Six-degree-of-freedom hydraulic leveling system for vehicle-mounted equipment

Abstract

The invention belongs to the field of hydraulic control, and particularly relates to a six-degree-of-freedom hydraulic leveling system for vehicle-mounted equipment, which can ensure the stability and maneuverability of the equipment in the operation process. The six-degree-of-freedom hydraulic leveling system is designed for solving the problems that a vehicle-mounted equipment leveling system is slow in response, low in precision and the like. According to the system, the telescopic motion of the hydraulic supporting legs is controlled through a self-adaptive PID algorithm based on speed feedforward, and position closed-loop control is achieved by combining displacement and real-time feedback of a double-shaft tilt angle sensor. A leveling strategy of first X-axis leveling and then Y-axis leveling is adopted, combination of coarse adjustment and fine adjustment is achieved through staged leveling, and the leveling efficiency is greatly improved. According to the test under a real heavy-load vehicle-mounted platform, the result shows that the biaxial inclination of the vehicle-mounted platform can be smaller than or equal to 0.05 degree within 150 seconds, the leveling time is effectively shortened, the precision is higher, and the actual engineering application requirement is met.

Description

Technical Field

[0001] This invention patent belongs to the field of hydraulic control. Specifically, it is a six-degree-of-freedom hydraulic leveling system for vehicle-mounted equipment, which can ensure the stability and mobility of the equipment during operation. Background Technology

[0002] In recent years, my country's military industry and industrial technology have achieved rapid development, and various large-scale equipment has been widely used. In order to adapt to complex and ever-changing operating scenarios and improve the rapid response capability of operating equipment, many weapons and equipment are mounted on vehicle-mounted platforms and combined with transport vehicles to form vehicle-mounted equipment. Moreover, most of these operating equipment need to be kept in a horizontal position to operate normally.

[0003] When designing a vehicle-mounted equipment leveling system, the following three aspects are the main focus: First, high leveling accuracy is required, ensuring the vehicle platform has a high degree of levelness after leveling. Second, short leveling time is essential, meaning the time for leveling deployment and retraction must be minimized to ensure the mobility of the vehicle-mounted equipment during operation. Third, the leveling system must be stable, ensuring the safety of personnel and equipment entering the work area; the system should avoid situations such as false starts or platform instability. Existing leveling control systems, while meeting high accuracy requirements, suffer from long leveling times, making it impossible to simultaneously satisfy both mobility and high precision requirements. Summary of the Invention

[0004] Based on this, this patent develops a six-degree-of-freedom hydraulic leveling system for vehicle-mounted equipment. Leveraging the advantages of hydraulic systems, such as large load capacity, fast response speed, and high precision, the leveling process is completed by driving hydraulic cylinders.

[0005] To overcome the shortcomings of the aforementioned technical problems, this invention patent proposes a six-degree-of-freedom hydraulic leveling system for vehicle-mounted equipment. It controls the extension and retraction of hydraulic outriggers using a velocity-feedforward-based adaptive PID algorithm, and achieves closed-loop position control by combining real-time feedback from displacement and dual-axis tilt sensors. Employing a leveling strategy that prioritizes the X-axis before the Y-axis, it combines coarse and fine adjustments through staged leveling, thereby improving leveling efficiency.

[0006] According to one aspect of this application, a six-degree-of-freedom hydraulic leveling system for vehicle-mounted equipment is provided, including outrigger 1, outrigger 2, outrigger 3, outrigger 4, outrigger 5, outrigger 6, hydraulic station and valve group 7, tilt sensor 8, leveling controller 9, and chassis 10.

[0007] Among them, support legs 1, 2, 3, and 4 are the main support legs, and support legs 5 and 6 are the auxiliary support legs.

[0008] The outriggers 3 and 4 are installed at the two corners of the chassis 10 away from the front of the vehicle, the outriggers 5 and 6 are installed at the two corners of the chassis 10 close to the front of the vehicle, and the outriggers 1 and 2 are installed on the side of the chassis 10 along the direction the front of the vehicle is pointing. The center of the rectangle formed by the outriggers 1, 2, 3, and 4 is the center of gravity of the chassis 10.

[0009] The outriggers 1, 2, 3, 4, 5, and 6 are all hydraulic outriggers, and are connected to displacement sensors and pressure sensors.

[0010] The tilt sensor 8 is installed at the center of gravity of the chassis 10 and is used to detect the tilt angle in the horizontal and vertical directions in real time.

[0011] The six-degree-of-freedom hydraulic leveling system for vehicle-mounted equipment uses an adaptive PID control algorithm based on speed feedforward to control the movement of the outriggers through the hydraulic station and valve group 7, thereby achieving closed-loop control of the outrigger position and thus achieving leveling.

[0012] The adaptive PID control algorithm based on velocity feedforward is as follows:

[0013] S1: Determine the coordinates of each outrigger;

[0014] S2: Obtain the actual tilt angle of the X-axis by acquiring the tilt sensor 8. Actual tilt angle of the Y-axis Displacement data of each outrigger is obtained through displacement sensors, and pressure data of the rodless cavity of each outrigger is obtained through pressure sensors.

[0015] S3: The displacement data of each outrigger and the pressure data of the rodless chamber obtained in S2 are converted into digital signals by the analog-to-digital converter in the leveling controller 9, and the digital signals are preprocessed.

[0016] S4: Based on the preprocessing results of S3, power is provided by the hydraulic station and valve group 7, and the leveling controller 9 controls each outrigger to begin leveling, first performing coarse adjustment, and then fine adjustment, until the desired level is achieved. and When the stopping condition is met, the leveling ends, and at this point, it can be considered that chassis 10 has been leveled.

[0017] In S1:

[0018] Establish a horizontal coordinate system OXYZ and a chassis coordinate system OX'Y'Z' with the lowest outrigger's fulcrum as the origin. The position coordinates of each outrigger's fulcrum in the horizontal coordinate system OXYZ are (x...). i , y i , z i ) TIn the chassis coordinate system OX'Y'Z', the coordinates of the support points of each outrigger are respectively (x... i ', y i ', 0) T , where i is 1, 2, 3, 4, 5, or 6;

[0019] The leveling process involves rotating the chassis coordinate system OX'Y'Z' around the X-axis by α and around the Y-axis by β until it coincides with the horizontal coordinate system OXYZ. The corresponding transformation matrices for the X-axis and Y-axis are shown in equations (1) and (2):

[0020] (1)

[0021] (2)

[0022] The total transformation matrix is ​​shown in equation (3):

[0023] (3)

[0024] The coordinates of the fulcrum of each leg after the transformation are shown in equation (4):

[0025] (4).

[0026] Generally speaking, the tilt angle is very small, so the coordinates of each leg support point in the horizontal coordinate system can be approximated as equation (5).

[0027] (5).

[0028] In step S3, the preprocessing includes the following steps:

[0029] S31: Use an arithmetic average filter and transmit the digital signal as the valid output value at that moment to the application layer.

[0030] S32: A two-step differential filter based on 2σ outlier removal is proposed. Outliers are removed within a fixed time window by twice the standard deviation, and the mean of that time window is taken. Then, a maximum allowable deviation Δ is set between sampling points in two adjacent fixed time windows. When acquiring a new sample value, two conditions must be simultaneously checked: whether the absolute value of the difference between the current sample value and the previous sample value, and the absolute value of the difference between the previous sample value and the sample value before that, are both greater than Δ. Only when both exceed Δ is it determined that the signal has undergone a real change; otherwise, the original signal value is maintained, and the mean of the remaining sampling points is finally output.

[0031] The mean value here is the average value of the displacement data of each outrigger and the pressure data of the rodless cavity within a fixed time window after removing data with large deviations.

[0032] S4 includes the following process:

[0033] S41: Based on the displacement data of each outrigger obtained in S32, the error between the current displacement and the planned displacement is calculated using a PID algorithm, and the opening of the valve group is controlled. The PID algorithm is as shown in equation (6):

[0034] (6)

[0035] in This indicates the valve opening degree, i.e., the control speed. Setting values ​​for outrigger displacement Actual output of outrigger displacement The error, i.e. , This represents the base velocity of the i-th outrigger, the value of which is obtained through calibration. , , , These represent proportional, integral, derivative, and velocity feedforward coefficients, respectively.

[0036] S42: When the rodless chamber pressure data of a certain outrigger rises sharply, it indicates that the outrigger has touched the ground. At this time, the opening of the valve group of that outrigger needs to be reduced, while ensuring that the other outriggers continue to extend rapidly. The rodless chamber pressure of the other outriggers is continuously monitored. The above process is repeated until all outriggers have touched the ground.

[0037] S43: The condition for all wheels to lift off the ground after all outriggers have touched the ground is that the length of the shortest outrigger is greater than the critical value for wheel lift-off.

[0038] When chassis 10 tilts to the left, the wheel lift-off threshold value Equation (7) needs to be satisfied:

[0039] (7)

[0040] When chassis 10 tilts to the right, the wheel's ground clearance threshold is reached. Equation (8) needs to be satisfied:

[0041] (8)

[0042] Where R is the wheel diameter, and L is the distance between the wheel and the center of the outrigger in the chassis plane. The angle between the chassis plane and the horizontal plane is θ. .

[0043] The coarse adjustment includes the following process:

[0044] S44: Actual tilt angle of the X-axis output by tilt sensor 8 Actual tilt angle of the Y-axis The sign of the value determines the position of the highest support leg. The Z-axis coordinate of the support point of the highest support leg in the horizontal coordinate system is: Coordinates in the chassis coordinate system At this point, the other outriggers still require displacement in the horizontal coordinate system. As shown in equation (9):

[0045] (9);

[0046] S45: Based on the process in S41, control the displacement of each outrigger to approach the set value of the outrigger displacement. ,Right now .

[0047] The fine-tuning includes the following processes:

[0048] S46: First adjust the displacement of each support leg to achieve the actual tilt angle of the X-axis. Approaching 0, and then adjusting the displacement of each outrigger to adjust the actual tilt angle of the Y-axis. If the actual tilt angle of the X-axis approaches 0, then... If the stopping condition is not met, repeat the adjustment until the actual tilt angle of the X-axis is reached. Actual tilt angle of the Y-axis All conditions for stopping were met.

[0049] The leveling strategy and algorithm divide the leveling process into three stages: outrigger contact with the ground, ground contact lifting, coarse leveling, and fine leveling. An adaptive PID algorithm based on velocity feedforward is designed to control the extension and retraction of the outriggers. Combined with dual-axis tilt sensors and displacement sensors, a closed-loop position control is achieved.

[0050] The control system is implemented and designed using an STM32F407 control chip based on the ARM architecture, which includes communication interfaces such as RS485, IO, UART, CAN, Ethernet, and ADC. It is equipped with a u / cos system with a control cycle of 10ms. The displacement feedback of the leveling outriggers uses a TBEPF magnetostrictive displacement sensor with a measurement range of 50~4500mm and an output of 4-20mA analog signal. The pressure feedback of the leveling outriggers uses a First pressure sensor with a measurement range of 0~100MPa and an output of 4-20mA analog signal. The control of the leveling outriggers is achieved by sending CAN commands with a baud rate set to 250kbps. The control of the solenoid valves is implemented using IO signals.

[0051] The beneficial effects of the method proposed in this invention patent are:

[0052] To address the issues of slow response and low accuracy in vehicle-mounted equipment leveling systems, a six-degree-of-freedom hydraulic leveling system was designed. This system controls the extension and retraction of hydraulic outriggers using a velocity-feedforward-based adaptive PID algorithm, and achieves closed-loop position control by combining real-time feedback from displacement and dual-axis tilt sensors. Employing a leveling strategy that prioritizes the X-axis before the Y-axis, this staged leveling combines coarse and fine adjustments, significantly improving leveling efficiency. Tests on a real high-load vehicle-mounted platform demonstrate that the system can achieve a dual-axis tilt angle of less than or equal to 0.05° within 150 seconds, effectively shortening the leveling time and achieving higher accuracy, thus meeting the requirements of practical engineering applications. Attached Figure Description

[0053] Figure 1 This is a diagram of the leveling system.

[0054] Figure 2 The logic control flowchart is for leveling.

[0055] Figure 3 The diagram shows the support leg structure and coordinate transformation relationship, where (a) represents the ideal leveling state and (b) represents the non-leveling state.

[0056] Figure 4 This is a graph showing the change in tilt angle over time during the leveling process.

[0057] Figure 5 This is a graph showing the results of the repeatability test.

[0058] Table 1 shows the determination of the highest outrigger and adjustment strategies based on the sign of the tilt angle.

[0059] Table 2. Fine-tuning level control strategy based on tilt angle error.

[0060] The components include: 1 leg, 2 legs, 3 legs, 4 legs, 5 legs, 6 legs, 7 hydraulic station and valve group, 8 tilt sensor, 9 leveling controller, and 10 chassis. Detailed Implementation

[0061] The present application is described in detail below with reference to the embodiments, but the present application is not limited to these embodiments.

[0062] Example 1

[0063] The six-degree-of-freedom hydraulic leveling system proposed in this invention patent adopts a leveling strategy that prioritizes the X-axis before the Y-axis, dividing the leveling process into three stages: ground contact lifting, coarse leveling, and fine leveling. The movement of the hydraulic outriggers is controlled by an adaptive PID control algorithm based on speed feedforward, combined with real-time feedback from outrigger displacement sensors and dual-axis tilt sensors to achieve closed-loop position control.

[0064] Specifically, the steps include the following:

[0065] A six-degree-of-freedom hydraulic leveling system for vehicle-mounted equipment includes outriggers 1, 2, 3, 4, 5, and 6, a hydraulic station and valve group 7, a tilt sensor 8, a leveling controller 9, and a chassis 10.

[0066] Among them, support legs 1, 2, 3, and 4 are the main support legs, and support legs 5 and 6 are the auxiliary support legs.

[0067] The outriggers 3 and 4 are installed at the two corners of the chassis 10 away from the front of the vehicle, the outriggers 5 and 6 are installed at the two corners of the chassis 10 close to the front of the vehicle, and the outriggers 1 and 2 are installed on the side of the chassis 10 along the direction the front of the vehicle is pointing. The center of the rectangle formed by the outriggers 1, 2, 3, and 4 is the center of gravity of the chassis 10.

[0068] The outriggers 1, 2, 3, 4, 5, and 6 are all hydraulic outriggers, and are connected to displacement sensors and pressure sensors.

[0069] The tilt sensor 8 is mounted at the center of gravity of the chassis 10 and is used to detect the tilt angle in the horizontal and vertical directions in real time; for example Figure 1 As shown.

[0070] The six outriggers adopt the following design: Figure 3 As shown in (a), under ideal leveling conditions, the vehicle chassis is parallel to the horizontal plane. Taking the fulcrum of outrigger 5 as the origin, the horizontal coordinate system OXYZ is coaxial with the chassis coordinate system OX'Y'Z'. Under non-ideal leveling conditions... Figure 3 (b) At this time, the chassis is not parallel to the horizontal plane and the six outriggers are at different heights.

[0071] S1: Determine the coordinates of each outrigger; Figure 3 For example, in the diagram, support leg 4 is the highest and support leg 5 is the lowest. Taking the fulcrum of the lowest support leg (support leg 5) as the origin, we establish a horizontal coordinate system OXYZ and a chassis coordinate system OX'Y'Z'. Then, in the chassis coordinate system and the horizontal coordinate system, the position coordinates of each support leg are respectively (x...). i ', y i ', 0) T and (x) i , y i , z i ) T According to the coordinate transformation relationship, after the chassis coordinate system is rotated α around the X-axis and β around the Y-axis, it coincides with the horizontal coordinate system. The corresponding transformation matrices are as shown in equations (1) and (2).

[0072] (1)

[0073] (2)

[0074] Therefore, the total transformation matrix R is as shown in equation (3), and the coordinates of each leg support point in the horizontal coordinate system after transformation are shown in equation (4).

[0075] (3)

[0076] (4)

[0077] A dual-axis tilt sensor is mounted at the center of gravity of the vehicle platform to detect the tilt angles in the horizontal and vertical directions in real time. Based on geometric relationships, the tilt angles in the two directions are approximately equal to the coordinate system rotation angles α and β, with the sign of the tilt angle determined by... Figure 3 (b) is positive. Generally speaking, the tilt angle is very small, so the coordinates of each leg support point in the horizontal coordinate system can be approximated by equation (5).

[0078] (5)

[0079] S2: Obtain the actual tilt angle of the X-axis by acquiring the tilt sensor 8. Actual tilt angle of the Y-axis Displacement data of each outrigger is obtained through displacement sensors, and pressure data of the rodless cavity of each outrigger is obtained through pressure sensors.

[0080] S3: The displacement data of each outrigger and the pressure data of the rodless chamber obtained in S2 are converted into digital signals by the analog-to-digital converter in the leveling controller 9, and the digital signals are preprocessed.

[0081] The specific method used is as follows:

[0082] S31: Use an arithmetic average filter and transmit the digital signal as the valid output value at that moment to the application layer.

[0083] S32: A two-step differential filter based on 2σ outlier removal is proposed. Outliers are removed within a fixed time window by twice the standard deviation, and the mean of that time window is taken. Then, a maximum allowable deviation Δ is set between sampling points in two adjacent fixed time windows. When acquiring a new sample value, two conditions must be simultaneously checked: whether the absolute value of the difference between the current sample value and the previous sample value, and the absolute value of the difference between the previous sample value and the sample value before that, are both greater than Δ. Only when both exceed Δ is it determined that the signal has undergone a real change; otherwise, the original signal value is maintained, and the mean of the remaining sampling points is finally output.

[0084] The mean value here is the average value of the displacement data of each outrigger and the pressure data of the rodless cavity within a fixed time window after removing data with large deviations.

[0085] S4: Based on the pre-processing results of S3, power is provided by the hydraulic station and valve group (7), and the leveling controller (9) controls each outrigger to start leveling. First, coarse adjustment is performed, and then fine adjustment is performed until the desired level is achieved. and When the stopping condition is met, the leveling ends, and the chassis (10) can be considered to have been leveled.

[0086] The specific method used is as follows:

[0087] S41: Leveling command initialization, determine whether leveling is allowed, load parameters, and update the leveling outrigger status.

[0088] When the solenoid ball valve is energized, the oil pressure is greater than 23 MPa and remains stable for 3 seconds.

[0089] Based on real-time feedback of outrigger displacement data, a PID algorithm is used to calculate the error between the current displacement and the planned displacement, and the valve opening is controlled accordingly. An adaptive PID algorithm based on feedforward velocity is proposed. During system control, the proportional-integral-derivative-velocity feedforward controller achieves precise regulation of the controlled object through a linear combination. Position closed-loop control is achieved based on the acquired displacement sensor feedback data to control the outrigger movement.

[0090] (6)

[0091] in This indicates the valve opening degree, which corresponds to the control speed. Outrigger displacement setting value Actual output of outrigger displacement The error, This represents the base velocity of the i-th outrigger, the value of which is obtained through calibration. These represent the proportional, integral, derivative, and velocity feedforward coefficients, respectively.

[0092] S42: When a sharp increase in the rodless chamber pressure of a certain outrigger is detected, it indicates that the outrigger has touched the ground. At this time, reduce the opening of the proportional valve of the outrigger that has touched the ground, while ensuring that the remaining outriggers continue to extend rapidly, and continuously monitor the pressure. Similarly, repeat the above operation procedure until all outriggers have touched the ground.

[0093] S43: The condition for all wheels to be off the ground after all outriggers have touched the ground is that the length of the shortest outrigger is greater than this critical value. and These indicate whether the chassis is tilted to the left or to the right.

[0094] (7)

[0095] (8)

[0096] Where R is the wheel diameter and L is the distance between the wheel and the center of the outrigger in the chassis plane. The angle between the chassis plane and the horizontal plane is θ. .

[0097] S44: Begin the coarse adjustment process of the leveling stage.

[0098] The highest outrigger is determined by combining the positive and negative values ​​of the dual-axis tilt sensor output. Based on the tilt angle sign convention and the outrigger position relationship, the criteria for determining the highest outrigger and the corresponding control strategy are shown in Table 1.

[0099] Table 1 shows the determination of the highest outrigger and adjustment strategies based on the sign of the tilt angle.

[0100]

[0101] in Let z be the z-coordinate of the highest support leg in the horizontal coordinate system. The coordinates of the highest outrigger in the chassis coordinate system.

[0102] (9)

[0103] S45: Based on S41 above, PID control is implemented by subtracting the setpoint displacement of each outrigger from the detected value of the corresponding displacement sensor, thereby implementing deviation control and ensuring that the displacement value of each outrigger approaches the setpoint within a certain error range. Given the high speed of the position error leveling method, it is highly suitable for coarse leveling.

[0104] S46: Begin the leveling and fine-tuning process. A fine-tuning strategy based on tilt angle error will be adopted. Considering the large aspect ratio of the large vehicle platform, instability in the width direction can easily lead to overturning; therefore, adjustment should be performed first. Figure 4 The X-axis direction in the middle makes Approach 0, then adjust the Y-axis to approach 0. If the tilt angle approaches 0 after the Y-axis adjustment is complete, and the X-axis tilt angle does not meet the stopping condition, the above operation is repeated. The precise leveling control strategy based on tilt angle error is shown in Table 2.

[0105] Table 2 Fine-tuning control strategy based on tilt angle error

[0106]

[0107] S10: When satisfied and When the conditions are met, the leveling process ends.

[0108] When the leveling system is running, the cylinder unlocking operation is completed when the system oil pressure exceeds 23MPa, and the leveling cylinder extension action is then initiated. Based on the adaptive PID algorithm based on speed feedforward, the opening degree of the control valve group is obtained through error calculation, and control commands are sent to the multi-way valve leveling cylinder to achieve speed control in three stages: ground contact lifting, coarse leveling, and fine leveling, ultimately ensuring that the tilt angle of both axes of the tilt sensor does not exceed 0.05°. Figure 4 The curve showing the change of tilt angle over time during the leveling process is presented.

[0109] The leveling process can be divided into four stages: ground contact and lifting, coarse leveling, fine leveling, and leveling completion. During the 0-45 second period, the X-axis tilt angle remains stable at -0.36°, while the Y-axis tilt angle remains stable at -0.16°. During this stage, the outriggers are in the ground contact and lifting process. During the 46-86 second period, coarse leveling begins, and both the X and Y axes rapidly approach 0°. During the 87-145 second period, fine leveling is performed with small fluctuations around 0° until… and The leveling process is completed in time. Furthermore, this leveling system was repeatedly tested five times, with the results as follows: Figure 5 As shown, in five tests, the tilt angles of the X and Y axes of a large vehicle platform were all less than 0.05°. The results indicate that the system demonstrates good reliability and repeatability in achieving high-precision tilt angle adjustment of the vehicle platform.

[0110] The above description is merely a specific embodiment of this application, but the scope of protection of this application is not limited thereto. Any modifications or substitutions made by those skilled in the art within the scope of the technology disclosed in this application should be covered within the scope of protection of this application. Therefore, the scope of protection of this application should be determined by the scope of the claims.

Claims

1. A six-degree-of-freedom hydraulic leveling system for vehicle-mounted equipment, characterized in that, comprising a support leg (1), a support leg (2), a support leg (3), a support leg (4), a support leg (5), a support leg (6), a hydraulic station and valve group (7), an inclination sensor (8), a leveling controller (9), a chassis (10); wherein the support leg (1), the support leg (2), the support leg (3), and the support leg (4) are main support legs, and the support leg (5) and the support leg (6) are auxiliary support legs; the support leg (3) and the support leg (4) are installed at the two corners of the chassis (10) away from the direction of the vehicle head, the support leg (5) and the support leg (6) are installed at the two corners of the chassis (10) close to the direction of the vehicle head, the support leg (1) and the support leg (2) are installed on the side of the chassis (10) along the direction of the vehicle head, and the center of the rectangle formed by the support leg (1), the support leg (2), the support leg (3), and the support leg (4) is the center of gravity of the chassis (10); the support leg (1), the support leg (2), the support leg (3), the support leg (4), the support leg (5), and the support leg (6) are all hydraulic support legs, connected with displacement sensors and pressure sensors; the inclination sensor (8) is installed at the center of gravity of the chassis (10) for real-time detection of the inclination in the horizontal and vertical directions; the six-degree-of-freedom hydraulic leveling system for vehicle-mounted equipment realizes leveling by controlling the movement of the support legs through the hydraulic station and valve group (7) based on a speed feed-based adaptive PID control algorithm, achieving closed-loop control of the position of the support legs.

2. The six-degree-of-freedom hydraulic leveling system for vehicle-mounted equipment according to claim 1, characterized in that, the speed feed-based adaptive PID control algorithm is as follows: S1: Determine the coordinates of each support leg; S2: obtaining the actual inclination of the X axis by acquiring the inclination sensor (8) , the actual inclination of the Y axis , obtaining the displacement data of each outrigger by the displacement sensor, and obtaining the rodless cavity pressure data of each outrigger by the pressure sensor; S3: Convert the analog signal obtained in S2 into a digital signal through an analog-to-digital converter in the leveling controller (9), and preprocess the digital signal; S4: According to the pre-processing result of S3, the power is provided by the hydraulic station and the valve group (7), and the leveling of each leg is started to be controlled by the leveling controller (9), first coarse adjustment, and then fine adjustment, until the stop condition of is met, the leveling is ended, at this time it can be considered that the chassis (10) has been leveled.

3. The six-degree-of-freedom hydraulic leveling system for vehicle-mounted equipment according to claim 2, characterized in that, in S1: A horizontal coordinate system OXYZ and a chassis coordinate system OX'Y'Z' are established with the lowest support point of the support leg as the origin, the position coordinates of the support points of each support leg in the horizontal coordinate system OXYZ are (x i ,y i ,z i ) T , and the position coordinates of the support points of each support leg in the chassis coordinate system OX'Y'Z' are (x i ',y i ',0) T , wherein i is 1, 2, 3, 4, 5 or 6. the leveling process is to rotate the chassis coordinate system OX'Y'Z' around the X-axis by α and around the Y-axis by β to coincide with the horizontal coordinate system OXYZ, and the corresponding transformation matrix of the X-axis and the transformation matrix of the Y-axis are as shown in formula (1) and formula (2): （1） （2） the total transformation matrix is as shown in formula (3): （3） the position coordinates of the fulcrums of the support legs after transformation are as shown in formula (4): （4）。 4. The six-degree-of-freedom hydraulic leveling system for vehicle-mounted equipment according to claim 3, characterized in that, in S3, the preprocessing includes the following process: S31: Use an arithmetic average filter, and transmit the digital signal as the effective output value at this moment to the application layer; S32: A two-pulse difference filter based on 2σ outlier rejection is proposed, which takes the mean value of the fixed time window after rejecting outliers by twice the standard deviation within the fixed time window, and then sets the maximum deviation allowed for the sampling points of the adjacent two fixed time windows When a new sampling value is obtained, two conditions need to be judged simultaneously: whether the absolute value of the difference between the current sampling value and the previous sampling value, and the absolute value of the difference between the previous sampling value and the sampling value before the previous sampling value, are both greater than ; only when both are greater than , is the signal determined to have a real change; otherwise, the original signal value is maintained and the mean value of the remaining sampling points is finally output the mean value here is the mean value of each support leg's displacement data and rodless cavity pressure data after removing the data with large deviations in the fixed time window.

5. The six-degree-of-freedom hydraulic leveling system for vehicle-mounted equipment according to claim 4, characterized in that, S4 includes the following process: S41: According to the displacement data of each leg obtained in S32, the error between the current displacement and the planned displacement is calculated by a PID algorithm, and the opening of the valve group is controlled, the PID algorithm is as formula (6): （6） wherein denotes the opening of the valve group, i.e. the control speed, set value for the outrigger displacement actual output of the outrigger displacement error, i.e. , denotes the base speed of the i-th outrigger, which is obtained by calibration; denote the proportional, integral, derivative and speed feedforward coefficients, respectively; S42: When the rodless cavity pressure data of a certain leg is detected to rise sharply, it indicates that the leg has touched the ground, at this time the opening of the valve group of the leg needs to be adjusted small, while ensuring the remaining legs continue to extend quickly, the rodless cavity pressure of the remaining legs is continuously monitored, the above process is repeated until all legs have touched the ground; S43: After all the legs touch the ground, the condition that all the wheels are off the ground is that the length of the lowest leg is greater than the wheel off-ground critical value; When the chassis (10) is tilted to the left, the wheel lift-off threshold The following equation (7) needs to be satisfied: （7） When the chassis (10) is tilted to the right side, the wheel-off-the-ground threshold value The following equation (8) needs to be satisfied: （8） wherein R is the wheel diameter and L is the distance between the wheel and the center of the leg in the plane of the chassis; the angle between the plane of the chassis and the horizontal is θ, .

6. The six-degree-of-freedom hydraulic leveling system for vehicle-mounted equipment according to claim 5, characterized in that, the coarse adjustment comprises the following processes: S44: The actual tilt angle of the X-axis output by the tilt sensor (8) Actual tilt angle of the Y-axis The sign of the value determines the position of the highest support leg. The Z-axis coordinate of the support point of the highest support leg in the horizontal coordinate system is: Coordinates in the chassis coordinate system At this point, the other outriggers still require displacement in the horizontal coordinate system. As shown in equation (9): （9） S45: based on the process of S41, control the displacement of each leg to approach the leg displacement set value i.e. .

7. The six-degree-of-freedom hydraulic leveling system for vehicle-mounted equipment according to claim 6, characterized in that, the fine adjustment comprises the following processes: S46: Adjusting the displacement of each leg to make the actual inclination of the X-axis tend to 0, and then adjusting the displacement of each leg to make the actual inclination of the Y-axis tend to 0, at which time if the actual inclination of the X-axis does not satisfy the stop condition, the adjustment is repeated until the actual inclination of the X-axis and the actual inclination of the Y-axis both satisfy the stop condition.

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