A multi-axle commercial vehicle line control brake system thermal decay compensation method based on deceleration correction

Abstract

The application discloses a kind of based on deceleration correction multi-axis commercial vehicle line control brake system heat decay compensation method, it is related to line control brake system field, including braking process judgment, calculating heating rate, calculating cooling rate, updating brake disc temperature, oil outlet pressure judgment, brake disc low temperature judgment, calculating normal braking efficiency, first-order filtering, brake disc high temperature judgment, calculating hot disc braking efficiency, first-order filtering, calculating braking efficiency decay ratio, calculating brake pressure target correction value.In the application, the estimated brake disc temperature is only used to judge whether the current brake is in low temperature or high temperature state, and the accuracy requirement of the parameters used in the estimation of the brake disc temperature is not high, and the influence of vehicle speed and wind speed does not need to be considered in the cooling rate.Meanwhile, the relationship between the brake disc temperature and the friction coefficient between the brake disc and the brake pad does not need to be known during the implementation process, so the function calibration is simpler.The braking force characteristics under different vehicle loads will not be changed.

Description

TECHNICAL FIELD

[0001] The present application relates to the field of brake-by-wire systems, in particular to a brake-by-wire system thermal decay compensation method for multi-axle commercial vehicles based on deceleration correction. BACKGROUND

[0002] The brake-by-wire system refers to a brake system that can be controlled by a valve group to achieve braking. Due to its electrically controllable braking characteristics, the brake-by-wire system is usually used in AEB, ACC, automatic driving and other scenarios that require active braking instead of or to assist the driver in braking.

[0003] Currently, in the existing brake-by-wire system for multi-axle commercial vehicles, the brake-by-wire system thermal decay compensation takes the brake friction coefficient as the monitoring object, establishes a semi-theoretical and semi-empirical model of brake disc temperature and friction coefficient, and increases the brake pressure output of the brake-by-wire system after calculating the reduction of the friction coefficient.

[0004] However, accurate brake disc temperature calculation is difficult to achieve, and its calculated value is difficult to provide accurate input for calculating the friction coefficient; in addition, the relationship between the brake disc temperature and the brake pair friction coefficient is complex, and it is difficult to establish a relationship curve that adapts to different working conditions and stages.

[0005] As shown in Figure 1 The integrated brake-by-wire system (QEBS, Qiaochao Electric Brake System) adopted by our company outputs a certain pressure at the first oil outlet and the second oil outlet according to the stroke of the brake pedal, i.e. the pressure value corresponding to the pressure sensor at Ps_SP1 and Ps_SP2 in the figure.

[0006] After the basic function of the QEBS is realized, when the driver steps on a certain brake pedal stroke, the system can calculate the braking intensity required by the driver, so as to obtain the target pressure at the first oil outlet and the second oil outlet, and compare it with the actual pressure collected by Ps_SP1 and Ps_SP2 to perform pressure closed-loop control, so that the system can output corresponding pressure at the first oil outlet and the second oil outlet to realize the braking intensity required by the driver. When in long downhill and other working conditions, after continuous braking of the vehicle, the brake disc temperature rises, and the friction coefficient between the brake disc and the friction plate decreases, resulting in a decrease in the pressure at the first oil outlet and the second oil outlet, and a decrease in the braking intensity of the whole vehicle. At this time, by increasing the target pressure at the first oil outlet and the second oil outlet, the reduced braking intensity can be compensated to a certain extent. The present application proposes a new method for increasing the target pressure at the first oil outlet and the second oil outlet, and the method does not depend on accurate brake disc temperature and friction coefficient estimation, thereby reducing the difficulty and cost of calibration. SUMMARY

[0007] The present application aims to overcome the deficiencies in the prior art, and provides a multi-axle commercial vehicle line control brake system heat decay compensation method based on deceleration correction, which corrects the line control brake system output target pressure by comparing the brake efficiency (deceleration and brake pressure ratio) of the brake disc at low temperature and high temperature, and increases the brake deceleration caused by the decrease of the friction coefficient due to the increase of the brake disc temperature by increasing the brake pressure.

[0008] The purpose of the present application is achieved by the following technical scheme: a multi-axle commercial vehicle line control brake system heat decay compensation method based on deceleration correction, comprising the following steps:

[0009] S1_1: determine whether the current is in the braking process, if yes, go to step S1_2, if no, go to step S1_3;

[0010] S1_2: calculate the brake disc temperature rising rate, the formula is as follows:

[0011]

[0012] In formula (1), is the brake disc temperature rising rate; M v is the vehicle mass; a rl is the real vehicle deceleration, measured by the real vehicle sensor; v v is the vehicle speed, measured by the real vehicle sensor; k r is the temperature rising rate coefficient, measured by the bench;

[0013] S1_3: calculate the brake disc temperature falling rate, the formula is as follows:

[0014]

[0015] In formula (2), is the brake disc temperature falling rate; θ is the current brake disc temperature, obtained by iterative calculation; θ e is the ambient temperature of the vehicle, measured by the whole vehicle sensor; k d1 , k d4 is the heat conduction and heat radiation heat dissipation rate coefficient, measured by the bench;

[0016] S1_4: update the current brake disc temperature according to the brake disc temperature rising rate obtained in step S1_2, the brake disc temperature falling rate obtained in step S1_3, and the brake disc temperature at the last time, the formula is as follows:

[0017]

[0018] In formula (3), θ0 is the last iteration result of the brake disc temperature calculation; t s is the brake disc temperature iterative calculation period;

[0019] S1_5: judging whether the pressure at the first oil outlet and the second oil outlet reaches a set pressure value, if yes, entering step S1_6, if no, ending the process;

[0020] S1_6: judging whether the current brake disc temperature θ is less than a low temperature threshold value according to the current brake disc temperature θ obtained in step S1_4, if yes, entering step S1_7, if no, entering step S1_9;

[0021] S1_7: calculating the braking efficiency when the brake disc temperature is less than the low temperature threshold value;

[0022] S1_8: performing first-order filtering processing on the braking efficiency obtained in step S1_7 to obtain the braking efficiency before thermal decay, and entering step S1_12;

[0023] S1_9: judging whether the current brake disc temperature θ is greater than a high temperature threshold value, if yes, entering step S1_10, if no, ending the process;

[0024] S1_10: calculating the braking efficiency when the brake disc temperature is greater than the high temperature threshold value;

[0025] S1_11: performing first-order filtering processing on the braking efficiency obtained in step S1_10 to obtain the braking efficiency after thermal decay, and entering step S1_12;

[0026] S1_12: calculating the braking efficiency decay ratio, which is the ratio of the braking efficiency after thermal decay obtained in step S1_11 to the braking efficiency before thermal decay obtained in step S1_8;

[0027] S1_13: calculating the target pressure correction coefficient of the first oil outlet and the second oil outlet when the brake disc temperature is greater than the high temperature threshold value, the correction coefficient being the reciprocal of the calculation result of S1_12, and the brake-by-wire system compensating the brake pressure at the first oil outlet and the second oil outlet according to the correction coefficient.

[0028] As a further technical solution, in step S1_1, when the first pressure sensor Ps_SP1 and the second pressure sensor Ps_SP2 detect brake pressure at the first oil outlet and the second oil outlet, it is judged that the brake is in the braking process.

[0029] As a further technical solution, in step S1_5, the set pressure value is 15±0.5 Bar.

[0030] As a further technical solution, in step S1_6, the low temperature threshold value is 150±5℃.

[0031] As a further technical solution, in the step S1_9, the high temperature threshold is 280±5℃.

[0032] As a further technical solution, in the step S1_13, the correction coefficient is set with a lower limit of 1.0 and an upper limit of 1.5.

[0033] As a further technical solution, in the steps S1_7 and S1_10, the following steps are adopted when calculating the braking efficiency:

[0034] S2_1: First, determine whether the current braking is in the energy recovery state. If yes, go to step S2_2, if no, go to step S2_3;

[0035] S2_2: Calculate the deceleration generated by the energy recovery of the vehicle driving motor, the formula is as follows:

[0036]

[0037] In formula (4), a dmt is the deceleration generated by the energy recovery of the vehicle driving motor in the braking energy recovery working condition; T dmt is the energy recovery torque of the vehicle driving motor in the braking energy recovery working condition, which is sent to the linear brake-by-wire system through the vehicle CAN bus; R whl is the tire radius;

[0038] S2_3: Calculate the deceleration generated by the vehicle resistance, considering the sliding damping and wind resistance, the formula is as follows:

[0039] a rsst = a r0 +k av v v 2 (5)

[0040] In formula (5), a rsst is the vehicle resistance deceleration; a r0 is the fixed resistance deceleration, which is obtained by real vehicle test; k av is the vehicle resistance coefficient, which is 0.5 times of the product of the wind resistance coefficient and the windward area;

[0041] S2_4: Calculate the deceleration generated by the braking of the linear brake-by-wire system, the formula is as follows:

[0042] a qebs = a rl -a dmt -a rsst (6)

[0043] In formula (6), if it is in the braking energy recovery working condition, then a dmtCalculated by formula (4);if not in energy recovery condition, then a dmt value is 0;

[0044] S2_5: Calculate the braking efficiency, the formula is as follows:

[0045]

[0046] In formula (7), E qebs is the braking efficiency;a qebs is the deceleration generated by the brake-by-wire system, calculated by formula (6);P qebs is the pressure at the first and second oil outlets, measured by the first pressure sensor Ps_SP1 and the second pressure sensor Ps_SP2 in the brake-by-wire system.

[0047] As a further technical solution, in step S2_1, if the brake-by-wire system receives an energy recovery signal sent by the vehicle CAN bus, it is determined that the current braking is in the braking energy recovery state, otherwise, it is determined that the current braking is not in the braking energy recovery state.

[0048] As a further technical solution, in step S2_5, when the brake models connected at the first and second oil outlets are the same, the P qebs in formula (7) takes the average of the pressures measured by the first pressure sensor Ps_SP1 and the second pressure sensor Ps_SP2;when the brake models connected at the first and second oil outlets are different, the P qebs in formula (7) takes the weighted average of the pressures measured by the first pressure sensor Ps_SP1 and the second pressure sensor Ps_SP2.

[0049] The beneficial effects of the present application are:

[0050] 1. In the present application, the estimated brake disc temperature is only used to determine whether the current brake is in a low temperature or high temperature state, and the accuracy requirement for the parameters used in the estimation of the brake disc temperature is not high, and the influence of vehicle speed and wind speed on the cooling rate does not need to be considered. At the same time, the relationship between the brake disc temperature and the friction coefficient between the brake disc and the friction plate does not need to be known during the implementation process, so the function calibration is simpler and the calibration difficulty of each vehicle model is reduced.

[0051] 2. In the present application, the brake pedal stroke-target vehicle deceleration relationship and deceleration closed-loop control do not need to be established, but the braking efficiency at the beginning of braking and the braking efficiency after the brake disc temperature rises for a long time are calculated and monitored within the current ignition cycle, and the oil outlet target pressure compensation is performed, and it is not a complete target deceleration closed-loop control, so that the braking force characteristics under different vehicle loads will not be changed. BRIEF DESCRIPTION OF DRAWINGS

[0052] Figure 1 This is a schematic diagram of the linear braking system in this invention.

[0053] Figure 2 This is a flowchart illustrating an embodiment of the present invention.

[0054] Figure 3 This is a schematic diagram of the braking performance calculation process in an embodiment of the present invention.

[0055] Explanation of reference numerals in the attached diagram: 1. Master cylinder; 2. Power steering module; 3. Wheel end; 4. Brake pedal; 5. First chamber; 6. Second chamber; 7. First oil outlet; 8. Second oil outlet. Detailed Implementation

[0056] The present invention will now be described in detail with reference to the accompanying drawings:

[0057] Example: Figure 1 The diagram shows the structure of the brake-by-wire system (QEBS) upon which this invention is based. The QEBS system includes a master cylinder 1, a booster module 2, a wheel end 3, a brake pedal 4, a first chamber 5, a second chamber 6, a first oil outlet 7, and a second oil outlet 8. The brake pedal 4 drives the master cylinder 1, which is connected to the wheel end 3 via the booster module 2. A first stroke sensor PTS1 and a second stroke sensor PTS2 are located at the connection between the brake pedal 4 and the master cylinder 1. The first stroke sensor PTS1 outputs the measured brake pedal stroke signal using PWM, and the second stroke sensor PTS1 outputs the measured brake pedal stroke signal using the SENT protocol. A first oil outlet 7 is located between the first chamber 5 of the master cylinder 1 and the wheel end 3. A second pressure sensor Ps_SP2 is located on the bypass of the first oil outlet 7 to detect the pressure at the first oil outlet 7. A second oil outlet 8 is located between the second chamber 6 of the master cylinder and the wheel end 3. A first pressure sensor Ps_SP1 is located on the bypass of the second oil outlet 8 to detect the pressure at the second oil outlet 8. The brake-by-wire system outputs corresponding braking pressure at the first oil outlet 7 and the second oil outlet 8 based on the measured brake pedal stroke signal; the first pressure sensor Ps_SP1 and the second pressure sensor Ps_SP2 are both located in the power assist module 2.

[0058] As attached Figure 2 As shown, a thermal fade compensation method for a multi-axle commercial vehicle brake-by-wire system based on deceleration correction includes the following steps:

[0059] S1_1: Determine whether the current braking process is in progress. If the determination is yes, proceed to step S1_2; otherwise, proceed to step S1_3. When the first pressure sensor Ps_SP1 and the second pressure sensor Ps_SP2 detect braking pressure at the first oil outlet 7 and the second oil outlet 8, it is determined that the braking process is in progress.

[0060] S1_2: Calculate the brake disc temperature rise rate, the formula is as follows:

[0061]

[0062] In formula (1), is the brake disc temperature rise rate; M v is the vehicle mass; a rl is the real vehicle deceleration, measured by the real vehicle sensor; v v is the vehicle speed, measured by the real vehicle sensor; k r is the temperature rise rate coefficient, measured by the bench;

[0063] S1_3: Calculate the brake disc temperature drop rate, as long as the brake disc temperature is greater than the ambient temperature, the temperature drop process will continue to occur, and the temperature drop rate formula is as follows:

[0064]

[0065] In formula (2), is the brake disc temperature drop rate; θ is the current brake disc temperature, obtained by iterative calculation; θ e is the ambient temperature of the vehicle, measured by the vehicle sensor; k d1 , k d4 is the heat conduction and heat radiation heat dissipation rate coefficient, measured by the bench;

[0066] S1_4: According to the brake disc temperature rise rate obtained in step S1_2, the brake disc temperature drop rate obtained in step S1_3, and the brake disc temperature at the last time, update the current brake disc temperature, the formula is as follows:

[0067]

[0068] In formula (3), θ0 is the last iteration result of the brake disc temperature calculation; t s is the brake disc temperature iterative calculation period;

[0069] S1_5: Determine whether the pressure at the first oil outlet 7 and the second oil outlet 8 reaches the set pressure value 15Bar (which can be adjusted within the range of 15±0.5Bar according to the actual vehicle condition), if the determination is yes, go to step S1_6, if the determination is no, the process ends (i.e. no heat fade compensation is performed);

[0070] S1_6: According to the current brake disc temperature θ obtained in step S1_4, determine whether θ is less than the low temperature threshold value 150℃ (which can be adjusted within the range of 150±5℃ according to the actual vehicle condition), if the determination is yes, go to step S1_7, if the determination is no, go to step S1_9;

[0071] S1_7: Calculate the braking efficiency when the brake disc temperature is lower than the low temperature threshold 150℃;

[0072] S1_8: First-order filter processing is performed on the braking efficiency obtained in step S1_7 to obtain the braking efficiency before thermal decay, and step S1_12 is entered;

[0073] S1_9: Determine whether the current brake disc temperature θ is greater than the high temperature threshold 280℃ (which can be adjusted within the range of 280±5℃ according to the actual vehicle condition), if yes, enter step S1_10, if no, the process ends;

[0074] S1_10: Calculate the braking efficiency when the brake disc temperature is higher than the high temperature threshold 280℃;

[0075] S1_11: First-order filter processing is performed on the braking efficiency obtained in step S1_10 to obtain the braking efficiency after thermal decay, and step S1_12 is entered;

[0076] S1_12: Calculate the braking efficiency decay ratio, which is the ratio of the braking efficiency after thermal decay obtained in step S1_11 to the braking efficiency before thermal decay obtained in step S1_8 (the ratio is usually less than 1);

[0077] S1_13: Calculate the target pressure correction coefficient at the first oil outlet 7 and the second oil outlet 8 when the brake disc temperature is higher than the high temperature threshold 280℃, the correction coefficient is the inverse of the result of S1_12 calculation, and the correction coefficient has a saturation threshold lower limit of 1.0 and an upper limit of 1.5, that is, when the obtained correction coefficient is less than 1.0, output 1.0, and greater than 1.5, output 1.5; The brake-by-wire system compensates the brake pressure at the first oil outlet 7 and the second oil outlet 8 according to the correction coefficient, that is, amplifying the oil outlet pressure by the corresponding proportion at the corresponding oil outlet.

[0078] As shown in the accompanying Figure 3 , the following steps are used when calculating the braking efficiency in steps S1_7 and S1_10:

[0079] S2_1: First determine whether the current braking is in energy recovery state, usually the vehicle CAN bus will send a clear signal value to indicate that the current is in energy recovery state, when receiving the signal value, it is determined that the current braking is in braking energy recovery state, and step S2_2 is entered; If the vehicle CAN bus sends other values different from the signal value, it is understood that the current braking is not in braking energy recovery state, and step S2_3 is entered;

[0080] S2_2: Calculate the deceleration generated by the vehicle drive motor energy recovery, the formula is as follows:

[0081]

[0082] in formula (4), a dmt is the deceleration generated by the energy recovery of the vehicle driving motor in the brake energy recovery working condition; T dmt is the torque generated by the energy recovery of the vehicle driving motor in the brake energy recovery working condition, which is sent to the brake-by-wire system through the CAN bus of the vehicle; R whl is the tire radius;

[0083] S2_3: calculate the deceleration generated by the vehicle resistance, considering the sliding damping and the wind resistance, and the formula is as follows:

[0084] a rsst = a r0 + k av v v 2 (5)

[0085] in formula (5), a rsst is the vehicle resistance deceleration; a r0 is the fixed resistance deceleration, which is obtained by real vehicle test; k av is the vehicle resistance coefficient, which is 0.5 times of the product of the wind resistance coefficient and the windward area;

[0086] S2_4: calculate the deceleration generated by the brake-by-wire system braking, and the formula is as follows:

[0087] a qebs = a rl -a dmt -a rsst (6)

[0088] in formula (6), if in the brake energy recovery working condition, then a dmt is calculated by formula (4); if not in the energy recovery working condition, then a dmt value is 0;

[0089] S2_5: calculate the brake efficiency, and the formula is as follows:

[0090]

[0091] in formula (7), E qebs is the brake efficiency; a qebs is the deceleration generated by the brake-by-wire system braking, which is calculated by formula (6); P qebs is the pressure at the first oil outlet 7 and the second oil outlet 8, which is measured by the first pressure sensor Ps_SP1 and the second pressure sensor Ps_SP2 in the brake-by-wire system. It should be noted that when the brake models connected at the first oil outlet 7 and the second oil outlet 8 are the same, the P qebsThe average of the pressures measured by the first pressure sensor Ps_SP1 and the second pressure sensor Ps_SP2 is taken; when the brake models connected at the first oil outlet 7 and the second oil outlet 8 are different, the P qebs The weighted average of the pressures measured by the first pressure sensor Ps_SP1 and the second pressure sensor Ps_SP2 is taken.

[0092] It can be understood that equivalent replacements or changes to the technical solutions and inventive concepts of the present application made by those skilled in the art shall fall within the protection scope of the claims appended to the present application.

Claims

1. A method for compensating for thermal fade in a multi-axle commercial vehicle brake-by-wire system based on deceleration correction, wherein the brake-by-wire system includes a master cylinder (1) driven by a brake pedal (4), the master cylinder (1) being connected to the wheel end (3) via a power assist module (2); a first stroke sensor (PTS1) and a second stroke sensor (PTS2) are provided at the connection between the brake pedal (4) and the master cylinder (1), the first stroke sensor (PTS1) and the second stroke sensor (PTS2) being used to detect the stroke signal of the brake pedal (4); a first oil outlet (7) is provided between the first cavity (5) of the master cylinder (1) and the wheel end (3), and the first oil outlet (7) is located beside... A second pressure sensor (Ps_SP2) is provided on the road to detect the pressure at the first oil outlet (7); a second oil outlet (8) is provided between the second chamber (6) of the master cylinder and the wheel end (3), and a first pressure sensor (Ps_SP1) is provided on the bypass of the second oil outlet (8) to detect the pressure at the second oil outlet (8); the brake-by-wire system outputs corresponding braking pressure at the first oil outlet (7) and the second oil outlet (8) according to the measured brake pedal (4) stroke signal; both the first pressure sensor (Ps_SP1) and the second pressure sensor (Ps_SP2) are located in the power assist module (2); the features are: Includes the following steps: S1_1: Determine whether the braking process is currently underway. If yes, proceed to step S1_2; otherwise, proceed to step S1_3. S1_2: Calculate the brake disc heating rate, using the following formula: In equation (1), M represents the brake disc heating rate. v For vehicle mass; a rl The actual vehicle deceleration is measured by sensors on the actual vehicle; v v The vehicle speed is measured by sensors on the actual vehicle; k r The heating rate coefficient is measured on the test bench. S1_3: Calculate the brake disc cooling rate using the following formula: In equation (2), θ represents the brake disc cooling rate; θ is the current brake disc temperature, obtained through iterative calculation. e The ambient temperature of the vehicle, measured by sensors throughout the vehicle; k d1 k d4 The heat transfer rate coefficients for heat conduction and heat radiation are measured by the test bench. S1_4: Update the current brake disc temperature based on the brake disc heating rate obtained in step S1_2, the brake disc cooling rate obtained in step S1_3, and the brake disc temperature at the previous moment, using the following formula: In equation (3), θ0 is the result of the previous iteration in calculating the brake disc temperature; t s The iterative calculation cycle for brake disc temperature; S1_5: Determine whether the pressure at the first oil outlet (7) and the second oil outlet (8) has reached the set pressure value. If yes, proceed to step S1_6; otherwise, the process ends. S1_6: Based on the current brake disc temperature θ obtained in step S1_4, determine whether θ is less than the low temperature threshold. If yes, proceed to step S1_7; otherwise, proceed to step S1_9. S1_7: Calculate the braking performance when the brake disc temperature is below the low temperature threshold. S1_8: Perform first-order filtering on the braking performance obtained in step S1_7 to obtain the braking performance before thermal fade, and proceed to step S1_12. S1_9: Determine whether the current brake disc temperature θ is greater than the high temperature threshold. If yes, proceed to step S1_10; otherwise, the process ends. S1_10: Calculate the braking performance when the brake disc temperature is higher than the high temperature threshold; S1_11: Perform first-order filtering on the braking performance obtained in step S1_10 to obtain the braking performance after thermal fade, and proceed to step S1_12. S1_12: Calculate the braking performance degradation ratio, which is the ratio of the braking performance after thermal degradation obtained in step S1_11 to the braking performance before thermal degradation obtained in step S1_8. S1_13: Calculate the target pressure correction coefficient at the first oil outlet (7) and the second oil outlet (8) when the brake disc temperature is higher than the high temperature threshold. The correction coefficient is the reciprocal of the calculation result of S1_12. The brake-by-wire system compensates for the brake pressure at the first oil outlet (7) and the second oil outlet (8) according to the correction coefficient.

2. The thermal fade compensation method for a multi-axle commercial vehicle brake-by-wire system based on deceleration correction according to claim 1, characterized in that: In step S1_1, when the first pressure sensor (Ps_SP1) and the second pressure sensor (Ps_SP2) detect braking pressure at the first oil outlet (7) and the second oil outlet (8), it is determined that the system is in the braking process.

3. The thermal fade compensation method for a multi-axle commercial vehicle brake-by-wire system based on deceleration correction according to claim 2, characterized in that: In step S1_5, the pressure value is set to 15±0.5 Bar.

4. The thermal fade compensation method for a multi-axle commercial vehicle brake-by-wire system based on deceleration correction according to claim 3, characterized in that: In step S1_6, the low temperature threshold is 150±5℃.

5. The thermal fade compensation method for a multi-axle commercial vehicle brake-by-wire system based on deceleration correction according to claim 4, characterized in that: In step S1_9, the high temperature threshold is 280±5℃.

6. The thermal fade compensation method for a multi-axle commercial vehicle brake-by-wire system based on deceleration correction according to claim 5, characterized in that: In step S1_13, the correction coefficient is set with a lower limit of 1.0 and an upper limit of 1.5 for the saturation threshold.

7. The thermal fade compensation method for a multi-axle commercial vehicle brake-by-wire system based on deceleration correction according to claim 6, characterized in that: The following steps are used to calculate the braking performance in steps S1_7 and S1_10: S2_1: First, determine whether the current braking is in the energy recovery state. If yes, proceed to step S2_2; otherwise, proceed to step S2_3. S2_2: Calculate the deceleration generated by the energy recovery of the vehicle's drive motor, using the following formula: In equation (4), a dmt This refers to the deceleration generated by the energy recovery of the vehicle's drive motor under regenerative braking conditions. T dmt This refers to the energy recovery torque of the vehicle's drive motor under regenerative braking conditions. This torque is transmitted to the brake-by-wire system via the vehicle's CAN bus. whl The radius of the tire; S2_3: Calculate the deceleration caused by the overall vehicle resistance, considering sliding damping and wind resistance, as shown in the following formula: and rsst =a r0 +k av in v 2 (5) In equation (5), a rsst For vehicle resistance deceleration; a r0 The deceleration is a constant resistance, obtained through real-vehicle testing; k av The drag coefficient is 0.5 times the product of the drag coefficient and the frontal area. S2_4: Calculate the deceleration generated by braking in the brake-by-wire system, using the following formula: a qebs =a rl -a dmt -a rsst (6) In equation (6), if the braking energy recovery condition is in effect, then a dmt Calculated by equation (4); if not in energy recovery mode, then a dmt The value is 0; S2_5: Calculate braking performance, using the following formula: In equation (7), E qebs For braking performance; a qebs The deceleration generated by braking of the brake-by-wire system is calculated using equation (6); P qebs The pressure at the first oil outlet (7) and the second oil outlet (8) is measured by the first pressure sensor (Ps_SP1) and the second pressure sensor (Ps_SP2) in the brake-by-wire system.

8. The thermal fade compensation method for a multi-axle commercial vehicle brake-by-wire system based on deceleration correction according to claim 7, characterized in that: In step S2_1, if the brake-by-wire system receives an energy recovery signal sent by the vehicle's CAN bus, it determines that the current braking is in a braking energy recovery state; otherwise, it determines that the current braking is not in a braking energy recovery state.

9. The thermal fade compensation method for a multi-axle commercial vehicle brake-by-wire system based on deceleration correction according to claim 8, characterized in that: In step S2_5, when the brake models connected to the first oil outlet (7) and the second oil outlet (8) are the same, the P in formula (7) qebs Take the average pressure measured by the first pressure sensor (Ps_SP1) and the second pressure sensor (Ps_SP2); when the brake models connected to the first oil outlet (7) and the second oil outlet (8) are different, the P in formula (7) qebs The weighted average of the pressures measured by the first pressure sensor (Ps_SP1) and the second pressure sensor (Ps_SP2) is taken.

Images