High-frequency switch valve control multi-cylinder synchronous jacking control system and control method

Abstract

The invention belongs to the technical field of fluid transmission and control, and particularly relates to a high-frequency switch valve control multi-cylinder synchronous jacking control system and method. The control system comprises jacking equipment, N sets of hydraulic cylinders arranged below the jacking equipment and a hydraulic system used for controlling the N sets of hydraulic cylinders to stretch out and draw back. The hydraulic system comprises an oil tank, a filter, a hydraulic pump, a motor, an overflow valve, a first one-way valve, an energy accumulator, N high-frequency switch digital valve sets and N double-acting hydraulic control one-way valves, wherein the N high-frequency switch digital valve sets and the N double-acting hydraulic control one-way valves are in one-to-one correspondence with the N hydraulic cylinders. Any hydraulic cylinder passes through a hydraulic cylinder control loop composed of a high-frequency switch digital valve set and a double-acting hydraulic control one-way valve, the N sets of hydraulic cylinders adopt the same oil tank, main oil inlet path and main oil return path, it is guaranteed that the hydraulic cylinder control loop has high switching frequency, the displacement control precision is improved, and the working efficiency is improved. The problems that in the prior art, a multi-cylinder synchronous jacking control system is poor in synchronization precision, poor in system stability and low in response speed are solved.

Description

Technical Field

[0001] The invention belongs to the technical field of fluid transmission and control, and in particular relates to a high-frequency switch valve-controlled multi-cylinder synchronous lifting control system and a control method. Background Art

[0002] The hydraulic drive system plays an important role in the transportation of some heavy equipment due to its advantages such as high power density and good dynamic performance, including synchronous lifting, position adjustment and precise positioning. In this process, the performance of synchronous lifting will directly affect the safety of the equipment during transportation, transportation efficiency and the stable operation of the entire system.

[0003] At present, there are three main ways to use synchronous lifting systems: First, use a mechanical synchronization system; connect the ends of the actuators mechanically so that they can correct deviations with each other during operation to ensure the synchronous lifting requirements. The process of using mechanical synchronization is relatively simple, but the synchronization accuracy is poor in actual applications. At the same time, it has poor adaptability in working environments with variable loads and requires frequent maintenance. Second, the use of a proportional system can improve the accuracy of synchronous lifting, but the proportional valves commonly used in proportional systems are highly sensitive to oil and the system adjustment process is relatively complicated. Third, the use of a specific hydraulic synchronous control system can reduce dependence on electricity and ensure the stability of the system, but it requires the design of a more complex hydraulic system circuit, and there are also problems such as greater difficulty in installation and maintenance. Summary of the invention

[0004] The purpose of the present invention is to overcome the defects of poor synchronization accuracy, poor system stability and slow response speed in the prior art, and to provide a high-frequency switch valve-controlled multi-cylinder synchronous jacking control system and control method with high control accuracy, fast response speed and good stability, which can meet the needs of multi-cylinder synchronous jacking equipment during transportation of heavy equipment.

[0005] The technical solution adopted by the present invention to solve the technical problem is:

[0006] As a first aspect, a high-frequency switch valve-controlled multi-cylinder synchronous jacking control system includes a jacking device, N groups of hydraulic cylinders arranged below the jacking device, and a hydraulic system for controlling the extension and retraction of the N groups of hydraulic cylinders through a control unit;

[0007] The hydraulic system includes an oil tank, a filter, a hydraulic pump, a motor, a relief valve, a first one-way valve, an accumulator, and N groups of high-frequency switch digital valve groups and N groups of double-acting hydraulically controlled one-way valves corresponding to the N groups of hydraulic cylinders;

[0008] The motor is connected to the hydraulic pump through a coupling; the filter is placed in the oil tank, and the oil outlet of the filter is connected to the oil inlet fluid circuit of the hydraulic pump; the overflow valve is connected to the oil outlet of the hydraulic pump, and is also connected to the oil inlet of the first one-way valve on the main oil inlet circuit; the oil outlet of the first one-way valve is connected to the oil circuit of the hydraulic accumulator to form a main oil inlet circuit, and the output port of the main oil inlet circuit is connected to the oil inlet A of the N groups of high-frequency switching digital valve groups; the oil outlet of any group of the high-frequency switching digital valve groups is connected to the oil inlet fluid circuit of the corresponding hydraulically controlled one-way valve, and the two oil outlets of a group of double-acting hydraulically controlled one-way valves are respectively connected to the oil inlet and oil outlet fluid circuits of the corresponding hydraulic cylinder.

[0009] Specifically, the high-frequency switching digital valve group includes a first high-speed switching valve, a second high-speed switching valve, a third high-speed switching valve and a fourth high-speed switching valve;

[0010] When the hydraulic cylinder performs an extension action, the oil inlet circuit of the hydraulic cylinder includes the hydraulic oil in the main oil inlet circuit flowing through the first high-speed switch valve and the double-acting hydraulic control one-way valve in sequence, and then entering the oil from the oil inlet of the hydraulic cylinder; the oil return circuit of the hydraulic cylinder includes the hydraulic oil flowing out from the oil outlet of the hydraulic cylinder, flowing through the double-acting hydraulic control one-way valve and the fourth high-speed switch valve in sequence and merging into the main oil return circuit;

[0011] When the hydraulic cylinder performs a contraction action, the oil inlet circuit of the hydraulic cylinder includes the hydraulic oil in the main oil inlet circuit flowing through the third high-speed switching valve and the double-acting hydraulically controlled one-way valve in sequence, and then flowing into the oil outlet of the hydraulic cylinder; the oil outlet circuit of the hydraulic cylinder includes the hydraulic oil flowing out from the oil inlet of the hydraulic cylinder, flowing through the double-acting hydraulically controlled one-way valve and the second high-speed switching valve in sequence, and merging into the main return oil circuit.

[0012] Specifically, the control unit includes:

[0013] The first data acquisition module is used to collect the oil pressure of the main oil inlet and the oil pressure of the main oil return in real time.

[0014] N groups of second data acquisition modules are arranged in one-to-one correspondence with the hydraulic cylinders, and are used to collect the oil pressure on the oil inlet line, the hydraulic pressure on the oil outlet line, and the telescopic displacement of the hydraulic cylinders;

[0015] A main control module, used for receiving and processing the data information transmitted by the first data acquisition module, and setting the target displacement and the working mode of the hydraulic cylinder;

[0016] N groups of independent control modules, corresponding one to one with the hydraulic cylinders, for receiving data information transmitted by the corresponding second data acquisition module, and outputting data of the high-frequency switch digital valve group and double-acting hydraulic control check valve corresponding to the hydraulic cylinders;

[0017] The main control module receives and processes the data information output by the first data acquisition module and the data output by the independent control module, and determines and calculates the target displacement and working mode corresponding to each group of hydraulic cylinders at the next moment in combination with the target height data, calculates the input signal of each group of digital valves by inputting the target displacement into the RBF neural network sliding mode controller, and sends the control output signal and the working mode signal to each group of independent control modules.

[0018] Specifically, the first data acquisition module includes:

[0019] A main oil inlet line sensor is arranged on the main oil inlet line and is used to detect the oil pressure on the main oil inlet line in real time;

[0020] A main oil return line sensor is arranged on the main oil return line and is used to detect the oil pressure on the main oil return line in real time;

[0021] The main oil inlet circuit sensor and the main oil return circuit sensor are both communicatively connected to the main control module.

[0022] Specifically, the second data acquisition module includes:

[0023] A rodless chamber pressure sensor is arranged on the oil inlet line of the hydraulic cylinder and is used to detect the oil pressure on the oil inlet line of the hydraulic cylinder in real time;

[0024] A rod cavity pressure sensor is arranged on the oil outlet line of the hydraulic cylinder and is used to detect the oil pressure on the oil outlet line of the hydraulic cylinder in real time;

[0025] A displacement sensor is arranged on the hydraulic cylinder and is used to detect the telescopic displacement of the hydraulic cylinder in real time;

[0026] The rodless cavity pressure sensor, the rod cavity pressure sensor and the displacement sensor are all communicatively connected to the corresponding independent control modules; the independent control module is communicatively connected to the main control module.

[0027] Specifically, the main control module determines and calculates the target displacement and working mode corresponding to each group of hydraulic cylinders at the next moment, including the following steps:

[0028] Step 1: Construct a mathematical model of the synchronous lifting hydraulic system;

[0029] Step 2: Establish a sliding mode control algorithm using the mathematical model constructed in step 1;

[0030] Step 3: Calculate the target displacement and working mode corresponding to each hydraulic cylinder according to the sliding mode control algorithm constructed in step 2; the working mode includes an adjustment mode and a normal mode.

[0031] Specifically, the mathematical model of the synchronous lifting hydraulic system constructed in step 1 includes the following steps:

[0032] S101. Establish the flow equations through the corresponding high-frequency switching digital valve group when a single group of hydraulic cylinders are extended and retracted:

[0033]

[0034] Among them, A 1 A is the area of ​​the rod cavity; 2 is the area of ​​the rodless cavity; Q 1 is the oil inlet flow rate; Q 2 is the oil outlet flow rate; C dv is the flow coefficient of the digital valve; A dv is the flow area of ​​the digital valve; P s is the oil supply pressure; P 0 is the return oil pressure; u is the controller signal output; P 1 is the rodless cavity pressure; P 2 is the rod cavity pressure; x dv is the equivalent valve core displacement of the digital valve; ρ is the hydraulic oil density;

[0035] S102. Construct the flow continuity equation of the hydraulic system:

[0036]

[0037] Among them, x p is the displacement of the hydraulic cylinder piston rod; C ip is the leakage coefficient of the hydraulic cylinder; C ec is the external leakage coefficient of the hydraulic cylinder, A 1 A is the rod cavity area of ​​the hydraulic cylinder. 2 is the rodless chamber area of ​​the hydraulic cylinder, P 1 is the rodless chamber pressure of the hydraulic cylinder, P 2 is the rod chamber pressure of the hydraulic cylinder, V 1 V is the volume of the rodless chamber of the hydraulic cylinder. 2 is the volume of the rod chamber of the hydraulic cylinder; β is the bulk elastic modulus;

[0038] Hydraulic cylinder pressure P 1 , P 2 The relational expression is:

[0039]

[0040] Where P L represents the load pressure, η represents the ratio of the effective area of ​​the hydraulic cylinder with rod cavity and the rodless cavity; P s Represents the hydraulic system oil supply pressure, P L Represents the load pressure drop of the hydraulic system;

[0041] S103. The balance equation of the hydraulic cylinder's output force and external load is described as follows:

[0042]

[0043] In the formula, m represents the equivalent mass of the hydraulic cylinder; Represents the acceleration of the hydraulic cylinder; Represents the moving speed of the hydraulic cylinder; x p Represents the displacement of the hydraulic cylinder; B P represents the damping coefficient of the hydraulic cylinder piston; K represents the spring stiffness of the hydraulic cylinder; F L Represents the external load of the hydraulic cylinder; P s Represents the oil supply pressure of the hydraulic system;

[0044] Assume the state variable of the system: x 1 =x p , The state balance equation of the hydraulic cylinder is established using the above formula:

[0045]

[0046] In the formula, f(x 2 , x 3 )=a 1 x 2 +a 2 x 3 ; The system disturbance is defined as: G is a simplified expression whose specific definition is:

[0047]

[0048] Among them, C dv is the flow coefficient of the digital valve; A dv is the flow area of ​​the digital valve; u is the controller signal output; P 0 is the return oil pressure of the hydraulic system; P 1 is the rodless cavity pressure; P 2 is the rod cavity pressure; P S Supply oil pressure to the hydraulic system; x dv is the equivalent valve core displacement of the digital valve; ρ is the hydraulic oil density.

[0049] Specifically, the establishment of the sliding mode control algorithm includes the following process:

[0050] S201. Define the system error calculation:

[0051] e=x d -x p ; In the formula, x d is the target displacement value of the hydraulic cylinder; xp is the actual displacement value of the hydraulic cylinder.

[0052] S202. Construct sliding surface design formula:

[0053] In the formula, μ 1 is the sliding surface function coefficient 1, μ 2 is the sliding surface function coefficient 2, e is the displacement tracking error, is the first-order derivative of the displacement tracking error, is the second-order derivative of the displacement tracking error.

[0054] Taking the first-order derivative of s, we get:

[0055]

[0056] make The equivalent control rate of sliding mode control can be obtained as follows:

[0057]

[0058] The switching control rate selects the exponential approach rate:

[0059] u zs =-k 1 sgn(s)-k 2 s;

[0060] In the formula, k 1 >0,k 2 >0 is a constant in the switching function;

[0061] S203. Using RBF neural network sliding mode control strategy to obtain control rate;

[0062] The sliding mode control rate is:

[0063]

[0064] Using RBF neural network to model the uncertainty term f(x 2 , x 3 ) is estimated, we can get:

[0065] f(x 2 ,x 3 )=W T h(i)+∈;

[0066] Where: W = [w 1 , w 2 , w 3 , w 4 , w 5 ] T ; Radial basis vectors are: h(i) = [h1 ,h 2 ,h 3 ,h 4 ,h 5 ] T ,∈ network approximation error, the radial basis function h(i) is the Gaussian basis function:

[0067]

[0068] Among them, c j represents the node center, b j Represents the node width;

[0069] Using the RBF neural network sliding mode control strategy, the control rate is:

[0070]

[0071] The weight update rate of the neural network is defined as:

[0072] Where τ is the weight update coefficient of the neural network; s is the sliding surface function expression.

[0073] As a second aspect, according to the control method of a high-frequency switch valve-controlled multi-cylinder synchronous jacking control system as described above, the following steps are included:

[0074] K1. Data initialization;

[0075] K2 obtains the target height data; that is, the main control module obtains the target height command of the host computer and transmits it to the corresponding independent control modules;

[0076] K3. Synchronous error judgment: that is, judging whether the displacement feedback values ​​of each group of hydraulic cylinders are within the synchronous error range;

[0077] K4. Calculate and analyze the target displacement and working mode according to the judgment result of step K3; that is, if the synchronization error is not within the allowable range, enter the adjustment mode, that is, adjust the hydraulic cylinder to the same target value according to the output data of the independent control module and the target height data to eliminate the error between the oil cylinder displacements; if the synchronization error is within the allowable range, enter the normal mode, that is, according to the target error, update the next target value, and then calculate the target displacement according to the target error judgment result;

[0078] K5. The hydraulic cylinder executes the telescopic command according to the output data in step K4;

[0079] K6. Complete target displacement, end.

[0080] The beneficial effects of the high-frequency switch valve-controlled multi-cylinder synchronous lifting control system and control method of the present invention are:

[0081] Any hydraulic cylinder in the control system of the present invention is connected through a hydraulic cylinder control circuit composed of a high-frequency switching digital valve group and a double-acting hydraulically controlled one-way valve, and N groups of hydraulic cylinders use the same oil tank, main oil inlet circuit and main oil return circuit, which ensures that the hydraulic cylinder control circuit has a high switching frequency and improves the response rate. At the same time, the entire control system has a low sensitivity to oil, which reduces the impact of oil on system stability, thereby improving the displacement control accuracy of the hydraulic cylinder and solving the problems of poor synchronization accuracy, poor system stability and slow response speed of the multi-cylinder synchronous jacking control system in the prior art.

[0082] In the control method of the multi-cylinder synchronous lifting control system of the present invention, the main control module sets the adjustment mode and the normal mode according to the synchronization error data. The adjustment mode is to adjust the hydraulic cylinder to the same target value according to the output data of the independent control module and the target height data to eliminate the error between the oil cylinder displacements. The normal mode is to determine whether the error feedback value is within the allowable range, and then update the next target value. The combination of these two modes can ensure that the error value between multiple groups of hydraulic cylinders is kept within the minimum range, thereby improving the multi-cylinder synchronous control accuracy. In addition, a sliding mode control algorithm is adopted, which has good anti-interference performance. Even if the system is subject to external disturbances, it can effectively offset these disturbances, thereby improving the stability of the system. At the same time, combined with the RBF neural network, the modeling uncertainty terms in the system can be fitted, further improving the accuracy of multi-cylinder synchronous control. BRIEF DESCRIPTION OF THE DRAWINGS

[0083] The present invention will be further described in detail below in conjunction with the accompanying drawings and specific embodiments.

[0084] Figure 1 It is a schematic diagram of the jacking of the synchronous jacking control system according to an embodiment of the present invention.

[0085] Figure 2 It is a hydraulic principle diagram of the hydraulic system of the present invention.

[0086] Figure 3 It is a schematic diagram of the oil flow direction when the hydraulic cylinders of the present invention are synchronously extended.

[0087] Figure 4 It is a schematic diagram of the oil flow direction when the hydraulic cylinder of the present invention is synchronously retracted.

[0088] Figure 5 It is a connection diagram of the control unit of the present invention.

[0089] Figure 6 It is the electrical control principle diagram of the control unit of the present invention.

[0090] Figure 7 It is a flow chart of the control method steps of the synchronous jacking control system of the present invention.

[0091] Figure 8 The present invention is shown as a control system flow chart.

[0092] Fig. 9 It is a network topology diagram of the control system of the present invention.

[0093] Fig.10 It is a schematic diagram of the target displacement and control signal processing unit of the present invention.

[0094] Fig.11 It is a schematic diagram of the RBF neural network sliding mode control unit of the present invention.

[0095] In the figure: 1, lifting equipment, 2, hydraulic cylinder, 3, control unit, 31, first data acquisition module, 311, main oil inlet sensor, 312, main oil return sensor, 32, second data acquisition module, 321, rodless cavity pressure sensor, 322, rod cavity pressure sensor, 323, displacement sensor, 33, main control module, 331, data receiving unit, 332, target displacement and control signal processing unit, 333, RBF neural network sliding mode control algorithm unit, 3 34. Command output unit, 34. Independent control module, 4. Hydraulic system, 41. Oil tank, 42. Filter, 43. Motor, 44. Overflow valve, 45. First one-way valve, 46. Accumulator, 47. High-frequency switching digital valve group, 471. First high-speed switching valve, 472. Second high-speed switching valve, 473. Third high-speed switching valve, 474. Fourth high-speed switching valve, 48. Double-acting hydraulically controlled one-way valve, 49. Hydraulic pump, 410. Main oil inlet circuit, 420. Main oil return circuit. DETAILED DESCRIPTION

[0096] The present invention will now be described in further detail with reference to the accompanying drawings. These drawings are simplified schematic diagrams, which only illustrate the basic structure of the present invention in a schematic manner, and therefore only show the components related to the present invention.

[0097] like Figure 1-Figure 11 The specific embodiment of a high-frequency switch valve-controlled multi-cylinder synchronous jacking control system of the present invention shown includes a jacking device 1, N groups of hydraulic cylinders 2 arranged below the jacking device 1, and a hydraulic system 4 for controlling the extension and retraction of the N groups of hydraulic cylinders 2 through a control unit 3.

[0098] The hydraulic system 4 includes an oil tank 41, a filter 42, a hydraulic pump, a motor 43, a relief valve 44, a first one-way valve 45, an accumulator 46, and N groups of high-frequency switching digital valve groups 47 and N groups of double-acting hydraulically controlled one-way valves 48 corresponding one to one with the N groups of hydraulic cylinders 2. The motor 43 is connected to the hydraulic pump through a coupling; the filter 42 is placed in the oil tank 41, and the oil outlet of the filter 42 is connected to the oil inlet of the hydraulic pump; the relief valve 44 is connected to the oil outlet of the hydraulic pump, and is also connected to the oil inlet of the first one-way valve 45 on the main oil inlet 410; the oil outlet of the first one-way valve 45 is connected to the oil circuit of the hydraulic accumulator 46 to form the main oil inlet 410, and the output port of the main oil inlet 410 is connected to the oil inlet A of the N groups of high-frequency switching digital valve groups 47; the oil outlet of any group of high-frequency switching digital valve groups 47 is connected to the oil inlet of the corresponding hydraulically controlled one-way valve, and the two oil outlets of a group of double-acting hydraulically controlled one-way valves 48 are respectively connected to the oil inlet and oil outlet of the corresponding hydraulic cylinder 2.

[0099] The hydraulic system 4 in this embodiment is as follows Figure 3 and Figure 4 As shown, there are N groups of hydraulic cylinders 2 connected to the external load to be lifted, which are respectively controlled by a high-frequency switch digital valve group 47 and a double-acting hydraulically controlled one-way valve 48 corresponding to each group. Specifically, the hydraulic pump and the motor 43 are connected through a coupling to form a power element, the oil inlet of the hydraulic pump is connected to the filter 42, the overflow valve 44 is connected to the oil outlet of the hydraulic pump, and is also connected to the oil inlet of the first one-way valve 45 on the main oil inlet circuit 410, and the oil outlet of the first one-way valve 45 is connected to the hydraulic accumulator 46 to form the main oil inlet circuit. 410, the output end of the main oil inlet circuit 410 is fluidly connected to the oil inlets of N groups of high-frequency switching digital valve groups 47. It should be further explained that each group of high-frequency switching digital valve groups 47 is composed of 4 high-speed switching valves connected through independent load ports, and the oil outlet of each high-frequency switching digital valve group 47 is respectively connected to the two groups of oil inlets of the corresponding double-acting hydraulically controlled one-way valve 48, and then the two oil outlets of the double-acting hydraulically controlled one-way valve 48 are respectively connected to the oil inlet and outlet (i.e., rodless oil inlet and rod oil outlet) of the corresponding hydraulic cylinder 2.

[0100] The high-frequency switch digital valve group 47 in this embodiment includes a first high-speed switch valve 471, a second high-speed switch valve 472, a third high-speed switch valve 473 and a fourth high-speed switch valve 474. When the hydraulic cylinder 2 performs the extension action, the oil inlet circuit of the hydraulic cylinder 2 includes the hydraulic oil in the main oil inlet circuit 410 flowing through the first high-speed switch valve 471 and the double-acting hydraulic control check valve 48 in sequence, and then entering the oil from the oil inlet of the hydraulic cylinder 2; the oil return circuit of the hydraulic cylinder 2 includes the hydraulic oil flowing out from the oil outlet of the hydraulic cylinder 2, flowing through the double-acting hydraulic control check valve 48 and the fourth high-speed switch valve 474 in sequence and merging into the main oil return circuit 420. When the hydraulic cylinder 2 performs a contraction action, the oil inlet circuit of the hydraulic cylinder 2 includes the hydraulic oil in the main oil inlet circuit 410 flowing through the third high-speed switching valve 473 and the double-acting hydraulically controlled one-way valve 48 in sequence, and then flowing into the oil outlet of the hydraulic cylinder 2; the oil outlet circuit of the hydraulic cylinder 2 includes the hydraulic oil flowing out from the oil inlet of the hydraulic cylinder 2, flowing through the double-acting hydraulically controlled one-way valve 48 and the second high-speed switching valve 472 in sequence and merging into the main return oil circuit 420.

[0101] like Figure 2 As shown, the motor 43 in this embodiment is connected to the hydraulic pump to supply oil to the hydraulic system 4, the filter 42 is connected to the oil inlet of the hydraulic pump to filter the oil, the overflow valve 44 is located on the main oil inlet line 410 of the hydraulic system 4 to maintain the safety pressure of the hydraulic system 4, the first one-way valve 45 is installed on the main oil inlet line 410 to prevent the reverse flow of oil from damaging the oil pump, and the hydraulic accumulator 46 is connected to the oil outlet of the first one-way valve 45 to reduce the pressure fluctuation of the hydraulic system 4.

[0102] Any hydraulic cylinder 2 in the control system of the present invention has a control circuit of the hydraulic cylinder 2 composed of a high-frequency switching digital valve group 47 and a double-acting hydraulically controlled one-way valve 48, and N groups of hydraulic cylinders 2 use the same oil tank 41, main oil inlet circuit 410 and main oil return circuit 420, which ensures that the control circuit of the hydraulic cylinder 2 has a high switching frequency and improves the response rate. At the same time, the entire control system has a low sensitivity to oil, which reduces the influence of oil on system stability, thereby improving the displacement control accuracy of the hydraulic cylinder 2, and solving the problems of poor synchronization accuracy, poor system stability and slow response speed of the multi-cylinder synchronous jacking control system in the prior art.

[0103] like Figure 3 and Figure 4As shown, this embodiment takes the first group of high-frequency switch digital valve group 47 as an example, which is composed of 4 high-speed digital valves, wherein when the first high-speed switch valve 471 and the fourth high-speed switch valve 474 are energized at the same time, the hydraulic rod of the corresponding hydraulic cylinder 2 will extend, and when the second high-speed switch valve 472 and the third high-speed switch valve 473 are energized at the same time, the hydraulic rod of the corresponding hydraulic cylinder 2 will retract. When the external load is required to be stationary, each group of corresponding 4 high-speed digital valves will lose power, at which time, the corresponding double-acting hydraulic control one-way valve 48 will play a role in sealing the oil inlet and outlet of the hydraulic cylinder 2 to prevent the external load from automatically falling under the action of gravity. Of course, it should be understood that the Nth group of high-frequency switch digital valve group 47 also includes four high-speed digital valves, and its role and implementation principle are the same as those of the first group of high-frequency switch digital valve group 47, which will not be repeated here.

[0104] The control unit 3 in this embodiment includes: a first data acquisition module 31, N groups of second data acquisition modules 32, a main control module 33 and N groups of independent control modules 34, wherein the first data acquisition module 31 is used to collect the oil pressure of the main oil inlet 410 and the oil pressure of the main oil return 420 in real time. The N groups of second data acquisition modules 32 are set in a one-to-one correspondence with the hydraulic cylinder 2, and are used to collect the oil pressure on the oil inlet, the liquid pressure on the oil outlet, and the telescopic displacement of the hydraulic cylinder 2. The main control module 33 is used to receive and process the data information transmitted by the first data acquisition module 31, and set the target displacement and the working mode of the hydraulic cylinder 2. The N groups of independent control modules 34 are in a one-to-one correspondence with the hydraulic cylinder 2, and are used to receive the data information transmitted by the corresponding second data acquisition module 32, and output the data of the high-frequency switch digital valve group 47 and the double-acting hydraulic control check valve 48 corresponding to the hydraulic cylinder 2. The main control module 33 receives and processes the data information output by the first data acquisition module 31 and the data output by the independent control module 34, and determines and calculates the target displacement and working mode corresponding to each group of hydraulic cylinders 2 at the next moment in combination with the target height data, calculates the input signal of each group of digital valves by inputting the target displacement into the RBF neural network sliding mode controller, and sends the control output signal and the working mode signal to each group of independent control modules 34.

[0105] Among them, the first data acquisition module 31 includes a main oil inlet circuit sensor 311 and a main oil return circuit sensor 312. The main oil inlet circuit sensor 311 is arranged on the main oil inlet circuit 410, and is used to detect the liquid oil pressure on the main oil inlet circuit 410 in real time; the main oil return circuit sensor 312 is arranged on the main oil return circuit 420, and is used to detect the liquid oil pressure on the main oil return circuit 420 in real time; the main oil inlet circuit sensor 311 and the main oil return circuit sensor 312 are both communicatively connected to the main control module 33.

[0106] The second data acquisition module 32 includes a rodless cavity pressure sensor 321, a rod cavity pressure sensor 322, and a displacement sensor 323. The rodless cavity pressure sensor 321 is arranged on the oil inlet oil circuit of the hydraulic cylinder 2, and is used to detect the oil pressure on the oil inlet oil circuit of the hydraulic cylinder 2 in real time; the rod cavity pressure sensor 322 is arranged on the oil outlet oil circuit of the hydraulic cylinder 2, and is used to detect the oil pressure on the oil outlet oil circuit of the hydraulic cylinder 2 in real time; the displacement sensor 323 is arranged on the hydraulic cylinder 2, and is used to detect the telescopic displacement of the hydraulic cylinder 2 in real time; the rodless cavity pressure sensor 321, the rod cavity pressure sensor 322, and the displacement sensor 323 are all connected to the corresponding independent control module 34 in communication; the independent control module 34 is connected to the main control module 33 in communication.

[0107] The main control module 33 is respectively connected with the independent control modules 34 of the 1st group to the Nth group through communication. The data of the main circuit pressure sensor 312 is read by the main control module 33. The data of each group of displacement sensors 323 are respectively read by the corresponding independent control modules 34 and the acquired displacement sensor 323 values ​​are transmitted to the main control module 33 in real time. The values ​​of the rodless cavity pressure sensor 321 and the rod cavity pressure sensor 322 corresponding to each hydraulic cylinder 2 are read by the corresponding independent control modules 34 of each group, and the corresponding values ​​are monitored in real time while judging whether the corresponding hydraulic cylinder 2 is leaking oil. When it is judged that oil leakage may occur, an alarm signal is sent to the main control module 33 to remind the staff to deal with it in time.

[0108] As a preferred method, the main control module 33 in this embodiment determines and calculates the target displacement and working mode corresponding to each group of hydraulic cylinders 2 at the next moment, including the following steps:

[0109] Step 1: construct a mathematical model of the synchronous lifting hydraulic system 4;

[0110] Step 2: Establish a sliding mode control algorithm using the mathematical model constructed in step 1;

[0111] Step 3: Calculate the target displacement and working mode corresponding to each hydraulic cylinder 2 according to the sliding mode control algorithm constructed in step 2; the working mode includes adjustment mode and normal mode.

[0112] The mathematical model of the synchronous lifting hydraulic system 4 in step 1 includes the following steps:

[0113] S101. Establish the flow equations of the single hydraulic cylinder 2 when extending and retracting through the corresponding high-frequency switching digital valve group 47:

[0114]

[0115] Among them, A 1 A is the area of ​​the rod cavity; 2is the area of ​​the rodless cavity; Q 1 is the oil inlet flow rate; Q 2 is the oil outlet flow rate; C dv is the flow coefficient of the digital valve; A dv is the flow area of ​​the digital valve; P s is the oil supply pressure; P 0 is the return oil pressure; u is the controller signal output; P 1 is the rodless cavity pressure; P 2 is the rod cavity pressure; x dv is the equivalent valve core displacement of the digital valve; ρ is the hydraulic oil density;

[0116] S102. Construct the flow continuity equation of the hydraulic system 4:

[0117]

[0118] Among them, x p C is the displacement of the piston rod of hydraulic cylinder 2; ip is the internal leakage coefficient of hydraulic cylinder 2; C ec is the external leakage coefficient of hydraulic cylinder 2;

[0119] The load pressure expression for hydraulic cylinder 2 is: P L =P 1 -ηP 2 , put it into formula 1 to get the pressure P of hydraulic cylinder 2 1 , P 2 The relational expression is:

[0120]

[0121] In the formula, R L Represents load pressure.

[0122] The output load force of the hydraulic cylinder (2) can be expressed as: P L A e =P 1 A 1 -ηP 2 A 2 ,A e Expressed as the equivalent area corresponding to the load pressure, the equivalent area can be obtained by combining this formula with (3):

[0123]

[0124] Ignoring the influence of the length and diameter of the oil pipeline on the modeling, and ignoring the pressure loss of the fluid along the pipe, the internal and external leakage are all laminar flow, and the flow continuity equation expression of the hydraulic system 4 can be obtained as follows:

[0125]

[0126] Where: x p is the output displacement of hydraulic cylinder 2; C ic is the internal leakage coefficient of hydraulic cylinder 2; C ec for

[0127] External leakage coefficient of hydraulic cylinder 2; V 1 V is the rodless chamber volume of hydraulic cylinder 2; 2 is the rod chamber volume of hydraulic cylinder 2; β is the bulk elastic modulus.

[0128] In the hydraulic system 4, it is assumed that the initial volumes of the rodless chamber and the rod chamber of the hydraulic cylinder 2 are: V 10 、V 20 , then the volume change formula of the two chambers of hydraulic cylinder 2 is: V 1 =V 10 +x p A 1 , V 2 =V 20 -x p A 2 , the total volume of hydraulic cylinder 2 is expressed as V t ; The relationship between the total volume and the initial volume is as follows:

[0129] V t =V 10 +x p A 1 +V 20 +x p A 2 (7);

[0130] So the flow continuity equation of hydraulic cylinder 2 can be expressed as:

[0131]

[0132] In the above formula, x p A 1 <<V10,x p A 2 <<V20 So the fifth term in the formula can be ignored, so Q L The expression is:

[0133]

[0134] Where: A P is the piston equivalent area,

[0135] S103. The balance equation of the output force of the hydraulic cylinder 2 and the external load is described as follows:

[0136]

[0137] Therefore, the equilibrium equation is expressed as:

[0138]

[0139] In the formula, m represents the equivalent mass of the hydraulic cylinder; Represents the acceleration of the hydraulic cylinder; Represents the moving speed of the hydraulic cylinder; x p Represents the displacement of the hydraulic cylinder; B P represents the damping coefficient of the hydraulic cylinder piston; K represents the spring stiffness of the hydraulic cylinder; F L Represents the external load of the hydraulic cylinder; P s Represents the hydraulic system oil supply pressure.

[0140] Assume the state variable of the system: x 1 =x p , The state balance equation of hydraulic cylinder 2 is established by using the above formulas (1) to (10):

[0141]

[0142] In the formula, f(x 2 , x 3 )=a 1 x 2 +a 2 x 3 ; The system disturbance is defined as: The expression of G is defined as follows:

[0143]

[0144] Among them, C dv is the flow coefficient of the digital valve; A dv is the flow area of ​​the digital valve; u is the controller signal output; P 0 is the return oil pressure of the hydraulic system; P 1 is the rodless cavity pressure; P 2 is the rod cavity pressure; P S is the oil supply pressure of the hydraulic system; x dv is the equivalent valve core displacement of the digital valve; ρ is the hydraulic oil density.

[0145] Establishing the sliding mode control algorithm includes the following processes:

[0146] S201. Define the system error calculation:

[0147] e=x d -x p (13);

[0148] In the formula, x d is the target displacement of the hydraulic cylinder; xp is the actual displacement of the hydraulic cylinder.

[0149] S202. Construct sliding surface design formula:

[0150]

[0151] In the formula, μ 1 is the coefficient of the sliding surface function 1, μ 2 is the sliding surface function coefficient 2, e is the displacement tracking error, is the first-order derivative of the displacement tracking error, is the second-order derivative of the displacement tracking error.

[0152] Taking the first-order derivative of s, we get:

[0153]

[0154] make The equivalent control rate of sliding mode control can be obtained as follows:

[0155]

[0156] The switching control rate selects the exponential approach rate:

[0157] u zs =-k 1 sgn(s)-k 2 s (16);

[0158] In the formula, k 1 >0,k 2 >0 is a constant in the switching function.

[0159] S203. Using RBF neural network sliding mode control strategy to obtain control rate;

[0160] The sliding mode control rate is:

[0161]

[0162] Using RBF neural network to model the uncertainty term f(x 2 , x 3 ) is estimated, we can get:

[0163] f(x 2 ,x 3 )=W T h(i)+∈ (18);

[0164] Where: W = [w 1 , w 2 , w 3 , w 4 , w5 ] T ; Radial basis vectors are: h(i) = [h 1 ,h 2 ,h 3 ,h 4 ,h 5 ] T ,∈ network approximation error, the radial basis function h(i) is the Gaussian basis function:

[0165]

[0166] Among them, c j represents the node center, b j Represents the node width;

[0167] Using the RBF neural network sliding mode control strategy, the control rate is:

[0168]

[0169] The weight update rate of the neural network is defined as:

[0170]

[0171] Where τ is the weight update coefficient of the neural network; s is the sliding surface function expression.

[0172] See also Figure 7 The control method based on the high-frequency switch valve-controlled multi-cylinder synchronous lifting control system includes the following steps:

[0173] K1. Data initialization;

[0174] K2 obtains the target height data; that is, the main control module 33 obtains the host computer target height command and transmits it to the corresponding independent control modules 34;

[0175] K3. Synchronous error judgment; that is, judging whether the displacement feedback value of each group of hydraulic cylinders 2 is within the synchronous error range;

[0176] K4. Calculate and analyze the target displacement and working mode according to the judgment result of step K3; that is, if the synchronization error is not within the allowable range, enter the adjustment mode, that is, adjust the hydraulic cylinder 2 to the same target value according to the output data of the independent control module 34 and the target height data to eliminate the error between the oil cylinder displacements; if the synchronization error is within the allowable range, enter the normal mode, that is, according to the target error, update the next target value, and then calculate the target displacement according to the target error judgment result;

[0177] K5 hydraulic cylinder 2 according to the output data in step K4, execute the telescopic command;

[0178] K6. Complete target displacement, end.

[0179] like Figure 8 As shown, the specific process is as follows: First, the synchronous jacking control system needs to initialize data, and then obtain the target height command in the host computer. The displacement feedback value collected by the displacement sensor 323 in each group of hydraulic cylinders 2 is judged whether it is within the set synchronization error range. If it is within the error range, it will enter the normal mode selection judgment. If it is not within the synchronization error range, it will enter the adjustment mode. When entering the normal mode selection, if the displacement values ​​of the current N groups of hydraulic cylinders 2 are all within the specified error range, it indicates that the target displacement has been reached and the displacement tracking ends. When entering the normal mode, the displacement target value at the next moment will be updated by "D_1+STEP_D", that is, the current displacement value plus the target displacement step value, and then the updated target displacement is input into the RBF neural network sliding mode control algorithm unit 333, and the corresponding high-frequency switch digital valve group 47 control signal u is calculated. Each group of independent control modules 34 receives the control signal of the main control module 33 and then controls the switch action of each high-speed switch valve. When the current target displacement is reached, the current round of displacement tracking ends, and then the next round of target displacement tracking continues until the target height is reached. When entering the adjustment mode, first calculate the average displacement of all hydraulic cylinders 2, then use the average as the target value for adjustment, and input the target value into the RBF neural network sliding mode control unit 3 to calculate the control signal u of the high-frequency switching digital valve group 47, and then each group of independent control modules 34 receives the control signal u of the main control module 33 to control the switching action of each high-speed switching valve, and finally determine whether it is within the allowable range of synchronization error, and then continue to the next process.

[0180] The main control module 33 in this embodiment includes a data receiving unit 331, a target displacement and control signal processing unit 332, an RBF neural network sliding mode control algorithm unit 333, and an instruction output unit 334. The control method of the multi-cylinder synchronous jacking control system in this embodiment adopts a master-slave control scheme, and the main control module 33 is mainly responsible for the implementation of the control algorithm; at the same time, it receives the corresponding hydraulic cylinder 2 displacement data uploaded by N groups of independent control modules 34, and sends the data to the target displacement and control signal processing unit 332, and then the unit will combine the target height data and output the target displacement value and control command signal of each group of hydraulic cylinder 2 at the next moment after calculation and judgment, and transmit it to the corresponding independent control module 34 through the instruction output unit 334.

[0181] In this embodiment, the principle of the target displacement and control signal processing unit 332 is as follows: Fig.10 As shown, the target displacement and control signal processing unit 332 receives the displacement values ​​of each group of hydraulic cylinders 2 and calculates the average value D AVE, then calculate the absolute value of the difference between the target height and the average displacement of N groups of hydraulic cylinders 2: |D goal -D AVE |, and calculate the average value D AVE and the absolute value of the difference from the actual displacement value D _1 of each group of hydraulic cylinders 2: |D AVE -D _1 |. In the target displacement and control signal processing unit 332, the output state of "STATE_1" is |D goal -D AVE |<∈ and the result of taking the "AND" of |D AVE -D _1 |<E comparison values, where ∈ is defined as the target error tolerance value, and E is defined as the allowable error of the difference between the actual displacement of each group of hydraulic cylinders 2 and the average displacement of all hydraulic cylinders 2. In the target displacement and control signal processing unit 332, the state of "STATE_12" is determined by the result of taking the "AND" of the output of "STATE_1" being "FALSE" and |D goal -D AVE |>∈ comparison values. When the output of "STATE_1" is "TRUE", the displacement value of the corresponding group of hydraulic cylinders 2 at the next moment is the current moment displacement value plus the moving step value "STEP_D". At the same time, the control signal output is in the normal normal mode. When the state of "STATE_12" is "TRUE", it means that the displacement of this group of hydraulic cylinders 2 exceeds the error tolerance value. At this time, the control signal output is in the displacement adjustment mode, and the target value of this group of hydraulic cylinders 2 is updated to the displacement average value D AVE ; when the state of "STATE_12" is "FALSE", it represents the stop mode. At this time, the target displacement stops updating, and the control signal output is in the stop mode.

[0182] In the normal mode, each independent control module 34 will judge the actions of each high-speed switching valve according to the signal u output by the main control module 33. Taking the first group of high-frequency switching digital valve groups 47 as an example: when u>0, the corresponding first high-speed switching valve 471 and the fourth high-speed switching valve 474 are simultaneously powered on. When u<0, the corresponding second high-speed switching valve 472 and the third high-speed switching valve 473 are simultaneously powered on. When u = 0, all four high-speed switching valves are de-energized. In the adjustment mode, each independent control module 34 adjusts the displacement of this group of hydraulic cylinders 2 to the average displacement according to the signal output by the main control module 33. In the stop mode, all high-speed switching valves are de-energized, and the position of the corresponding hydraulic cylinder 2 is locked.

[0183] The difference between the target displacement value output by the main control module 33 and the current actual displacement value of the hydraulic cylinder 2 is calculated, and the obtained result, which is the target displacement increment, will be used as the control input of the RBF neural network sliding mode control algorithm unit 333, as Fig.11As shown in the formula, the input of the control algorithm is the target displacement increment, and the output is the actual displacement increment of the hydraulic cylinder 2. In the RBF neural network sliding mode control algorithm unit 333, the actual displacement of the hydraulic cylinder 2 collected by the main control module 33 is used to calculate the incremental displacement within the sampling time period Δt, and then the first-order and second-order derivatives are calculated, and the first-order and second-order derivatives of the target incremental value are respectively subtracted to obtain and The error e is the difference between the target displacement increment and the actual displacement increment. The control output signal u can be calculated by inputting it into the RBF neural network sliding mode control algorithm unit 333 respectively, and then the output signal is transmitted to each group of independent control modules 34.

[0184] Each group of independent control modules 34 will receive the mode instruction and the output signal of the main control module 33 from the main control module 33 in real time, and then convert the output signal of the main control module 33 into the gain / loss electrical signal of the corresponding high-speed switch valve according to the mode instruction.

[0185] In the control method of the multi-cylinder synchronous lifting control system of the present invention, the main control module 33 sets the adjustment mode and the normal mode according to the synchronization error data. The adjustment mode is to adjust the hydraulic cylinder 2 to the same target value according to the output data of the independent control module 34 and the target height data to eliminate the error between the oil cylinder displacements. The normal mode is to determine whether the error feedback value is within the allowable range, and then update the next target value. The combination of these two modes can ensure that the error value between multiple groups of hydraulic cylinders 2 is kept within the minimum range, thereby improving the multi-cylinder synchronous control accuracy. In addition, a sliding mode control algorithm is adopted, which has good anti-interference performance. Even if the system is subject to external disturbances, it can effectively offset these disturbances, thereby improving the stability of the system. At the same time, combined with the RBF neural network, the uncertainty terms in the modeling system can be fitted, further improving the accuracy of multi-cylinder synchronous control.

[0186] It should be understood that the specific embodiments described above are only used to explain the present invention, and are not used to limit the present invention. Obvious changes or modifications derived from the spirit of the present invention are still within the protection scope of the present invention.

Claims

1. A high-frequency switch valve-controlled multi-cylinder synchronous lifting control system, characterized in that: It comprises a lifting device (1), N groups of hydraulic cylinders (2) arranged below the lifting device (1), and a hydraulic system (4) for controlling the extension and retraction of the N groups of hydraulic cylinders (2) through a control unit (3); The hydraulic system (4) comprises an oil tank (41), a filter (42), a hydraulic pump, a motor (43), a relief valve (44), a first check valve (45), an accumulator (46), and N groups of high-frequency switch digital valve groups (47) and N groups of double-acting hydraulically controlled check valves (48) corresponding one-to-one to the N groups of hydraulic cylinders (2); The motor (43) is connected to the hydraulic pump through a coupling; the filter (42) is placed in the oil tank (41), and the oil outlet of the filter (42) is connected to the oil inlet of the hydraulic pump; the overflow valve (44) is connected to the oil outlet of the hydraulic pump and is also connected to the oil inlet of the first one-way valve (45) on the main oil inlet (410); the oil outlet of the first one-way valve (45) is connected to the oil circuit of the hydraulic accumulator (46) to form the main oil inlet (410), and the output port of the main oil inlet (410) is connected to the oil inlet A of the N groups of the high-frequency switch digital valve groups (47); the oil outlet of any group of the high-frequency switch digital valve groups (47) is connected to the oil inlet of the corresponding hydraulically controlled one-way valve, and the two oil outlets of a group of the double-acting hydraulically controlled one-way valve (48) are respectively connected to the oil inlet and oil outlet of the corresponding hydraulic cylinder (2).

2. A high-frequency switch valve-controlled multi-cylinder synchronous lifting control system according to claim 1, characterized in that: The high-frequency switching digital valve group (47) comprises a first high-speed switching valve (471), a second high-speed switching valve (472), a third high-speed switching valve (473) and a fourth high-speed switching valve (474); When the hydraulic cylinder (2) performs an extension action, the oil inlet circuit of the hydraulic cylinder (2) includes the hydraulic oil in the main oil inlet circuit (410) flowing through the first high-speed switch valve (471) and the double-acting hydraulically controlled one-way valve (48) in sequence, and then entering the oil from the oil inlet of the hydraulic cylinder (2); the oil return circuit of the hydraulic cylinder (2) includes the hydraulic oil flowing out from the oil outlet of the hydraulic cylinder (2), flowing through the double-acting hydraulically controlled one-way valve (48) and the fourth high-speed switch valve (474) in sequence, and entering the main oil return circuit (420); When the hydraulic cylinder (2) performs a contraction action, the oil inlet circuit of the hydraulic cylinder (2) includes the hydraulic oil in the main oil inlet circuit (410) flowing through the third high-speed switch valve (473) and the double-acting hydraulically controlled one-way valve (48) in sequence, and then flowing into the oil outlet of the hydraulic cylinder (2); the oil outlet circuit of the hydraulic cylinder (2) includes the hydraulic oil flowing out of the oil inlet of the hydraulic cylinder (2), flowing through the double-acting hydraulically controlled one-way valve (48) and the second high-speed switch valve (472) in sequence, and merging into the main return oil circuit (420).

3. A high-frequency switch valve-controlled multi-cylinder synchronous lifting control system according to claim 1, characterized in that: The control unit (3) comprises: The first data acquisition module (31) is used to collect the oil pressure of the main oil inlet circuit (410), the oil pressure of the main oil return circuit (420), N groups of second data acquisition modules (32), arranged in one-to-one correspondence with the hydraulic cylinders (2), and used to collect the oil pressure on the oil inlet path, the oil pressure on the oil outlet path, and the telescopic displacement of the hydraulic cylinders (2); A main control module (33) is used to receive and process the data information transmitted by the first data acquisition module (31), and to set the target displacement and the working mode of the hydraulic cylinder (2); N groups of independent control modules (34), corresponding one to one with the hydraulic cylinder (2), for receiving data information transmitted by the corresponding second data acquisition module (32), and outputting data of the high-frequency switch digital valve group (47) and the double-acting hydraulic control check valve (48) corresponding to the hydraulic cylinder (2); The main control module (33) receives and processes the data information output by the first data acquisition module (31) and the data output by the independent control module (34), determines and calculates the target displacement and working mode corresponding to each group of hydraulic cylinders (2) at the next moment in combination with the target height data, calculates the input signal of each group of digital valves by inputting the target displacement into the RBF neural network sliding mode controller, and sends the control output signal and the working mode signal to each group of independent control modules (34).

4. A high-frequency switch valve-controlled multi-cylinder synchronous lifting control system according to claim 3, characterized in that: The first data acquisition module (31) comprises: A main oil inlet sensor (311), arranged on the main oil inlet (410), for detecting the oil pressure on the main oil inlet (410) in real time; A main oil return line sensor (312), arranged on the main oil return line (420), for detecting the oil pressure on the main oil return line (420) in real time; The main oil inlet sensor (311) and the main oil return sensor (312) are both communicatively connected to the main control module (33).

5. A high-frequency switch valve-controlled multi-cylinder synchronous lifting control system according to claim 3, characterized in that: The second data acquisition module (32) comprises: A rodless chamber pressure sensor (321) is arranged on the oil inlet line of the hydraulic cylinder (2) and is used to detect the oil pressure on the oil inlet line of the hydraulic cylinder (2) in real time; A rod chamber pressure sensor (322) is arranged on the oil outlet line of the hydraulic cylinder (2) and is used to detect the oil pressure on the oil outlet line of the hydraulic cylinder (2) in real time; A displacement sensor (323) is arranged on the hydraulic cylinder (2) and is used to detect the telescopic displacement of the hydraulic cylinder (2) in real time; The rodless cavity pressure sensor (321), the rod cavity pressure sensor (322) and the displacement sensor (323) are all communicatively connected to the corresponding independent control module (34); the independent control module (34) is communicatively connected to the main control module (33).

6. A high-frequency switch valve-controlled multi-cylinder synchronous lifting control system according to claim 3, characterized in that: The main control module (33) determines and calculates the target displacement and working mode corresponding to each group of hydraulic cylinders (2) at the next moment, including the following steps: Step 1: construct a mathematical model of the synchronous lifting hydraulic system (4); Step 2: Establish a sliding mode control algorithm using the mathematical model constructed in step 1; Step three: Calculate the target displacement and working mode corresponding to each hydraulic cylinder (2) according to the sliding mode control algorithm constructed in step two; the working mode includes an adjustment mode and a normal mode.

7. A high-frequency switch valve-controlled multi-cylinder synchronous lifting control system according to claim 6, characterized in that: The step 1 of constructing the mathematical model of the synchronous lifting hydraulic system (4) comprises the following steps: S101. Establish the flow equations of the single hydraulic cylinder (2) when extending and retracting through the corresponding high-frequency switching digital valve group (47): Among them, A1 is the area of ​​the rod cavity; A2 is the area of ​​the rodless cavity; Q1 is the oil inlet flow rate; Q2 is the oil outlet flow rate; C dv is the flow coefficient of the digital valve; A dv is the flow area of ​​the digital valve; P s is the oil supply pressure; P0 is the oil return pressure; u is the controller signal output; P1 is the rodless chamber pressure; P2 is the rod chamber pressure; x dv is the equivalent valve core displacement of the digital valve; ρ is the hydraulic oil density; S102. Construct the flow continuity equation of the hydraulic system (4): Among them, x p C is the displacement of the piston rod of the hydraulic cylinder (2); ip is the internal leakage coefficient of the hydraulic cylinder (2); C ec is the external leakage coefficient of the hydraulic cylinder (2), A1 is the area of ​​the hydraulic cylinder with rod cavity, A2 is the area of ​​the hydraulic cylinder without rod cavity, P1 is the pressure of the hydraulic cylinder without rod cavity, P2 is the pressure of the hydraulic cylinder with rod cavity, V1 is the volume of the hydraulic cylinder without rod cavity, V2 is the volume of the hydraulic cylinder with rod cavity; β is the bulk elastic modulus; The relationship between the pressures P1 and P2 of the hydraulic cylinder (2) is expressed as: Where P L represents the load pressure, η represents the ratio of the effective area of ​​the hydraulic cylinder with rod cavity and the rodless cavity; P s Represents the hydraulic system oil supply pressure, P L Represents the load pressure drop of the hydraulic system; S103. The balance equation of the output force of the hydraulic cylinder (2) and the external load is described as follows: In the formula, m represents the equivalent mass of the hydraulic cylinder; Represents the acceleration of the hydraulic cylinder; Represents the moving speed of the hydraulic cylinder; x p Represents the displacement of the hydraulic cylinder; B P represents the damping coefficient of the hydraulic cylinder piston; K represents the spring stiffness of the hydraulic cylinder; F L Represents the external load of the hydraulic cylinder; P s Represents the oil supply pressure of the hydraulic system; Assume the state variable of the system: x1 = x p , The state balance equation of the hydraulic cylinder (2) is established using the above formula: Where, f(x2, x3) = a1x2 + a2x3; The system disturbance is defined as: G is a simplified expression whose specific definition is: Among them, C dv is the flow coefficient of the digital valve; A dv is the flow area of ​​the digital valve; u is the controller signal output; P0 is the return oil pressure of the hydraulic system; P1 is the rodless chamber pressure; P2 is the rod chamber pressure; P S Supply oil pressure to the hydraulic system; x dv is the equivalent valve core displacement of the digital valve; ρ is the hydraulic oil density.

8. The high-frequency switch valve-controlled multi-cylinder synchronous lifting control system according to claim 5 is characterized in that: The establishment of the sliding mode control algorithm includes the following processes: S201. Define the system error calculation: e=x d -x p ; In the formula, x d is the target displacement of the hydraulic cylinder; x p is the actual displacement of the hydraulic cylinder. S202. Construct sliding surface design formula: Where, μ1 is the sliding surface function coefficient 1, μ2 is the sliding surface function coefficient 2, e is the displacement tracking error, is the first-order derivative of the displacement tracking error, is the second-order derivative of displacement tracking error; Taking the first-order derivative of s, we get: make The equivalent control rate of sliding mode control can be obtained as follows: The switching control rate selects the exponential approach rate: u zs =-k1sgn(s)-k2s; Where, k1>0, k2>0 are constants in the switching function; S203. Using RBF neural network sliding mode control strategy to obtain control rate; The sliding mode control rate is: By using RBF neural network to estimate the modeling uncertainty term f(x2, x3), we can get: f(x2,x3)=W T h(i)+∈; Where: W = [w1, w2, w3, w4, w5] T ; Radial basis vectors are: h(i) = [h1, h2, h3, h4, h5] T ,∈ network approximation error, the radial basis function h(i) is the Gaussian basis function: Among them, c j represents the node center, b j Represents the node width; Using the RBF neural network sliding mode control strategy, the control rate is: The weight update rate of the neural network is defined as: Where τ is the weight update coefficient of the neural network; s is the sliding surface function expression.

9. A control method for a high-frequency switch valve-controlled multi-cylinder synchronous lifting control system according to any one of claims 1 to 8, characterized in that: The following steps are involved: K1. Data initialization; K2 obtains the target height data; that is, the main control module (33) obtains the host computer target height command and transmits it to the corresponding independent control modules (34); K3. Synchronous error judgment; that is, judging whether the displacement feedback value of each group of hydraulic cylinders (2) is within the synchronous error range; K4. Calculate and analyze the target displacement and working mode according to the judgment result of step K3; that is, if the synchronization error is not within the allowable range, enter the adjustment mode, that is, adjust the hydraulic cylinder (2) to the same target value according to the output data of the independent control module (34) and the target height data to eliminate the error between the oil cylinder displacements; if the synchronization error is within the allowable range, enter the normal mode, that is, update the next target value according to the target error, and then calculate the target displacement according to the target error judgment result; K5 hydraulic cylinder (2) according to the output data in step K4, execute the telescopic command; K6. Complete target displacement, end.

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