CN111290015B - Fractional order self-sustaining type electromechanical seismograph system acceleration stability control method with constraint - Google Patents
Fractional order self-sustaining type electromechanical seismograph system acceleration stability control method with constraint Download PDFInfo
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- G01—MEASURING; TESTING
- G01V—GEOPHYSICS; GRAVITATIONAL MEASUREMENTS; DETECTING MASSES OR OBJECTS; TAGS
- G01V1/00—Seismology; Seismic or acoustic prospecting or detecting
- G01V1/24—Recording seismic data
- G01V1/242—Seismographs
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- G01V—GEOPHYSICS; GRAVITATIONAL MEASUREMENTS; DETECTING MASSES OR OBJECTS; TAGS
- G01V1/00—Seismology; Seismic or acoustic prospecting or detecting
- G01V1/16—Receiving elements for seismic signals; Arrangements or adaptations of receiving elements
- G01V1/18—Receiving elements, e.g. seismometer, geophone or torque detectors, for localised single point measurements
- G01V1/181—Geophones
- G01V1/182—Geophones with moving coil
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- G—PHYSICS
- G01—MEASURING; TESTING
- G01V—GEOPHYSICS; GRAVITATIONAL MEASUREMENTS; DETECTING MASSES OR OBJECTS; TAGS
- G01V1/00—Seismology; Seismic or acoustic prospecting or detecting
- G01V1/16—Receiving elements for seismic signals; Arrangements or adaptations of receiving elements
- G01V1/162—Details
- G01V1/164—Circuits therefore
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- G05D—SYSTEMS FOR CONTROLLING OR REGULATING NON-ELECTRIC VARIABLES
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- G05D19/02—Control of mechanical oscillations, e.g. of amplitude, of frequency, of phase characterised by the use of electric means
Abstract
The invention relates to an acceleration stability control method for a constrained fractional order self-sustaining electromechanical seismograph system, and belongs to the field of seismic exploration. The method comprises the following steps: s1: the method comprises the following steps of system modeling, namely establishing a mathematical model of a fractional order self-sustaining type electromechanical seismograph system according to a Newton second law and a kirchhoff law, and defining constraint conditions; s2: designing an acceleration stability controller, which comprises constructing an acceleration feedforward controller and an optimal feedback controller; the acceleration feedforward controller is integrated by a modeling behavior function based on a fractional order inversion method, a fuzzy wavelet neural network and a tracking differentiator; the optimal feedback controller is formed by fusing a fuzzy wavelet neural network and a self-adaptive dynamic programming strategy. The invention can inhibit chaotic oscillation and realize the minimized cost function while ensuring the boundedness of all signals of the closed-loop system and ensuring the safe operation of the system under the constraint condition.
Description
Technical Field
The invention belongs to the field of seismic exploration, and relates to a method for controlling acceleration stability of a constrained fractional order self-sustaining electromechanical seismograph system.
Background
A self-contained electromechanical seismograph system is an electromechanical sensitive instrument and can be used for detecting ground vibration caused by earthquakes. Nonlinear oscillation and chaotic dynamics of a seismograph system have very important influence on stable operation of the seismograph system, and performance indexes are often required to be met in engineering application. Therefore, modeling fractional order self-sustaining electromechanical seismograph systems in an optimal form, dynamics analysis, driving chaotic motion to periodic target trajectories, satisfying system safety constraints, and accelerating stabilization are meaningful and challenging tasks.
There have been sporadic reports of dynamics issues with such seismograph systems over the past several decades. Siewe et al first studied the nonlinear response and chaotic control of the electromechanical seismometer system to the fifth resonance excitation, and they further studied the divergence and control of the co-host orbit of the seismometer system using an analytical method. Hegazy discusses the nonlinear dynamics and vibration control of electromechanical seismometer systems with time-varying stiffness. However, these works are limited only to the dynamics of the integer order electro-mechanical seismograph system and do not accurately describe its operation.
Fractional calculus has received extensive attention in academia since it has proven to be an effective tool for modeling system dynamics with greater accuracy and more design freedom. Later, many research results on fractional order control strategies, such as PI, were reported in successionλDμControl, sliding mode control, robust control, adaptive control and the like. Inversion is well known as a good way to control an uncertain integer order nonlinear system with a triangular structure. Some researchers have further generalized the inversion method to fractional order nonlinear systems, particularly chaotic systems. Liu et al studied the fuzzy inversion control problem of fractional order nonlinear systems and fractional order neural networks with nonlinear inputs and unknown dynamical models. Wei et al discussed the adaptive inversion control problem for fractional order systems and asymmetric fractional order systems using a frequency distribution model. With the increase of the order of the system, the fractional order derivation of the methods can generate 'explosion terms', and meanwhile, the problem of low approximation precision can occur when the general fuzzy logic faces a high-dimensional hyper-chaotic system. Furthermore, regulatory performance control issues, including transient dynamic and steady state responses, cannot be addressed therein.
There are zero and differential countermeasures problems in engineering that involve less resource consumption, and how to approximate the solution of the hamilton-jacobi-isax equation to obtain a nash equilibrium solution becomes somewhat tricky. To address this problem, a learner, such as the Valvouakis, uses data measured along the player trajectory to perform reinforcement learning to solve the multi-player game problem. To solve the zero and derivative countermeasures problem, Modares and Lewis propose an integral reinforcement learning and H ∞ control strategy for constrained input systems. These works are effective for optimal control of integer order systems, not fractional order electro-mechanical seismometer systems. Therefore, how to design an acceleration stability controller with optimal performance for a fractional order electromechanical device remains an open question.
For nonlinear systems given transient and stable behavior, the prescribed performance control has become another interesting but challenging topic. It is worth noting that constraints from safety regulations and physical failures in case of violation of the constraints can lead to degraded performance and unstable operation of the controlled system. The barrier lyapunov function method is used to solve the state constraint problem. In combination with the specified performance control and the barrier Lyapunov function, Zhao et al solve the zero-error tracking problem of the Euler-Lagrange system with full-state constraint and nonparametric uncertainty. Huang et al discusses adaptive neural control for a rigid feedback system with full state constraints at a given performance index. In the fractional order domain, these works are no longer applicable and there is a huge difference between a class of rigid feedback systems and self-sustaining electromechanical seismograph systems with complex dynamics. Furthermore, the optimal energy cost of a non-linear system is not addressed in this type of document.
Disclosure of Invention
In view of the above, the present invention provides a constrained fractional order self-sustaining electromechanical seismograph system acceleration stability control method, which solves the problems of dynamics analysis and acceleration stability control of a fractional order self-sustaining electromechanical seismograph system under an energy mechanism. By using the method, the boundedness of all signals of the closed-loop system is ensured, the safe operation of the system under the condition of meeting the constraint condition is ensured, and the purposes of inhibiting chaotic oscillation and realizing the minimized cost function are achieved.
In order to achieve the purpose, the invention provides the following technical scheme:
a method for controlling acceleration stability of a constrained fractional order self-supporting electromechanical seismograph system is characterized in that a gyro coupling fractional order equation of the control system is established, a phase diagram and a Lyapunov exponent are used for performing dynamics analysis, and strong dependence of chaotic behaviors and periodic behaviors on system physical parameters and fractional order orders is found. The whole controller is composed of an acceleration feedforward controller and an optimal feedback controller. In the acceleration feedforward controller, a modeling behavior function is used for accelerating the convergence of tracking errors in controllable time and speed, unknown items of a transformed fuzzy wavelet neural network approximation system are used, and a tracking differentiator is arranged for solving the complexity problem of the modeling behavior function and fractional order under the framework of a fractional order inversion method. In an optimal feedback controller, an adaptive dynamic programming strategy is proposed to deal with the zero and differential countermeasure solution problem, in which the solution of the constrained hamilton-jacobi-isax equation is solved approximately on-line using a fuzzy wavelet neural network. The method specifically comprises the following steps:
s1: the method comprises the following steps of system modeling, namely establishing a mathematical model of a fractional order self-sustaining type electromechanical seismograph system according to a Newton second law and a kirchhoff law, and defining constraint conditions;
s2: designing an acceleration stability controller, which comprises constructing an acceleration feedforward controller and an optimal feedback controller; the acceleration feedforward controller is integrated by a modeling behavior function based on a fractional order inversion method, a fuzzy wavelet neural network and a tracking differentiator; the optimal feedback controller is formed by fusing a fuzzy wavelet neural network and a self-adaptive dynamic programming strategy.
Further, in step S1, the mathematical model of the fractional order self-sustaining electro-mechanical seismograph system is:
where m is the mass, x is the elongation of the spring, k0Is the linear spring constant, k1Is the cubic spring constant, k2Is the fifth order spring coefficient, B represents the magnetic field, l represents the length of the wire; alpha is the order of fractional order, q is the instantaneous charge, C0Is the linear part of a capacitor, I0Is the initial current, aaAnd abIs the coefficient of the nonlinear part of the capacitor;represents the current; f. ofv=f1+f0cos Ω t represents random vibration due to ground acceleration, f1Represents the critical force and is assumed to be 0, f0And Ω represents the amplitude and frequency of the noise term;
the gyro coupling fractional order control equation of the system is as follows:
wherein u isiI-2, 4 denotes an increasing control input; defining dimensionless parameters: x1=y,x3z, C denotes kaputol definition, μ0Representing a damping system, L being a linear inductor, Q0Represents a reference charge, R is a resistance; new dimensionless variables are defined as y ═ x/l, and z ═ Q/Q0,τ=ωet,
Further, in step S1, the defined constraint condition specifically includes:
definition 1: for the real function f (t), the kapton fractional derivative is given as:
taking laplace transform of the above equation:
if F(k)(0)=0,k=0,1,…,max(pα,pβ) Is formed, wherein pα,pβIf greater than 0, then
Definition 2: defining a constrained cost function as:
where Q (S) > 0, S and U 'represent a penalty function, a tracking error and a positive definite function, and U' is defined as:
wherein R isoRepresenting a symmetric positive definite matrix, λoWhich is a representation of a normal number,representing an optimal control input, and upsilon representing a variable;
definition 3: analogous for kappa (t) ═ 1+ l0(t-t0)2、κ(t)=exp(l0(t-t0) Or κ (t) ═ 1+ tan (0.5 π tanh (t-t)0) Etc.) of the rate functionHas the following characteristics: 1) kappa (t) > 1, where t > t0And κ (t)0)=1;2)Wherein t is more than or equal to t0;3)Is bounded; wherein l0Denotes a constant, t0Represents an initial time;
suppose that: target trajectory xidI 1,3 and the corresponding fractional order derivative are known and bounded, thenWherein A isi>0,
Further, in the step S2, the constructing the acceleration feedforward controller specifically includes:
to specify steady state error and tracking accuracy in a given time, a modeling behavior function is introduced
step 1: to ensure x1And (3) satisfying the constraint condition, and selecting a first Lyapunov candidate function as follows:
the virtual control is selected accordingly as:
obtaining V in conjunction with virtual control1The derivative of (c) is:wherein β represents the modeling behavior function, k1>0,And
step 2: selecting a second Lyapunov candidate function as:wherein the content of the first and second substances,an estimate representing a degree of shooting;
approximating on a compact set using a fuzzy wavelet neural network and reconstructing a fractional tracking differentiator based on an integer tracking differentiator:
wherein the content of the first and second substances,andindicating the state of the tracking differentiator and,representing the input signal of a tracking differentiator,ciAnd σiIndicates that c is satisfiedi0 and 0 < sigmaiA design constant < 1;
the control inputs for the design adaptation law are:
combining the fractional order tracking differentiator and the control input to obtain V2The fractional derivative of (a) is:
and step 3: selecting a third Lyapunov candidate function as:whereinThe virtual control selection is as follows:
wherein k is3Represents a normal number;
determining V in conjunction with virtual control3The derivative of (c) is:
the control inputs and adaptation laws were designed as follows:
wherein k is4Denotes the normal number, Z4Representing the state of a fractional order tracking differentiator;
combining control inputs and adaptive laws to determine V4The derivative of (c) is:
further, in step S2, the constructing an optimal feedback controller specifically includes: first, a controlled system is givenStatistics, cost functions and optimal cost functions, the existence of which satisfiesContinuous differentiable and unbounded Lyapunov function JaWhereinTo representPartial derivatives of (d); defining a symmetric positive definite matrix so thatThen, a fuzzy wavelet neural network is adopted to estimate a cost function, and weight approximation errors are introducedThe optimal control inputs are obtained as:whereinTherefore, a weight self-adaptation law associated with the fuzzy wavelet neural network is deduced, namely:
wherein the content of the first and second substances,korepresenting a design parameter, z1And z2Representing the regulating parameters, the controlled system is:g denotes a fourth order identity matrix.
The invention has the beneficial effects that:
1) the invention establishes a fractional order dynamic model of the self-sustaining electromechanical seismograph system, accurately describes the dynamic characteristics of the system and increases the design freedom of the controller.
2) In order to better detect and record beneficial vibration of the ground, the invention provides an acceleration stability control scheme for converting chaotic motion into conventional motion of a system, so that convergence and stability are accelerated, and the influence of uncertainty and chaotic oscillation is overcome.
3) The overall control strategy of the present invention includes an acceleration feedforward controller and an optimal feedback controller. The acceleration feedforward controller is integrated by a modeling behavior function based on a fractional order inversion method, a fuzzy wavelet neural network and a tracking differentiator, and the optimal feedback controller is formed by fusing the fuzzy wavelet neural network and a self-adaptive dynamic programming strategy. The control strategy not only ensures the boundedness of all signals of the closed-loop system, but also ensures the safe operation of the system under the condition of meeting the constraint condition, and achieves the purposes of inhibiting chaotic oscillation and realizing the minimized cost function.
Additional advantages, objects, and features of the invention will be set forth in part in the description which follows and in part will become apparent to those having ordinary skill in the art upon examination of the following or may be learned from practice of the invention. The objectives and other advantages of the invention may be realized and attained by the means of the instrumentalities and combinations particularly pointed out hereinafter.
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For the purposes of promoting a better understanding of the objects, aspects and advantages of the invention, reference will now be made to the following detailed description taken in conjunction with the accompanying drawings in which:
FIG. 1 is a schematic diagram of an accelerated stability control method of the present invention;
FIG. 2 is a schematic diagram of a self-contained electromechanical seismograph system;
FIG. 3 is a phase diagram at different fractional orders and sets of parameters 1;
FIG. 4 is a phase diagram at different fractional orders and set 2 parameters;
FIG. 5 is a simulation diagram of the relationship between Lyapunov exponent and time history and fractional order;
FIG. 6 is a simulation diagram of target trajectory tracking under different parameters and fractional orders under the condition of the 1 st scenario;
FIG. 7 is a graph of performance for different parameters and fractional order for case 1;
FIG. 8 is a simulation graph comparing the performance of the method of the present invention with AFBC under a verified embodiment;
reference numerals: 1-spring, 2-seismic mass block, 3-shock absorber, 4-frame, 5-coupling magnet coil, 6-permanent magnet, 7-bolt, 8-base.
Detailed Description
The embodiments of the present invention are described below with reference to specific embodiments, and other advantages and effects of the present invention will be easily understood by those skilled in the art from the disclosure of the present specification. The invention is capable of other and different embodiments and of being practiced or of being carried out in various ways, and its several details are capable of modification in various respects, all without departing from the spirit and scope of the present invention. It should be noted that the drawings provided in the following embodiments are only for illustrating the basic idea of the present invention in a schematic way, and the features in the following embodiments and examples may be combined with each other without conflict.
Referring to fig. 1 to 8, a method for controlling acceleration and stability of a constrained fractional order self-sustaining electro-mechanical seismograph system is shown in fig. 1, and includes the following steps:
firstly, modeling a system.
The fractional order self-sustaining electromechanical seismograph system shown in FIG. 2 is comprised of electrical and mechanical parts, where the former is comprised of a linear inductor L, a nonlinear capacitor CNLA non-linear resistor RNLAnd electromotive force evAre connected in series with each other and consist of a shock absorber 3 and a seismic mass 2 suspended on springs. The two parts interact with each other through a coupling magnet coil 5 and a permanent magnet 6 to generate a radial magnetic fieldIn case of earthquake, the vibration generated by crust breaking will radiate outwards from the broken positionAnd (4) shooting. Seismographs detect and measure these vibrations from the vertical motion of the seismic mass. Westerlund and Ekstam disclose fractional order experimental values for various dielectric capacitors, in which the current flowsAnd voltageThere is a fractional order relationship betweenBased on this fact and the persistent memory of the fractional order operator, the voltage of the nonlinear resistor and capacitor is expressed as:
where α is the fractional order, q is the instantaneous charge, R is the resistance, C0Is the linear part of a capacitor, I0Is the initial current, aaAnd abIs the coefficient of the non-linear part of the capacitor,where I is the current.
Obviously, there is friction and air resistance in the system being controlled, writing a spring force with a non-linear stiffness as
Fk=k0+k1x2+k2x4, (2)
Wherein x is the elongation of the spring, k0Is the linear spring constant, k1Is the cubic spring constant, k2Is the fifth order spring rate.
Due to the constituent structures of the permanent magnet and the coupling coil, it is necessary to consider the laplace force of the mechanical part and the lorentz electromotive force of the electrical part. Based on Newton's second law and kirchhoff's law, a mathematical model of a fractional order self-sustaining electromechanical seismograph system is designed as follows:
wherein m is mass, B is magnetic field, l is length of wire, fv=f1+f0cost represents the random vibration due to ground acceleration, f1Represents the critical force and is assumed to be 0, f0And represents the amplitude and frequency of the noise term.
Defining new dimensionless variables as:
wherein Q0Representing a reference charge.
In the Gr ü nwald-Letnikov, Riemann-Luville and Kapopot fractional definitions, the fractional and integer order systems of the Kapopot definition are adopted since they are the same in the form of the initial conditions in the application. Using equations (3) and (4) and increasing the control input uiI is 2,4, and a control equation of the gyro coupling system is derived
Definition 1: for the real function F (t), the fractional order derivative of kapton is given as
Taking Laplace transform from equation (6) to obtain
If F(k)(0)=0,k=0,1,…,max(pα,pβ) Is formed, wherein pα,pβIf greater than 0, then
Definition 2: a constrained cost function is proposed
Where Q (S) > 0, S and U 'represent a penalty function, a tracking error and a positive definite function, and U' is defined as
Wherein R isoRepresenting a symmetric positive definite matrix, λoIndicating a normal number.
Definition 3: analogous for kappa (t) ═ 1+ l0(t-t0)2、κ(t)=exp(l0(t-t0) Or κ (t) ═ 1+ tan (0.5 π tanh (t-t)0) Etc.) of the rate functionHas the following characteristics: 1) kappa (t) > 1, where t > t0And κ (t)0)=1;2)Wherein t is more than or equal to t0;3)Is bounded; wherein l0Denotes a constant, t0Indicating the initial time.
Assume that 1: target trajectory xidI is 1,3 and the corresponding fractional order derivative is known and bounded. This means thatWherein A isi>0,
And II, kinetic analysis.
To reveal the dynamics of the seismometer system, the present example presents two sets of physical parameters of the seismometer system:
group 1: mu.s1=0.1,μ2=0.2,ω1=1,λ1=0.01,λ2=-0.7,β1=0.01,β2=0.1,γ1=0.25,γ2=0.95,ω=0.5,
Group 2: mu.s1=0.03,μ2=0.02,ω1=1,λ1=0.5,λ2=0.6,β1=0.05,β2=0.13,γ1=0.65,γ2=0.42,ω=0.25.
And solving the numerical solution of the fractional order differential equation by adopting a multi-step method.Can be approximated by a product integration quadrature formula to produce an explicit Euler method
Wherein t ismNh, with a constant step h > 0. The first term on the right in equation (11) represents a taylor polynomial of degree n-1 of a function f (t) centered at the time zero. Numerical solution Fm≈F(tm) In each subinterval [ t ]j,tj+1]In the medium approximation, the vector field y (t, f (t)) is approximated by a first order interpolating polynomial.
Fig. 3 and 4 show phase diagrams under different fractional orders and parameters in two cases, and obviously, different parameter sets including fractional orders and external forces can induce periodic, quasi-periodic and chaotic behaviors. The chaotic attractor undergoes magnification, contraction, twisting, and movement. Fig. 5 reveals the time history and the lyapunov exponent of the fractional order, and it can be seen that the fractional order seismograph system exhibits periodic motion and chaotic oscillations due to the negative and positive values of LE. This oscillation caused by the unbalanced interaction of the potential energy can undermine the stability of the system under the energy mechanism.
The control problem of this embodiment is: an acceleration stability control strategy is found by using a cost function (9) and combining a given mathematical model (5) of a fractional order self-sustaining type electromechanical seismograph system, so that all signals in a closed-loop system are bounded, and constraint conditions are metAndand the cost function is minimal. In addition, a target track for detecting and recording earthquake ground vibration is embedded in the chaotic attractor, so that chaotic control is realized.
Designing an acceleration stability controller, which comprises constructing an acceleration feedforward controller and an optimal feedback controller; the acceleration feedforward controller is integrated by a modeling behavior function based on a fractional order inversion method, a fuzzy wavelet neural network and a tracking differentiator; the optimal feedback controller is formed by fusing a fuzzy wavelet neural network and a self-adaptive dynamic programming strategy.
1. Fuzzy wavelet neural network
The fuzzy wavelet neural network has good performance in the aspects of control, prediction and classification. It consists of a series of fuzzy if-then rules:
WhereinA j-th membership function, n, representing the i-th inputsRepresenting the input number, NsRepresenting the number of fuzzy rules considered.
Defining the triggering degree of a rule as
Where i 1, …, N, j 1, …, N, N denotes the number of inputs, N denotes the number of regular neurons,andrepresenting the center and width of the membership function.
The degree of shooting is defined as follows:
let xi ≡ 21,…,ξN]T,w≡[w1,…,wN]TThen, the output of the fuzzy wavelet neural network is as follows:
Wherein ε and DXRepresenting the approximation error and a compact set with bounded X, an optimal parameter w is set*Is equal toSolution of (2), omegawRepresenting an tight set of w. Introduction ofWherein w*Represents satisfactionAndthe virtual amount of (a).
To increase the solution speed, the transformations associated with the fuzzy wavelet neural network are derived from (15)
2. Design acceleration feedforward controller
To specify steady state error and tracking accuracy in a given time, a modeling behavior function is introduced
defining the error variables as:
wherein alpha isi+1Representing virtual control.
Based on the principle of a fractional order inversion method, the acceleration feedforward controller consists of four steps.
Step 1: to ensure x1Satisfying the constraint condition, selecting the first Lyapunov candidate function as
Get V1Derivative of (2)Is composed of
accordingly, the virtual control is selected as
Wherein k is1>0。
According to (22), can convert (21) into
Step 2: selecting a second Lyapunov candidate function as
V is obtained2Fractional order derivative of
involving in system dynamicsThe term is considered an unknown function. To facilitate controller design, it is approximated on a compact set using a fuzzy wavelet neural network, i.e.
Wherein (·) represents (x)1,x2,x3,x4) Abbreviations of (a).
Obviously, due to the complexity of modeling the behavior function and the fractional order, the direct calculationIs very difficult. In order to realize signal estimation of virtual control derivative, a fractional order tracking differentiator is reconstructed based on an integer order tracking differentiator
WhereinAndindicating the state of the tracking differentiator,representing the input signal of a tracking differentiator, ciAnd σiIndicates that c is satisfiedi0 and 0 & ltsigmaiA design constant of < 1.
Combining equations (26) and (27), equation (25) is rewritten as:
then, the control input with the adaptive law is designed as follows
Wherein k is2Indicating a normal number.
Substituting formula (29) and formula (30) into formula (28):
wherein k is3Indicating a normal number.
Obtaining V from (31) and (32)3Derivative of (2)
and 4, step 4: selecting a fourth Lyapunov candidate function
Attention is paid toAnd is identified as an unknown function. Once again with fuzzy wavelet neural networkApproaching it.
Similarly, step 2, the control input and the adaptation law are directly designed as:
wherein k is4Denotes the normal number, Z4Indicating the state of the fractional order tracking differentiator.
The derivative of (34) can be derived using equations (35) and (36) as:
the control strategy consists of an acceleration feedforward controller and an optimal feedback controller. The latter relies on the former rather than being juxtaposed. If it is notAndthe stability of the closed loop system cannot be guaranteed. In addition, the proposed acceleration feedforward controller does not involve optimality.
3. Designing an optimal feedback controller
Based on equation (37), in order to solve the zero-sum differential countermeasure problem of the seismograph system, an optimal feedback control method combined with an adaptive dynamic programming strategy needs to be developed, namely
Wherein G represents a fourth order identity matrix.
From equation (9), the Hamiltonian of equation (38) is defined:
By solving the theory of Hamilton-Jacobi-IsaxxAn optimal cost function J can be calculated*. The optimal control input is written as
Substituting formula (40) into formula (39) to derive Hamilton-Jacobi-Isaxx equation
Introduction 1: given a controlled system (38), a cost function (9) and an optimal control (40), there is a satisfactionContinuous differentiable and unbounded Lyapunov function JaWhereinTo representPartial derivatives of (a). Defining a symmetric positive definite matrix gamma
To solve the problem of likeSuch unknown systemSystem dynamics problem, using fuzzy wavelet neural network to estimate cost function
Through Taylor expansion, the optimal control input and Hamilton-Jacobi-Isaxx equation are obtained
given that the weights of the fuzzy wavelet neural network are unknown, it is necessary to introduce currently known weights instead of them:
whereinAnddenotes J and woAn estimate of (d). In addition, the weight approximation error is defined as
Calling formula (45), the optimum control input can be rewritten as
Equation (41) becomes:
invoke formula (39), need to selectMake the square residual errorAnd (4) minimizing. However, during learning, only e is adjustedqThe stability of the controlled system cannot be guaranteed. Therefore, a weight adaptation law associated with the fuzzy wavelet neural network is derived, namely:
The weight adaptation law consists of three parts. The first part is used for stability analysis, the second part is used for minimizing a Hamiltonian, and the third part is used for guaranteeing the system state to be bounded.
Fourth, stability analysis
Theorem 1: for the acceleration stability control problem of the fractional order self-sustaining electromechanical seismograph system described by the formula (5) and having the cost function formula (9), the acceleration feedforward control input with the adaptive law formula (30) and the formula (36) is designed to be the formula (29) and the formula (35). If the optimal feedback control input is derived as equation (46) by an update law (48) associated with the fuzzy wavelet neural network, all signals in the closed loop system are bounded and do not violate the constraints. At the same time, accelerated stabilization is achieved and the cost function is minimized.
And (3) proving that: selecting the entire Lyapunov candidate function
The derivative of equation (49) is:
equation (50) is further simplified as:
By adjusting ki,i=1,…,4、bi,i=2,4、Ro、λo、ko、ziAnd i is 1,2 and other design parameters, so that satisfactory transient performance and stable results can be obtained. Direct adjustment of kiA lower tracking error can be obtained. However, too large kiThe value will result in a larger control input. Alternative ziTo guarantee the matrixIs a positive definite matrix.
The examples verify that:
the parameters of the acceleration feedforward controller and the tracking differentiator are set to k1=k2=10、k3=k4=15、b2=b4=0.6、l0=1、c1=c34 and σ1=σ30.2. Selecting a parameter for shaping the behavior function as ηb=1.1、Andselecting a target trajectory as x1d1.5sin3t and x3d0.9sin2 t. A is easily obtained1=1.5,A3=0.9,Andin the optimal feedback controller, the constraint condition of the optimal control input isPenalty function Q equal toSymmetric positive definite matrix RoIs set to I4×4. In addition, z2≡8×I4×4,z1≡[9 9 9 9]TAnd k o5. The center and width of the fuzzy wavelet neural network are defined asAnd
fig. 6 shows target trajectory tracking for different parameters and fractional orders in case 1. The fractional order self-sustaining electromechanical seismograph system can realize high-precision track tracking in a short time. Over time, changes in the external and internal environments to system parameters and fractional order do not affect tracking performance. Compared with fig. 3-4, the controller is designed to completely suppress the chaotic oscillation related to the potential energy. As can be seen from fig. 7, sub-graphs 1 and 5, the Lyapunov function-based control scheme does not violate the state constraint, and the modeling behavior function accelerates the stabilization process regardless of the change of the system parameters and the fractional order.
The 2 nd and 6 th subgraphs of figure 7 reveal the ability of the fuzzy wavelet neural network to approximate unknown system dynamics. It can also be seen that this approximation capability is insensitive to system parameters and sensitive to fractional order. In the 4 th and 8 th sub-graphs of fig. 7, the optimal control input satisfies given constraints regardless of the system parameters and fractional order. The remaining figures of fig. 7 further show the stable control performance of the proposed scheme at different parameters and fractional orders.
In order to verify the superiority of the control method, the scheme designed by the invention is compared with an adaptive fuzzy inversion control (AFBC) method. It can be seen from fig. 8 that the proposed scheme is significantly better than AFBC, both in terms of stable amplitude and response time.
Finally, the above embodiments are only intended to illustrate the technical solutions of the present invention and not to limit the present invention, and although the present invention has been described in detail with reference to the preferred embodiments, it will be understood by those skilled in the art that modifications or equivalent substitutions may be made on the technical solutions of the present invention without departing from the spirit and scope of the technical solutions, and all of them should be covered by the claims of the present invention.
Claims (4)
1. A constrained fractional order self-sustaining electromechanical seismograph system acceleration stability control method, comprising the steps of:
s1: the method comprises the following steps of system modeling, namely establishing a mathematical model of a fractional order self-sustaining type electromechanical seismograph system according to a Newton second law and a kirchhoff law, and defining constraint conditions;
s2: designing an acceleration stability controller, which comprises constructing an acceleration feedforward controller and an optimal feedback controller; the acceleration feedforward controller is integrated by a modeling behavior function based on a fractional order inversion method, a fuzzy wavelet neural network and a tracking differentiator; the optimal feedback controller is formed by fusing a fuzzy wavelet neural network and a self-adaptive dynamic programming strategy;
in step S1, the mathematical model of the fractional order self-sustaining electromechanical seismograph system:
where m is the mass, x is the elongation of the spring, k0Is the linear spring constant, k1Is the cubic spring constant, k2Is the fifth order spring coefficient, B represents the magnetic field, l represents the length of the wire; alpha is the order of fractional order, q is the instantaneous charge, C0Is the linear part of a capacitor, I0Is the initial current, aaAnd abIs the coefficient of the nonlinear part of the capacitor;represents the current; f. ofv=f1+f0cos Ω t represents random vibration due to ground acceleration, f1Represents the critical force and is assumed to be 0, f0And Ω represents the amplitude and frequency of the noise term;
the gyro coupling fractional order control equation of the system is as follows:
wherein u isiI-2, 4 denotes an increasing control input; defining dimensionless parameters: x1=y,x3z, C denotes kaputol definition, μ0Representing a damping system, L being a linear inductor, Q0Represents a reference charge, R is a resistance; new dimensionless variables are defined as y ═ x/l, and z ═ Q/Q0,τ=ωet,
2. The method for controlling acceleration and stabilization of a fractional order self-sustaining electro-mechanical seismograph system with constraints as claimed in claim 1, wherein the defined constraints in step S1 specifically include:
definition 1: for the real function f (t), the kapton fractional derivative is given as:
taking laplace transform of the above equation:
if F(k)(0)=0,k=0,1,…,max(pα,pβ) Is formed, wherein pα,pβIf greater than 0, then
Definition 2: defining a constrained cost function as:
where Q (S) > 0, S and U 'represent a penalty function, a tracking error and a positive definite function, and U' is defined as:
wherein R isoRepresenting a symmetric positive definite matrix, λoWhich is indicative of a normal number of the cells,representing an optimal control input, and upsilon representing a variable;
definition 3: function of rateHas the following characteristics: 1) kappa (t) > 1, where t > t0And κ (t)0)=1;2) Wherein t is more than or equal to t0;3)Is bounded; wherein l0Denotes a constant, t0Represents an initial time;
suppose that: target trajectory xidI 1,3 and the corresponding fractional order derivative are known and bounded, then | xid|≤Ai<kζiWherein A isi>0,kζi>0。
3. The method for acceleration stability control of a constrained fractional order self-sustaining electro-mechanical seismograph system of claim 2, wherein in step S2, the constructing of the acceleration feedforward controller specifically comprises:
to specify steady state error and tracking accuracy in a given time, a modeling behavior function is introduced
step 1: to ensure x1And (3) satisfying the constraint condition, and selecting a first Lyapunov candidate function as follows:
the virtual control is selected accordingly as:
obtaining V in conjunction with virtual control1The derivative of (c) is:wherein β represents the modeling behavior function, k1>0,And
step 2: selecting a second Lyapunov candidate function as:wherein the content of the first and second substances,an estimate representing a degree of shooting;
approximating on a compact set using a fuzzy wavelet neural network and reconstructing a fractional tracking differentiator based on an integer tracking differentiator:
wherein the content of the first and second substances,andindicating the state of the tracking differentiator,representing the input signal of a tracking differentiator, ciAnd σiIndicates that c is satisfiedi0 and 0 < sigmaiA design constant < 1;
the control inputs for the design adaptation law are:
combining the fractional order tracking differentiator and the control input to obtain V2The fractional derivative of (a) is:
The virtual control selection is as follows:
wherein k is3Represents a normal number;
determining V in conjunction with virtual control3The derivative of (c) is:
the control inputs and adaptation laws were designed as follows:
wherein k is4Denotes the normal number, Z4Representing a tracking differentiator of fractional orderA state;
combining control inputs and adaptive laws to determine V4The derivative of (c) is:
4. the method for acceleration stability control of a constrained fractional order self-sustaining electromechanical seismograph system of claim 3, wherein in step S2, constructing an optimal feedback controller specifically comprises: first, given a controlled system, a cost function, and an optimal cost function, there is a satisfactionContinuous differentiable and unbounded Lyapunov function JaWhereinTo representPartial derivatives of (d); defining a symmetric positive definite matrix gammaThen, a fuzzy wavelet neural network is adopted to estimate a cost function, and weight approximation errors are introducedThe optimal control inputs are obtained as:whereinTherefore, a weight self-adaptation law associated with the fuzzy wavelet neural network is deduced, namely:
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