Automobile drift control method based on brake-by-wire system

Abstract

The invention discloses an automobile drifting control method based on a brake-by-wire system. The automobile drifting control method comprises the following steps: S1, enabling an automobile to be in a drifting mode starting state; s2, judging whether a drift mode is triggered or not; s3, the braking torque for braking the rear axle of the automobile is calculated, and the rear axle of the automobile is braked to enable the automobile to drift; the brake torque is obtained by adding the feedforward brake torque, the yaw velocity feedback brake torque and the wheel speed feedback brake torque; the feedforward braking torque is calculated according to the load of the wheel, the road adhesion coefficient and the rolling radius of the wheel; the yaw velocity feedback braking torque is calculated according to a drift yaw velocity target, the wheel speed feedback braking torque is calculated according to a rear wheel speed target, and the drift yaw velocity target and the rear wheel speed target are both obtained according to a steering wheel angle and the change rate of the steering wheel angle; and S4, judging whether the automobile exits the drifting state or not in the drifting driving process of the automobile. By means of the control method, the drifting state of the automobile is more stable, control is easier, and safety is high.

Description

Technical Field

[0001] The present invention relates to the technical field of automobiles, and particularly relates to an automobile drift control method based on a wire control braking system. Background Art

[0002] Drift is a driving technique that makes the rear of the vehicle skid by torque control and power distribution in a curve. Without the assistance of any electronic control system, ordinary drivers often have difficulty mastering the driving technique of vehicle drift. With the continuous development of vehicle chassis control technology, the vehicle drift function makes it possible for ordinary drivers to experience drift.

[0003] The common vehicle drift function generates a drift state by taking advantage of the instantaneous response characteristic of the electric vehicle motor and making the rear wheels of the vehicle skid through the drive motor. This type of method makes the vehicle in an accelerating state during drift, resulting in greater control difficulty and poorer safety for the driver. Summary of the Invention

[0004] The purpose of the present invention is to provide an automobile drift control method based on a wire control braking system, which has a more stable drift state, is easy to control, and has high safety, aiming at the deficiencies in the prior art.

[0005] To achieve the above purpose, the technical solution adopted by the present invention is:

[0006] An automobile drift control method based on a wire control braking system, comprising:

[0007] S1, making the vehicle in a state where the drift mode is turned on;

[0008] S2, judging whether the drift mode is triggered according to the vehicle state information;

[0009] S3, when the drift mode is triggered and the vehicle enters the drift state, calculating the braking torque for braking the rear axle of the vehicle, and braking the rear axle of the vehicle through the braking system, and making the vehicle drift and travel in a state where the rear axle wheels of the vehicle are not locked;

[0010] The braking torque is obtained by adding the feedforward braking torque, the yaw rate feedback braking torque, and the wheel speed feedback braking torque;

[0011] The feedforward braking torque is calculated according to the load of the wheel, the road surface adhesion coefficient, and the wheel rolling radius;

[0012] The yaw rate feedback braking torque is calculated according to the target drift yaw rate, and the target drift yaw rate is calculated according to the steering wheel angle and the change rate of the steering wheel angle;

[0013] The wheel speed feedback braking torque is calculated based on the rear wheel speed target, and the rear wheel speed target is obtained according to the steering wheel angle and the change rate of the steering wheel angle;

[0014] S4. During the drifting driving of the vehicle, it is judged whether the vehicle exits the drifting state.

[0015] In some embodiments, the calculation method of the feedforward braking torque is as follows:

[0016] T base =c base *mue*g*m wheel *r wheel ;

[0017] Wherein,

[0018] c base is an adjustment coefficient obtained through calibration;

[0019] mue is the road surface adhesion coefficient;

[0020] g is the acceleration due to gravity;

[0021] m wheel is the gravity load borne by this wheel;

[0022] r wheel is the rolling radius of this wheel;

[0023] T base is the feedforward braking torque.

[0024] In some embodiments, the calculation formula of the target yaw rate during drifting is:

[0025] ω target =c yawtar *(θ sas +c sas_1 *ω sas );

[0026] Wherein,

[0027] θ sas is the steering wheel angle;

[0028] ω sas is the change rate of the steering wheel angle;

[0029] c sas_1 is the weight adjustment coefficient of the steering wheel angle and the change rate of the steering wheel angle, obtained through calibration;

[0030] c yawtar is the target yaw rate adjustment coefficient, obtained through calibration;

[0031] ω targetis the target of the drift yaw rate.

[0032] In some embodiments, the deviation between the target of the drift yaw rate and the actual yaw rate is used as feedback control, and the yaw rate feedback braking torque is obtained through the feedback control.

[0033] In some embodiments, the deviation between the target of the rear wheel speed and the actual rear wheel speed is used as feedback control, and the wheel speed feedback braking torque is obtained through the feedback control.

[0034] In some embodiments, the wheel speed feedback braking torques of the left and right rear wheels are respectively calculated according to the actual rear wheel speeds of the left and right rear wheels, so as to calculate the braking torques of the two rear wheels and respectively brake the two rear wheels correspondingly.

[0035] In some embodiments, in step S1, the conditions for triggering the drift mode include:

[0036] The vehicle speed is within a set range;

[0037] The road surface gradient is less than a set angle;

[0038] The driver does not step on the brake and the throttle opening is less than a set value;

[0039] When the driver turns the steering wheel, the steering wheel angle is greater than a set value, and the rate of change of the steering wheel angle is greater than a set value;

[0040] When all the conditions are met, the drift mode is triggered to make the vehicle enter the drift state.

[0041] In some embodiments, in step S4, during the vehicle drift driving process, the actual drifted angle value of the vehicle is calculated in real time. When the actual drifted angle value of the vehicle reaches the expected vehicle drift angle value of the driver, the drift state is exited.

[0042] In some embodiments, the calculation method of the actual drifted angle value of the vehicle is:

[0043] θ yaw = θ yawk1 + ω yawcor * dt;

[0044]

[0045] Wherein,

[0046] ω yaw is the yaw rate value sampled by the sensor at the current moment;

[0047] ω yawcork1 is the yaw rate correction value calculated at the previous moment;

[0048] ω yawcor is the correction value of the yaw rate at the current moment;

[0049] n is an adjustment coefficient, and its value is set to any integer greater than or equal to 0;

[0050] θ yawk1 is the drift angle calculated at the previous moment;

[0051] dt is the program running period;

[0052] θ yaw is the drift angle value at the current moment.

[0053] In some embodiments, the calculation method of the desired drift angle value of the vehicle by the driver is:

[0054] θ target = c drift *(θ sas + c sas_2 * ω sas );

[0055] Wherein,

[0056] θ sas is the steering wheel angle;

[0057] ω sas is the steering wheel angle change rate;

[0058] c sas_2 is the weight adjustment coefficient of the steering wheel angle and the steering wheel angle change rate, obtained by calibration;

[0059] c drift is the vehicle drift angle adjustment coefficient desired by the driver, obtained by calibration;

[0060] θ target is the vehicle drift angle value desired by the driver.

[0061] In some embodiments, in step S4, when the driver returns the steering wheel to the straight position during the vehicle drift driving process, the drift state is exited.

[0062] Due to the application of the above technical solution, the vehicle drift control method based on the wire control braking system of the present invention has the following advantages compared with the prior art:

[0063] (1) Realize vehicle drift control based on the wire control braking system, without any requirements on the type and parameters of the vehicle drive unit. The method of this patent is suitable for any vehicle equipped with a wire control braking system, including front-wheel drive, rear-wheel drive and four-wheel drive vehicles;

[0064] (2) Realize vehicle drift control based on the electronic brake system. During the drift state, the vehicle speed can be controlled very low, which is safe and easier to control.

[0065] (3) During the drift process, based on the closed-loop control of the yaw rate, the drift state is more stable and easier to control.

[0066] (4) During the drift process, based on the closed-loop control of the rear wheel speed, the rear wheels will not lock or have an excessive slip ratio, and the wear of the wheels is smaller.

[0067] (5) Under the method of this patent, the driver can turn the steering wheel to different angles to determine different drift angle targets. After this drift control method controls the vehicle to drift to the target angle, it will automatically stop drifting, which is safe and easier to control. Description of the Drawings

[0068] Appendix Figure 1 is a flowchart of the vehicle drift control method based on the electronic brake system of this embodiment. Detailed Embodiment

[0069] Next, the technical solution of the present invention will be clearly and completely described in conjunction with the drawings. Obviously, the described embodiments are part of the embodiments of the present invention, rather than all of them. All other embodiments obtained by those of ordinary skill in the art based on the embodiments of the present invention without creative work fall within the scope of protection of the present invention.

[0070] The flowchart of the vehicle drift control method based on the electronic brake system of the present invention is as Figure 1 shown, and specifically includes the following steps:

[0071] S1. Make the vehicle in a state where the drift mode is turned on.

[0072] It can be activated by physical buttons or the driving mode linkage of the vehicle itself to make the vehicle in a state where the drift mode is turned on. The physical buttons can be set on the vehicle display screen or at positions suitable for the driver to operate, such as the steering wheel. The present embodiment does not specifically limit the position of the physical buttons.

[0073] S2. According to the vehicle state information, determine whether to trigger the drift mode.

[0074] To further improve the safety during vehicle drifting, after the vehicle is in a state where the drift mode is turned on, it is necessary to identify the current vehicle state information. Only when the vehicle state information meets the set conditions is it allowed to trigger the drift mode, so as to prevent difficult control and instability during drifting and improve the safety of vehicle drifting.

[0075] The conditions for triggering the drift mode include:

[0076] (1) When the vehicle speed of the automobile is within the set range, in this embodiment, the set range of the vehicle speed of the automobile is 5 - 23 m / s;

[0077] (2) The road surface gradient is less than the set angle. In this embodiment, the road surface gradient is set to be less than 4°;

[0078] (3) The driver does not step on the brake, and the throttle opening is less than the set value. In this embodiment, the set value is 10%;

[0079] (4) When the driver quickly turns the steering wheel, the steering wheel angle is greater than the set value, and the rate of change of the steering wheel angle is greater than the set value.

[0080] When all of the above multiple conditions are satisfied, the drift mode can be triggered to make the vehicle enter the drift state.

[0081] S3, brake the rear axle of the vehicle to make the vehicle drift.

[0082] After the drift mode is triggered and the vehicle enters the drift state, a certain braking torque is established on the rear axle of the vehicle through a pure mechanical wire control braking system, so that the rear axle wheels of the vehicle are in a state of relatively low wheel speed, that is, the non-locked state. At this time, the lateral force generated by the rear axle wheels is very low, and the rear axle wheels of the vehicle will skid, thereby making the vehicle drift. The pure mechanical wire control braking system can be EMB or EHB.

[0083] The braking torque applied to the rear axle of the vehicle is obtained by adding the feedforward braking torque, the yaw rate feedback braking torque, and the wheel speed feedback braking torque.

[0084] (1) Calculate the feedforward braking torque.

[0085] The feedforward braking torque is calculated according to the load of the wheel, the road surface adhesion coefficient, and the wheel rolling radius. The specific calculation formula is as follows:

[0086] T base =c base *mue*g*m wheel *r wheel (1)

[0087] Among them,

[0088] c base is an adjustment coefficient, which can be obtained through calibration;

[0089] mue is the road surface adhesion coefficient;

[0090] g is the acceleration due to gravity;

[0091] m wheel is the gravity load borne by the wheel;

[0092] r wheel is the rolling radius of the wheel;

[0093] T base is the feedforward braking torque.

[0094] (2) Calculate the yaw rate feedback braking torque.

[0095] The yaw rate feedback braking torque is calculated based on the target drift yaw rate, and the target drift yaw rate is calculated based on the steering wheel angle and the change rate of the steering wheel angle, etc.

[0096] The calculation formula for the target drift yaw rate is as follows:

[0097] ω target = c yawtar *(θ sas + c sas_1 *ω sas ) (2)

[0098] where,

[0099] θ sas is the steering wheel angle;

[0100] ω sas is the change rate of the steering wheel angle;

[0101] c sas_1 is the weight adjustment coefficient of the steering wheel angle and the change rate of the steering wheel angle, which can be obtained through calibration. In this implementation, it can be calibrated to 0.5;

[0102] c yawtar is the target yaw rate adjustment coefficient, which can be obtained through calibration. In this implementation, it can be calibrated to 0.3;

[0103] ω target is the target drift yaw rate.

[0104] After calculating the target drift yaw rate, calculate the deviation between the target drift yaw rate and the actual yaw rate, and use this deviation as feedback control to obtain the yaw rate feedback braking torque through feedback control. In this embodiment, the feedback control can use fuzzy PID or other feedback control algorithms.

[0105] (3) Calculate the wheel speed feedback braking torque.

[0106] When the vehicle is in a drifting state, by identifying information such as the steering wheel angle and the change rate of the steering wheel angle, the target rear wheel speed is determined by looking up a table or other means. After obtaining the target rear wheel speed, the deviation between the target rear wheel speed and the actual rear wheel speed is calculated, and this deviation is used as feedback control to obtain the wheel speed feedback braking torque through feedback control. In this embodiment, the feedback control can adopt fuzzy PID or other feedback control algorithms.

[0107] During the driving process of the vehicle, there may be differences in the actual rear wheel speeds of the left and right rear wheels of the vehicle, resulting in different deviations as described above, and thus different wheel speed feedback braking torques for the left and right rear wheels. Therefore, in this embodiment, the wheel speed feedback braking torques for the left and right rear wheels are calculated separately.

[0108] When the wheel speed feedback braking torques of the left and right rear wheels are different, the calculated final braking torques for the left and right rear wheels are also different. Brake control is performed on the two rear wheels respectively according to the calculated braking torques, so that the vehicle drifts.

[0109] S4. During the drifting driving of the vehicle, it is judged whether the vehicle exits the drifting state.

[0110] There are several ways for the vehicle to exit the drifting state during the drifting driving process as follows:

[0111] Method 1: During the drifting driving process of the vehicle, the actually drifted angle value of the vehicle is calculated in real time. When the actually drifted angle value of the vehicle reaches the desired vehicle drifting angle value of the driver, the drifting state is exited. Through this method, the driver can turn the steering wheel to different angles to determine different drifting angle targets, so that the vehicle drifts at different angles, and the vehicle drifting angle control can be realized with high safety.

[0112] (1) Calculate the actually drifted angle value of the vehicle.

[0113] By identifying the actual yaw rate, the integration of the yaw rate starts when the vehicle enters the drifting state, and the discrete integration method is used to calculate the actually drifted angle value of the vehicle. The specific calculation method is as follows:

[0114] θ yaw =θ yawk1 +ω yawcor *dt (3)

[0115]

[0116] Among them,

[0117] ω yaw is the yaw rate value sampled by the sensor at the current moment;

[0118] ω yawcor1is the yaw rate correction value calculated at the previous moment;

[0119] ω yawcor is the yaw rate correction value at the current moment;

[0120] n is the adjustment coefficient, whose value can be set as any integer greater than or equal to 0, obtained through calibration, and can be calibrated as 10 in this implementation;

[0121] θ yawk1 is the drift angle calculated at the previous moment;

[0122] dt is the program running period;

[0123] θ yaw is the drift angle value at the current moment.

[0124] (2) Calculate the desired car drift angle value of the driver.

[0125] Calculate the desired car drift angle value of the driver according to information such as the steering wheel angle and the change rate of the steering wheel angle. The specific calculation method is as follows:

[0126] θ target =c drift *(θ sas +c sas_2 *ω sas ) (5)

[0127] Among them,

[0128] θ sas is the steering wheel angle;

[0129] ω sas is the change rate of the steering wheel angle;

[0130] c sas_2 is the weight adjustment coefficient of the steering wheel angle and the change rate of the steering wheel angle, which can be obtained through calibration

[0131] and can be calibrated as 0.1 in this implementation;

[0132] c drift is the adjustment coefficient of the desired car drift angle of the driver, which can be obtained through calibration. In this implementation

[0133] it can be calibrated as 0.6;

[0134] θ target is the desired car drift angle value of the driver.

[0135] Method 2: When the driver returns the steering wheel to the straight position during the car's drifting driving, exit the drifting state.

[0136] The above embodiments are only for illustrating the technical concept and features of the present invention, and the purpose is to enable those skilled in the art to understand the content of the present invention and implement it accordingly. It is not intended to limit the protection scope of the present invention. Any equivalent changes or modifications made according to the spirit of the present invention should be covered within the protection scope of the present invention.

Claims

1. A vehicle drift control method based on a wire control brake system, characterized in that: include: S1, puts the car in drift mode on; S2, judging whether to trigger the drift mode according to the vehicle status information; S3, when the drift mode is triggered to make the vehicle enter a drift state, the braking torque for braking the rear axle of the vehicle is calculated, and the rear axle of the vehicle is braked through the braking system, so that the vehicle drifts when the rear axle wheels of the vehicle are not locked; The braking torque is obtained by adding the feedforward braking torque, the yaw rate feedback braking torque and the wheel speed feedback braking torque; The feedforward braking torque is calculated based on the wheel load, road adhesion coefficient, and wheel rolling radius; The yaw rate feedback braking torque is calculated based on a drift yaw rate target, and the drift yaw rate target is calculated based on a steering wheel angle and a rate of change of the steering wheel angle; The wheel speed feedback braking torque is calculated based on a rear wheel speed target, and the rear wheel speed target is obtained based on a steering wheel angle and a rate of change of the steering wheel angle; S4, during the drifting process of the vehicle, determining whether the vehicle has exited the drifting state.

2. The vehicle drift control method based on the wire control brake system according to claim 1, characterized in that: The calculation method of the feedforward braking torque is: T base =c base *mue*g*m wheel *r wheel ; in, c base is the adjustment coefficient, obtained through calibration; mue is the road adhesion coefficient; g is the acceleration due to gravity; m wheel is the gravity load borne by the wheel; r wheel is the rolling radius of the wheel; T base is the feedforward braking torque.

3. The vehicle drift control method based on the wire control brake system according to claim 1, characterized in that: The calculation formula of the drift yaw rate target is: oh target =c yawtar *(θ sas +c sas_1 *oh sas ); in, θ sas is the steering wheel angle; ω sas is the steering wheel angle change rate; c sas_1 is the weight adjustment coefficient of the steering wheel angle and the steering wheel angle change rate, obtained through calibration; c yawtar is the target yaw rate adjustment coefficient, obtained through calibration; ω target is the drift yaw rate target.

4. The vehicle drift control method based on a wire control brake system according to claim 1 or 3, characterized in that: The deviation between the drift yaw rate target and the actual yaw rate is used as feedback control to obtain the yaw rate feedback braking torque through feedback control.

5. The vehicle drift control method based on the wire control brake system according to claim 1, characterized in that: The deviation between the rear wheel speed target and the actual rear wheel speed is used as feedback control to obtain the wheel speed feedback braking torque through feedback control.

6. The vehicle drift control method based on the wire control brake system according to claim 5, characterized in that: The wheel speed feedback braking torques of the left and right rear wheels are calculated respectively according to the actual rear wheel speeds of the left and right rear wheels, thereby calculating the braking torques of the two rear wheels to brake the two rear wheels respectively.

7. The vehicle drift control method based on the wire control brake system according to claim 1, characterized in that: In step S1, the conditions for triggering the drift mode include: The vehicle speed is within the set range; The road slope is less than the set angle; The driver does not step on the brakes, and the throttle opening is less than the set value; When the driver turns the steering wheel, the steering wheel angle is greater than a set value, and the rate at which the steering wheel angle changes is greater than a set value; When multiple conditions are met, the drift mode is triggered and the car enters a drift state.

8. The vehicle drift control method based on the wire control brake system according to claim 1, characterized in that: In step S4, the actual drift angle of the car is calculated in real time during the drifting process of the car. When the actual drift angle of the car reaches the car drift angle value expected by the driver, the drift state is exited.

9. The vehicle drift control method based on the wire control brake system according to claim 8, characterized in that: The calculation method for the actual angle value of the car's drift is: i yaw =θ yawk1 +oh yawcor *dt; in, ω yaw is the yaw angular velocity value sampled by the sensor at the current moment; ω yawcork1 is the yaw rate correction value calculated at the previous moment; ω yawcor is the yaw rate correction value at the current moment; n is the adjustment coefficient, and its value is set to any integer greater than or equal to 0; θ yawk1 The drift angle calculated at the last moment; dt is the program running cycle; θ yaw It is the drift angle value at the current moment.

10. The vehicle drift control method based on the wire control brake system according to claim 8, characterized in that: The calculation method for the car drift angle value expected by the driver is: i target =c drift *(θ sas +c sas_2 *oh sas ); in, θ sas is the steering wheel angle; ω sas is the steering wheel angle change rate; c sas_2 is the weight adjustment coefficient of the steering wheel angle and the steering wheel angle change rate, obtained through calibration; c drift The drift angle adjustment coefficient of the car expected by the driver is obtained through calibration; θ target It is the car drift angle value expected by the driver.

11. The vehicle drift control method based on a wire control brake system according to claim 1, characterized in that: In step S4, when the driver straightens the steering wheel during the drifting process of the car, the drifting state is exited.

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