A proportional reference state feedback control method for direct drive valve based on inverse system

Abstract

The present invention provides a proportional reference state feedback control method for a direct-drive valve based on an inverse system, which belongs to the field of control. The method comprises: linearizing the direct-drive valve through an inverse system method, that is, constructing an equivalent linear inverse system so that the original nonlinear system behaves as a linear system under the action of the inverse system. The application of the inverse system method can effectively simplify the controller design process and improve the controllability of the system. Secondly, based on the linearized system model, a proportional reference state feedback controller is designed. The controller performs feedback control on the system state by introducing a proportional reference signal, thereby achieving accurate tracking of the target position and speed. The design of the controller takes into account the dynamic characteristics and external interference of the system, ensuring the stability and robustness of the system under different working conditions.

Description

Technical Field

[0001] The present invention mainly relates to the field of control-related technologies, and in particular to a proportional reference state feedback control method for a direct-drive valve based on an inverse system. Background Art

[0002] A direct-drive valve is a hydraulic valve that directly drives the valve core to move through electromagnetic force. Compared with traditional servo valves and proportional valves, direct-drive valves are suitable for high-speed dynamic control occasions and can achieve high-precision valve core position control, thereby accurately adjusting the flow and pressure of the hydraulic system. Due to these advantages, direct-drive valves are widely used in aerospace, industrial automation, hydraulic control systems and other fields.

[0003] Although direct-drive valves have many advantages, their control still faces many challenges: direct-drive valve systems usually have significant nonlinear characteristics, such as the nonlinear relationship between electromagnetic force and current, and the friction nonlinearity of valve core movement. These nonlinear factors make it difficult for traditional linear control methods to achieve ideal control effects. In practical applications, direct-drive valve systems are often affected by external interference and changes in system parameters, which can lead to a decrease in system performance. Many application scenarios have extremely high requirements for the control accuracy and dynamic performance of direct-drive valves, requiring the control system to achieve precise valve core position control in a short time.

[0004] In the field of direct-drive valve control, common control methods include PID control, adaptive control and fuzzy control. PID control is the most common control method, with the advantages of simple structure and easy implementation. However, PID control has poor performance when dealing with nonlinear systems and large-scale parameter changes, and it is difficult to meet the requirements of high precision and high dynamic performance. Adaptive control can automatically adjust the control strategy according to the changes in system parameters, and has good robustness and adaptability. However, the design and implementation of adaptive control are relatively complex, with large amount of calculation and poor real-time performance. Fuzzy control is a control method based on empirical rules, which is suitable for dealing with nonlinear and uncertain systems. Fuzzy control does not rely on precise mathematical models, but its control effect depends on the design of the rule base, and it is difficult to guarantee global optimal performance.

[0005] The inverse system method is an effective nonlinear control technology. By constructing an equivalent linear inverse system, the original nonlinear system is made to behave as a linear system under the action of the inverse system, which simplifies the controller design process. It can also effectively eliminate the nonlinear effects of the system, maintain good control performance in the face of external interference and parameter changes, and ensure the stability and reliability of the system.

[0006] The proportional reference state feedback controller is a classic control strategy. The direct drive valve is linearized by the inverse system method and combined with the proportional reference state feedback controller to achieve accurate tracking of the target position and speed. Enhance the robustness and anti-interference ability of the system: This combined method can maintain good control performance in the face of external interference and parameter changes, ensure the stability and reliability of the system, and facilitate engineering applications.

[0007] In summary, the research and development of a proportional reference state feedback controller based on an inverse system has important theoretical significance and practical application value for the high-performance control of direct-drive valves. Summary of the invention

[0008] In order to solve the shortcomings of the current technology, the present invention combines the existing technology and, starting from practical applications, provides a proportional reference state feedback control method for direct-drive valves based on an inverse system. This control strategy can not only improve the control accuracy and dynamic performance of the system, but also has good robustness and anti-interference ability, which provides strong support for the widespread application of direct-drive valves in modern industry.

[0009] The technical solution of the present invention is as follows:

[0010] A proportional reference state feedback control method for a direct-drive valve based on an inverse system, wherein the valve core of the direct-drive valve is driven by an electromagnetic linear actuator, and the control method comprises the following steps:

[0011] S1. A mathematical model of the direct-drive valve is established based on the direct-drive valve core motion equation, the circuit voltage Kirchhoff voltage balance equation, the electromagnetic force and the back electromotive force equation;

[0012] S2. Establish a state observer to measure the state variables of the direct-drive valve system. The state observer adds a feedback matrix to the equivalent model of the direct-drive valve state equation, takes the actual control quantity and output of the direct-drive valve as input, and takes the state vector estimation value as output;

[0013] S3, pseudo-linearizing the direct-drive valve and constructing an equivalent linear inverse system, so that the original nonlinear system of the direct-drive valve behaves as a linear system under the action of the inverse system, and finally obtaining a pseudo-linear system of the direct-drive valve;

[0014] S4. Design a state feedback controller based on a pseudo-linear system. The state feedback controller adopts a proportional reference state feedback control method.

[0015] Further, in step S1, the mathematical model expression of the direct drive valve is as follows:

[0016] ,

[0017] In the formula, is the power supply voltage, is the current in the coil, is the coil resistance, is the coil inductance, is the electromagnetic force constant, is the spool speed of the direct drive valve, is the electromagnetic force, is the magnetic field strength, is the number of coil turns, is the coil length, It is the steady-state hydraulic force generated by the hydraulic oil in the valve cavity of the direct-drive valve. is the electromagnetic force, is the magnetic field strength, is the number of coil turns, is the coil length, It is the steady-state hydraulic force generated by the hydraulic oil in the valve cavity of the direct-drive valve. It is the transient hydraulic force generated by the hydraulic oil in the valve cavity of the direct drive valve. is the friction force, is the total mass including the electromagnetic linear actuator, valve core, connectors, and springs. is the displacement of the valve core, is the damping coefficient; is the stiffness of the spring.

[0018] Furthermore, the steady-state hydraulic force generated by the hydraulic oil in the valve chamber of the direct-drive valve and transient fluid power The calculation is limited as follows:

[0019] 1) Ignore the pressure loss along the pipeline caused by viscous friction between the inside and the hydraulic oil, and the potential energy of the hydraulic oil is negligible, and the length of the oil line has no effect on the system;

[0020] 2) The kinetic energy correction factor is 1;

[0021] 3) The entire system is well sealed and there is no hydraulic oil leakage problem.

[0022] Furthermore, steady-state fluid dynamics The calculation formula is as follows:

[0023] ,

[0024] Transient fluid power The calculation formula is as follows:

[0025] ,

[0026] In the formula, is the jet angle, that is, the angle between the positive direction of the equivalent integrated hydraulic oil flow and the axial centerline of the valve core. is the flow coefficient, is the valve port area gradient, using calculate, is the valve core diameter, is the oil density, is the pressure difference at the valve port, is the liquid oil length in the working chamber.

[0027] Further, in step S2, the state observer is established as follows:

[0028] Select the state vector of the direct-actuated valve, which includes the current in the coil , valve core speed of direct drive valve , displacement of valve core Based on the state vector and the mathematical model of the direct-drive valve, a state equation representing the state space of the direct-drive valve is obtained;

[0029] A model equivalent to the state equation of the direct-drive valve is constructed, the state vector of the direct-drive valve is measured from the equivalent model, and the output error is used as negative feedback to obtain the state observer equation.

[0030] Furthermore, the state observer equation is expressed as follows:

[0031] ,

[0032] In the formula, is the power supply voltage, is the feedback gain matrix, , , are the coefficients of the feedback gain matrix, is the coil inductance, is the displacement of the valve core, is the state vector The estimated value of is the coefficient matrix of the state variables, is the input coefficient matrix, is the output coefficient matrix, is the estimated value of the current, is the valve core speed of the direct drive valve The estimated value of is the valve core displacement The estimated value of .

[0033] Further, in step S3, the pseudo linearization process of the direct-drive valve is specifically performed as follows:

[0034] Solve the inverse system based on the original direct drive valve system, and further find out based on the inverse system After the inverse system is established, The inverse system is placed in front of the original system. The part of the state variables that characterize the dynamic performance of the inverse system that can be replaced by the original system is replaced by the state variables of the original system. The structure is simplified by using feedback replacement. Finally, the constructed pseudo-linear system of the direct-drive valve is taken as the controlled object and the controller is designed using linear theory to achieve the corresponding control objectives.

[0035] Furthermore, the inverse system and The inverse system expression is as follows:

[0036] ,

[0037] In the formula, is the power supply voltage, is the coil inductance, is the electromagnetic force constant, is the damping coefficient, is the jet angle, is the flow coefficient, is the valve port area gradient, is the length of liquid oil in the working chamber, is the total mass including the electromagnetic linear actuator, valve core, connectors, and springs. is the oil density, is the pressure difference at the valve port, is the coil resistance, is the current in the coil, is the stiffness of the spring, is the acceleration of the valve core movement, is the displacement of the valve core.

[0038] Further, in step S4, the state feedback control method is specifically:

[0039] The multi-row and one-column matrix composed of the state variables of the original system is multiplied by the feedback coefficient in the feedback gain matrix with one row and multiple columns. The matrix multiplication obtains a polynomial, and the result is the corresponding numerical value. This numerical value is fed back to the input end to form a control law with the input target command to control the corresponding action of the controlled object.

[0040] Furthermore, the control equation of the state feedback device is as follows:

[0041] ,

[0042] In the formula, is the state vector of the pseudo-linear system, is the feedback gain matrix, is the corresponding proportionality coefficient, To control the target, is the coefficient matrix of the state variables of the pseudo-linear system, is the coefficient matrix of the pseudo-linear system input, is the coefficient matrix output by the pseudo-linear system, is the displacement of the valve core.

[0043] Beneficial effects of the present invention:

[0044] The invention discloses a proportional reference state feedback control method for a direct-drive valve based on an inverse system. The mathematical model of the direct-drive valve system is solved inversely to obtain an inverse system model, and a proportional reference state feedback controller is designed. Based on the linear system theory, the control input is calculated using the state feedback information of the system, so that the system can track a given reference input. The inverse system is used as a feedforward compensator and placed at the input end of the direct-drive valve system to offset the nonlinear characteristics of the system, so that the entire system behaves as a linear system. The inverse system and the proportional reference state feedback controller are connected in series to form a complete closed-loop control system. The inverse system is responsible for nonlinear compensation, and the state feedback controller is responsible for precise control, so that the direct-drive valve system can operate efficiently and stably, and can effectively compensate for the nonlinear characteristics of the direct-drive valve, so that the system can accurately track the reference input and improve the control accuracy. The method is suitable for high-precision and high-response speed industrial control scenarios. BRIEF DESCRIPTION OF THE DRAWINGS

[0045] Figure 1 It is the overall block diagram of the control method of the present invention;

[0046] Figure 2 The performance comparison diagram of the control method of the present invention and other control methods at different displacements in step response;

[0047] Figure 3 This is a performance comparison diagram of step response when parameters are perturbed between the control method of the present invention and other control methods. DETAILED DESCRIPTION

[0048] The present invention will be further described with reference to the accompanying drawings and specific embodiments. It should be understood that these embodiments are only used to illustrate the present invention and are not intended to limit the scope of the present invention. In addition, it should be understood that after reading the content taught by the present invention, those skilled in the art may make various changes or modifications to the present invention, and these equivalent forms also fall within the scope limited by the application.

[0049] This embodiment provides a proportional reference state feedback control method for a direct-drive valve based on an inverse system, the purpose of which is to compensate for the nonlinear characteristics of the direct-drive valve system. The direct-drive valve is linearized by the inverse system method, the input-output relationship of the original system is reversed, and a pseudo-linear system of the direct-drive valve is formed. In combination with a proportional reference state feedback controller, the proportional reference state feedback controller is used to feedback and adjust the system state to further improve the dynamic performance and robustness of the system. The combination of the two can transform complex nonlinear control problems into linear control problems, simplifying the controller design process. The relevant technology of this embodiment is intended to improve the overall performance of the direct-drive valve system and meet the needs of industrial automation and precision control.

[0050] The technical solution of this embodiment is mainly as follows.

[0051] A proportional reference state feedback control method for a direct-drive valve based on an inverse system mainly includes the following steps:

[0052] S1. Establish a mathematical model of the direct-drive valve;

[0053] S2, establish a state observer to measure state variables such as velocity and acceleration;

[0054] S3, pseudo-linearizing the direct-drive valve, that is, constructing an equivalent linear inverse system so that the original nonlinear system behaves as a linear system under the action of the inverse system;

[0055] S4. Design a state feedback controller based on pseudo-linear system.

[0056] The mathematical model established in step S1 is specifically as follows:

[0057] The movement of the valve core of the direct-drive valve is achieved by an electromagnetic linear actuator. It is a complex system formed by the interconnection of subsystems such as the mechanical subsystem actuator force model, the magnetic circuit subsystem model, and the circuit subsystem voltage balance. The direct-drive valve also needs to consider the force of the hydraulic system.

[0058] According to Newton's second law, the acceleration law, the differential equation for the corresponding movement of the direct-drive valve core is:

[0059] (1),

[0060] In the formula, Total mass including electromagnetic linear actuator, valve core, connectors, and springs; is the valve core speed of the direct drive valve; is the damping coefficient; is the stiffness of the spring; is the electromagnetic force; It is the equivalent integrated force of the transient and steady-state hydraulic forces generated by the hydraulic oil in the valve cavity of the direct-drive valve; is the friction force; the displacement of the valve core is .

[0061] The components of hydraulic force mainly include steady-state hydraulic force and transient hydraulic force.

[0062] (1) Steady-state fluid dynamics The calculation is as follows:

[0063] (2),

[0064] (3),

[0065] In the formula, It is the jet angle, that is, the angle between the positive direction of the equivalent integrated hydraulic oil flow and the axial centerline of the valve core. It is usually taken as 69° according to engineering needs.

[0066] For the purpose of fast response of the direct-actuated valve, the following assumptions need to be made about the system.

[0067] (1) Ignore the pressure loss along the pipeline caused by viscous friction between the inside and the hydraulic oil. At the same time, the potential energy of the hydraulic oil can be ignored, and the length of the oil line has no effect on the system.

[0068] (2) The kinetic energy correction factor is 1;

[0069] (3) The entire system is well sealed and there is no leakage of hydraulic oil;

[0070] Based on all the above assumptions, the Bernoulli equation can be simply regarded as:

[0071] (4),

[0072] In the formula, is the oil source pressure, is the oil pressure entering the valve. is the kinetic energy correction factor, is the liquid flow rate, is the oil density.

[0073] Simplify formula (4) to:

[0074] (5),

[0075] In the formula, is the pressure difference at the valve port, which can be expressed as:

[0076] (6),

[0077] In the formula, is the valve core displacement, It is the oil pressure of the oil flowing out of the valve.

[0078] The flow equation is:

[0079] (7),

[0080] in is the flow coefficient, usually taken as 0.61, is the valve port area gradient, usually used calculate, is the valve core diameter.

[0081] Combining the above formula, the steady-state fluid force can be obtained The expression is:

[0082] (8),

[0083] when The value is 0.61. When the value is 69°, the steady-state fluid force The calculation is as follows:

[0084] (9).

[0085] (2) Transient fluid power The calculation is as follows:

[0086] (10),

[0087] In the formula, is the liquid oil length in the working chamber.

[0088] Regarding friction: the traditional friction model describes the relationship between the force and the differential of the motion displacement of the system response component. This traditional model describes the static friction characteristics, but the dynamic friction characteristics of the motion system during its motion have a significant effect on the system tracking trajectory, and the LuGre model includes complex dynamic friction phenomena such as the Stribeck effect. In this embodiment, the friction can be calculated using the LuGre model. The specific LuGre friction model is shown in the following formula:

[0089] (11),

[0090] In the formula, is the average deformation of the bristles between the contact surfaces; is the valve core speed of the direct drive valve; For about Function of is the friction force; is the Coulomb friction force; is the static friction; , is the design parameter; is the empirical coefficient of the Stribeck effect; For time; is the friction force caused by the average deformation of the bristles between the contact surfaces; is the viscous friction.

[0091] The circuit subsystem of the electromagnetic linear actuator can be equivalent to a circuit consisting of a series connection of resistance, inductance, and back electromotive force generated by the energized coil.

[0092] (12),

[0093] In the formula, To induce back electromotive force; is the number of coil turns; is the magnetic field strength; is the coil length; is the valve core speed of the direct-drive valve; according to Kirchhoff law, the voltage balance equation of the circuit is as follows:

[0094] (13),

[0095] In the formula, is the power supply voltage; is the current in the coil; is the coil resistance; is the coil inductance;

[0096] The driving force of the electromagnetic linear actuator comes from the Ampere force exerted on the coil due to the induced electromotive force in the magnetic field generated by the permanent magnet and the yoke. The electromagnetic force is calculated as follows:

[0097] (14),

[0098] The magnetic field strength in the formula And coil length It depends on the material selected for the moving coil and the internal structure of the electromagnetic linear actuator. The product is a constant, It is called the electromagnetic force constant. From formula (12), we know that It can also be called the back electromotive force constant. In summary, the electromagnetic force formula and the back electromotive force formula can be expressed as:

[0099] (15).

[0100] The system equation of the direct-drive valve based on the electromagnetic linear actuator is established based on the direct-drive valve spool motion equation (1), the circuit voltage Kirchhoff voltage balance equation (13), and the electromagnetic force and back electromotive force equation (15). The system equation is shown as follows:

[0101] (16).

[0102] In step S2, the state observer is established as follows:

[0103] In actual engineering, some state variables of the system are difficult or even impossible to measure, such as the speed and acceleration of the valve core of a direct-drive valve, which are difficult to measure without a sensor. In order to obtain all the state variables of the system, the state observer related technology is introduced to achieve this task.

[0104] The core of the direct-drive valve spool movement control is to control the input voltage of the coil to realize the movement law. The state variable is a set of variables with the minimum number that is sufficient to characterize the system's motion state, so the state vector of the system is selected as:

[0105] (17),

[0106] In the formula, is the current in the coil; is the valve core speed of the direct drive valve; is the displacement of the valve core.

[0107] The state equation of the direct-actuated valve is composed of the state variables of the direct-actuated valve , , The combined first-order linear differential equations can be expressed as follows according to equations (16) and (17):

[0108] (18);

[0109] The output equation is:

[0110] (19),

[0111] In the formula, is the coefficient matrix of the state variables, is the input coefficient matrix, is the output coefficient matrix, is the displacement of the valve core.

[0112] The state observer is designed to estimate the state vector of the direct-drive valve. , and make it as close as possible to the actual state vector of the direct-drive valve system. Therefore, a model equivalent to the state equation of the direct-drive valve system can be constructed:

[0113] (20).

[0114] By comparison, it can be seen that the coefficient matrix in formula (20) is consistent with that in formula (18), so it can be measured from the model , there must be an error between the measured value and the actual value. Since the observability of the system ensures that each output is formed by a unique state vector, the error between the state vector observer observation value and the actual value of the direct-drive valve can determine the error between the observer observation value and the actual value of the system output, that is:

[0115] (twenty one),

[0116] Through the above analysis, the state observer can be obtained by forming a negative feedback with the output error. It can be seen that the equation of the state observer is:

[0117] (twenty two),

[0118] In the formula, is the feedback gain matrix, are the coefficients of the feedback gain matrix.

[0119] The state observer adds a feedback matrix to the system equivalent model, takes the actual system control quantity and output as input, and takes the state vector estimate as output.

[0120] In step S3, the pseudo linear system is established as follows:

[0121] The primary basis of the inverse system method is to feedback linearize the system. The role of feedback linearization is to use its working principle to transform the original nonlinear system into a new, controllable linear system. After that, a simpler linear control knowledge system can be used to track the control target of the system. This method does not rely on various operations on the original nonlinear system, and does not require the use of complex nonlinear control methods. Therefore, the control problem of the nonlinear system becomes no longer complicated, and the system can be analyzed completely and accurately.

[0122] The main method of feedback linearization is the inverse system method. The idea of ​​the inverse system is: for a given system, the output equation of the system is used to establish the inverse system of the system through a continuous derivation method that can only be stopped under certain conditions, and then the inverse system of the system is used to Substituting another parameter produces An inverse system is constructed by placing this system in front of the original system, which constitutes a pseudo-linear system with a linear transfer relationship. After that, the knowledge system of linear control can be used to design a reasonable controller to control the constructed integrator series pseudo-linear system.

[0123] Introduce the basic concepts and principles of the inverse system: Assumptions is a given arbitrary system, when When the input is , the output is , the initial state is , the output of the system is determined by the initial value and the input value. , or written as a simple functional relationship .

[0124] set up For another given system, , the initial state is , For any given is a differentiable function of order, and the function satisfies certain initial conditions at the initial time (whose value is determined by ), if the operator satisfy , then it is called for The inverse system.

[0125] Re-establish For a given system, the initial state , there exists an operator satisfy ,Pick , if exists , then this system is the original system Inverse system.

[0126] according to Definition of the order inverse system So, the composite operator Representation system Equivalent to The series connection of the integrators satisfies ,definition For input, is the output.

[0127] Will The inverse system is connected in series in front of the original system to form a system , this system is called a pseudo-linear system. It is called a pseudo-linear system because the relationship between the input and output of this system is linear, but there may still be complex nonlinear relationships within the system.

[0128] The general steps of inverse system control are:

[0129] (1) Solve the inverse system based on the original system;

[0130] (2) Further obtain the inverse system order inverse system;

[0131] (3) After the establishment is completed, The first-order inverse system is placed in front of the original system, and then the structure is simplified as much as possible by using state feedback, that is, The part of the state variables that characterize the dynamic performance of the inverse system that can be replaced by the original system can be replaced by the feedback of the state variables of the original system to simplify the structure;

[0132] (4) Taking the pseudo-linear system of the direct-drive valve constructed in the first three steps as the controlled object, the linear theory can be used to design a controller to achieve the corresponding control objective.

[0133] The system described by the state equation is , ) The necessary and sufficient condition for judging whether it is reversible is whether the system has a relative order , the general steps for determining the reversibility of a system described by a state equation are:

[0134] (1) Performing the corresponding operation of derivation on the output equation of the above system under certain conditions, that is, stopping until the obtained equation explicitly contains the input quantity;

[0135] (2) If the equation The order derivative is not 0, that is, there is a relative order;

[0136] (3) If the relative order ,and ( is the dimension of the system state vector), then the reversibility of this system can be determined. According to the above conditions, the system is reversible.

[0137] According to the above steps, the reversibility of the direct-drive valve system is analyzed according to the output equation and state equation of the direct-drive valve system.

[0138] First, the output equation is continuously differentiated to obtain:

[0139] (twenty three),

[0140] It can be seen that the relative order is 3, which is equal to the dimension of the state vector, so it can be judged that the direct-drive valve system is reversible.

[0141] Based on the above judgment, the pseudo-linear system of the direct-drive valve is established.

[0142] First, find the inverse system of the original system. The general steps are:

[0143] Assume that the state equation of the original direct-drive valve system and the output equation of the direct-drive valve system are expressed as follows:

[0144] (twenty four).

[0145] Continue to differentiate the output equation until the equation explicitly contains the input term , stop the derivation, and judge from the obtained equation that the highest-order derivative term is not 0. At this time, according to the implicit function theorem and the term shift, we get:

[0146] (25),

[0147] Substitute equation (25) into equation (24) and use replace ,constitute

[0148] (26),

[0149] This system is the system of the original system, and then according to the method of re-input, that is, use , the inverse system is constructed as The system is then placed in front of the original system and the direct drive valve is The state variables in the order inverse system can be replaced by partial feedback of the state variables of the original system of the direct-drive valve, that is, a pseudo-linear system equivalent to the integrator series type direct-drive valve is constructed.

[0150] According to the above analysis, the inverse system of the system and The inverse system equation is:

[0151] (27).

[0152] In step S4, the specific steps are as follows:

[0153] A proportional reference state feedback control method is adopted. The state feedback method is to multiply the multi-row and one-column matrix composed of the state variables of the original system by the feedback coefficient in the feedback gain matrix of one row and multiple columns. The matrix multiplication obtains a polynomial, and the result is the corresponding value. This value is fed back to the input end to form a control law with the input target command to control the corresponding action of the controlled object. Since the state variables can fully characterize the dynamic performance of the system, when using state feedback, the dynamic response characteristics of the system can be freely controlled without increasing the system dimension.

[0154] Assume the state vector of the pseudo-linear system is:

[0155] (28),

[0156] Then the state equation of the pseudo-linear system is:

[0157] (29),

[0158] The control law of the state feedback controller is:

[0159] (30),

[0160] Substituting formula (29) into formula (30), we get:

[0161] (31),

[0162] In the formula, is the feedback gain matrix, is the corresponding proportionality coefficient, To control the goal. is the coefficient matrix of the state variables of the pseudo-linear system, is the coefficient matrix of the pseudo-linear system input, is the coefficient matrix output by the pseudo-linear system, is the displacement of the valve core. The pseudo-linear system already has a linear transfer relationship, and the corresponding linear theory can be used. This embodiment adopts a proportional reference state feedback control method. The state feedback method is to multiply the multi-row and one-column matrix composed of the state variables of the original system by the feedback coefficient in the feedback gain matrix of one row and multiple columns. The matrix multiplication obtains a polynomial, and the result is the corresponding numerical value. This numerical value is fed back to the input end, and forms a control law with the input target instruction to control the corresponding action of the controlled object. Since the state variable can fully characterize the dynamic performance of the system, when using state feedback, the dynamic response characteristics of the system can be freely controlled without increasing the system dimension.

[0163] In order to compare the response speed of this control algorithm with PID control and nonlinear active disturbance rejection control, Figure 2 The response curves of proportional reference state feedback controller and traditional PID control method to direct drive valve spool displacement under 10mm, 8mm and 6mm step response are shown. The results show that the response time of the inverse system proportional reference state feedback controller is faster than that of PID control, and the dynamic performance is better. It can meet the requirement of adjustment time less than 10 milliseconds, and the system response is consistent under different target displacements, without obvious overshoot and instability, which is beneficial to the control of direct drive valve spool.

[0164] Since the coil resistance of most electromagnetic linear actuators is temperature-sensitive, the resistance value of the coil of the electromagnetic linear actuator will change with the change of temperature. In order to require the direct-drive valve to work reliably and accurately, the system controller should have good robustness, that is, the control system should be able to maintain the system performance under the change of certain structural parameters. Figure 3 The response curves of the control system following the step signal when the coil resistance changes by 1.5 times and 2 times are given. It can be seen that the change of the coil resistance using the inverse system method has no obvious effect on the graph of the system tracking the target trajectory, and the direct drive valve control system will not produce obvious overshoot and instability, and the dynamic response characteristics of the system will not change, showing good robustness. However, when the resistance value is different, the curves of PID control are slightly different, and the robustness performance is not as good as the inverse system.

Claims

1. A proportional reference state feedback control method for a direct-drive valve based on an inverse system, wherein the valve core of the direct-drive valve is driven by an electromagnetic linear actuator, characterized in that: The control method comprises the following steps: S1. A mathematical model of the direct-drive valve is established based on the direct-drive valve core motion equation, the circuit voltage Kirchhoff voltage balance equation, the electromagnetic force and the back electromotive force equation; S2. Establish a state observer to measure the state variables of the direct-drive valve system. The state observer adds a feedback matrix to the equivalent model of the direct-drive valve state equation, takes the actual direct-drive valve control quantity and output as input, and takes the state vector estimation value as output. The state observer establishment method is as follows: Select the state vector of the direct-actuated valve, which includes the current in the coil , valve core speed of direct drive valve , displacement of valve core , based on the state vector and the mathematical model of the direct-drive valve, the state equation representing the state space of the direct-drive valve is obtained; A model equivalent to the state equation of the direct-drive valve is constructed, the state vector of the direct-drive valve is measured from the equivalent model, and the output error is used as negative feedback to obtain the state observer equation; S3. Pseudo-linearization is performed on the direct-drive valve to construct an equivalent linear inverse system, so that the original nonlinear system of the direct-drive valve is expressed as a linear system under the action of the inverse system, and finally the pseudo-linear system of the direct-drive valve is obtained. The pseudo-linearization of the direct-drive valve is specifically as follows: Solve the inverse system based on the original direct drive valve system, and further find out based on the inverse system After the inverse system is established, The inverse system is placed in front of the original system. The part of the state variables that characterize the dynamic performance of the inverse system that can be replaced by the original system is replaced by the feedback of the state variables of the original system to simplify the structure. Finally, the constructed pseudo-linear system of the direct-drive valve is taken as the controlled object and the controller is designed using linear theory to achieve the corresponding control target. S4. Design a state feedback controller based on a pseudo-linear system. The state feedback controller adopts a proportional reference state feedback control method. The specific state feedback control method is: The multi-row and one-column matrix composed of the state variables of the original system is multiplied by the feedback coefficient in the feedback gain matrix with one row and multiple columns. The matrix multiplication obtains a polynomial, and the result is the corresponding numerical value. This numerical value is fed back to the input end to form a control law with the input target command to control the corresponding action of the controlled object.

2. The direct-drive valve proportional reference state feedback control method based on the inverse system according to claim 1 is characterized in that: In step S1, the mathematical model expression of the direct drive valve is as follows: ， In the formula, is the power supply voltage, is the current in the coil, is the coil resistance, is the coil inductance, is the electromagnetic force constant, is the spool speed of the direct drive valve, is the electromagnetic force, is the magnetic field strength, is the number of coil turns, is the coil length, It is the steady-state hydraulic force generated by the hydraulic oil in the valve cavity of the direct-drive valve. It is the transient hydraulic force generated by the hydraulic oil in the valve cavity of the direct drive valve. is the friction force, is the total mass including the electromagnetic linear actuator, valve core, connectors, and springs. is the displacement of the valve core, is the damping coefficient; is the stiffness of the spring.

3. The direct-drive valve proportional reference state feedback control method based on the inverse system according to claim 2 is characterized in that: The steady-state hydraulic force generated by the hydraulic oil in the valve cavity of the direct-drive valve and transient fluid power The calculation is limited as follows: 1) Ignore the pressure loss along the pipeline caused by viscous friction between the inside and the hydraulic oil, and the potential energy of the hydraulic oil is negligible, and the length of the oil line has no effect on the system; 2) The kinetic energy correction factor is 1; 3) The entire system is well sealed and there is no hydraulic oil leakage problem.

4. The direct-drive valve proportional reference state feedback control method based on the inverse system according to claim 3 is characterized in that: Steady-state fluid power The calculation formula is as follows: ； Transient fluid power The calculation formula is as follows: ； In the formula, is the jet angle, that is, the angle between the positive direction of the equivalent integrated hydraulic oil flow and the axial centerline of the valve core. is the flow coefficient, is the valve port area gradient, using calculate, is the valve core diameter, is the oil density, is the pressure difference at the valve port, is the liquid oil length in the working chamber.

5. The direct-drive valve proportional reference state feedback control method based on the inverse system according to claim 1 is characterized in that: The state observer equation expression is as follows: ； In the formula, is the power supply voltage, is the feedback gain matrix, , , are the coefficients of the feedback gain matrix, is the coil inductance, is the displacement of the valve core, is the state vector The estimated value of is the coefficient matrix of the state variables, is the input coefficient matrix, is the output coefficient matrix, For current The estimated value of is the spool speed of the direct drive valve The estimated value of is the valve core displacement The estimated value of .

6. The direct-drive valve proportional reference state feedback control method based on the inverse system according to claim 1 is characterized in that: Inverse system and The inverse system expression is as follows: ； In the formula, is the power supply voltage, is the coil inductance, is the electromagnetic force constant, is the damping coefficient, is the jet angle, is the flow coefficient, is the valve port area gradient, is the length of liquid oil in the working chamber, is the total mass including the electromagnetic linear actuator, valve core, connectors, and springs. is the oil density, is the pressure difference at the valve port, is the coil resistance, is the current in the coil, is the stiffness of the spring, is the acceleration of the valve core movement, is the displacement of the valve core.

7. The direct-drive valve proportional reference state feedback control method based on the inverse system according to claim 1 is characterized in that: The control equation of the state feedback device is as follows: ； In the formula, is the state vector of the pseudo-linear system, is the feedback gain matrix, is the corresponding proportionality coefficient, To control the target, is the coefficient matrix of the state variables of the pseudo-linear system, is the coefficient matrix of the pseudo-linear system input, is the coefficient matrix output by the pseudo-linear system, is the displacement of the valve core.

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