A low-noise high-precision servo hydraulic control system for deep rock-soil laboratory

Abstract

The application belongs to the field of engineering simulation experiment equipment, and relates to a low-noise high-precision servo hydraulic control system for a deep rock-soil laboratory, which comprises an execution module for applying pressure to a sample, a power module integrated in a cabinet with sound insulation function, the power module being in hydraulic connection with the execution module and used for providing power for the execution module, a detection module for detecting the internal state of the hydraulic system in real time through a sensor, a control module connected with the execution module and the power module, built-in PID closed-loop control algorithm, the state of the execution module and the power module being sampled in real time through the sensor, the execution module being driven to execute after PID operation to form closed-loop control, and a man-machine interaction module used for setting experiment parameters by a user. The servo motor and the servo valve are combined to control the high-precision displacement and force closed-loop control in the sample pressing process, so as to meet the harsh requirements of deep rock-soil mechanics experiments.

Description

Technical Field

[0001] This invention relates to the field of engineering simulation experimental equipment technology, and in particular to a low-noise, high-precision servo hydraulic control system for deep geotechnical laboratories. Background Technology

[0002] In deep mining laboratory studies, in order to simulate the high-stress environment underground, it is usually necessary to use a hydraulic press to press samples of rock, soil, concrete or similar materials with high precision in order to test their mechanical properties.

[0003] Existing laboratory hydraulic presses typically consist of a standard motor, a metering pump, an on / off solenoid valve, and a hydraulic cylinder. Their main problems in practical use are as follows: Low control precision, unable to simulate complex stress paths in deep environments: Traditional hydraulic presses mostly use "start-stop" or "proportional valve" control, resulting in significant steady-state errors and hysteresis in pressure and displacement control. In precise loading scenarios requiring the simulation of micro-deformation in deep rock masses, the force and displacement control of traditional equipment cannot achieve millisecond-level response, leading to distorted experimental data.

[0004] Severe noise pollution disrupts the laboratory microenvironment: Traditional hydraulic stations typically use industrial frequency motors to drive quantitative pumps, resulting in significant energy overflow and throttling losses. During the pressurization and pressure holding phases, the motor operates at full speed, and the hydraulic oil generates a sharp whistling sound through the relief valve, with noise levels often reaching 80-90 decibels. Long-term operation seriously affects the hearing health of laboratory personnel and the quietness of the experimental environment.

[0005] High energy consumption and low energy efficiency: In the pressure holding stage, the motor of the traditional hydraulic system is still running idle or overflowing at full load. This not only generates a lot of heat energy, causing the oil temperature to rise and affecting the oil viscosity and thus the control accuracy, but also causes a great waste of electricity. Summary of the Invention

[0006] Technical problems to be solved In view of the above-mentioned shortcomings and deficiencies of the prior art, the present invention provides a low-noise, high-precision servo hydraulic control system for deep geotechnical laboratories, which solves the technical problems of low control accuracy, serious noise pollution and high energy consumption in the prior art. Technical solution

[0007] To achieve the above objectives, the main technical solutions adopted by the present invention include: This invention provides a low-noise, high-precision servo hydraulic control system for deep geotechnical laboratories, comprising an execution module, a power module, a detection module, a control module, and a human-machine interaction module; The execution module is used to apply pressure to the sample; The power module is integrated into a cabinet with sound insulation function. The power module is hydraulically connected to the execution module and is used to provide power to the execution module. The detection module uses sensors to detect the internal state of the hydraulic system in real time. The control module is connected to the execution module and the power module. It has a built-in PID closed-loop control algorithm. It samples the state of the execution module and the power module in real time through sensors, and drives the execution module to execute after PID calculation to form closed-loop control. The human-computer interaction module is used for users to set experimental parameters.

[0008] Optionally, the execution module includes: Hydraulic cylinder; The hydraulic cylinder adopts a servo actuator structure to directly apply pressure to the sample.

[0009] Optionally, the power module includes: Servo motor; Silent internal gear pump, directly connected to a servo motor; Servo proportional valves are installed on the valve assembly of the hydraulic station and are used to adjust the direction, speed and force of the hydraulic cylinder. Accumulator group, equipped with bladder-type accumulator, is used to absorb the pressure shock and pulsation generated when the servo proportional valve switches quickly, and to provide a large instantaneous flow when rapid replenishment of hydraulic oil is required. The air cooler uses a plate-type air cooler to force-cool the hydraulic oil.

[0010] Optionally, the detection module includes at least: The pressure sensor is installed on the main pressure oil line of the hydraulic station valve group. It uses a high-precision pressure transmitter to collect pressure signals in real time and build a force closed-loop control. The displacement sensor is a built-in magnetostrictive displacement sensor, which is embedded inside the piston rod of the hydraulic cylinder and uses the magnetostrictive principle to monitor the extension of the piston rod in real time. The integrated level and temperature sensor is installed on the hydraulic oil tank to monitor the hydraulic oil level and temperature in real time and feed the temperature signal back to the control system.

[0011] Optionally, the sensor waveguide of the displacement sensor is coaxially mounted with the piston rod of the hydraulic cylinder, and its moving magnetic ring moves synchronously with the piston of the hydraulic cylinder.

[0012] Optionally, the integrated liquid level and temperature sensor has both liquid level display and temperature sensing functions.

[0013] Optionally, the cylinder body of the hydraulic cylinder is made of high-strength alloy steel.

[0014] Optionally, the experimental parameters include at least one or more of the following: target loading force, loading rate, holding time, target displacement, and number of cycles.

[0015] Optionally, the control module provides two closed-loop control modes, including: In force control mode, the pressure sensor reads the pressure value in real time and feeds it back to the control module. The control module compares the set pressure with the actual pressure, outputs a command to the servo motor to adjust the speed, and at the same time fine-tunes the valve core opening of the servo proportional valve, forming a composite closed loop of pump control and valve control. In displacement control mode, the built-in magnetostrictive displacement sensor reads the displacement of the hydraulic cylinder in real time. The control module dynamically adjusts the opening direction and opening amount of the servo proportional valve according to the displacement error, so that the hydraulic cylinder piston rod moves at a constant speed according to the preset displacement curve.

[0016] Optionally, the control module executes a three-stage zero-noise control logic during the pressure holding phase, including: The servo proportional valve is closed to cut off the oil supply from the power module to the actuator module; The servo motor is completely stopped. The hydraulic cylinder maintains its pressure by relying on the hydraulic energy stored in the accumulator connected in parallel in the oil circuit. Beneficial effects

[0017] The beneficial effects of this invention are: The hydraulic cylinder and hydraulic station are treated as independent modular units, without experimental frames, which can be flexibly adapted to different specifications of loading frames in various deep mining laboratories, and have good versatility and expandability.

[0018] Through a series / parallel closed-loop control of a servo motor (pump-controlled) and a high-frequency response servo valve (valve-controlled), combined with a built-in magnetostrictive displacement sensor and a millisecond-response pressure sensor, the force control accuracy of this system can reach within ±0.5% of the indicated value, and the displacement control accuracy can reach ±0.01mm. The structural design of completely integrating the magnetostrictive displacement sensor inside the hydraulic cylinder piston rod eliminates signal distortion caused by installation errors or mechanical interference from external sensors. It can simulate the microscopic deformation and fracture process of deep rock masses under complex stress paths, achieving non-contact high-precision displacement measurement and dual high-precision closed-loop control of force and displacement during the pressing process. This avoids the defects of external sensors being susceptible to contamination and collisions, improves the validity and repeatability of experimental data, and enhances the reliability of the system under harsh working conditions.

[0019] In terms of noise reduction, a servo motor-driven internal gear pump, combined with a soundproof cabinet, eliminates fluid and mechanical noise from the hydraulic system at its source, reducing noise by approximately 10-15 decibels compared to traditional vane pumps. For control, the servo motor provides power on demand, avoiding the high-frequency whistling of the relief valve. During pressure holding, the servo motor power is cut off, and pressure is maintained using an accumulator, achieving zero-noise pressure holding and significantly reducing ambient noise in the laboratory. Under comprehensive testing, the equipment's operating noise can be controlled between 55-65 decibels, far lower than the 85 decibels of traditional equipment, improving the working environment for laboratory personnel.

[0020] Because the servo motor only operates at high speed when output flow is required, it consumes almost no power during the pressure holding phase. Compared to traditional fixed displacement pump systems, energy savings can reach 40%–70%. Simultaneously, the integrated solution of a liquid level and temperature sensor and a plate-type air cooler enables intelligent temperature control management. The integrated liquid level and temperature sensor monitors oil temperature in real time, and the plate-type air cooler provides on-demand cooling without the need for an external cooling water source. The cooler only activates when the oil temperature exceeds the set range, avoiding the energy waste caused by prolonged operation of traditional water-cooled systems. Furthermore, the system eliminates the need for an external cooling water source, removing maintenance risks such as water pipe corrosion and leaks, making it particularly suitable for independent deployment in laboratory settings. Attached Figure Description

[0021] Figure 1 This invention provides a structural diagram of a low-noise, high-precision servo hydraulic control system for a deep geotechnical laboratory. Figure 2 This is a hydraulic schematic diagram of a low-noise, high-precision servo hydraulic control system for a deep geotechnical laboratory, as described in an embodiment of the present invention.

[0022] [Explanation of Labels in the Attached Image] 1. Hydraulic oil tank; 2. Level gauge; 3. Air filter; 4. Integrated level and temperature sensor; 5. Suction filter; 6. Suction ball valve; 7. Servo motor; 8. Silent internal gear pump; 9. High-pressure filter; 10. Solenoid relief valve; 11. Air cooler; 12. Return oil filter; 13. Check valve; 14. Accumulator; 15. Pressure test connector; 16. Pressure gauge; 17. Pressure sensor; 18. Drain ball valve; 19. Stacked filter; 20. Servo valve; 21. High-pressure ball valve. Detailed Implementation

[0023] To better understand the above technical solutions, exemplary embodiments of the present invention will be described in more detail below with reference to the accompanying drawings. Although exemplary embodiments of the present invention are shown in the drawings, it should be understood that the present invention can be implemented in various forms and should not be limited to the embodiments set forth herein. Rather, these embodiments are provided so that the present invention can be understood more clearly and thoroughly, and that the scope of the present invention can be fully conveyed to those skilled in the art.

[0024] like Figure 1 As shown, this embodiment of the invention provides a low-noise, high-precision servo hydraulic control system for deep geotechnical laboratories, including an execution module, a power module, a detection module, a control module, and a human-machine interaction module.

[0025] The execution module, including a hydraulic cylinder, is used to apply pressure to the sample.

[0026] The hydraulic cylinder employs a servo actuator structure to directly apply pressure to the sample. The cylinder body is made of high-strength alloy steel to ensure stability and sealing under high-pressure conditions.

[0027] The power module is integrated into a soundproof cabinet. The power module is hydraulically connected to the execution module and provides power to the execution module, including: The servo motor is a permanent magnet synchronous servo motor, which has a fast response speed and adjustable speed.

[0028] Silent internal gear pump, directly connected to a servo motor. Compared to traditional vane pumps or external gear pumps, internal gear pumps have extremely low flow pulsation and mechanical noise.

[0029] Servo proportional valves are installed on the valve assembly of a hydraulic station and are used to precisely adjust the direction, speed, and force of the hydraulic cylinder's movement.

[0030] The accumulator group is equipped with a bladder-type accumulator to absorb the pressure shocks and pulsations generated when the servo proportional valve switches quickly, eliminate pipeline vibration noise, and provide instantaneous large flow when rapid replenishment of hydraulic oil is required.

[0031] The air cooler uses a plate-type air cooler to force-cool the hydraulic oil. Compared to water coolers, air coolers do not require an external cooling water source, making installation and maintenance simple and avoiding the risk of water pipe corrosion or leakage.

[0032] The detection module detects the internal state of the hydraulic system in real time through sensors, including at least: The pressure sensor, installed on the main pressure oil line of the hydraulic station valve group, uses a high-precision pressure transmitter to collect pressure signals in real time and build a force closed-loop control.

[0033] The main pressure oil circuit refers to the pipeline that starts after the check valve, flows sequentially through the accumulator group and the pressure sensor, and ends at the system hydraulic oil outlet.

[0034] The displacement sensor is a built-in magnetostrictive displacement sensor, embedded inside the piston rod of a hydraulic cylinder, utilizing the magnetostrictive principle for non-contact displacement measurement. Furthermore, the sensor waveguide of the displacement sensor is coaxially mounted with the piston rod of the hydraulic cylinder, and the moving magnetic ring of the displacement sensor moves synchronously with the piston of the hydraulic cylinder. This eliminates the risks of external sensors being susceptible to mechanical impact and oil contamination. It features high resolution (down to the micrometer level), strong anti-interference capability, and long service life, and is used for real-time monitoring of the piston rod extension (i.e., sample compression).

[0035] The integrated level and temperature sensor is mounted on the hydraulic oil tank. This sensor simultaneously displays the level and senses the temperature, monitoring the hydraulic oil level and temperature in real time and feeding the temperature signal back to the control system. When the oil temperature exceeds a set threshold, the plate-type air cooler automatically activates for forced cooling, ensuring the oil remains within its optimal operating temperature range (typically 35-45℃) and preventing a decrease in control accuracy due to temperature fluctuations.

[0036] The control module, as the central processing unit, adopts a PLC controller and is connected to the execution module and the power module. It has a built-in PID (proportional-integral-derivative) closed-loop control algorithm. It samples the state of the execution module and the power module in real time through sensors, and drives the execution module to execute after PID calculation, so as to form a closed-loop control.

[0037] The control module provides two closed-loop control modes, including: In force control mode, the pressure sensor reads the pressure value in real time and feeds it back to the control module. The control module compares the set pressure with the actual pressure, outputs a command to the servo motor to adjust the speed, and at the same time fine-tunes the valve core opening of the servo proportional valve, forming a composite closed loop of pump control and valve control. In displacement control mode, the built-in magnetostrictive displacement sensor reads the displacement of the hydraulic cylinder in real time. The control module dynamically adjusts the opening direction and opening amount of the servo proportional valve according to the displacement error, so that the hydraulic cylinder piston rod moves at a constant speed according to the preset displacement curve.

[0038] The human-computer interaction module is used for users to set experimental parameters.

[0039] The experimental parameters include at least one or more of the following: target loading force, loading rate, holding time, target displacement, and number of cycles.

[0040] This embodiment provides a low-noise, high-precision servo hydraulic control system for deep geotechnical laboratories. The specific usage process is as follows: The operator first sets the experimental parameters through the human-machine interface (HMI). After the settings are completed, the control system performs a self-check to confirm that the signals from each sensor are normal and that the oil level and oil temperature in the tank are within the allowable range.

[0041] After the system is powered on, the PLC controller sends a running command to the servo motor, which drives the silent internal gear pump to start. At this time, the system enters standby mode: the controller controls the servo motor to run at an extremely low speed (e.g., 300-500 rpm) according to the system pressure setpoint, maintaining only the basic standby pressure of the hydraulic system without overflowing through the relief valve. In this mode, the hydraulic station is almost noiseless, achieving silent standby and significantly reducing standby power consumption.

[0042] After the operator issues the start pressurization command via HMI, the control system executes the following two high-precision closed-loop control strategies according to the user-selected control mode (force control or displacement control): The force control mode is applicable to scenarios such as constant force loading and graded loading, and its specific process includes: The controller uses the target pressure value set by the HMI as the control target; The pressure sensor collects the pressure in the rodless chamber of the hydraulic cylinder in real time and feeds it back to the controller. The controller calculates the deviation between the set pressure and the actual pressure. If the deviation is large, the controller first outputs a speed adjustment command to the servo motor to increase the motor speed, thereby increasing the output flow of the oil pump, driving the hydraulic cylinder piston to extend rapidly, so that the system pressure quickly approaches the target value; When the system pressure approaches the target value (enters the set fine-tuning threshold), the controller stops coarsely adjusting the servo motor and instead finely adjusts the valve core opening of the servo proportional valve. By controlling the precise amount of oil entering the cylinder, the pressure is finely adjusted to eliminate steady-state error. Through a combined closed-loop strategy of pump-controlled coarse adjustment and valve-controlled fine adjustment, it can quickly respond to and stabilize at the target pressure value, with force control accuracy within ±0.5% of the indicated value, ensuring the linearity and accuracy of the applied force.

[0043] The displacement control mode is suitable for scenarios such as displacement rate loading and fixed-point displacement holding, and its specific process includes: The controller uses the target displacement value or displacement-time curve set by the HMI as the control target.

[0044] An integrated magnetostrictive displacement sensor reads the extension of the hydraulic cylinder piston rod (i.e., the sample compression) in real time and feeds it back to the controller. The controller calculates the deviation between the target displacement and the actual displacement. The controller dynamically adjusts the opening direction and amount of the servo proportional valve in real time based on the displacement deviation signal. When the displacement deviation is large, the valve opening is large and the cylinder moves quickly; when the displacement deviation is small, the valve opening is small and the cylinder moves slowly, thereby enabling the piston rod to move precisely according to a preset displacement curve (such as uniform speed, segmented speed change, etc.), with a displacement control accuracy of ±0.01mm.

[0045] When a pressing stroke is completed and reversal is needed for unloading or cyclic loading, the controller sends a reversal signal to the servo proportional valve. At the moment the valve core switches, a high-pressure shock wave is generated in the oil circuit. At this moment, the accumulator connected in parallel in the main oil circuit instantly comes into play: its internal bladder rapidly absorbs the pressure spikes and flow pulsations generated by the commutation by compressing nitrogen, converting the impact energy into the compressible energy of the gas. Through this process, the pressure shock wave is effectively isolated and cannot be transmitted to the built-in magnetostrictive displacement sensor through the oil, thus protecting the sensor waveguide from pressure pulsation interference and ensuring the purity and long-term stability of the displacement feedback signal.

[0046] Once the sample compression reaches the set target value (such as target pressure or displacement), the system enters the pressure holding stage. At this time, the controller executes a three-stage zero-noise control logic.

[0047] The three-stage zero-noise control logic includes: The controller sends a shut-off signal to the servo proportional valve, cutting off the oil supply from the hydraulic station to the hydraulic cylinder.

[0048] The controller sends a zero-speed command to the servo motor, causing the servo motor to stop completely, and the silent internal gear pump directly connected to it also stops simultaneously. At this time, no mechanical moving parts are operating in the hydraulic station.

[0049] The system relies entirely on the hydraulic energy stored in the accumulator connected in parallel with the oil circuit to maintain the pressure holding pressure of the hydraulic cylinder. At the same time, the accumulator continuously absorbs pressure changes caused by fluctuations in ambient temperature or minor oil leaks, keeping the sample stable at the set pressing state for a long time.

[0050] At this stage, since the servo motor stops completely, the system achieves true zero-decibel noise output, completely eliminating the continuous noise generated by the motor running idle or the relief valve whistling during the pressure holding stage of traditional hydraulic systems.

[0051] After the pressure holding time ends, the system enters the depressurization and return phase.

[0052] The pressure relief includes: the controller controls the servo proportional valve to slowly switch to the return oil position, and the pressure oil in the rodless chamber of the hydraulic cylinder is slowly released back to the oil tank through the servo proportional valve to prevent the hydraulic shock caused by the sudden drop in pressure.

[0053] The return stroke includes: after the pressure is fully released, the controller sends a return command to the servo proportional valve, and hydraulic oil enters the rod chamber of the hydraulic cylinder, pushing the piston rod to quickly return to the initial position.

[0054] After the depressurization and return phases are completed, the displacement sensor feedback piston has returned to the zero position, and the system enters silent standby mode again, waiting for the next experimental command.

[0055] To further illustrate the low-noise, high-precision servo hydraulic control system for deep geotechnical laboratories provided in this embodiment, the following description is provided in conjunction with specific implementation methods: like Figure 2 As shown, in actual use, the hydraulic oil in the hydraulic oil tank 1 is drawn in by the silent internal gear pump 8 driven by the servo motor 7 after passing through the suction ball valve 6 and the suction filter 5.

[0056] The level gauge 2 and the temperature and level sensor 4 are installed on the hydraulic oil tank 1 to monitor the level and temperature of the oil. The air filter 3 is installed at the filling port to maintain the air pressure balance of the oil tank. The drain port at the lowest point of the bottom of the hydraulic oil tank 1 is equipped with a drain ball valve to drain the old oil. The sampling ball valve is installed at the side sampling port to collect oil samples for testing.

[0057] The hydraulic oil output from the silent internal gear pump 8 first enters the high-pressure filter 9 for fine filtration. The filtered hydraulic oil is then divided into two paths before the check valve 13: The first path is the safety unloading branch, which is connected to the oil inlet of the electromagnetic overflow valve 10, and its oil outlet is directly connected back to the hydraulic oil tank 1. It is used to set the maximum working pressure of the system and realize unloading protection.

[0058] The second line is the working oil supply branch, which is connected to the oil inlet of the one-way valve 13.

[0059] After the hydraulic oil flows through the check valve 13, it enters the main pressure oil circuit. This section of the oil circuit is connected in sequence to: Accumulator 14 is connected in parallel to the main oil circuit to absorb pressure shocks, provide instantaneous large flow rates, and maintain pressure.

[0060] Pressure gauge 16, connected via pressure test connector 15, is used for on-site visual pressure inspection.

[0061] Pressure sensor 17 is used to acquire pressure signals in real time and feed them back to the controller.

[0062] After passing through the aforementioned components, the main hydraulic oil circuit splits into two paths again near the hydraulic cylinder, including: Working circuit: Hydraulic oil first enters the stacked filter 19 for pre-valve fine filtration to protect the servo valve. Then it enters the P port of the servo valve 20. According to the control signal from the controller, the servo valve 20 outputs from its A and B ports, which are respectively connected to two high-pressure ball valves 21, and then to the rodless chamber and rod chamber of the hydraulic cylinder. By placing the valve assembly near the cylinder, the oil circuit length is reduced, thereby improving the dynamic response speed of the system.

[0063] Pressure relief branch: connected to the oil inlet of the oil drain ball valve 18.

[0064] Subsequently, the hydraulic oil flows back to the oil tank through the return port T of the servo valve 20, and merges with the outlet of the drain ball valve 18 and the outlet pipeline of the solenoid relief valve 10. The combined return oil then flows sequentially through the air cooler 11 and the return oil filter 12, and finally returns to the hydraulic oil tank 1.

[0065] Those skilled in the art will understand that embodiments of the present invention can be provided as methods, systems, or computer program products. Therefore, the present invention can take the form of a completely hardware embodiment, a completely software embodiment, or an embodiment combining software and hardware aspects. Furthermore, the present invention can take the form of a computer program product embodied on one or more computer-usable storage media (including, but not limited to, disk storage, CD-ROM, optical storage, etc.) containing computer-usable program code.

[0066] Obviously, those skilled in the art can make various modifications and variations to this invention without departing from its spirit and scope. Therefore, if these modifications and variations fall within the scope of the claims of this invention and their equivalents, then this invention should also include these modifications and variations.

[0067] Although embodiments of the present invention have been shown and described above, it is understood that the above embodiments are exemplary and should not be construed as limiting the present invention. Those skilled in the art can make modifications, alterations, substitutions and variations to the above embodiments within the scope of the present invention.

Claims

1. A low-noise, high-precision servo hydraulic control system for deep geotechnical laboratories, characterized in that, It includes an execution module, a power module, a detection module, a control module, and a human-machine interaction module; The execution module is used to apply pressure to the sample; The power module is integrated into a cabinet with sound insulation function. The power module is hydraulically connected to the execution module and is used to provide power to the execution module. The detection module uses sensors to detect the internal state of the hydraulic system in real time. The control module is connected to the execution module and the power module. It has a built-in PID closed-loop control algorithm. It samples the state of the execution module and the power module in real time through sensors, and drives the execution module to execute after PID calculation to form closed-loop control. The human-computer interaction module is used for users to set experimental parameters.

2. The low-noise, high-precision servo hydraulic control system for deep geotechnical laboratories according to claim 1, characterized in that, The execution module includes: Hydraulic cylinder; The hydraulic cylinder employs a servo actuator structure to directly apply pressure to the sample.

3. The low-noise, high-precision servo hydraulic control system for deep geotechnical laboratories according to claim 2, characterized in that, The power module includes: Servo motor; Silent internal gear pump, directly connected to a servo motor; Servo proportional valves are installed on the valve assembly of the hydraulic station and are used to adjust the direction, speed and force of the hydraulic cylinder. Accumulator group, equipped with bladder-type accumulator, is used to absorb the pressure shock and pulsation generated when the servo proportional valve switches quickly, and to provide a large instantaneous flow when rapid replenishment of hydraulic oil is required. The air cooler uses a plate-type air cooler to force-cool the hydraulic oil.

4. The low-noise, high-precision servo hydraulic control system for deep geotechnical laboratories according to claim 3, characterized in that, The detection module includes at least: The pressure sensor is installed on the main pressure oil line of the hydraulic station valve group. It uses a high-precision pressure transmitter to collect pressure signals in real time and build a force closed-loop control. The displacement sensor is a built-in magnetostrictive displacement sensor, which is embedded inside the piston rod of the hydraulic cylinder and uses the magnetostrictive principle to monitor the extension of the piston rod in real time. The integrated level and temperature sensor is installed on the hydraulic oil tank to monitor the hydraulic oil level and temperature in real time and feed the temperature signal back to the control system.

5. The low-noise, high-precision servo hydraulic control system for deep geotechnical laboratories according to claim 4, characterized in that, The sensor waveguide of the displacement sensor is coaxially mounted with the piston rod of the hydraulic cylinder, and its moving magnetic ring moves synchronously with the piston of the hydraulic cylinder.

6. The low-noise, high-precision servo hydraulic control system for deep geotechnical laboratories according to claim 5, characterized in that, The integrated liquid level and temperature sensor has both liquid level display and temperature sensing functions.

7. The low-noise, high-precision servo hydraulic control system for deep geotechnical laboratories according to claim 6, characterized in that, The cylinder body of the hydraulic cylinder is made of high-strength alloy steel.

8. The low-noise, high-precision servo hydraulic control system for deep geotechnical laboratories according to claim 7, characterized in that, The experimental parameters include at least one or more of the following: target loading force, loading rate, holding time, target displacement, and number of cycles.

9. The low-noise, high-precision servo hydraulic control system for deep geotechnical laboratories according to claim 8, characterized in that, The control module provides two closed-loop control modes, including: In force control mode, the pressure sensor reads the pressure value in real time and feeds it back to the control module. The control module compares the set pressure with the actual pressure, outputs a command to the servo motor to adjust the speed, and at the same time fine-tunes the valve core opening of the servo proportional valve, forming a composite closed loop of pump control and valve control. In displacement control mode, the built-in magnetostrictive displacement sensor reads the displacement of the hydraulic cylinder in real time. The control module dynamically adjusts the opening direction and opening amount of the servo proportional valve according to the displacement error, so that the hydraulic cylinder piston rod moves at a constant speed according to the preset displacement curve.

10. The low-noise, high-precision servo hydraulic control system for deep geotechnical laboratories according to claim 9, characterized in that, The control module executes a three-stage zero-noise control logic during the pressure holding phase, including: The servo proportional valve is closed to cut off the oil supply from the power module to the actuator module; The servo motor is completely stopped. The hydraulic cylinder maintains its pressure by relying on the hydraulic energy stored in the accumulator connected in parallel in the oil circuit.

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