Driving anti-skid control method for electronic mechanical braking system

Abstract

The invention discloses a driving anti-skid control method for an electronic mechanical braking system, and belongs to the technical field of drive-by-wire control of new energy vehicles. The method specifically comprises the steps that the current maximum allowable driving torque is evaluated in real time according to vehicle and road surface state information; judging the slip tendency of the wheel according to the acceleration of the wheel, pre-clamping the EMB when the wheel has an obvious slip tendency, and applying a pre-clamping moment to eliminate a brake clearance; and when it is judged that the actual slip rate is larger than the optimal slip rate, the driving intention of a driver is recognized according to the opening change of the accelerator pedal within the time t1, and power performance priority or stability priority mode distinguishing is conducted on driving anti-slip control. According to the method, the slip rate is rapidly converged through pre-clamping and rapid and accurate control of the electronic mechanical braking system, the wheel slip rate is kept close to the optimal slip rate, meanwhile, if the road adhesion condition changes or an estimation error exists, accurate control over the slip rate can be achieved through dynamic coordination control, and the control precision is improved. And the stability is improved while the dynamic property is ensured under road surfaces of different working conditions.

Description

TECHNICAL FIELD

[0001] The present application relates to the field of new energy vehicle drive-by-wire technology, and more particularly 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 an electric 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 drive-by-wire 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 a 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 combination of both.

[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 (Proportional-Integral-Derivative) 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 has the problems of poor adaptability and robustness due to the logical threshold and the PID control method. 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 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 fast response and accurate control characteristics of the electronic mechanical brake system to achieve coordinated control of brake torque and driving torque, so that the wheel slip ratio is always maintained near the optimal slip ratio.

[0006] The present application adopts the following technical solutions: An electronic mechanical brake system driving anti-slip control method, characterized in that it comprises 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.

[0007] Specifically, the vehicle and road condition information in S01 above 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.

[0008] Furthermore, the wheel acceleration in S02 mentioned above With vehicle acceleration Before comparison, filtering is required to prevent signal noise interference.

[0009] Preferably, the above-mentioned real-time vehicle speed It can be estimated through vehicle dynamics equations or measured by speed sensors.

[0010] Specifically, the aforementioned actual slip ratio The calculation formula is: (2).

[0011] 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.

[0012] In a preferred embodiment, the feedforward + feedback control method 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.

[0013] The preferred value for t1 is 200ms, the preferred value for the accelerator pedal opening threshold is 80%, and the preferred value for t2 is 500ms.

[0014] As can be seen from the above description of the present invention, compared with the prior art, the present invention has the following advantages: By using the above method of coordinated control of braking torque and driving torque, different control modes can be distinguished according to the driver's driving intention when the anti-skid system is activated. The pre-clamping and rapid and precise control of the electromechanical braking system can quickly converge the slip ratio, keeping the wheel slip ratio near the optimal slip ratio. At the same time, if the road surface adhesion changes or there is an estimation error in the road surface adhesion coefficient, the dynamic coordinated control can also achieve precise control of the slip ratio. This method ensures power performance while improving stability under different road conditions. Attached Figure Description

[0015] Figure 1 This is a flowchart illustrating Embodiment 1 of the present invention.

[0016] Figure 2 This is a schematic diagram of the power priority control method according to Embodiment 1 of the present invention.

[0017] Figure 3 This is a schematic diagram of the stability priority control method according to Embodiment 1 of the present invention.

[0018] Figure 4 This is a system structure block diagram of Embodiment 2 of the present invention. Detailed Implementation

[0019] Specific embodiments of the present invention will now be described with reference to the accompanying drawings. Many details are described below to provide a comprehensive understanding of the invention; however, those skilled in the art will not need these details to implement the invention. Well-known components, methods, and processes will not be described in detail below.

[0020] Example 1 This embodiment provides a method for anti-slip control of an electromechanical braking system, including 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. .

[0021] Vehicle and road condition information includes: obtaining the vehicle's current wheel speed. Vehicle acceleration Real-time vehicle speed and the current road surface adhesion coefficient The formula for estimating the maximum permissible driving torque is: (1) In the formula: For wheel load, R is the resistance force experienced by the vehicle, and R is the rolling radius of the wheel.

[0022] In another embodiment, the real-time vehicle speed can be estimated not only through vehicle dynamics equations but also directly measured by sensors.

[0023] S02, Chassis domain controller calculates actual slip ratio in real time. The slip ratio clearly describes the degree of wheel slippage. The specific calculation formula is: (2) Based on the Burckhardt tire model, the coefficient of adhesion and slip ratio The relationship is used to determine the optimal slip ratio under the current road surface adhesion coefficient. The optimal slip ratio It is also the target slip ratio in the following steps, and the specific calculation formula is as follows: (3) (4) In the formula: C 1 , C 2 , C 3 The fitting parameters are different for different road surfaces.

[0024] Calculate wheel acceleration in real time based on current wheel speed. , Filtering is required to prevent signal noise interference. If Greater than And it continues to increase. 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. Pre-clamp the electromechanical brake by applying a pre-clamping torque. The control motor quickly pushes the shims against the brake disc, eliminating the brake clearance. For example... Figure 2 and Figure 3 Phase A of the process.

[0025] 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-slip function is activated, and proceed to S05 to record the change in accelerator pedal opening within time t1.

[0026] In this embodiment, t1 is preferably 200ms.

[0027] S05. Identify the driver's driving intention 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, enter the power priority mode S06; otherwise, enter the stability priority mode S07.

[0028] In this embodiment, the accelerator pedal opening threshold is preferably 80%.

[0029] S06. Maintain the driving torque output by the drive motor at the torque required by the driver. ; Calculate 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 actual slip ratio With optimal slip ratio The error is used as the error input, and the feedback output of the electromechanical brake torque is controlled by the sliding mode control algorithm to quickly stabilize the actual slip ratio to the optimal slip ratio, and the output braking torque value is recorded. ,in, The sliding mode control algorithm formula is as follows: (6) In the formula: For equivalent braking torque, To switch control torque, For the thickness of the sliding layer, This represents the system state, including the actual slip ratio. With optimal slip ratio Error, such as Figure 2 Phase B.

[0030] Then, maintaining the driving torque, the braking torque output is controlled using a sliding mode control algorithm, ensuring the actual slip ratio remains near the optimal slip ratio, thus achieving precise control of the actual slip ratio. Figure 2 Phase C.

[0031] As the road surface adhesion coefficient increases or the driver's required torque decreases, when the braking torque decreases to... If the duration is maintained at t2, the anti-slip control is considered to have ended and the anti-slip control is discontinued. Figure 2 Phase D.

[0032] In this embodiment, t2 is preferably set to 500ms.

[0033] S07, Control the drive torque output of the drive motor to be reduced to Calculate the actual slip ratio With optimal slip ratio The error is used as the error input, and the sliding mode control algorithm is used to control the output of the electromechanical brake torque, so that the actual slip ratio quickly stabilizes to the optimal slip ratio. Figure 3 Phase B.

[0034] Then, the braking torque is reduced to the pre-clamping torque. And maintain, calculate the actual slip ratio With optimal slip ratio As an error input, a sliding mode control algorithm is used to control the output of the drive motor's driving torque, ensuring that the actual slip ratio is always near the optimal slip ratio, thus achieving precise control of the actual slip ratio. Figure 3 Phase C.

[0035] When the drive motor's driving torque exceeds 90% of the driver's required torque and remains at this level for time t2, the anti-slip control is considered to have ended and is disengaged. Figure 3 Phase D.

[0036] Example 2 This embodiment provides an electromechanical braking system drive anti-skid control system. (Refer to...) Figure 4 The anti-skid control system includes a chassis domain controller 100, an electromechanical brake 200, a drive motor 300, wheel speed sensors 400, and an acceleration sensor 500. There are four electromechanical brakes 200 and four wheel speed sensors 400. One electromechanical brake 200 and one wheel speed sensor 400 are installed on the left front wheel, one on the left rear wheel, one on the right front wheel, and one on the right rear wheel. The wheel speed sensors 400 are used to collect the current wheel speed of their respective tires. The accelerometer 500 is used to collect vehicle acceleration. .

[0037] Reference Figure 4 The chassis domain controller 100 communicates with four wheel speed sensors 400 and an acceleration sensor 500 to adjust the current wheel speed. and vehicle acceleration Real-time assessment of the current maximum permissible driving torque And calculate the actual slip ratio in real time. The chassis domain controller 100 is also communicatively connected to four electromechanical brakes 200 and drive motors 300 to send corresponding control commands to the electromechanical brakes 200 and drive motors 300.

[0038] The above are merely specific embodiments of the present invention, but the design concept of the present invention is not limited thereto. Any non-substantial modifications made to the present invention using this concept shall be considered as infringing upon the protection scope of the present invention.

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 wheel acceleration 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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