A vacuum pump control method with fault detection and motor regenerative braking compensation

Abstract

In order to accurately cope with the vacuum booster system failure, improve the driving safety, the present application provides a kind of vacuum pump control method with fault detection and motor feedback compensation brake, vehicle controller obtains vacuum degree, vacuum pump relay working time, vehicle speed, brake pedal stroke and other signals to judge the state of vehicle vacuum booster system to control vacuum pump, and the fault is divided into general leakage fault, vacuum sensor fault, serious fault, and according to the fault state control adjusts the working mode of vacuum pump, and the intensity of brake feedback is appropriately increased according to the threshold value of vacuum degree and the stroke value of brake pedal, to compensate for the shortage of brake assist, so as to improve the service life of vacuum pump and driving safety on the basis of not affecting the driving feeling of driver.

Description

Technical Field

[0001] This invention relates to the field of vehicle technology, and in particular to a vacuum pump control method with fault detection and motor feedback compensation braking. Background Technology

[0002] The braking assist system in pure electric vehicles comes from a vacuum pump. The vacuum assist system operates frequently and plays an indispensable role in the vehicle's braking system. When the braking assist system malfunctions, if corresponding measures are not taken in time, the brake pedal will become hard, increasing the risk to driving safety. Summary of the Invention

[0003] The purpose of this invention is to logically determine the state of the vacuum booster system by using a vacuum sensor, brake pedal travel value, and vacuum pump operating time, and to take different handling methods under different fault conditions to ensure driving braking safety. At the same time, in conjunction with the regenerative braking of the pure electric vehicle motor, it enables the driver to easily control the vehicle according to driving habits even when the vacuum booster system malfunctions.

[0004] To achieve the above objectives, the present invention provides a vacuum pump control method with fault detection and motor regenerative braking, the technical solution of which is as follows:

[0005] A vacuum pump control method with fault detection and motor regenerative braking, characterized in that the method includes:

[0006] Acquire the signal from the vacuum sensor over a certain period of time and calculate the rate of change of vacuum level;

[0007] Obtain the brake pedal travel value and calculate the rate of change of the brake pedal travel value;

[0008] Obtain real-time vehicle speed signals;

[0009] Based on the above signals, the vehicle controller classifies the vacuum booster system into three categories: general leakage fault, sensor fault, and severe leakage fault.

[0010] Common leakage faults:

[0011] When the rate of change of brake pedal travel is ≤ a1, the rate of change of vacuum degree is ≤ b1, and the filtering continues for a preset time, the vacuum booster system is determined to have entered a general leakage fault.

[0012] If the vacuum pump relay's working time has not reached the first preset time and the vacuum level has not reached the vacuum level threshold corresponding to the vehicle's current speed, the vehicle controller will control the vacuum pump to stop working.

[0013] Vacuum sensor malfunction:

[0014] The vehicle controller determines whether the vacuum sensor is short-circuited or open-circuited based on the voltage value of the internal hard-wired circuit. At the same time, if the vacuum level is continuously ≤d2, the brake pedal travel is greater than c, and the vacuum level does not change or the rate of change is less than b2 after the pedal returns to its original position, the vacuum sensor is determined to be faulty.

[0015] Critical leakage fault:

[0016] When the brake pedal travel change rate is ≤ a1 and the vacuum degree is > d1 for more than the second preset time, or when the brake pedal travel change rate is ≤ a2 and the vacuum pump continues to work for more than the third preset time, the vacuum booster system is determined to have entered a serious leakage fault. At this time, the vehicle controller limits the maximum vehicle speed to no more than the first vehicle speed and controls the vacuum pump to start and stop intermittently and work in a cycle. At the same time, the motor regenerative braking is activated. The magnitude of the motor regenerative compensation torque follows the product of the difference in brake vacuum degree and the motor regenerative compensation torque MAP.

[0017] ;

[0018] in:

[0019] The first speed is the critical value for determining whether the vehicle is in a low-speed or high-speed driving state.

[0020] a1 is the first preset threshold value for the rate of change of brake pedal travel;

[0021] a2 is the second preset threshold value for the rate of change of brake pedal travel;

[0022] c represents the minimum pedal travel value for driver intervention in the braking system;

[0023] b1 represents the maximum rate of change of vacuum under normal conditions, when the rate of change of the brake pedal is a1.

[0024] b2 is the minimum rate of change of vacuum under normal conditions, when the brake pedal travel is greater than c and the pedal returns to its original position;

[0025] d1 is the minimum vacuum level required by the vacuum pump assist system;

[0026] d3 is the minimum threshold of the vacuum sensor when the vehicle speed is greater than the first vehicle speed;

[0027] d1 > d3.

[0028] Furthermore, the method also includes:

[0029] After determining that the vacuum booster system has entered a general leakage fault, if the vehicle speed is less than the first vehicle speed and the vacuum degree is ≥d2, the vehicle controller controls the vacuum pump to start working until the vacuum pump relay working time has not reached the first preset time and the vacuum degree is ≤d4, at which point the vacuum pump stops working.

[0030] If the vehicle speed is greater than the first vehicle speed and the vacuum degree is ≥d3, the vehicle controller controls the vacuum pump to start working until the vacuum pump relay clock has not reached the first preset time and the vacuum degree is ≤d4, at which point the vacuum pump stops working.

[0031] Where: d2 is the threshold of the vacuum sensor when the vacuum pump is off, d4 is the threshold of the vacuum pump when it is on, and d1 > d2 > d3 > d4.

[0032] Furthermore, the method also includes: after determining that the vacuum booster system has entered a general leakage fault, a vacuum sensor fault, or a serious leakage fault, the vehicle controller sends a fault signal to the instrument panel to display the corresponding fault information.

[0033] Furthermore, the method also includes:

[0034] In the event of a general leakage fault or a vacuum sensor fault, if the vacuum pump operates for more than the first preset time and d4≤vacuum≤d2, the vehicle controller will stop the vacuum pump. When the brake pedal travel value increases in the positive direction, the vacuum pump operating time will be reset.

[0035] Furthermore, the method also includes:

[0036] When the vehicle controller determines that the vacuum booster system has entered a vacuum sensor failure state, the vehicle controller controls the vacuum pump to work according to the brake signal. After the brake signal stops, the vacuum pump will work continuously for a preset time and then stop.

[0037] The beneficial effects of this invention are as follows:

[0038] 1. Using the brake pedal travel value and the rate of change of vacuum to make judgments can more dynamically determine faults and avoid misjudgments when the vacuum remains unchanged when the brake pedal is depressed.

[0039] 2. By using hardware voltage feedback and the dynamic process of the brake pedal being pressed and returned to determine the change in vacuum, the problem of the sensor getting stuck and unable to make a judgment within the measurement range can be solved.

[0040] 3. Compensation is achieved using the difference ratio between the motor feedback compensation torque MAP and the vacuum level. When a serious malfunction occurs in the vacuum booster system, the vehicle controller obtains the brake pedal travel value and the current vehicle speed. After adjusting the brake torque compensation using the motor feedback compensation torque MAP, the vehicle controller again performs PID torque compensation adjustment based on the obtained current vacuum level difference ratio. The smaller the vacuum level difference ratio, the smaller the motor feedback compensation torque, resulting in less intervention in driving behavior. This ensures safety while closely aligning with the driver's daily driving habits.

[0041] 4. Fault diagnosis and vacuum pump control of the vacuum booster system are controlled in a closed loop by the vehicle controller, reducing the risk of node failures. Simultaneously, in the vacuum booster system fault mode, the vehicle control can compensate for torque through drive motor feedback, ensuring a comfortable driving experience for the driver when vacuum booster is insufficient, with braking distances nearly identical to normal under the same braking force. Attached Figure Description

[0042] Figure 1 This is a control principle diagram of the present invention.

[0043] Figure 2 This is a schematic diagram of the fault diagnosis principle of the present invention.

[0044] Figure 3 This is a schematic diagram of the fault handling principle of the present invention.

[0045] Figure 4 Schematic diagram of motor feedback torque compensation

[0046] Figure 5 Circuit diagram for motor feedback compensation torque control

[0047] Figure 6 Schematic diagram of brake pedal change rate

[0048] Figure 7 Schematic diagram of vacuum degree threshold Detailed Implementation

[0049] Exemplary embodiments of the present disclosure will now be described in more detail with reference to the accompanying drawings. While exemplary embodiments of the present disclosure are shown in the drawings, it should be understood that the present disclosure may be implemented in various forms and should not be limited to the embodiments set forth herein. Rather, these embodiments are provided so that this disclosure will be thorough and complete, and will fully convey the scope of the disclosure to those skilled in the art.

[0050] In the description of the invention, it should be understood that the terms "upper", "lower", "front", "back", "left", "right", "vertical", "horizontal", "top", "bottom", "inner", "outer", etc., indicate the orientation or positional relationship based on the view direction or positional relationship, and are only for the convenience of describing the invention, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation, and therefore should not be construed as a limitation on the invention.

[0051] like Figures 1 to 7 The vacuum pump control method shown here, which features fault detection and motor regenerative braking, is based on the vehicle controller, vacuum sensor, brake pedal, vehicle speed, and vacuum pump relay. The control method is as follows:

[0052] The vehicle controller acquires the vacuum level signal from the vacuum sensor over a certain period of time and calculates the rate of change of vacuum level; acquires the brake pedal travel value and calculates the rate of change of brake pedal travel value; and acquires the real-time vehicle speed signal.

[0053] The vehicle controller determines the fault status of the vacuum booster system based on the vacuum degree change rate, brake pedal travel change rate, vehicle speed, and vacuum degree signals. This includes general leakage faults, vacuum sensor faults, and severe leakage faults. Specifically:

[0054] Common leakage faults:

[0055] When the rate of change of brake pedal travel is ≤ a1 and the rate of change of vacuum is ≤ b1, and after continuous filtering for 5 seconds, the vehicle controller determines that the vacuum booster system has entered a general leakage fault.

[0056] When the vacuum booster system enters a general leakage fault, it sends a general fault signal to the instrument panel to alert the driver that the brake system vacuum booster is faulty.

[0057] Under normal leakage fault conditions of the vacuum booster system, when the vehicle speed is less than the first vehicle speed s and the vacuum degree is ≥d2, the vehicle controller controls the vacuum pump relay to engage and the vacuum pump starts to work. When the working time of the vacuum pump relay has not reached the first preset time of 15s and the vacuum degree is ≤d4, the vacuum pump stops working.

[0058] When the vehicle speed is greater than or equal to the first vehicle speed s and the vacuum degree is ≥d3, the vehicle controller controls the vacuum pump relay to engage and the vacuum pump starts to work. When the vacuum pump relay working time has not reached the first preset time of 15s and the vacuum degree is ≤d4, the vacuum pump stops working.

[0059] When the vacuum pump operates for more than 15 seconds and d4 ≤ vacuum degree ≤ d2, the vacuum pump stops working. When the brake pedal travel value increases in the positive direction, the vacuum pump operating time is reset.

[0060] Among them, the first vehicle speed s is the speed used to determine whether the vehicle is in a high-speed or low-speed driving state. When the vehicle speed is greater than or equal to the first vehicle speed, the vehicle is in a high-speed driving state; otherwise, it is in a low-speed driving state. The first vehicle speed value can be set according to different vehicle models.

[0061] a1 is the first preset threshold for the rate of change of the direct-access pedal travel value, which is the minimum resolution of n times the brake pedal travel value. The smaller the value of a1, the higher the detection accuracy, but the greater the detection error. In this embodiment, a1 is 10 times the minimum resolution of the brake pedal travel.

[0062] b1 is the first preset vacuum change rate threshold, which represents the maximum change rate of vacuum when the brake pedal travel value changes at a1 under normal conditions;

[0063] d2 is the threshold value of the vacuum sensor when the vacuum pump is off, d3 is the minimum threshold value of the vacuum sensor when the vehicle is traveling at high speed, and d4 is the threshold value of the vacuum sensor when the vacuum pump is on, and d2 > d3 > d4.

[0064] Vacuum sensor malfunction:

[0065] When the vehicle controller determines whether the vacuum sensor is short-circuited or open-circuited based on the voltage value of the internal hard-wired circuit, and when the vacuum sensor detects a vacuum level that is continuously ≤d2, the brake pedal travel value is ≥c, and after the pedal returns to its original position, the vacuum level remains unchanged or the rate of change is ≤b2, the vacuum booster system is determined to have entered a vacuum sensor fault state.

[0066] At this time, the vehicle controller sends a fault signal from the vacuum booster system vacuum sensor to the instrument panel. At the same time, it controls the vacuum pump to work according to the brake signal. After receiving the brake signal, the vacuum pump starts to work. After the brake signal stops, the vacuum pump works continuously for 10 seconds and then stops working.

[0067] If the vacuum booster system enters a vacuum sensor failure state, and the vacuum pump continues to work for more than 15 seconds with d4≤vacuum degree≤d2, the vacuum pump will stop working. When the brake pedal travel value increases in the positive direction, the vacuum pump working time will be reset.

[0068] c is a preset brake pedal travel threshold value, representing the minimum pedal travel value at which the driver intervenes in the braking system. c is a constant value, generally taken as 10% to 30% of the brake pedal travel. In this embodiment, c is taken as 20%.

[0069] b2 represents the minimum rate of change in vacuum when the brake pedal travel value is ≥ c and the pedal returns to its original position under normal conditions.

[0070] Critical leakage fault:

[0071] When the rate of change of brake pedal travel is ≤ a1, the vacuum degree is > d1 and continues for more than 3 seconds for the second preset time, or when the rate of change of brake pedal travel is ≤ a2 and the vacuum pump continues to work for more than 60 seconds for the third preset time, the vehicle controller determines that the vacuum booster system has entered a serious leakage fault.

[0072] Where d1 is the minimum vacuum level required by the vacuum pump operating system, and d1 > d2;

[0073] a2 is the threshold value for the rate of change of the second brake pedal travel. a2 is the minimum resolution of m times the brake pedal travel. The smaller the value, the higher the detection accuracy, but the greater the detection error. In this embodiment, a2 is 10 times the minimum resolution of the brake pedal travel.

[0074] At this time, the vehicle controller sends a serious leakage fault signal of the vacuum booster system to the instrument panel. At the same time, the maximum vehicle speed is limited to the first vehicle speed s, and the vacuum pump works for 5 seconds and stops for 5 seconds, working in an infinite cycle.

[0075] When the vacuum booster system experiences a severe leakage fault, the vehicle controller activates regenerative braking. The magnitude of the regenerative braking torque is as follows:

[0076] ;

[0077] The magnitude of the motor's regenerative compensation torque is proportional to the difference in braking vacuum and the product of the motor's regenerative compensation torque MAP, such as... Figure 4 As shown, when a serious malfunction occurs in the vacuum assist system, the vehicle controller obtains the brake pedal travel value and the current vehicle speed. It then performs brake torque compensation adjustment by looking up the table through the motor feedback compensation torque MAP (the initial adjustment is to obtain the maximum motor feedback compensation torque under the current vehicle speed and brake pedal position without vacuum assist). After that, the vehicle controller performs PID torque compensation adjustment again based on the difference ratio of the current vacuum degree. The smaller the vacuum degree difference ratio, the smaller the motor feedback compensation torque, and the less intervention in driving behavior. Under the premise of ensuring safety, it is closer to the driver's daily driving habits.

[0078] The motor feedback compensation adopts a dual adjustment method of vacuum level motor feedback compensation torque MAP lookup table and vacuum degree difference. When the brake pedal is pressed, the whole vehicle feedback compensation torque is initially adjusted by looking up the table according to the two-dimensional MAP of the current vehicle speed and brake pedal depth, and then a second torque PID adjustment is performed according to the vacuum degree difference ratio. This adjustment method is closer to the braking condition of the vehicle under normal conditions than the single lookup table braking compensation method.

[0079] In addition, in this embodiment, to more clearly illustrate the technical solution of this application, the vehicle controller can also determine whether the vehicle is in normal mode based on the vacuum degree change rate, brake pedal travel value change rate, vehicle speed, and vacuum degree signal. Specifically:

[0080] When the vehicle speed is less than the first vehicle speed s, and the vacuum degree is greater than or equal to d2, the vehicle controller controls the vacuum pump to start working. When the vacuum pump relay works for 15 seconds and the vacuum degree is less than or equal to d4, the vacuum pump stops working.

[0081] When the vehicle speed is greater than or equal to the first vehicle speed s and the vacuum degree is greater than or equal to d3, the vehicle controller controls the vacuum pump to start working. When the vacuum pump relay works for 15 seconds and the vacuum degree is less than or equal to d4, the vacuum pump stops working.

[0082] If the vehicle is in the above state, the vacuum booster system is considered to be in normal working condition.

[0083] The above description is only a preferred embodiment of the present invention. It should be noted that for those skilled in the art, several improvements can be made without departing from the principle of the present invention, and these improvements should also be considered within the scope of protection of the present invention.

Claims

1. A vacuum pump control method with fault detection and motor back- emf compensation braking, characterized by, The method comprises: acquiring signals of the vacuum degree sensor within a certain time and calculating the rate of change of the vacuum degree; acquiring the brake pedal stroke value and calculating the rate of change of the brake pedal stroke value; acquiring the real-time vehicle speed signal; the vehicle control unit divides the vacuum assist system into general leakage faults, sensor faults and serious leakage faults according to the above signals, wherein: general leakage faults: when the rate of change of the brake pedal stroke value is ≤a1 and the rate of change of the vacuum degree is ≤b1 and after a preset filtering time, it is determined that the vacuum assist system enters a general leakage fault; if the vacuum pump relay working time does not reach a first preset time and the vacuum degree does not reach a threshold value corresponding to the current vehicle speed, the vehicle control unit controls the vacuum pump to stop working; vacuum degree sensor fault: the vehicle control unit determines the short circuit or open circuit of the vacuum degree sensor according to the internal hard-wire circuit voltage value, and at the same time, when the vacuum degree is ≤d2 and the brake pedal stroke is greater than c and the pedal returns, the vacuum degree does not change or the rate of change is less than b2, it is determined that the vacuum degree sensor is faulty; serious leakage fault: when the rate of change of the brake pedal stroke is ≤a1 and the vacuum degree is >d1 and lasts for more than a second preset time, or the rate of change of the brake pedal stroke value is ≤a2 and the vacuum pump works continuously for more than a third preset time, it is determined that the vacuum assist system enters a serious leakage fault, at this time, the vehicle control unit limits the maximum vehicle speed to be less than a first speed, and controls the vacuum pump to work intermittently and circularly, and starts the motor feedback compensation braking, the size of the motor feedback compensation torque is proportional to the difference between the brake vacuum degree and the motor feedback compensation torque MAP product: ； wherein: the first speed is a critical value for determining that the vehicle is in a low-speed or high-speed driving state; a1 is a first preset brake pedal stroke rate threshold value; a2 is a second preset brake pedal stroke rate threshold value; c is the minimum pedal stroke value of the driver's intervention braking system; b1 is the maximum rate of change of the vacuum degree when the brake pedal rate is a1 under normal conditions; b2 is the minimum rate of change of the vacuum degree when the brake pedal stroke value is greater than c and the pedal returns under normal conditions; d1 is the minimum vacuum degree required by the vacuum pump assist system; d3 is the minimum threshold value of the vacuum degree sensor when the vehicle speed is greater than the first speed; d1>d3.

2. The vacuum pump control method with fault detection and motor back emf compensation braking of claim 1, wherein, The method further comprises: after it is determined that the vacuum assist system enters a general leakage fault, if the vehicle speed is less than the first speed and the vacuum degree is ≥d2, the vehicle control unit controls the vacuum pump to start working until the vacuum pump relay working time does not reach the first preset time and the vacuum degree is ≤d4, the vacuum pump stops working; if the vehicle speed is greater than the first speed and the vacuum degree is ≥d3, the vehicle control unit controls the vacuum pump to start working until the vacuum pump relay working time does not reach the first preset time and the vacuum degree is ≤d4, the vacuum pump stops working; wherein: d2 is the threshold value of the vacuum degree sensor when the vacuum pump is off, d4 is the threshold value of the vacuum pump when it is on, and d1>d2>d3>d4.

3. The vacuum pump control method with fault detection and motor back emf compensation braking of claim 1, wherein, The method further comprises: after it is determined that the vacuum assist system enters a general leakage fault, a vacuum degree sensor fault or a serious leakage fault, the vehicle control unit sends a fault signal to the instrument to prompt the corresponding fault information.

4. The vacuum pump control method with fault detection and motor back emf compensation braking of claim 1, wherein, The method further comprises: In a general leakage fault or vacuum degree sensor fault state, if the vacuum pump works for more than a first preset time and d4≤ vacuum degree≤d2, the vehicle controller controls the vacuum pump to stop working, and when the brake pedal stroke value positively increases, the vacuum pump working time is re-timed.

5. The vacuum pump control method with fault detection and motor back emf compensation braking of claim 1, wherein, The method further comprises: When the vehicle controller judges that the vacuum assist system enters a vacuum degree sensor fault, the vehicle controller controls the vacuum pump to work according to a brake signal, and after the brake signal stops, the vacuum pump continuously works for a preset time and then stops.

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