A loader automatic unloading dual-cylinder synchronous control method and system

Abstract

The present invention relates to the field of automatic control technology, and more particularly to a method and system for synchronously controlling dual cylinders for automatic unloading of a loader. The method comprises collecting real-time data from a rodless cavity pressure sensor, a rod cavity pressure sensor, a three-position four-way proportional valve, a speed sensor, and a displacement sensor. Based on the displacement data collected by the displacement sensors and specified displacement parameters, the method combines the state-space equations of the hydraulic cylinder piston rod position control system with Lyapunov stability theory to adjust the hydraulic cylinder's external load compensation, piston rod displacement speed, and hydraulic cylinder displacement accuracy parameters to achieve automatic unloading of the loader. The present invention addresses the problem that traditional dual-cylinder synchronous control algorithms have difficulty maintaining their original control accuracy under variable load conditions and have poor adaptability.

Description

Technical Field

[0001] The present invention relates to the field of automatic control technology, and in particular to a method and system for synchronously controlling dual cylinders for automatic unloading of a loader. Background Art

[0002] A loader is a highly efficient construction machine. It's primarily used for shoveling, loading, transporting, and digging loose, accumulated materials. It can also be used to organize and level sites, as well as for hauling. Equipped with the appropriate working device, it can also perform digging, lifting, and loading and unloading operations. It's widely used in urban construction, mining, railways, highways, hydropower, oil fields, national defense, and airport construction, among other projects. It plays a vital role in accelerating project progress, ensuring quality, improving working conditions, increasing work efficiency, and reducing construction costs.

[0003] Traditional loaders operate through a variety of actions, including driving, loading, and unloading. Unloading is the most frequent and requires the highest precision. Currently, unloading is primarily performed manually, requiring manual control of the lift and dump cylinders for coordinated movement. This places heavy workload on operators, and drivers often experience fatigue after long hours of work, leading to incomplete unloading and low efficiency.

[0004] As a result, the demand for automation in loaders is growing. Since unloading is the most frequent operation, the demand for automatic unloading functionality is increasing. Loaders typically use traditional dual-cylinder synchronous control systems to achieve these unloading operations. However, traditional dual-cylinder synchronous control algorithms struggle to maintain control accuracy under variable load conditions and have poor adaptability. Summary of the Invention

[0005] Aiming at the deficiencies of existing algorithms, the present invention solves the problem that the traditional dual-cylinder synchronous control algorithm is difficult to maintain the original control accuracy under variable load conditions and has poor adaptability.

[0006] The technical solution adopted by the present invention is: a loader automatic unloading dual-cylinder synchronous control method, comprising the following steps:

[0007] Step 1: Collect real-time data of the rodless cavity pressure sensor, rod cavity pressure sensor, three-position four-way proportional valve, speed sensor and displacement sensor;

[0008] Furthermore, the real-time data includes: dual cylinder data of the dump cylinder and the lifting cylinder.

[0009] Step 2: Based on the displacement data collected by the displacement sensor and the specified displacement parameters, the backstepping control algorithm is used to realize automatic unloading of the loader.

[0010] Furthermore, the backstepping control algorithm combines the state space equation of the hydraulic cylinder piston rod position control system with the Lyapunov stability theory, and realizes automatic unloading of the loader by adjusting the compensation of the hydraulic cylinder subjected to external load force, the piston rod displacement speed, and the hydraulic cylinder displacement accuracy parameters.

[0011] Furthermore, the state space equation of the cylinder piston rod position control system is:

[0012]

[0013] Where m is the system load mass; x1 is the output displacement of the hydraulic cylinder; x2 is the output speed of the hydraulic cylinder; x3 is the internal force of the hydraulic cylinder; A1 is the working area of the hydraulic cylinder rodless cavity; A2 is the working area of the hydraulic cylinder rod cavity; P1 is the oil pressure of the hydraulic cylinder rodless cavity; P2 is the oil pressure of the hydraulic cylinder rod cavity; V 01 V is the initial volume of the rodless chamber of the hydraulic cylinder; 02 is the initial volume of the rodless chamber of the hydraulic cylinder; B is the effective viscous damping coefficient; C t Actuator leakage coefficient; β e Hydraulic oil elastic modulus; F L is the external load force borne by the hydraulic cylinder; Q1 is the oil flow rate of the hydraulic cylinder rodless chamber; Q2 is the oil flow rate of the hydraulic cylinder rod chamber; Q1 and Q2 are expressed as shown in formula (3):

[0014]

[0015] Where k q is the flow coefficient; k i is the valve core current gain; s() is a custom function, and u is the input electrical signal.

[0016] Furthermore, the formula of the backstepping control algorithm is:

[0017]

[0018] Where u is the input electrical signal, m is the system load mass; x1 is the output displacement of the hydraulic cylinder; x2 is the output speed of the hydraulic cylinder; x3 is the internal force of the hydraulic cylinder; A1 is the working area of the hydraulic cylinder rodless cavity; A2 is the working area of the hydraulic cylinder rod cavity; P1 is the oil pressure of the hydraulic cylinder rodless cavity; P2 is the oil pressure of the hydraulic cylinder rod cavity; F L V is the external load force borne by the hydraulic cylinder; 01 V is the initial volume of the rodless chamber of the hydraulic cylinder; 02 is the initial volume of the rodless chamber of the hydraulic cylinder; B is the effective viscous damping coefficient; C t Actuator leakage coefficient; β e Hydraulic oil elastic modulus; k qis the flow coefficient; k i is the spool current gain; x 1d 、x 2d 、x 3d are the specified displacement, ideal velocity, and ideal internal force of the hydraulic cylinder respectively; e1, e2, and e3 are the displacement error, velocity error, and internal force error respectively; k1, k2, and k3 are the control parameters.

[0019] The loader automatic unloading dual-cylinder synchronous control system includes: a bucket cylinder 2, a first three-position four-way proportional valve 10, a first rodless cavity pressure sensor 11, a first rod cavity pressure sensor 12, a first speed sensor 13, a first displacement sensor 14 and a first force sensor 15. The outlet of the oil source 22 is connected to the oil inlet P of the first three-position four-way proportional valve 10 through a hydraulic pipeline; the oil outlet A of the first three-position four-way proportional valve 10 is connected to the rodless cavity oil port of the bucket cylinder 2 through a hydraulic pipeline; the first rodless cavity pressure sensor 11 is connected in series between the first three-position four-way proportional valve 10 and the hydraulic pipeline of the bucket cylinder 2; the first speed sensor 13 and the first force sensor are installed on the piston rod of the bucket cylinder 2. 15 and the first displacement sensor 14; the rod chamber oil port of the bucket cylinder 2 is connected to the oil outlet B of the first three-position four-way proportional valve 10 through a hydraulic pipeline; a first rod chamber pressure sensor 12 is connected in series between the hydraulic pipeline of the bucket cylinder 2 and the first three-position four-way proportional valve 10, and the return oil port T of the first three-position four-way proportional valve 10 is connected to the oil tank 23 through a hydraulic pipeline; when the piston rod of the bucket cylinder 2 needs to move, the first three-position four-way proportional valve 10 is in the left position or the right position, so that the hydraulic oil at both ends of the bucket cylinder 2 cavity flows to push the piston rod to move; when the piston rod of the bucket cylinder 2 needs to be stationary, the first three-position four-way proportional valve 10 is in the middle position, so that the hydraulic oil cannot flow at both ends of the bucket cylinder 2 cavity.

[0020] Furthermore, it also includes: a lifting cylinder 7, a second three-position four-way proportional valve 16, a second rodless cavity pressure sensor 17, a second rod cavity pressure sensor 18, a second speed sensor 19, a second displacement sensor 20 and a second force sensor 21, the outlet of the oil source 22 is connected to the oil inlet P of the second three-position four-way proportional valve 16 through a hydraulic pipeline; the oil outlet A of the second three-position four-way proportional valve 16 is connected to the oil port of the rodless cavity of the lifting cylinder 7 through a hydraulic pipeline; a second rodless cavity pressure sensor 17 is connected in series between the second three-position four-way proportional valve 16 and the hydraulic pipeline of the lifting cylinder 7; a second speed sensor 19, a second force sensor 21 and a second Displacement sensor 20; the lifting cylinder 7 has a rod chamber oil port and is connected to the oil outlet B of the second, three-position, four-way proportional valve 16 through a hydraulic pipeline; a second rod chamber pressure sensor 17 is connected in series between the lifting cylinder 7 and the hydraulic pipeline of the second, three-position, four-way proportional valve 16, and the return oil port T of the second, three-position, four-way proportional valve 16 is connected to the oil tank 23 through a hydraulic pipeline; when the piston rod of the lifting cylinder 7 needs to move, the second, three-position, four-way proportional valve 16 is in the left position or the right position, so that the hydraulic oil at both ends of the cavity of the lifting cylinder 7 flows to push the piston rod to move; when the piston rod of the lifting cylinder 7 needs to be stationary, the second, three-position, four-way proportional valve 16 is in the middle position, so that the hydraulic oil cannot flow at both ends of the cavity of the lifting cylinder 7.

[0021] Furthermore, it also includes a controller 9, the output terminals of the controller 9 are connected to the electromagnet input terminals of the first three-position four-way proportional valve 10 and the second three-position four-way reversing valve 16 through wires, and the movement of the three-position four-way proportional valve is controlled by the backstepping control algorithm in the controller 9, thereby driving the piston rod to reach a specified displacement.

[0022] Furthermore, the conversion formula between the motion displacement of the three-position four-way directional valve and the electrical signal is:

[0023] x v =k i u (1)

[0024] Where x v , k i , u are the proportional valve spool displacement, spool current gain and input electrical signal respectively.

[0025] Beneficial effects of the present invention:

[0026] 1. It not only realizes the complete automatic unloading process of the loader, improves the working efficiency, but also reduces the labor intensity;

[0027] 2. The backstepping control algorithm is used to control the synchronous movement of the dual cylinders and implement closed-loop feedback control for automatic unloading. Compared with other feedback control algorithms, the backstepping control algorithm controls the next step of the hydraulic cylinder piston rod based on the real-time motion data fed back by the hydraulic cylinder. In the complex working environment of the loader, the backstepping control algorithm has stronger adaptability, higher accuracy and better stability;

[0028] 3. It has a manual and automatic switching function. When an unexpected situation occurs, it can take into account manual control and complete manual / automatic integrated control. Therefore, the invention is reliable, practical and highly automated. BRIEF DESCRIPTION OF THE DRAWINGS

[0029] Figure 1 This is a diagram of the automatic unloading mechanism of a loader of the prior art;

[0030] Figure 2 This is a structural diagram of the automatic unloading dual-cylinder synchronous control system for a loader of the present invention;

[0031] Figure 3 This is a hydraulic principle diagram of the automatic unloading dual-cylinder synchronous control system for a loader of the present invention;

[0032] Figure 4 This is a schematic diagram of the automatic unloading dual-cylinder synchronous control process of the loader of the present invention;

[0033] Figure 5 This is a block diagram of the automatic unloading dual-cylinder synchronous control of the loader of the present invention;

[0034] Figure 6 This is a hydraulic principle diagram of the hydraulic cylinder piston rod position control of the present invention;

[0035] Figure 1 Middle: 1. Part of the vehicle body, 2. Dump cylinder, 3. Crank, 4. Straight rod, 5. Bucket, 6. Boom, 7. Lift cylinder;

[0036] Figure 2 Middle: 8, operation box, 9, controller, 10, first three-position four-way proportional valve, 11, first rodless cavity pressure sensor, 12, first rod cavity pressure sensor, 13, first speed sensor, 14, first displacement sensor, 15, first force sensor, 16, second three-position four-way proportional valve, 17, second rodless cavity pressure sensor, 18, second rod cavity pressure sensor, 19, second speed sensor, 20, second displacement sensor, 21, second force sensor;

[0037] Figure 3 Chinese: 22, oil source, 23, fuel tank. DETAILED DESCRIPTION

[0038] The present invention will be further described below in conjunction with the accompanying drawings and embodiments. This figure is a simplified schematic diagram, which only illustrates the basic structure of the present invention in a schematic manner, and therefore only shows the components related to the present invention.

[0039] like Figure 1 As shown, the automatic unloading mechanism of the loader in the prior art includes: a partial body 1, a dump bucket cylinder 2, a crank 3, a straight rod 4, a bucket 5, a boom 6, and a lifting cylinder 7. The tail of the dump bucket cylinder 2, the tail of the lifting cylinder 7, and the left end of the boom 6 are connected to the partial body 1 through a hinge, the piston rod of the lifting cylinder 7 is connected to the middle end of the boom 6 through a hinge, the right end of the boom 6 is connected to the tail of the bucket 5 through a hinge, the middle tail of the boom 6 is connected to the middle part of the crank 3 through a hinge, the left end of the crank 3 is connected to the piston rod of the dump bucket cylinder 2 through a hinge, the right end of the crank 3 is connected to the left end of the straight rod 4 through a hinge, and the right end of the straight rod 4 is connected to the top of the bucket 5 through a hinge.

[0040] The working principle of automatic unloading is that when the piston rods of the dump bucket cylinder 2 and the lifting cylinder 7 are extended at the same time, the bucket 5 is raised and turned outward to unload the materials onto the loading truck. When the piston rods of the dump bucket cylinder 2 and the lifting cylinder 7 are retracted at the same time, the bucket 5 is lowered and retracted to its original position.

[0041] like Figure 2A loader automatic unloading dual-cylinder synchronous control system includes an operation box 8, a controller 9, a first three-position four-way proportional valve 10, a first rodless cavity pressure sensor 11, a first rod cavity pressure sensor 12, a bucket oil cylinder 2, a first speed sensor 13, a first displacement sensor 14, a first force sensor 15, a second three-position four-way proportional valve 16, a second rodless cavity pressure sensor 17, a second rod cavity pressure sensor 18, a lifting oil cylinder 7, a second speed sensor 19, a second displacement sensor 20 and a second force sensor 21. The operation box 8 is equipped with operation buttons, a handle and a display screen. The operation buttons, handle and display screen on the operation box 8 are connected to the input terminals of the controller 9 through wires, and the output terminals of the controller 9 are respectively connected to the electromagnet input terminals of the first three-position four-way proportional valve 10 and the second three-position four-way reversing valve 16 through wires. The first rodless cavity pressure sensor 11, the first rod cavity pressure sensor 12, the first speed sensor 13, the first displacement sensor 14, the first force sensor 15, the second rodless cavity pressure sensor 17, the second rod cavity The output terminals of the pressure sensor 18, the lifting cylinder 7, the second speed sensor 19, the second displacement sensor 20, and the second force sensor 21 are respectively connected to the input terminals of the controller 9. The first three-position four-way proportional valve 10 is connected to the bucket cylinder 2 through two hydraulic pipelines. The first rodless cavity pressure sensor 11 is connected in series between the oil inlet pipelines of the two, and the first rod cavity pressure sensor 12 is installed between the oil return pipelines of the two. The first displacement sensor 14 for measuring the real-time displacement of the piston rod of the bucket cylinder 2, the first speed sensor 13 for real-time speed, and the first force sensor 15 for real-time force are installed on the piston rod of the bucket cylinder 2. The second three-position four-way proportional valve 16 is connected to the lifting cylinder 7 through two hydraulic pipelines. The second rodless cavity pressure sensor 17 is connected in series between the oil inlet pipelines of the two, and the second rod cavity pressure sensor 18 is installed between the oil return pipelines of the two. The second displacement sensor 20 for measuring the real-time displacement of the piston rod of the lifting cylinder 7, the second speed sensor 15 for real-time speed, and the second force sensor 21 for real-time force are installed on the piston rod of the lifting cylinder 7.

[0042] like Figure 3The figure shows the hydraulic principle diagram of the dual-cylinder synchronous control system of the present invention. The control oil circuits of the bucket cylinder 2 and the lifting cylinder 7 are symmetrical and have the same principle. The control oil circuit of the bucket cylinder 2 is taken as an example for explanation. The outlet of the oil source 22 is connected to the oil inlet P of the first three-position four-way proportional valve 10 through a hydraulic pipeline, and the oil outlet A of the first three-position four-way proportional valve 10 is connected to the rodless cavity oil port of the bucket cylinder 2 through a hydraulic pipeline. A first rodless cavity pressure sensor 11 is connected in series between the two hydraulic pipelines. A first speed sensor 13, a first force sensor 15 and a first displacement sensor 14 are installed on the piston rod of the bucket cylinder 2. The rod cavity oil port of the bucket cylinder 2 is connected to the oil outlet B of the first three-position four-way proportional valve 10 through a hydraulic pipeline. A first rod cavity pressure sensor 12 is connected in series between the two hydraulic pipelines. The return oil port T of the first three-position four-way proportional valve 10 is connected to the oil tank 23 through a hydraulic pipeline. The key to the synchronous control of the two cylinders lies in the control of the three-position four-way proportional valve. At the same time, the initial state of the three-position four-way proportional valve is the O-type neutral function, thereby realizing the function of maintaining the position of the two cylinders. When the piston rod of the bucket cylinder 2 needs to move, the first three-position four-way proportional valve 10 is in the left position or the right position, so that the hydraulic oil at both ends of the bucket cylinder 2 cavity flows to push the piston rod to move. When the piston rod of the bucket cylinder 2 needs to be stationary, the first three-position four-way proportional valve 10 is in the neutral position, so that the hydraulic oil cannot flow at both ends of the bucket cylinder 2 cavity. The original oil in the rodless cavity and the rod cavity of the bucket cylinder 2 interact with each other to put the piston rod in a state of force balance, and the piston rod stops moving and remains stationary.

[0043] like Figure 4 As shown, a loader automatic unloading dual-cylinder synchronous control method, the specific steps are as follows:

[0044] Step 1. Initialization: Initialize the control system of the loader and check whether the input and output parameters of the controller 9, the first three-position four-way proportional valve 10, the first rodless cavity pressure sensor 11, the first rod cavity pressure sensor 12, the bucket cylinder 2, the first speed sensor 13, the first displacement sensor 14, the first force sensor 15, the second three-position four-way proportional valve 16, the second rodless cavity pressure sensor 17, the second rod cavity pressure sensor 18, the lifting cylinder 7, the second speed sensor 19, the second displacement sensor 20, and the second force sensor 21 are normal. If not, do not proceed to the next step and check for faults. If normal, continue to proceed to the next step.

[0045] Step 2, collect data: The controller 9 collects data of the first three-position four-way proportional valve 10, the first rodless cavity pressure sensor 11, the first rod cavity pressure sensor 12, the bucket cylinder 2, the first speed sensor 13, the first displacement sensor 14, the first force sensor 15, the second three-position four-way proportional valve 16, the second rodless cavity pressure sensor 17, the second rod cavity pressure sensor 18, the lifting cylinder 7, the second speed sensor 19, the second displacement sensor 20, and the second force sensor 21 and displays them on the display screen of the operating box 8. Check whether the display screen can display the sensor data. If not, proceed to the next step to check for faults; if normal, continue to proceed to the next step.

[0046] Step 3, manual / automatic mode judgment: judge whether it is automatic mode by the manual / automatic switch button on the operation box 8. If it is manual mode, go to step 4.1; if it is automatic mode, go to step 4.2;

[0047] Step 4.1, manual mode: After the manual remote control mode is turned on, set the controller 9 to the manual control program state and proceed to step 4.1.1;

[0048] Step 4.1.1, manual control: The first three-position four-way proportional valve 10 and the second three-position four-way proportional valve 16 are output with electrical signals by controlling the handle of the operating box 8. The expression of the valve core displacement of the three-position four-way proportional valve and the electrical signal is shown in formula (1). Manual control is mainly to observe the movement process of the loader with the naked eye or observe the feedback values of the first displacement sensor 14 and the second displacement sensor 20 on the display screen of the operating box 8 to judge whether the piston rod has reached the specified displacement or completed the expected action. If it has reached, the next step can be carried out. If not, it is continuously adjusted by the operating handle.

[0049] x v =k i u (1)

[0050] Where x v , k i , u are the proportional valve spool displacement, spool current gain and input electrical signal respectively.

[0051] Step 4.2, automatic mode: After the automatic mode is turned on, set the controller 9 to the automatic control program state and enter step 4.2.1;

[0052] Step 4.2.1, parameter setting: set the specified displacement of the dual cylinder and the backstepping control algorithm parameters.

[0053] Step 4.2.2, real-time data collection: The controller 9 collects data of the first three-position four-way proportional valve 10, the first rodless cavity pressure sensor 11, the first rod cavity pressure sensor 12, the tipping cylinder 2, the first speed sensor 13, the first displacement sensor 14, the first force sensor 15, the second three-position four-way proportional valve 16, the second rodless cavity pressure sensor 17, the second rod cavity pressure sensor 18, the lifting cylinder 7, the second speed sensor 19, the second displacement sensor 20, and the second force sensor 21 in each scanning cycle.

[0054] Step 4.2.2, dual-cylinder synchronization automatic adjustment module: This module is implemented by implanting the backstepping control algorithm into the controller 9, such as Figure 5 As shown, the dual-cylinder synchronous control strategy of the present invention adopts a parallel control structure. Two parallel control algorithms output two parallel electrical signals to control the first three-position four-way proportional valve 10 and the second three-position four-way proportional valve 16 respectively. Taking the bucket cylinder as an example, the controller has collected the sensor parameters of each scanning cycle. Then, the controller performs backstepping control algorithm calculation based on these parameters to output electrical signals to the proportional valve to control the bucket cylinder piston rod. The bucket cylinder hydraulic control system is simplified as follows Figure 6 As shown in the figure, P s is the inlet pressure of the three-position four-way proportional valve, P r is the system return oil pressure (usually set to 0), P1 is the pressure of the hydraulic cylinder rodless cavity, P2 is the pressure of the hydraulic cylinder rod cavity, Q1 and Q2 are the flow rates flowing into and out of the first three-position four-way proportional valve 10 respectively, F L It is the external load force borne by the hydraulic cylinder.

[0055] according to Figure 6 The state space equation of the hydraulic cylinder piston rod position control system is listed as shown in formula (2):

[0056]

[0057] Where m is the system load mass, kg; x1 is the output displacement of the hydraulic cylinder, collected by the displacement sensor, in meters; x2 is the output speed of the hydraulic cylinder, collected by the speed sensor, in m / s; x3 is the internal force of the hydraulic cylinder, in N, expressed as x3 = A1P1-A2P2, A1 is the working area of the hydraulic cylinder rodless cavity, in m 2 , A2 is the working area of the hydraulic cylinder rod cavity, m 2 , P1 is the oil pressure in the rodless chamber of the hydraulic cylinder, Pa, P2 is the oil pressure in the rod chamber of the hydraulic cylinder, Pa; V 01 is the initial volume of the rodless chamber of the hydraulic cylinder, m 3 ; V 02 is the initial volume of the rodless chamber of the hydraulic cylinder, m 3 ; B is the effective viscous damping coefficient; C tActuator leakage coefficient; β e Hydraulic oil elastic modulus; F L is the external load force borne by the hydraulic cylinder, collected by the force sensor, N; Q1 is the oil flow rate of the rodless chamber of the hydraulic cylinder, m 3 / s; Q2 hydraulic cylinder rod chamber oil flow, m 3 / s; Q1 and Q2 are expressed as shown in formula (3):

[0058]

[0059] Where k q is the flow coefficient; k i is the valve core current gain; s() is a custom function, u is the input electrical signal, when u is greater than 0, the output of this function is 1, otherwise it is 0.

[0060] The backstepping control algorithm model for the hydraulic cylinder piston rod position control is shown in formula (4). It is an adaptive control algorithm derived from the system state space equation and Lyapunov stability theory. As can be seen from the formula, the output of the algorithm depends on the command variable, the measurement variable and the fixed parameters of the hydraulic system components. From this point of view, compared with the traditional control algorithm, the algorithm has good adaptability to working conditions and superior compensation effect. The algorithm formula is:

[0061]

[0062] Where u is the input electrical signal, m is the system load mass, kg; x1 is the output displacement of the hydraulic cylinder, collected by the displacement sensor, m; x2 is the output speed of the hydraulic cylinder, collected by the speed sensor, m / s; x3 is the internal force of the hydraulic cylinder, N, expressed as x3 = A1P1-A2P2; A1 is the working area of the hydraulic cylinder rodless cavity, m 2 ; A2 is the working area of the hydraulic cylinder rod cavity, m 2 ; P1 is the oil pressure in the rodless chamber of the hydraulic cylinder, Pa; P2 is the oil pressure in the rod chamber of the hydraulic cylinder, Pa; F L V is the external load force borne by the hydraulic cylinder, which is collected by the force sensor; 01 is the initial volume of the rodless chamber of the hydraulic cylinder, m 3 ; V 02 is the initial volume of the rodless chamber of the hydraulic cylinder, m 3 ; B is the effective viscous damping coefficient; C t Actuator leakage coefficient; β e Hydraulic oil elastic modulus; k q is the flow coefficient; k i is the spool current gain; x 1d 、x 2d 、x 3dare the specified displacement, ideal velocity, and ideal internal force of the hydraulic cylinder, respectively, and x 1d is the input control quantity, x 2d 、x 3d is the virtual control quantity; e1, e2, and e3 are displacement error, velocity error, and internal force error respectively; k1, k2, and k3 are control parameters. By adjusting these three parameters, the size of the control input can be adjusted.

[0063] The backstepping control algorithm is written into the controller 9 in parallel to control the first three-position four-way proportional valve 10 and the second three-position four-way proportional valve 16 respectively, thereby realizing the synchronous control of the loader's automatic unloading dual-cylinders. The key to the algorithm lies in the adjustment of parameters k1, k2, and k3 to control various properties of the piston rod displacement. The k3 value mainly participates in compensating the hydraulic cylinder for the external load force. The larger the value, the greater the compensation of the hydraulic cylinder piston rod displacement. In the synchronous control, k3 needs to be limited to improve the precision of the dual-cylinder synchronous control. Generally, the k3 range is set to 0-30; the k2 value mainly participates in controlling the piston rod displacement speed. The larger the value, the greater the piston rod displacement speed. In order to reduce the overshoot of the piston rod displacement, the k2 value is controlled within 200; the k1 value mainly participates in the hydraulic cylinder displacement accuracy, that is, the fit with the specified displacement. The larger the k1 value, the stronger the hydraulic cylinder piston rod displacement fit ability. In the parallel structure, the higher the control precision of the dual-cylinder synchronization, the k1 value is generally controlled within 100,000.

[0064] The controller 9 calculates and provides an electrical signal to the three-position four-way proportional valve according to each scanning cycle, and the piston rod follows the movement. Generally, it takes multiple cycles for the piston rod to reach the specified displacement. The controller 9 will make a judgment in each scanning cycle. If the piston rod displacement reaches the specified displacement value, the controller 9 will not provide an electrical signal and the piston rod movement will stop. If the specified displacement value is not reached, the controller 9 will continue to collect real-time data from the sensor, continue to calculate the control signal to the three-position four-way proportional valve, and the piston rod will continue to move.

[0065] Step 5: The automatic unloading operation is completed and proceed to the next step.

[0066] With the above-described preferred embodiments of the present invention as a guide, and with reference to the above description, relevant personnel are fully capable of making various changes and modifications without departing from the technical scope of this invention. The technical scope of this invention is not limited to the contents of the specification and must be determined according to the scope of the claims.

Claims

1. A loader automatic unloading dual-cylinder synchronous control method, characterized in that: The following steps are involved: Step 1: Collect real-time data of the rodless cavity pressure sensor, rod cavity pressure sensor, three-position four-way proportional valve, speed sensor and displacement sensor; Real-time data includes: dump cylinder and lift cylinder data; Step 2: Based on the collected displacement data and the specified displacement parameters, the backstepping control algorithm is used to realize automatic unloading of the loader; The backstepping control algorithm combines the state space equation of the hydraulic cylinder piston rod position control system with the Lyapunov stability theory. By setting the parameters of the hydraulic cylinder's external load compensation, piston rod displacement speed, and hydraulic cylinder displacement accuracy, the loader can achieve automatic unloading. The state space equation of the hydraulic cylinder piston rod position control system is: Where m is the system load mass; x1 is the output displacement of the hydraulic cylinder; x2 is the output speed of the hydraulic cylinder; x3 is the internal force of the hydraulic cylinder; A1 is the working area of the hydraulic cylinder rodless cavity; A2 is the working area of the hydraulic cylinder rod cavity; P1 is the oil pressure of the hydraulic cylinder rodless cavity; P2 is the oil pressure of the hydraulic cylinder rod cavity; V 01 V is the initial volume of the rodless chamber of the hydraulic cylinder; 02 is the initial volume of the rodless chamber of the hydraulic cylinder; B is the effective viscous damping coefficient; C t Actuator leakage coefficient; β e Hydraulic oil elastic modulus; F L is the external load force borne by the hydraulic cylinder; Q1 is the oil flow rate of the hydraulic cylinder rodless chamber; Q2 is the oil flow rate of the hydraulic cylinder rod chamber; Q1 and Q2 are expressed as shown in formula (3): Where k q is the flow coefficient; k i is the valve core current gain; s() is a custom function, u is the input electrical signal; P s is the inlet pressure of the three-position four-way proportional valve, P r is the system return oil pressure; The formula of the backstepping control algorithm is: Where u is the input electrical signal, m is the system load mass; x1 is the output displacement of the hydraulic cylinder; x2 is the output speed of the hydraulic cylinder; x3 is the internal force of the hydraulic cylinder; A1 is the working area of the hydraulic cylinder rodless cavity; A2 is the working area of the hydraulic cylinder rod cavity; P1 is the oil pressure of the hydraulic cylinder rodless cavity; P2 is the oil pressure of the hydraulic cylinder rod cavity; F L V is the external load force borne by the hydraulic cylinder; 01 V is the initial volume of the rodless chamber of the hydraulic cylinder; 02 is the initial volume of the rodless chamber of the hydraulic cylinder; B is the effective viscous damping coefficient; C t Actuator leakage coefficient; β e Hydraulic oil elastic modulus; k q is the flow coefficient; k i is the spool current gain; x 1d 、x 2d 、x 3d are the specified displacement, ideal velocity, and ideal internal force of the hydraulic cylinder respectively; e1, e2, and e3 are the displacement error, velocity error, and internal force error respectively; k1, k2, and k3 are the control parameters.

2. A system using the loader automatic unloading dual-cylinder synchronous control method according to claim 1, characterized in that: include: The tipping cylinder (2), the first three-position four-way proportional valve (10), the first rodless cavity pressure sensor (11), the first rod cavity pressure sensor (12), the first speed sensor (13), the first displacement sensor (14) and the first force sensor (15); the oil source (22) outlet is connected to the oil inlet P of the first three-position four-way proportional valve (10) through a hydraulic pipeline; the oil outlet A of the first three-position four-way proportional valve (10) is connected to the rodless cavity oil port of the tipping cylinder (2) through a hydraulic pipeline; the first rodless cavity pressure sensor (11) is connected in series between the first three-position four-way proportional valve (10) and the hydraulic pipeline of the tipping cylinder (2); the first speed sensor (13), the first force sensor (15) and the first displacement sensor are installed on the piston rod of the tipping cylinder (2). sensor (14); the oil port of the rod chamber of the bucket oil cylinder (2) is connected to the oil outlet B of the first three-position four-way proportional valve (10) through a hydraulic pipeline; a first rod chamber pressure sensor (12) is connected in series between the hydraulic pipeline of the bucket oil cylinder (2) and the first three-position four-way proportional valve (10), and the oil return port T of the first three-position four-way proportional valve (10) is connected to the oil tank (23) through a hydraulic pipeline; when the piston rod of the bucket oil cylinder (2) needs to move, the first three-position four-way proportional valve (10) is in the left position or the right position, so that the hydraulic oil at both ends of the bucket oil cylinder (2) cavity flows to push the piston rod to move; when the piston rod of the bucket oil cylinder (2) needs to be stationary, the first three-position four-way proportional valve (10) is in the middle position, so that the hydraulic oil cannot flow at both ends of the bucket oil cylinder (2) cavity; The invention also includes: a lifting oil cylinder (7), a second three-position four-way proportional valve (16), a second rodless cavity pressure sensor (17), a second rod cavity pressure sensor (18), a second speed sensor (19), a second displacement sensor (20) and a second force sensor (21); the outlet of the oil source (22) is connected to the oil inlet P of the second three-position four-way proportional valve (16) through a hydraulic pipeline; the oil outlet A of the second three-position four-way proportional valve (16) is connected to the rodless cavity oil port of the lifting oil cylinder (7) through a hydraulic pipeline; a second rodless cavity pressure sensor (17) is connected in series between the second three-position four-way proportional valve (16) and the hydraulic pipeline of the lifting oil cylinder (7); the second speed sensor (19), the second force sensor (21) and the second displacement sensor (22) are installed on the piston rod of the lifting oil cylinder (7); a displacement sensor (20); a rod cavity oil port of the lifting oil cylinder (7) is connected to an oil outlet B of the second three-position four-way proportional valve (16) through a hydraulic pipeline; a second rod cavity pressure sensor (18) is connected in series between the hydraulic pipeline of the lifting oil cylinder (7) and the second three-position four-way proportional valve (16); and an oil return port T of the second three-position four-way proportional valve (16) is connected to an oil tank (23) through a hydraulic pipeline; when the piston rod of the lifting oil cylinder (7) needs to move, the second three-position four-way proportional valve (16) is in the left position or the right position, thereby allowing the hydraulic oil at both ends of the lifting oil cylinder (7) cavity to flow and push the piston rod to move; when the piston rod of the lifting oil cylinder (7) needs to be stationary, the second three-position four-way proportional valve (16) is in the middle position, thereby preventing the hydraulic oil from flowing at both ends of the lifting oil cylinder (7) cavity; The invention also includes a controller (9), wherein the output terminals of the controller (9) are respectively connected to the electromagnet input terminals of the first three-position four-way proportional valve (10) and the second three-position four-way proportional valve (16) through electric wires, and the movement of the three-position four-way proportional valve is controlled by the backstepping control algorithm in the controller (9), thereby driving the piston rod to reach a specified displacement.

3. The automatic unloading dual-cylinder synchronous control system for a loader according to claim 2 is characterized in that: The conversion formula between the motion displacement and the electrical signal of the second three-position four-way directional valve (16) and the first three-position four-way proportional valve (10) is: x v =k i u (1) Where x v , k i , u are the proportional valve spool displacement, spool current gain and input electrical signal respectively.

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