Distributed cooperative control method of multiple electro-hydraulic servo systems based on feedback linearization

Abstract

The present invention discloses a distributed cooperative control method for multiple electro-hydraulic servo systems based on feedback linearization, which is applied to the field of hydraulic control and aims to solve the problem that the prior art lacks consideration of the synchronous control of distributed electro-hydraulic servo actuators under the condition of communication delay. The present invention establishes affine nonlinear models of multiple electro-hydraulic servo actuators and performs linearization processing to obtain feedback data of the electro-hydraulic servo system in real time, designs a distributed consistency protocol, uses a disturbance observer to estimate the unknown external load interference of the system, calculates the linear matrix inequality (LMI) conditions for system stability, and drives the electro-hydraulic servo mechanism in real time according to the distributed consistency control law. The distributed consistency cooperative control of multiple electro-hydraulic servo actuators is realized, and the tracking and coordination capabilities of multiple electro-hydraulic servo systems are improved.

Description

Technical Field

[0001] The invention belongs to the field of hydraulic control, and in particular relates to a coordinated control technology of multiple asymmetric hydraulic cylinder actuators. Background Art

[0002] Electro-hydraulic servo actuators are often widely used in large-scale load scenarios in the engineering field due to their advantage of high output power. The control core of the electro-hydraulic servo actuator is the servo valve, and the entire hydraulic control system is mainly composed of electrical devices and hydraulic mechanisms. The main working principle is: the sensor on the actuator collects information such as displacement, speed, and hydraulic cylinder pressure difference, and obtains an error signal by comparing the element with the expected instruction, which is input to the controller through the A\D conversion device. The controller calculates the rated output voltage signal based on the error signal through the designed algorithm, and then inputs it to the servo valve through the A\D conversion device and the amplifier. The servo valve achieves the goal of driving the actuator to move by changing the pressure and flow in the hydraulic cylinder according to the input signal. By continuously controlling the flow and pressure of the servo valve according to the error signal, the system error is gradually reduced, and finally the actuator moves according to the instruction of the desired trajectory.

[0003] In engineering, the demand for large loads is increasing, and the distributed collaborative control of multiple electro-hydraulic servo actuators can complete more complex and larger tasks. In practice, due to the limitations of hardware equipment, the communication between the controllers of each electro-hydraulic servo actuator often contains a certain delay. Previous studies have mainly focused on the synchronous control of multiple electro-hydraulic servo actuators with load or parameter uncertainty, but lacked research on the synchronous control of distributed electro-hydraulic servo actuators considering communication delay. Summary of the invention

[0004] In order to solve the above technical problems, the present invention proposes a distributed collaborative control method for multiple electro-hydraulic servo actuators under communication delay, which realizes the collaborative control of multiple electro-hydraulic servo actuators with unknown external load interference under communication delay and improves the synchronization tracking performance of the distributed electro-hydraulic servo control system.

[0005] The technical solution adopted by the present invention is: a distributed cooperative control method of multiple electro-hydraulic servo actuators under communication delay, comprising:

[0006] S1. Establish a nonlinear model of a multi-node distributed electro-hydraulic servo actuator and perform linearization processing to obtain a linear model;

[0007] S2, driving the electro-hydraulic servo system and collecting feedback data of the electro-hydraulic servo system in real time;

[0008] S3, using a disturbance observer to estimate the unknown external load disturbance of the electro-hydraulic servo system according to the feedback data collected in step S2;

[0009] S4, according to the unknown external load disturbance of the electro-hydraulic servo system estimated in step S3 and the linear model of step S1, design a distributed consistency protocol for multiple electro-hydraulic servo actuators based on neighborhood information and disturbance compensation under communication delay;

[0010] S5. Based on the Lyapunov energy function, and combined with the distributed consensus protocol, feedback data, consistency error and disturbance estimation, the LMI condition for system stability is obtained;

[0011] S6. The three-node distributed electro-hydraulic servo mechanism is driven in real time according to the distributed consistency control law under the LMI condition of system stability.

[0012] The beneficial effects of the present invention are as follows: the present invention designs a distributed consistency protocol based on neighborhood information under communication delay, establishes a disturbance observer to estimate unknown load interference, realizes distributed consistency collaborative control of multiple electro-hydraulic servo actuators, and improves the synchronous tracking performance of the distributed electro-hydraulic servo system. BRIEF DESCRIPTION OF THE DRAWINGS

[0013] Figure 1 It is a flow chart of a method for coordinated control of distributed electro-hydraulic servo actuators in the presence of load disturbance under communication delay of the present invention;

[0014] Figure 2 It is a physical picture of a three-node distributed electro-hydraulic servo mechanism in an embodiment of the present invention. DETAILED DESCRIPTION

[0015] In order to make the purpose, technical solution and advantages of the present invention more clearly understood, the present invention is further described in detail below in conjunction with the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are only used to explain the present invention and are not used to limit the present invention.

[0016] like Figure 1 As shown, it is a flow chart of the distributed cooperative control method of multiple electro-hydraulic servo actuators in the presence of load interference of the present invention; it includes the following steps:

[0017] S1. Establish a nonlinear model of a multi-node distributed electro-hydraulic servo actuator and perform linearization processing to obtain a linear model;

[0018] S2, driving the electro-hydraulic servo system and collecting feedback data of the electro-hydraulic servo system in real time;

[0019] S3, using a disturbance observer to estimate the unknown external load disturbance of the electro-hydraulic servo system according to the feedback data collected in step S2;

[0020] S4, according to the unknown external load disturbance of the electro-hydraulic servo system estimated in step S3 and the linear model of step S1, design a distributed consistency protocol for multiple electro-hydraulic servo actuators based on neighborhood information and disturbance compensation under communication delay;

[0021] S5. Based on the Lyapunov energy function, and combined with the distributed consistency protocol, feedback data, consistency error and disturbance estimation value, the LMI condition for system stability is obtained;

[0022] S6. The three-node distributed electro-hydraulic servo mechanism is driven in real time according to the distributed consistency control law under the LMI condition of system stability.

[0023] like Figure 2 As shown, the present invention takes the distributed collaborative control of three-node distributed electro-hydraulic servo actuators in the presence of unknown load interference under communication delay as an example, and further explains in detail the distributed collaborative control method of multiple electro-hydraulic servo actuators in the presence of load interference of the present invention.

[0024] The above-mentioned three-node distributed electro-hydraulic servo actuator includes: 3 hydraulic actuators, including: 3 hydraulic cylinders and 3 load metal blocks, 3 electro-hydraulic servo valves, 1 hydraulic pump, and 3 lower computers responsible for calculation; the 3 electro-hydraulic servo valves drive the corresponding hydraulic cylinders to move according to the hydraulic oil flow and pressure; displacement sensors are set on the 3 hydraulic cylinders to measure the displacement and speed of the hydraulic cylinders; a pressure sensor is set at the oil inlet and outlet of the 3 hydraulic cylinders to measure the load force of the hydraulic cylinders; the hydraulic pump is responsible for outputting hydraulic oil to supply power; the 3 load metal blocks act on the hydraulic cylinders as external load disturbances in the model.

[0025] In an optional embodiment of the present invention, the above step S1 uses a third-order model to describe the electro-hydraulic servo actuator model of the servo valve driving the hydraulic cylinder circuit, and the i-th electro-hydraulic servo actuator nonlinear model established is expressed as:

[0026]

[0027] The symbols in the formula have the following meanings:

[0028] x i1 (t) is the displacement of the hydraulic cylinder at the i-th node, x i2 (t) is the hydraulic cylinder speed of the i-th node, x i3 (t) is the load pressure of the i-th node; They are x i1 (t), x i2 (t), x i3 The differential of (t); F Li (t) is the load pressure of the hydraulic cylinder at the i-th node; A p is the cross-sectional area of ​​the hydraulic cylinder; yi (t) is the displacement of the ith node; m is the mass of the load block; C tl is the total leakage coefficient; p s is the oil supply pressure; β e is the bulk elastic modulus of oil; C d is the valve flow coefficient; w is the valve area gradient; ρ is the oil density; K is the load stiffness coefficient; b is the oil damping coefficient; K sv is the amplification factor; V t is the total volume; u i (t) is the output voltage of the ith node; sgn(·) is the sign function.

[0029] The affine nonlinear model of the i-th electro-hydraulic servo actuator is expressed as: i (t) = [x i1 ,x i2 ,x i3 ] T , x i (t) is a 3D vector, which is x i1 (t), x i2 (t), x i3 (t) integration;

[0030]

[0031] y i (t) = h i (x,t)

[0032] in, is x i The differential of (t), D Li (t) = [0 d Li (t) 0] T , d Li (t)=-F Li (t) / m,h i (x,t)=x i1 (t), θ 1 =K / m,θ 2 =b / m,θ 3 =1 / m, θ 5 =4β e C tl / V t ,

[0033] The linear model is obtained by linearizing the affine nonlinear models of multiple electro-hydraulic servo actuators, specifically:

[0034] Using the state variable zi (t) Linear transformation

[0035] z i (t) = [x i1 (t) x i2 (t) -θ 1 x i1 (t)-θ 2 x i2 (t)+θ 3 x i3 (t)] T

[0036] and feedback control variable u i (t)

[0037] u i (t) = α i (x,t)+β i (x,t)γ i (t)

[0038] in,

[0039] γ i (t) is the new control input.

[0040] The linear system model is obtained as:

[0041]

[0042] y i (t) = C 1 z i (t)

[0043] in, B 1 =[0,0,1] T , C 1 =[1 0 0], D Li (t)=[0,d Li (t),θ 2 d Li (t)] T .

[0044] To ensure the stability of the obtained linear system, the poles of the linear system are configured, and γ i (t) = K p z i (t)+v i (t), the linear model of the affine nonlinear model of the electro-hydraulic servo actuator is obtained, which is expressed as:

[0045]

[0046] y(t)=Cz(t)

[0047] Among them, A=A 1 +B 1 K p , B=B 1 , C=C 1 ;

[0048] In an optional embodiment of the present invention, the above step S2 drives the electro-hydraulic servo mechanism to obtain feedback data of the electro-hydraulic servo mechanism in real time, including: hydraulic cylinder output displacement, hydraulic cylinder speed, pressure of chambers on both sides of the hydraulic cylinder, and servo valve core displacement.

[0049] In an optional embodiment of the present invention, the above step S3 uses a disturbance observer to estimate the unknown external load disturbance of the system, which is expressed as:

[0050] in: The interference estimate The derivative of Represents the Kronecker product, which can perform vector combination augmentation on multiple scalars;

[0051]

[0052] Among them, e i (t) = z i (t)-z 0 (t), e i (t) represents the state error between the ith node and the 0th node (leader node), z 0 (t) represents the state of the 0th node (leader node), λ L is a positive number, P is a positive definite symmetric matrix, Y is a diagonal matrix, μ=diag{μ 1 ,μ 2 ,...μ n} is the diagonal μ i The diagonal gain matrix of . Represents the vector form of the disturbance observer. represents the estimated value of the i-th external load interference.

[0053] In an optional embodiment of the present invention, the distributed consistency protocol designed in step S4 for multiple electro-hydraulic servo actuators based on neighborhood information and disturbance compensation under communication delay is expressed as:

[0054]

[0055] Among them, v i (t) is the control law of the ith node, K is the gain vector, zi (t),z j (t) are the states of the i-th and j-th nodes respectively, a ij The i-th and j-th nodes transmit information to each other, and d represents the communication delay;

[0056] The consistency protocol vector form of n systems is expressed as:

[0057]

[0058] Where v(t)=[v 1 (t),…,v n (t)] T , the superscript T represents the transpose, H = L + B, which is the sum of the Laplacian matrix of n nodes and the leader matrix.

[0059] In an optional embodiment of the present invention, the above step S5 is based on the Lyapunov candidate function, and combines the distributed consistency protocol, feedback data, consistency error and disturbance estimation value to obtain the LMI (linear matrix inequality) condition for system stability, which is specifically:

[0060] Set the Lyapunov energy function, expressed as

[0061]

[0062] Among them, I n is the n-order identity matrix, is the disturbance estimation error;

[0063] Combining the distributed consensus protocol, feedback data, consistency error and disturbance estimate, the LMI condition for system stability is expressed as

[0064]

[0065] Among them, P and Q are positive definite symmetric matrices, and α is a positive number.

[0066] According to the LMI condition of system stability, the positive definite symmetric matrix P is solved and substituted into the consistency protocol vector and disturbance observer model, thus completing the design of distributed consistency protocol and disturbance observer for system stability.

[0067] Aiming at the problem of distributed collaborative control of multiple electro-hydraulic servo actuators under communication delay, the present invention adopts a method combining a distributed consistency protocol under communication delay and a disturbance observer to improve the distributed synchronous control tracking performance of three-node distributed electro-hydraulic servo actuators under the condition of unknown external load interference.

[0068] The present invention first transforms the affine nonlinear model of the electro-hydraulic servo actuator into a linear model by linearizing the input-output feedback. The unknown external load in the model is estimated by a disturbance observer. Then, a distributed consistency protocol is designed based on the neighborhood information under communication delay. At the same time, the Lyapunov energy function and the Lyapunov-Krasovskii function are designed based on the state error and the observer estimation error. The LMI condition for system stability is obtained to complete the design of the distributed consistency protocol and the disturbance observer. The three electro-hydraulic servo actuators drive the load metal blocks respectively. In the distributed cooperative control law v i (t), the coordinated control of three-node distributed electro-hydraulic servo actuators is realized, which improves the coordinated control performance of the node distributed electro-hydraulic servo actuator motion.

[0069] Those skilled in the art will appreciate that the embodiments described herein are intended to help readers understand the principles of the present invention, and should be understood that the scope of protection of the present invention is not limited to such specific statements and embodiments. For those skilled in the art, the present invention may have various changes and variations. Any modifications, equivalent substitutions, improvements, etc. made within the spirit and principles of the present invention should be included in the scope of the claims of the present invention.

Claims

1. A distributed cooperative control method for multiple electro-hydraulic servo actuators under communication delay, characterized in that: The electro-hydraulic servo system based on the invention specifically includes a multi-node distributed electro-hydraulic servo actuator; the control method includes: S1. Establish a nonlinear model of a multi-node distributed electro-hydraulic servo actuator and perform linearization processing to obtain a linear model; S2, driving the electro-hydraulic servo system and collecting feedback data of the electro-hydraulic servo system in real time; S3, using a disturbance observer to estimate the unknown external load disturbance of the electro-hydraulic servo system according to the feedback data collected in step S2; S4. According to the unknown external load disturbance of the electro-hydraulic servo system estimated in step S3 and the linear model of step S1, a distributed consistency protocol of multiple electro-hydraulic servo actuators based on neighborhood information and disturbance compensation under communication delay is designed; Step S4 designs a distributed consistency protocol of multiple electro-hydraulic servo actuators based on neighborhood information and disturbance compensation under communication delay as follows: Among them, v i (t) is the control law of the ith node, K is the gain vector, z i (t),z j (t) are the states of the i-th and j-th nodes respectively, a ij The i-th and j-th nodes transmit information to each other, and d represents the communication delay; The consistency protocol vector form of n systems is expressed as: where v(t)=[v1(t),…,v n (t)] T , H is the sum of the Laplacian matrix of n nodes and the leader matrix; S5. Based on the Lyapunov energy function, and combined with the distributed consistency protocol, feedback data, consistency error and disturbance estimation value, the LMI condition for system stability is obtained; S6. The three-node distributed electro-hydraulic servo mechanism is driven in real time according to the distributed consistency control law under the LMI condition of system stability.

2. The distributed cooperative control method of multiple electro-hydraulic servo actuators under communication delay according to claim 1 is characterized in that: The nonlinear model corresponding to each distributed electro-hydraulic server in step S1 is expressed as: In, x i1 (t) is the displacement of the hydraulic cylinder at the i-th node, x i2 (t) is the hydraulic cylinder speed of the i-th node, x i3 (t) is the load pressure of the i-th node; They are x i1 (t), x i2 (t), x i3 The differential of (t); F Li (t) is the load pressure of the hydraulic cylinder at the i-th node; A p is the cross-sectional area of ​​the hydraulic cylinder; y i (t) is the displacement of the ith node; m is the mass of the load block; C tl is the total leakage coefficient; p s is the oil supply pressure; β e is the bulk elastic modulus of oil; C d is the valve flow coefficient; w is the valve area gradient; ρ is the oil density; K is the load stiffness coefficient; b is the oil damping coefficient; K sv is the amplification factor; V t is the total volume; u i (t) is the output voltage of the ith node; sgn(·) is the sign function.

3. The distributed cooperative control method of multiple electro-hydraulic servo actuators under communication delay according to claim 2 is characterized in that: The process of performing linearization processing to obtain a linear model in step S1 is as follows: Using the state variable z i (t) Linear transformation z i (t)=[x i1 (t) x i2 (t) -θ1x i1 (t)-θ2x i2 (t)+θ3x i3 (t)] T and feedback control variable u i (t) you i (t)=a i (x,t)+β i (x,t)γ i (t) in, γ i (t) is the new control input, and the superscript T indicates transposition; The linear system model is obtained as: y i (t)=C1z i (t) in, B1=[0,0,1] T , C1=[1 0 0],D Li (t)=[0,d Li (t),θ2d Li (t)] T .

4. The distributed cooperative control method of multiple electro-hydraulic servo actuators under communication delay according to claim 3 is characterized in that: The feedback data in step S2 specifically include: hydraulic cylinder output displacement, hydraulic cylinder speed, pressure of chambers on both sides of the hydraulic cylinder, and servo valve core displacement.

5. The distributed cooperative control method of multiple electro-hydraulic servo actuators under communication delay according to claim 4 is characterized in that step S3 uses a disturbance observer to estimate the unknown external load disturbance of the system as: in, The interference estimate The derivative of represents the Kronecker product, P is a positive definite symmetric matrix, e i (t) represents the state error between the ith node and the 0th node, e i (t) = z i (t)-z0(t),λ L is a positive number, Y is a diagonal matrix, and μ is the diagonal μ i The diagonal gain matrix, μ = diag{μ1,μ2,...μ n }.

6. The distributed cooperative control method of multiple electro-hydraulic servo actuators under communication delay according to claim 5 is characterized in that step S5 is based on the Lyapunov candidate function and combines the distributed consistency protocol, feedback data, consistency error and disturbance estimation value to obtain the LMI condition for system stability, which is specifically: Set the Lyapunov energy function, expressed as in, I n is the n-order identity matrix, is the disturbance estimation error; Combining the distributed consensus protocol, feedback data, consistency error and disturbance estimate, the LMI condition for system stability is expressed as Among them, P, Q are positive definite symmetric matrices, and α is a positive number; According to the LMI condition of system stability, the positive definite symmetric matrix P is obtained.

7. A distributed cooperative control method for multiple electro-hydraulic servo actuators under communication delay according to claim 6, characterized in that the positive definite symmetric matrix P is obtained by solving the LMI condition for system stability and is substituted into the consistency protocol vector In the process, the three-node distributed electro-hydraulic servo mechanism is driven in real time according to the updated consistency protocol vector.

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