Driving anti-skid control method and system based on maximum transmittable driving force estimation

Abstract

The present invention provides a driving anti-skid control method and system based on the estimation of the maximum transferable driving force. The present invention calculates the target rotation speed of each wheel and the target yaw velocity of the vehicle body according to the speed, front wheel steering angle and yaw velocity of the vehicle; obtains the estimated value of the maximum driving force that can be transmitted to the wheel according to the torque of each wheel driving motor and the wheel rotation speed; defines the wheel rotation speed disturbance value and the yaw velocity disturbance value according to the actual wheel rotation speed and the target rotation speed, the actual yaw velocity of the vehicle body and the target yaw velocity; preliminarily calculates the wheel driving motor torque command according to the above two disturbance values ​​and the estimated value of the maximum transferable driving force; and obtains the driving anti-skid control torque command value of each wheel by observing the positive and negative nature of the yaw velocity disturbance value.

Description

Technical Field

[0001] The present invention belongs to the technical field of drive and steering coordinated control, and in particular to a drive anti-skid control method based on maximum transmittable drive force estimation. Background Art

[0002] Drive anti-skid control belongs to the field of active safety control of automobiles, also known as traction control system. Drive anti-skid control prevents the driving wheels from slipping during vehicle acceleration, especially during low-adhesion acceleration and steering under complex motion conditions, so as to maintain the stability of the vehicle during driving.

[0003] There are two main types of existing drive anti-skid control methods. One is to use the fixed "optimal" slip rate of traditional fuel vehicles for drive anti-skid control; the other is to rely on road observers to identify the optimal slip rate in real time or rely on advanced drive anti-skid control systems such as nominal vehicle models. However, these methods are heavily dependent on the online recognition accuracy of road observers, lack effective verification and have poor adaptability under two-dimensional complex conditions on low-adhesion roads, and cannot obtain the optimal control effect. Summary of the invention

[0004] The object of the present invention is to provide a drive anti-skid control method and system based on the estimation of the maximum transferable driving force. On the basis of the estimation of the maximum transferable driving force, the drive anti-skid control of an independently driven vehicle is realized by tracking the target wheel speed and the target yaw angular velocity, thereby improving the stability of the vehicle.

[0005] The technical solution to achieve the purpose of the present invention is:

[0006] A driving anti-slip control method based on the estimation of the maximum transmittable driving force is controlled by the following torque command value:

[0007] When Δ2>0,

[0008]

[0009] When Δ2<0,

[0010]

[0011] When Δ2>0,

[0012]

[0013] When Δ2<0,

[0014]

[0015] Among them, w riis the target reference speed of the i-th wheel center, the left front wheel is 1, the right front wheel is 2, the left rear wheel is 3, the right rear wheel is 4, r is the yaw rate of the vehicle body, r r is the target yaw rate under steady-state neutral steering, Δ 1i is the speed disturbance value of the i-th wheel, Δ2 is the yaw rate disturbance value, is the estimated value of the maximum transferable driving force of the i-th wheel, J w is the wheel moment of inertia, R w is the wheel radius, b and a are the weight coefficients of wheel speed and yaw rate, C1 and C2 are controller parameters, T si is the motor torque command value of the i-th wheel.

[0016] A driving anti-skid control system based on maximum transmittable driving force estimation, comprising a speed sensor, a yaw rate sensor, an angle sensor integrated in an electronic control unit inside a vehicle, a wheel speed sensor installed on a wheel, and a torque sensor installed on a motor; the speed sensor, the yaw rate sensor, the angle sensor, the wheel speed sensor and the torque sensor are all connected to a processor; the processor outputs a control command to a vehicle actuator;

[0017] The speed sensor is used to obtain the speed u of the vehicle; the yaw rate sensor is used to obtain the yaw rate r of the vehicle; the angle sensor is used to obtain the front wheel steering angle δ f The wheel speed sensor is used to obtain the wheel speed w i ; The torque sensor is used to obtain the motor torque T i ;

[0018] The processor includes a target value calculation module, a maximum transmittable driving force estimation module, a disturbance value calculation module, a motor torque preliminary calculation module, and an anti-slip control torque calculation module;

[0019] The target value calculation module is used to calculate the target rotation speed and the target yaw angular velocity;

[0020] The maximum transmittable driving force estimation module is used to estimate the maximum driving force that the motor torque can transmit to the wheels;

[0021] The disturbance value calculation module is used to define the disturbance values ​​of the wheel speed and the yaw angular velocity;

[0022] The motor torque preliminary calculation module is used to calculate the motor torque command of the wheel;

[0023] The anti-skid control torque calculation module is used to calculate the driving anti-skid control torque command value of each wheel according to the positive and negative values ​​of the yaw rate disturbance value.

[0024] Compared with the prior art, the present invention has the following significant advantages:

[0025] (1) By obtaining the estimated value of the maximum transferable driving force of each wheel and applying it to the design of the wheel anti-slip control torque, it is not necessary to rely on other complex mathematical models or observers that reflect tire-road characteristics, thereby improving the controller's computing efficiency and system real-time performance;

[0026] (2) It does not require state information that is difficult to observe, such as vehicle weight and road adhesion coefficient. It fully considers the changing relationship between wheel speed and vehicle yaw angular velocity when the wheel slips, and uses it to adjust the output of the motor torque, thereby improving the robustness of the controller under changes in vehicle weight, load transfer, and adhesion coefficient. BRIEF DESCRIPTION OF THE DRAWINGS

[0027] Figure 1 The figure is a flow chart of a vehicle driving anti-skid control method according to some embodiments of the present invention.

[0028] Figure 2 FIG. 4 is a schematic diagram of a vehicle driving anti-skid control system according to some embodiments of the present invention.

[0029] Figure 3 Vehicle state diagram using certain embodiments of the present invention - before and after comparison of yaw rate control.

[0030] Figure 4 A vehicle state diagram for utilizing certain embodiments of the present invention - a before and after comparison of the center of mass sideslip angle control.

[0031] Figure 5 To utilize the vehicle status diagram of certain embodiments of the present invention - comparison between vehicle speed and wheel speed control before and after.

[0032] Figure 6 A wheel state diagram of certain embodiments of the present invention - a comparison before and after slip rate control.

[0033] Figure 7 FIG. 1 is a control command input diagram for utilizing certain embodiments of the present invention - steering wheel angle. DETAILED DESCRIPTION

[0034] The present invention is further described below in conjunction with the accompanying drawings and specific embodiments.

[0035] Combination Figure 1 A driving anti-skid control method based on maximum transmittable driving force estimation of the present invention comprises the following steps:

[0036] Step S1: Obtain the vehicle speed u, the vehicle body yaw rate r, and the front wheel steering angle δ f , individual wheel speeds and motor torque;

[0037] Step S2: according to the vehicle speed u, the front wheel turning angle δ f and the yaw rate r of the vehicle body, calculate the target reference speed of each wheel and the target yaw rate of the vehicle body:

[0038]

[0039]

[0040]

[0041]

[0042]

[0043] l f , l r are the distances from the vehicle’s center of mass to the front and rear axles, respectively, and K f , K r are the cornering stiffness of the front and rear tires, R w is the wheel radius, d f d r are the front and rear wheel tracks of the vehicle, r is the yaw rate of the vehicle body, δ f is the front wheel turning angle. l=l f +l r , l is the wheelbase, d f =d r , w ri is the target reference speed of the i-th wheel center, i = 1, 2, 3, 4 (in this embodiment, the vehicle is a four-wheel drive vehicle), r r is the target yaw rate under steady-state neutral steering, and m is the vehicle body mass. The target value is calculated so that the wheel speed and the vehicle body yaw rate can follow the target value well during the two-dimensional steering motion of the vehicle, so as to achieve wheel anti-slip and vehicle body stability.

[0044] Step S3: Calculate the estimated value of the maximum driving force that can be transmitted to the wheels according to the torque of each wheel motor and the wheel speed:

[0045]

[0046] in, is the estimated value of the maximum transferable driving force of the i-th wheel, w i is the speed of the i-th wheel, J w is the wheel moment of inertia, T i is the motor torque of the i-th wheel. i=1,2,3,4.

[0047] Step S4: define the wheel speed disturbance value and the yaw rate disturbance value according to the actual wheel speed and the target speed, the actual yaw rate and the target yaw rate of the vehicle body:

[0048] Δ 1i =w i -w ri

[0049] Δ2=rr r

[0050] Among them, Δ 1i is the speed disturbance value of the i-th wheel, and Δ2 is the yaw rate disturbance value. In order to better prevent wheel slip and vehicle body stability, the defined disturbance value should tend to 0, which can be achieved by using the SMC controller.

[0051] Step S5: Preliminarily calculate the wheel drive motor torque command based on the above two disturbance values ​​and the maximum transmittable driving force estimation value:

[0052]

[0053]

[0054] s i =bΔ 1i +aΔ2

[0055] Where b and a are the weight coefficients of wheel speed and yaw rate, respectively, Δ is the controller boundary layer and is a positive constant, Δ>0, k is an intermediate variable and C1, C2 are controller parameters and C1, C2>0, s i is the sliding surface of the i-th wheel, Δ 1i is the speed disturbance value of the i-th wheel, and Δ2 is the yaw rate disturbance value.

[0056] Step S6: Obtain the driving anti-skid control torque command value of each wheel by observing the positive and negative values ​​of the yaw rate disturbance value:

[0057] When Δ2>0,

[0058]

[0059] When Δ2<0,

[0060]

[0061] When Δ2>0,

[0062]

[0063] When Δ2<0,

[0064]

[0065] Among them, w ri is the target reference speed of the i-th wheel center, i=1, 2, 3, 4 (in this embodiment, the vehicle is a four-wheel drive vehicle, i is the tire order, from the driver's perspective, the left front wheel is 1, the right front wheel is 2, the left rear wheel is 3, and the right rear wheel is 4), r is the yaw angular velocity of the vehicle body, r r is the target yaw rate under steady-state neutral steering, Δ 1i is the speed disturbance value of the i-th wheel, Δ2 is the yaw rate disturbance value, is the estimated value of the maximum transferable driving force of the i-th wheel, J w is the wheel moment of inertia, R w is the wheel radius, b and a are the weight coefficients of wheel speed and yaw rate respectively, C1 and C2 are controller parameters, and C1 and C2>0, T si is the motor torque command value of the i-th wheel.

[0066] By analyzing the influence of the relationship between the yaw angular velocity and the target value on the controller and referring to the simulation results, the positivity and value of the weight coefficients a and b are determined respectively.

[0067] The vehicle speed, front wheel steering angle, yaw rate, each wheel speed and motor torque are obtained, and the target wheel speed and the target yaw rate of the vehicle body are calculated. The maximum estimated driving force that can be transmitted to the wheel is further calculated. According to the actual wheel speed and the target speed, the actual yaw rate and the target yaw rate of the vehicle body, the wheel speed disturbance value and the yaw rate disturbance value are defined. According to the above two disturbance values ​​and the maximum estimated driving force that can be transmitted, the wheel drive motor torque command is preliminarily calculated. By observing the positive and negative nature of the yaw rate disturbance value, the drive anti-skid control torque command value of each wheel is obtained, and then the motor torque output on each wheel is adjusted to prevent the wheel from slipping.

[0068] Based on the above method, the present invention also proposes a driving anti-skid control system based on the estimation of the maximum transmittable driving force, comprising a speed sensor, a yaw rate sensor, an angle sensor integrated in an electronic control unit inside the vehicle, a wheel speed sensor installed on a wheel, and a torque sensor installed on a motor; the speed sensor, the yaw rate sensor, the angle sensor, the wheel speed sensor and the torque sensor are all connected to a processor; the processor outputs a control command to a vehicle actuator;

[0069] The speed sensor is used to obtain the speed u of the vehicle;

[0070] The yaw rate sensor is used to obtain the yaw rate r of the vehicle;

[0071] The angle sensor is used to obtain the front wheel turning angle δ f ;

[0072] The wheel speed sensor is used to obtain the wheel speed w i ;

[0073] The torque sensor is used to obtain the motor torque T i ;

[0074] The processor includes a target value calculation module, a maximum transmittable driving force estimation module, a disturbance value calculation module, a motor torque preliminary calculation module, and an anti-slip control torque calculation module;

[0075] The target value calculation module is used to calculate the target speed and target yaw rate; the target speed and target yaw rate of each wheel are calculated according to the vehicle speed, front wheel angle and yaw rate:

[0076]

[0077]

[0078]

[0079]

[0080]

[0081] l f , l r are the distances from the vehicle’s center of mass to the front and rear axles, respectively, and K f , K r are the cornering stiffness of the front and rear tires, R w is the wheel radius, d f ,d r are the front and rear wheel tracks of the vehicle, r is the yaw rate of the vehicle body, δ f is the front wheel turning angle. l=l f +l r , l is the wheelbase, d f =d r , w ri is the target reference speed of the i-th wheel center, i=1, 2, 3, 4 (in this embodiment, the vehicle is a four-wheel drive vehicle), r r is the target yaw rate under steady-state neutral steering, and m is the vehicle body mass.

[0082] The maximum transferable driving force estimation module is used to estimate the maximum driving force that can be transferred to the wheels by the motor torque; according to the motor torque of each wheel and the wheel speed, the estimated value of the maximum driving force that can be transferred to the wheel is calculated:

[0083]

[0084] in, is the estimated value of the maximum transferable driving force of the i-th wheel, w i is the speed of the i-th wheel, J w is the wheel moment of inertia, T i is the motor torque of the i-th wheel. i=1, 2, 3, 4.

[0085] The disturbance value calculation module is used to define the disturbance values ​​of the wheel speed and the yaw rate; according to the actual wheel speed and the target speed, the actual yaw rate and the target yaw rate of the vehicle body, the wheel speed disturbance value and the yaw rate disturbance value are defined as:

[0086] Δ 1i =w i -w ri

[0087] Δ2=rr r

[0088] Among them, Δ 1i is the speed disturbance value of the i-th wheel, Δ2 is the yaw rate disturbance value. The SMC controller is used to make the disturbance values ​​of the wheel speed and yaw rate tend to 0.

[0089] The motor torque preliminary calculation module is used to preliminarily calculate the motor torque command of the wheel; according to the above two disturbance values ​​and the maximum transmittable driving force estimation value, the wheel drive motor torque command is preliminarily calculated:

[0090]

[0091]

[0092] s i =bΔ 1i +aΔ2

[0093] Where b and a are the weight coefficients of wheel speed and yaw rate, respectively, Δ is the controller boundary layer and is a positive constant, Δ>0, k is an intermediate variable and C1, C2 are controller parameters and C1, C2>0.

[0094] The anti-skid control torque calculation module is used to calculate the driving anti-skid control torque command value of each wheel according to the positive and negative values ​​of the yaw rate disturbance value; and obtain the driving anti-skid control torque command value of each wheel by observing the positive and negative values ​​of the yaw rate disturbance value:

[0095] When Δ2>0,

[0096]

[0097] When Δ2<0,

[0098]

[0099] When Δ2>0,

[0100]

[0101] When Δ2<0,

[0102]

[0103] By analyzing the influence of the relationship between the yaw angular velocity and the target value on the controller and referring to the simulation results, the positivity and value of the weight coefficients a and b are determined respectively.

[0104] The following is a simulation process of vehicle driving anti-skid control using the method of the present invention:

[0105] Simulation parameter settings: m = 1412 kg, J z =1536.7kg·m 2 ,d f =d r =1.675m,l f =1.015m,l r =1.895m; R w =0.325m, J ω =0.9kg·m 2 , g=9.81m / s 2 , a=1, b=0.2;

[0106] The simulation conditions are set as follows: the initial vehicle speed is 80km / h and the road adhesion coefficient is 0.4.

[0107] Combination Figure 3 The simulation comparison of the front and rear yaw angular velocity controlled by the drive anti-slip control algorithm is shown. Figure 4 The comparison of the sideslip angle at the center of mass is shown. After applying the drive anti-slip control algorithm, the yaw rate tracks the upper target value better and the overshoot is reduced; the peak value of the sideslip angle at the center of mass is reduced, which can keep the vehicle stable.

[0108] Combination Figure 5 The simulation comparison of vehicle speed and wheel speed before and after the drive anti-slip control algorithm is shown. Figure 6 The comparison of slip ratio simulation is shown. Figure 7The change of steering wheel angle during two-dimensional steering motion is shown. After applying the drive anti-slip control algorithm, the difference between vehicle speed and wheel speed is significantly reduced compared with before control, and the fluctuation of wheel speed is smaller than before control, and the slip rate is reduced from the original 0.3 to below 0.1, ensuring stable wheel adhesion.

Claims

1. A driving anti-slip control method based on maximum transmittable driving force estimation, characterized in that: Control is performed by the following torque command values: When Δ2>0, When Δ2<0, When Δ2>0, When Δ2<0, Among them, w ri is the target reference speed of the i-th wheel center, the left front wheel is 1, the right front wheel is 2, the left rear wheel is 3, the right rear wheel is 4, r is the yaw rate of the vehicle body, r r is the target yaw rate under steady-state neutral steering, Δ 1i is the speed disturbance value of the i-th wheel, Δ2 is the yaw rate disturbance value, is the estimated value of the maximum transferable driving force of the i-th wheel, J w is the wheel moment of inertia, R w is the wheel radius, b and a are the weight coefficients of wheel speed and yaw rate respectively, C1 and C2 are controller parameters, T si is the motor torque command value of the i-th wheel.

2. The driving anti-slip control method based on maximum transmittable driving force estimation according to claim 1, characterized in that: The steps to obtain the torque command value are as follows: Step S1, obtaining the vehicle speed, front wheel angle, yaw rate, each wheel speed and motor torque; Step S2, calculating the target rotation speed and target yaw rate of each wheel according to the speed, front wheel steering angle and yaw rate of the vehicle; Step S3, calculating an estimated value of the maximum driving force that can be transmitted to the wheels according to the torque of each wheel motor and the wheel speed; Step S4, defining a wheel speed disturbance value and a yaw rate disturbance value according to the actual wheel speed and the target wheel speed, the actual yaw rate and the target yaw rate of the vehicle body; Step S5, preliminarily calculating the wheel drive motor torque command according to the two disturbance values ​​and the maximum transmittable driving force estimation value; Step S6: Obtain the driving anti-skid control torque command value of each wheel by observing the positive and negative properties of the yaw rate disturbance value.

3. The driving anti-slip control method based on the estimation of the maximum transmittable driving force according to claim 2, characterized in that: Step 2: Target speed w of each wheel ri and the target yaw rate r under steady-state neutral steering r for: l f , l r are the distances from the vehicle center of mass to the front and rear axles, respectively, and K f , K r are the cornering stiffness of the front and rear tires, R w is the wheel radius, d f ,d r are the front and rear wheel tracks of the vehicle, δ f is the front wheel turning angle, l is the wheelbase, m is the vehicle mass, and u is the vehicle speed.

4. The driving anti-slip control method based on the estimation of the maximum transmittable driving force according to claim 2, characterized in that: Step 3 The estimated maximum driving force that can be transmitted to the wheels is: Among them, w i is the speed of the i-th wheel, T i is the motor torque of the i-th wheel.

5. The driving anti-slip control method based on maximum transmittable driving force estimation according to claim 2, characterized in that: Step 4: The wheel speed disturbance value and yaw rate disturbance value are: Δ 1i =w i -w ri Δ2=rr r , w i is the speed of the i-th wheel.

6. The driving anti-slip control method based on maximum transmittable driving force estimation according to claim 2, characterized in that: Step 5: The wheel drive motor torque command is: s i =bΔ 1i +aΔ2 Where Δ is the controller boundary layer and is a positive constant, s i is the sliding surface of the i-th wheel, k is an intermediate variable and 7. A driving anti-skid control system based on maximum transmittable driving force estimation, characterized in that: It includes a speed sensor, a yaw rate sensor, an angle sensor integrated in the electronic control unit inside the car, a wheel speed sensor installed on the wheel, and a torque sensor installed on the motor; the speed sensor, yaw rate sensor, angle sensor, wheel speed sensor and torque sensor are all connected to the processor; the processor outputs a control command to the vehicle actuator; The speed sensor is used to obtain the speed u of the vehicle; the yaw rate sensor is used to obtain the yaw rate r of the vehicle; the angle sensor is used to obtain the front wheel steering angle δ f The wheel speed sensor is used to obtain the wheel speed w i ; The torque sensor is used to obtain the motor torque T i ; The processor includes a target value calculation module, a maximum transmittable driving force estimation module, a disturbance value calculation module, a motor torque preliminary calculation module, and an anti-slip control torque calculation module; The target value calculation module is used to calculate the target rotation speed and the target yaw angular velocity; The maximum transmittable driving force estimation module is used to estimate the maximum driving force that the motor torque can transmit to the wheels; The disturbance value calculation module is used to define the disturbance values ​​of the wheel speed and the yaw rate; The motor torque preliminary calculation module is used to preliminarily calculate the motor torque command of the wheel; The anti-skid control torque calculation module is used to calculate the driving anti-skid control torque command value of each wheel according to the positive and negative value of the yaw rate disturbance value; The anti-skid control torque calculation module calculates the driving anti-skid control torque command value of each wheel as follows: When Δ2>0, When Δ2<0, When Δ2>0, When Δ2<0, Among them, w ri is the target reference speed of the i-th wheel center, the left front wheel is 1, the right front wheel is 2, the left rear wheel is 3, the right rear wheel is 4, r is the yaw rate of the vehicle body, r r is the target yaw rate under steady-state neutral steering, Δ 1i is the speed disturbance value of the i-th wheel, Δ2 is the yaw rate disturbance value, is the estimated value of the maximum transferable driving force of the i-th wheel, J w is the wheel moment of inertia, R w is the wheel radius, b and a are the weight coefficients of wheel speed and yaw rate respectively, C1, C2 are controller parameters and, T si is the motor torque command value of the i-th wheel.

8. The driving anti-skid control system based on the estimation of the maximum transmittable driving force according to claim 7, characterized in that: The target value calculation module calculation process is as follows: l f , l r are the distances from the vehicle center of mass to the front and rear axles, respectively, and K f , K r are the cornering stiffness of the front and rear tires, R w is the wheel radius, d f ,d r are the front and rear wheel tracks of the vehicle, δ f is the front wheel turning angle, l is the wheelbase, m is the vehicle mass, and u is the vehicle speed.

9. The driving anti-skid control system based on the estimation of the maximum transmittable driving force according to claim 7, characterized in that: The maximum transmittable driving force estimation module process is as follows: Among them, w i is the speed of the i-th wheel, T i is the motor torque of the i-th wheel.

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