Deceleration control method after failure of braking system of electric automobile and automobile

Abstract

The invention discloses a deceleration control method after failure of a brake system of an electric automobile and the automobile, and the method comprises the following steps: monitoring the working state of the brake system in real time in the running process of the automobile, limiting the maximum speed of the automobile through a VCU (Vehicle Control Unit) after monitoring the failure of the brake system, and controlling the deceleration of the automobile through the VCU after detecting that a brake pedal is triggered. And the vehicle is controlled to slow down by controlling the driving motor to be in an energy recovery mode and / or controlling the ESC / EPB to be in a parking braking mode. The method has the advantages that linkage braking is achieved through multiple braking strategies, rapid and stable braking control is achieved, meanwhile, the vehicle speed is limited after braking failure is detected, and the safety risk that rapid braking cannot be achieved due to the fact that the vehicle speed is too high is avoided.

Description

Technical Field

[0001] The present invention relates to the field of brake control of new energy electric vehicles, and in particular to a deceleration control method after a brake system of an electric vehicle fails. Background Art

[0002] The automobile braking system is the core system of vehicle braking. During driving, once an accident occurs, it will lead to the inability to brake and thus cause a traffic accident. After the driving brake system fails, the car cannot perform deceleration control, which is very dangerous for the use of the vehicle; therefore, in the prior art, a redundant backup method of the brake system is often used to reduce the probability of failure of the brake system, such as a double backup large-liquid electronic power-assisted brake with patent application number 202110535319.4, which includes a first and a second electronic power-assisted brake, the first electronic power-assisted brake includes a first cylinder, a second cylinder, a first main push rod and a first power-assisted motor, the first cylinder is connected in series with the second cylinder, the rear end of the first main push rod is hinged with the pedal, and the front end is connected with the second cylinder piston rod, the second electronic power-assisted brake includes a third cylinder, a fourth cylinder, a second main push rod and a second power-assisted motor, the third cylinder is connected in series with the fourth cylinder, the rear end of the second main push rod is connected in parallel with the first main push rod, and the front end is connected with the fourth cylinder piston rod, the first cylinder is connected in parallel with the third cylinder, and the second cylinder is connected in parallel with the fourth cylinder.

[0003] The above patent discloses a method of providing stable reliability of the braking system through redundant backup, avoiding the problem of being unable to brake due to failure of the braking system. However, the backup of the braking system means that two sets of braking systems are required, which increases the development cost of the vehicle. Therefore, the prior art proposes to use the EPB function installed on the vehicle to realize the braking control after the vehicle fails in the parking method, but because the parking wheels are generally on the rear wheels, the overall deceleration cannot be too large, the braking distance will be long, and accidents are very easy to occur. Therefore, the braking control strategy after the failure of the braking system in the prior art cannot meet the user's demand for safe backup of braking. Summary of the invention

[0004] The purpose of the present invention is to overcome the shortcomings of the prior art and provide a deceleration control method after the braking system of an electric vehicle fails. The method realizes fast and stable braking control by linking braking with multiple braking strategies. At the same time, the vehicle speed is limited after the braking failure is detected to avoid the safety risk of being unable to brake quickly due to excessive speed.

[0005] In order to achieve the above-mentioned purpose, the technical solution adopted by the present invention is: a deceleration control method after the failure of the braking system of an electric vehicle, including real-time monitoring of the working status of the braking system during vehicle driving, and when a braking system failure is detected, limiting the maximum speed of the vehicle through the vehicle controller VCU, and after detecting that the brake pedal is triggered, controlling the vehicle deceleration by controlling the drive motor to be in energy recovery mode and or the ESC / EPB to be in parking brake mode.

[0006] When the vehicle is driving, the master cylinder pressure signal, vehicle speed change signal or wheel end speed change signal after the brake pedal is stepped on is detected in real time to determine whether the brake system is faulty.

[0007] After determining that the brake system fails, the corresponding maximum vehicle speed value is obtained according to the vehicle's current environment, and the vehicle speed is limited by the maximum vehicle speed value.

[0008] After a braking system failure, if the brake pedal is not pressed and the vehicle's real-time speed is greater than the maximum speed, the VCU will limit the torque of the drive motor and control the drive motor in energy recovery mode to reduce the real-time speed to below the maximum speed.

[0009] Different maximum speed values ​​are set according to the type of road the vehicle is on, and the road surface or positioning position is obtained through sensors to determine the current road type.

[0010] When the braking system fails, the depth of the brake pedal pressed by the driver is converted into the vehicle deceleration requirement at that time, and the deceleration requirement is converted into the energy recovery torque value corresponding to the drive motor. The converted energy recovery torque value is used to control the drive motor to recover energy for deceleration control.

[0011] When the converted energy recovery torque value is greater than the maximum recovery torque that the drive motor can provide, the maximum recovery torque is used to control the vehicle's energy recovery. At the same time, the vehicle's deceleration is monitored to obtain the real-time deceleration, and then the ESC / EPB is controlled to perform parking braking to increase the deceleration so that the real-time deceleration approaches the vehicle's deceleration requirement or the deceleration provided by the ESC / EPB reaches the threshold.

[0012] After the vehicle speed drops to the set speed threshold, the VCU sends a parking request through the ESC or EPB controller, decelerates to 0 and stops the vehicle through the parking brake, and controls the drive motor to stop working.

[0013] After a brake system failure is detected, a corresponding alarm reminder signal is sent to the driver through the vehicle's multimedia or instrument.

[0014] An electric vehicle adopts the deceleration control method to perform deceleration control on the vehicle after a brake system failure occurs.

[0015] The advantages of the present invention are: through the linkage braking of multiple braking strategies, fast and stable braking control is achieved, and at the same time, the vehicle speed is limited after the brake failure is detected, avoiding the safety risk of not being able to brake quickly due to excessive speed. This solution realizes a safe and effective deceleration control method for the vehicle when the service brake system fails; it does not increase the cost of additional parts on conventional electric vehicles, and realizes redundant backup braking. BRIEF DESCRIPTION OF THE DRAWINGS

[0016] The following is a brief description of the contents expressed in the drawings of the present invention and the symbols in the drawings:

[0017] Figure 1 This is a flow chart of the control method of the present invention. DETAILED DESCRIPTION

[0018] The specific implementation of the present invention will be further explained in detail below by describing the optimal embodiment with reference to the accompanying drawings.

[0019] Compared with the redundant backup of the braking system in the prior art, this solution does not increase the hardware cost. Although it is also a redundant backup, the redundant backup of this solution adopts the energy recovery braking of the motor and the ESC and EPB braking for parking. Since the vehicle has ESC or EPB and energy recovery mode, this redundant backup braking does not increase the hardware cost. There is only the development cost of the software control strategy, which is suitable for OTA upgrades of new cars or vehicles that have been sold.

[0020] The system components involved in the control method of this solution include:

[0021] Motor: It can be a drive motor that provides power to the entire vehicle, or it can be a generator in the vehicle power system that provides energy conversion for driving;

[0022] Motor controller: a controller that controls the motor output torque;

[0023] VCU: Vehicle Controller, a controller that outputs the required torque to the motor controller based on the real-time environment of the vehicle system.

[0024] ESC: vehicle dynamic control system, which integrates brake pressure sensor and longitudinal acceleration sensor;

[0025] EPB: Electronic parking brake controller, independent electronic parking control unit is installed on the brake pedal brake light switch, its on and off is realized when the pedal is stepped on; the travel sensor installed on the brake pedal, it outputs a corresponding nearly linear travel signal as the pedal is stepped on.

[0026] The control method includes: during driving braking, if:

[0027] ①After the pedal is pressed, the ESC system does not detect the master cylinder pressure, deceleration occurs, or the wheel end speed does not decrease;

[0028] ②The ESC system sends a driving system fault signal;

[0029] ③ When the driver steps on the brake pedal, the VCU sends the energy recovery torque value to the motor controller according to the change in the depth of the travel sensor;

[0030] ④After receiving the second signal, the VCU limits the maximum positive torque of the drive motor data, that is, limits the maximum vehicle speed;

[0031] ⑤ Through comprehensive judgment by the wheel speed sensor and the ESC internal acceleration sensor, when the vehicle speed drops to a specific value (calibrable value), the VCU sends a parking request to the ESC or EPB controller to achieve final parking of the vehicle.

[0032] like Figure 1 As shown, the solution of this embodiment is further described below in conjunction with the accompanying drawings as follows:

[0033] A deceleration control method for an electric vehicle after a braking system fails, comprising the following steps:

[0034] The working status of the braking system is monitored in real time during the driving process of the vehicle. When a braking system failure is detected, the maximum speed of the vehicle is limited through the vehicle controller VCU, and after the brake pedal is detected to be triggered, the vehicle is decelerated by controlling the drive motor to be in energy recovery mode and or ESC / EPB to be in parking brake mode. Since the efficiency is relatively low when the braking system fails, the VCU responds to the user's braking needs through the braking system when the braking system is not faulty; when a failure occurs, the braking control can be performed through braking energy recovery and parking brake as redundant backup.

[0035] The method for judging whether the brake system is faulty or ineffective includes: during the driving process of the vehicle, real-time detection of the master cylinder pressure signal or the vehicle speed change signal or the wheel speed change signal after the brake pedal is stepped on to judge whether the brake system is faulty. When the brake pedal is stepped on, generally, the master cylinder pressure signal will change or the vehicle speed will change. Therefore, after the brake pedal is stepped on, the change trend of the master cylinder pressure signal or the vehicle speed can be monitored to judge whether the brake system is normal. If the master cylinder pressure remains unchanged or the vehicle speed remains unchanged or only changes slightly after the brake pedal is stepped on (this slight change may be caused by deceleration due to friction after the accelerator pedal is released), it can be judged that the brake system is faulty or ineffective.

[0036] After judging the brake system failure, the corresponding maximum speed value is obtained according to the current environment of the vehicle, and the vehicle speed is limited by the maximum speed value. After judging the brake system failure, whether the brake pedal is pressed or not, the maximum speed of the vehicle needs to be limited at this time, and the maximum speed can be set according to the road type. Different maximum speed values ​​are set according to the type of road the vehicle is on, and the road surface or positioning position is obtained by the sensor to determine the current road type. For example, the vehicle's camera is used to collect the road surface status or the position is obtained through GPS, and the map is combined with the positioning to determine whether the current road type of the vehicle is a highway, urban road, rural road, etc., and then the corresponding pre-set maximum speed value is adaptively obtained according to the road type, and then the vehicle speed is controlled to be less than this speed value according to the maximum speed value.

[0037] After a braking system failure, if the brake pedal is not pressed and the vehicle's real-time speed is greater than the maximum speed, the VCU will limit the torque of the drive motor and control the drive motor in energy recovery mode to reduce the real-time speed to below the maximum speed. Although the driver has not pressed the brake pedal and there is no need to brake, the braking system is in a failed state and therefore the speed needs to be limited in advance to avoid the subsequent safety hazard of being unable to brake due to excessive speed. Therefore, the speed is automatically limited to below the maximum speed to avoid the occurrence of safety hazards.

[0038] After the brake system fails or fails, in order to better meet the driver's braking needs, the motor braking in the motor energy recovery mode and the electronic parking brake of ESC / EPB can be combined to meet the driver's braking needs. At the same time, it is also necessary to issue a prompt through the instrument or multimedia after the brake fails, prompting the driver to pull over or repair it in time. When the brake system fails, the depth of the brake pedal pressed by the driver is converted into the vehicle deceleration requirement at this time, and the deceleration requirement is converted into the energy recovery torque value corresponding to the drive motor. The converted energy recovery torque value is used to control the drive motor to recover energy for deceleration control.

[0039] When the converted energy recovery torque value is greater than the maximum recovery torque that the drive motor can provide, the maximum recovery torque is used to control the vehicle's energy recovery. At the same time, the vehicle's deceleration is monitored to obtain the real-time deceleration, and then the ESC / EPB is controlled to perform parking braking to increase the deceleration so that the real-time deceleration approaches the vehicle's deceleration requirement or the deceleration provided by the ESC / EPB reaches the threshold.

[0040] When the deceleration demand can be met by the energy recovery torque of the driving motor, the torque generated by the motor energy recovery mode is used for deceleration control. When it cannot be met, EPB and ESC are also added to perform speed reduction control to meet the braking demand at this time as much as possible. Although the addition of EPB at this time may cause damage to the EPB system, compared with the safety hazard of not being able to meet the user's braking needs, damage to vehicle parts is acceptable for safety. However, after EPB is added to the brakes, the deceleration provided by EPB is certain. If the deceleration provided by EPB is too large, it will cause safety hazards such as skidding. Therefore, the deceleration threshold that EPB can provide is set, and the general threshold is set to less than 0.2G. After the braking recovery energy cannot be met, EPB is controlled to provide deceleration. The maximum deceleration that EPB can provide is 0.2G, and it will no longer increase after reaching it.

[0041] After the vehicle speed drops to the set speed threshold, the VCU sends a parking request through the ESC or EPB controller, decelerates to 0 and stops the vehicle through the parking brake, and controls the drive motor to stop working, thereby completing the braking requirements after deceleration.

[0042] After a brake system failure is detected, a corresponding alarm reminder signal is sent to the driver through the vehicle multimedia or instrument. The reminder is sent through the instrument or multimedia to prompt the driver to pull over or repair the car in time, and try to avoid driving the car in the case of brake failure or failure, thereby improving safety.

[0043] In a preferred embodiment of the present application, an electric vehicle is also provided, which adopts the deceleration control method in the above embodiment to control the deceleration of the vehicle after a brake system failure. Since the vehicle includes all the features of the deceleration control method, it has all its technical advantages, including that when the driver steps on the brake pedal, the VCU sends an energy recovery torque value to the motor controller according to the change in the depth of the stroke sensor, and finally parks the vehicle to achieve complete stopping of the vehicle, and has the advantages of safety, reliability, redundant backup and low cost.

[0044] In this solution, the ESC system detects a fault in the service brake system and sends a fault signal; when the driver steps on the brake pedal, the VCU sends an energy recovery torque value to the motor controller based on the change in the depth of the travel sensor; after receiving the fault signal from the ESC, the VCU limits the maximum vehicle speed; after the vehicle is decelerated by energy recovery, it finally stops.

[0045] Obviously, the specific implementation of the present invention is not limited to the above-mentioned methods. As long as various non-substantial improvements are made using the method concept and technical solution of the present invention, they are all within the protection scope of the present invention.

Claims

1. A deceleration control method after a brake system failure of an electric vehicle, characterized in that: It includes real-time monitoring of the working status of the braking system during vehicle driving. When a braking system failure is detected, the vehicle's maximum speed is limited by the vehicle controller VCU. After detecting that the brake pedal is triggered, the vehicle is decelerated by controlling the drive motor to be in energy recovery mode and or the ESC / EPB to be in parking brake mode.

2. The deceleration control method after the failure of the electric vehicle brake system as claimed in claim 1, characterized in that: When the vehicle is driving, the master cylinder pressure signal, vehicle speed change signal or wheel end speed change signal after the brake pedal is stepped on is detected in real time to determine whether the brake system is faulty.

3. The deceleration control method after the failure of the electric vehicle braking system as claimed in claim 1, characterized in that: After determining that the brake system fails, the corresponding maximum vehicle speed value is obtained according to the vehicle's current environment, and the vehicle speed is limited by the maximum vehicle speed value.

4. The deceleration control method after the failure of the electric vehicle brake system as claimed in claim 3, characterized in that: After a braking system failure, if the brake pedal is not pressed and the vehicle's real-time speed is greater than the maximum speed, the VCU will limit the torque of the drive motor and control the drive motor in energy recovery mode to reduce the real-time speed to below the maximum speed.

5. The deceleration control method after the failure of the electric vehicle brake system as claimed in claim 3, characterized in that: Different maximum speed values ​​are set according to the type of road the vehicle is on, and the road surface or positioning position is obtained through sensors to determine the current road type.

6. A deceleration control method after a brake system failure of an electric vehicle as claimed in any one of claims 1 to 5, characterized in that: When the braking system fails, the depth of the brake pedal pressed by the driver is converted into the vehicle deceleration requirement at that time, and the deceleration requirement is converted into the energy recovery torque value corresponding to the drive motor. The converted energy recovery torque value is used to control the drive motor to recover energy for deceleration control.

7. The deceleration control method after the brake system of an electric vehicle fails as claimed in claim 6, characterized in that: When the converted energy recovery torque value is greater than the maximum recovery torque that the drive motor can provide, the maximum recovery torque is used to control the vehicle's energy recovery. At the same time, the vehicle's deceleration is monitored to obtain the real-time deceleration, and then the ESC / EPB is controlled to perform parking braking to increase the deceleration so that the real-time deceleration approaches the vehicle's deceleration requirement or the deceleration provided by the ESC / EPB reaches the threshold.

8. A deceleration control method after a brake system failure of an electric vehicle as claimed in any one of claims 1 to 7, characterized in that: After the vehicle speed drops to the set speed threshold, the VCU sends a parking request through the ESC or EPB controller, decelerates to 0 and stops the vehicle through the parking brake, and controls the drive motor to stop working.

9. A deceleration control method after a brake system failure of an electric vehicle as claimed in any one of claims 1 to 7, characterized in that: After a brake system failure is detected, a corresponding alarm reminder signal is sent to the driver through the vehicle's multimedia or instrument.

10. An electric vehicle, characterized in that: The electric vehicle uses the deceleration control method as described in any one of claims 1 to 9 to perform deceleration control on the vehicle after a brake system failure.

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