Comprehensive test bed and method for performance detection and fault diagnosis of hydraulic AGC system

Abstract

The invention discloses a hydraulic AGC system performance detection and fault diagnosis comprehensive test bench and method, and relates to the technical field of hydraulic AGC system performance detection, and the hydraulic AGC system performance detection and fault diagnosis comprehensive test bench comprises a power pump assembly, a servo valve, a proportional overflow valve, a data acquisition module, an auxiliary assembly, a PLC control unit and a PC control end; compared with a traditional two-hydraulic-cylinder opposite-jacking loading mode, the loading mode that the proportional overflow valve is used for providing back pressure for the hydraulic cylinders is safer and higher in reliability, and a hydraulic system is simplified. Multiple performance indexes are accurately measured, complex faults are accurately recognized, the detection accuracy and diagnosis precision are improved, through high-frequency data collection and real-time comparison of threshold values and models, manual control and traditional relay control are replaced by PLC control, and the system is simple in structure and convenient to operate. The testing efficiency and safety are improved, and the system has the diagnosis function of detecting faults such as leakage, step response, frequency response, servo valve dynamic and static performance and the like in the AGC hydraulic cylinder.

Description

Technical Field

[0001] The present invention relates to the technical field of hydraulic AGC system performance detection and fault diagnosis, and in particular to a comprehensive test bench and method for hydraulic AGC system performance detection and fault diagnosis. Background Art

[0002] The AGC system automatically adjusts the distance between the rolls and the pressure of the hydraulic cylinder in real time to ensure that the thickness of the steel remains stable during the rolling process. The accuracy and response speed of the AGC system are crucial to the stability of production and the quality of steel. In the AGC system, the hydraulic cylinder is responsible for controlling the dynamic adjustment of the mill roll gap. Its performance and working status directly affect the stability and production efficiency of the mill. If the hydraulic cylinder and servo valve fail, the roll gap control will be inaccurate, which will ultimately affect the quality and production efficiency of the steel.

[0003] Performance testing and fault diagnosis of AGC hydraulic cylinders and servo valves can detect potential problems early and avoid production interruptions caused by equipment failure, thereby improving the stability and production efficiency of the production line. Optimization and troubleshooting of hydraulic cylinder and servo valve performance can ensure more accurate thickness control of the rolling mill, reduce product thickness fluctuations caused by unstable control, and ensure the quality and consistency of steel. Through regular testing and preventive maintenance, major failures of hydraulic cylinders and servo valves can be avoided, and unexpected downtime and maintenance costs can be reduced. This not only reduces the operating cost of the equipment, but also extends the service life of hydraulic cylinders and servo valves. If a hydraulic system fails, it may cause unstable mill operation and may even cause safety accidents. Through real-time monitoring and early diagnosis, potential faults can be discovered in time, accidents can be prevented, and production safety can be guaranteed.

[0004] With the development of production technology, the control of hydraulic systems has become more and more complex, and the technical means of fault diagnosis for AGC hydraulic cylinders and servo valves are also constantly developing. Modern fault diagnosis methods include technologies based on signal processing, data analysis, artificial intelligence, etc., 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] The dynamic performance test of AGC hydraulic cylinders is highly professional, technically difficult, and has special requirements for test equipment. Therefore, most AGC hydraulic cylinder manufacturers in my country do not have the ability to perform dynamic performance tests on AGC hydraulic cylinders. The servo valve has a high failure rate and is difficult to repair, which has a great impact on the stability and reliability of the system. Therefore, there is an urgent need for a comprehensive test bench and method for performance detection and fault diagnosis of hydraulic AGC systems to improve the efficiency and accuracy of performance detection and fault diagnosis of AGC hydraulic cylinders and servo valves, and reduce the cost and maintenance difficulty of enterprises. Summary of the invention

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

[0007] In order to solve the above technical problems, the present invention provides a comprehensive test bench and method for hydraulic AGC system performance detection and fault diagnosis, including:

[0008] A power pump assembly, comprising a fuel tank, a variable displacement pump, a motor, a first filter, a first one-way valve, a first stop valve, an accumulator and a pilot relief valve;

[0009] The oil suction port of the variable pump is connected to the oil tank, and the outlet is connected in series with a first filter, a first one-way valve, and a first stop valve in sequence;

[0010] The accumulator and the pilot relief valve are connected in parallel to the outlet of the first stop valve;

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

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

[0013] Data acquisition module, including:

[0014] A first pressure sensor is installed in the pipeline between the first filter outlet and the first one-way valve;

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

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

[0017] The fourth pressure sensor and the fifth pressure sensor are respectively installed at the inlet and outlet of the proportional relief valve;

[0018] a sixth pressure sensor, mounted at the P port of the servo valve;

[0019] The first flow sensor and the second flow sensor are installed at the A port and the B port of the servo valve respectively;

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

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

[0022] An auxiliary component, comprising an air filter, a liquid level gauge and a temperature sensor, wherein the air filter is arranged on the top of the oil tank, the liquid 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] A PLC control unit is electrically connected to the servo valve, the proportional relief valve and the motor, and receives a feedback signal 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 one-way valve, a second shut-off valve, and a fifth shut-off valve;

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

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

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

[0029] The fifth stop valve is arranged on the oil return pipeline of the oil tank.

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

[0031] Internal leakage fault: According to the pressure difference Δp between the rodless cavity and the rod cavity detected by the third pressure sensor and the fourth pressure sensor, the formula

[0032]

[0033] Calculate the leakage volume and trigger an alarm if it exceeds the threshold;

[0034] Servo valve flow abnormality: Compare the measured flow of the first flow sensor and the second flow sensor with the fitting curve of the servo valve input current. If the deviation exceeds the preset range, it is determined that the valve core is worn.

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

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

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

[0038] The present invention also provides a hydraulic AGC system performance detection and fault diagnosis method, which specifically includes the following steps:

[0039] S1.AGC hydraulic cylinder performance detection and fault diagnosis:

[0040] S101. Install a trouble-free servo valve and open all stop valves, including the first stop valve, the second stop valve, the third stop valve, the fourth stop valve and the fifth stop 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 pressure sensor and the fourth pressure sensor, the pressure difference between the two chambers of the hydraulic cylinder is monitored, and the internal leakage coefficient is calculated in combination with the fifth-order polynomial fitting model. When the threshold is exceeded, a leakage fault alarm is triggered;

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

[0044] S2. Servo valve performance detection and fault diagnosis:

[0045] S201. Install the trouble-free AGC hydraulic cylinder and open all stop 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, close the third stop valve and the fourth stop valve, and monitor the leakage of the T port through the flow sensor. When the limit is exceeded, the servo valve leakage alarm is triggered;

[0048] S204. Generate a servo valve pressure characteristic curve based on the relationship between the pressure drop and the current monitored by the second pressure sensor and the sixth pressure sensor.

[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 determined by the displacement reaching 90% of the steady-state value, and the frequency response bandwidth is determined by the cut-off frequency corresponding to the amplitude attenuation of -3dB.

[0052] Compared with the related art, the comprehensive test bench and method for hydraulic AGC system performance detection and fault diagnosis provided by the present invention have the following beneficial effects:

[0053] The present invention provides a comprehensive test bench and method for hydraulic AGC system performance detection and fault diagnosis. The loading method of using a proportional relief valve to provide back pressure for the hydraulic cylinder is safer and more reliable than the traditional two-hydraulic cylinder top loading method, and simplifies the hydraulic system. Accurately measure multiple performance indicators, accurately identify complex faults, improve detection accuracy and diagnostic accuracy, collect high-frequency data, compare thresholds and models in real time, use PLC control to replace manual control and traditional relay control, improve test efficiency and safety, and have the diagnostic function of detecting leakage in the AGC hydraulic cylinder, step response, frequency response, and dynamic and static performance of the servo valve. BRIEF DESCRIPTION OF THE DRAWINGS

[0054] Figure 1 It is the hydraulic principle diagram of the present invention;

[0055] Figure 2 is a system control flow chart of the present invention;

[0056] Figure 3 It is the internal leakage coefficient and pressure difference fitting curve diagram of the present invention.

[0057] Numbers in the figure: 1, variable pump; 21, first filter; 22, second filter; 31, first one-way valve; 32, second one-way valve; 33, third one-way valve; 41, first stop valve; 42, second stop valve; 43, third stop valve; 44, fourth stop valve; 45, fifth stop 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 relief valve; 7, accumulator Energy device; 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, fuel tank; 18, liquid level meter; 19, motor; 201, first quick-change connector; 202, second quick-change connector; 203, third quick-change connector; 204, fourth quick-change connector. DETAILED DESCRIPTION

[0058] The present invention provides a comprehensive test bench and method for performance detection and fault diagnosis of a hydraulic AGC system, which integrates the static and dynamic performance detection functions of an AGC hydraulic cylinder and a servo valve on one device. The test carries out performance detection and fault diagnosis of the AGC hydraulic cylinder and the servo valve according to a preset program.

[0059] Specifically, it includes a PC control terminal, an AGC hydraulic cylinder and a servo valve test platform. The PC terminal controls the electro-hydraulic servo valve of the test bench through a programmable controller, thereby controlling the action of the AGC hydraulic cylinder. The PC control terminal displays and stores the experimental data. The test bench tests the static and dynamic performance of the AGC hydraulic cylinder and the static performance of the servo valve according to the latest national testing standards. The signals of the sensors of the entire test bench are sent to the PC terminal through a data acquisition card.

[0060] Embodiment 1

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

[0062] Embodiment 2 (Internal leakage detection)

[0063] Close the third stop valve 43 and the fourth stop valve 44, and monitor the pressure difference Δp between the rodless chamber and the rod chamber of the AGC hydraulic cylinder 11 through the third pressure sensor 53 and the fourth pressure sensor 54, and combine the flow formula:

[0064]

[0065] Calculate the internal leakage.

[0066] The fifth-order polynomial model fitted according to the experimental data is:

[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 leakage fault prediction model is:

[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, the PC triggers a fault alarm.

[0072] Example 3 (Step Response Test)

[0073] The first stop valve 41, the second stop valve 42, the third stop valve 43, the fourth stop valve 44, and the fifth stop valve 45 are opened, and a step signal is input to the servo valve 8 to 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 terminal generates a step response curve, with the time for the displacement to reach 90% of the steady-state value as the response index.

[0074] Embodiment 4 (Frequency Response Test)

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

[0076] Embodiment 5 (Leakage detection in servo valve)

[0077] Close the third stop valve 43 and the fourth stop valve 44 to make the load flow zero. The third flow sensor 93 monitors the leakage of the servo valve 8T port. When the leakage exceeds the preset threshold (such as zero position leakage>5% rated flow), the PC terminal triggers the servo valve internal leakage fault alarm.

[0078] Example 6 (Servo valve flow characteristics test)

[0079] The load pressure of the proportional relief valve 13 is adjusted, and a dynamic current signal is input to the servo valve 8. The first flow sensor 91 and the second flow sensor 92 respectively record the flow of port A and port B, generate a no-load flow characteristic curve and a load flow-pressure parabola cluster, and compare the standard curve to determine whether the valve core is worn or stuck.

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

[0081] The pilot relief valve 6 is adjusted to make the oil supply pressure constant, and the third stop valve 43 and the fourth stop 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, and generate a pressure difference-input current relationship curve. When the deviation exceeds ±10%, it is determined that the pressure characteristic is abnormal.

[0082] Working principle:

[0083] 1.Performance detection and fault diagnosis of AGC cylinder

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

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

[0086]

[0087] Calculate the leakage volume;

[0088] 2) Step response test: a step signal is input 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: A sine wave signal is input to the servo valve 8, and the frequency response bandwidth is calculated through the amplitude and phase data of the displacement sensor 12.

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

[0091] When performing performance testing and fault diagnosis of the servo valve 8, install a fault-free AGC hydraulic cylinder 11, open all stop valves, and adjust the back pressure load of the proportional relief valve 13 through the current signal 14. The specific process is as follows:

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

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

[0094] 3) Internal leakage detection: close the third stop valve 43 and the fourth stop valve 44, and the third flow sensor 93 monitors the leakage of the servo valve 8T port, and triggers an alarm when the threshold is exceeded.

Claims

1. A comprehensive test bench for hydraulic AGC system performance detection and fault diagnosis, characterized by: include: A power pump assembly, comprising a fuel tank, a variable displacement pump, a motor, a first filter, a first one-way valve, a first stop valve, an accumulator and a pilot relief valve; The oil suction port of the variable pump is connected to the oil tank, and the outlet of the variable pump is connected in series with a first filter, a first one-way valve, and a first stop valve in sequence; The accumulator and the pilot relief valve are connected in parallel to the outlet of the first stop valve; The servo valve has its P port connected to the outlet of the first stop valve, its A port connected to the rodless chamber of the AGC hydraulic cylinder through the third stop valve, its B port connected to the rod chamber of the AGC hydraulic cylinder through the fourth stop valve, and its T port returns oil to the oil tank; A proportional relief valve is connected in series to the rod chamber circuit of the AGC hydraulic cylinder and is connected in parallel to the second check valve; Data acquisition module, including: A first pressure sensor is installed in the pipeline between the first filter outlet and the first one-way valve; A second pressure sensor is installed at the inlet of the accumulator; The third pressure sensor is installed at the rodless chamber inlet of the AGC hydraulic cylinder; The fourth pressure sensor and the fifth pressure sensor are respectively installed at the inlet and outlet of the proportional relief valve; a sixth pressure sensor, mounted at the P port of the servo valve; The first flow sensor and the second flow sensor are installed at the A port and the B port of the servo valve respectively; The third flow sensor is installed on the T-port oil return pipeline of the servo valve; The displacement sensor is fixed to the piston rod end of the AGC hydraulic cylinder; An auxiliary component, comprising an air filter, a liquid level gauge and a temperature sensor, wherein the air filter is arranged on the top of the oil tank, the liquid 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; A PLC control unit is electrically connected to the servo valve, the proportional relief valve and the motor, and receives a feedback signal 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.

2. A comprehensive test bench for hydraulic AGC system performance detection and fault diagnosis according to claim 1, characterized in that: The power pump assembly also includes a second filter, a third one-way valve, a second stop valve and a fifth stop valve; The second filter is connected in series between the T-port oil return pipeline of the servo valve and the oil tank; The third one-way valve is connected in series between the T-port oil return pipeline of the servo valve and the second filter; The second stop valve is connected in series between the P port of the servo valve and the first stop valve; The fifth stop valve is arranged on the oil return pipeline of the oil tank.

3. A comprehensive test bench for hydraulic AGC system performance detection and fault diagnosis according to claim 1, characterized in that: The decision logic of the fault diagnosis module includes: Internal leakage fault: According to the pressure difference Δp between the rodless cavity and the rod cavity detected by the third pressure sensor and the fourth pressure sensor, the formula Calculate the leakage volume and trigger an alarm if it exceeds the threshold; Servo valve flow abnormality: Compare the measured flow of the first flow sensor and the second flow sensor with the fitting curve of the servo valve input current. If the deviation exceeds the preset range, it is determined that the valve core is worn.

4. A comprehensive test bench for hydraulic AGC system performance detection and fault diagnosis according to claim 1, characterized in that: A first quick connector and a second quick connector are respectively provided on the branch line and the connecting line between the A port of the servo valve and the rod chamber of the AGC hydraulic cylinder, a third quick connector is provided on the connecting line between the rodless chamber of the AGC hydraulic cylinder and the proportional relief valve, and a fourth quick connector is provided on the branch line of the connecting line between the proportional relief valve and the P port of the servo valve.

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

6. A comprehensive test bench for hydraulic AGC system performance detection and fault diagnosis 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 is adjusted by the PLC control unit to simulate the actual working back pressure of the AGC hydraulic cylinder.

7. A performance detection and fault diagnosis method based on the comprehensive test bench for hydraulic AGC system performance detection and fault diagnosis according to any one of claims 1 to 6, characterized in that: The specific steps include: S1.AGC hydraulic cylinder performance detection and fault diagnosis: S101. Install a trouble-free servo valve and open all stop valves, including the first stop valve, the second stop valve, the third stop valve, the fourth stop valve and the fifth stop 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 pressure sensor and the fourth pressure sensor, the pressure difference between the two chambers of the hydraulic cylinder is monitored, and the internal leakage coefficient is calculated in combination with the fifth-order polynomial fitting model. When the threshold is exceeded, a leakage fault alarm is triggered; S104. Input a step signal and a sine wave signal to the servo valve, collect response data through a displacement sensor, and generate a step response curve and a frequency response bandwidth index; S2. Servo valve performance detection and fault diagnosis: S201. Install the trouble-free AGC hydraulic cylinder and open all stop 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, close the third stop valve and the fourth stop valve, and monitor the leakage of the T port through the flow sensor. When the limit is exceeded, the servo valve leakage alarm is triggered; S204. Generate a servo valve pressure characteristic curve based on the relationship between the pressure drop and the current monitored by the second pressure sensor and the sixth pressure sensor.

8. A method for performance detection and fault diagnosis of a hydraulic AGC system according to claim 7, characterized in that: The fifth-order polynomial fitting model is specifically: Q=aΔP 5 +bΔP 4 +cΔP 3 +dΔP 2 +eΔP+f Where af is the experimental calibration coefficient, and the step response time is determined by the displacement reaching 90% of the steady-state value, and the frequency response bandwidth is determined by the cut-off frequency corresponding to the amplitude attenuation of -3dB.

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