Output feedback control method for pilot-operated electro-hydraulic proportional servo valve considering disturbance suppression

Abstract

Disclosed in the present invention is an output feedback control method for a pilot-operated electro-hydraulic proportional servo valve considering disturbance suppression. According to the control method, a nonlinear active disturbance rejection controller with both disturbance suppression and unknown state estimation is designed on the basis of a constructed disturbance observer in combination with an extended state observer. To address the problem of a valve core position control system of the pilot-operated electro-hydraulic proportional servo valve, the present invention not only ensures suppression of matched interference in the system, but also compensates for mismatched interference in the system, and utilizes a state observer to estimate unmeasurable state variables, so as to construct full-state feedback control, thereby ultimately achieving high-precision tracking control of the valve core position.

Description

Output feedback control method of pilot-operated electro-hydraulic proportional servo valve considering disturbance suppression Technical Field

[0001] The present invention relates to the technical field of electro-hydraulic proportional servo control, and in particular to an output feedback control method of a pilot-operated electro-hydraulic proportional servo valve taking disturbance suppression into consideration. Background Art

[0002] In the electro-hydraulic servo field, pilot-operated electro-hydraulic proportional servo valves are highly regarded in industrial applications due to their high-pressure, high-flow characteristics. Their high output force or torque, high dynamic frequency response, and strong contamination resistance make them an ideal choice for large-scale injection molding equipment and electro-hydraulic lifting systems. However, the main challenges faced by pilot-operated electro-hydraulic proportional servo valves in practical applications are their high nonlinearity and uncertainty. In the pilot stage, nonlinearity primarily stems from hysteresis and saturation effects of the proportional solenoid, as well as friction between the valve spool and sleeve. Furthermore, uncertainty primarily arises from parameter uncertainties of the proportional solenoid and moving components, the oil compressibility, and the clearance between the valve spool and sleeve. For the main valve, the primary nonlinearity is the flow-pressure nonlinearity of the valve body, which significantly impacts system performance, especially under high-pressure, high-flow conditions. Uncertainty stems primarily from parameter uncertainty and external disturbances, such as the effects of steady-state and transient hydraulic forces, and the impact of load pressure changes on the main valve spool.

[0003] As power demands for industrial equipment continue to increase, pilot-operated proportional servo valves are becoming increasingly common in electro-hydraulic servo systems. However, traditional proportional-integral-derivative control strategies and fully analog circuit implementations limit system performance. Furthermore, their functionality is limited, and control performance is easily affected by component parameter drift. Parameter adjustment is inflexible, making subsequent maintenance and secondary development difficult.

[0004] In the digital age, with advances in computer science and technology, pilot-operated proportional servo valve controllers equipped with digital signal processors have become increasingly mainstream. However, while current adaptive control methods can effectively handle system parameter uncertainties, they struggle to handle external disturbances. While sliding mode variable structure control can effectively address system-matched disturbances, it cannot handle unmatched uncertainties. Furthermore, the sign function included in its control input can cause actuator chatter, negatively impacting the entire control system.

[0005] Overall, research on high-performance nonlinear control strategies for pilot-operated electro-hydraulic proportional servo valves is of great significance. Addressing the limitations of existing methods, in-depth research on emerging nonlinear control technologies is crucial for improving the dynamic performance of pilot-operated proportional servo valves and expanding their application range, leveraging the advantages of high-performance digital controllers to better address complex system characteristics.

[0006] Summary of the Invention

[0007] The present invention proposes an output feedback control method for a pilot-operated electro-hydraulic proportional servo valve taking disturbance suppression into consideration. This method can not only ensure real-time estimation of the unknown state of the system and reduce the influence of sensor noise on the control performance, but also actively compensate for the matching and mismatching uncertainty interference in the system, thereby enhancing the robustness of the system and achieving high-precision trajectory tracking control.

[0008] The technical solution for achieving the purpose of the present invention is: a method for output feedback control of a pilot-operated electro-hydraulic proportional servo valve taking disturbance suppression into consideration, comprising the following steps:

[0009] Step 1: Establish a mathematical model of the valve core position control system of the pilot-operated electro-hydraulic proportional servo valve, and then proceed to step 2.

[0010] Step 2: Based on the mathematical model of the valve core position control system of the pilot-operated electro-hydraulic proportional servo valve, design an output feedback controller of the pilot-operated electro-hydraulic proportional servo valve considering disturbance suppression, and then proceed to step 3.

[0011] Step 3: Use Lyapunov stability theory to prove the stability of the nonlinear valve core position controller and obtain the result that the system tracking error and observation error are bounded.

[0012] Compared with the existing technology, the present invention has the following significant advantages: (1) it only requires the valve core position information to be known, and other unknown or unmeasurable states are obtained by the state observer, which reduces the impact of measurement noise on control accuracy; (2) it can actively compensate for the matching disturbance terms and mismatching disturbance terms in the system, enhance the robustness of the system, and improve the tracking performance of the system. The simulation results verify its effectiveness. BRIEF DESCRIPTION OF THE DRAWINGS

[0013] FIG1 is a schematic diagram showing the principle of the output feedback control method of the pilot-operated electro-hydraulic proportional servo valve taking disturbance suppression into consideration according to the present invention.

[0014] FIG2 is a schematic diagram showing the principle of the pilot-operated electro-hydraulic proportional servo valve according to the present invention.

[0015] FIG3 is a graph showing the desired command signal of the system to be tracked by the nonlinear controller designed in the present invention.

[0016] FIG4 is a graph showing the tracking error of the system changing with time under the action of the nonlinear controller designed by the present invention.

[0017] FIG5 is a comparison curve diagram of the tracking errors of the system under the action of the nonlinear controller designed by the present invention and the traditional PID controller.

[0018] FIG6 is a control input curve diagram of the system under the action of the nonlinear controller designed by the present invention. DETAILED DESCRIPTION

[0019] The present invention will be further described in detail below with reference to the accompanying drawings and specific embodiments.

[0020] 1 and 2 , the output feedback control method of a pilot-operated electro-hydraulic proportional servo valve considering disturbance suppression of the present invention includes the following steps:

[0021] Step 1: Establish a mathematical model of the valve core position control system of the pilot-operated electro-hydraulic proportional servo valve.

[0022] Step 1-1. The pilot-operated electro-hydraulic proportional servo valve is applied to large-scale industrial heavy-duty mechanical equipment, and includes a pilot-stage proportional servo valve and a main valve. The pilot-stage proportional servo valve controls the pressure difference between the two chambers of the main valve core, thereby driving the movement of the main valve core. The flow rate of the pilot valve is generally much smaller than that of the main valve, and its frequency response is also much higher than that of the main valve. Therefore, the valve core dynamics of the pilot-stage proportional servo valve can be simplified to a proportional link.

[0023] According to Newton's second law, the force balance equation of the main valve core movement of the pilot-operated proportional servo valve is:

[0024] In formula (1), m represents the mass of the main valve core, x represents the displacement of the main valve core, The speed of the main valve core, Indicates the acceleration of the main valve core, A indicates the effective area at both ends of the main valve core, P a and P b They represent the pressures in the two control chambers between the main valve and the pilot valve (defined as the oil inlet control chamber and the oil outlet control chamber, respectively), B represents the viscous damping coefficient of the main valve movement, k represents the spring coefficient of the main valve centering spring, and d represents the unmodeled mechanical interference of the system.

[0025] Then formula (1) can be rewritten as:

[0026] In the valve core control system of the pilot-operated electro-hydraulic proportional servo valve, ignoring the leakage of the control chamber oil in the pilot stage, the pressure dynamic equation is:

[0027] Formula (3), β e Indicates the elastic modulus of hydraulic oil, Ct The leakage coefficient between the control chamber and the main valve core, the volume of the oil inlet control chamber V a =V 0a +Ax, oil outlet control chamber volume V b =V 0b -Ax, V 0a Indicates the initial volume of the oil inlet control chamber, V 0b Indicates the initial volume of the oil control chamber, Q a Indicates the flow rate into the control chamber, Q b represents the flow rate out of the control chamber, q a Indicates P a The unmodeled disturbance, q b Indicates P b The unmodeled disturbance, Indicates P a The first derivative of Indicates P b The first derivative of .

[0028] Q a , Q b Respectively with the valve core displacement x of the pilot stage proportional servo valve v There are the following relationships:

[0029] Among them, the valve coefficient of the pilot-stage proportional servo valve is C d represents the flow coefficient of the pilot-stage proportional servo valve, w0 represents the valve core area gradient of the pilot-stage proportional servo valve, ρ represents the oil density, P s Indicates the oil supply pressure, P r represents the return oil pressure, s(·) represents the function of the variable ·, and is defined as:

[0030] Ignoring the valve core dynamics of the pilot stage proportional servo valve, assuming that the control input u acting on the valve core and the valve core displacement x v Proportional relationship, that is, x v =k i u, where k i represents the voltage and valve core displacement gain coefficient, so Equation (4) is rewritten as:

[0031] Formula (6), intermediate variable k u =k q k i , intermediate variables Intermediate variables

[0032] Step 1-2, define system state variables: Then transform Equation (2) into the state space equation:

[0033] Formula (7), represents the first-order derivative of state x1, represents the first-order derivative of state x2, Represents the first-order derivative of state x3, intermediate variable Intermediate variables Mismatched disturbance terms Intermediate variables Matched perturbation terms

[0034] To facilitate the design of the controller and observer, the following assumptions are made:

[0035] Assumption 1: The system expects the position command x d It is second-order continuous, and the position command, velocity command, and acceleration command expected by the system are all bounded.

[0036] Assumption 2: D1 and D2 satisfy:

[0037] In formula (8), σ1, σ2, π1 and π2 are all unknown constants greater than zero; represents the derivative of D1, represents the derivative of D2.

[0038] Go to step 2.

[0039] Step 2: Based on the mathematical model of the valve core position control system of the pilot-operated electro-hydraulic proportional servo valve, design an output feedback controller that takes disturbance suppression into consideration. The specific steps are as follows:

[0040] Step 2-1: To compensate for the interference term of the valve core displacement control matching of the pilot-operated electro-hydraulic proportional servo valve and estimate the remaining unmeasurable state quantities except the main valve core displacement, a state expansion system with the following form is constructed:

[0041] In formula (9), the intermediate variable x4 represents the matching disturbance term D2, and the intermediate variable represents the rate of change of the matching disturbance term, and t represents time;

[0042] In order to estimate the unknown system state and external disturbance, an extended state observer of the following form is designed:

[0043] Formula (10), Represents the state x i Estimates, Express Estimates of where i = 1, 2, 3, 4, gain ω o is the bandwidth of the observer, a positive number, Represents the estimate of g, because the parameter g is related to the state variable x3, so Denotes the estimate of the mismatch disturbance term D1.

[0044] Subtracting Equation (10) from Equation (9) yields the observation error of the extended state observer:

[0045] in represents the estimation error of D1, represents the estimation error of g.

[0046] Define the scaling error variable Then formula (11) can be written as:

[0047] Formula (12), matrix matrix matrix matrix The matrix A is a Hurwitz matrix, so there exists a positive definite matrix P that satisfies the following Lyapunov equation: T P+PA=-2I (13);

[0048] I represents the identity matrix.

[0049] Step 2-2: To estimate the disturbance term of the system mismatch, design the following form of disturbance observer. First, define the auxiliary variable z as: z = D1-γ1x2 (14),

[0050] Formula (14), γ1 is a positive gain constant, and the differential of z can be obtained

[0051] Then the estimate of the auxiliary variable z Designed to:

[0052] in, Express The estimate of the mismatch disturbance term D1 is:

[0053] Define the estimation error of the auxiliary variable z as Combining equations (14) and (17), we can obtain:

[0054] Taking the derivative of formula (18) we can get The derivative of

[0055] Step 2-3: To facilitate controller design, define the tracking error of the system as e1 = x1 - x d , x d Indicates the command signal expected by the system.

[0056] Taking the derivative of e1, we can get:

[0057] Represents x d The first derivative of .

[0058] Design the virtual control law α1 as:

[0059] Formula (21), gain k1>0. Define the deviation between the virtual control law α1 and x2 as e2=x2-α1, and substitute formula (21) into formula (20) to obtain

[0060] Step 2-4, take the derivative of e2 and get

[0061] in Represents x d The second derivative of .

[0062] The deviation between the virtual control law α2 and x3 is defined as e3 = x3 - α2, then Equation (23) can be rewritten as:

[0063] Design the virtual control law α2 as:

[0064] where α 2a is the model feedforward term, α 2s is the robust feedback term, k2>0. Substituting equation (25) into equation (24) yields:

[0065] Step 2-5, take the derivative of e3 and get

[0066] Formula (27), represents the first-order derivative of α2, is the computable part of the derivative of α2, is the uncomputable part of the derivative of α2, and the control input u of the system can be designed as

[0067] Where, the gain k3>0. Substituting equation (28) into equation (27) yields

[0068] Go to step 3.

[0069] Step 3: Use Lyapunov stability theory to prove the stability of the observer and controller, and obtain the results that the system observation error and tracking error are bounded, as follows:

[0070] The Lyapunov function is defined as follows:

[0071] Taking the derivative of formula (30) and combining formula (12), formula (13), formula (19), formula (22), formula (26) and formula (29) we can obtain:

[0072] Where ||·|| represents the binorm of ·. According to formula (18), we can get: Substituting it into formula (31) we can get

[0073] According to the definition of the intermediate variable g, there exists a constant c such that

[0074] To simplify the representation, the following set of constants are defined:

[0075] Combining Equation (34) and using Young's inequality, Equation (32) can be written as:

[0076] Formula (35), the intermediate definitions are as follows:

[0077] In formula (36), the intermediate variables Λ1, Λ2, Λ3, Λ4, and Λ5 are defined as:

[0078] By adjusting the gains k1, k2, k3, ω o and γ1, the symmetric matrix Λ can be made a positive definite matrix. Applying the comparison lemma, we can obtain:

[0079] Formula (38), τ = 2λ min (Λ)min{1,1 / λ max (P)} is the exponential convergence rate, λ min (·) and λ max (·) are the maximum and minimum eigenvalues ​​of the matrix respectively. Therefore, the observation error ε, And the tracking errors e1, e2, e3 are bounded, which means that the state x and its estimate are bounded, and the disturbance estimate and There are also boundaries.

[0080] Therefore, it is concluded that by adjusting the gains k1, k2, k3, ω O and γ1, the output feedback controller of the pilot-operated electro-hydraulic proportional servo valve considering disturbance rejection designed for the valve core position control system of the pilot-operated proportional servo valve can make the system tracking error and observation error bounded.

[0081] Example

[0082] To verify the performance of the designed controller, the physical parameters of the valve core position control system of the pilot-operated electro-hydraulic proportional servo valve in the simulation are shown in Table 1:

[0083] Table 1 System physical parameters

[0084] The expected instructions for a given system are

[0085] The following controllers are used for comparison in the simulation:

[0086] Output feedback controller (DROF) for pilot-operated electro-hydraulic proportional servo valve considering disturbance rejection: Setting observer gain ω o =200, γ1 = 170. The controller gains are k1 = 10, k2 = 2, k3 = 2.

[0087] PID controller: The parameter adjustment method of the PID controller is: first ignore the nonlinear dynamics of the valve core position control system of the pilot-operated electro-hydraulic proportional servo valve, set a set of PID parameters at random, and then use the parameter self-tuning function in Matlab-Simulink to adjust a set of appropriate control parameters. Then, superimpose the nonlinear dynamics on the basis of the original linear system, and use the trial and error method to manually fine-tune the controller parameters to minimize the tracking error of the system. The final adjusted PID controller parameter value is k P =10,k I =0.02, k D =0.005.

[0088] Figure 1 is a schematic diagram of the principle of the output feedback control method for the pilot-operated electro-hydraulic proportional servo valve designed in accordance with the present invention, which takes disturbance suppression into consideration. Figure 2 is a diagram of the working principle of the pilot-operated electro-hydraulic proportional servo valve. Figure 3 shows the command signal applied to the system. Figure 4 shows the tracking error of the DROF controller. Figure 5 shows a comparison of the steady-state tracking error between the DROF controller and the PID controller. Figure 6 shows the time-varying curve of the control input of the system. As can be seen from Figure 4, the pilot-operated electro-hydraulic proportional servo valve achieves excellent tracking performance under the action of the DROF controller, with the amplitude of its steady-state tracking error being approximately 0.0045 mm and the control accuracy reaching 0.45%. Combined with Figure 5, it can be seen that the tracking accuracy of the DROF controller proposed in the present invention is 8 times higher than that of the PID controller. As can be seen from Figure 6, the control input of the system remains smooth throughout, without large mutations or jumps, which is very beneficial for practical applications.

Claims

1. A method for output feedback control of a pilot-operated electro-hydraulic proportional servo valve taking disturbance suppression into consideration, characterized in that: The following steps are involved: Step 1: Establish a mathematical model of the valve core position control system of the pilot-operated electro-hydraulic proportional servo valve, and then proceed to step 2; Step 2: Based on the mathematical model of the valve core position control system of the pilot-operated electro-hydraulic proportional servo valve, design an output feedback controller of the pilot-operated electro-hydraulic proportional servo valve that takes disturbance suppression into consideration, and then proceed to step 3. Step 3: Use Lyapunov stability theory to prove the stability of the nonlinear valve core position controller and obtain the result that the system tracking error and observation error are bounded.

2. The output feedback control method of a pilot-operated electro-hydraulic proportional servo valve considering disturbance suppression according to claim 1, characterized in that: In step 1, a mathematical model of the valve core position control system of the pilot-operated electro-hydraulic proportional servo valve is established as follows: Step 1-1: Simplify the valve core dynamics of the pilot-stage proportional servo valve into a proportional link, and obtain a mathematical model of the valve core position control system of the pilot-type proportional servo valve based on the dynamic characteristics of the pilot valve and the main valve; Step 1-2: To facilitate the design of nonlinear algorithms, define the state variables of the system and convert the mathematical model of the valve core position control system of the pilot-operated electro-hydraulic proportional servo valve into the form of a state space equation.

3. The output feedback control method of a pilot-operated electro-hydraulic proportional servo valve considering disturbance suppression according to claim 2, characterized in that: In step 1-1, the valve core dynamics of the pilot-stage proportional servo valve can be simplified to a proportional link. Based on the dynamic characteristics of the pilot valve and the main valve, the mathematical model of the valve core position control system of the pilot-operated proportional servo valve is derived as follows: According to Newton's second law, the force balance equation of the main valve core movement of the pilot-operated proportional servo valve is: In formula (1), m represents the mass of the main valve core, x represents the displacement of the main valve core, The speed of the main valve core, Indicates the acceleration of the main valve core, A indicates the effective area at both ends of the main valve core, P a Indicates the pressure of the oil inlet control chamber between the main valve and the pilot valve, P b represents the pressure of the oil outlet control chamber between the main valve and the pilot valve, B represents the viscous damping coefficient of the main valve movement, k represents the spring coefficient of the main valve centering spring, and d represents the unmodeled mechanical interference of the system; Rewrite formula (1) as: In the valve core position control system of the pilot-operated electro-hydraulic proportional servo valve, ignoring the leakage of the control chamber oil in the pilot stage, the pressure dynamic equation is: In formula (3), β e Indicates the elastic modulus of hydraulic oil, C t The leakage coefficient between the control chamber and the main valve core, the volume of the oil inlet control chamber V a =V 0a +Ax, oil outlet control chamber volume V b =V 0b -Ax, V 0a Indicates the initial volume of the oil inlet control chamber, V 0b Indicates the initial volume of the oil control chamber, Q a Indicates the flow rate into the control chamber, Q b represents the flow rate out of the control chamber, q a Indicates P a The unmodeled disturbance, q b Indicates P b The unmodeled disturbance, represents the first-order derivative of Pa, represents the first-order derivative of Pb; Q a , Q b Respectively with the valve core displacement x of the pilot stage proportional servo valve v There are the following relationships: Among them, the valve coefficient of the pilot-stage proportional servo valve is C d represents the flow coefficient of the pilot-stage proportional servo valve, w0 represents the valve core area gradient of the pilot-stage proportional servo valve, x v represents the valve core displacement, ρ represents the oil density, P s Indicates the oil supply pressure, P r represents the return oil pressure, s(·) represents the function of the variable ·, and is defined as: Ignoring the valve core dynamics of the pilot stage proportional servo valve, assuming that the control input u acting on the valve core and the valve core displacement x v Proportional relationship, that is, satisfying x v =k i u, where k i represents the gain coefficient of voltage and valve core displacement, so equation (4) is rewritten as: Formula (6), intermediate variable k u =k q k i , intermediate variables Intermediate variables 4. The output feedback control method of a pilot-operated electro-hydraulic proportional servo valve considering disturbance suppression according to claim 3, characterized in that: Step 1-2: To facilitate the design of the nonlinear algorithm, define the state variables of the system and convert the derived mathematical model of the pilot-operated electro-hydraulic proportional servo valve main valve core position control system into the form of state space equations, as follows: Define state variables: Then transform Equation (2) into the state space equation: Formula (7), represents the first-order derivative of the state variable x1, represents the first-order derivative of the state variable x2, Represents the first-order derivative of the state variable x3, the intermediate variable Intermediate variables Mismatched disturbance terms Intermediate variables Matched perturbation terms The superscript T indicates transposition; To facilitate the design of the controller and observer, the following assumptions are made: Assumption 1: The system expects the position command x d It is second-order continuous, and the position command, velocity command, and acceleration command expected by the system are all bounded; Assumption 2: D1 and D2 satisfy: In formula (8), σ1, σ2, π1 and π2 are all unknown constants greater than zero, and |·| is the absolute value symbol. represents the first derivative of D1; represents the first derivative of D2; Go to step 2.

5. The output feedback control method of a pilot-operated electro-hydraulic proportional servo valve considering disturbance suppression according to claim 4, characterized in that: In step 2, based on the mathematical model of the valve core position control system of the pilot-operated electro-hydraulic proportional servo valve, an output feedback controller of the pilot-operated electro-hydraulic proportional servo valve with consideration of disturbance suppression is designed, as follows: Step 2-1: To compensate for the interference term that matches the valve core displacement control of the pilot-operated electro-hydraulic proportional servo valve and estimate the remaining unmeasurable state quantities other than the main valve core displacement, an extended state observer is constructed, and a separate disturbance observer is designed to estimate the mismatched disturbance term D1. Step 2-2: Define the tracking error of the system as e1 = x1 - x d , x d Indicates the command signal expected by the system. In order to achieve control of the main valve core, the control input u of the system should be designed so that the tracking error e1 of the system should be as small as possible; Step 2-3: Define the deviation between the virtual control law α1 and x2 as e2 = x2 - α1. To ensure that e1 tends to 0, it is necessary to ensure that the error e2 also tends to 0. Step 2-4: Define the deviation between the virtual control law α2 and x3 as e3 = x3 - α2. In order to ensure that e2 tends to 0, it is necessary to ensure that the error e3 also tends to 0.

6. The output feedback control method of a pilot-operated electro-hydraulic proportional servo valve considering disturbance suppression according to claim 5, characterized in that: Step 2-1: To compensate for the interference term of the valve core displacement control matching of the pilot-operated electro-hydraulic proportional servo valve and estimate the remaining unmeasurable state quantities except the main valve core displacement, a state expansion system with the following form is constructed: In formula (9), x4 represents the matching disturbance term D2, represents the rate of change of the matching disturbance term, and t represents time; In order to estimate the unknown system state and external disturbance, an extended state observer of the following form is designed: Formula (10), Represents the state x i Estimates, Express Estimates of, subscript i=1,2,3,4; ω o is the bandwidth of the observer, which is a positive number; Represents the estimate of g, because g is related to the state variable x3, so represents the estimate of the mismatch disturbance term D1; The state observation error is defined as Derivative of the observation error Subtracting Equation (10) from Equation (9) yields the observation error of the extended state observer: in represents the estimation error of D1, represents the estimation error of g. Define the error variable for scaling Then formula (11) can be written as: in, represents the first derivative of ε; Formula (12), matrix matrix matrix matrix The matrix A is a Hurwitz matrix, so there exists a positive definite matrix P that satisfies the following Lyapunov equation: A T P+PA=-2I (13), I represents the identity matrix; In order to estimate the disturbance term of the system mismatch, a disturbance observer of the following form is designed. First, the auxiliary variable z is defined as: z=D1-γ1x2 (14), In formula (14), γ1 is a positive gain constant; taking the derivative with respect to z, we get Then the estimate of the auxiliary variable z is Designed for in express estimated value of; Estimation of the mismatch disturbance term D1 for: Define the estimation error of the auxiliary variable z as Combining equations (14) and (17), we can get: in represents the estimation error of D1; Taking the derivative of formula (18) we can get 7. The output feedback control method of a pilot-operated electro-hydraulic proportional servo valve considering disturbance suppression according to claim 6, characterized in that: In step 2-2, the tracking error of the system is defined as e1 = x1-x d In order to achieve control of the main valve core, the control input u should be designed so that the tracking error e1 of the system should be as small as possible, as follows: Taking the derivative of e1, we get in is x d The first-order derivative of , the designed virtual control α1 is: Formula (21), gain k1>0, define the deviation between the virtual control law α1 and the state x2 as e2=x2-α1, substitute formula (21) into formula (20) to obtain 8. The output feedback control method of a pilot-operated electro-hydraulic proportional servo valve considering disturbance suppression according to claim 7, characterized in that: In step 2-3, in order to ensure that the error e1 tends to 0, it is necessary to ensure that the error e2 also tends to 0. The derivative of e2 is in, Represents x d The second derivative of The deviation between the virtual control law α2 and the state x3 is defined as e3 = x3 - α2, then Equation (23) can be rewritten as: Design the virtual control law α2 as: Among them, α 2a is the model feedforward term, α 2s is the robust feedback term. Gain k2>0, substituting equation (25) into equation (24) yields:

9. The output feedback control method of a pilot-operated electro-hydraulic proportional servo valve considering disturbance suppression according to claim 8, characterized in that: In steps 2-4, in order to ensure that the error e2 tends to 0, it is necessary to ensure that the error e3 also tends to 0. The derivative of e3 is Formula (27), represents the first-order derivative of α2, represents the computable part of the derivative of α2, Represents the uncomputable part of the derivative of α2, and the control input u of the system is designed as: Where, the gain k3>0, and substituting equation (28) into equation (27) yields Go to step 3.

10. The output feedback control method of a pilot-operated electro-hydraulic proportional servo valve considering disturbance suppression according to claim 9, characterized in that: The stability of the observer and controller is proved by using Lyapunov stability theory as described in step 3, and the results show that the system observation error and tracking error are bounded, as follows: The Lyapunov function V is defined as follows: Formula (30), error matrix e = [e1, e2, e3] T , Lyapunov stability theory is used to prove the stability, and the results show that the system observation error and tracking error are bounded.

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