CN117799595A - Hydraulic brake circuit fault diagnosis method based on OneBox line control brake system - Google Patents

Abstract

The specification discloses a hydraulic brake circuit fault diagnosis method based on an OneBox line control brake system, which comprises four parts of electric cylinder circuit fault diagnosis, master cylinder and simulator brake circuit fault diagnosis, PSV fault diagnosis and CSV fault diagnosis. According to the embodiment of the specification, the circuit faults of the brake system are detected through four diagnosis processes, the pressure detection and the pressure increasing and reducing control are realized by using the pressure sensor and the electric cylinder unit, the diagnosis of the pressure building function is realized, and the leakage performance of the valve, the hydraulic cylinder and the wheel cylinder is diagnosed; the clamping fault diagnosis of the valve and the electric power assisting unit can be performed on the pressure increasing isolation valve, the main cylinder isolation valve, the simulation valve, the pedal simulator, the isolation valve and the wheel cylinder, and the accuracy is high.

Description

Hydraulic brake circuit fault diagnosis method based on OneBox line control brake system

Technical Field

The invention relates to the technical field of automobile braking, in particular to a hydraulic braking loop fault diagnosis method based on an OneBox line control braking system.

Background

In recent years, intelligent driving technology of automobiles is rapidly developed, and a brake-by-wire system which is indispensable in an intelligent driving scheme is also increasingly important. There are Two main approaches to current brake-by-wire systems, namely the Two-box approach of the "eboster+esc" combination and the OneBox approach integrating brake boosting and ESC functions. Wherein OneBox integrates the functions of two control units into one control unit, the integration level and the complexity of the OneBox are higher. The brake system with high integration and complexity is difficult to check and is not easy to locate a fault source once the brake system fails. Therefore, there is a need for a method for diagnosing faults of a hydraulic brake circuit based on OneBox, which can quickly and accurately check whether the hydraulic brake circuit has faults and fault positions by controlling the brake system through external instructions without disassembling OneBox components and related pipelines when the brake system has faults.

Therefore, a fault diagnosis method suitable for a high-integration brake system is needed to be researched so as to quickly and accurately check fault conditions.

Disclosure of Invention

The present disclosure provides a hydraulic brake circuit fault diagnosis method based on OneBox brake-by-wire system, which is used for overcoming at least one technical problem existing in the related art.

According to an embodiment of the present disclosure, there is provided a hydraulic brake circuit fault diagnosis method based on an OneBox brake control system, including

The method comprises the steps of acquiring real vehicle calibration parameters of each device of a hydraulic brake circuit of a vehicle to be detected under normal conditions, wherein the hydraulic brake circuit comprises a hydraulic unit, a master cylinder unit, a circuit solenoid valve unit, a brake wheel cylinder, an isolation valve unit, a simulator and an electric cylinder unit, wherein the hydraulic brake circuit comprises a hydraulic pressure unit, a master cylinder unit, a circuit solenoid valve unit, a brake wheel cylinder, an isolation valve unit, a simulator and an electric cylinder unit

The hydraulic unit stores hydraulic pressure and is used for communicating the simulator, the main cylinder unit and the electric cylinder unit, and comprises a liquid storage tank and a hydraulic pipeline;

the master cylinder unit comprises a master cylinder, a pedal rod, a displacement sensor, a test valve TSV and a first pressure sensor P1, wherein the master cylinder is communicated with the liquid storage tank through the hydraulic unit, the test valve TSV is arranged between the master cylinder unit and the liquid storage tank, the pedal rod is arranged on the master cylinder, the displacement sensor is arranged on the master cylinder and used for detecting the braking displacement of the pedal rod, and the first pressure sensor P1 is arranged on the master cylinder;

The loop solenoid valve unit comprises eight solenoid valves, wherein the eight solenoid valves comprise four pressure increasing solenoid valves ISO1, ISO2, ISO3, ISO4 and four pressure reducing solenoid valves Dump1, dump2, dump3, dump4, ISO4 and Dump4 are arranged in series to form a first passage, ISO3 and Dump3 are arranged in series to form a second passage, ISO2 and Dump2 are arranged in series to form a third passage, ISO1 and Dump1 are arranged in series to form a fourth passage, the brake wheel cylinder comprises four wheel cylinders, each wheel cylinder is respectively connected with one passage, the first passage is connected with the second passage in parallel, the third passage is connected with the fourth passage in parallel, and the four passages are communicated with the hydraulic unit to form a loop;

the isolation valve unit comprises a first master cylinder isolation valve CSV1, a second master cylinder isolation valve CSV2, a first electric cylinder isolation valve PSV1 and a second electric cylinder isolation valve PSV2, wherein the first master cylinder isolation valve CSV1 is communicated with a master cylinder and one end of a first passage which is parallel to a second passage through a hydraulic pipeline, the second master cylinder isolation valve CSV2 is communicated with the master cylinder and one end of a third passage which is parallel to a fourth passage through the hydraulic pipeline, the first electric cylinder isolation valve PSV2 is communicated with an electric cylinder and one end of the first passage which is parallel to the second passage through the hydraulic pipeline, and the second electric cylinder isolation valve PSV2 is communicated with the electric cylinder and one end of the third passage which is parallel to the fourth passage through the hydraulic pipeline;

One end of the simulator is communicated with the liquid storage tank through a hydraulic pipeline, and the other end of the simulator is connected with the solenoid valve SSV through the hydraulic pipeline and is communicated with the master cylinder;

the electric cylinder unit comprises an electric cylinder, a piston, a motor, a pressure relief valve PRV and a second pressure sensor P2, wherein the motor drives the piston to move to change the pressure of the electric cylinder;

the electric cylinder, the piston, the first electric cylinder isolation valve PSV1, the second electric cylinder isolation valve PSV2, the second pressure sensor P2, the pressure relief valve PRV and a hydraulic pipeline which are communicated form an electric cylinder loop; the first master cylinder isolation valve CSV1, the second master cylinder isolation valve CSV2, the electromagnetic valve SSV, the test valve TSV, the simulator, the master cylinder and the first pressure sensor P1 form a master cylinder and simulator brake loop;

the real vehicle calibration parameters comprise a pressure value range of a first pressure sensor P1, a pressure value range P2 of a second pressure sensor, a displacement range of a piston and a range of a deviation value of a brake loop liquid volume;

in a preset time, controlling the electric cylinder piston to move to an initial position, controlling the PSV1, the PSV2, the SSV, the PRV and the Dump1, the Dump2, the Dump3 and the Dump4 to be closed, controlling the CSV1, the CSV2, the TSV, the ISO1, the ISO2, the ISO3 and the ISO4 to be opened, controlling the electric cylinder unit to boost pressure, comparing an actual parameter with a real vehicle calibration parameter, determining the fault of a hydraulic braking loop according to the comparison result of the actual parameter and the real vehicle calibration parameter, firstly performing fault diagnosis on the electric cylinder loop,

If the electric cylinder loop detects that the non-PSV fault exists, determining a fault position and a fault type;

if the electric cylinder loop detects that PSV faults exist, PSV fault diagnosis is carried out, and a fault valve and a fault type are determined;

otherwise, the master cylinder and the simulator brake circuit are subjected to fault diagnosis,

if the master cylinder and the simulator braking loop have faults, determining a specific fault valve and a specific fault type;

otherwise, diagnosing the CSV fault and determining the fault condition of the CSV valve;

and obtaining a fault diagnosis result of the hydraulic brake circuit of the vehicle to be detected.

Further, the step of performing fault diagnosis on the electric cylinder circuit includes:

s101, controlling the electric cylinder unit to stably boost pressure at a preset speed, if the pressure value acquired by the second pressure sensor P2 reaches a target pressure value within a preset time and the piston advancing distance is within a displacement range, continuing the test, otherwise, judging that the electric cylinder unit is a serious leakage fault, and stopping the test;

s102, controlling the electric cylinder unit to continuously boost for 1S, calculating the piston advancing distance and the liquid volume deviation of the electric cylinder circuit in the beginning 500ms, and performing the following fault diagnosis according to the calculation result after 500 ms:

If the piston advancing distance is not greater than the first threshold value and the liquid volume deviation amount of the electric cylinder loop is not greater than the second threshold value, judging that the electric cylinder loop has no fault, and entering a master cylinder and a simulator brake loop for diagnosis;

if the piston advancing distance is larger than the first threshold value and the liquid volume deviation amount of the electric cylinder loop is not larger than the second threshold value, judging that PSV or PRV leaks and fails, and entering step S103;

if the liquid volume deviation amount of the electric cylinder loop is larger than the second threshold value and not larger than the third threshold value, judging that the PSV fails;

if the liquid volume deviation amount of the electric cylinder loop is larger than a third threshold value, judging that the PRV is in fault;

s103, controlling the piston to return to the initial position, closing the 4 ISO valves, CSV1 and CSV2, if the piston returns to the initial position within a preset time period, entering S104, otherwise, judging the clamping failure of the piston of the electric cylinder, and stopping the test;

s104, controlling the electric cylinder unit to stably boost pressure at a preset speed, if the pressure value acquired by the first pressure sensor P1 reaches the target pressure within a preset time, and the piston advance position is within a displacement range, entering a step S105, otherwise, judging that the PRV leaks;

s105, continuing to boost for 1S, calculating the piston advance distance and the liquid volume deviation amount of the electric cylinder circuit in the beginning 500ms, and performing the following fault diagnosis according to the calculation result after 500 ms:

If the piston advancing distance is between the fourth threshold value and the sixth threshold value and the liquid volume deviation is not larger than the fifth threshold value, judging that the PRV has no fault, and entering a master cylinder and simulator brake circuit for diagnosis;

if the piston advancing distance is not greater than the fourth threshold value and the liquid volume deviation is not greater than the fifth threshold value, judging that the PSV fails to open;

if the piston advancing distance is not greater than the sixth threshold value and the liquid volume deviation amount is greater than the fifth threshold value, judging that the PRV is in fault;

and if the piston advancing distance is larger than the sixth threshold value, judging that the PRV is in fault.

Further, the liquid volume deviation of the electric cylinder circuit is calculated according to the following steps:

and obtaining a liquid volume change value of the brake circuit under normal conditions according to a brake circuit PV curve tested by the real vehicle, and comparing the liquid volume change value with a hydraulic cylinder volume change value caused by piston movement to obtain a deviation value of the liquid volume of the brake circuit.

Further, the step of performing fault diagnosis on the master cylinder and the simulator brake circuit, if the master cylinder and the simulator brake circuit have faults, determining specific fault valves and fault types includes:

s201, under the condition that an electric cylinder loop is free from faults, controlling all hydraulic valves and pistons to restore to an initial state;

S202, opening a PSV1, closing TSV, closing CSV2, controlling an electric cylinder unit to boost pressure with a preset fixed boosting gradient, and entering S203 if the pressure value acquired by a first pressure sensor reaches the target pressure within a preset time and the piston advancing distance is within a displacement range; otherwise, judging that the master cylinder and the simulator brake loop have serious leakage faults, and stopping the test;

s203, controlling the electric cylinder unit to decompress with a preset fixed depressurization gradient, and if the pressure value acquired by the first pressure sensor reaches a depressurization target pressure value within a preset time and the piston advancing distance is within a displacement range, entering into a step S204; otherwise, judging that the brake loop has serious leakage fault, and stopping the test;

s204, maintaining the current pressure value for 1S, entering a pressure maintaining stage, and if the pressure value of the first pressure sensor P1 is not greater than a seventh threshold value and the piston movement speed is not greater than an eighth threshold value, judging that the piston of the auxiliary cavity of the master cylinder in the loop is stuck or the CSV1 is not opened, and stopping the test; if the piston advancing distance is larger than a seventh threshold value or the piston moving speed is larger than an eighth threshold value, judging that the loop has serious leakage fault, and stopping the test; if the pressure value of the first pressure sensor P1 is higher than the seventh threshold value and no serious leakage fault exists, judging that the main cylinder and the CSV have no faults, and entering S205;

S205, testing a simulator loop, controlling the electric cylinder to keep the current piston state unchanged, opening the SSV, and judging the SSV clamping failure if the pressure value of the first pressure sensor P1 or the second pressure sensor P2 is larger than a ninth threshold value; otherwise, enter S206 step;

s206, closing the SSV, controlling the electric cylinder unit to push the piston forwards at a preset pushing speed, opening the SSV, and judging that the TSV is stuck if the pressure value of the first pressure sensor P1 or the second pressure sensor P2 is greater than a ninth threshold value; otherwise, judging that the master cylinder and the simulator brake circuit have no faults.

Further, if the electric cylinder circuit detects that the PSV fault exists, the PSV fault diagnosis is performed, and the fault valve and the fault type are determined, including the steps of:

s301, controlling all hydraulic valves to return to an initial state and controlling the electric cylinder piston to return to an initial position when the electric cylinder loop fault diagnosis judges that the PSV is faulty;

s302, opening PSV1, closing CSV1, closing 4 ISO, controlling the electric cylinder unit to smoothly boost at a preset speed,

if the pressure value acquired by the second pressure sensor P2 reaches the target pressure within the preset time period and the piston advanced position is within the displacement range, executing step S303;

Otherwise, judging that the leakage is serious, and stopping the test;

s303, controlling the electric cylinder unit to continuously boost, wherein fault diagnosis is as follows:

if the piston advancing distance is not greater than a tenth threshold value, judging that the PSV1 is stuck;

if the piston advancing distance is between the sixth threshold value and the tenth threshold value and the P1 pressure value is not greater than the ninth threshold value, judging that the PSV1 has no fault, and entering into S304;

if the piston advancing distance is between the sixth threshold value and the tenth threshold value and the P1 pressure value is larger than the ninth threshold value, judging that the PSV2 has leakage faults;

s304, opening PSV2 and CSV1, closing PSV1 and CSV2, controlling the electric cylinder unit to stably boost pressure at a preset speed, and if the pressure value acquired by the second pressure sensor P2 reaches the target pressure and the piston is in the forward position within the displacement range within a preset time, entering S305, otherwise, judging serious leakage fault, and stopping the test;

s305, continuing pressurizing, and performing the following fault diagnosis:

if the piston advancing distance is not greater than a tenth threshold value, judging the clamping stagnation fault of the PSV2 valve;

if the piston advancing distance is between the sixth threshold value and the tenth threshold value and the first P1 pressure is not greater than the ninth threshold value, judging that the PSV2 has no fault;

if the piston advance distance is between the sixth threshold and the tenth threshold and the first P1 pressure is greater than the ninth threshold, then a leak fault is determined for PSV 1.

Further, the step of diagnosing the CSV fault and determining the fault condition of the CSV valve includes:

s401, under the condition that the fault diagnosis of the electric cylinder loop is normal, controlling all hydraulic valves and electric cylinder pistons to restore to an initial state;

s402, opening PSV1, closing CSV1, closing 4 ISO valves, controlling an electric cylinder unit to stably boost pressure at a preset speed, if the pressure value acquired by a second pressure sensor P2 reaches the target pressure within a preset time and the piston advanced position is within a displacement range, entering S403, otherwise, judging that the electric cylinder unit is seriously leaked and fault, and stopping testing;

s403, continuing pressurizing, and diagnosing faults as follows:

if the piston advancing distance is not greater than the sixth threshold value and the P1 pressure value is greater than the ninth threshold value, judging CSV1 leakage fault;

if the piston advancing distance is not greater than the eleventh threshold value and the pressure value acquired by the first sensor P1 is not greater than the ninth threshold value, the CSV1, the ISO3 and the ISO4 valves have no faults, and the S404 is entered;

if the piston advancing distance is between the sixth threshold value and the eleventh threshold value and the pressure acquired by the first pressure sensor P1 is not greater than the ninth threshold value, the ISO valve has leakage fault;

s404, opening PSV2 and CSV1, closing PSV1 and CSV2, controlling an electric cylinder unit to stably boost pressure at a preset speed, and stopping testing when the pressure value acquired by the second pressure sensor P2 reaches the target pressure and the piston is in the forward position within the displacement range, and entering S405, otherwise, judging that the leakage is serious;

And S405, continuing pressurizing, and diagnosing faults as follows:

if the piston advancing distance is not greater than the sixth threshold value and the pressure value of the first pressure sensor P1 is greater than the ninth threshold value, judging CSV2 leakage fault;

if the piston advancing distance is not greater than the eleventh threshold value and the pressure value of the first pressure sensor P1 is not greater than the ninth threshold value, the CSV2, the ISO1 and ISO2 valves have no faults;

if the piston advance distance is between the sixth and eleventh thresholds and the pressure value of the first sensor P1 is not greater than the ninth threshold, the ISO valve has a leak failure.

The beneficial effects of the embodiment of the specification are as follows:

according to the embodiment of the specification, the hydraulic brake circuit fault diagnosis method based on the OneBox line control brake system is provided, four diagnosis processes are reasonably designed by utilizing the existing pressure sensor and electric cylinder unit of the brake system aiming at the system design of the line control brake system, and the system automatically selects the steps to be executed according to the current state, so that the comprehensive fault diagnosis and pressure building function diagnosis of the brake circuit can be realized, including diagnosis of various valves, hydraulic cylinders, wheel cylinders, leakage performance and clamping faults of various valves and electric cylinder units. The method of the embodiment of the specification can realize rapid and comprehensive detection of the pressure-increasing isolation valve, the main cylinder isolation valve, the simulation valve, the pedal simulator, the isolation valve and the wheel cylinder, and has higher accuracy and strong practicability.

The innovation points of the embodiment of the specification comprise:

1. in the present specification, the fault diagnosis of the hydraulic brake system is divided into four parts, namely, electric cylinder fault diagnosis, master cylinder and simulator brake circuit fault diagnosis, PSV fault diagnosis and CSV fault diagnosis, and the fault detection is completed by using the state of the existing equipment of the system, which is one of the innovation points of the embodiments of the present specification.

2. In the specification, the pressure-increasing isolation valve, the master cylinder isolation valve, the simulation valve, the pedal simulator, the isolation valve and the wheel cylinder are rapidly and comprehensively detected, and the accuracy is high, so that the pressure-increasing isolation valve, the master cylinder isolation valve, the simulation valve, the pedal simulator, the isolation valve and the wheel cylinder are one of innovation points of the embodiment of the specification.

3. In the present specification, all four diagnostic processes are not required to be executed, and the system can automatically select the steps to be executed according to the current state, so that the fault detection efficiency is high, which is one of the innovation points of the embodiments of the present specification.

Drawings

In order to more clearly illustrate the embodiments of the present description or the technical solutions in the related art, the drawings that are required to be used in the embodiments or the related technical descriptions will be briefly described, and it is apparent that the drawings in the following description are only some embodiments of the present invention, and other drawings may be obtained according to the drawings without inventive effort for those skilled in the art.

FIG. 1 is a schematic diagram of a hydraulic brake circuit of an OneBox brake system according to an embodiment of the present disclosure;

FIG. 2 is a schematic flow chart of a diagnostic method for OneBox brake system hydraulic brake circuit according to an embodiment of the present disclosure;

FIG. 3 is a flow chart of an electric cylinder circuit diagnostic step according to an embodiment of the present disclosure;

FIG. 4 is a schematic flow chart of a master cylinder and simulator brake circuit diagnostic step provided in an embodiment of the present disclosure;

FIG. 5 is a flowchart illustrating a PSV fault diagnosis procedure according to an embodiment of the present disclosure;

fig. 6 is a flowchart illustrating a CSV fault diagnosis procedure according to an embodiment of the present disclosure.

Detailed Description

The technical solutions of the embodiments of the present specification will be clearly and completely described below with reference to the drawings of the embodiments of the present specification, and it is apparent that the described embodiments are only some embodiments of the present invention, not all embodiments. All other embodiments, which can be made by those skilled in the art based on the embodiments of the invention without any inventive effort, are intended to be within the scope of the invention.

It should be noted that the terms "comprising" and "having" and any variations thereof in the embodiments and figures herein are intended to cover a non-exclusive inclusion. For example, a process, method, system, article, or apparatus that comprises a list of steps or elements is not limited to only those listed steps or elements but may include other steps or elements not listed or inherent to such process, method, article, or apparatus.

The embodiment of the specification discloses a hydraulic brake circuit fault diagnosis method based on an OneBox line control brake system, which comprises four parts of electric cylinder fault diagnosis, master cylinder and simulator brake return diagnosis, PSV fault diagnosis and CSV fault diagnosis.

Firstly, real vehicle calibration parameters of all equipment of a hydraulic brake circuit of a vehicle to be detected under normal conditions are obtained.

Fig. 1 is a schematic structural diagram of an OneBox brake system hydraulic brake circuit according to an embodiment of the present disclosure. As shown in fig. 1, the hydraulic brake circuit includes a hydraulic unit 1, a master cylinder unit 2, a circuit solenoid valve unit 3, a brake cylinder 4, an isolation valve unit 5, a simulator 6, and an electric cylinder unit 7.

The hydraulic unit 1 stores hydraulic pressure and is used for communicating the simulator, the main cylinder unit and the electric cylinder unit, and comprises a liquid storage tank and a hydraulic pipeline.

The master cylinder unit 2 includes a master cylinder which is communicated with the liquid storage tank through the hydraulic unit, a pedal lever which is provided on the master cylinder, a displacement sensor which is provided on the master cylinder to detect a braking displacement amount of the pedal lever, a test valve TSV which is provided between the master cylinder unit and the liquid storage tank, and a first pressure sensor P1 which is provided on the master cylinder.

The circuit solenoid valve unit 3 includes eight solenoid valves including four pressure increasing solenoid valves ISO1, ISO2, ISO3, ISO4 and four pressure reducing solenoid valves Dump1, dump2, dump3, dump4, ISO4 being arranged in series with Dump4 to form a first passage, ISO3 being arranged in series with Dump3 to form a second passage, ISO2 being arranged in series with Dump2 to form a third passage, ISO1 being arranged in series with Dump1 to form a fourth passage. The brake cylinder 4 includes four wheel cylinders, each wheel cylinder is connected with a passage, wherein the first passage is connected in parallel with the second passage, the third passage is connected in parallel with the fourth passage, and the four passages are communicated with the hydraulic unit to form a loop.

The isolation valve unit 5 includes a first master cylinder isolation valve CSV1, a second master cylinder isolation valve CSV2, a first electric cylinder isolation valve PSV1, and a second electric cylinder isolation valve PSV2, wherein the first master cylinder isolation valve CSV1 communicates with the master cylinder and one end of the first passage connected in parallel with the second passage through a hydraulic line, the second master cylinder isolation valve CSV2 communicates with the master cylinder and one end of the third passage connected in parallel with the fourth passage through a hydraulic line, the first electric cylinder isolation valve PSV2 communicates with the electric cylinder and one end of the first passage connected in parallel with the second passage through a hydraulic line, and the second electric cylinder isolation valve PSV2 communicates with the electric cylinder and one end of the third passage connected in parallel with the fourth passage through a hydraulic line.

One end of the simulator 6 is communicated with the liquid storage tank through a hydraulic pipeline, and the other end of the simulator is connected with the solenoid valve SSV through the hydraulic pipeline and is communicated with the master cylinder.

The electric cylinder unit 7 comprises an electric cylinder, a piston, a motor, a pressure relief valve PRV and a second pressure sensor P2, wherein the motor drives the piston to move to change the pressure of the electric cylinder, the pressure relief valve is arranged between the electric cylinder unit and the hydraulic unit, and the second pressure sensor is arranged on a pipeline between the electric cylinder and the electric cylinder isolation valve.

The electric cylinder, the piston, the first electric cylinder isolation valve PSV1, the second electric cylinder isolation valve PSV2, the second pressure sensor P2, the pressure relief valve PRV and a hydraulic pipeline which are communicated form an electric cylinder loop; the first master cylinder isolation valve CSV1, the second master cylinder isolation valve CSV2, the electromagnetic valve SSV, the test valve TSV, the simulator, the master cylinder and the first pressure sensor P1 form a master cylinder and simulator brake loop.

The real vehicle calibration parameters comprise a pressure value range of the first pressure sensor P1, a pressure value range of the second pressure sensor P2, a displacement range of the piston and a range of a deviation value of the liquid volume of the brake circuit.

And in a preset time, controlling the electric cylinder piston to move to an initial position, controlling the PSV1, the PSV2, the SSV, the PRV and the Dump1, the Dump2, the Dump3 and the Dump4 to be closed, controlling the CSV1, the CSV2, the TSV, the ISO1, the ISO2, the ISO3 and the ISO4 to be opened, controlling the electric cylinder unit to boost pressure, comparing an actual parameter with a real vehicle calibration parameter, and determining the fault of a hydraulic braking circuit according to the comparison result of the actual parameter and the real vehicle calibration parameter.

Fig. 2 is a schematic flow chart of a diagnostic method for a hydraulic brake circuit of an OneBox brake control system according to an embodiment of the present disclosure. As shown in fig. 2, firstly, performing fault diagnosis on an electric cylinder loop, and if the electric cylinder loop detects that a non-PSV fault exists, determining a fault position and a fault type; if the electric cylinder loop detects that PSV faults exist, PSV fault diagnosis is carried out, and a fault valve and a fault type are determined; otherwise, performing fault diagnosis on the master cylinder and the simulator braking circuit, and determining specific fault valves and fault types if faults exist in the master cylinder and the simulator braking circuit; otherwise, diagnosing the CSV fault and determining the fault condition of the CSV valve; and obtaining a fault diagnosis result of the hydraulic brake circuit of the vehicle to be detected.

Fig. 3 is a schematic flow chart of an electric cylinder circuit diagnosis procedure according to an embodiment of the present disclosure. As shown in fig. 3, the step of diagnosing a fault in the electric cylinder circuit includes:

s101, controlling the electric cylinder unit to stably boost at a preset speed, if the pressure value acquired by the second pressure sensor P2 reaches a target pressure value within a preset time, and the piston advancing distance is within a displacement range, continuing the test, otherwise, judging that the electric cylinder unit is a serious leakage fault, and stopping the test.

S102, controlling the electric cylinder unit to continuously boost for 1S, calculating the piston advancing distance and the liquid volume deviation of the electric cylinder circuit in the beginning 500ms, and performing the following fault diagnosis according to the calculation result after 500 ms:

if the piston advancing distance is not greater than the first threshold value and the liquid volume deviation amount of the electric cylinder loop is not greater than the second threshold value, judging that the electric cylinder loop has no fault, and entering a master cylinder and a simulator brake loop for diagnosis;

if the piston advancing distance is larger than the first threshold value and the liquid volume deviation amount of the electric cylinder loop is not larger than the second threshold value, judging that PSV or PRV leaks and fails, and entering step S103;

if the liquid volume deviation amount of the electric cylinder loop is larger than the second threshold value and not larger than the third threshold value, judging that the PSV fails;

and if the liquid volume deviation amount of the electric cylinder circuit is larger than a third threshold value, judging that the PRV is in fault.

And S103, controlling the piston to return to the initial position, closing the 4 ISO valves, CSV1 and CSV2, if the piston returns to the initial position within a preset time period, entering the step S104, otherwise, judging the clamping failure of the piston of the electric cylinder, and stopping the test.

And S104, controlling the electric cylinder unit to stably boost at a preset speed, if the pressure value acquired by the first pressure sensor P1 reaches the target pressure within a preset time, and the piston advance position is within the displacement range, entering the step S105, otherwise, judging that the PRV leaks.

S105, continuing to boost for 1S, calculating the piston advance distance and the liquid volume deviation amount of the electric cylinder circuit in the beginning 500ms, and performing the following fault diagnosis according to the calculation result after 500 ms:

if the piston advancing distance is between the fourth threshold value and the sixth threshold value and the liquid volume deviation is not larger than the fifth threshold value, judging that the PRV has no fault, and entering a master cylinder and simulator brake circuit for diagnosis;

if the piston advancing distance is not greater than the fourth threshold value and the liquid volume deviation is not greater than the fifth threshold value, judging that the PSV fails to open;

if the piston advancing distance is not greater than the sixth threshold value and the liquid volume deviation amount is greater than the fifth threshold value, judging that the PRV is in fault;

and if the piston advancing distance is larger than the sixth threshold value, judging that the PRV is in fault.

In a specific implementation, the liquid volume deviation of the electric cylinder circuit is calculated according to the following steps:

and obtaining a liquid volume change value of the brake circuit under normal conditions according to a brake circuit PV curve tested by the real vehicle, and comparing the liquid volume change value with a hydraulic cylinder volume change value caused by piston movement to obtain a deviation value of the liquid volume of the brake circuit.

The first threshold, the second threshold, the third threshold, the fourth threshold, the fifth threshold and the sixth threshold in the test step are all data obtained by real vehicle calibration parameters.

FIG. 4 is a flow chart of a master cylinder and simulator brake circuit diagnostic procedure according to an embodiment of the present disclosure. As shown in fig. 4, the steps of diagnosing faults of the master cylinder and the simulator brake circuit, and determining specific fault valves and fault types if faults exist in the master cylinder and the simulator brake circuit, include:

and S201, controlling all the hydraulic valves and the pistons to restore to the initial state under the condition that the electric cylinder circuit has no fault.

S202, opening a PSV1, closing TSV, closing CSV2, controlling an electric cylinder unit to boost pressure with a preset fixed boosting gradient, and entering S203 if the pressure value acquired by a first pressure sensor reaches the target pressure within a preset time and the piston advancing distance is within a displacement range; otherwise, judging that the master cylinder and the simulator brake circuit have serious leakage faults, and stopping the test.

S203, controlling the electric cylinder unit to decompress with a preset fixed depressurization gradient, and if the pressure value acquired by the first pressure sensor reaches a depressurization target pressure value within a preset time and the piston advancing distance is within a displacement range, entering into a step S204; otherwise, judging that the brake loop has serious leakage fault, and stopping the test.

S204, maintaining the current pressure value for 1S, entering a pressure maintaining stage, and if the pressure value of the first pressure sensor P1 is not greater than a seventh threshold value and the piston movement speed is not greater than an eighth threshold value, judging that the piston of the auxiliary cavity of the master cylinder in the loop is stuck or the CSV1 is not opened, and stopping the test; if the piston advancing distance is larger than a seventh threshold value or the piston moving speed is larger than an eighth threshold value, judging that the loop has serious leakage fault, and stopping the test; if the pressure value of the first pressure sensor P1 is higher than the seventh threshold value and there is no serious leakage fault, it is determined that the master cylinder and the CSV have no fault, and the process proceeds to step S205.

S205, testing a simulator loop, controlling the electric cylinder to keep the current piston state unchanged, opening the SSV, and judging the SSV clamping failure if the pressure value of the first pressure sensor P1 or the second pressure sensor P2 is larger than a ninth threshold value; otherwise, the process advances to step S206.

S206, closing the SSV, controlling the electric cylinder unit to push the piston forwards at a preset pushing speed, opening the SSV, and judging that the TSV is stuck if the pressure value of the first pressure sensor P1 or the second pressure sensor P2 is greater than a ninth threshold value; otherwise, judging that the master cylinder and the simulator brake circuit have no faults.

And the seventh threshold value, the eighth threshold value and the ninth threshold value in the test step are all data obtained by the real vehicle calibration parameters.

Fig. 5 is a flowchart illustrating a PSV fault diagnosis procedure according to an embodiment of the present disclosure. As shown in fig. 5, the PSV fault diagnosis step includes:

s301, controlling all hydraulic valves to return to an initial state and controlling the electric cylinder piston to return to an initial position when the electric cylinder loop fault diagnosis judges that the PSV is faulty;

s302, opening PSV1, closing CSV1, closing 4 ISO, controlling the electric cylinder unit to smoothly boost at a preset speed,

if the pressure value acquired by the second pressure sensor P2 reaches the target pressure within the preset time period and the piston advanced position is within the displacement range, executing step S303;

And otherwise, judging that the leakage is serious, and stopping the test.

S303, controlling the electric cylinder unit to continuously boost, wherein fault diagnosis is as follows:

if the piston advancing distance is not greater than a tenth threshold value, judging that the PSV1 is stuck;

if the piston advancing distance is between the sixth threshold value and the tenth threshold value and the P1 pressure value is not greater than the ninth threshold value, judging that the PSV1 has no fault, and entering into S304;

and if the piston advancing distance is between the sixth threshold value and the tenth threshold value and the P1 pressure value is larger than the ninth threshold value, judging that the PSV2 has leakage faults.

S304, PSV2 and CSV1 are opened, PSV1 and CSV2 are closed, the electric cylinder unit is controlled to stably boost pressure at a preset speed, if the pressure value acquired by the second pressure sensor P2 reaches the target pressure and the piston is in the forward position within the displacement range within the preset time, the step S305 is carried out, otherwise, the serious leakage fault is judged, and the test is stopped.

S305, continuing pressurizing, and performing the following fault diagnosis:

if the piston advancing distance is not greater than a tenth threshold value, judging the clamping stagnation fault of the PSV2 valve;

if the piston advancing distance is between the sixth threshold value and the tenth threshold value and the first P1 pressure is not greater than the ninth threshold value, judging that the PSV2 has no fault;

if the piston advance distance is between the sixth threshold and the tenth threshold and the first P1 pressure is greater than the ninth threshold, then a leak fault is determined for PSV 1.

The tenth threshold in the test step is real vehicle calibration data.

Fig. 6 is a flowchart illustrating a CSV fault diagnosis procedure according to an embodiment of the present disclosure. As shown in fig. 6, the steps for diagnosing the CSV fault include:

and S401, controlling all hydraulic valves and electric cylinder pistons to restore to the initial state under the condition that the fault diagnosis of the electric cylinder circuit is normal.

S402, opening PSV1, closing CSV1, closing 4 ISO valves, controlling an electric cylinder unit to stably boost pressure at a preset speed, if the pressure value acquired by a second pressure sensor P2 reaches the target pressure within a preset time and the piston advanced position is within a displacement range, entering S403, otherwise, judging that the electric cylinder unit is seriously leaked and fault, and stopping testing;

s403, continuing pressurizing, and diagnosing faults as follows:

if the piston advancing distance is not greater than the sixth threshold value and the P1 pressure value is greater than the ninth threshold value, judging CSV1 leakage fault;

if the piston advancing distance is not greater than the eleventh threshold value and the pressure value acquired by the first sensor P1 is not greater than the ninth threshold value, the CSV1, the ISO3 and the ISO4 valves have no faults, and the S404 is entered;

if the piston advancing distance is between the sixth threshold value and the eleventh threshold value and the pressure acquired by the first pressure sensor P1 is not greater than the ninth threshold value, the ISO valve has leakage fault;

S404, opening PSV2 and CSV1, closing PSV1 and CSV2, controlling an electric cylinder unit to stably boost pressure at a preset speed, and stopping testing when the pressure value acquired by the second pressure sensor P2 reaches the target pressure and the piston is in the forward position within the displacement range, and entering S405, otherwise, judging that the leakage is serious;

and S405, continuing pressurizing, and diagnosing faults as follows:

if the piston advancing distance is not greater than the sixth threshold value and the pressure value of the first pressure sensor P1 is greater than the ninth threshold value, judging CSV2 leakage fault;

if the piston advancing distance is not greater than the eleventh threshold value and the pressure value of the first pressure sensor P1 is not greater than the ninth threshold value, the CSV2, the ISO1 and ISO2 valves have no faults;

if the piston advance distance is between the sixth and eleventh thresholds and the pressure value of the first sensor P1 is not greater than the ninth threshold, the ISO valve has a leak failure.

The eleventh threshold in the testing step is real vehicle calibration data.

The above processes are all performed under the condition that the P1 and P2 pressure sensors and the piston position sensor can be normally used.

In summary, the embodiments of the present disclosure provide a hydraulic brake circuit fault diagnosis method based on an OneBox brake system, and provide a fault diagnosis method suitable for an integrated brake circuit, which has perfect judgment execution logic, and can implement comprehensive fault diagnosis of the brake circuit by using the existing pressure sensor and electric cylinder unit of the brake system.

Those of ordinary skill in the art will appreciate that: the drawing is a schematic diagram of one embodiment and the modules or flows in the drawing are not necessarily required to practice the invention.

Those of ordinary skill in the art will appreciate that: the modules in the apparatus of the embodiments may be distributed in the apparatus of the embodiments according to the description of the embodiments, or may be located in one or more apparatuses different from the present embodiments with corresponding changes. The modules of the above embodiments may be combined into one module, or may be further split into a plurality of sub-modules.

Finally, it should be noted that: the above embodiments are only for illustrating the technical solution of the present invention, and are not limiting; although the invention has been described in detail with reference to the foregoing embodiments, it will be understood by those of ordinary skill in the art that: the technical scheme described in the foregoing embodiments can be modified or some of the technical features thereof can be replaced by equivalents; such modifications and substitutions do not depart from the spirit and scope of the technical solutions of the embodiments of the present invention.

Claims (6)

1. A hydraulic brake circuit fault diagnosis method based on OneBox line control brake system is characterized by comprising the following steps of

The method comprises the steps of acquiring real vehicle calibration parameters of each device of a hydraulic brake circuit of a vehicle to be detected under normal conditions, wherein the hydraulic brake circuit comprises a hydraulic unit, a master cylinder unit, a circuit solenoid valve unit, a brake wheel cylinder, an isolation valve unit, a simulator and an electric cylinder unit, wherein the hydraulic brake circuit comprises a hydraulic pressure unit, a master cylinder unit, a circuit solenoid valve unit, a brake wheel cylinder, an isolation valve unit, a simulator and an electric cylinder unit

The hydraulic unit stores hydraulic pressure and is used for communicating the simulator, the main cylinder unit and the electric cylinder unit, and comprises a liquid storage tank and a hydraulic pipeline;

the master cylinder unit comprises a master cylinder, a pedal rod, a displacement sensor, a test valve TSV and a first pressure sensor P1, wherein the master cylinder is communicated with the liquid storage tank through the hydraulic unit, the test valve TSV is arranged between the master cylinder unit and the liquid storage tank, the pedal rod is arranged on the master cylinder, the displacement sensor is arranged on the master cylinder and used for detecting the braking displacement of the pedal rod, and the first pressure sensor P1 is arranged on the master cylinder;

the loop solenoid valve unit comprises eight solenoid valves, wherein the eight solenoid valves comprise four pressure increasing solenoid valves ISO1, ISO2, ISO3, ISO4 and four pressure reducing solenoid valves Dump1, dump2, dump3, dump4, ISO4 and Dump4 are arranged in series to form a first passage, ISO3 and Dump3 are arranged in series to form a second passage, ISO2 and Dump2 are arranged in series to form a third passage, ISO1 and Dump1 are arranged in series to form a fourth passage, the brake wheel cylinder comprises four wheel cylinders, each wheel cylinder is respectively connected with one passage, the first passage is connected with the second passage in parallel, the third passage is connected with the fourth passage in parallel, and the four passages are communicated with the hydraulic unit to form a loop;

The isolation valve unit comprises a first master cylinder isolation valve CSV1, a second master cylinder isolation valve CSV2, a first electric cylinder isolation valve PSV1 and a second electric cylinder isolation valve PSV2, wherein the first master cylinder isolation valve CSV1 is communicated with a master cylinder and one end of a first passage which is parallel to a second passage through a hydraulic pipeline, the second master cylinder isolation valve CSV2 is communicated with the master cylinder and one end of a third passage which is parallel to a fourth passage through the hydraulic pipeline, the first electric cylinder isolation valve PSV2 is communicated with an electric cylinder and one end of the first passage which is parallel to the second passage through the hydraulic pipeline, and the second electric cylinder isolation valve PSV2 is communicated with the electric cylinder and one end of the third passage which is parallel to the fourth passage through the hydraulic pipeline;

one end of the simulator is communicated with the liquid storage tank through a hydraulic pipeline, and the other end of the simulator is connected with the solenoid valve SSV through the hydraulic pipeline and is communicated with the master cylinder;

the electric cylinder unit comprises an electric cylinder, a piston, a motor, a pressure relief valve PRV and a second pressure sensor P2, wherein the motor drives the piston to move to change the pressure of the electric cylinder;

the electric cylinder, the piston, the first electric cylinder isolation valve PSV1, the second electric cylinder isolation valve PSV2, the second pressure sensor P2, the pressure relief valve PRV and a hydraulic pipeline which are communicated form an electric cylinder loop; the first master cylinder isolation valve CSV1, the second master cylinder isolation valve CSV2, the electromagnetic valve SSV, the test valve TSV, the simulator, the master cylinder and the first pressure sensor P1 form a master cylinder and simulator brake loop;

The real vehicle calibration parameters comprise a pressure value range of a first pressure sensor P1, a pressure value range P2 of a second pressure sensor, a displacement range of a piston and a range of a deviation value of a brake loop liquid volume;

in a preset time, controlling the electric cylinder piston to move to an initial position, controlling the PSV1, the PSV2, the SSV, the PRV and the Dump1, the Dump2, the Dump3 and the Dump4 to be closed, controlling the CSV1, the CSV2, the TSV, the ISO1, the ISO2, the ISO3 and the ISO4 to be opened, controlling the electric cylinder unit to boost pressure, comparing an actual parameter with a real vehicle calibration parameter, determining the fault of a hydraulic braking loop according to the comparison result of the actual parameter and the real vehicle calibration parameter, firstly performing fault diagnosis on the electric cylinder loop,

if the electric cylinder loop detects that the non-PSV fault exists, determining a fault position and a fault type;

if the electric cylinder loop detects that PSV faults exist, PSV fault diagnosis is carried out, and a fault valve and a fault type are determined;

otherwise, the master cylinder and the simulator brake circuit are subjected to fault diagnosis,

if the master cylinder and the simulator braking loop have faults, determining a specific fault valve and a specific fault type;

otherwise, diagnosing the CSV fault and determining the fault condition of the CSV valve;

And obtaining a fault diagnosis result of the hydraulic brake circuit of the vehicle to be detected.

2. The method of claim 1, wherein the step of diagnosing the failure of the electric cylinder circuit comprises:

s101, controlling the electric cylinder unit to stably boost pressure at a preset speed, if the pressure value acquired by the second pressure sensor P2 reaches a target pressure value within a preset time and the piston advancing distance is within a displacement range, continuing the test, otherwise, judging that the electric cylinder unit is a serious leakage fault, and stopping the test;

s102, controlling the electric cylinder unit to continuously boost for 1S, calculating the piston advancing distance and the liquid volume deviation of the electric cylinder circuit in the beginning 500ms, and performing the following fault diagnosis according to the calculation result after 500 ms:

if the piston advancing distance is not greater than the first threshold value and the liquid volume deviation amount of the electric cylinder loop is not greater than the second threshold value, judging that the electric cylinder loop has no fault, and entering a master cylinder and a simulator brake loop for diagnosis;

if the piston advancing distance is larger than the first threshold value and the liquid volume deviation amount of the electric cylinder loop is not larger than the second threshold value, judging that PSV or PRV leaks and fails, and entering step S103;

if the liquid volume deviation amount of the electric cylinder loop is larger than the second threshold value and not larger than the third threshold value, judging that the PSV fails;

If the liquid volume deviation amount of the electric cylinder loop is larger than a third threshold value, judging that the PRV is in fault;

s103, controlling the piston to return to the initial position, closing the 4 ISO valves, CSV1 and CSV2, if the piston returns to the initial position within a preset time period, entering S104, otherwise, judging the clamping failure of the piston of the electric cylinder, and stopping the test;

s104, controlling the electric cylinder unit to stably boost pressure at a preset speed, if the pressure value acquired by the first pressure sensor P1 reaches the target pressure within a preset time, and the piston advance position is within a displacement range, entering a step S105, otherwise, judging that the PRV leaks;

s105, continuing to boost for 1S, calculating the piston advance distance and the liquid volume deviation amount of the electric cylinder circuit in the beginning 500ms, and performing the following fault diagnosis according to the calculation result after 500 ms:

if the piston advancing distance is between the fourth threshold value and the sixth threshold value and the liquid volume deviation is not larger than the fifth threshold value, judging that the PRV has no fault, and entering a master cylinder and simulator brake circuit for diagnosis;

if the piston advancing distance is not greater than the fourth threshold value and the liquid volume deviation is not greater than the fifth threshold value, judging that the PSV fails to open;

If the piston advancing distance is not greater than the sixth threshold value and the liquid volume deviation amount is greater than the fifth threshold value, judging that the PRV is in fault;

and if the piston advancing distance is larger than the sixth threshold value, judging that the PRV is in fault.

3. The method of claim 2, wherein the amount of liquid volume deviation of the electric cylinder circuit is calculated according to the steps of:

and obtaining a liquid volume change value of the brake circuit under normal conditions according to a brake circuit PV curve tested by the real vehicle, and comparing the liquid volume change value with a hydraulic cylinder volume change value caused by piston movement to obtain a deviation value of the liquid volume of the brake circuit.

4. The method of claim 1, wherein the step of diagnosing faults in the master cylinder and the simulator brake circuits, and determining specific fault valves and fault types if faults exist in the master cylinder and the simulator brake circuits, comprises:

s201, under the condition that an electric cylinder loop is free from faults, controlling all hydraulic valves and pistons to restore to an initial state;

s202, opening a PSV1, closing TSV, closing CSV2, controlling an electric cylinder unit to boost pressure with a preset fixed boosting gradient, and entering S203 if the pressure value acquired by a first pressure sensor reaches the target pressure within a preset time and the piston advancing distance is within a displacement range; otherwise, judging that the master cylinder and the simulator brake loop have serious leakage faults, and stopping the test;

S203, controlling the electric cylinder unit to decompress with a preset fixed depressurization gradient, and if the pressure value acquired by the first pressure sensor reaches a depressurization target pressure value within a preset time and the piston advancing distance is within a displacement range, entering into a step S204; otherwise, judging that the brake loop has serious leakage fault, and stopping the test;

s204, maintaining the current pressure value for 1S, entering a pressure maintaining stage, and if the pressure value of the first pressure sensor P1 is not greater than a seventh threshold value and the piston movement speed is not greater than an eighth threshold value, judging that the piston of the auxiliary cavity of the master cylinder in the loop is stuck or the CSV1 is not opened, and stopping the test; if the piston advancing distance is larger than a seventh threshold value or the piston moving speed is larger than an eighth threshold value, judging that the loop has serious leakage fault, and stopping the test; if the pressure value of the first pressure sensor P1 is higher than the seventh threshold value and no serious leakage fault exists, judging that the main cylinder and the CSV have no faults, and entering S205;

s205, testing a simulator loop, controlling the electric cylinder to keep the current piston state unchanged, opening the SSV, and judging the SSV clamping failure if the pressure value of the first pressure sensor P1 or the second pressure sensor P2 is larger than a ninth threshold value; otherwise, enter S206 step;

S206, closing the SSV, controlling the electric cylinder unit to push the piston forwards at a preset pushing speed, opening the SSV, and judging that the TSV is stuck if the pressure value of the first pressure sensor P1 or the second pressure sensor P2 is greater than a ninth threshold value; otherwise, judging that the master cylinder and the simulator brake circuit have no faults.

5. The method of claim 1, wherein the step of performing a PSV fault diagnosis if the electric cylinder circuit detects the presence of a PSV fault, determining a faulty valve and a fault type comprises:

s301, controlling all hydraulic valves to return to an initial state and controlling the electric cylinder piston to return to an initial position when the electric cylinder loop fault diagnosis judges that the PSV is faulty;

s302, opening PSV1, closing CSV1, closing 4 ISO, controlling the electric cylinder unit to smoothly boost at a preset speed,

if the pressure value acquired by the second pressure sensor P2 reaches the target pressure within the preset time period and the piston advanced position is within the displacement range, executing step S303;

otherwise, judging that the leakage is serious, and stopping the test;

s303, controlling the electric cylinder unit to continuously boost, wherein fault diagnosis is as follows:

if the piston advancing distance is not greater than a tenth threshold value, judging that the PSV1 is stuck;

If the piston advancing distance is between the sixth threshold value and the tenth threshold value and the P1 pressure value is not greater than the ninth threshold value, judging that the PSV1 has no fault, and entering into S304;

if the piston advancing distance is between the sixth threshold value and the tenth threshold value and the P1 pressure value is larger than the ninth threshold value, judging that the PSV2 has leakage faults;

s304, opening PSV2 and CSV1, closing PSV1 and CSV2, controlling the electric cylinder unit to stably boost pressure at a preset speed, and if the pressure value acquired by the second pressure sensor P2 reaches the target pressure and the piston is in the forward position within the displacement range within a preset time, entering S305, otherwise, judging serious leakage fault, and stopping the test;

s305, continuing pressurizing, and performing the following fault diagnosis:

if the piston advancing distance is not greater than a tenth threshold value, judging the clamping stagnation fault of the PSV2 valve;

if the piston advancing distance is between the sixth threshold value and the tenth threshold value and the first P1 pressure is not greater than the ninth threshold value, judging that the PSV2 has no fault;

if the piston advance distance is between the sixth threshold and the tenth threshold and the first P1 pressure is greater than the ninth threshold, then a leak fault is determined for PSV 1.

6. The method of claim 1, wherein the step of diagnosing a CSV fault and determining a fault condition of the CSV valve comprises:

S401, under the condition that the fault diagnosis of the electric cylinder loop is normal, controlling all hydraulic valves and electric cylinder pistons to restore to an initial state;

s402, opening PSV1, closing CSV1, closing 4 ISO valves, controlling an electric cylinder unit to stably boost pressure at a preset speed, if the pressure value acquired by a second pressure sensor P2 reaches the target pressure within a preset time and the piston advanced position is within a displacement range, entering S403, otherwise, judging that the electric cylinder unit is seriously leaked and fault, and stopping testing;

s403, continuing pressurizing, and diagnosing faults as follows:

if the piston advancing distance is not greater than the sixth threshold value and the P1 pressure value is greater than the ninth threshold value, judging CSV1 leakage fault;

if the piston advancing distance is not greater than the eleventh threshold value and the pressure value acquired by the first sensor P1 is not greater than the ninth threshold value, the CSV1, the ISO3 and the ISO4 valves have no faults, and the S404 is entered;

if the piston advancing distance is between the sixth threshold value and the eleventh threshold value and the pressure acquired by the first pressure sensor P1 is not greater than the ninth threshold value, the ISO valve has leakage fault;

s404, opening PSV2 and CSV1, closing PSV1 and CSV2, controlling an electric cylinder unit to stably boost pressure at a preset speed, and stopping testing when the pressure value acquired by the second pressure sensor P2 reaches the target pressure and the piston is in the forward position within the displacement range, and entering S405, otherwise, judging that the leakage is serious;

And S405, continuing pressurizing, and diagnosing faults as follows:

if the piston advancing distance is not greater than the sixth threshold value and the pressure value of the first pressure sensor P1 is greater than the ninth threshold value, judging CSV2 leakage fault;

if the piston advancing distance is not greater than the eleventh threshold value and the pressure value of the first pressure sensor P1 is not greater than the ninth threshold value, the CSV2, the ISO1 and ISO2 valves have no faults;

if the piston advance distance is between the sixth and eleventh thresholds and the pressure value of the first sensor P1 is not greater than the ninth threshold, the ISO valve has a leak failure.