A pressure maintenance method for a multi-axis commercial vehicle brake-by-wire system based on motor-isolation valve collaboration

Abstract

The present invention provides a pressure-maintaining method for a multi-axis commercial vehicle brake-by-wire system based on motor-isolation valve collaboration. When the motor temperature rises due to continuous pressure maintenance, the pressure at oil outlets 1 and 2 is maintained by closing the pressure-building cylinder isolation valves PSV1 and PSV2 until the pressure drops significantly or the motor M shutdown time reaches a set value. The pressure-building cylinder isolation valves and motor M are then reopened for pressure compensation. The beneficial effects of the present invention are: when the integrated brake-by-wire system (QEBS system) needs to maintain pressure, the pressure is maintained by the pressure-building cylinder isolation valves, the motor drive current is reduced, and the brake pressure is monitored in real time. When the brake pressure decreases, the motor again compensates for the reduced pressure.

Description

Technical Field

[0001] The present invention relates to the technical field of wire control brakes, and mainly relates to a pressure maintaining method for a multi-axis commercial vehicle wire control brake system based on motor-isolation valve collaboration. Background Art

[0002] A brake-by-wire system refers to a braking system that can achieve braking through an electronically controlled valve group. Due to its electronically controlled braking feature, the brake-by-wire system is usually used in scenarios such as AEB, ACC, and autonomous driving that require active braking to replace or assist the driver in braking.

[0003] In existing multi-axis commercial vehicle brake-by-wire systems, brake pressure is established and maintained by a motor-ball screw mechanism that drives a pressure-building chamber. When brake pressure must be maintained for extended periods, the motor's output torque must be maintained. This causes significant heating of the motor and PCB, leading to demagnetization or structural damage, and increased system power consumption. Summary of the Invention

[0004] The purpose of the present invention is to overcome the shortcomings of the prior art and provide a pressure maintaining method for a multi-axis commercial vehicle wire control brake system based on motor-isolation valve collaboration.

[0005] The object of the present invention is achieved through the following technical solution: A method for maintaining pressure in a multi-axis commercial vehicle brake-by-wire system based on motor-isolation valve collaboration, the method comprising the following steps:

[0006] A1. Collect brake pedal travel data and vehicle deceleration signals to calculate the target pressure that needs to be established at the oil outlet.

[0007] A2. Collect the current of the pressure-building cylinder motor and estimate the temperature of the pressure-building cylinder motor;

[0008] A3. Determine whether the current pressure-building cylinder motor temperature exceeds a threshold. If not, proceed to step A5.

[0009] A4. Determine whether the current pressure error at the oil outlet exceeds a threshold, where the pressure error refers to the difference between the target pressure and the actual pressure measured by the pressure sensor. If yes, proceed to step A7.

[0010] A5. Use the target pressure of the oil outlet as the control target and the actual pressure of the oil outlet as the control feedback to perform PID control and calculate the target speed and position of the pressure-building cylinder motor.

[0011] A6. Perform servo control on the pressure-building cylinder motor. In this mode, the pressure-building cylinder isolation valve PSV remains open, and the process proceeds to step A1.

[0012] A7. Close the pressure-building cylinder isolation valve PSV;

[0013] A8. Delay for a certain period of time to ensure that the pressure-building cylinder isolation valve PSV is completely closed;

[0014] A9. Record the pressure cylinder motor position P0 and turn off the motor.

[0015] A10: Determine whether the current shutdown time of the pressure-building cylinder motor exceeds a threshold. If yes, proceed to step A13.

[0016] A11. Recalculate the target pressure of the oil outlet;

[0017] A12, determine whether the current pressure error at the oil outlet exceeds the threshold. If not, proceed to step A10;

[0018] A13, turn on the pressure-building cylinder motor and return to the pressure-building cylinder motor position P0;

[0019] A14. Open the pressure-building cylinder isolation valve PSV.

[0020] Furthermore, the calculation method of step A1 is to determine the braking deceleration through the target pedal force-deceleration curve, and then determine the target pressure according to the vehicle mass and brake parameters.

[0021] Furthermore, the calculation method of step A2 is: calculating the motor temperature based on the motor current, including the temperature rise calculation caused by the motor internal resistance and the temperature drop calculation caused by heat conduction / heat radiation, wherein the temperature rise calculation formula is as follows:

[0022]

[0023] Where, k is the motor heating rate; r is the heating rate coefficient, which can be measured by the bench; i m is the motor current, obtained through the current acquisition circuit; R m is the internal resistance of the motor;

[0024] The cooling calculation formula is as follows:

[0025]

[0026] Where, is the motor cooling rate; θ, θ e are the current motor temperature and the vehicle’s ambient temperature, respectively. The former is obtained through iterative calculation, and the latter is measured by the vehicle’s sensors; k d1 、k d4 is the heat conduction and heat radiation heat dissipation rate coefficient, which can be measured by the bench;

[0027] The current motor temperature can be updated based on the heating rate, cooling rate, and the motor temperature at the previous moment. The formula is as follows:

[0028]

[0029] Where θ0 is the result of the last iteration of the motor temperature calculation; t s Iterative calculation period for motor temperature.

[0030] Furthermore, in step A3, the threshold is determined according to the motor demagnetization temperature and the heat resistance temperature of the motor magnet adhesive.

[0031] The beneficial effects of the present invention are: when the integrated wire control brake system (QEBS system) needs to maintain pressure, the brake pressure is maintained by the pressure-building cylinder isolation valve, the motor drive current is reduced, and the brake pressure is monitored in real time. When the brake pressure is reduced, the reduced pressure is compensated again by the motor. BRIEF DESCRIPTION OF THE DRAWINGS

[0032] Figure 1 A schematic diagram of the system principle of a pressure maintaining method for a multi-axis commercial vehicle brake-by-wire system based on motor-isolation valve collaboration provided by an embodiment of the present invention is shown;

[0033] Figure 2 Shown is a schematic diagram of the process of the present invention. DETAILED DESCRIPTION

[0034] The present invention will be described in detail below with reference to the accompanying drawings and embodiments:

[0035] like Figure 1 The system principle diagram shown in the figure includes the simulation valve SSV, the main cylinder isolation valve CSV, the pressure-building cylinder isolation valve PSV, the pressure sensor PS, the position sensor Pts, the angle sensor RPS, the oil tank Resevior, the pedal simulator PFS, the test valve TSV, the power-assisting motor main cylinder assembly MSC1, MSC2, the controller MCU1, MCU2, and the communication channel CAN between the controllers MCU1 and MCU2. Among them, PSV1 and PSV2 are two pressure-building cylinder isolation valves, and the pressure-building cylinders ( Figure 1 The left side of the motor M is connected to the oil outlets 1 and 2. The pressure at the oil outlets 1 and 2 can be adjusted by controlling the rotation of the pressure-building cylinder motor M and driving the pressure-building cylinder piston to move left and right.

[0036] like Figure 2 As shown, the present invention provides a pressure maintenance method for a multi-axis commercial vehicle brake-by-wire system based on motor-isolation valve coordination. When the motor temperature rises due to continuous pressure maintenance, the pressure of oil outlets 1 and 2 is maintained by closing the pressure-building cylinder isolation valves PSV1 and PSV2 until the pressure drops significantly or the motor M shutdown time reaches a set value. The pressure-building cylinder isolation valve and motor M are then reopened for pressure compensation. The method includes the following steps:

[0037] A1. Step A1 calculates the current required braking time based on the collected brake pedal travel data and vehicle deceleration signals. Figure 1 The target pressure established at outlets 1 and 2 is calculated by determining the braking deceleration through the target pedal force-deceleration curve, and then determining the target pressure based on the vehicle mass and brake parameters.

[0038] The formula used in this embodiment is: pdl =MaR / 2Aμr

[0039] In the above formula, M is the vehicle mass, a is the vehicle deceleration requirement, R is the tire radius, A is the brake cylinder area, μ is the brake friction coefficient, r is the brake radius, and P is the braking force. pdl Target pressure calculated by QEBS based on pedal travel in non-ABS mode.

[0040] A2. Collect the current of the pressure-building cylinder motor and estimate the temperature of the pressure-building cylinder motor;

[0041] The specific calculation method is: calculate the motor temperature based on the motor current, including the temperature rise calculation caused by the motor internal resistance and the temperature drop calculation caused by heat conduction / heat radiation. The temperature rise calculation formula is as follows:

[0042]

[0043] Where, k is the motor heating rate; r is the heating rate coefficient, which can be measured by the bench; i m is the motor current, obtained through the current acquisition circuit; R m is the internal resistance of the motor;

[0044] The cooling calculation formula is as follows:

[0045]

[0046] Where, is the motor cooling rate; θ, θ e are the current motor temperature and the vehicle’s ambient temperature, respectively. The former is obtained through iterative calculation, and the latter is measured by the vehicle’s sensors; k d1 、k d4 is the heat conduction and heat radiation heat dissipation rate coefficient, which can be measured by the bench;

[0047] The current motor temperature can be updated based on the heating rate, cooling rate, and the motor temperature at the previous moment. The formula is as follows:

[0048]

[0049] Where θ0 is the result of the last iteration of the motor temperature calculation; t s Iterative calculation period for motor temperature.

[0050] A3. Determine whether the current pressure-building cylinder motor temperature exceeds a threshold. If not, proceed to step A5. The threshold is determined based on the motor demagnetization temperature and the heat resistance temperature of the motor magnet adhesive, and is set to 150 degrees Celsius here.

[0051] A4. Determine whether the pressure error at the current oil outlet exceeds the threshold (1 Bar). The pressure error refers to the difference between the target pressure and the actual pressure measured by the pressure sensor. If so, proceed to step A7. If the error is large, the motor needs to perform pressure regulation, and the pressure-building cylinder isolation valve pressure-maintaining mode cannot be entered.

[0052] Steps A5 and A6 are the conventional motor M pressure adjustment or maintenance mode. That is, step A5 uses the target pressure of the oil outlet as the control target and the actual pressure of the oil outlet as the control feedback to perform PID control, calculate the target speed and position of the motor M, and perform servo control of the motor M through step A6. In this mode, the PSV1 and PSV2 valves remain open, and then the process goes to step A1.

[0053] A7-A9, steps A7, A8, and A9 are the process of switching to the pressure-building cylinder isolation valve pressure-maintaining mode. First, step A7 closes the pressure-building cylinder isolation valve PSV (PSV1, PSV2), then step A8 delays 200ms to ensure that the pressure cylinder isolation valve PSV is completely closed, and finally step A8 records the motor M position P0 and turns off the motor M. The recorded position P0 is used to ensure that the motor M is in the correct position when restoring the conventional motor M pressure regulation mode, thereby preventing pressure fluctuations during the recovery process.

[0054] A10. Determine whether the current shutdown time of the pressure-building cylinder motor exceeds the threshold (60s). If so, proceed to step A13. According to the design, when the motor is shut down for more than this time, its temperature can be reduced to a safe range and the normal motor M pressure regulation mode can be restored.

[0055] A11-A12, recalculate the target pressure of the oil outlet and determine whether the current pressure error at the oil outlet exceeds the threshold (3 Bar). If the threshold is reached, it is necessary to restore to the normal motor M pressure regulation mode. If not, go to step A10;

[0056] A13-14, steps A13 and A14 are the process of returning to the normal motor M pressure regulation mode. First, step A13 turns on the pressure-building cylinder motor and returns to the pressure-building cylinder motor position P0. Then, step A14 reopens the pressure-building cylinder isolation valve PSV (PSV1, PSV2).

[0057] The embodiment of the present invention uses the pressure-building cylinder isolation valves PSV (PSV1, PSV2) to maintain pressure, thereby effectively suppressing the temperature rise of the motor, which is beneficial to the durability of the motor; at the same time, it also suppresses the temperature rise of the circuit board and improves its durability.

[0058] It is understandable that for those skilled in the art, any equivalent replacement or change to the technical solution and inventive concept of the present invention should fall within the scope of protection of the claims attached to the present invention.

Claims

1. A pressure maintenance method for a multi-axle commercial vehicle brake-by-wire system based on motor-isolation valve collaboration, characterized by: The method comprises the following steps: A1. Collect brake pedal travel data and vehicle deceleration signals to calculate the target pressure that needs to be established at the oil outlet. A2. Collect the current of the pressure-building cylinder motor and estimate the temperature of the pressure-building cylinder motor; A3. Determine whether the current pressure-building cylinder motor temperature exceeds a threshold. If not, proceed to step A5. A4. Determine whether the current pressure error at the oil outlet exceeds a threshold, where the pressure error refers to the difference between the target pressure and the actual pressure measured by the pressure sensor. If yes, proceed to step A7. A5. Use the target pressure of the oil outlet as the control target and the actual pressure of the oil outlet as the control feedback to perform PID control and calculate the target speed and position of the pressure-building cylinder motor. A6. Perform servo control on the pressure-building cylinder motor. In this mode, the pressure-building cylinder isolation valve PSV remains open, and the process proceeds to step A1. A7. Close the pressure-building cylinder isolation valve PSV; A8. Delay for a certain period of time to ensure that the pressure-building cylinder isolation valve PSV is completely closed; A9. Record the pressure cylinder motor position P0 and turn off the motor. A10: Determine whether the current shutdown time of the pressure-building cylinder motor exceeds a threshold. If yes, proceed to step A13. A11. Recalculate the target pressure of the oil outlet; A12, determine whether the current pressure error at the oil outlet exceeds the threshold. If not, proceed to step A10; A13, turn on the pressure-building cylinder motor and return to the pressure-building cylinder motor position P0; A14. Open the pressure-building cylinder isolation valve PSV; The calculation method of step A1 is to determine the braking deceleration through the target pedal force-deceleration curve, and then determine the target pressure according to the vehicle mass and brake parameters.

2. The pressure maintaining method of a multi-axis commercial vehicle brake-by-wire system based on motor-isolation valve coordination according to claim 1 is characterized in that: The calculation method for step A2 is: The motor temperature is calculated based on the motor current, including the temperature rise caused by the motor's internal resistance and the temperature drop caused by heat conduction / radiation. The temperature rise calculation formula is as follows: (1) Where, is the motor heating rate; is the heating rate coefficient, which can be measured by the bench; is the motor current, obtained through the current acquisition circuit; is the internal resistance of the motor; The cooling calculation formula is as follows: (2) Where, is the motor cooling rate; 、 The current motor temperature and the vehicle's ambient temperature are respectively. The former is obtained through iterative calculation, and the latter is measured by vehicle sensors. 、 is the heat conduction and heat radiation heat dissipation rate coefficient, which can be measured by the bench; The current motor temperature can be updated based on the heating rate, cooling rate, and the motor temperature at the previous moment. The formula is as follows: (3) Where, Calculate the last iteration result for the motor temperature; Iterative calculation period for motor temperature.

3. The pressure maintaining method for a multi-axle commercial vehicle brake-by-wire system based on motor-isolation valve coordination according to claim 2 is characterized in that: In step A3, the threshold is determined according to the motor demagnetization temperature and the heat resistance temperature of the motor magnet adhesive.

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