A comprehensive test bench and method for performance detection and fault diagnosis of a hydraulic AGC system

Abstract

The application discloses a kind of comprehensive test bench and method of hydraulic AGC system performance detection and fault diagnosis, it is related to hydraulic AGC system performance detection technical field, including power pump assembly, servo valve, proportional overflow valve, data acquisition module, auxiliary assembly, PLC control unit and PC control end;The application provides back pressure loading mode for hydraulic cylinder using proportional overflow valve than traditional two hydraulic cylinder top loading mode is safer, more reliable, simplifies the hydraulic system.Precision determination multiple performance indicators, accurately identify complex faults, improve detection accuracy and diagnostic accuracy, through high-frequency data acquisition, real-time threshold and model comparison, using PLC control replaces manual control and with traditional relay control, improve test efficiency and safety and have the diagnostic function of detecting AGC hydraulic cylinder leakage, step response, frequency response and servo valve dynamic, static performance and the like.

Description

Technical Field

[0001] This invention relates to the field of hydraulic AGC system performance testing and fault diagnosis technology, and in particular to a comprehensive test bench and method for hydraulic AGC system performance testing and fault diagnosis. Background Technology

[0002] The AGC (Automatic Gauge Control) system automatically adjusts the distance between the rolls and regulates the pressure of the hydraulic cylinders in real time to ensure stable steel thickness during the rolling process. The accuracy and response speed of the AGC system are crucial to production stability and steel quality. Within the AGC system, the hydraulic cylinders control the dynamic adjustment of the mill roll gap; their performance and operating status directly affect the mill's stability and production efficiency. Failures in the hydraulic cylinders and servo valves will lead to inaccurate roll gap control, ultimately impacting steel quality and production efficiency.

[0003] Performance testing and fault diagnosis of AGC hydraulic cylinders and servo valves can identify potential problems early, preventing production interruptions due to equipment failure and thus improving production line stability and efficiency. Optimization and troubleshooting of hydraulic cylinder and servo valve performance ensures more precise thickness control in the rolling mill, reducing product thickness fluctuations caused by unstable control and guaranteeing steel quality and consistency. Regular inspection and preventative maintenance can prevent major failures of hydraulic cylinders and servo valves, reducing unexpected downtime and repair costs. This not only lowers equipment operating costs but also extends the service life of hydraulic cylinders and servo valves. Hydraulic system malfunctions can lead to unstable rolling mill operation and even safety accidents. Real-time monitoring and early diagnosis can promptly identify potential faults, prevent accidents, and ensure production safety.

[0004] With the development of production technology, the control of hydraulic systems is becoming increasingly complex, and the technical means for fault diagnosis of AGC hydraulic cylinders and servo valves are also constantly evolving. Modern fault diagnosis methods include those based on signal processing, data analysis, and artificial intelligence technologies, which can monitor the working status of hydraulic cylinders in real time, thereby effectively extending the service life of equipment and improving production efficiency.

[0005] Dynamic performance testing of AGC hydraulic cylinders is highly specialized and technically challenging, requiring specialized testing equipment. Therefore, most AGC hydraulic cylinder manufacturers in my country lack the capability to conduct such tests. Servo valves suffer from high failure rates and are difficult to repair, significantly impacting system stability and reliability. Therefore, there is an urgent need for a comprehensive testing platform and method for performance testing and fault diagnosis of hydraulic AGC systems. This would improve the efficiency and accuracy of performance testing and fault diagnosis for AGC hydraulic cylinders and servo valves, while reducing costs and maintenance complexity for enterprises. Summary of the Invention

[0006] This invention provides a comprehensive test bench and method for performance testing and fault diagnosis of hydraulic AGC systems, which solves the technical problems of difficulty in testing dynamic performance and low degree of automation in most AGC hydraulic cylinder and servo valve performance testing test benches on the market.

[0007] To solve the above-mentioned technical problems, the present invention provides a comprehensive test bench and method for performance testing and fault diagnosis of a hydraulic AGC system, comprising:

[0008] The power pump assembly includes an oil tank, a variable pump, a motor, a first filter, a first check valve, a first shut-off valve, an accumulator, and a pilot-operated relief valve;

[0009] The variable pump's suction port is connected to the oil tank, and its outlet is connected in series with the first filter, the first check valve, and the first shut-off valve.

[0010] The accumulator is connected in parallel with the pilot-operated relief valve at the outlet of the first shut-off valve;

[0011] The servo valve has its P port connected to the outlet of the first shut-off valve, its A port connected to the rodless chamber of the AGC hydraulic cylinder through the third shut-off valve, its B port connected to the rod chamber of the AGC hydraulic cylinder through the fourth shut-off valve, and its T port returning oil to the oil tank.

[0012] A proportional relief valve is connected in series in the rod-side chamber circuit of the AGC hydraulic cylinder and in parallel with the second check valve;

[0013] The data acquisition module includes:

[0014] The first pressure sensor is installed in the pipeline between the outlet of the first filter and the first check valve;

[0015] The second pressure sensor is installed at the accumulator inlet;

[0016] The third pressure sensor is installed at the rodless chamber inlet of the AGC hydraulic cylinder;

[0017] The fourth and fifth pressure sensors are installed at the inlet and outlet of the proportional relief valve, respectively.

[0018] The sixth pressure sensor is installed at the P port of the servo valve;

[0019] The first flow sensor and the second flow sensor are installed at ports A and B of the servo valve, respectively.

[0020] The third flow sensor is installed on the T-port return oil line of the servo valve;

[0021] The displacement sensor is fixed to the end of the piston rod of the AGC hydraulic cylinder;

[0022] The auxiliary components include an air filter, a level gauge, and a temperature sensor. The air filter is located on the top of the oil tank, the level gauge is installed on the side wall of the oil tank, and the temperature sensor is immersed in the oil in the oil tank.

[0023] The PLC control unit is electrically connected to the servo valve, proportional relief valve and motor, and receives feedback signals from the data acquisition module.

[0024] The PC control terminal communicates with the PLC control unit via Ethernet and includes a performance monitoring module and a fault diagnosis module.

[0025] In some embodiments, the power pump assembly further includes a second filter, a third check valve, a second shut-off valve, and a fifth shut-off valve;

[0026] The second filter is connected in series between the T-port return oil line of the servo valve and the oil tank;

[0027] The third check valve is connected in series between the T-port return oil line of the servo valve and the second filter;

[0028] The second shut-off valve is connected in series between the P port of the servo valve and the first shut-off valve;

[0029] The fifth shut-off valve is located on the oil return line of the oil tank.

[0030] In some embodiments, the determination logic of the fault diagnosis module includes:

[0031] Internal leakage fault: Based on the pressure difference Δp between the rodless chamber and the rod chamber detected by the third and fourth pressure sensors, the fault can be determined using the formula...

[0032]

[0033] Calculate the leakage amount; if it exceeds the threshold, trigger an alarm.

[0034] Servo valve flow abnormality: Compare the measured flow rates of the first and second flow sensors with the fitting curves of the servo valve input current. If the deviation exceeds the preset range, the valve core is determined to be worn.

[0035] In some embodiments, a first quick connector and a second quick connector are respectively provided on the branch and the connecting pipe of the servo valve's A port to the rod chamber of the AGC hydraulic cylinder, a third quick connector is provided on the connecting pipe of the rodless chamber of the AGC hydraulic cylinder to the proportional relief valve, and a fourth quick connector is provided on the branch of the connecting pipe of the proportional relief valve to the P port of the servo valve.

[0036] In some embodiments, the first quick connector and the fourth quick connector are respectively connected to a first pressure gauge and a second pressure gauge.

[0037] In some embodiments, the current signal of the proportional relief valve is programmed and output by the PC control terminal, and its opening degree is adjusted by the PLC control unit to simulate the actual working back pressure of the AGC hydraulic cylinder.

[0038] This invention also provides a method for performance testing and fault diagnosis of a hydraulic AGC system, specifically including the following steps:

[0039] S1. Performance testing and fault diagnosis of AGC hydraulic cylinders:

[0040] S101. Install the fault-free servo valve and open all shut-off valves, including the first shut-off valve, the second shut-off valve, the third shut-off valve, the fourth shut-off valve, and the fifth shut-off valve.

[0041] S102. Set the back pressure load through the proportional sequence valve and input a control signal to the servo valve to drive the AGC hydraulic cylinder;

[0042] S103. Based on the third and fourth pressure sensors, monitor the pressure difference between the two chambers of the hydraulic cylinder, and calculate the internal leakage coefficient using a fifth-order polynomial fitting model. When the threshold is exceeded, trigger a leakage fault alarm.

[0043] S104. Input step signal and sine wave signal to servo valve, collect response data through displacement sensor, and generate step response curve and frequency response bandwidth index.

[0044] S2. Servo Valve Performance Testing and Fault Diagnosis:

[0045] S201. Install a fault-free AGC hydraulic cylinder and open all shut-off valves;

[0046] S202. Adjust the proportional sequence valve to set the load pressure and input a dynamic current signal to the servo valve;

[0047] S203. Generate no-load flow characteristic curve and load flow parabola cluster through the first flow sensor and the second flow sensor. After closing the third and fourth shut-off valves, monitor the leakage of port T through the flow sensor. If the leakage exceeds the limit, trigger the servo valve leakage alarm.

[0048] S204. Based on the monitoring of the pressure drop and current relationship by the second and sixth pressure sensors, a servo valve pressure characteristic curve is generated.

[0049] In some embodiments, the fifth-order polynomial fitting model is specifically:

[0050] Q = aΔP 5 +bΔP 4 +cΔP 3 +dΔP 2 +eΔP+f

[0051] Where af is the experimental calibration coefficient, and the step response time is judged by the displacement reaching 90% of the steady state value, and the frequency response bandwidth is judged by the cutoff frequency corresponding to the amplitude attenuation of -3dB.

[0052] Compared with related technologies, the comprehensive test bench and method for performance testing and fault diagnosis of hydraulic AGC systems provided by this invention have the following beneficial effects:

[0053] This invention provides a comprehensive test bench and method for performance testing and fault diagnosis of hydraulic AGC systems. The loading method using a proportional relief valve to provide back pressure to the hydraulic cylinder is safer and more reliable than the traditional two-cylinder counter-loading method, and simplifies the hydraulic system. It accurately measures multiple performance indicators, precisely identifies complex faults, and improves detection accuracy and diagnostic precision. Through high-frequency data acquisition, it compares thresholds and models in real time, and uses PLC control to replace manual control and traditional relay control, improving testing efficiency and safety. It also has diagnostic functions for detecting faults such as internal leakage, step response, frequency response, and dynamic and static performance of servo valves in AGC hydraulic cylinders. Attached Figure Description

[0054] Figure 1 This is a hydraulic schematic diagram of the present invention;

[0055] Figure 2 This is a system control flowchart of the present invention;

[0056] Figure 3 This is a curve showing the internal leakage coefficient versus pressure difference in this invention.

[0057] Labels in the diagram: 1. Variable pump; 21. First filter; 22. Second filter; 31. First check valve; 32. Second check valve; 33. Third check valve; 41. First shut-off valve; 42. Second shut-off valve; 43. Third shut-off valve; 44. Fourth shut-off valve; 45. Fifth shut-off valve; 51. First pressure sensor; 52. Second pressure sensor; 53. Third pressure sensor; 54. Fourth pressure sensor; 55. Fifth pressure sensor; 56. Sixth pressure sensor; 6. Pilot-operated relief valve; 7. Accumulator 8. Servo valve; 91. First flow sensor; 92. Second flow sensor; 93. First flow sensor; 101. First pressure gauge; 102. Second pressure gauge; 11. AGC hydraulic cylinder; 12. Displacement sensor; 13. Proportional relief valve; 14. Current signal; 15. Temperature sensor; 16. Air filter; 17. Oil tank; 18. Level gauge; 19. Motor; 201. First quick-connect coupling; 202. Second quick-connect coupling; 203. Third quick-connect coupling; 204. Fourth quick-connect coupling. Detailed Implementation

[0058] This invention provides a comprehensive test bench and method for performance testing and fault diagnosis of hydraulic AGC systems. It integrates the static and dynamic performance testing functions of AGC hydraulic cylinders and servo valves into one device. The test is carried out according to a preset program to perform performance testing and fault diagnosis of AGC hydraulic cylinders and servo valves.

[0059] Specifically, the system includes a PC control terminal, an AGC hydraulic cylinder testing platform, and a servo valve testing platform. The PC controls the electro-hydraulic servo valve on the testing platform via a programmable logic controller (PLC), thereby controlling the movement of the AGC hydraulic cylinder. The PC control terminal displays and stores the experimental data. The testing platform performs static and dynamic performance tests on the AGC hydraulic cylinder and static performance tests on the servo valve according to the latest national testing standards. Signals from all sensors on the testing platform are transmitted to the PC via a data acquisition card.

[0060] Example 1

[0061] like Figure 1 As shown, the variable pump 1 of the power pump assembly is driven by motor 19. After drawing oil from oil tank 17, the oil is purified by first filter 21 and enters the main oil circuit through first check valve 31 and first shut-off valve 41. Accumulator 7 and pilot-operated relief valve 6 are connected in parallel to the main oil circuit. The P port of servo valve 8 is connected to the main oil circuit through second shut-off valve 42, its A port is connected to the rodless chamber of AGC hydraulic cylinder 11 through third shut-off valve 43, and its B port is connected to the rod chamber through fourth shut-off valve 44. Proportional relief valve 13 is connected in series in the rod chamber circuit and adjusts the back pressure load through current signal 14. The first pressure sensor 51, second pressure sensor 52, third pressure sensor 53, fourth pressure sensor 54, fifth pressure sensor 55, sixth pressure sensor 56 and the first flow sensor 91, second flow sensor 92, third flow sensor 93 of the data acquisition module monitor the system status in real time. Displacement sensor 12 collects the displacement signal of AGC hydraulic cylinder 11. The PC control terminal realizes closed-loop control through PLC control unit.

[0062] Example 2 (Internal Leakage Detection)

[0063] With the third shut-off valve 43 and the fourth shut-off valve 44 closed, the pressure difference Δp between the rodless chamber and the rod chamber of the AGC hydraulic cylinder 11 is monitored by the third pressure sensor 53 and the fourth pressure sensor 54. This is then combined with the flow formula:

[0064]

[0065] Calculate the internal leakage.

[0066] The fifth-order polynomial model fitted based on the experimental data is as follows:

[0067] Q = aΔP 5 +bΔP 4 +cΔP 3+dΔP 2 +eΔP+f

[0068] Where af is the experimental calibration coefficient.

[0069] The final hydraulic cylinder internal leakage fault prediction model is as follows:

[0070] y = -5 × 10 -5 ΔP 5 +0.0014ΔP 4 -0.0178ΔP 3 +0.1316ΔP 2 -0.6963ΔP+3.1713

[0071] When the leakage coefficient exceeds the threshold, a fault alarm is triggered on the PC.

[0072] Example 3 (Step Response Test)

[0073] Open the first shut-off valve 41, the second shut-off valve 42, the third shut-off valve 43, the fourth shut-off valve 44, and the fifth shut-off valve 45 to input a step signal to the servo valve 8 and adjust the back pressure of the proportional relief valve 13. The displacement sensor 12 collects the displacement signal of the AGC hydraulic cylinder 11 in real time, and the PC generates a step response curve, using the time for the displacement to reach 90% of the steady-state value as the response index.

[0074] Example 4 (Frequency Response Test)

[0075] Keep all shut-off valves open and input sinusoidal signals of different frequencies to servo valve 8. Displacement sensor 12 monitors the displacement amplitude and phase difference of AGC hydraulic cylinder 11. The PC calculates the system frequency response through Fourier transform, using the cutoff frequency corresponding to an amplitude attenuation of -3dB as the bandwidth index.

[0076] Example 5 (Internal Leakage Detection of Servo Valve)

[0077] The third shut-off valve 43 and the fourth shut-off valve 44 are closed to reduce the load flow to zero. The third flow sensor 93 monitors the leakage at the servo valve 8T port. When the leakage exceeds a preset threshold (e.g., zero-position leakage > 5% of rated flow), the PC triggers an internal leakage fault alarm for the servo valve.

[0078] Example 6 (Servo Valve Flow Characteristic Test)

[0079] Adjust the load pressure of the proportional relief valve 13 to input a dynamic current signal to the servo valve 8. The first flow sensor 91 and the second flow sensor 92 record the flow rates at ports A and B, respectively, generating an unloaded flow characteristic curve and a cluster of load flow-pressure parabolas. By comparing with the standard curve, valve core wear or jamming can be determined.

[0080] Example 7 (Servo Valve Pressure Characteristic Test)

[0081] The pilot-operated relief valve 6 is adjusted to maintain a constant oil supply pressure, and the third shut-off valve 43 and the fourth shut-off valve 44 are closed. The second pressure sensor 52 and the sixth pressure sensor 56 synchronously monitor the pressure difference between the P port and the T port of the servo valve 8, generating a pressure difference-input current relationship curve. If the deviation exceeds ±10%, the pressure characteristics are judged to be abnormal.

[0082] Working principle:

[0083] 1. Performance testing and fault diagnosis of AGC cylinders

[0084] When performing performance testing and fault diagnosis of the AGC cylinder, install the fault-free servo valve 8 and open all shut-off valves in the oil circuit. Adjust the opening pressure of the proportional relief valve 13 via the current signal 14 to provide a back pressure load to the tested AGC hydraulic cylinder 11. The specific procedure is as follows:

[0085] 1) Internal leakage detection: The pressure difference Δp between the two chambers is monitored by pressure sensor 53 (rodless chamber) and pressure sensor 54 (rod chamber), and the leakage is determined according to the formula...

[0086]

[0087] Calculate the leakage amount;

[0088] 2) Step response test: Input a step signal to the servo valve 8, and the displacement sensor 12 collects the displacement of the AGC hydraulic cylinder 11 to generate a step response curve;

[0089] 3) Frequency response test: Input a sine wave signal to the servo valve 8, and calculate the frequency response bandwidth using the amplitude and phase data of the displacement sensor 12.

[0090] 2. Performance testing and fault diagnosis of servo valves

[0091] When performing performance testing and fault diagnosis on servo valve 8, a fault-free AGC hydraulic cylinder 11 is installed, all shut-off valves are opened, and the back pressure load of the proportional relief valve 13 is adjusted via current signal 14. The specific procedure is as follows:

[0092] 1) Flow characteristic test: Input a dynamic current signal to the servo valve 8, and the flow sensor 91 (port A) and flow sensor 92 (port B) record the flow rate to generate no-load / load flow characteristic curves;

[0093] 2) Pressure characteristic test: Close the third shut-off valve 43 and the fourth shut-off valve 44, monitor the pressure difference through pressure sensor 52 (supply pressure) and pressure sensor 56 (return pressure), and generate a pressure difference-current relationship curve;

[0094] 3) Internal leakage detection: After closing the third shut-off valve 43 and the fourth shut-off valve 44, the third flow sensor 93 monitors the leakage at the servo valve 8T port. An alarm is triggered when the leakage exceeds the threshold.

Claims

1. A comprehensive test bench for performance testing and fault diagnosis of a hydraulic AGC system, characterized in that: include: The power pump assembly includes an oil tank, a variable pump, a motor, a first filter, a first check valve, a first shut-off valve, an accumulator, and a pilot-operated relief valve; The oil inlet of the variable pump is connected to the oil tank, and the outlet of the variable pump is connected in series with the first filter, the first check valve, and the first shut-off valve. The accumulator is connected in parallel with the pilot-operated relief valve at the outlet of the first shut-off valve; The servo valve has its P port connected to the outlet of the first shut-off valve, its A port connected to the rodless chamber of the AGC hydraulic cylinder through the third shut-off valve, its B port connected to the rod chamber of the AGC hydraulic cylinder through the fourth shut-off valve, and its T port returning oil to the oil tank. A proportional relief valve is connected in series in the rod-side chamber circuit of the AGC hydraulic cylinder and in parallel with the second check valve; The data acquisition module includes: The first pressure sensor is installed in the pipeline between the outlet of the first filter and the first check valve; The second pressure sensor is installed at the accumulator inlet; The third pressure sensor is installed at the rodless chamber inlet of the AGC hydraulic cylinder; The fourth and fifth pressure sensors are installed at the inlet and outlet of the proportional relief valve, respectively. The sixth pressure sensor is installed at the P port of the servo valve; The first flow sensor and the second flow sensor are installed at ports A and B of the servo valve, respectively. The third flow sensor is installed on the T-port return oil line of the servo valve; The displacement sensor is fixed to the end of the piston rod of the AGC hydraulic cylinder; The auxiliary components include an air filter, a level gauge, and a temperature sensor. The air filter is located on the top of the oil tank, the level gauge is installed on the side wall of the oil tank, and the temperature sensor is immersed in the oil in the oil tank. The PLC control unit is electrically connected to the servo valve, proportional relief valve and motor, and receives feedback signals from the data acquisition module. The PC control terminal communicates with the PLC control unit via Ethernet and includes a performance monitoring module and a fault diagnosis module. The fault diagnosis module's determination logic includes: Internal leakage fault: Based on the pressure difference Δp between the rodless chamber and the rod chamber detected by the third and fourth pressure sensors, the fault can be determined using the formula... ； Calculate the leakage amount; if it exceeds the threshold, trigger an alarm. Servo valve flow abnormality: Compare the measured flow rates of the first and second flow sensors with the fitting curves of the servo valve input current. If the deviation exceeds the preset range, the valve core is determined to be worn.

2. The comprehensive test bench for performance testing and fault diagnosis of a hydraulic AGC system according to claim 1, characterized in that, The power pump assembly also includes a second filter, a third check valve, a second shut-off valve, and a fifth shut-off valve; The second filter is connected in series between the T-port return oil line of the servo valve and the oil tank; The third check valve is connected in series between the T-port return oil line of the servo valve and the second filter; The second shut-off valve is connected in series between the P port of the servo valve and the first shut-off valve; The fifth shut-off valve is located on the oil return line of the oil tank.

3. The comprehensive test bench for performance testing and fault diagnosis of a hydraulic AGC system according to claim 1, characterized in that, The servo valve's A port is connected to the rod chamber of the AGC hydraulic cylinder via a branch pipe and a connecting pipe, respectively, with a first quick connector and a second quick connector. The AGC hydraulic cylinder's rodless chamber is connected to the proportional relief valve via a third quick connector. The proportional relief valve is connected to the servo valve's P port via a branch pipe, with a fourth quick connector.

4. The comprehensive test bench for performance testing and fault diagnosis of a hydraulic AGC system according to claim 3, characterized in that, The first quick connector and the fourth quick connector are respectively connected to the first pressure gauge and the second pressure gauge.

5. The comprehensive test bench for performance testing and fault diagnosis of a hydraulic AGC system according to claim 1, characterized in that, The current signal of the proportional relief valve is programmed and output by the PC control terminal, and its opening degree is adjusted by the PLC control unit to simulate the actual back pressure of the AGC hydraulic cylinder.

6. A performance testing and fault diagnosis method for a comprehensive test bench based on the hydraulic AGC system performance testing and fault diagnosis according to any one of claims 1-5, characterized in that, Specifically, the following steps are included: S1. Performance testing and fault diagnosis of AGC hydraulic cylinders: S101. Install the fault-free servo valve and open all shut-off valves, including the first shut-off valve, the second shut-off valve, the third shut-off valve, the fourth shut-off valve, and the fifth shut-off valve. S102. Set the back pressure load through the proportional sequence valve and input a control signal to the servo valve to drive the AGC hydraulic cylinder; S103. Based on the third and fourth pressure sensors, monitor the pressure difference between the two chambers of the hydraulic cylinder, and calculate the internal leakage coefficient using a fifth-order polynomial fitting model. When the threshold is exceeded, trigger a leakage fault alarm. S104. Input step signal and sine wave signal to servo valve, collect response data through displacement sensor, and generate step response curve and frequency response bandwidth index. S2. Servo Valve Performance Testing and Fault Diagnosis: S201. Install a fault-free AGC hydraulic cylinder and open all shut-off valves; S202. Adjust the proportional sequence valve to set the load pressure and input a dynamic current signal to the servo valve; S203. Generate no-load flow characteristic curve and load flow parabola cluster through the first flow sensor and the second flow sensor. After closing the third and fourth shut-off valves, monitor the leakage of port T through the flow sensor. If the leakage exceeds the limit, trigger the servo valve leakage alarm. S204. Based on the monitoring of the pressure drop and current relationship by the second and sixth pressure sensors, a servo valve pressure characteristic curve is generated.

7. The method for performance testing and fault diagnosis of a hydraulic AGC system according to claim 6, characterized in that, The fifth-order polynomial fitting model is specifically as follows: ； Where af is the experimental calibration coefficient, and the step response time is judged by the displacement reaching 90% of the steady state value, and the frequency response bandwidth is judged by the cutoff frequency corresponding to the amplitude attenuation of -3dB.

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