Vehicle brake backup method for EMB system failure

Abstract

The invention provides a vehicle brake backup method for EMB system failure, which is based on a central controller and four wheel end EMB controllers and brakes connected with the central controller, and comprises the following steps: S1, collecting signals of a brake pedal, a power system and wheel speed; s2, setting control logic of a wheel end EMB controller relative to a brake pedal, a power system and a wheel speed signal; and S3, the wheel end EMB controller conducts brake clamping and brake releasing on the wheels according to the set control logic. Under the condition that the central controller of the EMB system fails, the driving and braking functions of the vehicle can still be achieved according to the braking intention of a driver, and the safety is improved. Reasonable control logic is set to control the braking speed and the braking torque of the wheel end EMB controller, the wheel anti-lock function is considered, the braking intention of a driver is matched, and the safety principle of emergency braking can also be followed.

Description

Technical Field

[0001] The invention relates to the technical field of vehicle braking, and in particular to a vehicle braking backup method for EMB system failure. Background Art

[0002] At present, new energy vehicles are booming, and the electronic hydraulic braking (EHB) system is becoming more and more popular and applied, with an increasing market share. In the future, the wire control system will completely replace the traditional hydraulic braking system. The EHB system works normally in electronic form. If the electronic control unit fails, the brake will be downgraded to mechanical form. During the implementation of electronic braking, the driver applies the brake pedal, which is processed by the pedal feel simulator and the signal is transmitted to the central controller. The switch of the solenoid valve drives the brake fluid to the wheel end under the action of the motor. The hydraulic pressure acts on the caliper friction plate to clamp the brake disc to realize the braking function of the vehicle. If the electronic control unit fails, the solenoid valve will lose control, and the vehicle will enter the mechanical backup braking mode. The force generated by the driver's action on the brake pedal will drive the brake fluid in the brake master cylinder to the wheel end to generate the corresponding braking force, thereby achieving the braking deceleration required by the braking regulations.

[0003] The EMB system is a complete wire-controlled braking system. All mechanical connections between the brake pedal and the wheel-end brake are eliminated and replaced by wiring harnesses. The driver acts on the electronic brake pedal, and the pedal sensor converts the driver's braking intention into a signal and transmits it to the central controller. The central controller performs relevant analysis and calculations and transmits the command to the wheel-end EMB controller, which controls the motor in the EMB brake to achieve vehicle braking. At present, in order to improve the safety of the EMB system, redundant solutions are designed for related sensors and central controllers. Although the safety is enhanced, most of them use redundant sensors and related controllers, which increases the development cost. Compared with the mechanical backup braking of the EHB system, there is a lack of simple and easy-to-control backup solutions. Considering that EMB is completely wire-controlled and vehicle braking cannot be achieved directly by stepping on the pedal, the present invention proposes a vehicle braking backup solution for EMB system failure. Summary of the invention

[0004] In order to solve the above problems, the present invention discloses a vehicle brake backup method for EMB system failure, which solves the problem of design control cost of redundancy scheme required in the development process of EMB system.

[0005] The specific plan is as follows:

[0006] A vehicle brake backup method for EMB system failure is based on a central controller and four wheel-end EMB controllers and brakes connected thereto, comprising the following steps:

[0007] S1: Collect signals from the brake pedal, power system, and wheel speed;

[0008] S2: Set the control logic of the wheel-end EMB controller relative to the brake pedal, power system and wheel speed signal;

[0009] S3: The wheel-end EMB controller clamps and releases the brakes on the wheels according to the set control logic.

[0010] Furthermore, in step S2, the control logic is:

[0011] S21: When the driver steps on the brake pedal, the wheel-end EMB controller performs braking control according to the speed, depth and wheel speed of the driver's stepping on the brake pedal;

[0012] S22: When the driver releases the brake pedal, the wheel-end EMB controller performs brake release control according to the stroke of the released brake pedal and the strength of the power system.

[0013] Furthermore, the step S21 specifically includes the following steps:

[0014] S211, setting a response time threshold of the central controller acting on the wheel-end EMB controller, and executing a braking backup solution when the threshold is exceeded;

[0015] S212, collecting the ratio of the brake pedal's pedal stroke to the total stroke and setting it to q%, and collecting the brake pedal's pedaling speed Q;

[0016] Q=q% / Δt

[0017] Among them, Δt is the total time of a certain stroke;

[0018] S213, calculating the corresponding braking force applied torque and the response rate of the EMB motor applying the braking torque according to the following formula:

[0019] V=k1*Q

[0020] T=k2*q%*(w / k3)

[0021] Among them, V is the response rate of the EMB motor that applies braking torque; T is the applied braking torque; k1 and k2 are correlation coefficients; w is the wheel speed; k3 is the correlation coefficient related to the wheel speed, and k1, k2, and k3 are all greater than 0, which are the values ​​finally optimized during the test process.

[0022] Furthermore, the step S22 specifically includes the following steps:

[0023] S221, collecting the ratio b% of the release stroke of the brake pedal, that is, the return stroke to the total stroke, and collecting the strength coefficient of the power system, recorded as G, the value of G is derived from the ratio of the strength of the current power system to the total strength;

[0024] S222. Calculate the speed of releasing the braking force according to the relevant formula:

[0025] V 1 =k4*b%*G n

[0026] Among them, V 1 is the speed at which the braking force is released; k4 is the correlation coefficient; n is the correlation coefficient of the power intensity coefficient. Both k4 and n are greater than 0, which are the values ​​finally optimized during the test.

[0027] The beneficial effects of the present invention are:

[0028] 1. In the case of failure of the central controller of the EMB system, the present invention can still realize the driving and braking functions of the vehicle according to the driver's braking intention, thereby improving safety.

[0029] 2. The present invention sets reasonable control logic to control the braking rate and braking torque of the wheel-end EMB controller, and takes the wheel anti-lock function into consideration, which not only matches the driver's braking intention, but also complies with the safety principle of emergency braking. BRIEF DESCRIPTION OF THE DRAWINGS

[0030] Figure 1 It is a logic diagram of the method of the present invention. DETAILED DESCRIPTION

[0031] The present invention will be further explained below in conjunction with the accompanying drawings and specific embodiments. It should be understood that the following specific embodiments are only used to illustrate the present invention and are not used to limit the scope of the present invention.

[0032] As shown in the figure, the present invention provides a vehicle brake backup method for EMB system failure, based on a central controller and four wheel-end EMB controllers and brakes connected thereto, comprising the following steps:

[0033] S1: Collect signals from the brake pedal, power system, and wheel speed;

[0034] S2: Set the control logic of the wheel-end EMB controller relative to the brake pedal, power system and wheel speed signal;

[0035] S3: The wheel-end EMB controller clamps and releases the brakes on the wheels according to the set control logic.

[0036] In this embodiment, in step S2, the control logic is:

[0037] S21: When the driver steps on the brake pedal, the wheel-end EMB controller performs braking control according to the speed, depth and wheel speed of the driver's stepping on the brake pedal;

[0038] S22: When the driver releases the brake pedal, the wheel-end EMB controller performs brake release control according to the stroke of the released brake pedal and the strength of the power system.

[0039] In this embodiment, step S21 specifically includes the following steps:

[0040] S211, setting a response time threshold of the central controller acting on the wheel-end EMB controller, and executing a braking backup solution when the threshold is exceeded;

[0041] S212, collecting the ratio of the brake pedal's pedal stroke to the total stroke and setting it to q%, and collecting the brake pedal's pedaling speed Q;

[0042] Q=q% / Δt

[0043] Among them, Δt is the total time of a certain stroke;

[0044] S213, calculating the corresponding braking force applied torque and the response rate of the EMB motor applying the braking torque according to the following formula:

[0045] V=k1*Q

[0046] T=k2*q%*(w / k3)

[0047] Among them, V is the response rate of the EMB motor that applies braking torque; T is the applied braking torque; k1 and k2 are correlation coefficients; w is the wheel speed; k3 is the correlation coefficient related to the wheel speed, and k1, k2, and k3 are all greater than 0, which are the values ​​finally optimized during the test process.

[0048] In this embodiment, step S22 specifically includes the following steps:

[0049] S221, collecting the ratio b% of the release stroke of the brake pedal, that is, the return stroke to the total stroke, and collecting the strength coefficient of the power system, recorded as G, the value of G is derived from the ratio of the strength of the current power system to the total strength;

[0050] S222. Calculate the speed of releasing the braking force according to the relevant formula:

[0051] V 1 =k4*b%*G n

[0052] Among them, V 1is the speed at which the braking force is released; k4 is the correlation coefficient; n is the correlation coefficient of the power intensity coefficient. Both k4 and n are greater than 0, which are the values ​​finally optimized during the test.

[0053] The technical means disclosed in the scheme of the present invention are not limited to the technical means disclosed in the above-mentioned implementation mode, but also include technical schemes composed of any combination of the above-mentioned technical features. It should be pointed out that for ordinary technicians in this technical field, several improvements and modifications can be made without departing from the principle of the present invention, and these improvements and modifications are also regarded as the protection scope of the present invention.

Claims

1. A vehicle brake backup method for EMB system failure, characterized in that: Based on the central controller and the four wheel-end EMB controllers and brakes connected thereto, the following steps are included: S1: Collect signals from the brake pedal, power system, and wheel speed; S2: Set the control logic of the wheel-end EMB controller relative to the brake pedal, power system and wheel speed signal; S3: The wheel-end EMB controller clamps and releases the brakes on the wheels according to the set control logic.

2. A vehicle brake backup method for EMB system failure according to claim 1, characterized in that: In step S2, the control logic is: S21: When the driver steps on the brake pedal, the wheel-end EMB controller performs braking control according to the speed, depth and wheel speed of the driver's stepping on the brake pedal; S22: When the driver releases the brake pedal, the wheel-end EMB controller performs brake release control according to the stroke of the released brake pedal and the strength of the power system.

3. The vehicle brake backup method for EMB system failure according to claim 2, characterized in that: The step S21 specifically includes the following steps: S211, setting a response time threshold of the central controller acting on the wheel-end EMB controller, and executing a braking backup solution when the threshold is exceeded; S212, collecting the ratio of the brake pedal's pedal stroke to the total stroke and setting it to q%, and collecting the brake pedal's pedaling speed Q; Q=q% / Δt Among them, Δt is the total time of a certain stroke; S213, calculating the corresponding braking force applied torque and the response rate of the EMB motor applying the braking torque according to the following formula: V=k1*Q T=k2*q%*(w / k3) Among them, V is the response rate of the EMB motor applying braking torque; T is the applied braking torque; k1 and k2 are correlation coefficients; w is the wheel speed; k3 is the correlation coefficient related to the wheel speed, and k1, k2, and k3 are all greater than 0.

4. The vehicle brake backup method for EMB system failure according to claim 3, characterized in that: The step S22 specifically includes the following steps: S221, collecting the ratio b% of the release stroke of the brake pedal, that is, the return stroke to the total stroke, and collecting the strength coefficient of the power system, denoted as G, where the value of G is derived from the ratio of the strength of the current power system to the total strength; S222. Calculate the speed of releasing the braking force according to the relevant formula: V 1 =k4*b%*G n Among them, V 1 is the speed at which the braking force is released; k4 is the correlation coefficient; n is the correlation coefficient of the power intensity coefficient, and both k4 and n are greater than 0.

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