Parameter calibration method of hydraulic cylinder system

Abstract

The invention discloses a parameter calibration method of a hydraulic cylinder system, which comprises the following steps: S1, building a hydraulic cylinder system experiment platform according to the working principle of the hydraulic cylinder system; s2, establishing a mathematical model for the hydraulic cylinder system, and solving a transfer function of the hydraulic cylinder system; s3, converting the transfer function of the hydraulic cylinder system into a discrete equation by adopting a bilinear transformation formula according to the basic principle of the least square method; and S4, a parameter matrix of the hydraulic cylinder system is solved, and parameter calibration work of the hydraulic cylinder system is completed. By adjusting the transfer function of the hydraulic cylinder system, the performance of the system can be improved, the dynamic response characteristic of the system can be optimized, the stability of the system can be improved, the response speed can be increased, and overshoot can be reduced; the frequency characteristics of the system can be visually understood through the transfer function, an engineer is helped to quickly identify and adjust key parameters, and the design process of the control system is simplified.

Description

Technical Field

[0001] The invention relates to the fields of hydraulic equipment technology and mechanical control, and in particular to a parameter calibration method for a hydraulic cylinder system. Background Art

[0002] The hydraulic cylinder is a key component in the hydraulic system for converting hydraulic energy into mechanical energy. The accurate calibration of its parameters is crucial to the working efficiency and stability of the entire hydraulic system. In order to ensure the performance and stability of the hydraulic cylinder under different working conditions, it is often necessary to calibrate its parameters.

[0003] Technically, the behavior of a hydraulic cylinder may not be consistent with theoretical expectations due to manufacturing tolerances, material properties, and changes in the use environment. Therefore, it is necessary to calibrate the parameters to meet the design requirements. The existing technology generally calculates each parameter by direct measurement or test, which is a huge workload and inconvenient for later modulation and management. By adjusting the transfer function of the hydraulic cylinder system to perform parameter calibration, its dynamic performance and steady-state performance can be optimized. The parameter indicators in the transfer function can usually affect the gain and response speed of the system, resulting in system stability or response characteristics. During the use of the hydraulic cylinder, the specific values ​​of the parameters in the transfer function of the hydraulic cylinder system will affect the performance and control accuracy of the system. Therefore, parameter calibration by adjusting the transfer function of the hydraulic cylinder system is a necessary step to ensure the normal operation of the hydraulic cylinder and an important technology for achieving efficient and stable control of the hydraulic system.

[0004] By adjusting the transfer function of the hydraulic cylinder system to calibrate the parameters, not only its performance and reliability are improved, but also a basis for the optimization and intelligent development of the hydraulic system is provided. With the development of scientific research and technology, the research on hydraulic cylinders will continue to deepen through scientific calibration methods. The performance of hydraulic cylinders can be optimized according to actual application requirements to meet the increasingly high precision and efficiency requirements of modern industry for hydraulic systems.

[0005] In view of the problems that the hydraulic cylinder system is difficult to achieve precise control due to factors such as poor flexibility and adaptability of existing hydraulic cylinder parameter calibration methods, difficulty in optimizing response characteristics, many nonlinear factors, low cost-effectiveness, and poor overall system stability, there is an urgent need to provide a new parameter calibration method for hydraulic cylinder systems to solve the above problems. Summary of the invention

[0006] The technical problem to be solved by the present invention is to provide a parameter calibration method for a hydraulic cylinder system, which can improve the performance of the hydraulic cylinder system, optimize the dynamic response characteristics of the system, improve the stability of the system, accelerate the response speed and reduce the overshoot.

[0007] In order to solve the above technical problems, a technical solution adopted by the present invention is: to provide a parameter calibration method of a hydraulic cylinder system, comprising the following steps:

[0008] S1: Build a hydraulic cylinder system experimental platform according to the working principle of the hydraulic cylinder system;

[0009] S2: Establishing a mathematical model of the hydraulic cylinder system and obtaining a transfer function of the hydraulic cylinder system;

[0010] S3: According to the basic principle of least square method and using bilinear transformation formula, the transfer function of hydraulic cylinder system is transformed into discrete equation;

[0011] S4: Calculate the parameter matrix of the hydraulic cylinder system and complete the parameter calibration of the hydraulic cylinder system.

[0012] In a preferred embodiment of the present invention, in step S1, the constructed hydraulic cylinder system experimental platform includes a system host computer, a hydraulic pump station, and a hydraulic cylinder. The system host computer sends a control signal to the hydraulic pump station, the hydraulic pump station sends a drive signal to the hydraulic cylinder, the hydraulic pump station drives the hydraulic cylinder to move, and the displacement sensor on the hydraulic cylinder feeds back the displacement signal to the system host computer. The system host computer uses MATLAB software to perform parameter calibration on the transfer function of the hydraulic cylinder system.

[0013] In a preferred embodiment of the present invention, in step S2, the mathematical model and transfer function of the hydraulic cylinder system are divided into two cases with and without external load, and the establishment basis is respectively:

[0014] (1) When the hydraulic cylinder system is subject to external load:

[0015] Flow equation Q of plunger pump p =D p n p -C tp p l ; Flow continuity equation of hydraulic cylinder The force balance equation of the hydraulic cylinder during normal operation

[0016] (2) When there is no external load on the hydraulic cylinder system:

[0017] Flow equation Q of plunger pump p =D p n p -C tp p l ; Flow continuity equation of hydraulic cylinder The force balance equation of the hydraulic cylinder during normal operation

[0018] In the above formula, Q p D is the output flow of the plunger pump; p is the displacement of the plunger pump; n p Input speed of the system; C tp is the leakage coefficient of the plunger pump; p l is the system pressure; C tc is the hydraulic cylinder leakage coefficient; A p V is the effective area of ​​the hydraulic cylinder; t is the total volume of the hydraulic cylinder; β e is the comprehensive elastic modulus of the hydraulic cylinder; x p is the displacement of the hydraulic cylinder piston; m t is the total mass of the hydraulic cylinder piston and the load; B p is the overall viscous damping coefficient; F L is the external load force acting on the hydraulic cylinder piston;

[0019] The flow equation of the plunger pump, the flow continuity equation of the hydraulic cylinder and the force balance equation of the hydraulic cylinder in normal operation are transformed into a pull-type transformation:

[0020] (1) When the hydraulic cylinder system is subject to external load:

[0021]

[0022] (2) When there is no external load on the hydraulic cylinder system:

[0023]

[0024] By calculating and arranging the above two combined equations, we can obtain the transfer function of the hydraulic cylinder system:

[0025] In a preferred embodiment of the present invention, the specific steps of step S3 include:

[0026] (1) When there is no external load on the hydraulic cylinder system, there is no external interference in the hydraulic cylinder system. At this time, the system only has a transfer function between the displacement of the hydraulic cylinder piston rod and the input speed of the system. The transfer function of the proposed hydraulic cylinder system is:

[0027]

[0028] in A p D is the effective area of ​​the hydraulic cylinder. p is the displacement of the plunger pump; m t is the total mass of the hydraulic cylinder piston and the load, V t is the total volume of the hydraulic cylinder, β eis the comprehensive elastic modulus of the hydraulic cylinder; B p is the overall viscous damping coefficient, C is the total leakage coefficient;

[0029] According to the basic principle of least square method, the transfer function of the hydraulic cylinder system is identified. First, the transfer function of the system is transformed into a discrete equation using the bilinear transformation formula. Let:

[0030]

[0031] In the above formula, T is the sampling time; Substituting this back into the transfer function we get:

[0032] In the above formula, T is the sampling time; Substituting this back into the transfer function we get:

[0033]

[0034] Suppose: B0=B3=K; B1=B2=3K; A0=A+B+C; A1=-3A-B+C; A2=3A-BC; A3=-A+BC; then:

[0035]

[0036] Therefore, there are:

[0037]

[0038] In the above formula, x p (k) represents the piston rod displacement data collected by the system at discrete time point k, x p (k-1) is the piston rod displacement data collected at time point k-1, x p (k-2) is the piston rod displacement data collected at time point k-2, x p (k-3) is the piston rod displacement data collected at time point k-3; n p (k) represents the system input speed data at discrete time point k, n p (k-1) is the input speed data of the system at time point k-1, n p (k-2) is the input speed data of the system at time point k-2, n p (k-3) is the data of the system input speed at time point k-3;

[0039] (2) When the hydraulic cylinder system is subject to external load, there is external interference in the hydraulic cylinder system. The system includes the transfer function between the displacement of the hydraulic cylinder piston rod and the motor input speed, and the transfer function between the displacement of the hydraulic cylinder piston rod and the external load of the system. At this time, the transfer function between the displacement of the hydraulic cylinder piston rod and the input speed of the system is proposed as follows:

[0040]

[0041] in A p D is the effective area of ​​the hydraulic cylinder. p is the displacement of the plunger pump; m t is the total mass of the hydraulic cylinder piston and the load, V t is the total volume of the hydraulic cylinder, β e is the comprehensive elastic modulus of the hydraulic cylinder; B p is the overall viscous damping coefficient, C is the total leakage coefficient;

[0042] The transfer function between the proposed hydraulic cylinder piston rod displacement and the external load of the system is:

[0043]

[0044] in A p is the effective area of ​​the hydraulic cylinder, V t is the total volume of the hydraulic cylinder; C is the total leakage coefficient; m t is the total mass of the hydraulic cylinder piston and the load, β e is the comprehensive elastic modulus of the hydraulic cylinder; B p is the overall viscous damping coefficient;

[0045] First, the bilinear transformation formula is used to transform the transfer function of the system into a discrete equation, and then:

[0046]

[0047] In the above formula, T is the sampling time; Substituting this back into the transfer function we get:

[0048]

[0049] Suppose: B0=D+K3; B1=D+3K3; B2=-D+3K3; B3=-D+K3; A0=A+B+C; A1=-3A-B+C; A2=3A-BC; A3=-A+BC; then:

[0050]

[0051] Therefore, there are:

[0052]

[0053] In the above formula, x p (k) represents the piston rod displacement data collected by the system at discrete time point k, x p (k-1) is the piston rod displacement data collected at time point k-1, x p (k-2) is the piston rod displacement data collected at time point k-2, x p (k-3) is the piston rod displacement data collected at time point k-3; n p (k) represents the system input speed data at discrete time point k, n p (k-1) is the input speed data of the system at time point k-1, n p (k-2) is the input speed data of the system at time point k-2, n p (k-3) is the data of the system input speed at time point k-3.

[0054] In a preferred embodiment of the present invention, the specific steps of step S4 include:

[0055] Use MATLAB software to convert the discrete equation into a time-continuous transfer function equation and obtain the parameter matrix of the hydraulic cylinder system:

[0056] (1) When there is no external load on the hydraulic cylinder system:

[0057] [K,x,y]

[0058] in A p D is the effective area of ​​the hydraulic cylinder. p is the displacement of the plunger pump; m t is the total mass of the hydraulic cylinder piston and the load, V t is the total volume of the hydraulic cylinder, β e is the comprehensive elastic modulus of the hydraulic cylinder; B p is the overall viscous damping coefficient, C is the total leakage coefficient;

[0059] (2) When the hydraulic cylinder system is subject to external load:

[0060] [K1, K2, K3, x, y

[0061] in A p D is the effective area of ​​the hydraulic cylinder. pis the displacement of the plunger pump; V t is the total volume of the hydraulic cylinder; C is the total leakage coefficient,; m t is the total mass of the hydraulic cylinder piston and the load, β e is the comprehensive elastic modulus of the hydraulic cylinder; B p is the overall viscous damping coefficient.

[0062] The beneficial effects of the present invention are:

[0063] (1) The present invention can improve system performance, optimize the dynamic response characteristics of the system, improve system stability, accelerate response speed and reduce overshoot by adjusting the transfer function of the hydraulic cylinder system. The transfer function can also intuitively understand the frequency characteristics of the system, help engineers quickly identify and adjust key parameters, and simplify the design process of the control system.

[0064] (2) The hydraulic cylinder system parameter calibration method mentioned in the present invention is more flexible and adaptable than other parameter calibration methods, and can be flexibly adjusted according to different application requirements. For example, by adding zero extreme points to avoid the occurrence of a lag between the hydraulic cylinder displacement value and the preset value, etc., it can quickly adapt to changes in different conditions, so that the hydraulic system can always maintain good performance in a variety of environments, and the system can adapt to various working environments and load conditions.

[0065] (3) Since the physical meaning of the transfer function is clear, it can clearly reflect the characteristics of the system, making the parameter calibration process easier to understand and operate. Hydraulic systems are usually affected by nonlinear factors. By adjusting the transfer function of the hydraulic cylinder system, these nonlinear effects can be offset to a certain extent and the linearity of the system can be improved. For example, if the end position of the hydraulic cylinder displacement deviates from the preset position, a gain can be added to the transfer function, and the unique value of the hydraulic cylinder can be continuously adjusted to be within the allowable error range. By optimizing or adjusting the transfer function of the hydraulic cylinder system, the robustness of the system to disturbances and parameter changes can be enhanced, and the overall stability of the system can be improved.

[0066] (4) Through theoretical analysis and simulation, the present invention can perform parameter optimization before actual experiments. Compared with the modification of mechanical structures, adjusting the transfer function parameters is an economical and effective solution that can reduce maintenance costs and extend the service life of equipment, reducing the time and cost of the trial and error process, which not only improves the control effect of the system, but also provides a more effective and convenient tool. BRIEF DESCRIPTION OF THE DRAWINGS

[0067] Figure 1It is a flow chart of a parameter calibration method of a hydraulic cylinder system of the present invention;

[0068] Figure 2 It is a schematic diagram of the constructed hydraulic cylinder system experimental platform;

[0069] Figure 3 It is the principle diagram of the hydraulic system of the hydraulic cylinder system experimental platform;

[0070] Figure 4 is a structural schematic diagram of the hydraulic pump station;

[0071] Figure 5 is a schematic diagram of the structure of the hydraulic cylinder;

[0072] Figure 6 It is the transfer function diagram of the hydraulic cylinder system.

[0073] The components in the attached drawings are marked as follows: 1. Servo motor, 2. Fixed-displacement piston pump, 3. Filter, 4. Safety relief valve, 5. High-pressure filter, 6. Check valve, 7. Oil tank, 8. Air cooling system, 9. Air cooling, 10. Air filter, 11. Hydraulic pump station system, 12. Electro-hydraulic servo valve, 13. Hydraulic cylinder, 14. Displacement sensor, 15. Control cabinet. DETAILED DESCRIPTION

[0074] The preferred embodiments of the present invention are described in detail below in conjunction with the accompanying drawings so that the advantages and features of the present invention can be more easily understood by those skilled in the art, thereby making a clearer and more definite definition of the protection scope of the present invention.

[0075] See also Figure 1 , the embodiment of the present invention includes:

[0076] A method for calibrating parameters of a hydraulic cylinder system comprises the following steps:

[0077] S1: Build a hydraulic cylinder system experimental platform according to the working principle of the hydraulic cylinder system;

[0078] In this example, the schematic diagram of the hydraulic cylinder experimental platform system is as follows: Figure 2 As shown, it includes: hydraulic pump station, hydraulic cylinder 13, and system host computer. The components of the hydraulic pump station system 11 include: servo motor 1, quantitative plunger pump 2, control cabinet 15, oil tank 7, air cooling system 8, safety overflow valve 4, filter 3, high pressure filter 5, check valve 6, air filter 10 and other components. The structural diagram of the pump station is shown in Figure 4 As shown; the hydraulic cylinder 13 itself carries a displacement sensor 14 and an electro-hydraulic servo valve 12, and the structure of the hydraulic cylinder is shown in Figure 5 shown.

[0079] like Figure 3As shown, the working principle of the hydraulic cylinder system experimental platform is as follows: the controller in the control cabinet 15 sends a control signal to the entire pump station, and the servo motor 1 receives the control signal to drive the quantitative plunger pump 2 to rotate, and deliver high-pressure oil to the entire hydraulic system. At the same time, in order to prevent the internal pressure of the pump station system from being too high, the temperature is too high, and other safety components in the pump station, such as air cooling 9 and overflow valves, also enter the working state. The valve of the electro-hydraulic servo valve 12 maintains a certain opening when the hydraulic cylinder 13 is working. The oil flows through the servo valve, and the pressure in the hydraulic cylinder 13 changes, thereby driving the piston movement of the hydraulic cylinder 13. The movement of the hydraulic cylinder 13 can achieve linear or reciprocating motion, which is used to perform mechanical operations. After the displacement signal collected by the displacement sensor 14 is processed by the data of the conversion module, the transfer function of the hydraulic cylinder system is calibrated using MATLAB software.

[0080] S2: Establishing a mathematical model of the hydraulic cylinder system and obtaining a transfer function of the hydraulic cylinder system; the specific steps include:

[0081] According to the working principle and composition structure of the hydraulic cylinder workstation, the open-loop transfer function of the hydraulic cylinder system can be divided into two cases: with external load and without external load.

[0082] (1) When the hydraulic cylinder system has an external load:

[0083] The flow equation for the plunger pump is:

[0084] Q p =D p n p -C tp p l

[0085] In the above formula, Q p D is the output flow of the plunger pump; p is the displacement of the plunger pump; n p Input speed of the system; C tp is the leakage coefficient of the plunger pump; p l is the system pressure.

[0086] The flow continuity equation of the hydraulic cylinder is:

[0087]

[0088] In the above formula, C tc is the hydraulic cylinder leakage coefficient; A p V is the effective area of ​​the hydraulic cylinder; t is the total volume of the hydraulic cylinder; β e is the comprehensive elastic modulus of the hydraulic cylinder, and the other parameters are consistent with the above; the three items in the formula are the total leakage of the hydraulic cylinder; the driving flow required for the normal operation of the hydraulic cylinder; and the total compression flow.

[0089] According to Newton's second law, the force balance equation of the hydraulic cylinder during normal operation is:

[0090]

[0091] In the above formula, x p is the displacement of the hydraulic cylinder piston; m t is the total mass of the hydraulic cylinder piston and the load; B p is the overall viscous damping coefficient; F L is the external load force acting on the hydraulic cylinder piston, and the other parameters are the same as above.

[0092] Since the system does not contain elastic loads, the force balance equation of the hydraulic cylinder during normal operation does not include the spring stiffness of the hydraulic cylinder piston rod and the load.

[0093] Combining the above three equations and performing pull-type transformation, we get:

[0094]

[0095] Determine the natural frequency of the transfer function of the hydraulic cylinder system Damping ratio of the transfer function of the hydraulic cylinder system Where C is the total leakage coefficient C = C tc +C tp ; Then by arranging and simplifying the above formula, we can get:

[0096]

[0097] At this time, the transfer function of the hydraulic cylinder piston rod displacement and the plunger pump speed is:

[0098]

[0099] The transfer function of the hydraulic cylinder piston rod displacement and external load force is:

[0100]

[0101] (2) When the hydraulic cylinder system has no external load, the flow equation of the plunger pump is: Q p =D p n p -C tp p l Flow continuity equation with hydraulic cylinder: It remains the same as when the hydraulic cylinder system has an external load, and the force balance equation of the hydraulic cylinder in normal operation is:

[0102]

[0103] In the above formula, x p is the displacement of the hydraulic cylinder piston; m t is the total mass of the hydraulic cylinder piston and the load; B p is the overall viscous damping coefficient, and the other parameters are the same as above.

[0104] Since the system does not contain elastic loads, the force balance equation of the hydraulic cylinder during normal operation does not include the spring stiffness of the hydraulic cylinder piston rod and the load.

[0105] Combining the above three equations and performing pull-type transformation, we get:

[0106]

[0107] Determine the natural frequency of the transfer function of the hydraulic cylinder system Damping ratio of the transfer function of the hydraulic cylinder system Where C is the total leakage coefficient C = C tc +C tp ; Then by arranging and simplifying the above formula, we can get:

[0108]

[0109] At this time, the transfer function of the hydraulic cylinder piston rod displacement and the plunger pump speed is:

[0110]

[0111] In summary, the transfer function of the hydraulic cylinder system is as follows: Figure 6 shown.

[0112] The displacement D of the plunger pump that appears in the derivation process of the transfer function of the hydraulic cylinder system above p 、Effective area of ​​hydraulic cylinder A p 、Total volume of hydraulic cylinder V t , the total mass of the hydraulic cylinder piston and the load m t All of them can be calculated through component technical indicators and component nominal dimensions, without the need to perform parameter calibration again.

[0113] S3: According to the basic principle of least square method and using bilinear transformation formula, the transfer function of hydraulic cylinder system is transformed into discrete equation;

[0114] S4: Calculate the parameter matrix of the hydraulic cylinder system and complete the parameter calibration of the hydraulic cylinder system.

[0115] The system parameter calibration process mentioned in steps S3 and S4 is specifically as follows:

[0116] (1) When the hydraulic cylinder system has no external load, there is no external interference in the hydraulic cylinder system. At this time, the system only has a transfer function between the displacement of the hydraulic cylinder piston rod and the input speed of the system. Based on the above derivation process of the transfer function of the hydraulic cylinder system, the transfer function of the hydraulic cylinder system is proposed as follows:

[0117]

[0118] in A p D is the effective area of ​​the hydraulic cylinder. p is the displacement of the plunger pump; m t is the total mass of the hydraulic cylinder piston and the load, V t is the total volume of the hydraulic cylinder, β e is the comprehensive elastic modulus of the hydraulic cylinder; B p is the overall viscous damping coefficient, and C is the total leakage coefficient.

[0119] According to the basic principle of least square method, the transfer function of the hydraulic cylinder system is identified: firstly, the transfer function of the system is transformed into a discrete equation using the bilinear transformation formula, and then:

[0120]

[0121] In the above formula, T is the sampling time; Then bring it back to the transfer function and we get:

[0122]

[0123] Proposed: B0=B3=K; B1=B2=3K; A0=A+B+C; A1=-3A-B+C; A2=3A-BC; A3=-A+BC;

[0124] but:

[0125]

[0126] Therefore, there are:

[0127]

[0128] In the above formula, x p (k) represents the piston rod displacement data collected by the system at discrete time point k, x p (k-1) is the piston rod displacement data collected at time point k-1, x p (k-2) is the piston rod displacement data collected at time point k-2, x p (k-3) is the piston rod displacement data collected at time point k-3; np (k) represents the system input speed data at discrete time point k, n p (k-1) is the input speed data of the system at time point k-1, n p (k-2) is the input speed data of the system at time point k-2, n p (k-3) is the data of the system input speed at time point k-3.

[0129] The above formula can be rewritten as:

[0130]

[0131] Rewriting the above formula into matrix form:

[0132] x p (k) = N (k) θ + e (k)

[0133] In the above formula, e(k) is the error matrix; N(k) = (-x p (k-1),…,-x p (kn),n p (k),…,n p (kn));θ=(a1,…,a n, b 0, …,b n );

[0134] After observing N sets of data, the above formula can be rewritten as:

[0135] X=Nθ+e

[0136] At this time, the error index of the system is

[0137]

[0138] When the system error index J = 0, the parameter matrix can be obtained as:

[0139]

[0140] After obtaining the parameter matrix, we can get the above x p The discrete equation of (k) can be converted into a time-continuous transfer function equation using MATLAB software, that is, In the form of, we can get the parameter matrix of the hydraulic cylinder system, which is as follows:

[0141] [K,x,y]

[0142] in A p D is the effective area of ​​the hydraulic cylinder. p is the displacement of the plunger pump; m t is the total mass of the hydraulic cylinder piston and the load, V t is the total volume of the hydraulic cylinder, β e is the comprehensive elastic modulus of the hydraulic cylinder; B p is the overall viscous damping coefficient, and C is the total leakage coefficient.

[0143] (2) When the hydraulic cylinder system is subject to external load, there is external interference in the hydraulic cylinder system. At this time, in addition to the transfer function between the hydraulic cylinder piston rod displacement and the motor input speed, the system also has a transfer function between the hydraulic cylinder piston rod displacement and the external load of the system. Based on the above derivation process of the transfer function of the hydraulic cylinder system, the transfer function between the hydraulic cylinder piston rod displacement and the system input speed is proposed as follows:

[0144]

[0145] in A p D is the effective area of ​​the hydraulic cylinder. p is the displacement of the plunger pump; m t is the total mass of the hydraulic cylinder piston and the load, V t is the total volume of the hydraulic cylinder, β e is the comprehensive elastic modulus of the hydraulic cylinder; B p is the overall viscous damping coefficient, and C is the total leakage coefficient.

[0146] The transfer function between the displacement of the hydraulic cylinder piston rod and the load outside the system is:

[0147]

[0148] in A p is the effective area of ​​the hydraulic cylinder, V t is the total volume of the hydraulic cylinder; C is the total leakage coefficient,; m t is the total mass of the hydraulic cylinder piston and the load, β e is the comprehensive elastic modulus of the hydraulic cylinder; B p is the overall viscous damping coefficient.

[0149] The identification process of K1 is the same as when the system has no external load. For K2 and K3, the bilinear transformation formula is first used to transform the transfer function of the system into a discrete equation, and then:

[0150]

[0151] In the above formula, T is the sampling time; Then bring it back to the transfer function and we get:

[0152]

[0153] Drafted: B0=D+K3; B1=D+3K3; B2=-D+3K3; B3=-D+K3; A0=A+B+C; A1=-3A-B+C; A2=3A-BC; A3=-A+BC;

[0154] but:

[0155]

[0156] The rest of the process is the same as when the system has no external load and will not be described here.

[0157] The parameter matrix of the hydraulic cylinder system that can be obtained in the end is as follows:

[0158] [K1, K2, K3, x, y

[0159] in A p D is the effective area of ​​the hydraulic cylinder. p is the displacement of the plunger pump; V t is the total volume of the hydraulic cylinder; C is the total leakage coefficient; m t is the total mass of the hydraulic cylinder piston and the load, β e is the comprehensive elastic modulus of the hydraulic cylinder; B p is the overall viscous damping coefficient.

[0160] The above descriptions are merely embodiments of the present invention and are not intended to limit the patent scope of the present invention. Any equivalent structure or equivalent process transformation made using the contents of the present invention specification and drawings, or directly or indirectly applied in other related technical fields, are also included in the patent protection scope of the present invention.

Claims

1. A method for calibrating parameters of a hydraulic cylinder system, characterized in that: The following steps are involved: S1: Build a hydraulic cylinder system experimental platform according to the working principle of the hydraulic cylinder system; S2: Establishing a mathematical model of the hydraulic cylinder system and obtaining a transfer function of the hydraulic cylinder system; S3: According to the basic principle of least square method and using bilinear transformation formula, the transfer function of hydraulic cylinder system is transformed into discrete equation; S4: Calculate the parameter matrix of the hydraulic cylinder system and complete the parameter calibration of the hydraulic cylinder system.

2. The parameter calibration method of the hydraulic cylinder system according to claim 1, characterized in that: In step S1, the constructed hydraulic cylinder system experimental platform includes a system host computer, a hydraulic pump station, and a hydraulic cylinder. The system host computer sends a control signal to the hydraulic pump station, the hydraulic pump station sends a drive signal to the hydraulic cylinder, the hydraulic pump station drives the hydraulic cylinder to move, and the displacement sensor on the hydraulic cylinder feeds back the displacement signal to the system host computer. The system host computer uses MATLAB software to calibrate the parameters of the transfer function of the hydraulic cylinder system.

3. The parameter calibration method of the hydraulic cylinder system according to claim 1, characterized in that: In step S2, the mathematical model and transfer function of the hydraulic cylinder system are divided into two cases: with external load and without external load, and the establishment basis is respectively: (1) When the hydraulic cylinder system is subject to external load: Flow equation Q of plunger pump p =D p n p -C tp p l ; Flow continuity equation of hydraulic cylinder The force balance equation of the hydraulic cylinder during normal operation (2) When there is no external load on the hydraulic cylinder system: Flow equation Q of plunger pump p =D p n p -C tp p l ; Flow continuity equation of hydraulic cylinder The force balance equation of the hydraulic cylinder during normal operation In the above formula, Q p D is the output flow of the plunger pump; p is the displacement of the plunger pump; n p Input speed of the system; C tp is the leakage coefficient of the plunger pump; p l is the system pressure; C tc is the hydraulic cylinder leakage coefficient; A p V is the effective area of ​​the hydraulic cylinder; t is the total volume of the hydraulic cylinder; β e is the comprehensive elastic modulus of the hydraulic cylinder; x p is the displacement of the hydraulic cylinder piston; m t is the total mass of the hydraulic cylinder piston and the load; B p is the overall viscous damping coefficient; F L is the external load force acting on the hydraulic cylinder piston; The flow equation of the plunger pump, the flow continuity equation of the hydraulic cylinder and the force balance equation of the hydraulic cylinder in normal operation are transformed into the following: (1) When the hydraulic cylinder system is subject to external load: (2) When there is no external load on the hydraulic cylinder system: The above two combined equations are calculated and sorted to obtain the transfer function of the hydraulic cylinder system.

4. The parameter calibration method of the hydraulic cylinder system according to claim 1, characterized in that: The specific steps of step S3 include: (1) When there is no external load on the hydraulic cylinder system, there is no external interference in the hydraulic cylinder system. At this time, the system only has a transfer function between the displacement of the hydraulic cylinder piston rod and the input speed of the system. The transfer function of the proposed hydraulic cylinder system is: in A p D is the effective area of ​​the hydraulic cylinder. p is the displacement of the plunger pump; m t is the total mass of the hydraulic cylinder piston and the load, V t is the total volume of the hydraulic cylinder, β e is the comprehensive elastic modulus of the hydraulic cylinder; B p is the overall viscous damping coefficient, C is the total leakage coefficient; According to the basic principle of least square method, the transfer function of the hydraulic cylinder system is identified. First, the transfer function of the system is transformed into a discrete equation using the bilinear transformation formula. Let: In the above formula, T is the sampling time; Substituting this back into the transfer function we get: Suppose: B0=B3=K; B1=B2=3K; A0=A+B+C; A1=-3A-B+C; A2=3A-BC; A3=-A+BC; then: Therefore, there are: In the above formula, x p (k) represents the piston rod displacement data collected by the system at discrete time point k, x p (k-1) is the piston rod displacement data collected at time point k-1, x p (k-2) is the piston rod displacement data collected at time point k-2, x p (k-3) is the piston rod displacement data collected at time point k-3; n p (k) represents the system input speed data at discrete time point k, n p (k-1) is the input speed data of the system at time point k-1, n p (k-2) is the input speed data of the system at time point k-2, n p (k-3) is the data of the system input speed at time point k-3; (2) When the hydraulic cylinder system is subject to external load, there is external interference in the hydraulic cylinder system. The system includes the transfer function between the displacement of the hydraulic cylinder piston rod and the motor input speed, and the transfer function between the displacement of the hydraulic cylinder piston rod and the external load of the system. At this time, the transfer function between the displacement of the hydraulic cylinder piston rod and the input speed of the system is proposed as follows: in A p D is the effective area of ​​the hydraulic cylinder. p is the displacement of the plunger pump; m t is the total mass of the hydraulic cylinder piston and the load, V t is the total volume of the hydraulic cylinder, β e is the comprehensive elastic modulus of the hydraulic cylinder; B p is the overall viscous damping coefficient, C is the total leakage coefficient; The transfer function between the proposed hydraulic cylinder piston rod displacement and the external load of the system is: in A p is the effective area of ​​the hydraulic cylinder, V t is the total volume of the hydraulic cylinder; C is the total leakage coefficient; m t is the total mass of the hydraulic cylinder piston and the load, β e is the comprehensive elastic modulus of the hydraulic cylinder; B p is the overall viscous damping coefficient; First, the bilinear transformation formula is used to transform the transfer function of the system into a discrete equation, and then: In the above formula, T is the sampling time; Substituting this back into the transfer function we get: Suppose: B0=D+K3; B1=D+3K3; B2=-D+3K3; B3=-D+K3; A0=A+B+C; A1=-3A-B+C; A2=3A-BC; A3=-A+BC; then: Therefore, there are: In the above formula, x p (k) represents the piston rod displacement data collected by the system at discrete time point k, x p (k-1) is the piston rod displacement data collected at time point k-1, x p (k-2) is the piston rod displacement data collected at time point k-2, x p (k-3) is the piston rod displacement data collected at time point k-3; n p (k) represents the system input speed data at discrete time point k, n p (k-1) is the input speed data of the system at time point k-1, n p (k-2) is the input speed data of the system at time point k-2, n p (k-3) is the data of the system input speed at time point k-3.

5. The parameter calibration method of the hydraulic cylinder system according to claim 1, characterized in that: The specific steps of step S4 include: Use MATLAB software to convert the discrete equation into a time-continuous transfer function equation and obtain the parameter matrix of the hydraulic cylinder system: (1) When there is no external load on the hydraulic cylinder system: [K, x, y] in A p D is the effective area of ​​the hydraulic cylinder. p is the displacement of the plunger pump; m t is the total mass of the hydraulic cylinder piston and the load, V t is the total volume of the hydraulic cylinder, β e is the comprehensive elastic modulus of the hydraulic cylinder; B p is the overall viscous damping coefficient, C is the total leakage coefficient; (2) When the hydraulic cylinder system is subject to external load: [K1, K2, K3, x, y] in A p D is the effective area of ​​the hydraulic cylinder. p is the displacement of the plunger pump; V t is the total volume of the hydraulic cylinder; C is the total leakage coefficient; m t is the total mass of the hydraulic cylinder piston and the load, β e is the comprehensive elastic modulus of the hydraulic cylinder; B p is the overall viscous damping coefficient.

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