Electronic mechanical brake system drive slip control method

Abstract

The application discloses an electronic mechanical brake system driving anti-slip control method and belongs to the technical field of new energy vehicle linear control. Specifically, the method comprises the following steps: evaluating the current maximum allowable driving torque in real time according to vehicle and road surface state information; judging the wheel slip trend according to wheel acceleration, pre-clamping the EMB when the wheel has an obvious slip trend, and eliminating the brake gap by applying a pre-clamping torque; when the actual slip rate is greater than the optimal slip rate, identifying the driving intention of the driver according to the accelerator pedal opening degree change within t1 time, and distinguishing the power priority or stability priority mode of the driving anti-slip control. The application utilizes the pre-clamping and fast and accurate control of the electronic mechanical brake system to make the slip rate quickly converge, keeps the wheel slip rate near the optimal slip rate, and simultaneously, if the road adhesion condition changes or there is an estimation error, the dynamic coordinated control can also realize the accurate control of the slip rate, thereby guaranteeing the power in different working conditions and improving the stability.

Description

TECHNICAL FIELD

[0001] The present application relates to the field of new energy vehicle line control technology, more specifically to an electronic mechanical brake system driving anti-slip control method. BACKGROUND

[0002] The EMB (Electro-Mechanical Brake) electronic mechanical brake system adopts an electric control pure mechanical brake technology, uses an electric signal as a transmission medium to replace a traditional air pressure (hydraulic pressure) pipeline, uses a motor to drive an end brake execution mechanism to brake, and uses an electronic brake pedal to detect a brake intention of a driver, and is a truly line control brake system. Compared with a traditional brake system, the electronic mechanical brake system has the advantages of faster response, more accurate control, and higher efficiency.

[0003] For the driving anti-slip control method of a new energy vehicle, a wheel slip ratio is usually controlled by adjusting a driving torque of a driving motor, or applying a brake torque to a driving wheel, or a method combining the two.

[0004] A Chinese patent application with the publication number CN101774372A discloses a driving anti-slip control system of a hybrid vehicle and a control method thereof. The method includes: calculating a slip ratio through a wheel speed sensor to determine whether a tire is slipping; if the slip ratio is greater than a threshold value and a vehicle speed is greater than a threshold value, directly controlling a motor torque and a throttle opening degree through a PID (Proportion Integration Differentiation) control; if the slip ratio is greater than the threshold value and the vehicle speed is less than the threshold value, controlling an ASR (Anti-Slip Regulation) adjusting valve and an ABS (Anti-Lock Braking System) adjusting valve, first allowing a brake to intervene to reduce the slip ratio for a certain period of time, then allowing the brake to exit, and then controlling the motor torque and the throttle opening degree through the PID control. The method improves the driving stability and acceleration ability of the hybrid vehicle by combining the control of an engine, a motor, and a brake, but the method has the problems of poor adaptability and robustness by using the logical threshold and the PID control. On the other hand, the air brake has a slow response and cannot be finely controlled, is easy to overshoot, and cannot achieve the expected control effect. Moreover, the brake control is only intervened at the initial stage of the slip and then exited, is separated from the driving torque control, and cannot achieve the dynamic coordinated control effect of the driving force and the brake force. SUMMARY

[0005] To solve the above problems, the present application provides an electronic mechanical brake system driving anti-slip control method, which utilizes the characteristics of fast response and accurate control of the electronic mechanical brake system to realize the coordinated control of the brake torque and the driving torque, so that the wheel slip ratio is always maintained near the optimal slip ratio.

[0006] The present application adopts the following technical scheme:

[0007] An electronic mechanical brake system driving anti-slip control method, characterized in that it comprises the following steps:

[0008] S01, the chassis domain controller evaluates the current maximum allowable driving torque in real time according to vehicle and road surface state information ;

[0009] S02, if the wheel acceleration is greater than the body acceleration and continues to increase, the actual slip ratio is greater than 0 and continues to increase, it is determined that the wheel has a tendency to slip, and S03 is entered;

[0010] S03, the electronic mechanical brake performs pre-clamping, and by applying a pre-clamping torque the control motor quickly pushes the pad to the brake disc to eliminate the brake gap;

[0011] S04, compare the actual slip ratio with the target slip ratio, if the actual slip ratio is greater than the target slip ratio and the duration exceeds t1, enter S05;

[0012] S05, the drive slip function is activated, and the driving intention of the driver is recognized according to the change of the accelerator pedal opening, if the accelerator pedal opening is greater than the threshold value and continues to increase within t1, enter S06, otherwise enter S07;

[0013] S06, in the power priority mode, the driving torque is maintained as the demand torque of the driver , a feedforward + feedback control method is used to quickly and stably maintain the actual slip ratio to the target slip ratio, and then the driving torque is maintained and the brake torque output is adjusted to achieve precise control of the actual slip ratio until the brake torque is reduced to and maintained for t2 time to exit the drive slip control;

[0014] S07, in the stability priority mode, the driving torque is reduced to the maximum allowable driving torque , a sliding mode control algorithm is used to control the output of the brake torque to quickly and stably maintain the actual slip ratio to the target slip ratio, and then the brake torque is reduced to and maintained, and a sliding mode control algorithm is used to control the output of the driving torque to achieve precise control of the actual slip ratio until the driving torque output is greater than 90% of the driver's demand torque and maintained for t2 time to exit the drive slip control.

[0015] Specifically, the vehicle and road surface state information in S01 above includes the current wheel speed , the body acceleration , the real-time vehicle speed , and the current road surface adhesion coefficient , and the maximum allowable driving torque estimation formula is: (1), wherein: is the wheel load, R is the rolling radius of the wheel.

[0016] Further, the wheel acceleration in S02 above is compared with the vehicle body acceleration Before comparison, filtering is performed to prevent signal noise interference.

[0017] Preferably, the real-time vehicle speed in S01 above is estimated through vehicle dynamics equations or measured through a speed sensor.

[0018] In particular, the actual slip ratio in S03 above is calculated according to the following formula: (2).

[0019] According to the Burckhardt tire model, the optimal slip ratio under the current road adhesion coefficient is calculated , and this is used as the target slip ratio, and the specific formula is as follows: (3), (4); wherein, C 1 , C 2 , C 3 are fitting parameters, and the values of the fitting parameters are different for different roads.

[0020] In a preferred embodiment, the control method of feedforward + feedback in S06 above specifically includes: calculating the clamping force according to wheel end dynamics as the feedforward output of the electronic mechanical brake torque, The calculation formula is as follows: (5); the error between the actual slip ratio and the target slip ratio is calculated as the error input; a sliding mode control algorithm is used to control the feedback output of the electronic mechanical brake torque, so that the actual slip ratio quickly and stably reaches the target slip ratio, and the output brake torque value is recorded , wherein, The formula of the sliding mode control algorithm is as follows: (6); wherein: is the equivalent brake torque, is the switching control torque, is the thickness of the sliding layer, is the system state, including the error between the actual slip ratio and the optimal slip ratio .

[0021] The value of t1 is preferably 200 ms, and the threshold value of the accelerator pedal opening is preferably 80%, and the value of t2 is preferably 500 ms.

[0022] From the above description of the present application, compared with the prior art, the present application has the following advantages:

[0023] The method of coordinating and controlling the braking torque and the driving torque can distinguish different control modes according to the driving intention of the driver when the driving anti-skid is activated, and the pre-clamping and rapid and accurate control of the electronic mechanical brake system are used to make the slip rate quickly converge, and the wheel slip rate is kept near the optimal slip rate. Meanwhile, if the road adhesion condition changes or there is an estimation error of the road adhesion coefficient, the dynamic coordination control can also achieve accurate control of the slip rate. The method ensures the power under different road conditions and improves the stability. BRIEF DESCRIPTION OF DRAWINGS

[0024] Figure 1 The flowchart of the embodiment one of the present application.

[0025] Figure 2 The schematic diagram of the power priority control method of the embodiment one of the present application.

[0026] Figure 3 The schematic diagram of the stability priority control method of the embodiment one of the present application.

[0027] Figure 4 The system structure block diagram of the embodiment two of the present application. DETAILED DESCRIPTION

[0028] The specific embodiments of the present application will be described below with reference to the accompanying drawings. In order to fully understand the present application, many details are described below, but the present application can be implemented without these details for those skilled in the art. For well-known components, methods and processes, the following will not be described in detail.

[0029] Embodiment one

[0030] The embodiment provides an electronic mechanical brake system driving anti-skid control method, comprising the following steps:

[0031] S01, the chassis domain controller evaluates the current maximum allowable driving torque in real time according to the vehicle and road surface state information .

[0032] The vehicle and road surface state information includes: acquiring the current wheel speed of the vehicle , the body acceleration , the real-time vehicle speed and the current road adhesion coefficient . The maximum allowable driving torque estimation formula is:

[0033] (1)

[0034] In the formula: is the wheel load, R is the rolling radius of the wheel.

[0035] In another embodiment, the above real-time vehicle speed is estimated by vehicle dynamics equation, but also directly measured by sensors.

[0036] S02, the chassis domain controller calculates the actual slip ratio in real time The size of the slip ratio can clearly describe the degree of wheel slip. The specific calculation formula is:

[0037] (2)

[0038] According to the Burckhardt tire model, the optimal slip ratio under the current road adhesion coefficient is calculated The optimal slip ratio The optimal slip ratio is also the target slip ratio in the following steps, and the specific calculation formula is:

[0039] (3)

[0040] (4)

[0041] In the formula: C 1 , C 2 , C 3 are fitting parameters, and the fitting parameters of different roads are different.

[0042] According to the current wheel speed, the wheel acceleration is calculated in real time , It needs to be filtered to prevent signal noise interference. If is greater than and continues to increase, is greater than 0 and continues to increase, it is judged that the wheel has a tendency to slip, and S03 is entered;

[0043] S03, pre-clamping the electronic mechanical brake, by applying a pre-clamping torque Make the control motor quickly push the gasket to the brake disc, eliminate the brake gap. For example Figure 2 and Figure 3 A stage.

[0044] S04, compare the actual slip ratio with the target slip ratio, if the actual slip ratio is greater than the target slip ratio and the duration exceeds t1, the anti-skid function is activated, S05 is entered, and the accelerator pedal opening change within t1 time is recorded.

[0045] In the present embodiment, t1 is preferably 200 ms.

[0046] S05, the driving intention of the driver is identified according to the change of the accelerator pedal opening degree. If the accelerator pedal opening degree is greater than the threshold value and continuously increases within t1 time, the power priority mode S06 is entered, otherwise the stability priority mode S07 is entered.

[0047] In the present embodiment, the accelerator pedal opening degree threshold value is preferably 80%.

[0048] S06, the driving torque of the drive motor is maintained as the demand torque of the driver The clamping force is calculated according to the wheel end dynamics As the feedforward output of the electronic mechanical brake torque. The calculation formula is:

[0049] (5)

[0050] The actual slip rate is calculated The error between the optimal slip rate As the error input, the feedback output of the electronic mechanical brake torque is controlled using the sliding mode control algorithm to quickly stabilize the actual slip rate to the optimal slip rate, and the output brake torque value is recorded Where, The sliding mode control algorithm formula is as follows:

[0051] (6)

[0052] In the formula: The equivalent brake torque is The switching control torque is The sliding layer thickness is The system state contains the error between the actual slip rate And the optimal slip rate As in stage B. Figure 2

[0053] Then, the driving torque is maintained, and the output of the brake torque is controlled using the sliding mode control algorithm to control the actual slip rate to be always near the optimal slip rate, realizing precise control of the actual slip rate, as in stage C. Figure 2

[0054] As the road adhesion coefficient increases or the driver demand torque decreases, when the brake torque is reduced to And maintained for t2 time, it is considered that the drive slip control is completed, and the drive slip control is exited, as in stage D. Figure 2

[0055] In the present embodiment, t2 is preferably 500 ms.​​​

[0056] S07, the driving motor output driving torque is reduced to , the actual slip ratio and the optimal slip ratio error is calculated as an error input, and the electronic mechanical brake brake torque output is controlled using a sliding mode control algorithm to quickly stabilize the actual slip ratio to the optimal slip ratio. The sliding mode control algorithm formula is the same as S06, as Figure 3 Stage B.

[0057] After that, the brake torque is reduced to the pre-clamping torque and maintained, the actual slip ratio and the optimal slip ratio are calculated, and the error input is used to control the driving motor driving torque output using a sliding mode control algorithm to control the actual slip ratio around the optimal slip ratio, achieving precise control of the actual slip ratio, as Figure 3 Stage C.

[0058] When the driving motor driving torque is greater than 90% of the driver demand torque and is maintained for t2 time, it is considered that the driving slip control is completed, and the driving slip control is exited, as Figure 3 Stage D.

[0059] Example Two

[0060] The embodiment provides an electronic mechanical brake system driving slip control system. Referring to Figure 4 , the driving slip control system includes a chassis domain controller 100, an electronic mechanical brake 200, a driving motor 300, a wheel speed sensor 400, and an acceleration sensor 500. Among them, the electronic mechanical brake 200 and the wheel speed sensor 400 are four, one electronic mechanical brake 200 and one wheel speed sensor 400 are installed on the left front wheel of the vehicle, one electronic mechanical brake and one wheel speed sensor are installed on the left rear wheel, one electronic mechanical brake 200 and one wheel speed sensor 400 are installed on the right front wheel, and one electronic mechanical brake 200 and one wheel speed sensor 400 are installed on the right rear wheel. The wheel speed sensor 400 is used to collect the current wheel speed of the corresponding tire .

[0061] Referring to Figure 4 , the chassis domain controller 100 is in communication connection with the four wheel speed sensors 400 and the acceleration sensor 500, so as to evaluate the current maximum allowable driving torque in real time according to the current wheel speed and the vehicle body acceleration , and to calculate the actual slip ratio The chassis domain controller 100 is also connected with four electromechanical brakes 200 and a driving motor 300 respectively to send corresponding control instructions to the electromechanical brakes 200 and the driving motor 300.

[0062] The above is only a specific embodiment of the present application, but the design concept of the present application is not limited thereto, and any non-essential modification of the present application using the concept shall be deemed as an infringement of the protection scope of the present application.

Claims

1. A method for driving anti-slip control in an electromechanical braking system, characterized in that, Includes the following steps: S01, The chassis domain controller assesses the current maximum permissible driving torque in real time based on vehicle and road condition information. ; S02, if the wheel acceleration Greater than vehicle body acceleration And it continues to increase, with the actual slip ratio If the value is greater than 0 and continues to increase, it is determined that the wheel has a tendency to slip, and the process proceeds to S03; S03, the electromechanical brake is pre-clamped by applying a pre-clamping torque. The control motor quickly pushes the shim against the brake disc to eliminate the brake clearance. S04. Compare the actual slip ratio with the target slip ratio. If the actual slip ratio is greater than the target slip ratio and the duration exceeds t1, proceed to S05. S05, Drive anti-slip function activated. The driver's driving intention is identified based on the change in accelerator pedal opening. If the accelerator pedal opening is greater than the threshold and continues to increase within time t1, proceed to S06; otherwise, proceed to S07. S06. In power priority mode, maintain the driving torque at the driver's required torque. A feedforward + feedback control method is employed to quickly stabilize the actual slip ratio to the target slip ratio. Then, the driving torque is maintained while the braking torque output is adjusted to achieve precise control of the actual slip ratio until the braking torque decreases to a certain value. And maintain the t2 time to exit the drive anti-slip control; S07. In stability priority mode, reduce the driving torque to the maximum permissible driving torque. The sliding mode control algorithm is used to control the output of the braking torque so that the actual slip ratio quickly stabilizes to the target slip ratio, and then the braking torque is reduced to... It maintains this state and uses a sliding mode control algorithm to control the output of the driving torque to achieve precise control of the actual slip ratio until the output of the driving torque is greater than 90% of the torque required by the driver and is maintained for time t2, at which point it exits the drive anti-slip control.

2. The anti-slip control method for an electromechanical braking system as described in claim 1, characterized in that: The acceleration of the wheel in S02 With vehicle acceleration Before comparison, filtering is required to prevent signal noise interference.

3. The anti-slip control method for an electromechanical braking system as described in claim 1, characterized in that: The vehicle and road condition information in S01 includes the vehicle's current wheel speed. Vehicle acceleration Real-time vehicle speed and the current road surface adhesion coefficient Maximum permissible driving torque The estimation formula is: (1), where: For wheel load, R is the resistance force experienced by the vehicle, and R is the rolling radius of the wheel.

4. The anti-slip control method for an electromechanical braking system as described in claim 3, characterized in that: The real-time vehicle speed It can be estimated through vehicle dynamics equations or measured by speed sensors.

5. The anti-slip control method for an electromechanical braking system as described in claim 3, characterized in that: The actual slip ratio The calculation formula is: (2).

6. The anti-slip control method for an electromechanical braking system as described in claim 5, characterized in that: Based on the friction coefficient-slip ratio relationship of the Burckhardt tire model, the optimal slip ratio under the current road surface friction coefficient is determined. This is used as the target slip ratio, and the specific formula is as follows: (3), (4); where, C 1 , C 2 , C 3 The fitting parameters are different for different road surfaces.

7. The anti-slip control method for an electromechanical braking system as described in claim 6, characterized in that, The feedforward + feedback control method used in S06 specifically includes: calculating the clamping force based on wheel end dynamics. As a feedforward output of the braking torque of an electromechanical brake. The calculation formula is: (5) Calculate the error between the actual slip ratio and the target slip ratio as the error input; use the sliding mode control algorithm to control the feedback output of the electromechanical brake torque, so that the actual slip ratio can be quickly stabilized to the target slip ratio, and record the output braking torque value. ,in, The sliding mode control algorithm formula is as follows: (6); where: For equivalent braking torque, To switch control torque, For the thickness of the sliding layer, This refers to the system state, including the actual slip ratio. With optimal slip ratio The error.

8. The anti-slip control method for an electromechanical braking system as described in claim 1, characterized in that: The value of t1 is 200ms, the threshold value of accelerator pedal opening is 80%, and the value of t2 is 500ms.

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