CN118560442A - Pressure control system and method for electronic stability control of vehicle body - Google Patents

Abstract

The invention relates to the technical field of pressure control of electronic stability control of automobile bodies, in particular to a pressure control system and a method for electronic stability control of automobile bodies, wherein the pressure control method comprises a system pressure control method, a wheel cylinder pressure control method, a motor pump load calculation and control method and a motor rotating speed control method; and the pressure control of the electronic stable control of the vehicle body is comprehensively realized by mutually matching the system pressure control method, the wheel cylinder pressure control method, the motor pump load calculation and control method and the motor rotating speed control method. The invention not only can realize the regulation and control when the brake fluid is insufficient, but also can realize the regulation and control of system pressure, wheel cylinder pressure, motor rotation speed and motor pump load calculation and control, and can comprehensively and fully realize the pressure control of the electronic stable control of the automobile body, and has small calculated amount, strong engineering practicability and strong robustness.

Description

Pressure control system and method for vehicle body electronic stability control

Technical Field

The present invention relates to the technical field of pressure control for electronic stability control of automobile bodies, and in particular to a pressure control system and method for electronic stability control of automobile bodies.

Background Art

The main task of the pressure control system and method of the body electronic stability control is to execute the upper-level functions of the body electronic stability control including the wheel cylinder fluid pressure target control of the whole vehicle dynamic control functions such as ABS/EBD/TCS/VDC/auxiliary function modules.

Patent document (CN117584913A) discloses a wheel cylinder pressure control method for an integrated brake-by-wire system, which includes: designing a servo motor, transmission mechanism and hydraulic system model for an integrated brake-by-wire system; using the servo cylinder fluid pressure-piston position characteristics to design a motor-solenoid valve coordinated fluid replenishment mechanism that can dynamically adjust the underlying pressure regulator; designing a servo cylinder pressure regulator including a hydraulic system variable stiffness feedforward pressure loop, a robust sliding mode position loop and a motor current loop; designing a wheel cylinder pressure regulator based on the wheel cylinder inlet/outlet valve increase/depressurization characteristics to achieve wheel cylinder pressure regulation. This patent document solves the problem of insufficient brake fluid when the integrated brake-by-wire system is performing wheel cylinder pressure regulation due to sudden changes in hydraulic system stiffness and the loss of brake fluid in the hydraulic circuit along with the wheel cylinder pressure regulation. However, this patent document only considers the regulation problem when the brake fluid is insufficient, and has poor engineering practicality and low robustness.

Therefore, the present invention provides a pressure control system and method for vehicle body electronic stability control to solve the above problems.

Summary of the invention

In view of the above situation, in order to overcome the defects of the prior art, the present invention provides a pressure control system and method for vehicle body electronic stability control, so as to solve the problem that the above patent document only considers the regulation when the brake fluid is insufficient, has poor engineering practicality and weak robustness.

In order to achieve the above-mentioned purpose, the technical solution adopted by the present invention is a pressure control system and method for vehicle body electronic stability control. In a first aspect, the pressure control method includes a system pressure control method, a wheel cylinder pressure control method, a motor pump load calculation and control method and a motor speed control method; according to the system pressure control method, the wheel cylinder pressure control method, the motor pump load calculation and control method and the motor speed control method, the pressure control of the vehicle body electronic stability control is comprehensively realized; wherein, the system pressure control method includes an external control target arbitration program, a system pressure control program and a system model pressure estimation program, and the external control target arbitration program includes the following steps:

Step S1: Arbitrate the braking requests of the driver, ABS module and auxiliary function module to determine the target wheel cylinder pressure and the source of the braking request actually responded to, wherein the braking request of the ABS module is the first priority, and the braking request of the auxiliary function module is the second priority. When the braking request value of the auxiliary function module is less than the braking request value of the driver, respond to the braking request of the driver; when there is no braking request from the ABS and auxiliary function modules, respond to the braking request of the driver.

Step S2: Arbitrate the braking requests of the driver, ABS module and auxiliary function module to determine the target system pressure and whether to actively build pressure. When determining the target system pressure, the preset system pressure corresponding to the braking request of TCS/VDC has the first priority. When the TCS/VDC active pressure building request flag is established, the maximum value of the target wheel cylinder pressure and the master cylinder pressure of the ABS module is determined as the target system pressure; the preset system pressure corresponding to the braking request of the auxiliary function module has the second priority. When the TCS/VDC active pressure building request flag is not established, the preset system pressure corresponding to the braking request of the auxiliary function module is the target system pressure and is not greater than the master cylinder pressure; the preset system pressure corresponding to the braking request of the driver has the third priority.

The system pressure control program determines the actual flow into the master cylinder through the pressure limiting valve according to the flow pumped into the pipeline by the motor pump and the flow entering the wheel cylinder through the boost valve, and determines the control current of the pressure limiting valve according to the system target pressure, and controls the system pressure with the control current. The system model pressure estimation program determines the flow into the system pressure pipeline and the wheel cylinder pressure pipeline according to the flow of the motor pump and the flow of the pressure limiting valve, and determines the system pressure according to the system characteristics.

Preferably, the wheel cylinder pressure control method includes a valve control strategy design program, a pressure reducing valve control program and a pressure increasing valve control program; the valve control strategy design program includes controlling the valve to increase pressure when the target wheel cylinder pressure is greater than the wheel cylinder model pressure, and controlling the valve to reduce pressure when the target wheel cylinder pressure is less than the wheel cylinder model pressure; the pressure reducing valve control program includes calculating the driving control time according to the accumulator pressure and the target wheel cylinder pressure, and the control time T _AV calculation formula is:

Where p _Model is the wheel cylinder model pressure, p _Acc is the accumulator pressure, p _Grad is the pressure reduction rate of the pressure reducing valve in the current cycle, T _Response is the response time, and the calculation formula of p _Grad is:

p _Grad = c _Wheel * q _AV ,

Where c _Wheel is the velocity coefficient, C _d is the flow coefficient, A is the valve hole area of the pressure reducing valve, ρ is the brake fluid density, and q _AV is the pressure reducing flow rate; the calculation formula of T _Response is:

T _Response =T _OpenResponse -T _{CloseResponse} ,

Among them, T _OpenResponse is the open response time, T _{CloseResponse} is the close response time, and the calculation formula of T _OpenResponse is:

T _OpenResponse ＝c _open +k _OpenU *U _vr +k _OpenP *p _Model +k _OpenUP *U _vr *p _Model ,

Among them, c _open is the opening response coefficient, k _OpenU is the voltage response coefficient, U _vr is the pressure reducing valve driving voltage, k _OpenP is the model response coefficient, p _Model is the wheel cylinder model pressure, and k _OpenUP is the fusion response coefficient; the calculation formula of T _{CloseResponse} is:

T _{CloseResponse} ＝c _Close +k _CloseP *p _Tgt ,

Wherein, c _Close is the closing response coefficient, k _CloseP is the wheel cylinder pressure coefficient, and p _Tgt is the wheel cylinder pressure. The pressure reducing valve control program also includes calculating the pressure reducing amount p _DecAV and the average flow q _AVMean according to the actual control time and actual pressure reducing rate of the pressure reducing valve in the current cycle. The calculation formulas of the pressure reducing amount p _DecAV and the average flow q _AVMean are:

p _DecAV = p _Grad *min (0.005, T _AV ),

Among them, min() is the minimum function, p _Grad is the pressure reducing rate of the pressure reducing valve in the current cycle, and q _AV is the pressure reducing flow rate; the boost valve control program calculates the target flow rate through the boost valve according to the target wheel cylinder pressure and the wheel cylinder model pressure, and calculates the control current of the boost valve according to the actual pressure difference of the boost valve and the flow characteristics of the boost valve, and controls the boost valve with the control current of the boost valve.

Preferably, the boost valve control program includes six modes: Open, Close, DP, Pulse, FastPulse and FixPulse; the Open mode is when the boost valve is open and the control current is 0; the Close mode is when the boost valve is closed and the control current is 1.5A; the DP mode includes converting the target pressure into the target flow, and the conversion formula is:

Wherein, q _Tgt is the target flow rate, p _Tgt is the target pressure, k is the response time value, p _Model is the wheel cylinder model pressure, c _Wheel is the rate coefficient, and the DP mode also includes a comfort mode, and the target flow rate of the comfort mode is 8cc/s. The control current I _EV of the DP mode boost valve is:

ΔP _EV =p _System -p _Model ,

I _EV =LookupTable (q _Tgt ,ΔP _EV ),

Wherein, LookTable() is a lookup function, ΔP _EV is the pressure difference, p _System is the system pressure, and p _Model is the wheel cylinder model pressure. Pulse mode and FastPulse mode periodically perform discrete sampling of p _Tgt , and calculate the boost valve opening time T _EV based on the discretely sampled p _Tgt . The T _EV calculation formula is:

Wherein, p _GradEV is the pressure change rate, c _wheel is the rate coefficient, C _d is the flow coefficient, A is the boost valve orifice area, ρ is the brake fluid density, p _TgtSample is the discrete sampled pressure, and p _Model is the wheel cylinder model pressure. The FixPulse mode opens the boost valve at a fixed time period in a fixed cycle. The boost valve control program also includes first-order filtering of the target control current of the boost valve, and using the filtering result as the control current; searching the current flow q _EV of the boost valve according to the control current I _EV and the pressure difference ΔP _EV of the boost valve, and the search formula for the current flow q _EV is: q _EV = LookupTable(I _EV ,ΔP _EV ); and estimating the pressure change of the current control cycle according to the wheel cylinder characteristics, and the calculation formula for the pressure change p _IncEV is:

p _IncEV =q _EvEst *c _Wheel *0.005, q _EvEst is the flow rate in the current control cycle.

In a second aspect, the present invention also provides a pressure control system for vehicle body electronic stability control, comprising: a system pressure control module, a wheel cylinder pressure control module, a motor control module, an ABS module and an auxiliary function module. The system pressure control module arbitrates the braking requests of the driver, the ABS module and the auxiliary function module to obtain the target system pressure and the target wheel cylinder pressure, and when the auxiliary function module is working, controls the motor pump to pump the accumulator or the master cylinder brake fluid into the system pressure pipeline, and controls the opening of the pressure limiting valve to adjust the system pressure. The wheel cylinder pressure control module estimates the wheel cylinder model pressure according to the relationship between the system pressure, the boost valve control current and the pressure reducing valve control time, and analyzes the target wheel cylinder pressure to obtain the target boost valve control current and the target pressure reducing valve control time. The motor control module includes a motor target speed calculation module, a motor pump load calculation and control module and a motor speed control module. The motor target speed calculation module analyzes the accumulator fluid volume of the accumulator and the flow demand of the active pressure building to obtain the motor target speed. The motor pump load calculation and control module uses the accumulator model to process the liquid volume and accumulator characteristics flowing into the accumulator through the pressure reducing valve to obtain the accumulator pressure, and uses the pump model to analyze the motor speed and the pressure difference at both ends of the pump to obtain the load torque applied by the pump to the motor. During active supercharging, when the accumulator liquid is emptied, the suction valve is controlled to open to allow the liquid to flow into the accumulator; the motor speed control module analyzes the target motor speed and motor load to control the motor speed.

The beneficial effects of the present invention are:

1. The present invention realizes the pressure control of the electronic stability control of the vehicle body by cooperating with the system pressure control method, the wheel cylinder pressure control method, the motor pump load calculation and control method and the motor speed control method. The present invention can not only realize the regulation when the brake fluid is insufficient, but also realize the system pressure regulation, wheel cylinder pressure regulation, motor speed regulation and motor pump load calculation and control, and can fully and comprehensively realize the pressure control of the electronic stability control of the vehicle body, and has small calculation amount, strong engineering practice and strong robustness.

2. The system pressure control method of the present invention adopts an external control target arbitration procedure to arbitrate the braking requests of the driver, ABS module and auxiliary function module to determine the target wheel cylinder pressure and the source of the braking request actually responded. Among the braking request sources, the braking request of the ABS module is the first priority, and the braking request of the auxiliary function module is the second priority. When the braking request value of the auxiliary function module is less than the braking request value of the driver, the driver's braking request is responded to. When there is no braking request from the ABS and auxiliary function modules, the driver's braking request is responded to. The braking requests of the driver, ABS module and auxiliary function module are arbitrated to determine the target system pressure and whether to actively build pressure. When determining the target system pressure, the preset system pressure corresponding to the braking request of TCS/VDC is the first priority. When the TCS/VDC active pressure building request flag is established, the maximum value of the target wheel cylinder pressure and the master cylinder pressure of the ABS module is determined as the target system pressure; the preset system pressure corresponding to the braking request of the auxiliary function module is the second priority. When the TCS/VDC active pressure building request flag is not established, the preset system pressure corresponding to the braking request of the auxiliary function module is the target system pressure and is not greater than the master cylinder pressure; the preset system pressure corresponding to the driver's braking request is the third priority. The system pressure control program determines the actual flow into the master cylinder through the pressure limiting valve according to the flow of the motor pump pumping into the pipeline and the flow entering the wheel cylinder through the booster valve, and determines the control current of the pressure limiting valve according to the system target pressure, and controls the system pressure with the control current. The system model pressure estimation program determines the flow into the system pressure pipeline and the wheel cylinder pressure pipeline according to the flow of the motor pump and the flow of the pressure limiting valve, and determines the system pressure according to the system characteristics. The system pressure control method of the present invention realizes the control of the system pressure through the external control target arbitration program, the system pressure control program and the system model pressure estimation program, and has strong engineering practicability and robustness. The system pressure control program of the present invention determines the control current according to the difference between the actual flow of the pressure limiting valve, the target circuit pressure and the master cylinder pressure, and has small calculation amount and strong engineering practicability.

3. The wheel cylinder pressure control method of the present invention adopts valve control strategy design program, pressure reducing valve control program and boosting valve control program to comprehensively control wheel cylinder pressure, with small calculation amount and strong engineering practice. Among them, the valve control strategy design program includes controlling the valve to increase pressure when the target wheel cylinder pressure is greater than the wheel cylinder model pressure, and controlling the valve to reduce pressure when the target wheel cylinder pressure is less than the wheel cylinder model pressure. The pressure reducing valve control program calculates the control time of the drive according to the accumulator pressure and the target wheel cylinder pressure, and calculates the pressure reduction amount and the average flow rate according to the actual control time and actual pressure reduction rate of the pressure reducing valve in the current cycle. The boosting valve control program calculates the target flow through the boosting valve according to the target wheel cylinder pressure and the wheel cylinder model pressure, and calculates the control current of the boosting valve according to the actual pressure difference of the boosting valve and the flow characteristics of the boosting valve, and controls the boosting valve with the control current of the boosting valve, and the boosting valve control program uses six modes to control the boosting valve. The wheel cylinder pressure control method of the present invention adopts the above-mentioned program to comprehensively realize the wheel cylinder pressure control, and the calculation amount of each formula is small and the engineering practice is strong.

4. The motor pump load calculation and control method of the present invention adopts the accumulator model, pump model, and suction valve control method to comprehensively realize the calculation of the motor pump load and the control of the motor pump. Among them, the accumulator model calculates the liquid flow and accumulator pressure out of the accumulator according to the liquid flow entering the accumulator, the pump flow, the opening and closing state of the suction valve, and the master cylinder pressure; judges whether the accumulator is emptied according to the opening and closing state of the suction valve; calculates the flow into the accumulator according to the pressure reducing valve model; and integrates the liquid flow into and out of the accumulator over time to obtain the actual liquid storage in the accumulator. The pump model calculates the pump flow and the pressure difference at both ends of the pump according to the master cylinder pressure, motor speed, the opening and closing state of the suction valve, the accumulator liquid volume, and the accumulator pressure; determines the pressure at both ends of the pump according to the opening and closing state of the suction valve. When the suction valve is closed, the pressure at both ends of the pump is the system pressure and the accumulator pressure respectively; when the H suction valve is opened, the accumulator is in an empty state, and the pressure at both ends of the pump is the system pressure and the master cylinder pressure respectively; according to the pressure difference at both ends of the pump and the size characteristics of the plunger pump, the load torque of the motor is calculated. The suction valve control method uses the suction valve permission opening strategy, the suction valve opening request strategy and the suction valve control strategy to control the suction valve. The motor pump load calculation and control method of the present invention adopts the above-mentioned method to comprehensively realize the calculation of the motor pump load and the control of the motor pump, with small calculation amount and strong engineering practice.

5. The motor speed control method of the present invention adopts a variable conversion unit, a motor model unit, a motor speed control unit and a motor back-EMF sampling request unit to comprehensively realize the control of the motor speed, with small calculation amount and strong engineering practicability.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a schematic structural diagram of a pressure control method for vehicle body electronic stability control according to the present invention.

FIG. 2 is a schematic structural diagram of the valve control strategy design program of the present invention.

FIG. 3 is a schematic structural diagram of the pressure reducing valve control program of the present invention.

FIG. 4 is a schematic structural diagram of the boost valve control program of the present invention.

FIG. 5 is a schematic structural diagram of a pressure control system for vehicle body electronic stability control according to the present invention.

FIG. 6 is a diagram showing the system pressure control module architecture of the present invention.

FIG. 7 is a diagram showing the architecture of a wheel cylinder pressure control module according to the present invention.

DETAILED DESCRIPTION

The embodiments of the present invention will be described in detail below with reference to Figures 1 to 7. Those skilled in the art should understand that these embodiments are only used to explain the technical principles of the present invention and are not intended to limit the protection scope of the present invention.

In one embodiment of the present invention, as shown in FIG1 , the present invention provides a pressure control method for vehicle body electronic stability control, including a system pressure control method, a wheel cylinder pressure control method, a motor pump load calculation and control method, and a motor speed control method; according to the system pressure control method, the wheel cylinder pressure control method, the motor pump load calculation and control method, and the motor speed control method, the pressure control of the vehicle body electronic stability control is comprehensively implemented. The system pressure control method includes an external control target arbitration program, a system pressure control program, and a system model pressure estimation program, and the external control target arbitration program includes the following steps:

Step S1: Arbitrate the braking requests of the driver, ABS module and auxiliary function module to determine the target wheel cylinder pressure and the source of the braking request actually responded to, wherein the braking request of the ABS module is the first priority, and the braking request of the auxiliary function module is the second priority. When the braking request value of the auxiliary function module is less than the braking request value of the driver, respond to the braking request of the driver; when there is no braking request from the ABS and auxiliary function modules, respond to the braking request of the driver.

Step S2: Arbitrate the braking requests of the driver, ABS module and auxiliary function module to determine the target system pressure and whether to actively build pressure. When determining the target system pressure, the preset system pressure corresponding to the braking request of TCS/VDC has the first priority. When the TCS/VDC active pressure building request flag is established, the maximum value of the target wheel cylinder pressure and the master cylinder pressure of the ABS module is determined as the target system pressure; the preset system pressure corresponding to the braking request of the auxiliary function module has the second priority. When the TCS/VDC active pressure building request flag is not established, the preset system pressure corresponding to the braking request of the auxiliary function module is the target system pressure and is not greater than the master cylinder pressure; the preset system pressure corresponding to the braking request of the driver has the third priority.

The system pressure control program determines the actual flow into the master cylinder through the pressure limiting valve according to the flow of the motor pump pumping into the pipeline and the flow into the wheel cylinder through the boost valve, and determines the control current of the pressure limiting valve according to the system target pressure, and controls the system pressure with the control current. The system model pressure estimation program determines the flow into the system pressure pipeline and the wheel cylinder pressure pipeline according to the flow of the motor pump and the flow of the pressure limiting valve, and determines the system pressure according to the system characteristics.

In this embodiment, the present invention realizes the pressure control of the electronic stability control of the vehicle body in a comprehensive manner according to the system pressure control method, the wheel cylinder pressure control method, the motor pump load calculation and control method and the motor speed control method. The present invention can not only realize the regulation when the brake fluid is insufficient, but also realize the system pressure regulation, wheel cylinder pressure regulation, motor speed regulation and motor pump load calculation and control, and can fully and comprehensively realize the pressure control of the electronic stability control of the automobile body, and has small calculation amount, strong engineering practice and strong robustness. The system feature is the PV characteristic of the system pressure pipeline. And the external control target arbitration procedure of the present invention mainly processes the master cylinder brake fluid pressure from the driver, the wheel cylinder brake target pressure from the ABS/EBD function in the electronic stability control of the vehicle body, the active pressure building request from the TCS/VDC function in the electronic stability control of the vehicle body, and the wheel cylinder brake pressure target from other value-added functions (VAF). Compare the effective control targets together, and take the maximum value as the system pressure control target and the wheel cylinder pressure control target. And by default, the target system pressure responds to the driver's braking request. The external control target arbitration procedure of the present invention uses a priority method to determine the source of the braking request, avoiding conflicts in source determination.

In one embodiment of the present invention, the system model pressure estimation procedure includes: determining the system stiffness. When the left wheel cylinder and the right wheel cylinder are connected through a pipeline, the system stiffness calculation formula is:

Where c _cir is the system stiffness, c _L is the left wheel cylinder stiffness, and c _R is the left wheel cylinder stiffness; when the target control fluid pressures of the left wheel cylinder and the right wheel cylinder are not equal, the system stiffness is the maximum value of the left wheel cylinder stiffness and the right wheel cylinder stiffness. When the pressure limiting valve is closed, the system pressure change rate calculation formula is:

d _pSystem = q _Rfp * c _cir ,

Where _dpSystem is the rate of change of the system pressure, _qRfp is the pump flow rate, and _dpSystem is integrated to obtain the system pressure. When the master cylinder pressure is greater than or equal to the left wheel cylinder model pressure and the right wheel cylinder model pressure, the master cylinder pressure is the system pressure. When the pressure limiting valve is actively increasing pressure, the system pressure is the maximum value of the left wheel cylinder model pressure and the right wheel cylinder model pressure. When the pressure limiting valve is actively reducing pressure, the system pressure converges to the master cylinder pressure over time.

In this embodiment, the actual system pressure value is obtained by estimation. First, the net flow rate of the system pressure pipeline and the wheel cylinder pressure pipeline can be calculated based on the flow rate of the motor pump and the flow rate of the pressure limiting valve; then, the system pressure change rate can be calculated in combination with the PV characteristics of the system pipeline, and the actual system pressure can be calculated by integration, which has a small amount of calculation and strong engineering practice.

In one embodiment of the present invention, the system pressure control program determines the control current according to the actual flow of the pressure limiting valve, the difference between the target circuit pressure and the master cylinder pressure. The actual flow q _USV is calculated by the formula:

q _USV = q _Rfp - q _L - q _R ,

Among them, q _L is the actual flow of the left wheel cylinder, q _R is the actual flow of the right wheel cylinder; the control current i _USV is obtained as follows:

i _USV = LookTable (q _USV ,pTgt _cir -pMC),

Among them, LookTable() is the lookup function, pTgt _cir is the target circuit pressure, and pMC is the master cylinder pressure.

In this embodiment, the present invention mainly realizes system pressure control by controlling the current of the pressure limiting valve and the speed of the pump motor. According to the electromagnetic valve characteristics of the pressure limiting valve, its flow rate is fixed under certain control current and pressure difference. Therefore, the control current can be calculated according to the actual flow rate of the pressure limiting valve and the difference between the target circuit pressure and the actual master cylinder pressure, with small calculation amount and strong engineering practice.

In one embodiment of the present invention, the wheel cylinder pressure control method includes a valve control strategy design program, a pressure reducing valve control program and a pressure increasing valve control program. The valve control strategy design program includes controlling the valve to increase pressure when the target wheel cylinder pressure is greater than the wheel cylinder model pressure, and controlling the valve to reduce pressure when the target wheel cylinder pressure is less than the wheel cylinder model pressure. The pressure reducing valve control program includes calculating the driving control time according to the accumulator pressure and the target wheel cylinder pressure, and the control time T _AV calculation formula is:

Where p _Model is the wheel cylinder model pressure, p _Acc is the accumulator pressure, p _Grad is the pressure reduction rate of the pressure reducing valve in the current cycle, and T _Response is the response time. The calculation formula of p _Grad is:

p _Grad = c _Wheel * q _AV ,

Where c _Wheel is the velocity coefficient, C _d is the flow coefficient, A is the valve hole area of the pressure reducing valve, ρ is the brake fluid density, and q _AV is the pressure reducing flow. The calculation formula of T _Response is:

T _Response =T _OpenResponse -T _{CloseResponse} ,

Where, T _OpenResponse is the open response time, and T _{CloseResponse} is the close response time. The calculation formula of T _OpenResponse is:

T _OpenResponse ＝c _open +k _OpenU *U _vr +k _OpenP *p _Model +k _OpenUP *U _vr *p _Model ,

Among them, c _open is the opening response coefficient, k _OpenU is the voltage response coefficient, U _vr is the pressure reducing valve driving voltage, k _OpenP is the model response coefficient, p _Model is the wheel cylinder model pressure, and k _OpenUP is the fusion response coefficient. The calculation formula of _{T CloseResponse} is:

T _{CloseResponse} ＝c _Close +k _CloseP *p _Tgt ,

Wherein, c _Close is the closing response coefficient, k _CloseP is the wheel cylinder pressure coefficient, and p _Tgt is the wheel cylinder pressure.

The pressure reducing valve control program also includes calculating the pressure reducing amount p _DecAV and the average flow q _AVMean according to the actual control time and the actual pressure reducing rate of the pressure reducing valve in the current cycle. The calculation formulas of the pressure reducing amount p _DecAV and the average flow q _AVMean are:

p _DecAV = p _Grad *min (0.005, T _AV ),

Wherein, min() is the minimum function, p _Grad is the pressure reducing rate of the pressure reducing valve in the current cycle, and q _AV is the pressure reducing flow rate. The boost valve control program calculates the target flow rate through the boost valve according to the target wheel cylinder pressure and the wheel cylinder model pressure, and calculates the control current of the boost valve according to the actual pressure difference of the boost valve and the flow characteristics of the boost valve, and controls the boost valve with the control current of the boost valve.

In this embodiment, as shown in FIG2 , the valve control strategy design program analyzes the target pressure of the left and right wheel cylinders of the current circuit, the wheel cylinder model pressure, the valve control strategy of the ABS and the driving voltage of the pressure reducing valve, and outputs the boost valve control mode, the result of whether the wheel cylinder is allowed to be boosted, the result of whether the wheel cylinder is allowed to be depressurized, and the pressure reducing valve control mode. The valve control strategy design program determines whether to perform a boost operation or a depressurization operation at this time according to the wheel cylinder pressure control target and the actual wheel cylinder model pressure, and then determines whether the boost valve and the pressure reducing valve are working, and at the same time, according to the valve control strategy, determines the control mode of the boost valve and the pressure reducing valve. As shown in FIG3 , the pressure reducing valve control program analyzes the pressure difference between the two ends of the pressure reducing valve, the driving voltage of the pressure reducing valve, the wheel cylinder stiffness/target wheel cylinder pressure/actual wheel cylinder pressure, whether the pressure reducing is allowed/the pressure reducing valve control mode, and outputs the driving time of the pressure reducing valve, the average flow through the pressure reducing valve in the current cycle, and the wheel cylinder pressure change through the pressure reducing valve in the current cycle. Compared with the simple opening and closing pressure reducing valve, this embodiment improves the control of the pressure reducing valve, thereby improving the pressure control of the electronic stability control of the vehicle body.

In one embodiment of the present invention, the boost valve control program includes six modes: Open, Close, DP, Pulse, FastPulse and FixPulse. The Open mode is when the boost valve is open and the control current is 0; the Close mode is when the boost valve is closed and the control current is 1.5A; the DP mode includes converting the target pressure into the target flow to achieve linear control of the wheel cylinder pressure, and the conversion formula for converting the target pressure into the target flow is:

Among them, q _Tgt is the target flow, p _Tgt is the target pressure, k is the response time value, which is used to adjust the response speed of the boost valve, generally k=2, which represents the response time of the boost valve, p _Model is the wheel cylinder model pressure, c _Wheel is the rate coefficient, and the DP mode includes a comfort mode. The target flow of the comfort mode is 8cc/s, which ensures that the wheel cylinder pressure changes smoothly and improves comfort. When the actual pressure difference and the target flow are given, the control current of the solenoid valve can be determined by the table lookup method. The control current I _EV of the DP mode boost valve is:

ΔP _EV =p _System -p _Model ,

I _EV =LookupTable (q _Tgt ,ΔP _EV ),

Wherein, LookTable() is the lookup function, ΔP _EV is the pressure difference, p _System is the system pressure, and p _Model is the wheel cylinder model pressure. Pulse mode and FastPulse mode periodically perform discrete sampling of p _Tgt , and periodically perform discrete sampling of p _Tgt at a certain period (30ms for Pulse mode and 20ms for FastPulse mode). The boost valve controls the pressure by switch control, and calculates the boost valve opening time T _EV based on the discretely sampled p _Tgt . The T _EV calculation formula is:

Where p _GradEV is the pressure change rate, c _wheel is the rate coefficient, C _d is the flow coefficient, A is the boost valve orifice area, ρ is the brake fluid density, p _TgtSample is the discrete sample pressure, and p _Model is the wheel cylinder model pressure. The FixPulse mode opens the boost valve at a fixed time period in a fixed cycle, that is, regardless of the change of p _Tgt , the boost valve is opened at a fixed time in a fixed cycle (33ms) and each cycle. The boost valve control program also includes performing a first-order filtering on the target control current of the boost valve, using the filtering result as the estimated actual boost valve control current; searching for the current flow rate q _EV of the boost valve according to the control current I _EV and the boost valve pressure difference ΔP _EV , and the current flow rate q _EV search formula is: q _EV = LookupTable(I _EV ,ΔP _EV ); and estimating the pressure change in the current control cycle according to the wheel cylinder characteristics, and the pressure change p _IncEV is calculated by the formula: p _IncEV = q _EvEst *c _Wheel *0.005, q _EvEst is the flow rate in the current control cycle, and the wheel cylinder characteristics are the wheel cylinder PV characteristics.

In this embodiment, as shown in FIG4 , the boost valve control program analyzes the ABS valve control strategy, system pressure, wheel cylinder stiffness/target wheel cylinder pressure/actual wheel cylinder pressure, whether to allow boost/boost valve control mode, and outputs the target control current of the boost valve, boost valve driving time, average flow through the boost valve in the current cycle, and wheel cylinder pressure change through the boost valve in the current cycle. Compared with a simple on-off boost valve, this embodiment improves the control of the boost valve, thereby improving the pressure control of the electronic stability control of the vehicle body.

The pressure control method for vehicle body electronic stability control also includes a wheel cylinder model pressure estimation method. The wheel cylinder model pressure estimation method combines the pressure models of the previous pressure reducing valve and the pressure boosting valve to calculate the wheel cylinder model pressure, that is, p _DecAV and p _IncEV are processed in each cycle. When the system is just powered on, the initial value of the wheel cylinder pressure is the master cylinder pressure sampling value. The processing formula is:

p _Model =p _Modelold +p _IncEV -p _DecAV ,

Where p _Model is the wheel cylinder model pressure, is the wheel cylinder model pressure of the previous cycle, p _IncEV is the pressure change of the boost valve, and p _DecAV is the pressure change of the pressure reducing valve.

In one embodiment of the present invention, the motor pump load calculation and control method includes an accumulator model, a pump model, and a suction valve control method. The accumulator model calculates the liquid flow rate and accumulator pressure out of the accumulator according to the liquid flow rate entering the accumulator, the pump flow rate, the opening and closing state of the suction valve, and the master cylinder pressure; determines whether the accumulator is emptied according to the opening and closing state of the suction valve; calculates the flow rate flowing into the accumulator according to the pressure reducing valve model; and integrates the liquid flow rate flowing into and out of the accumulator over time to obtain the actual liquid storage volume in the accumulator. The pump model calculates the pump flow rate and the pressure difference at both ends of the pump according to the master cylinder pressure, motor speed, the opening and closing state of the suction valve, the accumulator liquid volume, and the accumulator pressure; determines the pressure at both ends of the pump according to the opening and closing state of the suction valve. When the suction valve is closed, the pressure at both ends of the pump is the system pressure and the accumulator pressure respectively; when the H suction valve is opened, the accumulator is in an empty state, and the pressure at both ends of the pump is the system pressure and the master cylinder pressure respectively; the load torque of the motor is calculated according to the pressure difference at both ends of the pump and the size characteristics of the plunger pump. The pump flow is the amount of brake fluid pumped out by the plunger pump during operation, which depends on the motor speed and the geometry of the plunger pump. The pressure difference across the pump represents the load on the pump, which is also the load on the motor.

The suction valve control method includes a suction valve opening permission strategy, a suction valve opening request strategy and a suction valve control strategy; the suction valve opening permission strategy includes two modes, the opening conditions of the first mode include the master cylinder pressure is less than 140 bar, the motor is not in the working state of emptying the accumulator, and the accumulator is empty and has a flow request for active supercharging; the opening conditions of the second mode include the opening conditions of the first mode and the source of the wheel cylinder pressure regulation is the auxiliary function module. The suction valve opening request strategy includes two opening requests, the request conditions of the opening request of the first mode include HAL receiving an active pressure control request and precharging the HCU; the request conditions of the opening request of the second mode include satisfying the opening conditions of the second mode and the auxiliary function module being in a working state. The suction valve control strategy includes a step mode and a main mode, the step mode includes the current gradually increasing to the suction valve opening current value, and entering the main mode; the main mode includes an opening mode and a maintenance mode, the opening mode gives the suction valve the maximum current to fully open the suction valve, and the maintenance mode maintains the minimum current value to keep the suction valve in an open state.

In this embodiment, there are two types of conditions for allowing the suction valve to be opened. One is the conventional condition for allowing the suction valve to be opened, and the other is the condition for allowing the suction valve to be permanently opened. The former is the premise for the latter, and the latter is for the VAF function. For example, the automatic parking function requires long-term pressure maintenance, during which the suction valve remains open to ensure that it can respond to active boost requests in a timely manner. Conventional suction valve opening conditions are: (1) The master cylinder pressure is less than 140 bar; (2) The motor is not in the process of emptying the accumulator; (3) The accumulator has been emptied and there is a flow request for active boost. In addition to the conditions for permanently opening the suction valve, there are also: (4) The target source of wheel cylinder pressure regulation does not come from wheel-level control functions such as ABS/TCS/VDC, but from VAF-related vehicle-level control functions. VAF is an auxiliary function module.

There are two types of suction valve opening requests: a regular opening request and a permanent opening request. The former is for TCS/VDC, which has an active boost function, and the latter is for the VAF function. Regular suction valve opening request conditions are: (1) HAL receives an active pressure control request; (2) the HCU is pre-charged to prevent the motor from forming a vacuum inside the HCU when the accumulator is emptied. When the opening request condition is met, if the regular opening condition is met, the suction valve will be controlled. The permanent opening request condition is that the VAF function is in effect. At this time, as long as the suction valve is allowed to be permanently opened, the suction valve will be controlled.

The control method of the suction valve is to realize the switch control of the solenoid valve by controlling the coil power-on current. However, considering that it needs to be kept open when the VAF is in effect, its coil must be energized for a long time. In order to prevent the solenoid valve coil from being energized for a long time and causing heat damage, it is necessary to design its power-on current waveform. The design of the HSV control current is divided into two parts: the step stage and the main stage. In the step stage, the current gradually increases to a level at which the HSV can be opened, and then enters the main stage. The main stage is divided into Open and Hold. In the Open stage, the maximum current will be passed to the HSV to ensure that the HSV is fully opened; the subsequent Hold current will remain at a lower level, so that the HSV can remain in the open state and prevent the solenoid valve coil from overheating.

In one embodiment of the present invention, the motor speed control method includes a variable conversion unit, a motor model unit, a motor speed control unit and a motor back-EMF sampling request unit; the variable conversion unit is used to convert the motor target speed and the motor load into the motor back-EMF and the motor load voltage respectively. The motor model unit is used to estimate the actual speed of the motor; the actual speed of the motor is estimated according to the linear relationship between the motor speed and the motor back-EMF, the Carr filtering method, the physical model of the motor and the back-EMF sampling.

The motor speed control unit establishes a speed closed-loop controller with feedforward and feedback according to the target speed, calculates the duty cycle of the drive motor, and uses the motor proportional integral controller to output the target control voltage. The motor back-EMF sampling request unit performs back-EMF sampling during the short stop of the motor speed drive.

In this embodiment, the function of the variable conversion unit is to convert variables of different dimensions into voltage units to facilitate subsequent calculations. Information such as load and speed is converted into equivalent voltage quantities to unify the calculation basis. These variables include the motor target speed and motor load, which are converted into the motor target back electromotive force and the part of the motor drive voltage that needs to overcome the load.

The main function of the motor model unit is to estimate the actual speed of the motor. The motor speed has a linear relationship with the motor back EMF, so the motor speed can be calculated by back EMF sampling. However, there is noise interference in voltage sampling, so the Kalman filter method is used to estimate the actual speed of the motor based on the physical model of the motor and combined with back EMF sampling.

Motor back-EMF sampling request unit, the estimation of motor speed depends on back-EMF sampling. Back-EMF sampling usually requires a short stop of the motor drive, and the back-EMF sampling is completed during this pause time interval. Here, a pause request is issued every 25ms, the motor drive is paused for 1ms, and the motor back-EMF sampling is completed within this 1ms time.

Compared with the prior art, the present invention comprehensively and fully considers the system pressure, wheel cylinder pressure, wheel cylinder model pressure estimation, motor pump load calculation and control, and motor speed control in the vehicle stability control system. The method and system proposed by the present invention have the advantages of small calculation amount, strong engineering practice, and strong robustness.

The present invention also provides a pressure control system for vehicle body electronic stability control, as shown in FIG5, FIG6 and FIG7, including a system pressure control module, a wheel cylinder pressure control module and a motor control module, an ABS module and an auxiliary function module. The system pressure control module arbitrates the braking requests of the driver, the ABS module and the auxiliary function module to obtain the target system pressure and the target wheel cylinder pressure, and when the auxiliary function module is working, controls the motor pump to pump the accumulator or the master cylinder brake fluid into the system pressure pipeline, and controls the opening of the pressure limiting valve to adjust the system pressure. The wheel cylinder pressure control module estimates the wheel cylinder model pressure according to the relationship between the system pressure, the boost valve control current and the pressure reducing valve control time, and analyzes the target wheel cylinder pressure to obtain the target boost valve control current and the target pressure reducing valve control time. The motor control module includes a motor target speed calculation module, a motor pump load calculation and control module and a motor speed control module. The motor target speed calculation module analyzes the accumulator liquid volume and the flow demand of active pressure building to obtain the motor target speed; the motor pump load calculation and control module uses an accumulator model to process the liquid volume and accumulator characteristics flowing into the accumulator through the pressure reducing valve to obtain the accumulator pressure, and uses a pump model to analyze the motor speed and the pressure difference at both ends of the pump to obtain the load torque applied by the pump to the motor, and during active supercharging, when the accumulator liquid is emptied, the suction valve is controlled to open to allow the liquid to flow into the accumulator; the motor speed control module analyzes the target motor speed and the motor load to control the motor speed.

In this embodiment, the system pressure refers to the pipeline fluid pressure between the pressure limiting valve and the boost valve. When the auxiliary function module in the vehicle body electronic stability control system is in effect, the system pressure needs to be actively adjusted. At this time, the motor pump operates to pump the brake fluid of the accumulator or the master cylinder into the system fluid pressure pipeline, and then adjusts the system pressure by controlling the pressure limiting valve, providing a basis for adjusting the wheel cylinder pressure. The system pressure control module architecture diagram is shown in Figure 6, where VAF is an auxiliary function module; the target arbitration program, pressure limiting valve control program, and system pressure model of the system pressure control module analyze VAF/target wheel cylinder pressure/flag, wheel cylinder pressure model, pump flow, boost valve flow, and master cylinder pressure, and output the system pressure and the control method of the pressure limiting valve.

The wheel cylinder pressure control module estimates the model pressure of the wheel cylinder according to the system pressure, the boost valve control current, and the pressure reducing valve control time; at the same time, the control current of the boost valve and the control time of the pressure reducing valve are calculated according to the target wheel cylinder pressure, so as to achieve the purpose of wheel cylinder hydraulic pressure control and model pressure estimation. The architecture diagram of the wheel cylinder pressure control module is shown in FIG7 . The wheel cylinder pressure control module uses the pipeline control program, the pressure reducing valve control program, the boost valve control program, the pressure reducing valve model, and the boost valve model to analyze the pressure collected by the master cylinder pressure sensor, the system model pressure, the target wheel cylinder pressure, and the pressure reducing valve driving voltage, and outputs the boost valve control current, the pressure reducing valve control time, the wheel cylinder model pressure, and the boost valve flow rate.

In one embodiment of the present invention, the motor target speed calculation module includes calculating the target flow of the pump according to the gradient requirement of active pressure building; compensating the target flow of the pump according to the active boost pressure difference; compensating the target flow of the pump according to the lateral acceleration; and calculating the target speed according to the accumulator liquid volume and the target flow.

So far, the technical solutions of the present invention have been described in conjunction with the preferred embodiments shown in the accompanying drawings. However, it is easy for those skilled in the art to understand that the protection scope of the present invention is obviously not limited to these specific embodiments. Without departing from the principle of the present invention, those skilled in the art can make equivalent changes or substitutions to the relevant technical features, and the technical solutions after these changes or substitutions will fall within the protection scope of the present invention.

Claims (9)

1. A pressure control method for vehicle body electronic stability control, characterized by comprising a system pressure control method, a wheel cylinder pressure control method, a motor pump load calculation and control method and a motor speed control method; Comprehensively realize the pressure control of the vehicle body electronic stability control according to the system pressure control method, the wheel cylinder pressure control method, the motor pump load calculation and control method and the motor speed control method; The system pressure control method includes an external control target arbitration program, a system pressure control program and a system model pressure estimation program. The external control target arbitration program includes the following steps: Step S1: Arbitrating the braking requests of the driver, the ABS module and the auxiliary function module to determine the target wheel cylinder pressure and the source of the braking request actually responded, wherein the braking request of the ABS module is the first priority, and the braking request of the auxiliary function module is the second priority. When the braking request value of the auxiliary function module is less than the braking request value of the driver, the braking request of the driver is responded to. When there is no braking request from the ABS and the auxiliary function module, the braking request of the driver is responded to. Step S2: Arbitrate the braking requests of the driver, ABS module and auxiliary function module, determine the target system pressure and whether to actively build pressure, wherein, when determining the target system pressure, the preset system pressure corresponding to the braking request of TCS/VDC is the first priority, and when the TCS/VDC active pressure building request flag is established, the maximum value of the target wheel cylinder pressure and the master cylinder pressure of the ABS module is determined as the target system pressure; the preset system pressure corresponding to the braking request of the auxiliary function module is the second priority, and when the TCS/VDC active pressure building request flag is not established, the preset system pressure corresponding to the braking request of the auxiliary function module is the target system pressure and is not greater than the master cylinder pressure; the preset system pressure corresponding to the braking request of the driver is the third priority; The system pressure control program determines the actual flow rate flowing into the master cylinder through the pressure limiting valve according to the flow rate pumped into the pipeline by the motor pump and the flow rate entering the wheel cylinder through the boost valve, and determines the control current of the pressure limiting valve according to the system target pressure, and controls the system pressure with the control current; The system model pressure estimation program determines the flow rate flowing into the system pressure line and the wheel cylinder pressure line according to the flow rate of the motor pump and the flow rate of the pressure limiting valve, and determines the system pressure according to the system characteristics. 2. The pressure control method according to claim 1, characterized in that the system model pressure estimation procedure comprises: determining the system stiffness, when the left wheel cylinder and the right wheel cylinder are connected through a pipeline, the system stiffness calculation formula is: Wherein, c _cir is the system stiffness, c _L is the left wheel cylinder stiffness, and c _R is the left wheel cylinder stiffness; when the target control fluid pressures of the left wheel cylinder and the right wheel cylinder are not equal, the system stiffness is the maximum value of the left wheel cylinder stiffness and the right wheel cylinder stiffness; When the pressure limiting valve is closed, the rate of change of system pressure is calculated as: d _pSystem = q _Rfp * c _cir , Where _dpSystem is the rate of change of system pressure, _qRfp is the pump flow rate, and _dpSystem is integrated to obtain the system pressure; When the master cylinder pressure is greater than or equal to the left wheel cylinder model pressure and the right wheel cylinder model pressure, the master cylinder pressure is the system pressure; When the pressure limiting valve performs active pressure increase, the system pressure is the maximum value of the left wheel cylinder model pressure and the right wheel cylinder model pressure. When the pressure limiting valve performs active pressure reduction, the system pressure converges to the master cylinder pressure over time. 3. The pressure control method according to claim 2 is characterized in that the system pressure control program determines the control current according to the actual flow of the pressure limiting valve, the difference between the target circuit pressure and the master cylinder pressure, and the actual flow q _USV calculation formula is: q _USV = q _Rfp - q _L - q _R , Wherein, q _L is the actual flow rate of the left wheel cylinder, and q _R is the actual flow rate of the right wheel cylinder; the control current i _USV is obtained as follows: i _USV = LookTable (q _USV ,pTgt _cir -pMC), Among them, LookTable() is the lookup function, pTgt _cir is the target circuit pressure, and pMC is the master cylinder pressure. 4. The pressure control method according to claim 3, characterized in that the wheel cylinder pressure control method comprises a valve control strategy design program, a pressure reducing valve control program and a pressure increasing valve control program; the valve control strategy design program comprises controlling the valve to increase pressure when the target wheel cylinder pressure is greater than the wheel cylinder model pressure, and controlling the valve to reduce pressure when the target wheel cylinder pressure is less than the wheel cylinder model pressure; The pressure reducing valve control program includes calculating the driving control time according to the accumulator pressure and the target wheel cylinder pressure. The control time T _AV is calculated by the following formula: Where p _Model is the wheel cylinder model pressure, p _Acc is the accumulator pressure, p _Grad is the pressure reduction rate of the pressure reducing valve in the current cycle, T _Response is the response time, and the calculation formula of p _Grad is: p _Grad = c _Wheel * q _AV , Where c _Wheel is the velocity coefficient, C _d is the flow coefficient, A is the valve hole area of the pressure reducing valve, ρ is the brake fluid density, and q _AV is the pressure reducing flow rate; the calculation formula of T _Response is: T _Response =T _OpenResponse -T _{CloseResponse} , Among them, T _OpenResponse is the open response time, T _{CloseResponse} is the close response time, and the calculation formula of T _OpenResponse is: T _OpenResponse ＝c _open +k _OpenU *U _vr +k _OpenP *p _Model +k _OpenUP *U _vr *p _Model , Among them, c _open is the opening response coefficient, k _OpenU is the voltage response coefficient, U _vr is the pressure reducing valve driving voltage, k _OpenP is the model response coefficient, p _Model is the wheel cylinder model pressure, and k _OpenUP is the fusion response coefficient; the calculation formula of T _{CloseResponse} is: T _{CloseResponse} ＝c _Close +k _CloseP *p _Tgt , Wherein, c _Close is the closing response coefficient, k _CloseP is the wheel cylinder pressure coefficient, and p _Tgt is the wheel cylinder pressure; The pressure reducing valve control program further includes calculating the pressure reducing amount p _DecAV and the average flow q _AVMean according to the actual control time and the actual pressure reducing rate of the pressure reducing valve in the current cycle. The calculation formulas of the pressure reducing amount p _DecAV and the average flow q _AVMean are: p _DecAV = p _Grad *min (0.005, T _AV ), Among them, min() is the minimum function, p _Grad is the pressure reduction rate of the pressure reducing valve in the current cycle, and q _AV is the pressure reduction flow rate; The boost valve control program calculates the target flow through the boost valve based on the target wheel cylinder pressure and the wheel cylinder model pressure, and calculates the control current of the boost valve based on the actual pressure difference of the boost valve and the flow characteristics of the boost valve, and controls the boost valve with the control current of the boost valve. 5. The pressure control method according to claim 4 is characterized in that the boost valve control program includes six modes: Open, Close, DP, Pulse, FastPulse and FixPulse; the Open mode is when the boost valve is open and the control current is 0; the Close mode is when the boost valve is closed and the control current is 1.5A; the DP mode includes converting the target pressure into the target flow, and the conversion formula is: Wherein, q _Tgt is the target flow rate, p _Tgt is the target pressure, k is the response time value, p _Model is the wheel cylinder model pressure, c _Wheel is the rate coefficient, the DP mode also includes a comfort mode, the target flow rate of the comfort mode is 8cc/s, and the control current I _EV of the boost valve in the DP mode is: ΔP _EV =p _System -p _Model , I _EV =LookupTable (q _Tgt ,ΔP _EV ), Wherein, LookTable() is the lookup function, ΔP _EV is the pressure difference, p _System is the system pressure, and p _Model is the wheel cylinder model pressure; The Pulse mode and the FastPulse mode periodically perform discrete sampling on p _Tgt , and calculate the boost valve opening time T _EV according to the discretely sampled p _Tgt . The calculation formula of T _EV is: Wherein, p _GradEV is the pressure change rate, c _wheel is the rate coefficient, C _d is the flow coefficient, A is the valve hole area of the boost valve, ρ is the brake fluid density, p _TgtSample is the discrete sample pressure, and p _Model is the wheel cylinder model pressure; The FixPulse mode opens the boost valve at a fixed time period in a fixed cycle; The boost valve control program also includes performing a first-order filtering on the target control current of the boost valve, and using the filtering result as the control current; searching for the current flow q _EV of the boost valve according to the control current I _EV and the pressure difference ΔP _EV of the boost valve, and the search formula for the current flow q _EV is: q _EV = LookupTable(I _EV ,ΔP _EV ); and estimating the pressure change amount of the current control cycle according to the wheel cylinder characteristics, and the calculation formula for the pressure change amount p _IncEV is: p _IncEV = q _EvEst *c _Wheel *0.005, where q _EvEst is the flow rate of the current control cycle. 6. The pressure control method according to claim 1, characterized in that the motor pump load calculation and control method includes an accumulator model, a pump model, and a suction valve control method; The accumulator model calculates the liquid flow rate out of the accumulator and the accumulator pressure according to the liquid flow rate entering the accumulator, the pump flow rate, the opening and closing state of the suction valve and the master cylinder pressure; determines whether the accumulator is empty according to the opening and closing state of the suction valve; calculates the flow rate into the accumulator according to the pressure reducing valve model; and integrates the liquid flow rates in and out of the accumulator over time to obtain the actual liquid storage amount in the accumulator; The pump model calculates the pump flow and the pressure difference at both ends of the pump according to the main cylinder pressure, motor speed, the opening and closing state of the suction valve, the accumulator liquid volume, and the accumulator pressure; determines the pressure at both ends of the pump according to the opening and closing state of the suction valve, and when the suction valve is closed, the pressures at both ends of the pump are the system pressure and the accumulator pressure respectively; when the H suction valve is opened, the accumulator is in an emptying state, and the pressures at both ends of the pump are the system pressure and the main cylinder pressure respectively; calculates the load torque of the motor according to the pressure difference at both ends of the pump and the size characteristics of the plunger pump; The suction valve control method includes a suction valve opening permission strategy, a suction valve opening request strategy and a suction valve control strategy; the suction valve opening permission strategy includes two modes, the opening conditions of the first mode include that the master cylinder pressure is less than 140 bar, the motor is not in the working state of emptying the accumulator, and the accumulator is empty and there is a flow request for active pressurization; the opening conditions of the second mode include the opening conditions of the first mode and the source of wheel cylinder pressure regulation is the auxiliary function module; The suction valve opening request strategy includes two opening requests. The request conditions of the opening request of the first mode include that the HAL receives an active pressure control request and pre-charges the HCU; the request conditions of the opening request of the second mode include that the opening conditions of the second mode are met and the auxiliary function module is in a working state; The suction valve control strategy includes a step mode and a main mode. The step mode includes the current gradually increasing to the suction valve opening current value and entering the main mode. The main mode includes an opening mode and a maintaining mode. The opening mode gives the suction valve the maximum current to fully open the suction valve, and the maintaining mode maintains the minimum current value to keep the suction valve in an open state. 7. The pressure control method according to claim 1 is characterized in that the motor speed control method comprises a variable conversion unit, a motor model unit, a motor speed control unit and a motor back electromotive force sampling request unit; the variable conversion unit is used to convert the motor target speed and the motor load into the motor back electromotive force and the motor load voltage respectively; The motor model unit is used to estimate the actual speed of the motor; the actual speed of the motor is estimated according to the linear relationship between the motor speed and the motor back electromotive force, the Carr filtering method, the physical model of the motor and the back electromotive force sampling; The motor speed control unit establishes a speed closed-loop controller with feedforward and feedback according to the target speed, calculates the duty cycle of the drive motor, and uses the motor proportional-integral controller to output the target control voltage; The motor back-EMF sampling request unit performs back-EMF sampling during the time when the motor speed driving is temporarily stopped. 8. A pressure control system for vehicle body electronic stability control, characterized by comprising a system pressure control module, a wheel cylinder pressure control module and a motor control module, an ABS module and an auxiliary function module; The system pressure control module arbitrates the braking requests of the driver, the ABS module and the auxiliary function module to obtain the target system pressure and the target wheel cylinder pressure, and when the auxiliary function module is working, controls the motor pump to pump the accumulator or the master cylinder brake fluid into the system pressure pipeline, and controls the opening of the pressure limiting valve to adjust the system pressure; The wheel cylinder pressure control module estimates the wheel cylinder model pressure according to the relationship between the system pressure, the boost valve control current, and the pressure reducing valve control time, and analyzes the target wheel cylinder pressure to obtain the target boost valve control current and the target pressure reducing valve control time; The motor control module includes a motor target speed calculation module, a motor pump load calculation and control module and a motor speed control module. The motor target speed calculation module analyzes the accumulator liquid volume and the flow demand of active pressure building to obtain the motor target speed; the motor pump load calculation and control module uses an accumulator model to process the liquid volume and accumulator characteristics flowing into the accumulator through the pressure reducing valve to obtain the accumulator pressure, and uses a pump model to analyze the motor speed and the pressure difference at both ends of the pump to obtain the load torque applied by the pump to the motor, and during active supercharging, when the accumulator liquid is emptied, the suction valve is controlled to open to allow the liquid to flow into the accumulator; the motor speed control module analyzes the target motor speed and the motor load to control the motor speed. 9. The pressure control system according to claim 8 is characterized in that the motor target speed calculation module includes calculating the target flow of the pump according to the gradient requirement of active pressure building; compensating the target flow of the pump according to the active boost pressure difference; compensating the target flow of the pump according to the lateral acceleration; and calculating the target speed according to the accumulator liquid volume and the target flow.