An engineering machinery electro-hydraulic steering precision control device and method

Abstract

The application discloses an engineering machinery electro-hydraulic steering precise control device and method, an electro-hydraulic steering unit is communicated with a main pump unit and a hydraulic execution unit; a control unit is connected with an electric control handle unit, the main pump unit and the electro-hydraulic steering unit, the control of the electric control handle unit on the main pump unit and the electro-hydraulic steering unit is realized through the control unit, after the steering handle sends a signal, the valve core displacement calculation module and the flow matching module of the controller are passed, the real-time matching of the valve core displacement of the reversing valve and the output flow of the electric control pump is realized, the actual displacement fed back by the displacement sensor is compared with the set target displacement, the driving current of the displacement of the reversing valve is adjusted in real time, the high-precision matching of the electric control main pump and the valve core displacement and the electronic buffer of steering stop are realized.

Description

Technical Field

[0001] This invention relates to a precision control device and method for electro-hydraulic steering of engineering machinery, belonging to the field of steering technology for engineering machinery. Background Technology

[0002] To improve the driving comfort of earthmoving machinery, the steering control system of large-tonnage loaders is developing towards electrification. The electric control lever can not only improve the response speed and driving comfort, but also achieve closed-loop control that hydraulic control systems cannot achieve, thereby improving the control accuracy of the steering system.

[0003] Existing technologies achieve valve core displacement through high-speed switching valves and electro-proportional valves, but they have the following technical problems:

[0004] 1. Difficult to control during micro-steering operations: When the high-speed switching valve controls the valve core displacement, the main valve core displacement is achieved by opening the high-speed switching valve during the micro-opening process. During the micro-opening process, the flow rate into the valve core spring cavity is fast and large, and the pressure is built up quickly, resulting in a large overshoot of the main valve core displacement. During the adjustment process, the valve core is unstable, which manifests as steering vibration during micro-steering operations of the whole vehicle.

[0005] 2. The use of four high-speed switching valves increases the vehicle failure rate and costs.

[0006] 3. Steering systems using low-voltage proportional pilot control cannot achieve closed-loop steering control, resulting in poor steering control accuracy. Summary of the Invention

[0007] To address the shortcomings of existing technologies, the present invention aims to provide a precision control device and method for electro-hydraulic steering of engineering machinery, which solves the problems of poor micro-operation control performance, high cost, and high vehicle steering failure rate in existing technologies.

[0008] To achieve the above objectives, the present invention adopts the following technical solution:

[0009] A precision control device for electro-hydraulic steering of engineering machinery includes an electro-hydraulic steering unit, a main pump unit, a control unit, an electric control handle unit, a hydraulic auxiliary component unit, and a hydraulic actuator unit;

[0010] The electro-hydraulic steering unit includes a directional valve, a priority valve, a first electro-hydraulic proportional valve, and a second electro-hydraulic proportional valve; the hydraulic auxiliary unit includes hydraulic lines and a hydraulic oil tank.

[0011] The inlet of the main pump unit is connected to the hydraulic oil tank, the outlet P of the main pump unit is connected to the inlet of the priority valve, the CF port of the priority valve is connected to the A port of the directional valve, the B and C ports of the directional valve are respectively connected to the hydraulic actuator, the LS port of the directional valve is connected to the right control chamber of the priority valve, and the T port of the directional valve is connected to the hydraulic oil tank.

[0012] The inlet of the first electro-proportional valve and the inlet of the second electro-proportional valve are connected to the outlet of the pilot oil source block. The return ports of the first and second electro-proportional valves are connected to the hydraulic oil tank. The working port of the first electro-proportional valve is connected to the control port L of the directional valve. The working port of the second electro-proportional valve is connected to the control port R of the directional valve. The control ports of the first and second electro-proportional valves are connected to the control unit. The control unit is also connected to the electric control handle unit and the main pump unit.

[0013] When the control unit controls the first electro-proportional valve to be energized, the first electro-proportional valve operates in the lower position, and the oil inlet and working oil port of the first electro-proportional valve are connected. The directional valve operates in the left position, and the A port, LS port, and B port of the directional valve are connected. The C port and T port of the directional valve are also connected.

[0014] When the control unit energizes the second electro-proportional valve, the second electro-proportional valve operates in the lower position, with its inlet and working ports connected. The directional valve operates in the right position, with its A, LS, and C ports connected, and its B and T ports connected.

[0015] Furthermore, the aforementioned electro-hydraulic steering unit also includes a displacement sensor, with its two ends connected to the directional valve and the control unit, respectively. The displacement sensor is used to transmit the actual displacement of the directional valve core to the control unit.

[0016] Furthermore, the aforementioned electro-hydraulic steering unit also includes dynamic damping. The right control chamber and D port of the dynamic damping are both connected to the LS port of the directional valve, and the E port of the dynamic damping is connected to the hydraulic oil tank.

[0017] Furthermore, the aforementioned electro-hydraulic steering unit also includes a check valve and a damper. The oil inlet of the check valve is connected to the D port of the dynamic damper, the oil outlet of the check valve is connected to the LS port of the directional valve, one end of the damper is connected to the oil inlet of the check valve, and the other end is connected to the CF port of the priority valve.

[0018] Furthermore, the aforementioned electro-hydraulic steering unit also includes a hydraulically controlled directional valve, with the inlet and control ports of the hydraulically controlled directional valve connected to the T-port of the directional valve, and the outlet of the hydraulically controlled directional valve connected to the hydraulic oil tank.

[0019] Furthermore, the aforementioned control unit includes a controller.

[0020] Furthermore, the aforementioned electronically controlled handle unit includes an electronic handle.

[0021] Furthermore, the aforementioned hydraulic actuator includes a first hydraulic cylinder and a second hydraulic cylinder. The rodless chamber of the first hydraulic cylinder and the rod chamber of the second hydraulic cylinder are connected to port B of the directional valve, and the rod chamber of the first hydraulic cylinder and the rodless chamber of the second hydraulic cylinder are connected to port C of the directional valve.

[0022] Furthermore, the aforementioned main pump unit includes a pressure sensor, an electro-proportional control module, and an electric pump. The outlet of the electric pump is connected to port P, and the inlet of the electric pump is connected to the hydraulic oil tank. One end of the pressure sensor is connected to the outlet of the electric pump, and the other end is connected to the control unit. One end of the electro-proportional control module is connected to the control port of the electric pump, and the other end is connected to the control unit.

[0023] A method for precise electro-hydraulic steering control of engineering machinery includes the following steps:

[0024] Based on the percentage of the received electronic handle signal, calculate the corresponding pilot pressure that pushes the directional valve spool displacement, and calculate the target displacement of the directional valve spool based on the pilot pressure.

[0025] Based on the target displacement of the directional valve core, calculate the driving current of the first electro-proportional valve and the second electro-proportional valve, output the driving current to the first electro-proportional valve and the second electro-proportional valve, and control the movement of the directional valve core.

[0026] The actual displacement of the directional valve core transmitted by the displacement sensor is compared with the target displacement, and the drive current is adjusted in real time based on the PID algorithm.

[0027] Furthermore, the foregoing also includes the following steps:

[0028] Based on the target displacement of the directional valve core, the flow rate required by the electro-hydraulic steering unit at this time is calculated.

[0029] Based on the flow rate required by the electro-hydraulic steering unit, the output flow rate of the electro-hydraulic pump is calculated, and the drive current of the electro-proportional control module is calculated according to the output flow rate of the electro-hydraulic steering unit. The drive current is then output to the electro-proportional control module to control the flow rate output of the electro-hydraulic pump to match the flow rate requirement of the reversing valve in real time.

[0030] Furthermore, the foregoing includes the following steps:

[0031] When the electronic handle is moved to the left at a certain position or continuously changed within a certain range on the left, the output current controls the first electro-proportional valve to work in the lower position, the second electro-proportional valve to work in the upper position, and the directional valve to work in the left position.

[0032] Furthermore, the foregoing includes the following steps:

[0033] When the electronic handle is moved to the right to a certain position or continuously changed within a certain range on the right side, the output current controls the first electro-proportional valve to work in the upper position, the second electro-proportional valve to work in the lower position, and the directional valve to work in the right position.

[0034] Furthermore, the foregoing includes the following steps:

[0035] When the electronic handle is in the neutral position, the output current controls the first electro-proportional valve to operate in the upper position, the second electro-proportional valve to operate in the upper position, and the directional valve to operate in the neutral position.

[0036] The beneficial effects achieved by this invention are as follows:

[0037] 1. The valve core of the directional valve is switched by an electro-proportional valve. By utilizing the linear characteristics of the output pressure of the electro-proportional valve, smooth acceleration or deceleration is achieved during directional switching, reducing valve core opening and stopping impact, as well as reducing costs and failure rate.

[0038] 2. During the movement of the valve core, the actual displacement of the valve core is read by a displacement sensor to realize closed-loop control of the valve core displacement and improve the control accuracy of electro-hydraulic steering.

[0039] 3. The adoption of electro-hydraulic proportional control improves the driving comfort of the vehicle, enables closed-loop control of valve core displacement, and improves the control accuracy of the steering system of engineering machinery.

[0040] 4. An electronically controlled positive flow steering system is adopted, which adjusts the displacement of the electronically controlled pump in real time according to the flow demand of the steering valve, thereby reducing flow loss and energy consumption. Attached Figure Description

[0041] Figure 1 This is a schematic diagram of the hydraulic electrical system of this invention;

[0042] Figure 2 This is a flowchart of the valve core displacement module and flow matching module of the present invention.

[0043] Figure 3 This is a flowchart of the valve core displacement closed-loop control of the present invention.

[0044] The meanings of the reference numerals in the diagram are as follows: 1-Electro-hydraulic steering unit; 2-Main pump unit; 3-Controller; 4-Electronic handle; 5-Hydraulic oil tank; 6-Hydraulic actuator; 1.1-Directional control valve; 1.2-Priority valve; 1.3-Dynamic damping; 1.4-Displacement sensor; 1.5-First electro-proportional valve; 1.6-Second electro-proportional valve; 1.7-Check valve; 1.8-Hydraulic directional control valve; 1.9-Damping; 2.1-Pressure sensor; 2.2-Electro-proportional control module; 2.3-Electro-controlled pump; 6.1-First hydraulic cylinder; 6.2-Second hydraulic cylinder. Detailed Implementation

[0045] The technical solution of the present invention will be described in detail below with reference to the accompanying drawings and specific embodiments. It should be understood that the embodiments and specific features in the embodiments are detailed descriptions of the technical solution of the present application, rather than limitations thereof. In the absence of conflict, the embodiments and technical features in the embodiments can be combined with each other.

[0046] This embodiment discloses a precision control device for electro-hydraulic steering in engineering machinery, such as... Figure 1 As shown, it includes an electro-hydraulic steering unit 1, a main pump unit 2, a control unit, an electric control handle unit, a hydraulic auxiliary component unit, and a hydraulic actuator unit 6.

[0047] The electro-hydraulic steering unit 1 includes a directional valve 1.1, a priority valve 1.2, a dynamic damping valve 1.3, a displacement sensor 1.4, a first electro-hydraulic proportional valve 1.5, a second electro-hydraulic proportional valve 1.6, a check valve 1.7, and a hydraulically controlled directional valve 1.8; the main pump unit 2 includes a pressure sensor 2.1, an electro-proportional control module 2.2, and an electro-hydraulic pump 2.3; the control unit includes a controller 3; the electro-hydraulic handle unit includes an electronic handle 4; the hydraulic auxiliary components unit includes hydraulic pipelines and a hydraulic oil tank 5; and the hydraulic actuation unit 6 includes a first hydraulic cylinder 6.1 and a second hydraulic cylinder 6.2.

[0048] The electro-hydraulic steering unit 1 connects the main pump unit 2 and the hydraulic actuator unit 6. The control unit connects the electric control handle unit, the main pump unit 2 and the electro-hydraulic steering unit 1. The control unit enables the electric control handle unit to control the main pump unit 2 and the electro-hydraulic steering unit 1.

[0049] The pressurized oil from the outlet of the electronically controlled pump 2.3 enters the electro-hydraulic steering unit via port P. The position selection via priority valve 1.2 determines the flow rate into ports CF and EF. The control unit communicates with electro-hydraulic steering unit 1 via the CAN1 bus signal, with the electronically controlled handle unit via the CAN2 signal, and with the main pump unit 2 via the AI1 and PWM1 signals.

[0050] Displacement sensor 1.4 is installed at L side of directional valve 1.1. When directional valve 1.1 switches, displacement sensor 1.4 collects the actual displacement value of valve core and transmits it to controller 3 via CAN1 bus signal.

[0051] The oil inlet of the first electro-proportional valve 1.5 and the oil inlet of the second electro-proportional valve 1.6 are supplied with oil by the pilot oil source block. The control ports of the first electro-proportional valve 1.5 and the second electro-proportional valve 1.6 are connected to the controller 3 via the CAN1 bus. The electronic handle 4 is connected to the controller 3 via the CAN2 bus. The displacement sensor 1.4 transmits the actual displacement data to the controller 3 via the CAN1 bus. The pressure sensor 2.1 transmits the pressure value of the pump outlet to the controller 3 via the AI1 hard wire. The controller 3 controls the electro-proportional control module 2.2 of the electric pump through the PWM1 signal to realize the variable displacement control of the electric pump.

[0052] Furthermore, the main pump unit 2 is an electrically controlled pump. The pump's displacement is adjusted by regulating the current of the electrical control module 2.2. The outlet of the electrically controlled pump 2.3 is connected to the inlet of the priority valve 1.2. The CF port of the priority valve is connected to port A of the directional valve 1.1. Port B of the directional valve 1.1 is connected to the rodless chamber of the first hydraulic cylinder 6.1 and the rod chamber of the second hydraulic cylinder 6.2. Port C is connected to the rod chamber of the first hydraulic cylinder 6.1 and the rodless chamber of the second hydraulic cylinder 6.2. Simultaneously, when the pressurized oil in the electrically controlled pump 2.3 enters the CF port of the priority valve 1.2 through port P, the pressurized oil, after passing through damper 1.9, opens the check valve 1.7 and enters the LS pipeline. This connects the LS pipeline to the right control chamber of the priority valve 1.2 and the dynamic damper 1.3. The right-side control chamber is connected, and the E port of dynamic damping 1.3 is connected to the hydraulic oil tank 5. The T port of directional valve 1.1 is connected to the hydraulic oil tank 5 via a two-position two-way hydraulic directional valve 1.8. The inlet ports of the first electro-proportional valve 1.5 and the second electro-proportional valve 1.6 are connected to the pilot oil source block for stabilizing pressure. The working port of the first electro-proportional valve 1.5 is connected to the control port L of directional valve 1.1, and the working port of the second electro-proportional valve 1.6 is connected to the control port R of directional valve 1.1. The return ports of the first electro-proportional valve 1.5 and the second electro-proportional valve 1.6 are connected to the hydraulic oil tank 5. When the first electro-proportional valve 1.5 is energized and the second electro-proportional valve 1.6 is de-energized, the lower position of the first electro-proportional valve 1.5 is in the working position, and the pilot pressure after decompression... The oil enters the L control chamber of the directional control valve 1.1. The upper position of the second electro-proportional valve 1.6 is in the working position. The pressure in the R side control chamber of the directional control valve 1.1 is connected to the oil tank. The pressure oil in the L chamber pushes the valve core to move to the right, realizing the valve core switching. The left position of the three-position five-way directional control valve 1.1 is in the working position. The pressure oil enters the actuator through ports A and B. At the same time, port B is connected to port LS, transmitting the load pressure to the right control chamber and dynamic damping of the priority valve 1.2. The priority valve 1.2 adjusts the flow rate into the CF and EF oil passages according to the load pressure to realize steering priority. At the same time, the excess flow is shared to the EF side to realize the effective utilization of flow and reduce energy loss. Meanwhile, the return oil from the actuator enters the two-position two-way hydraulic directional control valve 1 through ports C and T. 8. When the return oil flow increases, the right position of the two-position two-way hydraulic directional valve 1.8 is in the working position, and the large flow of return oil flows back to the hydraulic oil tank, realizing the left turn of the vehicle. At this time, the actual displacement of the valve core is transmitted to the controller 3 through the displacement sensor 1.4 for precise control of vehicle steering. When the second electro-proportional valve 1.6 is energized and the first electro-proportional valve 1.5 is not energized, the lower position of the electro-proportional valve 1.6 is in the working position, and the depressurized pilot pressure enters the R control chamber of the directional valve. The upper position of the first electro-proportional valve 1.5 is in the working position, and the pressure in the L control chamber of the directional valve 1.1 is connected to the oil tank, pushing the valve core to move to the left. The right position of the directional valve 1.1 is in the working position, and the pressure oil enters the actuator through port A and port C, realizing the right turn of the vehicle.

[0053] Furthermore, the LS port of the directional valve 1.1 is connected to the right control chamber of the dynamic damper 1.3. When the left position of the directional valve 1.1 is in the working position, the load pressure at port B is transmitted to the right control chamber of the dynamic damper through the LS. When the load pressure increases or the load pressure fluctuation increases significantly, the return flow to the oil tank through the dynamic damper 1.3 increases, and the load pressure decreases accordingly, thereby effectively filtering the load impact and playing a neutral position unloading role. At the same time, the dynamic damper 1.3 always maintains a very small flow of the LS in communication with the oil tank, improving the response speed of the priority valve 1.2.

[0054] Example 2

[0055] This embodiment discloses a precise control method for electro-hydraulic steering of engineering machinery, such as Figure 2 , Figure 3 As shown, it includes the following steps:

[0056] When the construction machinery travels in a straight line, the electronic handle 4 is in the neutral position. The electronic handle signal outputs a neutral position signal 0 to the controller via CAN2. The controller calculates and transmits the current value to the first electro-proportional valve 1.5 and the second electro-proportional valve 1.6 via CAN1. The control current received by the electro-proportional valve is the minimum control current. The upper positions of the first electro-proportional valve 1.5 and the second electro-proportional valve 1.6 are in the working position. The control chambers L and R of the directional valve 1.1 are connected to the oil tank. The pressure in the control chambers L and R is zero, and the directional valve 1.1 is in the neutral position. The outlet pressure of the electric pump 2.3 is cut off to the A port of the directional valve 1.1 via the CF port of the priority valve 1.2. The pressure at port A pushes the priority valve 1.2 to the left position, which is in the working position. The flow of the electric pump 2.3 is connected to the EF port.

[0057] When the construction machinery turns left, the electronic handle 4 is moved to the left by a certain position or continuously changes within a certain range on the left. The signal from the electronic handle 4 is transmitted to the controller 3 via the CAN bus signal 2. After receiving the handle signal, the controller 3 converts the percentage of the handle signal into the target displacement of the directional valve 1.1 through the valve core displacement module. Based on the target displacement, a drive current is generated. This drive current is transmitted to the first electro-proportional valve 1.5 and the second electro-proportional valve 1.6 via the CAN bus signal 1.6. The first electro-proportional valve 1.5 is driven by the current and reverses direction. When the lower position is in the working position, the pressure value after depressurization is output to the control chamber L of the directional valve 1.1. At this time, the current value received by the second electro-proportional valve 1.6 is still the minimum current. When the upper position is in the working position, the pressure in the R side control chamber of the directional valve 1.1 is the oil tank pressure. The pilot pressure in the L side control chamber pushes the valve core to move to the right. The left position of the directional valve 1.1 is in the working position. The pressure oil from the electro-pump 2.3 enters the first hydraulic cylinder 6.1 and the second hydraulic cylinder 6.2 through the CF port of the priority valve 1.2, the A port and the B port of the directional valve 1.1, realizing the left turn of the engineering vehicle. The directional valve 1.1 generates actual displacement. The displacement sensor detects the actual displacement value and transmits it to the controller 3 via the CAN1 bus. After comparing it with the target displacement, the PID algorithm adjusts the drive current in real time, thus forming a closed-loop control of the valve core displacement, improving the control accuracy of the engineering machinery steering; at the same time, electronic buffer control of electro-hydraulic steering can be realized based on the feedback of the actual displacement.

[0058] Furthermore, when the construction machinery turns left, the electronic handle 4 is moved to the left by a certain position or continuously changed within a certain range. The electronic handle signal is transmitted to the controller 3 via the bus signal CAN2. After receiving the signal from the electronic handle 4, the controller 3 calculates the pilot pressure and flow matching, and determines the displacement corresponding to the required output flow of the electric pump 2.3. The controller 3 adjusts the displacement of the electric pump 2.3 in real time to meet the flow requirement corresponding to the opening size of the reversing valve 1.1, thereby achieving real-time matching and adjustment between the flow output of the electric pump 2.3 and the flow requirement of the reversing valve 1.1, thus saving energy and reducing consumption.

[0059] When the construction machinery turns right, the electronic handle 4 is moved to the right by a certain position or continuously changed within a certain range. The electronic handle signal is transmitted to the controller 3 via the bus signal CAN2. The controller 3 converts the percentage of the handle signal into the target displacement of the directional valve 1.1 through the valve core displacement module, and generates a drive current based on the target displacement. The drive current is transmitted to the second electro-proportional valve 1.6 via the bus signal CAN1. The second electro-proportional valve 1.6 is driven by the current and reverses. The lower position of the second electro-proportional valve 1.6 is in the working position, and the output... The reduced pressure is sent to the control chamber R of the directional valve 1.1. At this time, the current received by the first electro-proportional valve 1.5 is still the minimum current, and the upper position is the working position. The pressure in the L side control chamber of the directional valve 1.1 is the oil tank pressure. The pilot pressure in the R side control chamber pushes the valve core to move to the left. The right position of the directional valve 1.1 is in the working position. The pressure oil from the electric pump 2.3 enters the first hydraulic cylinder 6.1 and the second hydraulic cylinder 6.2 through the CF port of the priority valve 1.2 and the A and C ports of the directional valve 1.1, realizing the right turn of the engineering vehicle. The directional valve 1.1 generates actual displacement. The displacement sensor detects the actual displacement value and transmits it to the controller 3 via the CAN1 bus. After comparing the actual displacement value with the target displacement, the PID algorithm adjusts the drive current in real time to realize closed-loop control of the valve core displacement and improve the control accuracy of the steering of the engineering machinery. The LS pressure adjustment and pump flow adjustment are the same as above.

[0060] Furthermore, the valve core displacement calculation module is used to calculate the pilot pressure corresponding to the displacement of the directional control valve 1.1 based on the percentage of the handle signal, and to calculate the target displacement of the directional control valve 1.1 valve core in the current state based on the pilot pressure. The flow matching calculation module is used to calculate the flow rate required by the electro-hydraulic steering unit 1 at this time based on the target displacement of the directional control valve 1.1 valve core.

[0061] As described above, when the construction machinery turns right, the controller calculates the required pump displacement based on the signal from the electronic handle 4, by performing calculations on the required flow rate of the electro-hydraulic steering unit and the output flow rate of the electro-hydraulic pump. Based on the pump displacement, the controller calculates the drive current for driving the electro-hydraulic pump proportional control module, which is then transmitted to the electro-hydraulic pump proportional control module via PWM1. The controller then adjusts the electro-hydraulic pump proportional control module in real time according to the handle signal, thereby achieving real-time adjustment of the pump displacement and the handle signal. This satisfies the real-time matching between the flow requirement of the reversing valve 1.1 and the flow output of the electro-hydraulic pump, reducing flow loss and energy consumption.

[0062] The above description is only a preferred embodiment of the present invention. It should be noted that for those skilled in the art, several improvements and modifications can be made without departing from the technical principles of the present invention, and these improvements and modifications should also be considered within the scope of protection of the present invention.

Claims

1. A precision control device for electro-hydraulic steering of engineering machinery, characterized in that it includes an electro-hydraulic steering unit (1), a main pump unit (2), a control unit, an electric control handle unit, a hydraulic auxiliary component unit, and a hydraulic actuator unit (6). The electro-hydraulic steering unit (1) includes a reversing valve (1.1), a priority valve (1.2), a first electro-proportional valve (1.5), and a second electro-proportional valve (1.6). The hydraulic auxiliary unit includes hydraulic pipelines and a hydraulic oil tank (5). The inlet of the main pump unit (2) is connected to the hydraulic oil tank (5), the outlet P of the main pump unit (2) is connected to the inlet of the priority valve (1.2), the CF port of the priority valve (1.2) is connected to the A port of the directional valve (1.1), the B and C ports of the directional valve (1.1) are respectively connected to the hydraulic actuator (6), the LS port of the directional valve (1.1) is connected to the right control chamber of the priority valve (1.2), and the oil port T of the directional valve (1.1) is connected to the hydraulic oil tank (5). The inlet of the first electro-proportional valve (1.5) and the inlet of the second electro-proportional valve (1.6) are connected to the outlet of the pilot oil source block. The return ports of the first electro-proportional valve (1.5) and the second electro-proportional valve (1.6) are connected to the hydraulic oil tank (5). The working port of the first electro-proportional valve (1.5) is connected to the directional valve. The control port L of the first electro-proportional valve (1.1) is connected to the control port R of the directional valve (1.1), the control port of the first electro-proportional valve (1.5) and the control port of the second electro-proportional valve (1.6) are connected to the control unit, and the control unit is also connected to the electric control handle unit and the main pump unit (2). When the control unit controls the first electro-proportional valve (1.5) to be energized, the first electro-proportional valve (1.5) operates in the lower position, the oil inlet and working oil port of the first electro-proportional valve (1.5) are connected, the reversing valve (1.1) operates in the left position, the A port, LS port and B port of the reversing valve (1.1) are connected, and the C port and T port of the reversing valve (1.1) are connected; When the control unit controls the second electro-proportional valve (1.6) to be energized, the second electro-proportional valve (1.6) operates in the lower position, the oil inlet and working oil port of the second electro-proportional valve (1.6) are connected, the reversing valve (1.1) operates in the right position, the A port, LS port and C port of the reversing valve (1.1) are connected, and the B port and T port of the reversing valve (1.1) are connected; When the control unit controls the first electro-proportional valve (1.5) and the second electro-proportional valve (1.6) to be de-energized, the first electro-proportional valve (1.5) and the second electro-proportional valve (1.6) are both in the upper position, the directional valve (1.1) is in the middle position, the control port L and control port R of the directional valve (1.1) are connected to the hydraulic oil tank (5), and the LS port and T port of the directional valve (1.1) are connected. The electro-hydraulic steering unit (1) also includes a displacement sensor (1.4), which is connected to the reversing valve (1.1) and the control unit at both ends. The displacement sensor (1.4) is used to transmit the actual displacement of the valve core of the reversing valve (1.1) to the control unit. The main pump unit (2) includes a pressure sensor (2.1), an electro-proportional control module (2.2), and an electric pump (2.3). The outlet of the electric pump (2.3) is connected to port P, and the inlet of the electric pump (2.3) is connected to the hydraulic oil tank (5). One end of the pressure sensor (2.1) is connected to the outlet of the electric pump (2.3), and the other end is connected to the control unit. The control end of the electro-proportional control module (2.2) is connected to the control port of the electric pump (2.3), and the other end is connected to the control unit.

2. The precision control device for electro-hydraulic steering of engineering machinery according to claim 1, characterized in that, The electro-hydraulic steering unit (1) also includes a dynamic damper (1.3). The right control chamber and D port of the dynamic damper (1.3) are connected to the LS port of the directional valve (1.1), and the E port of the dynamic damper (1.3) is connected to the hydraulic oil tank (5).

3. The precision control device for electro-hydraulic steering of engineering machinery according to claim 2, characterized in that, The electro-hydraulic steering unit (1) also includes a one-way valve (1.7) and a damper (1.9). The oil inlet of the one-way valve (1.7) is connected to the D port of the dynamic damper (1.3), and the oil outlet of the one-way valve (1.7) is connected to the LS port of the directional valve (1.1). One end of the damper (1.9) is connected to the oil inlet of the one-way valve (1.7), and the other end is connected to the CF port of the priority valve (1.2).

4. The precision control device for electro-hydraulic steering of engineering machinery according to claim 1, characterized in that, The electro-hydraulic steering unit (1) also includes a hydraulic control directional valve (1.8), the oil inlet and control port of the hydraulic control directional valve (1.8) are connected to the T port of the directional valve (1.1), and the oil outlet of the hydraulic control directional valve (1.8) is connected to the hydraulic oil tank (5).

5. The precision control device for electro-hydraulic steering of engineering machinery according to claim 1, characterized in that, The control unit includes a controller (3).

6. The precision control device for electro-hydraulic steering of engineering machinery according to claim 1, characterized in that, The electronically controlled handle unit includes an electronic handle (4).

7. The precision control device for electro-hydraulic steering of engineering machinery according to claim 1, characterized in that, The hydraulic actuator (6) includes a first hydraulic cylinder (6.1) and a second hydraulic cylinder (6.2). The rodless chamber of the first hydraulic cylinder (6.1) and the rod chamber of the second hydraulic cylinder (6.2) are connected to port B of the directional valve (1.1). The rod chamber of the first hydraulic cylinder (6.1) and the rodless chamber of the second hydraulic cylinder (6.2) are connected to port C of the directional valve (1.1).

8. A method for precise electro-hydraulic steering control of engineering machinery, characterized in that, The control method using the electro-hydraulic steering precision control device for engineering machinery as described in claim 6 includes the following steps: Based on the percentage of the received electronic handle (4) signal, calculate the corresponding pilot pressure for pushing the valve core displacement of the reversing valve (1.1), and calculate the target displacement of the valve core of the reversing valve (1.1) according to the pilot pressure. Based on the target displacement of the valve core of the reversing valve (1.1), the driving current of the first electro-proportional valve (1.5) and the second electro-proportional valve (1.6) is calculated, and the driving current is output to the first electro-proportional valve (1.5) and the second electro-proportional valve (1.6) to control the movement of the valve core of the reversing valve (1.1). The actual displacement of the valve core of the reversing valve (1.1) transmitted by the displacement sensor (1.4) is compared with the target displacement, and the driving current is adjusted in real time based on the PID algorithm. Based on the target displacement of the valve core of the aforementioned reversing valve (1.1), calculate the flow rate required by the electro-hydraulic steering unit (1) at this time; Based on the required flow rate of the electro-hydraulic steering unit (1), the output flow rate of the electro-hydraulic pump (2.3) is calculated, and the drive current of the electro-proportional control module (2.2) is calculated according to the output flow rate of the electro-hydraulic steering unit (2.3). The drive current is output to the electro-proportional control module (2.2) to control the flow output of the electro-hydraulic pump (2.3) to match the flow demand of the reversing valve (1.1) in real time.

9. The method for precise electro-hydraulic steering control of engineering machinery according to claim 8, characterized in that, Includes the following steps: When the electronic handle (4) is moved to the left at a certain position or continuously changed within a certain range on the left, the output current controls the first electro-proportional valve (1.5) to work in the lower position, the second electro-proportional valve (1.6) to work in the upper position, and the directional valve (1.1) to work in the left position.

10. The method for precise electro-hydraulic steering control of engineering machinery according to claim 8, characterized in that, Includes the following steps: When the electronic handle (4) is moved to the right to a certain position or continuously changed within a certain range on the right side, the output current controls the first electro-proportional valve (1.5) to work in the upper position, the second electro-proportional valve (1.6) to work in the lower position, and the directional valve (1.1) to work in the right position.

11. The method for precise electro-hydraulic steering control of engineering machinery according to claim 8, characterized in that, Includes the following steps: When the electronic handle (4) is in the neutral position, the output current controls the first electro-proportional valve (1.5) to work in the upper position, the second electro-proportional valve (1.6) to work in the upper position, and the directional valve (1.1) to work in the neutral position.

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