A control method for a thrust hydraulic length adjustment device

Abstract

The application provides a control method of a thrust type hydraulic length adjusting device, and belongs to the technical field of device control. The method comprises the following steps: step 1: establishing a piston cylinder data model based on the piston rodless cavity area, the rodless cavity pressure, the piston rod cavity area, the rod cavity pressure, the viscous damping coefficient, the piston movement speed, the friction and the load of the piston cylinder of the thrust type hydraulic length adjusting device; step 2: constructing a closed-loop feedback system of the hydraulic system of the thrust type hydraulic length adjusting device and performing closed-loop feedback control; step 3: adjusting the flow according to the total control amount as an adaptive sliding mode control instruction; and step 4: adjusting the pressure of the hydraulic pump according to the rodless cavity pressure error of the piston cylinder. The method effectively avoids the defects of the existing thrust type hydraulic length adjusting device, such as slow response speed, the influence of the adjusting precision by multiple factors and the difficulty in realizing high-precision length fine adjustment.

Description

TECHNICAL FIELD

[0001] The application belongs to the technical field of device control, and particularly relates to a control method of a thrust type hydraulic length adjusting device. BACKGROUND

[0002] At present, the thrust type hydraulic length adjusting device mentioned in the prior art solution with the patent publication number CN119349406A is widely applied in industrial production. However, the hydraulic system of the existing thrust type hydraulic length adjusting device generally has the problem of slow response speed, and it is difficult to meet the work scene with high requirements on the adjusting timeliness. At the same time, the adjusting accuracy is affected by many factors, so that it is difficult to realize high-precision length fine adjustment in actual application, and the application in the field with high accuracy requirements is limited. SUMMARY

[0003] To solve the defects in the prior art, the application provides a control method of a thrust type hydraulic length adjusting device, which effectively avoids the defects of the existing thrust type hydraulic length adjusting device, such as slow response speed of the hydraulic system, adjusting accuracy affected by many factors, and difficulty in realizing high-precision length fine adjustment.

[0004] The application uses the following technical solutions.

[0005] A control method of a thrust type hydraulic length adjusting device, comprising:

[0006] Step 1: establishing a piston cylinder data model based on the piston rodless cavity area, rodless cavity pressure, piston rod cavity area, rod cavity pressure, viscous damping coefficient, piston movement speed, friction and load force of the piston cylinder of the thrust type hydraulic length adjusting device;

[0007] Step 2: constructing a closed-loop feedback system of the hydraulic system of the thrust type hydraulic length adjusting device and performing closed-loop feedback control;

[0008] Step 3: adjusting the flow according to the total control amount as an adaptive sliding mode control instruction

[0009] Step 4: adjusting the pressure of the hydraulic pump according to the rodless cavity pressure error of the piston cylinder.

[0010] Further, in step 1, the expression of the piston cylinder data model is:

[0011] ;

[0012] wherein T is the thrust generated by the piston cylinder, A is the piston rodless cavity area of the piston cylinder, P is the rodless cavity pressure of the piston cylinder,​ Piston rod cavity area of the piston cylinder, Piston rod cavity pressure of the piston cylinder, Viscous damping coefficient of the piston cylinder, Piston velocity of the piston cylinder, Friction of the piston cylinder, Load force of the piston cylinder.

[0013] Further, in step 1, the piston rod cavity pressure of the piston cylinder is collected by pressure sensor one connected to the controller and transmitted to the controller, pressure sensor one is arranged in the oil inlet pipeline of the piston rod cavity of the piston cylinder, the piston rod cavity pressure of the piston cylinder is collected by pressure sensor two connected to the controller and transmitted to the controller, pressure sensor two is arranged in the oil inlet pipeline of the piston rod cavity of the piston cylinder, the piston velocity of the piston cylinder is collected by velocity sensor connected to the controller and transmitted to the controller, velocity sensor is arranged on the piston rod of the piston cylinder, the load force of the piston cylinder is collected by tension sensor and transmitted to the controller, tension sensor is arranged at the connection part of the load and the piston cylinder, the friction of the piston cylinder is the thrust generated by the piston cylinder under no load condition .

[0014] Further, in step 2, the method for constructing the closed-loop feedback system of the hydraulic system of the thrust hydraulic length adjusting device includes:

[0015] The displacement sensor connected to the controller is arranged on the piston rod of the piston cylinder of the thrust hydraulic length adjusting device, so that the controller, the proportional flow valve, the proportional pressure valve, pressure sensor one and pressure sensor two constitute the closed-loop feedback system of the hydraulic system of the thrust hydraulic length adjusting device, and the displacement sensor collects the displacement of the piston rod and transmits it to the controller.

[0016] Further, in step 2, the method for executing closed-loop feedback control includes:

[0017] Step 2-1: filtering the load force of the piston cylinder, the piston rod cavity pressure of the piston cylinder, the piston rod cavity pressure of the piston cylinder and the displacement of the piston rod transmitted to the controller;

[0018] Step 2-2: calculating multi-dimensional error;

[0019] Step 2-3: generating adaptive sliding mode control instruction.

[0020] Furthermore, in step 2-1, the load force of the piston cylinder, the pressure in the rodless chamber of the piston cylinder, the pressure in the rod chamber of the piston cylinder, and the displacement of the piston rod transmitted to the controller are filtered using an improved second-order Butterworth low-pass filter. The calculation formula for the improved second-order Butterworth low-pass filter is as follows:

[0021] ;

[0022] in The filtered first Load capacity of a piston cylinder Pressure in the rodless chamber of the piston cylinder Pressure in the rod chamber of the piston cylinder Or the displacement of the piston rod. The filtered first Load capacity of a piston cylinder Pressure in the rodless chamber of the piston cylinder Pressure in the rod chamber of the piston cylinder Or the displacement of the piston rod. The filtered first Load capacity of a piston cylinder Pressure in the rodless chamber of the piston cylinder Pressure in the rod chamber of the piston cylinder Or the displacement of the piston rod. For the transmission to the controller Load capacity of a piston cylinder Pressure in the rodless chamber of the piston cylinder Pressure in the rod chamber of the piston cylinder Or the displacement of the piston rod. For the transmission to the controller Load capacity of a piston cylinder Pressure in the rodless chamber of the piston cylinder Pressure in the rod chamber of the piston cylinder Or the displacement of the piston rod. For the transmission to the controller Load capacity of a piston cylinder Pressure in the rodless chamber of the piston cylinder Pressure in the rod chamber of the piston cylinder Or the displacement of the piston rod.

[0023] Furthermore, step 2-2 specifically includes:

[0024] Step 2-2-1: Calculate the displacement error;

[0025] Step 2-2-2: Calculate the rate of change of error using the finite difference method according to the following formula. :

[0026] wherein is a sampling period of the displacement sensor, is a first displacement error calculated for the computation, is a second displacement error calculated for the computation; is a third displacement error calculated for the computation; is a fourth displacement error calculated for the computation;

[0027] Step 2-2-3: performing pressure auxiliary check.

[0028] Further, in step 2-2-1, the method of calculating the displacement error comprises:

[0029] the controller compares the filtered actual displacement with the preset target displacement and calculates the displacement error according to the following formula :

[0030] .

[0031] Further, step 2-2-3 specifically comprises:

[0032] according to the filtered pressure of the rodless chamber of the piston cylinder and the filtered pressure of the rod chamber of the piston cylinder , the controller calculates the thrust generated by the piston cylinder according to the piston cylinder data model , and then compares the thrust generated by the piston cylinder with the filtered load force of the piston cylinder , and when , the controller triggers a thrust abnormality warning.

[0033] Further, step 2-3 specifically comprises:

[0034] Step 2-3-1: calculating the sliding mode surface variable, i.e. calculating the sliding mode surface variable according to the following formula based on the displacement error and the error change rate :

[0035] ;

[0036] wherein is a set sliding mode surface parameter;

[0037] Step 2-3-2: solving the control law;

[0038] Step 2-3-3: calculating the total control amount as the adaptive sliding mode control instruction , thereby realizing closed-loop feedback control.

[0039] Further, step 2-3-2 specifically comprises:

[0040] Step 2-3-2-1: Solve the equivalent control law , whose expression is , where is the stiffness coefficient of the piston cylinder.

[0041] Step 2-3-2-2: Solve the switching control law , whose expression is , where the switching gain , and are the set coefficient one and coefficient two, respectively.

[0042] Further, in step 2-3-3, the total control amount is calculated as follows:

[0043] ;

[0044] , where is the voltage adjustment amount corresponding to a unit force; is the voltage adjustment amount corresponding to a unit speed.

[0045] Further, step 3 specifically includes:

[0046] The controller transmits the total control amount , which is the adaptive sliding mode control instruction, to the proportional flow valve provided at the outlet of the hydraulic pump, so that the working voltage of the proportional flow valve is .

[0047] Further, step 4 specifically includes:

[0048] Step 4-1: Calculate the target pressure , whose expression is , where is the required thrust of the piston cylinder under the current working condition;

[0049] Step 4-2: The controller calculates the rodless chamber pressure error of the piston cylinder every 1ms , whose expression is ;

[0050] Step 4-3: Set the adjustment threshold , when , the proportional pressure valve is not adjusted, and the current working current of the proportional pressure valve is maintained, when , the pressure adjustment mechanism is triggered;

[0051] Step 4-4: When the pressure adjustment mechanism is triggered, the controller adjusts the current working current of the proportional pressure valve to , whose calculation equation is

[0052] wherein is the minimum pressure value output by the hydraulic pump, is the maximum pressure value output by the hydraulic pump, is the minimum working current of the proportional pressure valve corresponding to the minimum pressure value output by the hydraulic pump, is the maximum working current of the proportional pressure valve corresponding to the maximum pressure value output by the hydraulic pump.

[0053] Further, the hydraulic system of the thrust hydraulic length adjusting device comprises a piston cylinder of the thrust hydraulic length adjusting device, an oil tank, and a pipeline communicating between the piston cylinder and the oil tank, wherein the pipeline is provided with a hydraulic pump connected with the controller, and the outlet of the hydraulic pump is provided with a proportional flow valve and a proportional pressure valve connected with the controller.

[0054] The beneficial effects of the present application are as follows compared with the prior art:

[0055] Significantly improve the response speed: by adopting advanced adaptive sliding mode control algorithm and constructing closed loop feedback system, the error of the hydraulic system of the thrust hydraulic length adjusting device can be quickly responded, the control strategy is adjusted in real time, so that the thrust hydraulic length adjusting device can quickly reach the target length, the adjustment time is greatly shortened, and the work scene with high response speed requirement is met.

[0056] Effectively improve the adjustment accuracy: the accurate mathematical model can fully consider the influence of various factors on the adjustment accuracy, through real-time monitoring and compensation, the interference of multiple factors is effectively reduced, combined with closed loop feedback control, the high-precision length fine adjustment is realized, and the applicability of the thrust hydraulic length adjusting device in the field with high precision requirement is improved.

[0057] Enhance the robustness of the system: the adaptive sliding mode control algorithm can automatically adjust the control parameters according to the real-time state of the hydraulic system, has strong inhibition ability to the uncertainty and interference of the hydraulic system, enhances the stability and reliability of the hydraulic system under complex working conditions, and improves the overall performance of the thrust hydraulic length adjusting device. BRIEF DESCRIPTION OF DRAWINGS

[0058] Figure 1 is the flow chart of the control method of the thrust hydraulic length adjusting device in the present application. DETAILED DESCRIPTION

[0059] In order to make the objects, technical solutions and advantages of the present application clearer, the following will be combined with the drawings in the embodiments of the present application to perform a clear and complete expression of the technical solutions of the present application. The embodiments expressed in the present application are only a part of the embodiments of the present application, rather than all the embodiments. According to the spirit of the present application, other embodiments obtained by those skilled in the art without creative labor are within the protection scope of the present application.

[0060] As shown in Figure 1 , a control method of a thrust type hydraulic length adjustment device, comprising:

[0061] Step 1: establishing a piston cylinder data model based on a piston rodless cavity area, a rodless cavity pressure, a piston rod cavity area, a rod cavity pressure, a viscous damping coefficient, a piston movement speed, a friction force and a load force of a piston cylinder of the thrust type hydraulic length adjustment device;

[0062] In the preferred but non-limiting embodiments of the present application, in step 1, the expression of the piston cylinder data model is:

[0063] ;

[0064] Wherein is a thrust force generated by the piston cylinder, is the piston rodless cavity area of the piston cylinder, is the rodless cavity pressure of the piston cylinder, is the piston rod cavity area of the piston cylinder, is the rod cavity pressure of the piston cylinder, is the viscous damping coefficient of the piston cylinder, is the piston movement speed of the piston cylinder, is the friction force of the piston cylinder, is the load force of the piston cylinder. Through accurate solving of the piston cylinder data model, the output characteristics of the piston cylinder of the thrust type hydraulic length adjustment device under different working conditions can be accurately predicted, thereby providing a theoretical basis for subsequent control strategy formulation.

[0065] In the preferred but non-limiting embodiments of the present application, in step 1, the viscous damping coefficient of the piston cylinder can be obtained through experiments, the rodless cavity pressure of the piston cylinder is collected by a pressure sensor one connected with the controller and transmitted to the controller, the pressure sensor one is arranged in an oil inlet pipeline of the rodless cavity of the piston cylinder, the rod cavity pressure of the piston cylinder is collected by a pressure sensor two connected with the controller and transmitted to the controller, the pressure sensor two is arranged in an oil inlet pipeline of the rod cavity of the piston cylinder, and the piston movement speed of the piston cylinder The load force of the piston cylinder is collected by a speed sensor connected to the controller and transmitted into the controller, the speed sensor is arranged on the piston rod of the piston cylinder The friction force of the piston cylinder is collected by a tension sensor arranged at the connecting part of the load and the piston cylinder and transmitted into the controller The thrust force generated by the piston cylinder under the condition of no load .

[0066] Step 2: Constructing the closed-loop feedback system of the hydraulic system of the thrust hydraulic length adjustment device and performing closed-loop feedback control;

[0067] In the preferred but non-limiting embodiment of the present application, in step 2, the method for constructing the closed-loop feedback system of the hydraulic system of the thrust hydraulic length adjustment device comprises:

[0068] The displacement sensor connected to the controller is arranged on the piston rod of the piston cylinder of the thrust hydraulic length adjustment device, so that the controller, the proportional flow valve, the proportional pressure valve, the pressure sensor one and the pressure sensor two constitute the closed-loop feedback system of the hydraulic system of the thrust hydraulic length adjustment device, and the displacement sensor collects the displacement of the piston rod and transmits it into the controller.

[0069] The displacement sensor is selected to be a grating displacement sensor or a magnetostrictive displacement sensor with a resolution of ≥0.1 μm and a sampling frequency of ≥1 kHz, to ensure that the high-precision fine adjustment requirement is met. Preferably, a model with an IP67 or above protection level is selected to adapt to the oil stains and dust interference in the industrial environment.

[0070] In the preferred but non-limiting embodiment of the present application, in step 2, the method for performing closed-loop feedback control comprises:

[0071] Step 2-1: Filtering the load force of the piston cylinder, the rodless cavity pressure of the piston cylinder, the rod cavity pressure of the piston cylinder and the displacement of the piston rod transmitted to the controller;

[0072] In the preferred but non-limiting embodiment of the present application, in step 2-1, the load force of the piston cylinder, the rodless cavity pressure of the piston cylinder, the rod cavity pressure of the piston cylinder and the displacement of the piston rod transmitted to the controller are filtered by using an improved second-order Butterworth low-pass filter, the cutoff frequency is set to 50 Hz (displacement) and 100 Hz (pressure and load force), and high-frequency noise generated by the vibration of the hydraulic system of the thrust hydraulic length adjustment device is filtered out. The calculation formula of the improved second-order Butterworth low-pass filter is:

[0073] ;

[0074] Wherein is the first load force of the piston cylinder rodless chamber pressure of the piston cylinder rod chamber pressure of the piston cylinder or displacement of the piston rod, filtered first load force of the piston cylinder rodless chamber pressure of the piston cylinder rod chamber pressure of the piston cylinder or displacement of the piston rod, filtered first load force of the piston cylinder rodless chamber pressure of the piston cylinder rod chamber pressure of the piston cylinder or displacement of the piston rod, transmitted to the controller first load force of the piston cylinder rodless chamber pressure of the piston cylinder rod chamber pressure of the piston cylinder or displacement of the piston rod, transmitted to the controller first load force of the piston cylinder rodless chamber pressure of the piston cylinder rod chamber pressure of the piston cylinder or displacement of the piston rod, transmitted to the controller first load force of the piston cylinder rodless chamber pressure of the piston cylinder rod chamber pressure of the piston cylinder or displacement of the piston rod.

[0075] 0.0234 is the weight of the first and 0.0469 is the weight of the second and satisfies 0.0234+0.0469+0.0234=0.0937, embodying the "low-pass weighting" of the recent signals, i.e. by reducing the weight of high-frequency signals (high-frequency signals change dramatically at adjacent time instants, and are counteracted after weighting), the trend of low-frequency signals is preserved (low-frequency signals change gently at adjacent time instants, and are superimposed and enhanced after weighting).

[0076] Step 2-2: perform multi-dimensional error calculation;

[0077] In the preferred but non-limiting embodiment of the present application, step 2-2 specifically includes:

[0078] Step 2-2-1: calculate displacement error;

[0079] In the preferred but non-limiting embodiment of the present application, in step 2-2-1, the method for calculating the displacement error comprises:

[0080] The controller compares the filtered actual displacement (unit: m) with the preset target displacement (unit: m) and calculates the displacement error according to the following formula:

[0081] .

[0082] Step 2-2-2: Calculate the error change rate by difference method according to the following formula:

[0083] , where is the sampling period of the displacement sensor, is the first displacement error calculated, is the second displacement error calculated; Step 2-2-3: Perform pressure auxiliary verification.

[0084] In the preferred but non-limiting embodiment of the present application, step 2-2-3 specifically comprises:

[0085] According to the filtered pressure of the rodless chamber of the piston cylinder and the pressure of the rod chamber of the piston cylinder

[0086] , the generated thrust of the piston cylinder is calculated in combination with the piston cylinder data model , and then the generated thrust of the piston cylinder is compared with the filtered load force of the piston cylinder , and when , the controller triggers a thrust abnormality warning, i.e., the controller sends a message to the display screen connected thereto to display a thrust abnormality warning. Step 2-3: Generate adaptive sliding mode control instructions.

[0087] In the preferred but non-limiting embodiment of the present application, step 2-3 specifically comprises:

[0088] Step 2-3-1: Calculate the sliding mode surface variable, i.e., based on the displacement error and the error change rate, calculate the sliding mode surface variable according to the following formula:

[0089]

[0090]

[0091] where ​​​​​​For the set sliding surface parameters, the sliding surface parameters are set according to specific requirements, for example may be 10 (unit: 1 / s), reflects the degree of deviation of the hydraulic system from the ideal trajectory;

[0092] Step 2-3-2: Solve the control law;

[0093] In the preferred but non-limiting embodiment of the present application, step 2-3-2 specifically includes:

[0094] Step 2-3-2-1: Solve the equivalent control law , that is, solve it by linearizing the mathematical model, and its expression is , where is the stiffness coefficient of the piston cylinder (calibrated by experiment).

[0095] Step 2-3-2-2: Solve the switching control law , that is, adopt an adaptive gain adjustment strategy, and its expression is , where the switching gain , and are respectively set coefficient one and coefficient two, which can be set according to specific requirements, just as may be 5, may be 0.1, and by increasing in real time, it ensures that the hydraulic system quickly approaches the sliding surface.

[0096] Step 2-3-3: Calculate the total control amount as an adaptive sliding mode control instruction , so as to realize closed-loop feedback control.

[0097] In the preferred but non-limiting embodiment of the present application, in step 2-3-3, the calculation formula of the total control amount is:

[0098] ;

[0099] , where is the voltage adjustment amount corresponding to a unit of force, which is calibrated by experiment (for example, when the load force changes by 1000N, a voltage adjustment of 2V is required, then = 0.002V / N); is the voltage adjustment amount corresponding to a unit of speed, which is calibrated by experiment (for example, when the speed of the piston rod changes by 0.01m / s, a voltage adjustment of 0.1V is required, then = 10VA*s / m).

[0100] Step 3: Perform flow regulation according to the total control amount as an adaptive sliding mode control instruction .

[0101] In the preferred but non-limiting embodiment of the present application, step 3 specifically comprises:

[0102] The controller transmits the total control amount as the adaptive sliding mode control instruction to the proportional flow valve installed at the outlet of the hydraulic pump, so that the working voltage of the proportional flow valve is . Wherein, the flow valve control signal is in a positive proportional relationship with .

[0103] During the flow regulation, when increases, the opening degree of the proportional flow valve increases, and the output flow Q of the hydraulic pump increases linearly according to Q=Qmax×u / 10 (Qmax is the maximum flow of the hydraulic pump), so as to accelerate the movement of the piston cylinder; when u decreases, the flow decreases, and the piston cylinder slows down.

[0104] Step 4: Pressure regulation of the hydraulic pump according to the rodless cavity pressure error of the piston cylinder.

[0105] In the preferred but non-limiting embodiment of the present application, step 4 specifically comprises:

[0106] Step 4-1: Calculate the target pressure , whose expression is: , wherein is the required thrust of the piston cylinder under the current working condition, which is preset according to the load characteristic;

[0107] Step 4-2: The controller calculates the rodless cavity pressure error of the piston cylinder every 1ms , whose expression is: ;

[0108] Step 4-3: In order to avoid frequent regulation, set the error dead zone, so as to set the regulation threshold , the regulation threshold can be set to a data greater than zero according to specific requirements, which ensures that the pressure accuracy is within , that is, can be 0.05MPa, when , the proportional pressure valve is not adjusted, and the current working current of the proportional pressure valve is maintained, when , the pressure regulation mechanism is triggered;

[0109] Step 4-4: When the pressure regulation mechanism is triggered, the controller adjusts the current working current of the proportional pressure valve to , whose calculation equation is:

[0110] , wherein is the minimum pressure value of the hydraulic pump output,​ the maximum pressure value output by the hydraulic pump, the minimum working current of the proportional pressure valve corresponding to the minimum pressure value output by the hydraulic pump, the maximum working current of the proportional pressure valve corresponding to the maximum pressure value output by the hydraulic pump.

[0111] According to the calculation equation, the current working current of the proportional pressure valve can be obtained, so that the proportional pressure valve can be accurately corrected according to the rodless cavity pressure error, and the actual pressure dynamically tracks the target pressure to provide stable thrust for the piston cylinder.

[0112] Through the above specific method, accurate acquisition of sensor signals, efficient execution of control algorithm and accurate adjustment of the hydraulic pump can be realized, the interference of multiple factors is effectively reduced, and finally a stable and reliable closed-loop feedback system is built, which significantly improves the adjustment accuracy and response speed of the device.

[0113] In the preferred but non-limiting embodiment of the application, the hydraulic system of the thrust type hydraulic length adjusting device comprises a piston cylinder of the thrust type hydraulic length adjusting device, an oil tank, and a pipeline communicating between the piston cylinder and the oil tank, the pipeline is provided with a hydraulic pump connected with the controller, and the outlet of the hydraulic pump is provided with a proportional flow valve and a proportional pressure valve connected with the controller. The controller can be a PLC controller.

[0114] The beneficial effects of the application are as follows compared with the prior art:

[0115] Significantly improve the response speed: by adopting the advanced adaptive sliding mode control algorithm and building a closed-loop feedback system, the error of the hydraulic system of the thrust type hydraulic length adjusting device can be quickly responded to, the control strategy can be adjusted in real time, the thrust type hydraulic length adjusting device can quickly reach the target length, the adjustment time is greatly shortened, and the work scene with high response speed requirement is met.

[0116] Effectively improve the adjustment accuracy: the accurate mathematical model can fully consider the influence of various factors on the adjustment accuracy, through real-time monitoring and compensation, the interference of multiple factors is effectively reduced, combined with the closed-loop feedback control, the high-precision length fine adjustment is realized, and the applicability of the thrust type hydraulic length adjusting device in the field with high precision requirement is improved.

[0117] Enhance the robustness of the system: the adaptive sliding mode control algorithm can automatically adjust the control parameters according to the real-time state of the hydraulic system, has strong inhibition ability to the uncertainty and interference of the hydraulic system, enhances the stability and reliability of the hydraulic system under complex working conditions, and improves the overall performance of the thrust type hydraulic length adjusting device.

[0118] It should be pointed out finally that the above embodiments are only used to illustrate the technical solutions of the present application but not to limit it, and although the present application is executed in detail with reference to the above embodiments, it should be understood by those skilled in the art that modifications or equivalent replacements can still be executed to the specific embodiments of the present application without departing from the spirit and scope of the present application, and any modifications or equivalent replacements should be covered in the protection scope of the claims of the present application.

Claims

1. A control method for a thrust-type hydraulic length adjustment device, characterized in that, include: Step 1: Establish a piston cylinder data model based on the piston rodless chamber area, rodless chamber pressure, piston rod chamber area, rod chamber pressure, viscous damping coefficient, piston speed, friction force, and load force of the piston cylinder of the thrust hydraulic length adjustment device. Step 2: Construct a closed-loop feedback system for the hydraulic system of the thrust-type hydraulic length adjustment device and execute closed-loop feedback control; Step 3: Based on the total control quantity used as the adaptive sliding mode control command Adjust the flow rate; Step 4: Adjust the hydraulic pump pressure based on the pressure error in the rodless chamber of the piston cylinder; In step 2, the method for implementing closed-loop feedback control includes: Step 2-1: Filter the load force of the piston cylinder, the pressure in the rodless chamber of the piston cylinder, the pressure in the rod chamber of the piston cylinder, and the displacement of the piston rod transmitted to the controller. Step 2-2: Calculate the multi-dimensional error; Steps 2-3: Generate adaptive sliding mode control commands; In step 2-1, the load force of the piston cylinder, the pressure in the rodless chamber of the piston cylinder, the pressure in the rod chamber of the piston cylinder, and the displacement of the piston rod transmitted to the controller are filtered using an improved second-order Butterworth low-pass filter. The calculation formula for the improved second-order Butterworth low-pass filter is as follows: ； in The filtered first Load capacity of a piston cylinder Pressure in the rodless chamber of the piston cylinder Pressure in the rod chamber of the piston cylinder Or the displacement of the piston rod. The filtered first Load capacity of a piston cylinder Pressure in the rodless chamber of the piston cylinder Pressure in the rod chamber of the piston cylinder Or the displacement of the piston rod. The filtered first Load capacity of a piston cylinder Pressure in the rodless chamber of the piston cylinder Pressure in the rod chamber of the piston cylinder Or the displacement of the piston rod. For the transmission to the controller Load capacity of a piston cylinder Pressure in the rodless chamber of the piston cylinder Pressure in the rod chamber of the piston cylinder Or the displacement of the piston rod. For the transmission to the controller Load capacity of a piston cylinder Pressure in the rodless chamber of the piston cylinder Pressure in the rod chamber of the piston cylinder Or the displacement of the piston rod. For the transmission to the controller Load capacity of a piston cylinder Pressure in the rodless chamber of the piston cylinder Pressure in the rod chamber of the piston cylinder Or the displacement of the piston rod.

2. The control method of the thrust-type hydraulic length adjustment device according to claim 1, characterized in that, In step 1, the expression for the piston cylinder data model is: ； in The thrust generated by the piston cylinder Let be the area of ​​the piston rodless chamber of the piston cylinder. This refers to the pressure in the rodless chamber of the piston cylinder. Let be the piston rod chamber area of ​​the piston cylinder. This refers to the pressure in the rod chamber of the piston cylinder. This is the viscous damping coefficient of the piston cylinder. The piston speed of the piston cylinder. For the friction force of the piston cylinder, The load force on the piston cylinder; In step 1, the pressure in the rodless chamber of the piston cylinder... The pressure sensor, connected to the controller, collects and transmits data to the controller. The pressure sensor is located in the oil inlet pipe of the rodless chamber of the piston cylinder. The pressure in the rod chamber of the piston cylinder is... Pressure sensor two, connected to the controller, collects and transmits data to the controller. Pressure sensor two is located in the oil inlet pipe of the rod chamber of the piston cylinder. The piston movement speed of the piston cylinder... The speed sensor, connected to the controller, collects and transmits data to the controller. The speed sensor is mounted on the piston rod of the piston cylinder. The load force of the piston cylinder... The force is collected and transmitted to the controller by a tension sensor located at the connection between the load and the piston cylinder. The friction force of the piston cylinder is also considered. The thrust generated by the piston cylinder under no-load conditions. .

3. The control method of the thrust-type hydraulic length adjustment device according to claim 2, characterized in that, In step 2, the method for constructing a closed-loop feedback system for the hydraulic system of the thrust-type hydraulic length adjustment device includes: A displacement sensor connected to the controller is installed on the piston rod of the piston cylinder of the thrust hydraulic length adjustment device. Thus, the controller, proportional flow valve, proportional pressure valve, pressure sensor one, and pressure sensor two constitute a closed-loop feedback system of the hydraulic system of the thrust hydraulic length adjustment device. The displacement sensor collects the displacement of the piston rod and transmits it to the controller.

4. The control method of the thrust-type hydraulic length adjustment device according to claim 3, characterized in that, Step 2-2 specifically includes: Step 2-2-1: Calculate the displacement error; Step 2-2-2: Calculate the rate of change of error using the finite difference method according to the following formula. : ,in The sampling period of the displacement sensor. The first one obtained for calculation One displacement error, The first one obtained for calculation One displacement error; Step 2-2-3: Perform pressure-assisted verification.

5. The control method of the thrust-type hydraulic length adjustment device according to claim 4, characterized in that, In step 2-2-1, the method for calculating the displacement error includes: The controller will filter the actual displacement. With respect to the preset target displacement In comparison, the displacement error is calculated according to the following formula. : ； Step 2-2-3 specifically includes: Based on the rodless chamber pressure of the piston cylinder after filtering Pressure in the rod chamber of the piston cylinder The thrust generated by the piston cylinder is calculated by combining the piston cylinder data model. Then the thrust generated by the piston cylinder Load force of the piston cylinder after filtering In contrast, when At that time, the controller triggered a thrust anomaly warning.

6. The control method of the thrust-type hydraulic length adjustment device according to claim 5, characterized in that, Steps 2-3 specifically include: Step 2-3-1: Calculate the sliding surface variables, i.e., based on the displacement error and the rate of change of the error, calculate the sliding surface variables according to the following formula. : ； in The parameters of the sliding surface are set; Step 2-3-2: Solve for the control law; Step 2-3-3: Calculate the total control quantity as the adaptive sliding mode control command. This achieves closed-loop feedback control; Step 2-3-2 specifically includes: Step 2-3-2-1: Solve for the equivalent control law Its expression is ,in This is the stiffness coefficient of the piston cylinder; Step 2-3-2-2: Solve the switching control law Its expression is In which the gain is switched , and These are the set coefficient one and coefficient two, respectively; In step 2-3-3, the total control quantity The calculation formula is: ； in This represents the voltage adjustment amount corresponding to a unit force. This represents the voltage adjustment per unit speed.

7. The control method for the thrust-type hydraulic length adjustment device according to claim 6, characterized in that, Step 3 specifically includes: The controller will serve as the total control quantity for the adaptive sliding mode control command. A proportional flow valve is installed at the outlet of the hydraulic pump, thereby ensuring that the operating voltage of the proportional flow valve is [value missing]. ; Step 4 specifically includes: Step 4-1: Calculate the target pressure Its expression is: ,in This represents the thrust required by the piston cylinder under current operating conditions. Step 4-2: The controller calculates the rodless chamber pressure error of the piston cylinder every 1ms. Its expression is: ; Step 4-3: Set the adjustment threshold ,when At this time, the proportional pressure valve is not adjusted, and the current operating current of the proportional pressure valve is maintained. At that time, the pressure regulation mechanism is triggered; Step 4-4: When the pressure regulation mechanism is triggered, the controller adjusts the current operating current of the proportional pressure valve to... The calculation equation is as follows: ,in This is the minimum pressure value output by the hydraulic pump. This represents the maximum pressure output by the hydraulic pump. This refers to the minimum operating current of the proportional pressure valve corresponding to the minimum pressure value output by the hydraulic pump. This refers to the maximum operating current of the proportional pressure valve corresponding to the maximum pressure value output by the hydraulic pump.

8. The control method of the thrust-type hydraulic length adjustment device according to claim 7, characterized in that, The hydraulic system of the thrust-type hydraulic length adjustment device includes a piston cylinder, an oil reservoir, and a pipeline connecting the piston cylinder and the oil reservoir. A hydraulic pump connected to a controller is installed on the pipeline, and a proportional flow valve and a proportional pressure valve connected to the controller are installed at the outlet of the hydraulic pump.

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