Landing leg leveling electro-hydraulic control system and method

Abstract

The invention discloses a landing leg leveling electro-hydraulic control system which comprises a hydraulic main loop which comprises a hydraulic pump, an oil return filter, an oil tank and a pipeline and is used for forming an oil supply path and an oil return path; the hydraulic loops are connected into the hydraulic main loop, each hydraulic loop comprises an electromagnetic reversing valve, a hydraulic cylinder, a first pressure sensor, an electric control balance valve and a one-way sequence valve, the hydraulic cylinders are installed on the supporting platform, a double-shaft tilt angle sensor is arranged on the supporting platform, and the first pressure sensors are connected with rodless cavities of the hydraulic cylinders; the control unit comprises a controller and an operation touch screen, the double-shaft tilt angle sensor and the first pressure sensor are connected into the controller, and the controller is used for controlling the electric control balance valve and the electromagnetic reversing valve. The hydraulic leveling device has a manual operation mode, an automatic operation mode, a rapid leveling operation mode and a high-rigidity leveling operation mode, and manual or automatic fine adjustment is allowed for supporting legs which are not in complete contact with the ground or are insufficient in load by monitoring pressure values of rodless cavities of all hydraulic cylinders, so that the supporting legs are kept horizontal.

Description

Technical Field

[0001] The present invention relates to the field of hydraulic control, and in particular to an outrigger leveling electro-hydraulic control system and method. Background Art

[0002] Common outrigger leveling hydraulic systems utilize a throttling and speed-regulating system consisting of a fixed-displacement pump and an on-off directional control valve. A hydraulically controlled check valve is installed in the rodless chamber of the vertical cylinder, locking the cylinder in place when the directional control valve is in the neutral position. Outrigger leveling is achieved by controlling the duration of a three-position, four-way solenoid valve to extend and retract the cylinder.

[0003] Chinese patent publication number CN111539083B discloses a modeling method for an autonomous leveling system for an aerial work platform chassis. Based on a four-point supported hydraulic leveling system, the system uses an angle error leveling method to level the chassis. An electromagnetic proportional directional valve regulates the flow rate in the system's main oil supply circuit to control the speed at which the outriggers extend and retract. Switch valves are then used to adjust the time it takes for each outrigger to extend and retract, controlling the accuracy of the chassis' X- and Y-axis tilt angles to complete the leveling process.

[0004] The advantages of the commonly used quantitative pump switch valve throttling speed control outrigger system are that the system is simple, reliable and easy to operate. However, the disadvantage is that it is difficult to level the outriggers on uneven ground. Insufficient pressure maintenance in the rodless chamber of the cylinder will cause the "soft leg" problem (excessive pressure and retraction of a certain cylinder will cause accidents such as overload and rollover), which requires a high level of user operation. Only one three-position four-way proportional speed control valve + one balancing valve is used to control the extension and retraction of the four vertical hydraulic cylinders. The system is simple in composition and low in cost. However, there are several disadvantages:

[0005] 1) In the initial state, the cylinder rod is off the ground and the four cylinders are extended at the same time. Since the protection valve is energized, the return oil path of the cylinder rod chamber is connected and the oil returns. In the load working state, the return oil path has no overflow or throttling protection, which is prone to stall or jitter. In addition, all four cylinders are equipped with zero-leakage electromagnetic switching valves, but no safety relief valve (or thermal expansion relief) to protect the cylinder rod chamber pressure from overload, which poses a safety hazard to the hydraulic system.

[0006] 2) Using the on-off timing of a switching valve to adjust the cylinder's extension and retraction length, and thus the chassis' X and Y axis inclination, this method calculates: metering pump flow / cylinder rodless chamber area * valve opening duration = cylinder extension length. Ignoring valve and cylinder leakage, this method provides accurate control. However, cylinder retraction can yield significant errors due to factors such as load, pressure in the rodless and rodless chambers, the reverse flow capacity of the balancing valve, and the opening of the proportional reversing valve. This repetitive adjustment of extension and retraction inevitably reduces leveling efficiency. Summary of the Invention

[0007] The purpose of the present invention is to provide a method for solving the above-mentioned problems, so as to solve the problems of low leveling efficiency and low stability of the existing legs.

[0008] To achieve the above objectives, the present invention provides the following technical solutions: an outrigger leveling electro-hydraulic control system, comprising:

[0009] The main hydraulic circuit includes a hydraulic pump, an oil return filter, an oil tank, and pipelines, which are used to form the oil supply and return routes;

[0010] At least four hydraulic circuits are connected to the hydraulic main circuit. The hydraulic circuit includes an electromagnetic reversing valve, a hydraulic cylinder, a first pressure sensor, an electronically controlled balancing valve, and a one-way sequence valve. The hydraulic cylinder is installed on a support platform. A dual-axis inclination sensor is provided on the support platform. The first pressure sensor is connected to the rodless chamber of the hydraulic cylinder.

[0011] The control unit includes a controller and an operating touch screen. The dual-axis tilt sensor and the first pressure sensor are connected to the controller. The controller is used to control the electronically controlled balancing valve and the electromagnetic reversing valve.

[0012] Preferably, the one-way sequence valve is connected to the rod chamber of the hydraulic cylinder.

[0013] Preferably, the electrically controlled balancing valve is connected to the rodless chamber of the hydraulic cylinder.

[0014] Preferably, the hydraulic pump is a load-sensitive variable displacement pump or a fixed displacement pump.

[0015] Preferably, a three-way flow valve and an electric proportional relief valve are provided on the hydraulic main circuit, the electric proportional relief valve is connected to the LS circuit, a second pressure sensor is provided on the LS circuit, and the second pressure sensor is connected to the controller.

[0016] Preferably, a pre-valve pressure compensator is provided between the oil outlet of the hydraulic main circuit and the electromagnetic reversing valve, and the spring chamber of the pre-valve pressure compensator is connected to the LS circuit.

[0017] The present invention discloses an electro-hydraulic control method for leg leveling, comprising the following steps:

[0018] S1. Establishing a hydraulic leveling system for the outriggers of the support platform; the outrigger hydraulic leveling system includes a main hydraulic circuit and four hydraulic circuits, each of which is connected to the main hydraulic circuit. Each hydraulic circuit includes a solenoid reversing valve, a hydraulic cylinder, a pressure sensor, an electronically controlled balancing valve, and a one-way sequence valve. The support platform is provided with a dual-axis inclination sensor, and the main hydraulic circuit is provided with an electric proportional relief valve.

[0019] In the initial state, the one-way sequence valve connected to the rod chamber of the hydraulic cylinder maintains pressure. The hydraulic cylinder is in the fully retracted state, and the hydraulic main circuit maintains a standby state with a set pressure differential ΔP. This refers to the pressure differential ΔP of the load-sensing pump; for a fixed-displacement pump system, it is the pressure differential ΔP of the three-way flow valve.

[0020] S3. Issue an outrigger extension command, the electric proportional relief valve sets the system working pressure to P1, the solenoid reversing valve switches to the right position, the rodless chamber pressure of the hydraulic cylinder increases, and the extended end of the hydraulic cylinder touches the ground;

[0021] S4. Adjust the system based on the dual-axis inclination sensor detection value and the four-cylinder pressure value on the control interface. If the ground is level, the four-cylinder fully extended system pressure reaches P1+ΔP, and the absolute values ​​of the X-axis and Y-axis inclination angles are both ≤0.3°, the system automatically levels without adjustment.

[0022] If the ground is uneven and the pressure in some rodless chambers reaches the P1 value, the electromagnetic reversing valve will be closed, and the extension or retraction of the remaining three cylinders will be manually adjusted based on the two inclination angles αx and αY.

[0023] S5. If stiffness adjustment is used to level the outriggers, it is necessary to ensure that the rodless chamber pressure reaches the P2 value at different extension amounts of the hydraulic cylinder. First, set the system working pressure of the electric proportional relief valve to the P2 value, select the hydraulic cylinder that has been fully extended among the four cylinders, and operate the hydraulic cylinder to extend again, so that its rodless chamber pressure increases from P1 to P2 value and then stops; then select the hydraulic cylinder diagonally opposite to it, operate it to fully extend, so that the rodless chamber pressure of the hydraulic cylinder reaches the P2 value and then stops. At this time, the X-axis and Y-axis angles are uneven, and then adjust the electronically controlled balancing valve to return the oil in the rodless chamber of the hydraulic cylinder. When the X-axis and Y-axis angles are close to 0, it stops, and the rodless chamber pressure is greater than the P1 value; use the same operation method to select the remaining two cylinders, first fully extend the cylinder to build up pressure to the P2 value, and then fine-tune the retract cylinder to a horizontal state, so that the rodless chamber pressures of the four cylinders all reach or are close to the P2 pressure value.

[0024] S6, outrigger retraction action. When the outrigger needs to be retracted, the system detects the outrigger retraction command. First, the electric proportional relief valve is set to the rated pressure P3. At the same time, the electric control balance valve and the electromagnetic reversing valve are energized and given the maximum control current. The system supplies oil to the rod chamber of the hydraulic cylinder, and at the same time, the oil returns to the rodless chamber of the hydraulic cylinder to realize the retraction action of the hydraulic cylinder.

[0025] Compared with the prior art, the present invention has the following beneficial effects:

[0026] High-precision leveling capability: A dual-axis inclination sensor monitors the platform's horizontal status (X-axis and Y-axis inclination) in real time and precisely controls the movements of four hydraulic cylinders, enabling the support platform to be adjusted to a very high level (absolute inclination ≤ 0.3°). This meets the stringent leveling requirements for precision work or stable equipment operation.

[0027] Adaptable to Complex Terrain: The system effectively handles uneven surfaces. By monitoring the pressure in each hydraulic cylinder's rodless chamber, it can determine which outriggers have touched the ground and are bearing the primary load. For outriggers that are not fully touching the ground or are underloaded, the system allows for manual or automatic (based on more complex logic) fine-tuning to ensure the final platform is level.

[0028] Safe and Reliable Pressure Maintenance and Support: During initial operation and after leveling, a one-way sequence valve connected to the hydraulic cylinder's rod chamber maintains pressure, preventing the outriggers from unexpectedly retracting under load and ensuring platform stability. The electronically controlled counterbalance valve further enhances system safety, particularly during outrigger retraction. It effectively controls oil return speed, preventing rapid drop and ensuring safe operation.

[0029] Flexible stiffness adjustment: The stiffness adjustment function allows the operator to adjust the overall stiffness of the support platform as needed. By controlling the rodless chamber pressure of the hydraulic cylinder at different extensions (to achieve the P2 value), the flexibility of the support system can be changed to adapt to different workloads or environmental vibrations, improving the stability and anti-interference ability of the platform.

[0030] Optimized hydraulic control and energy saving: The use of a load-sensing variable pump allows for precise adjustment of output flow and pressure based on actual system requirements, reducing energy loss and achieving energy-efficient operation. The electro-proportional relief valve allows for precise control of the system's operating pressures (P1, P2, and P3), eliminating the energy waste associated with fixed pressures associated with traditional relief valves. Pressure can be adjusted based on various operating conditions (leveling, operation, and retraction), optimizing hydraulic system performance. The use of an LS circuit (load-sensing circuit) enables components such as the three-way flow valve to distribute flow based on changes in load pressure, improving the hydraulic system's responsiveness and control accuracy.

[0031] In summary, the outrigger hydraulic leveling system integrates high-precision sensing, intelligent control, safety protection and optional stiffness adjustment functions, and can provide a stable, reliable and efficient support solution for various types of mobile equipment or occasions requiring precise horizontal support. BRIEF DESCRIPTION OF THE DRAWINGS

[0032] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the following briefly introduces the drawings required for use in the embodiments or the description of the prior art. Obviously, the drawings described below are only some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying any creative work.

[0033] Figure 1 It is a schematic diagram of the overall structure of the present invention.

[0034] The accompanying drawings are explained as follows: 1. Return oil filter; 2. Hydraulic pump; 3. Control valve group; 4. One-way sequence valve; 5. Hydraulic cylinder; 6. Pressure sensor; 7. Electronically controlled balancing valve; 8. Controller; 9. Dual-axis inclination sensor; 10. Touch screen; 11. Solenoid reversing valve; 12. Three-way flow valve; 13. Electric proportional overflow valve; 14. Second pressure sensor; 15. Pre-valve pressure compensator. DETAILED DESCRIPTION

[0035] To make the objectives, technical solutions, and advantages of the present invention more clear, the technical solutions of the present invention will be described in detail below. Obviously, the embodiments described are only some embodiments of the present invention, not all embodiments. Based on the embodiments of the present invention, all other implementations obtained by ordinary technicians in this field without making any creative work are within the scope of protection of the present invention.

[0036] like Figure 1 As shown, this embodiment discloses an outrigger leveling electro-hydraulic control system, including a power unit, a control unit, a detection unit and an execution unit;

[0037] The power unit includes a hydraulic pump 2 and a return oil filter 1. The hydraulic pump 2 provides an oil source for the system, and the return oil filter 1 is used to filter the oil returning to the oil tank. The power unit is a hydraulic main circuit.

[0038] The control unit includes electrical and hydraulic components. The electrical components include a touch screen 10 and a PLC controller 8. The HMI touch screen 10 is the input port for user manipulation. The controller 8 receives instructions and controls the output signals to the relevant solenoid valves. The hydraulic components include a control valve group 3 and an electrically controlled balancing valve 7. The control valve group 3 includes a solenoid reversing valve and an electrically proportional reversing control valve group with a pre-valve pressure compensator. Its LS oil circuit is equipped with an electrically proportional relief valve and a pressure sensor to control the reversing flow rate of the oil cylinder and the relief pressure at the LS port. The electrically controlled balancing valve 7 is installed in the rodless chamber of the hydraulic cylinder 5 and can accurately adjust the retraction flow rate.

[0039] The detection unit includes a second pressure sensor 14 installed at the M port of the control valve group 3, a first pressure sensor 6 installed at the rodless cavity of each hydraulic cylinder 5, and a dual-axis tilt sensor 9 installed on the frame or chassis, which are used to respectively detect the system load pressure, the cylinder load pressure, and the angle changes of the X and Y axes in real time;

[0040] The actuator unit includes four hydraulic cylinders 5, each with a one-way sequence valve 4 connected to the rod chamber. This ensures that the outriggers retract without falling out of the cylinder and that the empty cylinders extend smoothly. The four hydraulic cylinders 5 and the electromagnetic reversing valve 11 form the support hydraulic circuit.

[0041] The hydraulic pump 2 is a load-sensing variable displacement pump or a fixed displacement pump. When it is a fixed displacement pump, the flow capacity of the three-way flow valve on the matching control valve group 3 is different from that of the load-sensing variable displacement pump.

[0042] This embodiment discloses a control method for an outrigger leveling electro-hydraulic control system, including manual and automatic operation modes. Both modes employ rapid leveling and high-rigidity adjustment control strategies. The criterion for determining whether leveling is complete is that the absolute values ​​of the X-axis and Y-axis inclination values ​​displayed by the dual-axis inclination sensor are both ≤ 0.3° (which can be set to 0.1° based on operational requirements). The working principle of the electro-hydraulic control system is described using manual outrigger extension and leveling as an example.

[0043] The working process of manual control mode is as follows:

[0044] Initial state: All solenoid valves in the system are de-energized. Hydraulic cylinder 5 is fully retracted under the pressure-maintaining action of one-way sequence valve 4. If hydraulic pump 2 is a load-sensing pump, since control valves 3 are all de-energized, port LS after the reversing valve is connected to port T for oil return. The load-sensing pump operates at a set pressure differential ΔP, maintaining a low flow rate on standby. If it is a fixed-displacement pump, the output hydraulic oil is unloaded through the three-way flow valve on control valve group 3.

[0045] Manually operate the four legs to extend and touch the ground at the same time: After the system detects the extension command, it first controls the LS oil circuit electric proportional relief valve (-Y0) on the control valve group 3 to provide a constant current, sets the system's maximum working pressure to the preset value P1, and then simultaneously controls -Y1 b, -Y2b, -Y3b and -Y4b to obtain the maximum current. The proportional valve switches to the right position, and the hydraulic oil enters the rodless chamber of the hydraulic cylinder 5 through the control valve group 3 and the one-way valve in the electronically controlled balancing valve 7. The hydraulic oil in the rod chamber flows back to the tank through the one-way sequence valve 4 and the control valve group 3. When some cylinders touch the ground, the pressure in their rodless chambers increases, the extension speed decreases, and the oil flows to the remaining cylinders to make them touch the ground quickly.

[0046] Continue to extend the outriggers and manually level them: observe the detection values ​​of the dual-axis inclination sensors and the pressure values ​​of the four cylinders. If the ground is uneven, close the reversing valve corresponding to the cylinder whose rodless chamber pressure reaches the P1 value. Combined with the X-axis and Y-axis inclination values, manually adjust the extension or retraction of the remaining cylinders.

[0047] Outrigger stiffness adjustment: Based on manual leveling, increase the current value of the LS oil circuit electric proportional relief valve (-Y0) to make the relief pressure of the LS oil circuit reach P2 (P2=1.33*P1). Operate each cylinder in turn, first operating the cylinder to extend individually to increase the pressure in the rodless chamber to P2 and then stop. Then fine-tune the electronically controlled balancing valve 7 to slowly retract the cylinder until the X-axis and Y-axis angles are close to 0, so that the pressure in the rodless chambers of the four cylinders reaches or is close to P2.

[0048] The present invention offers two operating modes: rapid and high-rigidity leveling. In the former, the electric proportional relief valve sets the system operating pressure to P1, regardless of extension or retraction, resulting in a rodless chamber pressure around P1. The latter differs: during extension, the electric proportional relief valve sets the system operating pressure to P2, and during retraction, to P3. Fine-tuning of the electronically controlled balancing valve opening ensures the rodless chamber pressure remains around P2.

[0049] Outrigger retraction: After the system detects a retraction command, it sets the LS circuit's proportional relief valve to the rated pressure P3. Simultaneously, the proportional valve on the electronically controlled counterbalance valve 7 and -Y1a, -Y2a, -Y3a, and -Y4a on control valve group 3 all receive maximum control current. The system then supplies oil to the cylinder's rod chamber, while oil returns to the rodless chamber through the counterbalance valve, causing the cylinder to retract. P3 is the pump's rated pressure (for example, the Rexroth A10VO load-sensing variable displacement piston pump has a rated pressure of 25 MPa and a maximum pressure of 28 MPa). This means the pump can operate at 25 MPa for extended periods or 28 MPa for short periods. In this system, P3 > P2 > P1. Setting P3 only operates during vertical outrigger cylinder retraction. Because the cylinder's area ratio, i, is typically between 2 and 4, a high pressure at P3 raises the cylinder's rodless chamber pressure by at least 0.25 to 0.5 times P3. Higher rodless chamber pressure increases outrigger stiffness. The retraction speed can be controlled by adjusting the opening of the electronically controlled balancing valve. In addition, each rodless chamber of the oil cylinder has a pressure sensor, and overpressure will alarm or limit the retraction action.

[0050] The working principle of the automatic control mode is the same as that of the manual control mode. The difference is that in the automatic mode, the controller 8 automatically controls the action of the relevant electromagnetic valve according to the detection data of the detection unit to complete the leveling process.

[0051] The calculation formula of the preset value P1 is P1=(G+2*π*(D 2 -d 2 )) / (4*π*D 2 / 4), where G is the product weight, D is the cylinder diameter, and d is the cylinder rod diameter. The P1 value can be determined by operating one cylinder to hold pressure in the fully retracted position and observing the pressure sensor reading at port M on control valve block 3. The pressure of one-way sequence valve 4 is set to 15-25 bar. The opening pressure of the LS circuit electric proportional relief valve on control valve block 3 is ≤5 bar when de-energized. Increasing the control current increases the relief pressure.

[0052] The outrigger leveling electro-hydraulic control system of the present invention is applied to engineering machinery products and other special vehicles. The engineering machinery products include wheel cranes, truck cranes, fire trucks, aerial work vehicles, and concrete pump trucks.

[0053] The electro-hydraulic control system of the present invention includes a hydraulic pump, an electric proportional reversing control valve group with a pre-valve pressure compensator, an electric proportional relief valve and a pressure sensor installed in the LS oil circuit of the valve, and the pre-valve pressure compensator ensures that the pressure difference before and after the reversing valve is constant; four vertical hydraulic cylinders, each vertical hydraulic cylinder rodless chamber is installed with an electric control balance valve and a pressure sensor, which can accurately adjust the retraction flow; the rod chamber of the vertical hydraulic cylinder is connected to a one-way sequence valve, which can ensure that the outrigger is retracted into place without "falling out of the cylinder" and that the empty cylinder is extended smoothly; the touch screen can be used for close-range control of the outrigger leveling. The present invention has two operating modes: manual and automatic, and two control strategies: fast leveling and high-rigidity adjustment, which improve the efficiency of outrigger leveling and avoid the problem of soft legs.

[0054] Within the technical scope disclosed by the present invention, any changes or substitutions that can be easily imagined should be included in the protection scope of the present invention. Therefore, the protection scope of the present invention should be based on the protection scope of the claims.

Claims

1. An electro-hydraulic control system for outrigger leveling, characterized in that: include: A hydraulic main circuit, comprising a hydraulic pump (2), an oil return filter (1), an oil tank and pipelines, for forming an oil supply and oil return route; At least four hydraulic circuits are connected to the hydraulic main circuit, the hydraulic circuit comprising an electromagnetic reversing valve (11), a hydraulic cylinder (5), a first pressure sensor (6), an electrically controlled balancing valve (7) and a one-way sequence valve (4), the hydraulic cylinder (5) being mounted on a supporting platform, a dual-axis inclination sensor (9) being provided on the supporting platform, and the first pressure sensor (6) being connected to a rodless chamber of the hydraulic cylinder (5); The control unit comprises a controller (8) and an operating touch screen (10); the dual-axis tilt sensor (9) and the first pressure sensor (6) are connected to the controller (8); and the controller (8) is used to control the electrically controlled balancing valve (7) and the electromagnetic reversing valve (11).

2. The outrigger leveling electro-hydraulic control system according to claim 1, characterized in that: The one-way sequence valve (4) is connected to the hydraulic cylinder (5) via a rod cavity.

3. The outrigger leveling electro-hydraulic control system according to claim 2, characterized in that: The electrically controlled balancing valve (7) is connected to the rodless chamber of the hydraulic cylinder (5).

4. The outrigger leveling electro-hydraulic control system according to claim 3, characterized in that: The hydraulic pump (2) is a load-sensitive variable displacement pump or a fixed displacement pump.

5. The outrigger leveling electro-hydraulic control system according to claim 4, characterized in that: The hydraulic main circuit is provided with a three-way flow valve (12) and an electric proportional overflow valve (13), the electric proportional overflow valve (13) is connected to the LS circuit, the LS circuit is provided with a second pressure sensor (14), and the second pressure sensor (14) is connected to the controller (8).

6. The outrigger leveling electro-hydraulic control system according to claim 4, characterized in that: A pre-valve pressure compensator (15) is provided between the oil outlet of the hydraulic main circuit and the electromagnetic reversing valve (11), and a spring chamber of the pre-valve pressure compensator (15) is connected to the LS circuit.

7. A method for controlling outrigger leveling by electro-hydraulic means, characterized in that , including the following steps: S1. Establish a hydraulic leveling system for the outriggers of the support platform. The outrigger hydraulic leveling system includes a main hydraulic circuit and four hydraulic circuits. The hydraulic circuits are connected to the main hydraulic circuit. Each hydraulic circuit includes a solenoid reversing valve, a hydraulic cylinder, a pressure sensor, an electronically controlled balancing valve, and a one-way sequence valve. The support platform is provided with a dual-axis inclination sensor. The main hydraulic circuit is provided with a three-way flow valve and an electric proportional relief valve. S2, initial state, the one-way sequence valve connected to the rod chamber of the hydraulic cylinder plays a pressure-maintaining role, the hydraulic cylinder is in a fully retracted state, and the hydraulic main circuit maintains a standby state with a set pressure difference ΔP; S3. Issue an outrigger extension command, the electric proportional relief valve sets the system working pressure to P1, the solenoid reversing valve switches to the right position, the rodless chamber pressure of the hydraulic cylinder increases, and the extended end of the hydraulic cylinder touches the ground; S4. Adjust the system based on the dual-axis inclination sensor detection value and the four-cylinder pressure value on the control interface. If the ground is level, the four-cylinder fully extended system pressure reaches P1+ΔP, and the absolute values ​​of the X-axis and Y-axis inclination angles are both ≤0.3°, the system automatically levels without adjustment. If the ground is uneven and the pressure in some rodless chambers reaches the P1 value, the electromagnetic reversing valve will be closed, and the extension or retraction of the remaining three cylinders will be manually adjusted based on the two inclination angles αx and αY. S6, outrigger retraction action. When the outrigger needs to be retracted, the system detects the outrigger retraction command. First, the electric proportional relief valve is set to the rated pressure P3. At the same time, the electric control balance valve and the electromagnetic reversing valve are energized and given the maximum control current. The system supplies oil to the rod chamber of the hydraulic cylinder, and at the same time, the oil returns to the rodless chamber of the hydraulic cylinder to realize the retraction action of the hydraulic cylinder.

8. The electro-hydraulic control method for leg leveling according to claim 7, characterized in that , also includes: S5. If stiffness adjustment is used to level the outriggers, it is necessary to ensure that the rodless chamber pressure reaches the P2 value at different extension amounts of the hydraulic cylinder. First, set the system working pressure of the electric proportional relief valve to the P2 value, select the hydraulic cylinder that has been fully extended among the four cylinders, and operate the hydraulic cylinder to extend again, so that its rodless chamber pressure increases from P1 to P2 value and then stops; then select the hydraulic cylinder diagonally opposite to it, operate it to fully extend, so that the rodless chamber pressure of the hydraulic cylinder reaches the P2 value and then stops. At this time, the X-axis and Y-axis angles are uneven, and then adjust the electronically controlled balancing valve to return the oil in the rodless chamber of the hydraulic cylinder. When the X-axis and Y-axis angles are close to 0, it stops, and the rodless chamber pressure is greater than the P1 value; use the same operation method to select the remaining two cylinders, first fully extend the cylinder to build up pressure to the P2 value, and then fine-tune the retract cylinder to a horizontal state, so that the rodless chamber pressures of the four cylinders all reach or are close to the P2 pressure value.

Images