CN113942963B - A load sensitive forklift load port independent control system and method - Google Patents

Abstract

The purpose of the present invention is to overcome the problem that the prior art cannot simultaneously meet the requirements of forklift control performance and energy-saving performance, and provide a load-sensitive forklift load port independent control system and method, so as to ensure the working reliability of the forklift under any working conditions, and at the same time improve Energy-saving features and control features of forklift hydraulic systems. In order to achieve the above purpose, the following technical solutions are adopted: including mast lifting hydraulic cylinder, joystick, mast tilting hydraulic cylinder, load sensing pump, regulator, ECU controller and fork side shifting hydraulic cylinder, and also including lifting valve group, The tilt valve group and the side shift valve group are respectively configured to control the flow rate, pressure and Flow rate; the backstep adaptive robust control algorithm is used to alleviate the problem of low control accuracy caused by the nonlinearity and uncertainty of the hydraulic system; the combined pump and valve control each hydraulic cylinder to meet the flow demand under any working condition.

Description

A load sensitive forklift load port independent control system and method

technical field

The invention relates to the field of transport vehicle control, in particular to a load-sensitive forklift load port independent control system and method.

Background technique

Forklifts play an important role in modern logistics and warehousing and distribution, and the hydraulic system, as the execution system for forklift functions, has a decisive impact on the performance of forklifts.

The forklift hydraulic system is mainly composed of subsystems such as mast lifting, mast tilting, and fork side shifting. The specified actions are realized by controlling the expansion and contraction of the hydraulic cylinders (ie hydraulic cylinders) of each subsystem. At present, the forklift hydraulic system mostly adopts a load-sensitive control system in which a single pump supplies oil and multiple hydraulic cylinders work at the same time, that is, according to the pressure margin between the pump outlet pressure and the load pressure, the flow of the pump is adaptively adjusted by monitoring the pressure and flow. To reduce bypass throttling loss. However, under the condition of a large difference in load inertia, flow saturation is prone to occur, that is, the sum of the flow required by each hydraulic cylinder is greater than the maximum output flow of the pump, resulting in the flow being preferentially supplied to the hydraulic cylinder with a smaller load, and the large load hydraulic cylinder. Insufficient flow supply slows down or even stops working. In addition, when the working conditions change, the load-sensitive system at different operating points under a single control strategy cannot meet the requirements of control performance and energy-saving performance at the same time. Therefore, it is particularly important to design a forklift hydraulic system and control method that can not only ensure the working requirements of each hydraulic cylinder under any working condition, but also improve energy-saving characteristics and control performance.

Modern forklifts mostly use a load-sensing control system in which a single pump supplies oil and multiple hydraulic cylinders work at the same time. Under the condition of a large difference in load inertia, the flow and pressure matching of the load-sensing system at different operating points under a single control strategy cannot satisfy the control performance at the same time. and energy-saving performance requirements.

The working conditions of forklifts are complex and changeable, and flow saturation is prone to occur under the condition of large difference in load inertia, that is, the sum of the flow required by each hydraulic cylinder is greater than the maximum output flow of the pump, resulting in the flow being preferentially supplied to the hydraulic cylinder with a smaller load. The load hydraulic cylinder slows down or even stops working due to insufficient flow supply.

Load-sensitive multi-way valve spool coupling linkage, non-linear problems of hydraulic system, dynamic changes of hydraulic oil characteristics, and reduction of hydraulic cylinder control accuracy caused by external interference of load.

At present, the existing technologies for forklift hydraulic load-sensing control systems are as follows: (1) Taking Chinese patent 201410365226.1 as an example, the work stability of the load-sensing system is improved and energy loss is reduced by optimizing the structure of the multi-way valve, but the multi-way valve has mechanical linkage Phenomenon, only one oil port of the oil inlet and outlet can be controlled, and there is still room for improvement in control accuracy and energy utilization. (2) Taking Zhao Junwei's "Study on Flow Distribution Control of Multi-hydraulic Cylinder Load Sensing System" as an example, the work reliability of each hydraulic cylinder of the load sensing system is improved by studying the flow distribution algorithm of each hydraulic cylinder, but the control algorithm adopted is affected by the system The influence of nonlinearity is greater, and the design of the control algorithm can be further optimized.

Contents of the invention

The purpose of the present invention is to overcome the problem that the prior art cannot simultaneously meet the requirements of forklift control performance and energy-saving performance, and provide a load-sensitive forklift load port independent control system and method, so as to ensure the working reliability of the forklift under any working conditions, and at the same time improve Energy-saving features and control features of forklift hydraulic systems.

In order to achieve the above object, the present invention adopts the following technical solutions:

A load-sensing independent control system for the load port of a forklift is characterized in that it includes a mast lifting hydraulic cylinder, a joystick, a mast tilting hydraulic cylinder, a load-sensing pump, a regulator, an ECU controller, and a fork side-moving hydraulic cylinder;

It also includes a lifting valve group configured to control the flow, pressure and flow rate of hydraulic oil in the rodless chamber and the rod chamber of the mast lifting hydraulic cylinder;

It also includes a tilting valve group configured to control the flow, pressure and flow rate of hydraulic oil in the rodless chamber and the rod chamber of the gantry tilting hydraulic cylinder;

It also includes a side shift valve group configured to control the flow, pressure and flow rate of hydraulic oil in the rodless chamber and the rod chamber of the fork side shift hydraulic cylinder;

The joystick is connected to the ECU controller, the mast lifting hydraulic cylinder is connected to the lifting valve group, the mast tilting hydraulic cylinder is connected to the tilting valve group, the fork side shifting hydraulic cylinder is connected to the side shifting valve group, the lifting valve group, the tilting valve group and the side shifting valve group are connected. The valve group is connected in parallel to the load sensing pump, the load sensing pump is connected to the regulator, and the regulator is connected to the ECU controller.

Further, the lift valve group, tilt valve group and side shift valve group all use three-position three-way electro-hydraulic proportional valves; the valve body is equipped with a spool position sensor; all three-position three-way electro-hydraulic proportional valves are independent of each other, According to the requirements of the system, the controller outputs electric signals to directly control the opening and direction of the valve port. The mast lifting hydraulic cylinder, mast tilting hydraulic cylinder and fork side moving hydraulic cylinder are equipped with displacement sensors, which are configured to detect the piston rod. position and send the position information back to the ECU controller.

Further, the lift valve group includes a control valve for the rodless cavity of the gantry lifting hydraulic cylinder and a control valve for the rod cavity of the gantry lifting hydraulic cylinder, which are respectively connected to the rodless cavity and the rod cavity of the gantry lifting hydraulic cylinder. The tilting valve group includes the rodless chamber control valve of the mast tilting hydraulic cylinder and the rod chamber control valve of the mast tilting hydraulic cylinder respectively connected with the rodless chamber and the rod chamber of the mast tilting hydraulic cylinder, and the side shifting valve group includes The rodless chamber control valve of the fork side shift hydraulic cylinder and the rod chamber control valve of the fork side shift hydraulic cylinder are respectively connected with the rodless chamber and the rod chamber of the fork side shift hydraulic cylinder.

Further, a plurality of pressure sensors are respectively the first pressure sensor, the second pressure sensor, the third pressure sensor, the fourth pressure sensor, the fifth pressure sensor and the sixth pressure sensor and the pump outlet pressure sensor, wherein the mast lifts The rod chamber and the rodless chamber of the hydraulic cylinder are respectively connected to the ECU controller through the first pressure sensor and the second pressure sensor. The sensor is connected to the ECU controller. The rodless chamber and the rod chamber of the fork side-shift hydraulic cylinder are respectively connected to the ECU controller through the fifth pressure sensor and the sixth pressure sensor. Among them, the lift valve group, tilt valve group, and side shift valve The group is connected to the pump outlet pressure sensor in parallel, the pump outlet pressure sensor is connected to the ECU controller, and the pump outlet pressure sensor is connected in parallel with the load sensing pump.

A load-sensitive method for independently controlling the load port of a forklift, using the above-mentioned system, is characterized in that it includes the following steps:

Step 1: Input the ideal position manipulation command, the ECU controller judges the load direction and movement direction of each hydraulic cylinder, and calculates the ideal driving force F _di , i=1, 2, 3, 1 represents the lifting valve group, 2 represents the tilting valve group, 3 Represents the side-shift valve group, based on which the optimal working mode of each hydraulic cylinder is judged; the optimal working mode includes: when the F _di direction is consistent with the extending direction of the piston rod of the hydraulic cylinder, the rodless cavity is speed controlled, and the rod The chamber is for pressure control to maintain a lower pressure value; when the direction of F _di is opposite to the extension direction of the piston rod of the hydraulic cylinder, the rodless chamber is for pressure control to maintain a lower pressure value, and the rod chamber is for speed control; F _di is At zero time, close the valve group;

Step 2: The pressure and position sensors of each hydraulic cylinder output data to the ECU controller. According to the ideal driving force F _di , adopt the backstepping adaptive robust position tracking control algorithm to determine the control law of the rodless chamber speed control and the rod chamber speed The control law of the control and the ideal flow rate of the speed control, the control law of the pressure control of the rodless cavity, the control law of the pressure control of the rod cavity and the ideal flow rate of the pressure control, and at the same time output each hydraulic cylinder according to the optimal working mode of the step 1 The ideal control flow of hydraulic cylinder includes speed control ideal flow and pressure control ideal flow;

Step 3: Based on the ideal control flow of the two chambers of each hydraulic cylinder output in step 2, output the control signal u _p to adjust the displacement of the load-sensitive pump to realize the main control of the flow; The control signal adjusts the valve opening of each valve group to realize the precise control of the two-chamber flow of each hydraulic cylinder;

Step 4: Determine whether the actual flow rate meets the requirements, and if it is satisfied, the control is completed; otherwise, each hydraulic cylinder feeds back the values of the pressure sensor and displacement sensor, and repeats steps 2 and 3 until the flow rate of each hydraulic cylinder matches the ideal control flow rate, while ensuring The difference between system pressure and load pressure is maintained at the set value to realize the function of electro-hydraulic load sensitivity.

Further, the specific method for judging whether the actual flow rate meets the requirements in step 4 is to calculate the pressure flow rate of each hydraulic pressure in real time through the calibrated pressure-flow characteristic curve of the proportional valve according to the pressure difference at both ends of the valve port and the voltage of each electro-hydraulic proportional valve. The actual flow rate of the cylinder, if the absolute value of the difference between the actual flow rate and the ideal control flow rate is less than the preset error value, the control requirements are met.

Therefore, the present invention has the following beneficial effects: (1) The present invention uses two three-position three-way electro-hydraulic proportional valves to replace the multi-way valves in the traditional system, which simplifies the system structure, reduces the cost of valve parts, and increases the freedom of hydraulic cylinder control It provides a better hardware foundation for the control strategy that is more in line with the actual working conditions, and improves the control performance; (2) a load-sensitive forklift load port independent control technology of the present invention reduces the traditional multi-hydraulic cylinder load-sensitive system. The energy loss caused by the excessive pressure difference at the valve port of the low-pressure hydraulic cylinder can improve the energy utilization rate; (3) The backstep adaptive robust control algorithm can effectively alleviate the problem of low control accuracy caused by the nonlinearity and uncertainty of the hydraulic system ;Combined pump and valve composite control to accurately control the flow and pressure of the two chambers of each hydraulic cylinder to meet the flow requirements of each hydraulic cylinder under any working condition.

Description of drawings

Fig. 1 is a connection diagram of the control system of the present invention.

Fig. 2 is a flowchart of the control method of the present invention.

In the figure: 1. Gantry lifting hydraulic cylinder, 2. Joystick, 3. Gantry tilting hydraulic cylinder, 4. Pump outlet pressure sensor, 5. Load sensitive pump, 6. Regulator, 7. ECU controller, 8. Fork side shift hydraulic cylinder,

1.1. Gantry lifting hydraulic cylinder rodless cavity control valve, 1.2. Gantry lifting hydraulic cylinder rod cavity control valve, 3.1. Gantry tilting hydraulic cylinder rodless cavity control valve, 3.1. Gantry tilting hydraulic cylinder rod cavity control Valve, 8.1, fork side shift hydraulic cylinder rodless chamber control valve, 8.1, fork side shift hydraulic cylinder rod chamber control valve, 4.1, first pressure sensor, 4.2, second pressure sensor, 4.3, third pressure sensor , 4.4, the fourth pressure sensor, 4.5, the fifth pressure sensor, 4.6, the sixth pressure sensor.

Detailed ways

The present invention will be further described below in conjunction with the accompanying drawings and specific embodiments.

In the embodiment shown in Fig. 1, Fig. 2,

A load-sensitive independent control system for the load port of a forklift, including a mast lifting hydraulic cylinder 1, a joystick 2, a mast tilting hydraulic cylinder 3, a load-sensing pump 5, a regulator 6, an ECU controller 7, and a fork side-moving hydraulic pressure The cylinder 8 also includes a lift valve group, a tilt valve group, and a side shift valve group, which are respectively configured as rodless chambers for controlling the mast lift hydraulic cylinder 1, the mast tilt hydraulic cylinder 3, and the fork side shift hydraulic cylinder 8 and the flow rate, pressure and flow rate of the hydraulic oil in the rod cavity; the mast lifting hydraulic cylinder 1, the mast tilting hydraulic cylinder 3 and the fork side moving hydraulic cylinder 8 are equipped with displacement sensors, which are configured to detect the position of the piston rod x ₁ , x ₂ , x ₃ and send the position information back to the ECU controller 7 . The joystick is connected to the ECU controller 7, the mast lifting hydraulic cylinder 1 is connected to the lifting valve group, the mast tilting hydraulic cylinder 3 is connected to the tilting valve group, the fork side shifting hydraulic cylinder 8 is connected to the side shifting valve group, the lifting valve group, and the tilting valve The group and the side shift valve group are connected in parallel to the load sensing pump 5, the load sensing pump 5 is connected to the regulator 6, and the regulator 6 is connected to the ECU controller 7.

The above-mentioned lifting valve group, tilting valve group and side shifting valve group all use three-position three-way electro-hydraulic proportional valves; the valve body is equipped with a spool position sensor; all three-position three-way electro-hydraulic proportional valves are independent of each other, according to the needs of the system The electrical signal output by the controller directly controls the opening and direction of the valve port. The lifting valve group includes a rodless cavity control valve 1.1 of the gantry lifting hydraulic cylinder and a rod cavity control valve 1.2 of the gantry lifting hydraulic cylinder connected to the rodless cavity and the rod cavity of the gantry lifting hydraulic cylinder 1 respectively. The tilting valve group includes the rodless cavity control valve 3.1 of the gantry tilting hydraulic cylinder and the rod cavity control valve 3.2 of the gantry tilting hydraulic cylinder respectively connected to the rodless cavity and the rod cavity of the gantry tilting hydraulic cylinder 3. The valve group includes a rodless chamber control valve 8.1 of the fork sideshift hydraulic cylinder and a rod chamber control valve 8.2 of the fork sideshift hydraulic cylinder respectively connected to the rodless chamber and the rod chamber of the fork sideshift hydraulic cylinder 8 .

The above-mentioned load-sensitive forklift load port independent control system also includes a plurality of pressure sensors, respectively the first pressure sensor 4.1, the second pressure sensor 4.2, the third pressure sensor 4.3, the fourth pressure sensor 4.4, the fifth pressure sensor 4.5 and the sixth pressure sensor. The pressure sensor 4.6 and the pump outlet pressure sensor 4, wherein the rod cavity and the rodless cavity of the gantry lifting hydraulic cylinder 1 are respectively connected to the ECU controller 7 through the first pressure sensor 4.1 and the second pressure sensor 4.2, and the gantry tilting hydraulic cylinder The rodless chamber and the rod chamber of 3 are respectively connected to the ECU controller 7 through the third pressure sensor 4.3 and the fourth pressure sensor 4.4, and the rodless chamber and the rod chamber of the fork side shift hydraulic cylinder 8 are respectively passed through the fifth pressure sensor 4.5. The sixth pressure sensor 4.6 is connected to the ECU controller 7, wherein the lifting valve group, the tilting valve group and the side shifting valve group are connected in parallel to the pump outlet pressure sensor 4, and the pump outlet pressure sensor 4 is connected to the ECU controller 7, and the pump outlet The pressure sensor 4 is connected in parallel with the load sensing pump 5 .

The basic operation process of the above-mentioned system is as follows: the joystick 2 is manually manipulated to output control signals to the ECU controller 7 through the CAN bus; the multiple pressure sensors monitor the pressure of the rod chamber and the rodless chamber of each hydraulic cylinder , the spool position sensor monitors the spool position and sends it back to the ECU controller 7 through the CAN bus; the plurality of pressure sensors detect the pressure at the outlet of the load-sensitive pump 5 and sends it to the ECU controller 7 through the CAN bus; the ECU controller 7 Output control instructions according to the control algorithm, the regulator 6 receives the control instructions to adjust the pressure and flow of the load sensitive pump 5, and each valve group receives the control instructions to adjust the opening and direction of the valve ports.

A load-sensitive method for independently controlling the load port of a forklift, using the above-mentioned system, includes the following steps:

Step 1: Input the ideal position manipulation command, the ECU controller judges the load direction and movement direction of each hydraulic cylinder, and calculates the ideal driving force F _di , i=1, 2, 3, 1 represents the lifting valve group, 2 represents the tilting valve group, 3 Represents the side-shift valve group, based on which the optimal working mode of each hydraulic cylinder is judged; the optimal working mode includes: when the F _di direction is consistent with the extending direction of the piston rod of the hydraulic cylinder, the rodless cavity is speed controlled, and the rod The chamber is for pressure control to maintain a lower pressure value; when the direction of F _di is opposite to the extension direction of the piston rod of the hydraulic cylinder, the rodless chamber is for pressure control to maintain a lower pressure value, and the rod chamber is for speed control; F _di is At zero time, close the valve group;

Step 2: The pressure and position sensors of each hydraulic cylinder output data to the ECU controller. According to the ideal driving force F _di , adopt the backstep adaptive robust position tracking control algorithm to determine the control laws L _{s, i1} and Its ideal control flow rate Q _sd,i1 ; the control law L _s,i2 of rod chamber speed control and its ideal control flow rate Q _sd,i2 , and the control law L _{p of rodless chamber pressure control, i1} and its ideal control flow rate Q _pd,i1 , the control law L _p,i2 of rod cavity pressure control and the ideal control flow Q _pd,i2 , and output the ideal control flow Q _{d of each hydraulic cylinder according to the optimal working mode of each hydraulic cylinder in step 1, ij} , including speed control ideal flow Q _{sd, ij} and pressure control ideal flow Q _pd.ij ;

Step 3: Based on the ideal control flow of the two chambers of each hydraulic cylinder output in step 2, output the control signal u _p to adjust the displacement of the load-sensitive pump to realize the main control of the flow; The control signal adjusts the valve opening of each valve group to realize the precise control of the two-chamber flow of each hydraulic cylinder;

Step 4: Determine whether the actual flow rate meets the requirements, and if it is satisfied, the control is completed; otherwise, each hydraulic cylinder feeds back the values of the pressure sensor and displacement sensor, and repeats steps 2 and 3 until the flow rate of each hydraulic cylinder matches the ideal control flow rate, while ensuring The difference between system pressure and load pressure is maintained at the set value to realize the function of electro-hydraulic load sensitivity.

The specific method for judging whether the actual flow rate meets the requirements in step 4 is to calculate the actual flow rate of each hydraulic cylinder in real time through the calibrated pressure-flow characteristic curve of the proportional valve according to the pressure difference at both ends of the valve port and the voltage of each electro-hydraulic proportional valve. Q _r,ij , if ∣Q _r,ij -Q _d,ij ∣≤Z, Z is the preset error value, then the control requirements are met.

The foregoing embodiments are only used to illustrate the technical solutions of the present invention, rather than to limit them; although the present invention has been described in detail with reference to the foregoing embodiments, those of ordinary skill in the art should understand that: it can still be used for the foregoing embodiments Modifications are made to the recorded technical solutions, or equivalent replacements are made to some or all of the technical features; and these modifications or replacements do not make the essence of the corresponding technical solutions depart from the scope of the technical solutions of the embodiments of the present invention.

Claims (4)

1. A load-sensitive forklift load port independent control method, characterized in that, The method adopts a load-sensitive forklift load port independent control system, and the control system includes a mast lifting hydraulic cylinder, a joystick, a mast tilting hydraulic cylinder, a load-sensitive pump, a regulator, an ECU controller, and a fork side shifting hydraulic cylinder; also includes a lifting valve group configured to control the flow, pressure and flow rate of hydraulic oil in the rodless chamber and the rod chamber of the mast lifting hydraulic cylinder; also includes a tilting valve group configured for Control the flow, pressure and flow rate of hydraulic oil in the rodless chamber and the rod chamber of the mast tilt hydraulic cylinder; also include the side shift valve group, which is configured to control the rodless chamber and the rod of the fork side shift hydraulic cylinder The flow, pressure and flow rate of the hydraulic oil in the chamber; the joystick is connected to the ECU controller, the mast lifting hydraulic cylinder is connected to the lifting valve group, the mast tilting hydraulic cylinder is connected to the tilting valve group, and the fork side shifting hydraulic cylinder is connected to the side shifting valve group , the lift valve group, tilt valve group and side shift valve group are connected in parallel to the load sensing pump, the load sensing pump is connected to the regulator, and the regulator is connected to the ECU controller; The method comprises the steps of: Step 1: Input the ideal position manipulation command, the ECU controller judges the load direction and movement direction of each hydraulic cylinder, and calculates the ideal driving force F _di , i=1, 2, 3, 1 represents the lifting valve group, 2 represents the tilting valve group, 3 Represents the side-shift valve group, based on which the optimal working mode of each hydraulic cylinder is judged; the optimal working mode includes: when the F _di direction is consistent with the extending direction of the piston rod of the hydraulic cylinder, the rodless cavity is speed controlled, and the rod The chamber is for pressure control to maintain a lower pressure value; when the direction of F _di is opposite to the extension direction of the piston rod of the hydraulic cylinder, the rodless chamber is for pressure control to maintain a lower pressure value, and the rod chamber is for speed control; F _di is At zero time, close the valve group; Step 2: The pressure and position sensors of each hydraulic cylinder output data to the ECU controller. According to the ideal driving force F _di , adopt the backstepping adaptive robust position tracking control algorithm to determine the control laws L _{s, i1} and Its ideal control flow Q _sd,i1 ; the control law L _s,i2 of rod chamber speed control and its ideal control flow Q _sd,i2 , and the control law L _p,i1 of rodless chamber pressure control and its ideal control flow Q _pd,i1 , the control law L _p,i2 of rod cavity pressure control and the ideal control flow Q _pd,i2 , and output the ideal control flow Q _{d of each hydraulic cylinder according to the optimal working mode of each hydraulic cylinder in step 1, ij} , including speed control ideal flow Q _sd,ij and pressure control ideal flow Q _pd.ij ; Step 3: Based on the ideal control flow of the two chambers of each hydraulic cylinder output in step 2, output the control signal up to adjust the displacement of the load-sensitive pump to realize the main control of the flow; output the control of the lift valve group, tilt valve group, and side-shift valve group Signal to adjust the valve port opening of each valve group to realize the precise control of the two-chamber flow of each hydraulic cylinder; Step 4: Determine whether the actual flow rate meets the requirements, and if it is satisfied, the control is completed; otherwise, each hydraulic cylinder feeds back the values of the pressure sensor and displacement sensor, and repeats steps 2 and 3 until the flow rate of each hydraulic cylinder matches the ideal control flow rate, while ensuring The difference between system pressure and load pressure is maintained at the set value to realize the function of electro-hydraulic load sensitivity; The specific method for judging whether the actual flow rate meets the requirements in step 4 is to calculate the actual flow rate of each hydraulic cylinder in real time through the calibrated pressure-flow characteristic curve of the proportional valve according to the pressure difference at both ends of the valve port and the voltage of each electro-hydraulic proportional valve. Q _r,ij , if ∣Q _r,ij -Q _d,ij ∣≤Z, Z is the preset error value, then the control requirements are met. 2. A load-sensitive forklift load port independent control method according to claim 1, characterized in that, the lift valve group, the tilt valve group and the side-shift valve group all use three-position three-way electro-hydraulic proportional valves; The body is equipped with a spool position sensor; all three-position three-way electro-hydraulic proportional valves are independent of each other. According to the requirements of the system, the controller outputs electrical signals to directly control the opening and direction of the valve port. The hydraulic cylinder and the hydraulic cylinder for lateral movement of the cargo fork are equipped with displacement sensors, which are configured to detect the position of the piston rod and send the position information back to the ECU controller. 3. A load-sensitive independent control method for the load port of a forklift according to claim 1, wherein the lifting valve group includes masts respectively connected to the rodless chamber and the rod chamber of the mast lifting hydraulic cylinder The rodless cavity control valve of the lifting hydraulic cylinder and the rod cavity control valve of the gantry lifting hydraulic cylinder, the tilting valve group includes the rodless hydraulic cylinder of the gantry tilting hydraulic cylinder connected with the rodless cavity and the rod cavity of the gantry tilting hydraulic cylinder respectively. Cavity control valve and mast tilt hydraulic cylinder rod cavity control valve, the side shift valve group includes the rodless cavity control valve of the fork side shift hydraulic cylinder which is respectively connected to the rodless cavity and rod cavity Valves and fork side shift hydraulic cylinders have rod cavity control valves. 4. A load-sensitive independent control method for the load port of a forklift according to claim 1, further comprising a plurality of pressure sensors being respectively a first pressure sensor, a second pressure sensor, a third pressure sensor, a fourth pressure sensor, and a pressure sensor. Pressure sensors, the fifth pressure sensor and the sixth pressure sensor and the pump outlet pressure sensor, wherein the rod chamber and rodless chamber of the gantry lifting hydraulic cylinder are respectively connected to the ECU controller through the first pressure sensor and the second pressure sensor, and the door The rodless chamber and the rod chamber of the frame tilt hydraulic cylinder are respectively connected to the ECU controller through the third pressure sensor and the fourth pressure sensor, and the rodless chamber and the rod chamber of the fork side shift hydraulic cylinder are respectively connected through the fifth pressure sensor, The sixth pressure sensor is connected to the ECU controller, in which the lift valve group, the tilt valve group, and the side shift valve group are connected in parallel to the pump outlet pressure sensor, and the pump outlet pressure sensor is connected to the ECU controller, and the pump outlet pressure sensor is connected to the load sensing pump. parallel relationship.

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