A system and method for compensating for hydraulic cylinder synchronization error in an automatic leveling control

Abstract

The present application relates to a kind of compensation system and method for hydraulic cylinder synchronization error in automatic leveling control, belong to automatic leveling control technical field, solve the problem that leveling oil cylinder in prior art is out of sync when executing simultaneously stretch action, leveling system repeatedly adjusts output, causes the timeout of leveling time Even unable to complete leveling action.The present application includes control unit, acquisition unit and execution unit, the acquisition unit is used to acquire the rodless chamber pressure value of leveling oil cylinder, the control unit obtains delay compensation time based on the pressure value acquired by the acquisition unit, the execution unit is based on the delay compensation time to engineering vehicle leveling.The present application compensates the proportional speed regulating valve switching time error, realizes the synchronous action of leveling oil cylinder, finally without increasing system component, realizes the fast and accurate completion of leveling action of leveling system, avoids the occurrence of system overshoot and other unstable conditions.

Description

Technical Field

[0001] This invention relates to the field of automatic leveling control technology, and in particular to a compensation system and method for hydraulic cylinder synchronization error in automatic leveling control. Background Technology

[0002] Engineering vehicle leveling systems are generally divided into two categories: manual leveling systems and automatic leveling systems. Manual leveling systems are controlled manually, are low-cost, and suitable for applications with lower requirements for leveling accuracy and stability. Automatic leveling systems use a controller program to complete the leveling process and are suitable for applications with higher leveling accuracy requirements and time constraints.

[0003] The leveling of engineering vehicles is divided into three stages: leveling cylinder contact with the ground, wheel lifting, and vehicle body leveling. In vehicle body leveling control, at certain stages, it is necessary to keep two leveling cylinders operating simultaneously to ensure that the lateral or longitudinal leveling values ​​fall within a specified range. The synchronicity of the simultaneous operation of the two cylinders directly affects whether the leveling task for the current stage can be completed after synchronized action.

[0004] However, due to limitations in the manufacturing process and machining precision of proportional speed control valves, individual differences in their switching time characteristics are inevitable. These differences ultimately lead to asynchrony when two or more leveling cylinders extend simultaneously, causing the leveling system to repeatedly adjust its output, resulting in timeouts or even failure to complete the leveling action. Summary of the Invention

[0005] Based on the above analysis, the present invention aims to provide a compensation system and method for the synchronization error of hydraulic cylinders in automatic leveling control, in order to solve the problem that existing leveling cylinders are out of sync when performing simultaneous extension actions, causing the leveling system to repeatedly adjust the output, resulting in timeouts or even failure to complete the leveling action.

[0006] On one hand, the present invention provides a compensation system for synchronization error of hydraulic cylinder in automatic leveling control, including a control unit, a data acquisition unit and an execution unit. The data acquisition unit is used to acquire the pressure value of the rodless chamber of the leveling cylinder. The control unit obtains a delay compensation time based on the pressure value acquired by the data acquisition unit. The execution unit levels the engineering vehicle based on the delay compensation time.

[0007] Furthermore, the execution unit includes a proportional valve control board, a proportional speed control valve, and the leveling cylinder. After obtaining delay compensation, the control unit outputs a control signal from the proportional valve control board. The control signal is amplified by the proportional valve control board and then loaded onto the proportional speed control valve to control the opening and closing action of the proportional speed control valve. The opening and closing action of the proportional speed control valve controls the extension of the leveling cylinder, thus executing the leveling extension action of the leveling cylinder.

[0008] Furthermore, the acquisition unit is a pressure sensor, which acquires the pressure value of the rodless chamber of the leveling cylinder as a judgment condition for the leveling process.

[0009] Furthermore, the control unit includes an AD module and a DA module. The DA module is used to automatically control the proportional speed control valve through the proportional valve control board, and the AD board module can perform AD conversion of the pressure value collected by the leveling cylinder.

[0010] Furthermore, the control unit calls the acquisition function through the delay parameter setting function and calculates to obtain the delay parameter. The acquisition function is used to acquire the pressure sensor value, and the signal change of the pressure value is used as the input of the delay parameter setting function.

[0011] Furthermore, the specific working steps of the delay parameter setting function are as follows:

[0012] S1: Clear the delay parameter;

[0013] S2: Call the acquisition function to acquire pressure sensor values;

[0014] S3: Increment the delay parameter by 1;

[0015] S4: Wait 10ms;

[0016] S5: Check if press[i] > presslim is true. If it is true, exit the loop and execute S6. Otherwise, repeat S2 to S5.

[0017] Where press[i] is the collected pressure sensor value, and presslim is the pressure variation threshold value obtained from the friction test of the leveling cylinder;

[0018] S6: Returns the function's return value, i.e., obtains the delay parameter.

[0019] On the other hand, the present invention provides a method for compensating for hydraulic cylinder synchronization errors in automatic leveling control, employing the aforementioned compensation system for hydraulic cylinder synchronization errors in automatic leveling control, the steps of which include:

[0020] The pressure value of the rodless chamber of the leveling cylinder is collected by a pressure sensor, and the signal change of the pressure value is used as the input of the delay parameter setting function.

[0021] The delay parameter value is calculated using the delay parameter setting function, and the actual delay value is obtained based on the delay parameter.

[0022] Based on the actual delay value, the leveling cylinder is made to extend with an additional delay during the start-up phase.

[0023] Furthermore, the feature is that the specific steps include:

[0024] Step 1: The pressure sensor collects the pressure value of the rodless chamber of the leveling cylinder. The collected pressure value is converted into a DC voltage signal of 0 to 10V. The signal change of the pressure value is used as the input of the delay parameter setting function.

[0025] Step 2: After receiving the external input leveling signal, the control unit obtains the actual delay value and controls the execution unit to perform the leveling task.

[0026] Furthermore, step 2 specifically includes the following steps:

[0027] Step 2.1: Obtain the delay compensation value of the leveling cylinder during the ground contact stage;

[0028] Step 2.2: The four leveling cylinders extend rapidly at full speed, causing the wheels to lift.

[0029] Step 2.3: The leveling cylinder performs a compensation action by multiplying the delay compensation value obtained during the ground contact phase by 10ms.

[0030] Furthermore, in step 2.1, the delay compensation value is equal to the difference between the maximum switching time of the proportional speed control valve and k times the delay parameter, where k is the time coefficient.

[0031] Compared with the prior art, the present invention can achieve at least one of the following beneficial effects:

[0032] (1) The present invention compensates for the switching time error of the proportional speed control valve, realizes the synchronous action of the leveling cylinder, and finally achieves the leveling system to complete the leveling action quickly and accurately without adding system components, thus avoiding the occurrence of instability such as system overshoot.

[0033] (2) This invention achieves the synchronous action of the hydraulic cylinder by adaptively delaying the proportional speed control valve with different switching characteristics, thereby realizing the fast and accurate leveling of the leveling system.

[0034] (3) The present invention adopts a hydraulic cylinder synchronization error compensation method in automatic leveling control, which improves the synchronization of two or more cylinders extending at the same time, avoids the problem of repeatedly adjusting the output mode during the leveling stage, shortens the leveling time, and improves the stability of the system.

[0035] (4) The present invention compensates for the differences in the switching characteristics of different proportional speed control valves, improves the synchronization of the actuator in synchronous control, shortens the adjustment time, and improves the stability of the system.

[0036] (5) The present invention achieves delay compensation, improves the synchronization of the actuator, and shortens the leveling task time by comparing the characteristics of the switching characteristics of the proportional speed control valve without increasing hardware costs.

[0037] In this invention, the above-described technical solutions can be combined with each other to achieve more preferred combinations. Other features and advantages of this invention will be set forth in the following description, and some advantages may become apparent from the description or be learned by practicing the invention. The objects and other advantages of this invention can be realized and obtained from what is particularly pointed out in the description and drawings. Attached Figure Description

[0038] The accompanying drawings are for illustrative purposes only and are not intended to limit the invention. Throughout the drawings, the same reference numerals denote the same parts.

[0039] Figure 1 The diagram shows the control relationship of the hydraulic cylinder synchronization error compensation system in the automatic leveling control of a specific embodiment.

[0040] Figure 2 This is a flowchart of the control system for compensating for synchronization errors of hydraulic cylinders in the automatic leveling control of a specific embodiment. Detailed Implementation

[0041] The preferred embodiments of the present invention will now be described in detail with reference to the accompanying drawings, which constitute a part of the present invention and are used together with the embodiments of the present invention to illustrate the principles of the present invention, but are not intended to limit the scope of the present invention.

[0042] In the description of the embodiments of the present invention, it should be noted that, unless otherwise explicitly specified and limited, the term "connected" should be interpreted broadly. For example, it can refer to a fixed connection, a detachable connection, or an integral connection; it can be a mechanical connection or an electrical connection; it can be a direct connection or an indirect connection through an intermediate medium. Those skilled in the art can understand the specific meaning of the above terms in the present invention according to the specific circumstances.

[0043] Throughout the text, the terms “top,” “bottom,” “above,” “below,” and “on top” refer to the relative positions of components of the device, such as the relative positions of the top and bottom substrates within the device. It is understood that the device is multifunctional and independent of its spatial orientation.

[0044] Example 1

[0045] A specific embodiment of the present invention, such as Figure 1As shown, a compensation system for synchronization error of hydraulic cylinders in automatic leveling control (hereinafter referred to as the compensation system) is disclosed. The automatic leveling system of the engineering vehicle is an electro-hydraulic control system. The compensation system includes a control unit, a data acquisition unit, and an execution unit. The data acquisition unit is used to acquire the pressure value of the rodless chamber of the leveling cylinder. The control unit obtains a delay compensation time based on the pressure value acquired by the data acquisition unit. The execution unit levels the engineering vehicle based on the delay compensation time.

[0046] Compared with the prior art, in this embodiment, the pressure value of the leveling cylinder is obtained by the acquisition unit, and the control unit calculates the delay compensation time based on the pressure value of the rodless chamber. When the vehicle is leveled, the leveling cylinders extend and retract according to their respective delay compensation times to compensate for the opening and closing time error of the proportional speed control valve, thereby realizing the synchronous action of the leveling cylinders. Finally, without adding system components, the leveling system can quickly and accurately complete the leveling action, avoiding the occurrence of instability such as system overshoot.

[0047] The execution unit includes a leveling cylinder, a hydraulic oil source, a hydraulic valve, and a proportional valve control board.

[0048] The leveling cylinders are used to perform the leveling and retraction actions of the engineering vehicle body. Specifically, they include the left front leveling cylinder, the right front leveling cylinder, the left rear leveling cylinder, and the right rear leveling cylinder, and the four leveling cylinders are arranged symmetrically.

[0049] The hydraulic oil is supplied by the hydraulic system pump station.

[0050] Hydraulic valves include proportional relief valves, general directional valves, and proportional speed control valves. The proportional relief valve is used to control the pressure of the hydraulic system, the general directional valve is used to control the direction of movement of the leveling cylinder, and the proportional speed control valve is used to control the speed of movement of the leveling cylinder. Specifically, the speed of movement of the leveling cylinder is controlled by changing the flow rate of hydraulic oil through the proportional speed control valve.

[0051] The proportional valve control board is used to receive control signals output from the control unit and work with the proportional speed control valve to achieve stepless speed regulation control of the output flow.

[0052] The acquisition unit is a pressure sensor. The pressure sensor acquires the pressure value of the rodless chamber of the leveling cylinder as a judgment condition for the leveling process. At the same time, the acquired pressure value is interpreted by the program to generate a delay setting value.

[0053] The control unit can acquire input signals (i.e., leveling commands from the outside to the control unit, which can be input via buttons or keyboard), output leveling control signals to the ordinary directional valve, and output delay compensation time control signals obtained based on the pressure values ​​acquired by the acquisition unit to the proportional valve control board to complete the automatic leveling task.

[0054] The control unit provides the operating environment for the engineering vehicle control software and specifically includes an AD module, a DA module, a CPU control module, and an I / O module. Communication and control functions with other onboard devices are achieved through the human-machine interface, communication board, I / O module, AD module, and DA module.

[0055] Specifically, the CPU control module serves as the central hub of the control unit, and the control software for the engineering vehicle is embedded in the electronic disk of the CPU control module, which is used to control the functions required by the engineering vehicle.

[0056] The DA module is used to achieve automatic control of the proportional speed control valve through the proportional valve control board; it outputs 6 channels of double-ended opto-isolated analog output signals from 0V to +10V.

[0057] The AD module can perform AD conversion of the pressure values ​​acquired by the leveling cylinder; the analog input signal is 0V to +10V; isolation is required between inputs; the resolution is 12 bits; the conversion accuracy is ±3LSB; and the conversion time is no more than 1ms. It should be noted that the isolation is optocoupler isolation, the purpose of which is to prevent sudden changes in the output signal from damaging internal components.

[0058] The IO module has switch output capability and can control the corresponding relay in the controller according to the instructions of the control software, so as to control the engineering vehicle to complete the corresponding automatic control function; Output voltage: DC 24V (meets the requirements of 24V, 0.5A inductive load); Output current: 0.5A; Output signal characteristics: When each channel outputs a signal alone, it will not interfere with the status of other output signals.

[0059] In this embodiment, the leveling of the engineering vehicle is divided into three stages: the leveling cylinder (i.e., the outrigger in the traditional sense) touching the ground stage, the wheel lifting stage, and the vehicle body leveling stage.

[0060] Specifically: Leveling cylinder ground contact stage: The control unit controls the four leveling cylinders to extend simultaneously, and judges the leveling cylinders to touch the ground according to the preset pressure value. When a single leveling cylinder completes the ground contact judgment, it stops extending until all four leveling cylinders touch the ground, thus completing the leveling cylinder ground contact operation.

[0061] It should be noted that during the leveling cylinder's contact with the ground stage, the pressure sensor acquires the pressure value of the rodless chamber of the leveling cylinder in real time and compares it with the preset pressure value. When the acquired pressure value is greater than the preset pressure value, it indicates that the leveling cylinder has contacted the ground.

[0062] Wheel lifting phase: The four leveling cylinders extend at maximum speed to complete the wheel lifting operation. Wheel lifting is achieved by the simultaneous movement of all four leveling cylinders at the same speed.

[0063] Vehicle leveling stage: First, adjust the horizontal level of the front of the vehicle and the longitudinal and lateral level of the rear of the vehicle to the specified angle. When the horizontal level of the front of the vehicle does not meet the requirements, only the two leveling cylinders at the front of the vehicle will operate. Second, adjust the longitudinal and lateral level of the rear of the vehicle to the specified angle. When the horizontal level of the rear of the vehicle does not meet the requirements, only the two leveling cylinders at the rear of the vehicle will operate.

[0064] In vehicle body leveling control, at certain stages, it is necessary to keep two leveling cylinders operating simultaneously to ensure that the lateral or longitudinal leveling values ​​fall within a specified range. The synchronicity of the simultaneous operation of the two leveling cylinders directly affects whether the current leveling task can be completed after the synchronized operation.

[0065] The control unit uses the VxWorks embedded real-time operating system and employs a modular design to achieve automatic control of each component of the system.

[0066] The software application layer functions of the control unit mainly include the entry file user.c, the leveling file tp.c, and the acquisition file workoften.c.

[0067] The entry file user.c collects the status of each port in the system and initiates action tasks. The initiated tasks perform the leveling operation by calling the corresponding control function in the leveling file tp.c.

[0068] The balancing file tp.c mainly contains the balancing execution function auto_balance_leg, the output function output, and the delay parameter setting function Time.

[0069] During the execution of the leveling function `auto_balance_leg`, the acquisition function `Ad_in` in the acquisition file `workoften.c` is called to acquire the pressure value of the rodless chamber of the leveling cylinder obtained by the pressure sensor, which is then used for leveling control. Finally, through corresponding calculations, the leveling speed is output through the leveling output function `output`.

[0070] The delay parameter setting function `Time` calls the acquisition function `Ad_in` and returns the delay parameter `count` through calculation. The specific steps of the delay parameter setting function `Time` are as follows:

[0071] S1: Clear the delay parameter, i.e., count[i] = 0.

[0072] S2: Call the acquisition function Ad_in to acquire pressure sensor values.

[0073] S3: Increment the delay parameter by 1, i.e., count[i] = count[i] + 1.

[0074] S4: Set the function delay taskDelay(1), which is set to 10ms according to the system settings, meaning wait for 10ms. It should be noted that in taskDelay(1), the 1 in parentheses refers to 10ms.

[0075] S5: Determine if the condition press[i] > presslim for stopping the counting of the delay parameter is true. If it is true, exit the loop and execute S6. Otherwise, repeat S2 to S5.

[0076] Where press[i] is the collected pressure sensor value, and presslim is the pressure variation threshold value obtained from the cylinder friction test.

[0077] S6: Returns the function's return value count[i], which is the delay parameter.

[0078] It should be noted that clearing the delay parameter count to zero is for variable initialization, preventing old values ​​stored in the system from affecting the function's return error value.

[0079] Example 2

[0080] Another specific embodiment of the present invention discloses a method for compensating for hydraulic cylinder synchronization errors in automatic leveling control. It employs the hydraulic cylinder synchronization error compensation system of Embodiment 1, which uses a pressure sensor to collect the pressure value of the rodless chamber of the leveling cylinder and uses the signal change of the pressure value as the input to the delay parameter setting function Time. During the operation of the compensation system, the delay function is called to return the delay parameter count[i], which is then calculated to form the actual delay value T[i]. When executing the output function output, the actual delay value T[i] is called, increasing the delay during the extension start-up phase of the i-th leveling cylinder. The increased delay in the proportional speed control valve output compensates for the switching time error caused by the difference in the switching characteristics of the proportional speed control valve, thereby achieving compensation for hydraulic cylinder synchronization errors in automatic leveling control.

[0081] The specific steps include:

[0082] Step 1: Power supply to each unit, specifically, power supply to the acquisition unit, control unit and execution unit.

[0083] The pressure sensor collects the pressure value of the rodless chamber of the leveling cylinder to determine whether the four leveling cylinders are stably in contact with the ground during vehicle body leveling. During the initial movement of the leveling cylinder, it needs to overcome static friction to extend. The pressure value of the rodless chamber of the leveling cylinder will fluctuate briefly, and the pressure sensor can effectively collect this pressure fluctuation. The collected pressure value is converted into a 0-10V DC voltage signal, and then converted into a 0-2048 digital signal by the AD module, which is then read by the CPU control module and stored in the parameter press[i].

[0084] Step 2: After receiving the external input leveling signal, the control unit calls the leveling function through the entry function to perform the leveling task.

[0085] Step 2.1: Obtain the actual delay value T[i] of the leveling cylinder during the ground contact stage.

[0086] First, the leveling cylinder rapidly extends. During this process, the delay parameter setting function `Time` is called. The function returns the delay parameter `count[i]`, which is an integer representing the number of cycles for pressure condition reading with a period of 10ms, characterizing the proportional speed control valve's opening and closing delay error. Then, the actual delay value `T[i]` of the `i`-th leveling cylinder is calculated using the formula `T[i] = Tmax - k * count[i]`. Here, `Tmax` is the maximum opening and closing time of the proportional speed control valve, and `k` is the time coefficient.

[0087] It should be noted that the value of k is a decimal between 0 and 1. When k = 0, it means no compensation; when k = 1, it means maximum compensation. The value of k depends on the desired degree of compensation to the system.

[0088] Step 2.2: Wheel lifting: The four leveling cylinders extend at full speed to complete the wheel lifting operation.

[0089] Step 2.3: Level the vehicle body.

[0090] Based on the delay compensation value T[i] calculated in step 2.1, the leveling cylinder performs a delay of 10ms*T[i] when it is activated.

[0091] After obtaining the actual delay value, the proportional valve control board outputs a control signal. The control signal is amplified by the proportional valve control board and then applied to the proportional speed control valve to control the opening and closing of the proportional speed control valve. The opening and closing of the proportional speed control valve controls the extension of the leveling cylinder, thus executing the leveling extension action of the leveling cylinder i.

[0092] The leveling process is completed when the leveling conditions are met, i.e., the leveling angle is less than 30 minutes.

[0093] Due to manufacturing errors, proportional speed control valves exhibit individual variations in their switching characteristics. When receiving a synchronous switching signal, the valves may react at different times, resulting in a time lag. By employing the aforementioned synchronous control compensation method, this time lag caused by the proportional speed control valve's switching characteristics can be effectively reduced, thereby compensating for the synchronization error of the hydraulic cylinder.

[0094] Compared with the prior art, the method of this embodiment improves the synchronicity of the simultaneous extension of two or more hydraulic cylinders, avoids the problem of repeatedly adjusting the output mode during the leveling stage, shortens the leveling time, and improves the stability of the system.

[0095] This invention addresses the problems of system overshoot and excessively long leveling time caused by synchronization errors in existing leveling systems. It compensates for the switching time error of the speed control valve, realizes the synchronous action of the leveling cylinder, and ultimately achieves fast and accurate leveling without adding system components, thus avoiding instability such as system overshoot.

[0096] Those skilled in the art will understand that all or part of the processes of the methods described in the above embodiments can be implemented by a computer program instructing related hardware, and the program can be stored in a computer-readable storage medium. The computer-readable storage medium may be a disk, optical disk, read-only memory, or random access memory, etc.

[0097] The above description is only a preferred embodiment of the present invention, but the scope of protection of the present invention is not limited thereto. Any changes or substitutions that can be easily conceived by those skilled in the art within the scope of the technology disclosed in the present invention should be included within the scope of protection of the present invention.

Claims

1. A compensation system for synchronization error of hydraulic cylinders in automatic leveling control, characterized in that, The system includes a control unit, a data acquisition unit, and an execution unit. The data acquisition unit acquires the pressure value of the rodless chamber of the leveling cylinder. The control unit obtains a delay compensation time based on the pressure value acquired by the data acquisition unit. The execution unit levels the engineering vehicle based on the delay compensation time. The execution unit includes a proportional valve control board, a proportional speed control valve, and the leveling cylinder. After obtaining the delay compensation, the control unit outputs a control signal to the proportional valve control board. The control signal is amplified by the proportional valve control board and applied to the proportional speed control valve to control its opening and closing action. The opening and closing action of the proportional speed control valve controls the extension of the leveling cylinder, thus executing the leveling extension action of the leveling cylinder. The data acquisition unit is a pressure sensor that acquires the pressure value of the rodless chamber of the leveling cylinder as a judgment condition for the leveling process. The control unit calls the data acquisition function through a delay parameter setting function and calculates the delay parameter to obtain the delay parameter. The data acquisition function acquires the pressure sensor value, and the signal change of the pressure value is used as the input of the delay parameter setting function. The specific working steps of the delay parameter setting function are: S1: Clear the delay parameter to zero. S2: Call the acquisition function to acquire the pressure sensor value; S3: Increment the delay parameter by 1; S4: Wait for 10ms; S5: Check if press[i] > presslim is true. If true, exit the loop and execute S6. Otherwise, repeat S2~S5. Where press[i] is the acquired pressure sensor value, and presslim is the pressure variation threshold value obtained from the friction test of the leveling cylinder; S6: Return the function return value, that is, obtain the delay parameter.

2. The compensation system for hydraulic cylinder synchronization error in automatic leveling control according to claim 1, characterized in that, The control unit includes an AD module and a DA module. The DA module is used to automatically control the proportional speed control valve through the proportional valve control board, and the AD module can perform AD conversion of the pressure value collected by the leveling cylinder.

3. A method for compensating for synchronization errors of hydraulic cylinders in automatic leveling, characterized in that, The automatic leveling control system for compensating for hydraulic cylinder synchronization errors according to any one of claims 1-2 comprises the following steps: The pressure value of the rodless chamber of the leveling cylinder is collected by a pressure sensor, and the signal change of the pressure value is used as the input of the delay parameter setting function. The delay parameter value is calculated using the delay parameter setting function, and the actual delay value is obtained based on the delay parameter. Based on the actual delay value, the leveling cylinder is made to extend with an additional delay during the start-up phase.

4. The method for compensating for synchronization errors of hydraulic cylinders in automatic leveling according to claim 3, characterized in that, The specific steps include: Step 1: The pressure sensor collects the pressure value of the rodless chamber of the leveling cylinder. The collected pressure value is converted into a DC voltage signal of 0 to 10V. The signal change of the pressure value is used as the input of the delay parameter setting function. Step 2: After receiving the external input leveling signal, the control unit obtains the actual delay value and controls the execution unit to perform the leveling task.

5. The method for compensating for synchronization errors of hydraulic cylinders in automatic leveling according to claim 4, characterized in that, Step 2 specifically includes the following steps: Step 2.1: Obtain the delay compensation value of the leveling cylinder during the ground contact stage; Step 2.2: The four leveling cylinders extend rapidly at full speed, causing the wheels to lift. Step 2.3: The leveling cylinder performs a compensation action by multiplying the delay compensation value obtained during the ground contact phase by 10ms.

6. The method for compensating for synchronization errors of hydraulic cylinders in automatic leveling according to claim 5, characterized in that, In step 2.1, the delay compensation value is equal to the difference between the maximum opening and closing time of the proportional speed control valve and k times the delay parameter, where k is the time coefficient.

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