Method for estimating wheel cylinder pressure of vehicle body electronic stability control system

Abstract

The application discloses a wheel cylinder pressure estimation method of a vehicle body electronic stability control system and relates to the technical field of wheel cylinder pressure, which comprises the following steps: S1, a wheel cylinder pressure determination method, S2, wheel cylinder pressure estimation, S3, wheel cylinder pressure control and S4, PID control simulation verification. The application analyzes the wheel cylinder pressure reduction process: in order to avoid frequent opening and closing of the electromagnetic valve, a step-by-step pressure reduction method of pressure reduction-pressure maintenance-pressure reduction is adopted, when the wheel cylinder pressure and the target pressure difference is greater than the set threshold 1MPA, the electromagnetic valve is fully opened, the wheel cylinder starts to reduce pressure, until the wheel cylinder pressure and the target pressure difference is less than -1MPA, the electromagnetic valve is fully closed, the wheel cylinder enters the pressure maintenance state, when the wheel cylinder pressure and the target pressure difference reaches 1MPA again, the pressure reduction is continued, so that the purpose of following pressure reduction is achieved, and the pressure control is realized.

Description

Technical Field

[0001] This invention relates to the field of wheel cylinder pressure technology, specifically a wheel cylinder pressure estimation method for a vehicle electronic stability control system. Background Technology

[0002] Currently, with the development of electric vehicles and intelligent vehicles, the braking systems of electric vehicles and intelligent vehicles have put forward requirements such as electronic power assist and active boost. The braking system is constantly evolving into a brake-by-wire system. Braking pressure is a prerequisite for realizing vehicle control. The function of the brake wheel cylinder is to convert the hydraulic energy input from the master cylinder into mechanical energy so that the brake enters the working state. There are two types of brake wheel cylinders: single-piston and double-piston. Single-piston brake wheel cylinders are mainly used in double leading shoe and double trailing shoe brakes, while double-piston brake wheel cylinders are more widely used. They can be used in leading and trailing shoe brakes, as well as bidirectional double leading shoe brakes and bidirectional self-boosting brakes.

[0003] Nevertheless, there are still problems with improper cylinder pressure estimation methods and inaccurate cylinder pressure estimates. Summary of the Invention

[0004] The purpose of this invention is to provide a wheel cylinder pressure estimation method for a vehicle electronic stability control system, in order to solve the problems mentioned in the background art.

[0005] To achieve the above objectives, the present invention provides the following technical solution: a wheel cylinder pressure estimation method for a vehicle electronic stability control system, comprising the following steps:

[0006] S1. Wheel cylinder pressure determination method: Obtain the oil flow rate through each pressure boosting valve, the inflow oil volume of the corresponding wheel cylinder, the oil flow rate of the corresponding pressure reducing valve, and the outflow oil volume of each wheel cylinder in the controller at the current moment, and determine the oil volume of each wheel cylinder and the wheel cylinder pressure of each wheel cylinder at the next moment.

[0007] S2. Wheel cylinder pressure estimation: By testing the PV characteristics of the wheel cylinder, the relationship between pressure difference and flow rate is obtained, as well as the relationship between wheel cylinder hydraulic pressure and flow rate or volume. Simultaneously, the flow and pressure characteristics of the hydraulic control high-speed switching valve and the brake wheel cylinder, as well as the pressure characteristic algorithm, are used for estimation.

[0008] S3, Wheel cylinder pressure control: The wheel cylinder pressure characteristics are tested by solenoid valve PWM control, and the process changes during pressurization and depressurization are tested respectively.

[0009] S4. PID control simulation verification: PID segmented control is used to verify the following of the wheel cylinder pressure under target pressure curves of different shapes, and the PID control response under the same target pressure curve is compared.

[0010] Preferably, step 1 includes the following steps:

[0011] S101. Obtain the current oil volume of various booster valves: Obtain the current oil flow rate through each booster valve in the controller, the inflow volume of the corresponding wheel cylinder, the oil flow rate of the corresponding pressure reducing valve, and the outflow volume of each wheel cylinder.

[0012] S102. Based on the oil inflow and outflow volumes of the wheel cylinders: Determine the oil volume of each wheel cylinder at the next moment by using the current oil inflow volume of each wheel cylinder and the previous oil inflow volume of each wheel cylinder.

[0013] S103. Based on the preset volume pressure and oil volume: Based on the preset volume pressure change and the oil volume of each wheel cylinder at the next moment, determine the wheel cylinder pressure at the next moment.

[0014] Preferably, step S2 further includes the following step:

[0015] S201, Wheel cylinder PV characteristic test: By testing the wheel cylinder PV characteristics, the relationship between pressure difference and flow rate and the relationship between wheel cylinder hydraulic pressure and flow rate or volume can be obtained. The corresponding wheel cylinder pressure can be obtained from the wheel cylinder brake fluid volume.

[0016] S202. Obtain wheel cylinder fluid pressure and volume: Estimate the flow and pressure characteristics of the high-speed switching valve and brake wheel cylinder by hydraulic control. Obtain the initial pressure difference by estimating the wheel cylinder pressure and master cylinder pressure. Substitute the initial pressure difference and the duty cycle control signals of the boost and depressurization solenoid valves into the computer for calculation to obtain the real-time flow rate of the brake fluid flowing into and out of the wheel cylinder, and calculate the volume of brake fluid flowing into and out of the wheel cylinder.

[0017] Preferably, step S3 further includes the following step:

[0018] S301. Analysis of the wheel cylinder pressurization process: Through PWM control of the solenoid valve, when the wheel cylinder pressurization control is activated, the wheel cylinder pressure will always increase rapidly. During the subsequent pressure follow-up process, the difference between the target pressure and the actual pressure is basically within 0.5MPa. Therefore, when the pressure difference is greater than 0.5MPa, on / off control is used, and the solenoid valve is fully opened to make the wheel cylinder pressure quickly approach the target pressure. When the pressure difference is less than 0.5MPa, the wheel cylinder pressure is finely adjusted by changing the duty cycle of the control signal.

[0019] Preferably, step S3 further includes the following step:

[0020] S302. Analysis of the wheel cylinder pressure reduction process: To avoid frequent opening and closing of the solenoid valve, a stepped pressure reduction method of pressure reduction-pressure holding-pressure reduction is adopted. When the difference between the wheel cylinder pressure and the target pressure is greater than the set threshold of 1 MPa, the solenoid valve is fully opened and the wheel cylinder begins to reduce pressure. When the difference between the wheel cylinder pressure and the target pressure is less than -1 MPa, the solenoid valve is fully closed and the wheel cylinder enters the pressure holding state. When the difference between the wheel cylinder pressure and the target pressure reaches 1 MPa again, pressure reduction continues, thereby achieving the purpose of following pressure reduction and realizing pressure control.

[0021] Preferably, step S4 further includes the following step:

[0022] S401. Simulation using a trapezoidal pressure curve: This method can effectively verify the entire pressurization-holding-depressurization process of the wheel cylinder pressure. Under the target trapezoidal wave curve, the segmented control method has a good control effect, with a maximum delay of only 26ms and almost no overshoot. During pressure holding, the wheel cylinder pressure can be well stabilized at a fixed level, and during depressurization, it can quickly follow the depressurization curve to achieve rapid depressurization. It can achieve pressure following for holding pressures of different target pressures and has good universality.

[0023] Preferably, step S4 further includes the following step:

[0024] S402. Through sine curve simulation: it is possible to verify the following effect of the cylinder pressure on the smooth curve. The segmented control responds 100ms faster than the PID control when following the initial pressure. This is because the segmented control uses on / off control under large pressure difference. The booster valve is fully open and quickly approaches the target pressure. When depressurizing, although the PID control curve is smoother than the segmented control curve, its response speed is still not as good as the segmented control.

[0025] Preferably, step S4 further includes the following step:

[0026] S403. Through triangular wave simulation: it can be used to test the response of the cylinder pressure to the target pressure when there is a corner. The PID control performs poorly in the descent phase. At the corner, the PID control error reaches 8 bar, while the segmented control error is only 3 bar. The segmented control still performs well when the target curve has a corner, and can quickly adjust the pressure to achieve following.

[0027] The stress feature algorithm includes a feature extraction algorithm, which specifically includes:

[0028]

[0029] In the formula: Δt represents the time interval, m represents the time interval, n represents the number of frames collected during the waiting time, and L represents the total pressure value;

[0030] The pressure feature algorithm also includes the pressure averaging algorithm, which is specifically as follows:

[0031]

[0032] Where: m j S represents the pressure value of the j-th group, where j represents a positive integer from 1 to k. k This represents the set of all pressure values, where n represents S. k The collection contains the pressure values ​​of each valve within the internal data set.

[0033] Compared with the prior art, the beneficial effects of the present invention are:

[0034] This invention achieves accurate cylinder pressure estimation by precisely estimating the cylinder pressure. Attached Figure Description

[0035] Figure 1 A schematic diagram of the overall structure is provided for embodiments of the present invention;

[0036] Figure 2 This is an internal module block diagram of the wheel cylinder pressure determination method provided in an embodiment of the present invention;

[0037] Figure 3 An internal module block diagram for wheel cylinder pressure estimation provided in an embodiment of the present invention;

[0038] Figure 4 This is an internal module block diagram of the wheel cylinder pressure control provided in an embodiment of the present invention;

[0039] Figure 5 This is an internal module block diagram for PID control simulation verification provided in an embodiment of the present invention. Detailed Implementation

[0040] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0041] Please see Figure 1-5 This invention provides a technical solution: a wheel cylinder pressure estimation method for a vehicle electronic stability control system, comprising the following steps:

[0042] S1. Wheel cylinder pressure determination method: Obtain the oil flow rate through each pressure boosting valve, the inflow oil volume of the corresponding wheel cylinder, the oil flow rate of the corresponding pressure reducing valve, and the outflow oil volume of each wheel cylinder in the controller at the current moment, and determine the oil volume of each wheel cylinder and the wheel cylinder pressure of each wheel cylinder at the next moment.

[0043] S2. Wheel cylinder pressure estimation: By testing the PV characteristics of the wheel cylinder, the relationship between pressure difference and flow rate is obtained, as well as the relationship between wheel cylinder hydraulic pressure and flow rate or volume. Simultaneously, the flow and pressure characteristics of the hydraulic control high-speed switching valve and the brake wheel cylinder, as well as the pressure characteristic algorithm, are used for estimation.

[0044] S3, Wheel cylinder pressure control: The wheel cylinder pressure characteristics are tested by solenoid valve PWM control, and the process changes during pressurization and depressurization are tested respectively.

[0045] S4. PID control simulation verification: PID segmented control is used to verify the following of the wheel cylinder pressure under target pressure curves of different shapes, and the PID control response under the same target pressure curve is compared.

[0046] Step 1 includes the following steps:

[0047] S101. Obtain the current oil volume of various booster valves: Obtain the current oil flow rate through each booster valve in the controller, the inflow volume of the corresponding wheel cylinder, the oil flow rate of the corresponding pressure reducing valve, and the outflow volume of each wheel cylinder.

[0048] S102. Based on the oil inflow and outflow volumes of the wheel cylinders: Determine the oil volume of each wheel cylinder at the next moment by using the current oil inflow volume of each wheel cylinder and the previous oil inflow volume of each wheel cylinder.

[0049] S103. Based on the preset volume pressure and oil volume: Based on the preset volume pressure change and the oil volume of each wheel cylinder at the next moment, determine the wheel cylinder pressure at the next moment.

[0050] Step S2 also includes the following steps:

[0051] S201, Wheel cylinder PV characteristic test: By testing the wheel cylinder PV characteristics, the relationship between pressure difference and flow rate and the relationship between wheel cylinder hydraulic pressure and flow rate or volume can be obtained. The corresponding wheel cylinder pressure can be obtained from the wheel cylinder brake fluid volume.

[0052] S202. Obtain wheel cylinder fluid pressure and volume: Estimate the flow and pressure characteristics of the high-speed switching valve and brake wheel cylinder by hydraulic control. Obtain the initial pressure difference by estimating the wheel cylinder pressure and master cylinder pressure. Substitute the initial pressure difference and the duty cycle control signal of the boost and depressurization solenoid valves into the computer for calculation to obtain the real-time flow rate of the brake fluid flowing into and out of the wheel cylinder, and calculate the volume of brake fluid flowing into and out of the wheel cylinder.

[0053] Step S3 also includes the following steps:

[0054] S301. Analysis of the wheel cylinder pressurization process: Through the PWM control of the solenoid valve, when the wheel cylinder pressurization control is activated, the wheel cylinder pressure will always increase rapidly. During the subsequent pressure follow-up process, the difference between the target pressure and the actual pressure is basically within 0.5MPA. Therefore, when the pressure difference is greater than 0.5MPA, the switch control is used, and the solenoid valve is fully opened to make the wheel cylinder pressure quickly approach the target pressure. When the pressure difference is greater than 0.5MPA, the wheel cylinder pressure is finely adjusted by changing the duty cycle of the control signal.

[0055] Step S3 also includes the following steps:

[0056] S302. Analysis of the wheel cylinder pressure reduction process: In order to avoid frequent opening and closing of the solenoid valve, a step-pressure reduction method of pressure reduction-pressure holding-pressure reduction is adopted. When the difference between the wheel cylinder pressure and the target pressure is greater than the set threshold of 1 MPa, the solenoid valve is fully opened and the wheel cylinder begins to reduce pressure. When the difference between the wheel cylinder pressure and the target pressure is less than -1 MPa, the solenoid valve is fully closed and the wheel cylinder enters the pressure holding state. When the difference between the wheel cylinder pressure and the target pressure reaches 1 MPa again, the pressure reduction continues, thereby achieving the purpose of following pressure reduction and realizing pressure control.

[0057] Step S4 also includes the following steps:

[0058] S401. Simulation using trapezoidal pressure curves: This method can effectively verify the entire pressurization-holding-pressure reduction process of the wheel cylinder pressure. Under the target trapezoidal wave curve, the segmented control method has a good control effect, with a maximum delay of only 26ms and almost no overshoot. During pressure holding, the wheel cylinder pressure can be well stabilized at a fixed level, and during pressure reduction, it can quickly follow the pressure reduction curve to achieve rapid pressure reduction. It can achieve pressure following for holding pressures of different target pressures and has good universality.

[0059] Step S4 also includes the following steps:

[0060] S402. Through sine curve simulation: it is possible to verify the following effect of the cylinder pressure on the smooth curve. The segmented control responds 100ms faster than the PID control when following the initial pressure. This is because the segmented control uses on / off control under large pressure difference. The pressure boosting valve is fully open and quickly approaches the target pressure. When depressurizing, although the PID control curve is smoother than the segmented control curve, its response speed is still not as good as the segmented control.

[0061] Step S4 also includes the following steps:

[0062] S403. Through triangular wave simulation: it can be used to test the response of the wheel cylinder pressure to the target pressure when there is a corner. The PID control performs poorly in the descent phase. At the corner, the PID control error reaches 8 bar, while the segmented control error is only 3 bar. The segmented control still performs well when the target curve has a corner, and can quickly adjust the pressure to achieve following.

[0063] The stress feature algorithm includes a feature extraction algorithm, which specifically includes:

[0064]

[0065] In the formula: Δt represents the time interval, m represents the time interval, n represents the number of frames collected during the waiting time, and L represents the total pressure value;

[0066] The pressure feature algorithm also includes the pressure averaging algorithm, which is specifically as follows:

[0067]

[0068] Where: m j S represents the pressure value of the j-th group, where j represents a positive integer from 1 to k. k This represents the set of all pressure values, where n represents S. k The collection contains the pressure values ​​of each valve within the internal data set.

[0069] It should be noted that, in this document, relational terms such as "first" and "second" are used only to distinguish one entity or operation from another, and do not necessarily require or imply any such actual relationship or order between these entities or operations. Furthermore, the terms "comprising," "including," or any other variations thereof are intended to cover non-exclusive inclusion, such that a process, method, article, or apparatus that comprises a list of elements includes not only those elements but also other elements not expressly listed, or elements inherent to such process, method, article, or apparatus.

[0070] Although embodiments of the invention have been shown and described, it will be understood by those skilled in the art that various changes, modifications, substitutions and alterations can be made to these embodiments without departing from the principles and spirit of the invention, the scope of which is defined by the appended claims and their equivalents.

Claims

1. A method for estimating wheel cylinder pressure in a vehicle electronic stability control system, characterized in that... Includes the following steps: S1. Wheel cylinder pressure determination method: Obtain the oil flow rate through each pressure boosting valve, the inflow oil volume of the corresponding wheel cylinder, the oil flow rate of the corresponding pressure reducing valve, and the outflow oil volume of each wheel cylinder in the controller at the current moment, and determine the oil volume of each wheel cylinder and the wheel cylinder pressure of each wheel cylinder at the next moment. S2. Wheel cylinder pressure estimation: By testing the PV characteristics of the wheel cylinder, the relationship between pressure difference and flow rate is obtained, as well as the relationship between wheel cylinder hydraulic pressure and flow rate or volume. Simultaneously, the flow and pressure characteristics of the hydraulic control high-speed switching valve and the brake wheel cylinder, as well as the pressure characteristic algorithm, are used for estimation. S3, Wheel cylinder pressure control: The wheel cylinder pressure characteristics are tested by solenoid valve PWM control, and the process changes during pressurization and depressurization are tested respectively. S4. PID control simulation verification: PID segmented control is used to verify the following of the wheel cylinder pressure under target pressure curves of different shapes, and the PID control response under the same target pressure curve is compared. Step S3 also includes the following steps: S301. Analysis of the wheel cylinder pressurization process: Through PWM control of the solenoid valve, when the wheel cylinder pressurization control is activated, the wheel cylinder pressure will always increase rapidly. During the subsequent pressure follow-up process, the difference between the target pressure and the actual pressure is basically within 0.5MPA. Therefore, when the pressure difference is greater than 0.5MPA, on / off control is used, and the solenoid valve is fully opened to make the wheel cylinder pressure quickly approach the target pressure. When the pressure difference is less than 0.5MPA, the wheel cylinder pressure is finely adjusted by changing the duty cycle of the control signal. Step S3 also includes the following steps: S302. Analysis of the wheel cylinder pressure reduction process: To avoid frequent opening and closing of the solenoid valve, a stepped pressure reduction method of pressure reduction-pressure holding-pressure reduction is adopted. When the difference between the wheel cylinder pressure and the target pressure is greater than the set threshold of 1 MPa, the solenoid valve is fully opened and the wheel cylinder begins to reduce pressure. When the difference between the wheel cylinder pressure and the target pressure is less than -1 MPa, the solenoid valve is fully closed and the wheel cylinder enters the pressure holding state. When the difference between the wheel cylinder pressure and the target pressure reaches 1 MPa again, pressure reduction continues, thereby achieving the purpose of following pressure reduction and realizing pressure control.

2. The wheel cylinder pressure estimation method for the vehicle electronic stability control system according to claim 1, characterized in that: Step 1 includes the following steps: S101. Obtain the current oil volume of various booster valves: Obtain the current oil flow rate through each booster valve in the controller, the inflow volume of the corresponding wheel cylinder, the oil flow rate of the corresponding pressure reducing valve, and the outflow volume of each wheel cylinder. S102. Based on the oil inflow and outflow volumes of the wheel cylinders: Determine the oil volume of each wheel cylinder at the next moment by using the current oil inflow volume of each wheel cylinder and the previous oil inflow volume of each wheel cylinder. S103. Based on the preset volume pressure and oil volume: Based on the preset volume pressure change and the oil volume of each wheel cylinder at the next moment, determine the wheel cylinder pressure at the next moment.

3. The wheel cylinder pressure estimation method for the vehicle electronic stability control system according to claim 1, characterized in that: Step S2 also includes the following steps: S201, Wheel cylinder PV characteristic test: By testing the wheel cylinder PV characteristics, the relationship between pressure difference and flow rate and the relationship between wheel cylinder hydraulic pressure and flow rate or volume can be obtained. The corresponding wheel cylinder pressure can be obtained from the wheel cylinder brake fluid volume. S202. Obtain wheel cylinder fluid pressure and volume: Estimate the flow and pressure characteristics of the high-speed switching valve and brake wheel cylinder by hydraulic control. Obtain the initial pressure difference by estimating the wheel cylinder pressure and master cylinder pressure. Substitute the initial pressure difference and the duty cycle control signals of the boost and depressurization solenoid valves into the computer for calculation to obtain the real-time flow rate of the brake fluid flowing into and out of the wheel cylinder, and calculate the volume of brake fluid flowing into and out of the wheel cylinder.

4. The wheel cylinder pressure estimation method for the vehicle electronic stability control system according to claim 1, characterized in that: Step S4 also includes the following steps: S401. Simulation using a trapezoidal pressure curve: This method can effectively verify the entire pressurization-holding-depressurization process of the wheel cylinder pressure. Under the target trapezoidal wave curve, the segmented control method has a good control effect, with a maximum delay of only 26ms and almost no overshoot. During pressure holding, the wheel cylinder pressure can be well stabilized at a fixed level, and during depressurization, it can quickly follow the depressurization curve to achieve rapid depressurization. It can achieve pressure following for holding pressures of different target pressures and has good universality.

5. The wheel cylinder pressure estimation method for the vehicle electronic stability control system according to claim 1, characterized in that: Step S4 also includes the following steps: S402. Through sine curve simulation: it is possible to verify the following effect of the cylinder pressure on the smooth curve. The segmented control responds 100ms faster than the PID control when following the initial pressure. This is because the segmented control uses on / off control under large pressure difference. The booster valve is fully open and quickly approaches the target pressure. When depressurizing, although the PID control curve is smoother than the segmented control curve, its response speed is still not as good as the segmented control.

6. The wheel cylinder pressure estimation method for the vehicle electronic stability control system according to claim 1, characterized in that: Step S4 also includes the following steps: S403. Through triangular wave simulation: it can be used to test the response of the cylinder pressure to the target pressure when there is a corner. The PID control performs poorly in the descent phase. At the corner, the PID control error reaches 8 bar, while the segmented control error is only 3 bar. The segmented control still performs well when the target curve has a corner, and can quickly adjust the pressure to achieve following.

Images