheelbase of the hub motor four-wheel drive vehicle;

[0053] If the driving style recognition module determines that the current driver's driving style is an aggressive driving style or a sporty driving style, the stability factor is determined. for:

[0054] Where C k0 and C k1 are the gains of the transfer function when the driver enters and exits the curve, which directly affect K Tar The amplitude of the curve; τ0 and τ1 are the time constants of the transfer function when entering and exiting the curve, which directly affect K Tar rate of change; When it is greater than 0, it means exiting the curve. When it is less than 0, it means entering a curve; The above method realizes the selection of different control targets based on different driving styles.

[0055] In the above technical solution, the vehicle motion control module is based on the stability factor And the steering wheel angle obtained in real time by the vehicle state perception module and vehicle longitudinal speed Calculate the ideal yaw rate target for a hub motor 4WD vehicle The specific method is:

[0056] Determining different driver control objectives based on different driver driving styles includes: when the driving style identification module determines that the current driver driving style is a smooth driving style or a standard driving style, determining the control objective to be a torque vectoring control strategy with stability as the primary objective; or when the driving style identification module determines that the current driver driving style is an aggressive driving style or a sporty driving style, determining the control objective to be a torque vectoring control strategy with maneuverability as the primary objective and stability as the secondary objective;

[0057] The torque vector control strategy based on the stability objective includes: solving the ideal yaw rate target based on the understeering characteristic ;

[0058]

[0059] in, and are the front and rear wheel cornering stiffness, is the moment of inertia of the vehicle around the Z axis, a and b are the distances from the center of mass to the front and rear axles, respectively. is the vehicle's natural frequency, is the vehicle's damping ratio, m is the total mass of the hub motor four-wheel drive vehicle, L is the vehicle's wheelbase, is the longitudinal speed, is the lead correction amount, is the vehicle's natural frequency, represents the transfer function, is the front wheel turning angle;

[0060] The torque vectoring strategy, which prioritizes maneuverability while also ensuring stability, includes: A stability factor based on the entry and exit characteristics of a professional driver. Use the above formula to solve the ideal yaw rate target ;

[0061] Stability factor based on the cornering and exiting characteristics of professional drivers Solving for the ideal yaw rate target When the driver with the aggressive and sporty driving style increases the oversteer degree when the hub motor four-wheel drive vehicle enters the corner;

[0062] Maintaining neutral steering characteristics when a driver with an aggressive or sporty driving style controls a hub motor four-wheel drive vehicle during a turn;

[0063] Increases understeer when a driver with an aggressive or sporty driving style maneuvers a hub motor 4WD vehicle out of a corner.

[0064] In the above technical solution, the specific method for the torque vector control module to calculate the additional yaw torque based on the ideal yaw rate target and the actual yaw rate is:

[0065] The vehicle state perception module obtains the lateral force of each wheel of the hub motor four-wheel drive vehicle, the vehicle's moment of inertia around the Z axis, the distance from the center of mass to the front and rear axles, the vehicle's mass, the actual yaw rate r, and the ideal yaw rate target r * and the actual yaw rate r and the ideal yaw rate r * The derivative calculation is based on the main characteristics u of the torque vector control system when it is in a stable state s =bF yr -aF yf The steady-state control quantity of the additional yaw moment ΔM is obtained z_Stb , ΔM z_Stb =KUstb u s , where K Ustb The first calibration quantity is used to amplify or reduce the steady-state control quantity and provides correction and compensation u according to the transient changes of the state variable f =I z r * ,in is the derivative of the ideal yaw rate, I Z is the moment of inertia of the vehicle around the Z axis, and the additional yaw moment feedforward control value ΔM is obtained z_Ff =K Uff u f , where K Uff The second calibration quantity is used to amplify or reduce the feedforward control quantity, u f It is the feedforward control quantity before adjustment and the feedback control quantity ΔM of the additional yaw torque of the torque vector control system. z_Fb =K Ufb u e , K Ufb The third calibration quantity is used to amplify or reduce the feedback control quantity, u e is the feedback control quantity before adjustment, a and b are the distances from the center of mass to the front and rear axles respectively, and F yr and F yf are the lateral forces on the rear and front wheels of the vehicle respectively;

[0066] The steady-state control quantity , feedforward control quantity and feedback control quantity The three are added together to get the additional yaw moment .

[0067] The above design determines the desired additional yaw torque based on the calculated ideal yaw rate and the actual yaw rate to achieve tracking of the ideal yaw rate.

[0068] In the above technical solution, the vehicle state perception module monitors the fault state of the hub motor four-wheel drive vehicle and the results include:

[0069] Both the vehicle integrated braking control system IBC and the wheel hub motor control unit MCU are faulty, the vehicle integrated braking control system IBC is faulty but the wheel hub motor control unit MCU is normal, the wheel hub motor control unit MCU of one wheel is faulty, the wheel hub motor control unit MCU of two wheels on the opposite sides is faulty, the wheel hub motor control unit MCU of two wheels on the same side is faulty, and the wheel hub motor control unit MCU of more than two wheels is faulty.

[0070] In the above technical solution, the specific method of executing the corresponding fault handling strategy according to the result of fault status monitoring is:

[0071] When the vehicle integrated brake control system IBC and the wheel hub motor control unit MCU are both in good condition, the torque vector control system TVC operates normally, and the vehicle integrated brake control system IBC participates in the additional yaw moment when necessary. This configuration allows TVC and IBC to achieve integrated collaboration, directly requesting driving torque from the wheel hub motor and simultaneously requesting single-wheel braking torque from the IBC. This fully combines the advantages of the wheel hub motor's fast response and high transmission efficiency with the IBC's large hydraulic braking torque.

[0072] When the vehicle integrated brake control system IBC fails but the wheel hub motor control unit MCU is normal, the torque vector control system TVC enters the degraded mode. At this time, the vehicle integrated brake control system IBC does not participate in the additional yaw moment. Distribution of additional yaw moment Only executed by the wheel hub motor control unit MCU. At this time, due to the IBC failure, the distribution of the additional yaw torque can only be performed by the MCU;

[0073] When the wheel hub motor control unit MCU of one wheel fails or the wheel hub motor control unit MCU of the two wheels on the opposite side fails, the torque vector control system TVC enters the degraded mode regardless of whether the vehicle integrated braking control system IBC fails. At this time, the vehicle integrated braking control system IBC does not participate in the distribution of the additional yaw moment, and the additional yaw moment Only the wheel hub motor control unit MCU is in normal state. At this time, due to the failure of the existing MCU, TVC enters the degraded mode. To ensure the normal distribution of the additional yaw moment, the distribution task is performed by the MCU alone, and the IBC does not intervene. This is because the IBC's slow response will affect the distribution of the additional yaw moment.

[0074] When the MCU of the wheel hub motor control unit of the two wheels on the same side fails or the MCU of the wheel hub motor control unit of more than two wheels fails, the torque vector control system TVC will enter the closed state regardless of whether the vehicle integrated braking control system IBC fails. At this time, differential torque control cannot be formed, so TVC exits.

[0075] In the above technical solution, the specific method for distributing torque to generate additional driving torque and additional braking torque for each wheel based on the additional yaw torque combined with the fault status monitoring result is as follows:

[0076] When the torque vector control system TVC is working normally, the wheel hub motor control unit MCU completes the additional yaw torque part that needs to be completed ,include:

[0077] Will Distribution according to front and rear axle loads:

[0078]

[0079] Where: The front axle needs to be completed by the hub motor control unit MCU , The hub motor control unit MCU needs to complete the rear axle , a and b are the distances from the center of mass of the car to the front and rear axles respectively, L is the wheelbase of the car, and are the driving torques of the left and right front wheels respectively, and are the driving torques of the left and right rear wheels respectively, r is the wheel radius, and Respectively, front and rear wheelbase;

[0080] The vehicle integrated braking control system IBC completes the additional yaw moment part that needs to be completed , according to the principle of wheel execution efficiency, single wheel braking, when When the vehicle is turning left:

[0081] Only when the left wheel of the vehicle, that is, the left front wheel or the left rear wheel, generates braking force can a positive ΔM be generated. zb When the braking torque is generated on the left rear wheel, the left rear wheel is restricted by the friction ellipse and the lateral force F of the left rear wheel is y3 will decrease, which is equivalent to generating a negative ΔF y3 , thus forming a counterclockwise rotating torque around the center of mass of the vehicle, which is positive with ΔM zb Same direction, increase ΔM zb In summary, the left rear wheel brake is used, ΔT b3 * =r×2×ΔM zb3 / d r ;

[0082] when When the vehicle is turning right: apply the left front wheel brake. ;

[0083] when When the load is negative and the vehicle turns left: apply the right front wheel brake, ;

[0084] when When the load is negative and the vehicle turns left: apply the right rear wheel brake. ;

[0085] in, 、 、 and They represent the additional yaw moments of the left front wheel, right front wheel, left rear wheel, and right rear wheel that the IBC needs to distribute.

[0086] In the above technical solution, when the torque vector control system TVC enters the degradation mode, the hub motor control unit MCU completes the required ΔM zm (Due to the slow response of the IBC, after entering the degraded mode, the normal MCU is responsible for distributing the additional yaw torque to ensure that the additional yaw torque can be distributed normally), including:

[0087] When the hub motor control units MCU of the four wheels are all normal, Distribution according to front and rear axle loads:

[0088] ;

[0089] When the MCUs of the hub motor control units of the three wheels are normal, perform the operation on the axis where the MCUs of the two hub motor control units are normal. distribute:

[0090] 、 ;

[0091] The MCUs of the two wheel hub motor control units are normal and the MCUs of the two wheel hub motor control units are located on the same axis. The allocation method is:

[0092] or ;

[0093] The hub motor control unit MCU of the two wheels is normal, and the two normal motors are located on different axes. The allocation method is:

[0094] or .

[0095] In the above technical solution, the hub motor control unit MCU needs to complete , the automotive integrated brake control system IBC needs to complete The general allocation principles followed include:

[0096] When the torque vector control system TVC works normally:

[0097] If the current four-wheel hub motor maximum driving torque capacity is 80% of the calculated Less than total demand When the braking torque is generated, the vehicle integrated braking control system IBC is requested to generate the braking torque, and the required braking torque response value is monitored in real time. The braking torque generated by the vehicle integrated braking control system IBC is calculated according to the required braking torque response value. , during the IBC pressure building process, and The difference is compensated by the remaining 20% ​​driving capacity of the hub motor control unit MCU;

[0098] Or if the current four-wheel hub motor is 80% of the maximum driving torque capacity, the calculated ΔM zm Greater than the total demand ΔM z When , it is only necessary to request the power domain controller PDCU to generate a driving torque to meet ΔM z Require.

[0099] When the torque vector control system TVC is working in a degraded state:

[0100] The vehicle integrated brake control system IBC does not participate distribution; and the hub motor can work normally distribute.

[0101] A method for controlling torque vectoring of a four-wheel drive vehicle using a hub motor comprises the following steps:

[0102] Step 1: Determine the driver's driving style during the driving of the hub motor four-wheel drive vehicle;

[0103] Step 2: Obtain the steering wheel angle and vehicle longitudinal speed in real time, and monitor the fault status of the hub motor four-wheel drive vehicle;

[0104] Step 3: Select a target stability factor based on the determined driver's driving style, and calculate the ideal yaw rate target for the in-wheel motor four-wheel drive vehicle based on the target stability factor, the real-time steering wheel angle, and the vehicle's longitudinal speed;

[0105] Step 4: Calculate the additional yaw torque based on the ideal yaw rate target and the actual yaw rate, and execute the corresponding fault handling strategy based on the fault status monitoring results. Then, based on the additional yaw torque and the fault status monitoring results, torque distribution is performed to generate the additional driving torque and additional braking torque for each wheel.

[0106] The in-wheel motor four-wheel drive vehicle torque vector control method of this technical solution first obtains the driver's driving style at the current moment, and obtains the steering wheel angle and vehicle longitudinal speed in real time, calculates the current ideal yaw rate target, and passes it to the torque vector control module to perform torque vector control on the in-wheel motor four-wheel drive vehicle.

[0107] Technical solution 3:

[0108] A computer-readable storage medium stores a computer program, and the computer program performs the steps of the method described in Technical Solution 2 when executed by a processor.

[0109] Technical solution 4:

[0110] A computer program product includes a computer program, which implements the steps of the method described in Technical Solution 2 when executed by a processor.

[0111] The contents not described in detail in this specification belong to the prior art known to professional and technical personnel in this field.

Claims

1. A torque vector control system for a four-wheel drive vehicle with a hub motor, comprising: The driving style recognition module is used to determine the driver's driving style during the driving of the hub motor four-wheel drive vehicle; The vehicle status perception module is used to obtain the steering wheel angle, vehicle longitudinal speed and vehicle lateral acceleration in real time, and to monitor the fault status of hub motor four-wheel drive vehicles; The vehicle motion control module is used to select a target stability factor based on the determined driver's driving style, and calculate the ideal yaw rate target of the hub motor four-wheel drive vehicle based on the target stability factor, the real-time steering wheel angle and the vehicle's longitudinal speed; The torque vector control module is used to calculate the additional yaw torque based on the ideal yaw rate target and the actual yaw rate, and to execute the corresponding fault handling strategy according to the results of the fault status monitoring. Then, the torque is distributed based on the additional yaw torque combined with the fault status monitoring results to generate the additional driving torque and additional braking torque for each wheel.

2. The in-wheel motor four-wheel drive vehicle torque vector control system according to claim 1, wherein: The driving style identification module selects driving feature quantities and uses a BP neural network to classify the driving feature quantities to obtain the current driver's driving style. The driving feature quantities include: maximum lateral acceleration, variance of the product of steering wheel angle and vehicle speed, and maximum product of steering wheel angle and vehicle speed.

3. The in-wheel motor four-wheel drive vehicle torque vector control system according to claim 2, wherein: The specific method of the driving style identification module using the BP neural network to classify the driving style based on the driving feature is as follows: Based on fuzzy C-means clustering, the driving characteristics are used to classify the driving styles, including a stable driving style, a standard driving style, an aggressive driving style, and a sporty driving style; Select a single hidden layer BP neural network to build a driving style recognition model; Determine the number of neurons in the input layer, output layer, and hidden layer of the driving style recognition model; The softmax function is selected as the activation function of the output layer of the driving style recognition model. The driving feature quantity is transmitted to the driving style recognition model for driving style recognition, and the driving style with the maximum probability is output as the final recognition result.

4. The in-wheel motor four-wheel drive vehicle torque vector control system according to claim 3, wherein: The specific method for the vehicle motion control module to select the target stability factor based on the determined driver's driving style is as follows: If the driving style recognition module determines that the current driver's driving style is a stable driving style or a standard driving style, the stability factor is determined. for: , where: m is the total mass of the hub motor four-wheel drive vehicle; a and b are the distances from the center of mass of the hub motor four-wheel drive vehicle to the front and rear axles respectively; 、 are the front and rear axle lateral stiffness of the hub motor four-wheel drive vehicle respectively; L is the wheelbase of the hub motor four-wheel drive vehicle; If the driving style recognition module determines that the current driver's driving style is an aggressive driving style or a sporty driving style, the stability factor is determined. for: , where and are the gains of the transfer function when the driver enters and exits the curve, respectively; and are the time constants of the transfer functions when entering and exiting a curve, respectively; When it is greater than 0, it means exiting the curve. When it is less than 0, it means entering a curve; represents the steering wheel angular velocity, Indicates the steering wheel angle.

5. The in-wheel motor four-wheel drive vehicle torque vector control system according to claim 4, wherein: The vehicle motion control module is based on the stability factor And the steering wheel angle obtained in real time by the vehicle state perception module and vehicle longitudinal speed Calculate the ideal yaw rate target for a hub motor 4WD vehicle The specific method is: Determining different driver control objectives based on different driver driving styles includes: when the driving style identification module determines that the current driver driving style is a smooth driving style or a standard driving style, determining the control objective to be a torque vectoring control strategy with stability as the primary objective; or when the driving style identification module determines that the current driver driving style is an aggressive driving style or a sporty driving style, determining the control objective to be a torque vectoring control strategy with maneuverability as the primary objective and stability as the secondary objective; The torque vector control strategy based on the stability objective includes: solving the ideal yaw rate target based on the understeering characteristic ； ， in, and are the front and rear wheel cornering stiffness, is the moment of inertia of the vehicle around the Z axis, a and b are the distances from the center of mass to the front and rear axles, respectively. is the vehicle's natural frequency, is the vehicle's damping ratio, m is the total mass of the hub motor four-wheel drive vehicle, L is the vehicle's wheelbase, is the longitudinal speed, is the lead correction amount, is the vehicle's natural frequency, represents the transfer function, is the front wheel turning angle; The torque vectoring strategy, which prioritizes maneuverability while also ensuring stability, includes: A stability factor based on the entry and exit characteristics of a professional driver. Use the above formula to solve the ideal yaw rate target ； Stability factor based on the cornering and exiting characteristics of professional drivers Solving for the ideal yaw rate target When the driver with the aggressive and sporty driving style increases the oversteer degree when the hub motor four-wheel drive vehicle enters the corner; Maintaining neutral steering characteristics when a driver with an aggressive or sporty driving style controls a hub motor four-wheel drive vehicle during a turn; Increases understeer when a driver with an aggressive or sporty driving style maneuvers a hub motor 4WD vehicle out of a corner.

6. The in-wheel motor four-wheel drive vehicle torque vector control system according to claim 5, wherein: The specific method by which the torque vector control module calculates the additional yaw torque based on the ideal yaw rate target and the actual yaw rate is: The vehicle state perception module obtains the lateral force of each wheel of the hub motor four-wheel drive vehicle, the vehicle's moment of inertia around the Z axis, the distance from the center of mass to the front and rear axles, the vehicle's mass, the actual yaw rate r, and the ideal yaw rate target r * and the actual yaw rate r and the ideal yaw rate r * The derivative calculation is based on the main characteristics u of the torque vector control system when it is in a stable state s =bF yr -aF yf The steady-state control quantity of the additional yaw moment obtained is ΔM z_Stb , ΔM z_Stb =K Ustb u s , where K Ustb The first calibration quantity is used to amplify or reduce the steady-state control quantity and provides correction and compensation u according to the transient changes of the state variable f =I z r * ,in is the derivative of the ideal yaw rate, I Z is the moment of inertia of the vehicle around the Z axis, and the additional yaw moment feedforward control value ΔM is obtained z_Ff =K Uff u f , where K Uff The second calibration quantity is used to amplify or reduce the feedforward control quantity, u f It is the feedforward control quantity before adjustment and the feedback control quantity ΔM of the additional yaw torque of the torque vector control system. z_Fb =K Ufb u e , K Ufb The third calibration quantity is used to amplify or reduce the feedback control quantity, u e is the feedback control quantity before adjustment, a and b are the distances from the center of mass to the front and rear axles respectively, and F yr and F yf are the lateral forces on the rear and front wheels of the vehicle respectively; The steady-state control variable ΔM z_Stb , feedforward control quantity ΔM z_Ff And the feedback control amount ΔM z_Fb The sum of the three gives the additional yaw moment ΔM z When the wheel hub motor control unit MCU of one wheel fails or the wheel hub motor control unit MCU of two wheels on opposite sides fails, the torque vector control system TVC enters the degraded mode regardless of whether the vehicle integrated braking control system IBC fails. At this time, the vehicle integrated braking control system IBC does not participate in the additional yaw moment ΔM z The distribution of the additional yaw moment ΔM z Only executed by the wheel hub motor control unit MCU in normal state; 7. The in-wheel motor four-wheel drive vehicle torque vector control system according to claim 6, wherein: The vehicle status perception module monitors the fault status of the hub motor four-wheel drive vehicle and the results include: Both the vehicle integrated braking control system IBC and the wheel hub motor control unit MCU are faulty, the vehicle integrated braking control system IBC is faulty but the wheel hub motor control unit MCU is normal, the wheel hub motor control unit MCU of one wheel is faulty, the wheel hub motor control unit MCU of two wheels on the opposite sides is faulty, the wheel hub motor control unit MCU of two wheels on the same side is faulty, and the wheel hub motor control unit MCU of more than two wheels is faulty.

8. The in-wheel motor four-wheel drive vehicle torque vector control system according to claim 7, wherein: The specific method of executing the corresponding fault handling strategy based on the results of fault status monitoring is as follows: When the vehicle integrated brake control system IBC and the wheel hub motor control unit MCU are both in good condition, the torque vector control system TVC operates normally, and the vehicle integrated brake control system IBC participates in the additional yaw moment ΔM when necessary. z distribution; When the vehicle integrated brake control system IBC fails but the wheel hub motor control unit MCU is normal, the torque vector control system TVC enters the degraded mode. At this time, the vehicle integrated brake control system IBC does not participate in the additional yaw moment ΔM z The distribution of the additional yaw moment ΔM z Only executed by the hub motor control unit MCU; When the wheel hub motor control unit MCU of one wheel fails or the wheel hub motor control unit MCU of the two wheels on the opposite side fails, the torque vector control system TVC enters the degraded mode regardless of whether the vehicle integrated braking control system IBC fails. At this time, the vehicle integrated braking control system IBC does not participate in the additional yaw moment ΔM z The distribution of the additional yaw moment ΔM z Only executed by the wheel hub motor control unit MCU in normal state; When the wheel hub motor control unit MCU of two wheels on the same side fails or the wheel hub motor control unit MCU of more than two wheels fails, the torque vector control system TVC enters the closed state regardless of whether the vehicle integrated braking control system IBC fails.

9. The in-wheel motor four-wheel drive vehicle torque vector control system according to claim 8, wherein: The specific method for distributing the torque according to the additional yaw torque and the fault status monitoring results to generate the additional driving torque and additional braking torque of each wheel is as follows: When the torque vector control system TVC is working normally, the wheel hub motor control unit MCU completes the additional yaw torque part that needs to be completed ,include: Will Distribution according to front and rear axle loads: ， Where: The front axle needs to be completed by the hub motor control unit MCU ， The hub motor control unit MCU needs to complete the rear axle , a and b are the distances from the center of mass of the car to the front and rear axles respectively, L is the wheelbase of the car, and are the driving torques of the left and right front wheels respectively, and are the driving torques of the left and right rear wheels respectively, r is the wheel radius, and Respectively, front and rear wheelbase; The vehicle integrated braking control system IBC completes the additional yaw moment part that needs to be completed , single wheel braking based on wheel execution efficiency, when When the vehicle is turning left: apply left rear wheel brake, ； when When the vehicle is turning right: apply the left front wheel brake. ； when When the load is negative and the vehicle turns left: apply the right front wheel brake, ； when When the load is negative and the vehicle turns left: apply the right rear wheel brake, ； in, 、 、 and They represent the additional yaw moments of the left front wheel, right front wheel, left rear wheel, and right rear wheel that the IBC needs to distribute.

10. The in-wheel motor four-wheel drive vehicle torque vector control system according to claim 9, wherein: When the torque vector control system TVC enters the degradation mode, the hub motor control unit MCU completes the required ,include: When the hub motor control units MCU of the four wheels are all normal, Distribution according to front and rear axle loads: ； When the MCUs of the hub motor control units of the three wheels are normal, perform the operation on the axis where the MCUs of the two hub motor control units are normal. distribute: ； The MCUs of the two wheel hub motor control units are normal and the MCUs of the two wheel hub motor control units are located on the same axis. The allocation method is: or ； The MCUs of the hub motor control units of the two wheels are normal, and the two normal motors are located on different axes. The allocation method is: or 。 11. A method for torque vector control of a four-wheel drive vehicle with a hub motor, comprising the following steps: Step 1: Determine the driver's driving style during the driving of the hub motor four-wheel drive vehicle; Step 2: Obtain the steering wheel angle and vehicle longitudinal speed in real time, and monitor the fault status of the hub motor four-wheel drive vehicle; Step 3: Select a target stability factor based on the determined driver's driving style, and calculate the ideal yaw rate target for the in-wheel motor four-wheel drive vehicle based on the target stability factor, the real-time steering wheel angle, and the vehicle's longitudinal speed; Step 4: Calculate the additional yaw torque based on the ideal yaw rate target and the actual yaw rate, and execute the corresponding fault handling strategy based on the fault status monitoring results. Then, based on the additional yaw torque and the fault status monitoring results, torque distribution is performed to generate the additional driving torque and additional braking torque for each wheel.

12. A computer-readable storage medium storing a computer program, wherein the computer program implements the steps of the method according to claim 11 when executed by a processor.

13. A computer program product comprising a computer program, wherein when the computer program is executed by a processor, the computer program implements the steps of the method according to claim 11.

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