Stabilization of nonlinear switched systems using control Lyapunov functions

In this paper, we study the stabilization of general nonlinear switched systems by using control Lyapunov functions. The concept of control Lyapunov function for nonlinear control systems is generalized to switched control systems. The first part of our contribution provides a necessary and sufficient condition of stabilization. The main idea is to use a common control Lyapunov function; this is achieved with the converse Lyapunov theorem dedicated to switched systems. In the second part, an explicit construction of a common control Lyapunov function is addressed with respect to a finite family of switched systems. The approach uses a family of control Lyapunov functions attached to the subsystems.     

Stabilization of generalized Hamiltonian systems with internally generated energy and applications to power systems

Passivity-based control (PBC) is a very powerful design methodology for dynamic systems. In this paper, the stabilization of generalized Hamiltonian control systems with internally generated energy is considered using PBC. Sufficient conditions concerning the passivation of this kind of Hamiltonian control systems are given. The results are applied to power systems, including multimachine power systems with steam valve control and single machine infinite bus with superconducting magnetic energy storage. Simulations are employed to demonstrate the effectiveness of the proposed control methodology.     

Approximability of nonlinear affine control systems

This paper focuses on a strong approximability property for nonlinear affine control systems. We consider control processes governed by ordinary differential equations (ODEs) and study an initial system and the associated generalized system. Our theoretical approach makes it possible to prove a strong approximability result for the above dynamical systems. The latter can be effectively applied to some classes of variable structure and hybrid control systems. In particular, this paper deals with applications of the strong approximability property obtained to the conventional sliding mode processes and to hybrid control systems with autonomous location transitions. We also take into consideration some optimal control problems for the above class of hybrid systems.     

Isolation of the Trivial Part of a Nonlinear Control System by Factorization: I

The problem of constructing aggregated systems (quotient systems) of the simplest kind for nonlinear control systems is considered. With the help of this factorization, the original control system is reduced to a decomposition that allows one to reduce the dimension of control problems.     

非线性退化时滞微分控制系统的函数能控性

本文讨论非线性退化时滞微分控制系统．首先就非线性退化时滞微分控制系统的一阶变分系统给出变易公式,然后就非线性退化时滞微分控制系统的一阶变分系统的函数能控性给出一些判据,最后给出关于非线性退化时滞微分控制系统的函数能控性的判据．     

Nonlinear open-plus-closed-loop (NOPCL) control of dynamic systems

A nonlinear open-plus-closed-loop (NOPCL) control strategy is proposed in this paper to entrain complex dynamic systems to arbitrarily given goal dynamics. It contains nonlinear closed-loop control actions as well as nonlinear open-loop control actions. Compared to the existing open-plus-closed-loop (OPCL) control, the NOPCL control usually results in much simpler error equations that determine the basins of entrainment of the controlled dynamic systems. For a large number of dynamic systems such as the Lorenz, Rossler, Duffing, Van der Pol, and Chua systems, the NOPCL control is shown to have global basins of entrainment for arbitrarily given goal dynamics.     

On the Optimal Stabilisation for a set of Programmed Motions of the Bilinear Control System

During recent years there has been considerable interest in using bilinear systems [1, 2] as mathematical models to represent the dynamic behavior of a wide class of engineering, biological and economic systems. Moreover, there are some methods [3] which may approximate nonlinear control systems by bilinear systems. For the first time Zubov has proposed a method of stabilization control synthesis for a set of programmed motions in linear systems [4]. In papers [5, 6] this method has been developed and used to solve the same problem for bilinear systems. In the present paper the following problems are considered. First, synthesis of nonlinear control as feedback under which the bilinear control system has a given set of programmed and asymptotic stable motions. Because this control is not unique, the second problem concerns optimal stabilization. In this paper a method for the design of nonlinear optimal control is suggested. This control is constructed in the form of a convergent series. The theorem on the sufficient conditions to solve this problem is represented.     

Sufficient and necessary conditions for absolute stability of time-delayed Lurie control systems

In this paper, we present some sufficient and necessary conditions for the absolute stability of time-delayed Lurie control systems, which improve the results we obtained before for the absolute stability of direct control, indirect control and critical control of Lurie systems. We also derived certain simple and easy applicable algebraic sufficient conditions for the absolute stability of time-delayed Lurie control systems, which provide a convenient tool for practical control engineers in designing absolutely stable systems or stabilizing nonlinear control systems.     

Finite time synchronization of chaotic systems

Using finite time control techniques, continuous state feedback control laws are developed to solve the synchronization problem of two chaotic systems. We demonstrate that these two chaotic systems can be synchronized in finite time. Examples of Duffing systems, Lorenz systems are presented to verify our method.     

Suboptimal Control of Time-Varying Neutral Control Systems

In this paper,the optimal control of time-varying neutral control systems is investigated by means of the Maxmium Principle of time-delay systems.optimal control law is given. Then sub-optimal control of time-varying neutral control systems is studied by using sensitivity approach. Algorithm for suboptimal control is given.     

Minimum-fuel control of high-order systems

The minimum-fuel control problem is of special interest in various space systems. To date, solutions of minimum-fuel control problems have been carried out for relatively low-order systems. Space structures, however, are generally characterized by a large number of degrees of freedom, so that minimum-fuel control of such systems requires a new approach. In the independent modal-space control (IMSC) method, the control laws are designed in the modal space for each mode independently. The minimum-fuel problem reduces to that of a set of independent second-order systems, so that minimum-fuel control is possible. This paper shows how the IMSC method can be used to control a space structure with a minimum amount of fuel. A numerical example is presented.This research was supported by NASA Research Grant No. NAG-1-225, sponsored by the Spacecraft Control Branch, Langley Research Center.     

Contributions to flatness‐based control of systems with input‐dependent delays

Flatness‐based control of nonlinear systems has been generalized in [1] to systems with time‐delays of constant amplitude. Continuous stirred tank chemical reactors with recycle provide examples of such systems. However, if the volume flow‐rate in the recycle is used as control input the time delay depends on control. This can be avoided by a proper choice of the independent variable, i.e., time transformation: Transported volume is used instead of time. This leads to systems with a time delay of constant amplitude belonging to a class of systems which can be called a generalized type of π‐flat systems [2], barely studied so far. Motion planning and tracking control can be achieved by flatness‐based methods.     

Model-reference control of chaotic systems

In this paper, the problem of controlling chaotic systems is studied. A control law is introduced for a chaotic system to follow a desired reference system. The control strategy is developed within the general framework of the nonlinear model-reference control systems. Lyapunov stability is used to ensure the global stability of the error dynamics represents the difference between the desired and chaotic systems.     

Research on mean square exponential stability of networked control systems with multi-step delay

A new control mode is proposed for networked control systems whose network-induced delay is longer than a sampling period. The proposed control mode can make full use of control information and improve the performance of the system. Under the control mode, the mathematical model of networked control systems is obtained. Markov characteristic of the transfer delay is discussed. Based on Markov chain theory, the infinite horizon controller is designed, which is shown to render corresponding networked control systems mean square exponentially stable. Simulation results show the validity of the proposed theory.     

一类具独立子系统的退化时滞控制系统的能控性

讨论退化时滞微分控制系统的能控性问题.首先将退化时滞微分控制系统化为标准形式,除去关联项,得到具独立子系统的退化时滞微分控制系统.然后就一般的退化时滞微分控制系统,得到其能控的充要条件为其可达集等于全空间.对于具独立子系统的广义时滞控制系统,给出其能控的充要条件为每个子系统的可达集等于其相应的子空间,并给出其能控的代数判据,最后举例说明主要结果的应用.     

Approximate controllability of a class of semilinear degenerate systems with boundary control

This paper concerns a class of control systems governed by semilinear degenerate equations with boundary control in one-dimensional space. The control is proposed on the ‘degenerate’ part of the boundary. The control systems are shown to be approximately controllable by Kakutani's fixed point theorem.     

Relaxation of nonlinear impulsive controlled systems on Banach spaces

Relaxation control for a class of semilinear impulsive controlled systems is investigated. Existence of mild solutions for semilinear impulsive controlled systems is proved. By introducing a regular countably additive measure, we convexify the original control systems and obtain the corresponding relaxed control systems. The existence of optimal relaxed controls and relaxation results is also proved.     

The observability of linear singularly perturbed systems in state space

The state-space method is used to investigate the complete x- and y-relative observability of linear stationary singularly perturbed (LSSP) systems. Criteria, necessary conditions and sufficient conditions, phrased in terms of matrix ranks, are obtained for the observability; they involve the solutions of the defining equations, which are recurrent algebraic matrix equations. Duality principles are established between the LSSP observed and the control systems with coefficients of varying scales, the LSSP observed systems and LSSP control systems, and the governing equations for the observed and control systems. An example is given.     

On the dependence of the solutions and optimal solutions of control problems on the control constraint set

In this paper we examine the dependence of the solutions and optimal solutions of a class of linear, infinite dimensional control systems on the control constraint set. This is done using the weak and the Kuratowski-Mosco convergence of sets. First we establish some general facts about weakly convergent multifunctions. Then we prove some convergence theorems for the trajectories of certain control systems. We also derive a general relaxation theorem. Subsequently we pass to optimal control problems and prove various convergence results. We conclude with an example from parabolic control systems.Research supported by N. S. F. Grant DMS-8802688