An information fusion-based hydraulic cylinder leakage fault diagnosis experimental system and method

Abstract

The present application relates to the technical field of fault diagnosis, in particular to a hydraulic cylinder leakage fault diagnosis experimental system and method based on information fusion, through analyzing the structural characteristics of a typical hydraulic cylinder, four typical leakage models are analyzed mathematically, a valve-controlled cylinder model is built, leakage simulation verification is carried out, the key factors affecting the leakage of the hydraulic cylinder are determined, for different fault factors, dynamic and static experiments are carried out, offline detection and online monitoring experiments are carried out, and the leakage factors under different working conditions are verified, on the basis of not disassembling the original system, by analyzing the characteristic data of the system, the fault diagnosis of the hydraulic cylinder leakage can be realized, the fault diagnosis is more intelligent, simple to operate and high in reliability.

Description

Technical Field

[0001] This invention relates to the field of fault diagnosis methods, specifically to an experimental system and method for diagnosing hydraulic cylinder leakage faults based on information fusion. Background Technology

[0002] As the core actuator of a hydraulic system, the reliability and stability of the hydraulic cylinder are crucial for the stable operation of the hydraulic system. Hydraulic oil leakage is one of the most common failure modes of hydraulic cylinders, which can be divided into two types according to the type of leakage: internal leakage and external leakage. External leakage refers to hydraulic oil seeping into the external environment through the gaps in the hydraulic components. Its main characteristic is that it can be directly observed, and the solution is relatively simple. Internal leakage refers to oil leakage that occurs inside the system. Under the action of pressure difference, it starts from the high-pressure chamber, flows to the low-pressure chamber through the gap between the piston and the cylinder. Because it occurs inside the system, this fault has the characteristic of being hidden and cannot be determined by direct observation.

[0003] Besides causing environmental pollution and wasting hydraulic oil, the most significant consequence of hydraulic cylinder leakage is its impact on cylinder performance. Severe leakage can lead to insufficient power, creeping, and vibration in the hydraulic cylinder. Traditional methods for diagnosing hydraulic cylinder leakage have limitations, such as requiring machine shutdown for testing or being susceptible to pressure fluctuations. These methods fail to meet the real-time monitoring needs of current industrial automation and cannot provide early warnings of leakage faults, thus hindering timely prevention and elimination of leakage faults. Therefore, this invention proposes an experimental system and method for diagnosing hydraulic cylinder leakage faults based on information fusion. Summary of the Invention

[0004] To address the technical problems existing in the prior art, the present invention provides an experimental system and method for diagnosing hydraulic cylinder leakage faults based on information fusion.

[0005] To solve the above-mentioned technical problems, the present invention provides the following technical solution: an experimental system and method for diagnosing hydraulic cylinder leakage faults based on information fusion. The experimental system includes a hydraulic station, an experimental operating platform, a power transmission channel, and a PC control box. The controller of the PC control box is connected to the experimental operating platform to control and monitor the various components of the system. The hydraulic station includes a main power source and an auxiliary power source. The power transmission channel includes a main oil circuit, a first oil circuit, a second oil circuit, a third oil circuit, a fourth oil circuit, and a return oil circuit. The main power source and the auxiliary power source respectively collect oil from the main oil circuit, the second oil circuit, and the third oil circuit and input it into the inlet of the servo valve. The servo valve is an independent valve body. The servo valve body is provided with an inlet (P), a return oil port (T), and power output ports (A, B). The hydraulic oil enters the two chambers of the hydraulic cylinder under test through the power output ports A and B.

[0006] Preferably, the main power source includes an oil tank and a variable pump, the inlet of the variable pump is connected in series with the outlet of the oil filter, the inlet of the oil filter is connected with the outlet of the oil tank, and the oil tank is equipped with a level gauge, a thermometer and an air filter.

[0007] The auxiliary power source includes an accumulator assembly and a metering pump. The outlet of the metering pump is connected to the main oil circuit, and a first check valve, a first shut-off valve, and a pressure reducing valve are connected in series on the main oil circuit.

[0008] Preferably, a pilot-operated relief valve and a first pressure gauge are connected in parallel between the first check valve and the outlet of the variable pump on the main oil line, and a first quick-connect coupling is provided on the first oil line connected to the first pressure gauge.

[0009] A metering pump is connected in parallel on the second oil line connected to the outlet of the first shut-off valve. A second check valve and a second shut-off valve are connected in series on the second oil line branch connected to the metering pump. A first direct-acting relief valve is connected in parallel to the second check valve and the second shut-off valve.

[0010] An accumulator assembly is connected to the third oil line connected to the outlet of the first shut-off valve. The accumulator assembly consists of two or fewer accumulators connected in parallel. A third shut-off valve and a fourth shut-off valve are connected in series on the branch connecting each independent accumulator.

[0011] A second pressure gauge is connected in parallel to the fourth oil line connected to the outlet of the first shut-off valve, and a second quick-connect fitting is connected in series to the fourth oil line connected to the second pressure gauge.

[0012] Preferably, the experimental operating platform includes a hydraulic cylinder under test and a servo valve. The variable pump is connected to the oil port P of the servo valve through the main oil circuit. The oil port T of the servo valve is connected to the oil tank through the return oil circuit. A second direct-acting relief valve is connected in series on the return oil circuit. The oil port A of the servo valve is connected in series with a first speed control valve and the rodless chamber of the hydraulic cylinder under test. The oil port B of the servo valve is connected in series with a second speed control valve and the rod chamber of the hydraulic cylinder under test.

[0013] A first pressure sensor is connected in parallel on the oil inlet line connecting the first speed regulating valve and the rodless chamber of the hydraulic cylinder under test. A third check valve is connected in series on the branch oil line connected to the first pressure sensor. A second pressure sensor is connected in parallel on the oil return line connecting the second speed regulating valve and the rod chamber of the hydraulic cylinder under test. A fourth check valve is connected in series on the branch oil line connected to the second pressure sensor. The rod chamber and rodless chamber of the hydraulic cylinder under test are connected in series through an external oil circuit. The switch of the series oil circuit is controlled by a first ball valve and a second ball valve. An external flow sensor is connected between the first ball valve and the second ball valve. The oil passing through the flow sensor returns directly to the oil tank. The hydraulic cylinder under test is equipped with a displacement sensor to monitor the piston rod displacement.

[0014] An experimental method for diagnosing hydraulic cylinder leakage faults based on information fusion, the experimental method specifically includes the following steps:

[0015] S1. Collect characteristic data of typical hydraulic cylinders and model the valve-controlled cylinder using Amesim simulation software. The main components of the system include a variable pump, a three-position four-way servo valve, and a single-acting piston cylinder. Conduct software simulation experiments on leakage faults and preliminarily identify the key factors affecting hydraulic cylinder leakage.

[0016] S2. Based on the key factors obtained in step S1, distinguish between offline and online situations, and then conduct dynamic and static experiments respectively. In the offline state, the detection of faulty hydraulic cylinders is carried out on the test bench, and the individual experimental research is conducted on the faulty components. The online experiment is to monitor the status of hydraulic cylinders under actual working conditions.

[0017] In both offline and online states, static experimental performance parameters include the output force of the experimental cylinder under a specific load, the displacement accuracy of the experimental cylinder under a given displacement, and the leakage of the experimental cylinder; dynamic experimental performance parameters include the response speed of the experimental cylinder to input commands and the operational stability under sudden load changes. Based on offline and online experimental samples, fault diagnosis of the hydraulic cylinder is completed.

[0018] Preferably, in step S1, the data collected on the hydraulic cylinder characteristics includes the structural dimensions of the hydraulic cylinder and the pressure in both chambers of the hydraulic cylinder.

[0019] Preferably, in step S1, the leakage mathematical model derived from the structural analysis of the hydraulic cylinder is as follows:

[0020] ;

[0021] ;

[0022] ;

[0023] ;

[0024] In the formula, This is a leak model of a gap between two fixed parallel plates. This is a leak model of a gap between two parallel flat plates with relative motion. For annular gap leakage model, For orifice leakage model, The pressure difference between the two chambers The oil pressure in the leakage chamber. The width of the gap. For the gap thickness, The length of the gap. For fluid dynamic viscosity, The relative velocity of the parallel plates. For the eccentric ratio, The width of the gap between the piston and the cylinder. The diameter of the hydraulic cylinder piston. The dynamic viscosity of the oil. The area of ​​the leakage orifice. This represents the density of the oil.

[0025] Preferably, in step S1, for different leakage mathematical models, the impact of different leakage conditions on the operation of the valve-controlled cylinder model is studied to provide a reference for the determination of key factors, and finally the relationship curve between key factors and leakage is fitted.

[0026] Preferably, in step S2, the offline testing experiment involves installing the faulty hydraulic cylinder on a testing platform and testing the faulty cylinder at the component level. The control variables are the structural parameters, pressure, flow rate, oil temperature, and system gain of the hydraulic cylinder, and the result variable is the leakage amount.

[0027] Preferably, the control variable of the online monitoring experiment is the leakage of the hydraulic cylinder, and the result variables are pressure, displacement, static and dynamic performance. The fault sample parameters obtained from the experiment are used to establish a sample library and are uniformly stored in the fault sample library on the PC.

[0028] Compared with the prior art, the beneficial effects of the present invention are as follows:

[0029] 1. This invention establishes a multi-dimensional correlation database containing various information such as oil viscosity, piston rod displacement, hydraulic cylinder pressure status, temperature, and flow rate. This database is stored and retrieved via a PC, allowing for real-time monitoring of system operation data. Based on abnormal information, it predicts hydraulic cylinder leakage faults, which is of great significance for timely diagnosis and elimination of leakage faults. This is crucial for efficient operation of engineering production, equipment health, and cost savings. It overcomes the shortcomings of traditional fault diagnosis methods, such as low automation, high labor costs, and time-consuming testing, and achieves intelligent and automated fault diagnosis of hydraulic cylinders.

[0030] 2. This invention analyzes and simulates the leakage factors of hydraulic cylinders to determine the fault performance of hydraulic cylinders under different fault conditions. It analyzes the impact of different degrees of faults on system operation under offline and online conditions, which can ensure accurate judgment of the fault type and degree of hydraulic cylinders without disassembling them. Through real-time monitoring and control of the leakage amount, system pressure and oil temperature of hydraulic cylinders on the PC, early warning of hydraulic cylinder faults can be achieved and they can be quickly eliminated. It is applicable to hydraulic cylinder fault diagnosis under both offline and online conditions. Attached Figure Description

[0031] Figure 1 This is a schematic diagram of the simulation model principle of the present invention;

[0032] Figure 2 This is a schematic diagram of the invention process of the present invention;

[0033] Figure 3 This is a top view of the experimental system of the present invention;

[0034] Figure 4 This is a schematic diagram showing the relationship between the key factors of this invention and leakage.

[0035] Figure 5 This is a three-dimensional structural diagram of the experimental system of the present invention.

[0036] The numbers in the diagram represent:

[0037] 1. Variable displacement pump; 2. Motor; 3. Fixed displacement pump; 4. Oil tank; 5. Thermometer; 6. Air filter; 7. Level gauge; 8. Oil filter; 9. First direct-acting relief valve; 10. Second check valve; 11. Pilot-operated relief valve; 12. First quick-connect coupling; 13. First pressure gauge; 14. First check valve; 15. First shut-off valve; 16. Second shut-off valve; 17. Second quick-connect coupling; 18. Second pressure gauge; 19. Third shut-off valve; 20. Fourth shut-off valve; 21. Accumulator assembly; 22. PC control box; 23. Pressure reducing valve; 24. Second direct-acting relief valve; 25. Servo valve; 26. Second speed control valve; 27. First speed control valve; 28. Third check valve; 29. ​​Fourth check valve; 30. Flow sensor; 31. First ball valve; 32. Second ball valve; 33. First pressure sensor; 34. Second pressure sensor; 35. Hydraulic cylinder under test; 36. Displacement sensor. Detailed Implementation

[0038] The present invention will be further described below with reference to the accompanying drawings and embodiments, which illustrate the above and other technical features and advantages of the present invention. However, the following embodiments are merely preferred embodiments of the present invention and are not exhaustive.

[0039] Example:

[0040] like Figure 1-5As shown, this invention provides an experimental system for diagnosing hydraulic cylinder leakage faults based on information fusion. The experimental system includes a hydraulic station, an experimental operating platform, a power transmission channel, and a PC control box 22. The controller of the PC control box 22 is connected to the experimental operating platform to control and monitor the various components of the system. The hydraulic station includes a main power source and an auxiliary power source. The power transmission channel includes a main oil circuit, a first oil circuit, a second oil circuit, a third oil circuit, a fourth oil circuit, and a return oil circuit (the return oil circuit is the oil circuit between the servo valve return port (T) and the oil tank). The main power source and the auxiliary power source respectively collect oil from the main oil circuit, the second oil circuit, and the third oil circuit and input it into the inlet of the servo valve 25. The servo valve is an independent valve body, and the valve body of the servo valve is provided with an inlet port (P), a return port (T), and power output ports (A, B). The hydraulic oil enters the two chambers of the hydraulic cylinder under test through the power output ports A and B. Figure 1 As shown in the diagram, the red line is the main oil line, the magenta line is the first oil line, the blue line is the second oil line, the green line is the third oil line, and the yellow line is the fourth oil line.

[0041] In this embodiment, the main power source includes an oil tank 4 and a variable pump 1. The inlet of the variable pump 1 is connected in series with the outlet of the oil filter 8. The inlet of the oil filter 8 is connected with the outlet of the oil tank 4. The oil tank 4 is equipped with a level gauge 7, a thermometer 5 and an air filter 6.

[0042] The auxiliary power source includes an accumulator assembly 21 and a fixed displacement pump 3. The outlet of the fixed displacement pump 3 is connected to the main oil circuit. A first check valve 14 and a first shut-off valve 15 are connected in series on the main oil circuit. The outlet of the first shut-off valve 15 is connected to the main oil circuit and is connected in series with a pressure reducing valve 23.

[0043] In this embodiment, a pilot-operated relief valve 11 and a first pressure gauge 13 are connected in parallel between the first check valve 14 and the outlet of the metering pump 3 on the main oil line, and a first quick-connect fitting 12 is provided on the first oil line connected to the first pressure gauge 13.

[0044] A metering pump 3 is connected in parallel on the second oil line connected to the outlet of the first shut-off valve 15. A second check valve 10 and a second shut-off valve 16 are connected in series on the second oil line branch connected to the metering pump 3. A first direct-acting relief valve 9 is connected in parallel between the second check valve 10 and the second shut-off valve 16.

[0045] An accumulator assembly 21 is connected to the third oil line connected to the outlet of the first shut-off valve 15. The accumulator assembly 21 is composed of two or fewer accumulators connected in parallel. A third shut-off valve 19 and a fourth shut-off valve 20 are connected in series on the branch connecting each independent accumulator.

[0046] A second pressure gauge 18 is connected in parallel to the fourth oil line connected to the outlet of the first shut-off valve 15, and a second quick-connect fitting 17 is connected in series to the fourth oil line connected to the second pressure gauge 18.

[0047] In this embodiment, the experimental operating table includes the hydraulic cylinder 35 under test and the servo valve 25. The variable pump 1 is connected to the oil port P of the servo valve 25 through the main oil circuit. The oil port T of the servo valve 25 is connected to the oil tank 4 through the return oil circuit. A second direct-acting relief valve 24 is connected in series on the return oil circuit. The oil port A of the servo valve 25 is connected in series with the first speed control valve 27 and the rodless chamber of the hydraulic cylinder 35 under test. The oil port B of the servo valve 25 is connected in series with the second speed control valve 26 and the rod chamber of the hydraulic cylinder 35 under test.

[0048] A first pressure sensor 33 is connected in parallel on the oil inlet line connecting the first speed regulating valve 27 and the rodless chamber of the hydraulic cylinder 35 under test. A third check valve 28 is connected in series on the branch oil line connecting the first pressure sensor 33. A second pressure sensor 34 is connected in parallel on the oil return line connecting the second speed regulating valve 26 and the rod chamber of the hydraulic cylinder 35 under test. A fourth check valve 29 is connected in series on the branch oil line connecting the second pressure sensor 34. The rod chamber and rodless chamber of the hydraulic cylinder 35 under test are connected in series through an external oil circuit. The switch of the series oil circuit is connected in series through the first ball valve 31 and the second ball valve 32. An external flow sensor 30 is connected between the first ball valve 31 and the second ball valve 32. The oil passing through the flow sensor 30 returns directly to the oil tank 4. The hydraulic cylinder 35 under test is equipped with a displacement sensor 36 to monitor the piston rod displacement.

[0049] Working principle: When performing leakage fault diagnosis, the shut-off valve 15 is opened, and the variable pump 1 and fixed displacement pump 3 are started to supply oil to the hydraulic cylinder leakage fault diagnosis experimental system. The hydraulic cylinder test is started. The pilot-operated relief valve 11, pressure reducing valve 23, and second direct-acting relief valve 24 adjust the oil inlet and outlet pressure of the test system. The first speed control valve 27 and the second speed control valve 26 adjust the system flow rate. The first pressure sensor 33 and the second pressure sensor 34 monitor the pressure in the two chambers of the hydraulic cylinder under test in real time. The displacement sensor 36 monitors the piston rod displacement of the hydraulic cylinder. The servo valve 25 is energized in the right position to control the extension of the hydraulic cylinder piston rod. The piston rod moves to its final position. When the stroke ends, the first ball valve 31 is closed and the second ball valve 32 is opened. The flow sensor 30 monitors the internal leakage from the rod chamber to the rodless chamber of the hydraulic cylinder. The left position of the servo valve 25 is energized, controlling the retraction of the hydraulic cylinder piston rod. After the piston stroke ends, the second ball valve 32 is closed and the first ball valve 31 is opened. The flow sensor 30 monitors the internal leakage from the rodless chamber to the rod chamber. The return oil pressure of the oil port T of the servo valve 25 is regulated by the second direct-acting relief valve 24 to monitor the internal leakage of the oil. When the hydraulic cylinder piston stroke ends, the internally leaked oil flows through the flow sensor through the corresponding ball valve, thereby realizing the monitoring of the internal leakage of the oil.

[0050] An experimental method for diagnosing hydraulic cylinder leakage faults based on information fusion, the experimental method specifically includes the following steps:

[0051] S1. The specific parameters of a typical hydraulic cylinder during operation are collected by sensors and instruments on the valve-controlled cylinder model. The valve-controlled cylinder model is modeled using Amesim simulation software. The main components of the valve-controlled cylinder model include a variable pump, a three-position four-way servo valve, and a single-acting piston cylinder. Software simulation experiments on leakage faults are conducted. The simulation experiment process refers to the above working principle. The experimental variables are oil pressure, load, and temperature, and the dependent variable is the leakage amount. The key factors affecting hydraulic cylinder leakage are preliminarily identified.

[0052] S2. Based on the key factors obtained in step S1, distinguish between offline and online situations, and then conduct dynamic and static experiments respectively. In the offline state, the detection of faulty hydraulic cylinders is carried out on the test bench, and separate experimental studies are conducted on the faulty components. The online experiment is to monitor the status of hydraulic cylinders under actual working conditions.

[0053] In both offline and online states, static experimental performance parameters include the output force of the experimental cylinder under a specific load, the displacement accuracy of the experimental cylinder under a given displacement, and the leakage of the experimental cylinder; dynamic experimental performance parameters include the response speed of the experimental cylinder to input commands and the operational stability under sudden load changes. Based on offline and online experimental samples, fault diagnosis of the hydraulic cylinder is completed.

[0054] Therefore, valve-controlled cylinder models are established for different hydraulic cylinders under test, leakage detection is performed, and the cause of failure is finally determined.

[0055] In this embodiment, the data collected in step S1 includes the structural dimensions of the hydraulic cylinder and the pressure in both chambers of the hydraulic cylinder.

[0056] In this embodiment, in step S1, the leakage mathematical model derived from the structural analysis of the hydraulic cylinder is as follows:

[0057] ;

[0058] ;

[0059] ;

[0060] ;

[0061] In the formula, This is a leak model of a gap between two fixed parallel plates. This is a leak model of a gap between two parallel flat plates with relative motion. For annular gap leakage model, For orifice leakage model, The pressure difference between the two chambers The oil pressure in the leakage chamber. The width of the gap. For the gap thickness, The length of the gap. For fluid dynamic viscosity, The relative velocity of the parallel plates. For the eccentric ratio, The width of the gap between the piston and the cylinder. The diameter of the hydraulic cylinder piston. The dynamic viscosity of the oil. The area of ​​the leakage orifice. This represents the density of the oil.

[0062] In this embodiment, step S1 studies the impact of different leakage scenarios on the operation of the valve-controlled cylinder model for different leakage mathematical models, providing a reference for determining key factors. Finally, the relationship curve between key factors and leakage is fitted, such as... Figure 4 As shown, the numerical relationship between the pressure difference between the two chambers of the hydraulic cylinder and the leakage amount is displayed under different leakage coefficients (i.e. different leakage amounts). This yields the key failure factor: the pressure difference between the two chambers of the hydraulic cylinder, and verifies the feasibility of internal leakage fault diagnosis by monitoring the pressure difference between the two chambers of the hydraulic cylinder.

[0063] In this embodiment, during the offline testing experiment, the faulty hydraulic cylinder is installed on the testing platform and tested at the component level. The control variables are the structural parameters, pressure, flow rate, oil temperature and system gain of the hydraulic cylinder, and the result variable is the leakage amount.

[0064] The control variable in the online monitoring experiment was the leakage of the hydraulic cylinder, and the result variables were pressure, displacement, static and dynamic performance.

[0065] The fault sample library established during the experiment includes the fault sample parameters obtained from the experiment, which are then uniformly stored in the fault sample library on the PC.

[0066] The above description is merely a preferred embodiment of the present invention and is illustrative rather than restrictive. Those skilled in the art will understand that many changes, modifications, and even equivalents can be made within the spirit and scope defined by the claims of the present invention, all of which will fall within the protection scope of the present invention.

Claims

1. An experimental system for diagnosing hydraulic cylinder leakage faults based on information fusion, characterized in that, The experimental system includes a hydraulic station, an experimental operating table, a power transmission channel, and a PC control box (22). The controller of the PC control box (22) is connected to the experimental operating table through a dedicated cable to control and monitor the various components of the system. The hydraulic station includes a main power source and an auxiliary power source. The power transmission channel includes a main oil circuit, a first oil circuit, a second oil circuit, a third oil circuit, a fourth oil circuit, and a return oil circuit. The main power source and the auxiliary power source respectively collect oil from the main oil circuit, the second oil circuit, and the third oil circuit and input it into the inlet of the servo valve (25). The valve body of the servo valve (25) is provided with an inlet, a return oil port, and a power output oil port. The hydraulic oil enters the two chambers of the hydraulic cylinder under test through the power output oil port.

2. The hydraulic cylinder leakage fault diagnosis experimental system based on information fusion as described in claim 1, characterized in that, The main power source includes an oil tank (4) and a variable pump (1). The inlet of the variable pump (1) is connected in series with the outlet of the oil filter (8). The inlet of the oil filter (8) is connected to the outlet of the oil tank (4). The oil tank (4) is equipped with a level gauge (7), a thermometer (5) and an air filter (6). The auxiliary power source includes an accumulator assembly (21) and a metering pump (3). The outlet of the metering pump (3) is connected to the main oil circuit. The main oil circuit is connected in series with a first check valve (14), a first shut-off valve (15), and a pressure reducing valve (23).

3. The hydraulic cylinder leakage fault diagnosis experimental system based on information fusion as described in claim 2, characterized in that, A pilot-operated relief valve (11) and a first pressure gauge (13) are connected in parallel between the first check valve (14) and the outlet of the variable pump (3) on the main oil line. A first quick-connect fitting (12) is provided on the first oil line connected to the first pressure gauge (13). A metering pump (3) is connected in parallel to the second oil line connected to the outlet of the first shut-off valve (15). A second check valve (10) and a second shut-off valve (16) are connected in series on the second oil line branch connected to the metering pump (3). A first direct-acting relief valve (9) is connected in parallel to the second check valve (10) and the second shut-off valve (16). An accumulator assembly (21) is connected to the third oil line connected to the outlet of the first shut-off valve (15). The accumulator assembly (21) is composed of two or fewer accumulators connected in parallel. A third shut-off valve (19) and a fourth shut-off valve (20) are connected in series on the branch connecting each independent accumulator. A second pressure gauge (18) is connected in parallel to the fourth oil line connected to the outlet of the first shut-off valve (15), and a second quick-connect fitting (17) is connected in series to the fourth oil line connected to the second pressure gauge (18).

4. The hydraulic cylinder leakage fault diagnosis experimental system based on information fusion as described in claim 1, characterized in that, The experimental operating platform includes the hydraulic cylinder under test (35) and the servo valve (25). The variable pump (1) is connected to the oil port P of the servo valve (25) through the main oil circuit. The oil port T of the servo valve (25) is connected to the oil tank (4) through the return oil circuit. A second direct-acting relief valve (24) is connected in series on the return oil circuit. The oil port A of the servo valve (25) is connected in series with the first speed control valve (27) and the rodless chamber of the hydraulic cylinder under test (35). The oil port B of the servo valve (25) is connected in series with the second speed control valve (26) and the rod chamber of the hydraulic cylinder under test (35). A first pressure sensor (33) is connected in parallel on the oil inlet line connecting the first speed regulating valve (27) and the rodless chamber of the hydraulic cylinder under test (35). A third check valve (28) is connected in series on the branch oil line connecting the first pressure sensor (33). A second pressure sensor (34) is connected in parallel on the oil return line connecting the second speed regulating valve (26) and the rod chamber of the hydraulic cylinder under test (35). A fourth check valve (29) is connected in series on the branch oil line connecting the second pressure sensor (34). The rod chamber and rodless chamber of the hydraulic cylinder under test (35) are connected in series through an external oil circuit. The switch of the series oil circuit is controlled by the first ball valve (31) and the second ball valve (32). An external flow sensor (30) is connected between the first ball valve (31) and the second ball valve (32). The oil passing through the flow sensor (30) returns directly to the oil tank (4). The hydraulic cylinder under test (35) is equipped with a displacement sensor (36) to monitor the piston rod displacement.

5. An experimental method for diagnosing hydraulic cylinder leakage faults based on information fusion, employing the hydraulic cylinder leakage fault diagnosis experimental system based on information fusion as described in any one of claims 1-4, characterized in that, The diagnostic test method specifically includes the following steps: S1. Collect characteristic data of typical hydraulic cylinders and model the valve-controlled cylinder using Amesim simulation software. The main components of the system include a variable pump, a three-position four-way servo valve, and a single-acting piston cylinder. Conduct software simulation experiments on leakage faults and preliminarily identify the key factors affecting hydraulic cylinder leakage. S2. Based on the key factors obtained in step S1, distinguish between offline and online situations, and then conduct dynamic and static experiments respectively. In the offline state, the detection of faulty hydraulic cylinders is carried out on the test bench, and the individual experimental research is conducted on the faulty components. The online experiment is to monitor the status of hydraulic cylinders under actual working conditions. In both offline and online states, static experimental performance parameters include the output force of the experimental cylinder under a specific load, the displacement accuracy of the experimental cylinder under a given displacement, and the leakage of the experimental cylinder; dynamic experimental performance parameters include the response speed of the experimental cylinder to input commands and the operational stability under sudden load changes. Based on offline and online experimental samples, fault diagnosis of the hydraulic cylinder is completed.

6. The experimental method for diagnosing hydraulic cylinder leakage faults based on information fusion as described in claim 5, characterized in that, In step S1, the data collected on the characteristics of the hydraulic cylinder includes the structural dimensions of the hydraulic cylinder and the pressure in both chambers of the hydraulic cylinder.

7. The experimental method for diagnosing hydraulic cylinder leakage faults based on information fusion as described in claim 5, characterized in that, In step S1, the leakage mathematical model derived from the structural analysis of the hydraulic cylinder is as follows: ； ； ； ； In the formula, This is a leak model of a gap between two fixed parallel plates. This is a leak model of a gap between two parallel flat plates with relative motion. For annular gap leakage model, For orifice leakage model, The pressure difference between the two chambers The oil pressure in the leakage chamber. The width of the gap. For the gap thickness, The length of the gap. For fluid dynamic viscosity, The relative velocity of the parallel plates For the eccentric ratio, The width of the gap between the piston and the cylinder. The diameter of the hydraulic cylinder piston. The dynamic viscosity of the oil. The area of ​​the leakage orifice. This represents the density of the oil.

8. The experimental method for diagnosing hydraulic cylinder leakage faults based on information fusion as described in claim 5, characterized in that, In step S1, for different leakage mathematical models, the impact of different leakage conditions on the operation of the valve-controlled cylinder model is studied to provide a reference for the determination of key factors, and finally the relationship curve between key factors and leakage is fitted.

9. The experimental method for diagnosing hydraulic cylinder leakage faults based on information fusion as described in claim 5, characterized in that, In step S2, the offline testing experiment involves installing the faulty hydraulic cylinder on a testing platform and testing the faulty cylinder at the component level. The control variables are the structural parameters, pressure, flow rate, oil temperature, and system gain of the hydraulic cylinder, and the result variable is the leakage amount.

10. The experimental method for diagnosing hydraulic cylinder leakage faults based on information fusion as described in claim 5, characterized in that, In step S2, the control variable of the online monitoring experiment is the leakage of the hydraulic cylinder, and the result variables are pressure, displacement, static and dynamic performance. The fault sample parameters obtained from the experiment are used to establish a sample library and are uniformly stored in the fault sample library on the PC.

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