Automobile brake pressure control method

Abstract

The present invention provides a method for controlling the braking pressure of an automobile, comprising the following steps: Step 1: obtaining a target pressure value P of the vehicle's braking output; exp and the current brake chamber estimated pressure P est , calculate the pressure difference ΔP between the two; Step 2, determine the state that the actuator for pressure control is to enter according to ΔP, and the states include pressurization state, decompression state, pressure holding state, etc.; Step 3, obtain the new target pressure value P exp and the chamber pressure estimate P output by the pressure estimation model est The difference between the two values ​​is calculated to obtain an updated pressure differential ΔP. The obtained ΔP is used to determine whether to loop through step 2. In step 4, when ΔP ≤ a, the system enters a dynamic pressure-maintaining state. In step 5, after dynamic pressure-maintaining, the actual pressure feedback value output by the pressure sensor is collected and used to correct the pressure estimate. The corrected chamber pressure prediction value serves as the initial pressure estimate for the next control cycle. This control method solves problems such as low control accuracy and slow response speed.

Description

Technical Field

[0001] The present invention relates to the field of experimental simulation, and in particular to a method for controlling automobile brake pressure. Background Art

[0002] The electronically controlled brake system EBS (Electronically Controlled Brake System) is developed based on the ABS anti-lock braking system. Compared with conventional braking systems, commercial vehicle EBS uses electronically controlled air brakes, which can effectively improve the braking response speed and braking efficiency of commercial vehicles. At the same time, it can reduce the probability of danger during emergency braking and effectively ensure the safety of the driver. Based on EBS, a variety of system functions can also be expanded, such as vehicle stability control (ESC), adaptive cruise control (ACC), automatic emergency braking (AEB), etc. Among them, the accuracy of pressure control is an important guarantee for realizing EBS functions and other functions based on EBS.

[0003] In current commercial vehicle electronic braking systems (EBS), the axis module is generally used as the specific executive component of pressure control. The EBS controller calculates a reasonable target pressure signal based on information such as the braking stroke of the foot valve and the vehicle status. By receiving the actual air chamber pressure signal from the pressure sensor, it uses control methods such as PID and logical threshold values ​​to output drive instructions to control the opening and closing of the pressure and decompression solenoid valves integrated in the axis module, thereby achieving pressure control of the brake air chamber. Summary of the Invention

[0004] The present invention provides a method for controlling automobile brake pressure based on the existing technical problems.

[0005] In order to achieve the above object, the present invention adopts the following technical solutions:

[0006] A method for controlling automobile brake pressure comprises the following steps:

[0007] Step 1: Obtain the target pressure value P of the vehicle's brake output exp and the current brake chamber estimated pressure P est , calculate the pressure difference ΔP between the two;

[0008] Step 2: Determine the state that the actuator for pressure control will enter based on ΔP.

[0009] When ΔP>a, the executive component enters the pressurization control state, and the pressurization controller calculates the time t that the pressure and decompression solenoid valves need to open. ev , t av , use the pressure estimation model to estimate the output chamber pressure estimate P est ;

[0010] When ΔP<-a, the executive component enters the pressure reduction control state, and the pressure reduction controller calculates the time t that the pressure increase and pressure reduction solenoid valves need to open. ev , t av , use the pressure estimation model to estimate the output chamber pressure estimate P est ;

[0011] When |ΔP|≤a, the actuator is in the pressure maintaining state, and the pressure increasing and pressure reducing solenoid valves do not operate;

[0012] Step 3: Get the new target pressure value P exp and the chamber pressure estimate P output by the pressure estimation model est , calculate the difference between the two to obtain the updated pressure difference ΔP, and determine whether to loop through step 2 based on the obtained ΔP;

[0013] Step 4: When ΔP≤a, the estimated pressure is close to the target pressure, and the system enters the dynamic pressure holding state;

[0014] Step 5: After the dynamic pressure maintenance is completed, the actual pressure feedback value output by the pressure sensor is collected to correct the pressure estimation value; the corrected chamber pressure prediction value is used as the initial pressure estimation value of the next control cycle.

[0015] As a preferred embodiment, step 2 also includes that when ΔP≥c, c>a, the system enters a rapid pressurization process, during which only the pressurization solenoid valve is activated, and the pressurization controller calculates the opening time t of the pressurization solenoid valve using control methods such as PID and fuzzy control. ev , so that the air chamber pressure quickly approaches the target pressure value P exp ;

[0016] When ΔP≤-c, the system enters the rapid decompression process. During the rapid decompression process, only the pressure reducing solenoid valve is activated. The pressure reducing controller uses PID, fuzzy control and other control methods to calculate the opening time t of the pressurization solenoid valve. av , so that the air chamber pressure quickly approaches the target pressure value P exp ;

[0017] When a<|ΔP|<c, the system enters the pressure fine-tuning process. The fine-tuning of the air chamber pressure is achieved by opening the increasing and decreasing pressure solenoid valves at the same time. The opening time of the increasing and decreasing pressure solenoid valves is related to the current air chamber pressure. This method calibrates the optimal action time under different working conditions through experiments.

[0018] Preferably, during the rapid pressurization process, the rapid pressurization estimation module is used to estimate the pressure of the air chamber after the pressurization control; during the rapid decompression process, the rapid decompression estimation module is used to estimate the pressure of the air chamber after the decompression control;

[0019] The rapid pressurization estimation model is as follows:

[0020]

[0021] The rapid decompression estimation model is as follows:

[0022]

[0023] Where, P est_last is the estimated pressure of the gas chamber before pressure control, P est is the estimated pressure of the gas chamber after pressure control, C1 and C2 are constant calibration quantities, and P atm is the atmospheric pressure, and b is the critical pressure ratio.

[0024] Preferably, C1 and C2 are set to 0.012 and 0.016 respectively, and b is set to 0.528.

[0025] As a preferred method, the estimation model of the pressure fine-tuning process is:

[0026] When pressurized: P est =P est_last +A

[0027] When decompressing: P est =P est_last -A

[0028] P est is the estimated pressure of the gas chamber after pressure control, P est_last is the estimated pressure of the gas chamber before pressure control, and A is the single pressure adjustment value.

[0029] Preferably, A is 0.15 bar.

[0030] As a preference, in step 3, when |ΔP|≥a, the system needs to continue pressure control. At this time, the system enters step 2, performs pressure increase and pressure decrease control according to the size of ΔP, and calculates the total action time t of the pressure increase and pressure decrease solenoid valves in the current control cycle. sum ,t sum Only the opening time of the pressure increasing and reducing solenoid valves in the process of rapid pressure regulation is calculated, and two estimated pressures P are defined. est The process between feedback correction is a control cycle; when |ΔP|<a, the system enters the dynamic pressure holding state. The dynamic pressure holding state means that when the system enters the pressure holding state, the pressure holding time t hold It is dynamically adjusted in different control cycles, t hold By the current control cycle t sum Determine, the calculation formula is t hold =10·t sum ; Holding time is t min ≤t hold ≤t max .

[0031] As a preference, t min =30,t max =300.

[0032] As a preferred method, after the dynamic pressure holding is completed, the actual pressure feedback value output by the pressure sensor is collected to perform feedback correction on the pressure estimation value:

[0033] P est =h1·P act +h2·Pe st_last

[0034] Where h1 and h2 are correction coefficients, P est_last To correct the previous estimate of the chamber pressure, P est To correct the estimated value of the chamber pressure, P act The actual chamber pressure value output by the pressure sensor at the outlet of the actuator is the predicted value P est As the initial pressure estimation value of the next control cycle, the cyclic control of the air chamber pressure is achieved through this method.

[0035] As a preferred embodiment, the execution component is the shaft module, a is 0.1 bar, c is 0.3 bar; in step 1, the current brake chamber estimated pressure P in the initial state est The actual pressure of the current execution component.

[0036] This solution has the following beneficial effects:

[0037] This method uses the pressure estimation value of the model as the input of the pressure controller and performs control before the actual pressure changes, which improves the system response speed. It also adds a dynamic pressure holding process, waits for the system to enter a stable state, and uses the actual pressure value after stabilization to feedback and correct the pressure estimation value, thereby improving the accuracy of the pressure estimation value.

[0038] During pressure control, due to the significant lag between the opening and closing of the valve core, when the actual pressure approaches the target pressure, the air chamber pressure is prone to overshoot, typically requiring the next control cycle to correct the pressure, which increases the system's stabilization time. This method adds a control process in which the increasing and decreasing valves are simultaneously opened during pressure control, achieving fine-tuning of the air chamber pressure. This technical approach addresses the problems of low control accuracy, slow response speed, and large overshoot in existing control methods. BRIEF DESCRIPTION OF THE DRAWINGS

[0039] Figure 1 This is the system control flow chart.

[0040] Figure 2 This is the pressure control flow chart.

[0041] Figure 3 Pressure reduction control flow chart.

[0042] Figure 4 System installation diagram.

[0043] Figure 5 Schematic diagram of the actual control process. DETAILED DESCRIPTION

[0044] Example 1

[0045] A method for controlling automobile brake pressure comprises the following steps:

[0046] Step 1: Obtain the target pressure value P of the vehicle's brake output exp and the current brake chamber estimated pressure P est , calculate the pressure difference ΔP between the two; the target pressure value is obtained by combining the foot valve and other vehicle conditions; the pressure values ​​involved in this embodiment are all in bar;

[0047] Step 2: Determine the state that the actuator for pressure control will enter based on ΔP.

[0048] When ΔP>a, the executive component enters the pressurization control state, and the pressurization controller calculates the time t that the pressure and decompression solenoid valves need to open. ev , t av , use the pressure estimation model to estimate the output chamber pressure estimate P est The actuator in this embodiment is a shaft module in the prior art, which integrates a pressurizing and decompressing solenoid valve module. The time unit in this embodiment is milliseconds.

[0049] When ΔP<-a, the executive component enters the pressure reduction control state, and the pressure reduction controller calculates the time t that the pressure increase and pressure reduction solenoid valves need to open. ev , t av , use the pressure estimation model to estimate the output chamber pressure estimate P est ;

[0050] When |ΔP|≤a, the actuator is in the pressure maintaining state, and the pressure increasing and pressure reducing solenoid valves do not operate;

[0051] When the absolute value of ΔP is large, rapid pressurization and decompression should be performed. Therefore, in this scheme, pressurization and decompression are divided into rapid pressurization, rapid decompression, and fine-tuning pressurization and decompression processes.

[0052] That is, step 2 also includes when ΔP≥c, c>a, the system enters the rapid pressurization process, during which only the pressurization solenoid valve is activated, and the pressurization controller uses control methods such as PID and fuzzy control to calculate the opening time t of the pressurization solenoid valve. ev, so that the air chamber pressure quickly approaches the target pressure value P exp ;

[0053] When ΔP≤-c, the system enters the rapid decompression process. During the rapid decompression process, only the pressure reducing solenoid valve is activated. The pressure reducing controller uses PID, fuzzy control and other control methods to calculate the opening time t of the pressurization solenoid valve. av , so that the air chamber pressure quickly approaches the target pressure value P exp ;

[0054] When a<|ΔP|<c, the air chamber pressure is close to the target pressure. To avoid pressure overshoot, the system enters the pressure fine-tuning process. The fine-tuning of the air chamber pressure is achieved by opening the increasing and decreasing pressure solenoid valves at the same time. The opening time of the increasing and decreasing pressure solenoid valves is related to the current air chamber pressure. This method calibrates the optimal action time under different working conditions through experiments; see Appendix 2; see Appendix 2.

[0055] Table 1 Pressure Lookup Table Controller

[0056]

[0057] Table 2 Pressure reduction lookup table controller

[0058]

[0059] In this embodiment, the value of a is 0.1, and the value of c is 0.3. When the absolute value of the difference is greater than 0.3, the process of rapid pressurization and decompression is started.

[0060] During the rapid pressurization process, the rapid pressurization estimation module is used to estimate the pressure of the air chamber after pressurization control; during the rapid decompression process, the rapid decompression estimation module is used to estimate the pressure of the air chamber after decompression control;

[0061] The rapid pressurization estimation model is as follows:

[0062]

[0063] The rapid decompression estimation model is as follows:

[0064]

[0065] Where, P est_last is the estimated pressure of the gas chamber before pressure control, P est is the estimated pressure of the gas chamber after pressure control, C1 and C2 are constant calibration quantities, and P atm is the atmospheric pressure, b is the critical pressure ratio. Specifically, in this solution, C1 and C2 are set to 0.012 and 0.016 respectively, and b is set to 0.528.

[0066] Among them, since the pressure fine-tuning process is achieved by opening the pressure-increasing and pressure-reducing valves at the same time, the system has strong nonlinear characteristics and a complex model, which is not conducive to practical engineering applications. This method uses experimental calibration to calibrate the optimal opening time under different working conditions. Under this opening time, the pressure-increasing control can achieve the pressure gradient control of A, and the pressure-reducing control can achieve the pressure gradient control of -A. Therefore, the estimation model of the pressure fine-tuning estimation module is:

[0067] When pressurized: P est =P est_last +A

[0068] When decompressing: P est =P est_last -A

[0069] P est is the estimated pressure of the gas chamber after pressure control, P est_last is the estimated pressure of the gas chamber before pressure control, and A is the single pressure adjustment value. In this embodiment, A is 0.15.

[0070] Step 3: After completing the above adjustments based on the value of ΔP, obtain the new target pressure value P exp and the chamber pressure estimate P output by the pressure estimation model est , calculate the difference between the two to obtain the updated pressure difference ΔP, and determine whether to loop through step 2 based on the obtained ΔP;

[0071] Step 4: When |ΔP|≥0.1, the system needs to continue pressure control. At this time, the system enters step 2, performs pressure increase and pressure decrease control according to the size of ΔP, and calculates the total action time t of the pressure increase and pressure decrease solenoid valves in the current control cycle. sum ,t sum Only the opening time of the pressure increasing and reducing solenoid valves in the process of rapid pressure regulation is calculated. The pressure fine-tuning process is not included in the calculation range. The control cycle is defined as two estimated pressures P est The process between feedback corrections is a control cycle.

[0072] When ΔP≤a, the estimated pressure is close to the target pressure, and the system enters the dynamic pressure holding state; the dynamic pressure holding state means that when the system enters the pressure holding state, the pressure holding time t hold It is dynamically adjusted in different control cycles, t hold By the current control cycle t sum Determine, the calculation formula is t hold =10·t sum To avoid the influence of too long or too short holding time on the control effect, it is necessary to set upper and lower limits on the holding time. min ≤t hold ≤t max, the value used in this method is t min =30,t max =300.

[0073] Step 5: After the dynamic pressure maintenance is completed, the actual pressure feedback value output by the pressure sensor is collected to correct the pressure estimation value; the corrected chamber pressure prediction value is used as the initial pressure estimation value for the next control cycle. The correction model is:

[0074] P est =h1·P act +h2·P est_last

[0075] Where h1 and h2 are correction coefficients, P est_last To correct the previous estimate of the chamber pressure, P est To correct the estimated value of the chamber pressure, P act The actual chamber pressure value output by the pressure sensor at the outlet of the actuator is the predicted value P est As the initial pressure estimation value of the next control cycle, the cyclic control of the air chamber pressure is achieved through this method.

[0076] In this embodiment, the execution component is the shaft module. In step 1, the current brake chamber estimated pressure P in the initial state est The actual pressure of the current execution component.

[0077] This method uses the pressure estimation value of the model as the input of the pressure controller and performs control before the actual pressure changes, which improves the system response speed. It also adds a dynamic pressure holding process, waits for the system to enter a stable state, and uses the actual pressure value after stabilization to feedback and correct the pressure estimation value, thereby improving the accuracy of the pressure estimation value.

[0078] During pressure control, due to the significant lag between the opening and closing of the valve core, when the actual pressure approaches the target pressure, the air chamber pressure is prone to overshoot, typically requiring the next control cycle to correct the pressure, which increases the system's stabilization time. This method adds a control process in which the increasing and decreasing valves are simultaneously opened during pressure control, achieving fine-tuning of the air chamber pressure. This technical approach addresses the problems of low control accuracy, slow response speed, and large overshoot in existing control methods.

Claims

1. A method for controlling automobile brake pressure, characterized in that: The following steps are involved: Step 1: Obtain the target pressure value P of the vehicle's brake output exp and the current brake chamber estimated pressure P est , calculate the pressure difference ΔP between the two; Step 2: Determine the state that the actuator for pressure control will enter based on ΔP. When ΔP>a, the executive component enters the pressurization control state, and the pressurization controller calculates the time t that the pressure and decompression solenoid valves need to open. ev , t av , use the pressure estimation model to estimate the output chamber pressure estimate P est ; When ΔP<-a, the executive component enters the pressure reduction control state, and the pressure reduction controller calculates the time t that the pressure increase and pressure reduction solenoid valves need to open. ev , t av , use the pressure estimation model to estimate the output chamber pressure estimate P est ; When |ΔP|≤a, the actuator is in the pressure maintaining state, and the pressure increasing and pressure reducing solenoid valves do not operate; Step 3: Get the new target pressure value P exp and the chamber pressure estimate P output by the pressure estimation model est , calculate the difference between the two to obtain the updated pressure difference ΔP, and determine whether to loop through step 2 based on the obtained ΔP; Step 4: When ΔP≤a, the estimated pressure is close to the target pressure, and the system enters the dynamic pressure holding state; Step 5: After the dynamic pressure maintenance is completed, the actual pressure feedback value output by the pressure sensor is collected to correct the pressure estimation value; the corrected chamber pressure prediction value is used as the initial pressure estimation value of the next control cycle; In step 3, when |ΔP|≥a, the system needs to continue pressure control. At this time, the system enters step 2, performs pressure increase and pressure decrease control according to the size of ΔP, and calculates the total action time t of the pressure increase and pressure decrease solenoid valves in the current control cycle. sum ,t sum Only the opening time of the pressure increasing and reducing solenoid valves in the process of rapid pressure regulation is calculated, and two estimated pressures P are defined. est The process between feedback correction is a control cycle; when |ΔP|<a, the system enters the dynamic pressure holding state. The dynamic pressure holding state means that when the system enters the pressure holding state, the pressure holding time t hold It is dynamically adjusted in different control cycles, t hold By the current control cycle t sum Determine, the calculation formula is t hold =10·t sum ; Holding time is t min ≤t hold ≤t max ; After dynamic pressure maintenance is completed, the actual pressure feedback value output by the pressure sensor is collected to correct the pressure estimation value: P est =h1·P act +h2·P est_last Where h1 and h2 are correction coefficients, P est_last To correct the previous estimate of the chamber pressure, P est To correct the estimated value of the chamber pressure, P act The actual chamber pressure value output by the pressure sensor at the outlet of the actuator is the predicted value P est As the initial pressure estimation value of the next control cycle, the cyclic control of the air chamber pressure is achieved through this method.

2. The automobile brake pressure control method according to claim 1, characterized in that: Step 2 also includes that when ΔP≥c, c>a, the system enters the rapid pressurization process, during which only the pressurization solenoid valve is activated, and the pressurization controller uses control methods such as PID and fuzzy control to calculate the opening time t of the pressurization solenoid valve. ev , so that the air chamber pressure quickly approaches the target pressure value P exp ; When ΔP≤-c, the system enters the rapid decompression process. During the rapid decompression process, only the pressure reducing solenoid valve is activated. The pressure reducing controller uses PID, fuzzy control and other control methods to calculate the opening time t of the pressurization solenoid valve. av , so that the air chamber pressure quickly approaches the target pressure value P exp ; When a<|ΔP|<c, the system enters the pressure fine-tuning process. The fine-tuning of the air chamber pressure is achieved by opening the increasing and decreasing pressure solenoid valves at the same time. The opening time of the increasing and decreasing pressure solenoid valves is related to the current air chamber pressure. This method calibrates the optimal action time under different working conditions through experiments.

3. The automobile brake pressure control method according to claim 2, characterized in that: During the rapid pressurization process, the rapid pressurization estimation module is used to estimate the pressure of the air chamber after pressurization control; during the rapid decompression process, the rapid decompression estimation module is used to estimate the pressure of the air chamber after decompression control; The rapid pressurization estimation model is as follows: The rapid decompression estimation model is as follows: Where, P est_last is the estimated pressure of the gas chamber before pressure control, P est is the estimated pressure of the gas chamber after pressure control, C1 and C2 are constant calibration quantities, and b is the critical pressure ratio.

4. The automobile brake pressure control method according to claim 3, characterized in that: The values ​​of C1 and C2 are 0.012 and 0.016 respectively, and the value of b is 0.

528.

5. The automobile brake pressure control method according to claim 2, characterized in that: The estimation model of the pressure fine-tuning process is: When pressurized: P est =P est_last +A When decompressing: P est =p est_last -A P est is the estimated pressure of the gas chamber after pressure control, P est_last is the estimated pressure of the gas chamber before pressure control, and A is the single pressure adjustment value.

6. The automobile brake pressure control method according to claim 2, characterized in that: A is 0.15 bar.

7. The automobile brake pressure control method according to claim 4, characterized in that: t min =30,t max =300。 8. The automobile brake pressure control method according to claim 2, characterized in that: The actuator is the shaft module, a is 0.1 bar, c is 0.3 bar; in step 1, the current brake chamber estimated pressure P in the initial state est The actual pressure of the current execution component.

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