STABILITY OF SWITCHED POLYNOMIAL SYSTEMS

This paper investigates the stability of （switched） polynomial systems. Using semi-tensor product of matrices, the paper develops two tools for testing the stability of a （switched） polynomial system. One is to convert a product of multi-variable polynomials into a canonical form, and the other is an easily verifiable sufficient condition to justify whether a multi-variable polynomial is positive definite. Using these two tools, the authors construct a polynomial function as a candidate Lyapunov function and via testing its derivative the authors provide some sufficient conditions for the global stability of polynomial systems.

Control synthesis for polynomial nonlinear systems and application in attitude control

A method for positive polynomial validation based on polynomial decomposition is proposed to deal with control synthesis problems. Detailed algorithms for decomposition are given which mainly consider how to convert coefficients of a polynomial to a matrix with free variables. Then, the positivity of a polynomial is checked by the decomposed matrix with semidefinite programming solvers. A nonlinear control law is presented for single input polynomial systems based on the Lyapunov stability theorem. The control synthesis method is advanced to multi-input systems further. An application in attitude control is finally presented. The proposed control law achieves effective performance as illustrated by the numerical example.

An Iteration Method Based on Homotopy Function for Solving Polynomial Systems and Application to Mechanisms Problems

A new iterating method based on homotopy function is developed in this paper. All solutions can be found easily without the need of choosing proper initial values. Compared to the homotopy continuation method, the solution process of the present method is simplified, and the computation efficiency as well as the reliability for obtaining all solutions is also improved. By application of the method to the mechanisms problems, the results are satisfactory.

Analyzing Boolean Functions via Solving Parametric Polynomial Systems

In this paper,a new method to analyze Boolean functions is proposed.By this method,one can analyze the balancedness,the nonlinearity,and the input-output correlation of vectorial Boolean functions.The basic idea of this method is to compute the refined covers of some parametric Boolean polynomial systems which are equivalent to these problems.By a refined cover,the parameter space is divided into several disjoint components,and on each component,the parametric Boolean polynomial system has a fixed number of solutions.An efficient algorithm based on the characteristic set method to compute refined covers of parametric Boolean polynomial systems is presented.The experimental results about some instances generated from cryptanalysis show that this new method is efficient and can solve some instances which can not be solved in reasonable time by other methods.

DENSITY OF MARKOV SYSTEMS AND ZEROS OF CHEBYSHEV POLYNOMIALS

We raise and partly answer the question: whether there exists a Markov system with respect to which the zeros of the Chebyshev polynomials are dense, but the maximum length of a zero free interval of the nth Chebyshev polynomial does not tends to zero. We also draw the conclu- tion that a Markov system, under an additional assumption, is dense if and only if the maxi- mum length of a zero free interval of the nth associated Chebyshev polynomial tends to zero.

Connection between Volterra series and perturbation method in nonlinear systems analyses

This paper is concerned with the connection between the Volterra series and the regular perturbation method in nonlinear systems analyses. It is revealed for the first time that, for a forced polynomial nonlinear system, if its derived linear system is a damped dissipative system, the steady response obtained through the regular perturbation method is exactly identical to the response given by the Volterra series. On the other hand, if the derived linear system is an undamped conservative system, then the Volterra series is incapable of modeling the forced polynomial nonlinear system. Numerical examples are further presented to illustrate these points. The results provide a new criterion for quickly judging whether the Volterra series is applicable for modeling a given polynomial nonlinear system.

INTEGRABILITY VIA INVARIANT ALGEBRAIC CURVES FOR PLANAR POLYNOMIALDIFFERENTIAL SYSTEMS

We present an introduction to the Darboux integrability theory of planar complex and real polynomial differential systems containing some improvements to the classical theory.

Adaptive H∞control of polynomial Hamiltonian systems via symbolic computation:controller parameterisation

This paper deals with controller parameterisation method of adaptive H∞control for polynomial Hamiltonian systems(PHSs)with disturbances and unknown parameters.We design a simplified controller with a set of tuning parameters which can guarantee that the systems are adaptive H∞stable by using Hamiltonian function method.Then,a method for solving the set of tuning parameters of the controller with symbolic computation is presented.The proposed parameterisation method avoids solving Hamilton–Jacobi–Issacs(HJI)equations and the obtained controller is easier as compared to some existing ones.Simulation example shows that the controller is effective as it can optimise adaptive H∞control by adjusting tuning parameters.All these results are expected to be of use in the study of adaptive H∞control for nonlinear systems with disturbances and unknown parameters.

The Center Problem and Time-Reversibility with Respect to a Quadratic Involution for a Class of Polynomial Differential Systems with Order 2 or 3

Most studies of the time-reversibility are limited to a linear or an affine involution.In this paper,the authors consider the case of a quadratic involution.For a polynomial differential system with a linear part in the standard form(-y,x)in R~2,by using the method of regular chains in a computer algebraic system,the computational procedure for finding the necessary and sufficient conditions of the system to be time-reversible with respect to a quadratic involution is given.When the system is quadratic,the necessary and sufficient conditions can be completely obtained by this procedure.For some cubic systems,the necessary and sufficient conditions for these systems to be time-reversible with respect to a quadratic involution are also obtained.These conditions can guarantee the corresponding systems to have a center.Meanwhile,a property of a center-focus system is discovered that if the system is time-reversible with respect to a quadratic involution,then its phase diagram is symmetric about a parabola.

CENTERS OF SOME CUBIC SYSTEMS

We solve the l:-l resonant center problem for two cubic systems with complex coefficients.

POLYNOMIAL DIFFERENTIAL SYSTEM WITH DEGENERATE INFINITY

In this paper we show the distribution of critical points at infinity of n- dimensional polynomial differential systems, and give the conditions, under which the system is degenerate at infinity. Also, we discuss the quadratic systems with degenerate infinity, and obtain some similar properties to 2-dimensional quadratic systems.

Linear homotopy method for computing generalized tensor eigenpairs

Let m, m＇, n be positive integers such that m ≠ m＇. Let A be an ruth order n-dimensional tensor, and let B be an m＇th order n-dimensional tensor. ）, ∈ C is called a B-eigenvalue of A if Ax^m-1 = λBx^m＇-1 and Bx^m＇ = 1 for some x ∈ Cn／{0}. In this paper, we propose a linear homotopy method for solving this eigenproblem. We prove that the method finds all isolated B- eigenpairs. Moreover, it is easy to implement. Numerical results are provided to show the efficiency of the proposed method.