The transitivity in simultaneous stabilization

This paper deals with the transmission problem in simultaneous stabilization of time-varying linear systems. We establish two criteria for the transitivity in simultaneous stabilization. In particular, we give a necessary and sufficient condition for certain linear systems to satisfy a strengthened version of transitivity.     

Coprime factorization of discrete time-varying systems

A necessary condition is given for the existence of coprime factorizations for time-varying systems. This allows one to easily give unstable plants for which such factorizations do not exist.     

Simultaneous controller design for time-varying linear systems

In this paper, we establish the parametrization of all simultaneously stabilizing controllers for two time-varying linear systems. A new approach to the simultaneous stabilization of three time-varying linear systems is also provided.     

Stabilizability,representations and factorizations for time-varying linear systems

We study the system representations, factorizations and stabilizability of a discrete-time time-varying linear system in the framework of nest algebra. We shown that every time-varying linear system admits a normalized left factorization, while it may possibly not have a right factorization. The relationship between the system representation and factorization is studied, and some new stabilizability criteria are established.     

On strong stabilization for linear time-varying systems

This paper deals with the strong stabilization problem for linear time-varying systems and gives a sufficient condition, in terms of the coprime factors, for the existence of strong stabilizers for such a system.     

On robustness in the gap metric and coprime factor uncertainty for LTV systems

In this paper, we study the problem of robust stabilization for discrete linear time-varying (LTV) systems subject to time-varying normalized coprime factor uncertainty. Operator theoretic results which generalize similar results known to hold for linear time-invariant (infinite-dimensional) systems are developed. In particular, we compute an upper bound for the maximal achievable stability margin under TV normalized coprime factor uncertainty in terms of the norm of an operator with a time-varying Hankel structure. We point to a necessary and sufficient condition which guarantees compactness of the TV Hankel operator, and in which case singular values and vectors can be used to compute the time-varying stability margin and TV controller.     

On stabilization for discrete linear time-varying systems

In this paper, we consider the stabilization problem for discrete linear time-varying systems in an operator-theoretic framework. By using the complete finiteness of a certain discrete nest algebra, we show that a system is stabilizable if and only if it has one kind of strong representation and we also give a parametrization for all the stabilizing controllers in terms of this strong representation. This result extends the Youla parametrization theorem by only requiring a strong left or a strong right representation but not both. The strong stabilization problem is also discussed.     

Output-feedback stabilization for stochastic high-order nonlinear systems with time-varying delay

This paper investigates output-feedback control for a class of stochastic high-order nonlinear systems with time-varying delay for the first time. By introducing the adding a power integrator technique in the stochastic systems and a rescaling transformation, and choosing an appropriate Lyapunov-Krasoviskii functional, an output-feedback controller is constructed to render the closed-loop system globally asymptotically stable in probability and the output can be regulated to the origin almost surely. A simulation example is provided to show the effectiveness of the designed controller.     

On the simultaneous stabilization for a family of time‐varying linear systems under the transmission condition

This paper deals with the simultaneous stabilization problem for a family of discrete time‐varying linear systems in the framework of nest algebra. Under the transmission condition, a necessary and sufficient condition for simultaneous "stabilizability" is established in terms of single strong representation for only one controller in the transmission condition, in which the resulting characterization involves no strong representation of the plants compared to previous work.     

Stability analysis for time-varying systems via quadratic constraints

In this paper, we introduce the concept of “quadratic constraint” (QC) to deal with various stability problems for infinite dimensional linear discrete time-varying (LTV) systems. First, we derive a necessary and sufficient condition for the close-loop stability based on quadratic constraints (QCs). An equivalent condition of this stability criterion presents the relationship between the stabilization of each finite dimensional truncation system and that of the whole system. Moreover, applying this stability criterion and the complete finiteness of the nest algebra, we show that the plant is stabilizable if and only if it has a single strong representation. Finally, we use QCs to give a necessary and sufficient condition for the robust stabilization of connected uncertainty set defined by gap metric.     

Robustness for time-varying systems

We consider robust optimization for time-varying systems in terms of perturbations of fractional representations. Upper and lower bounds are given for the maximal radius of the operator ball around a given plant which can be stabilized by a single compensator. In the time-invariant case, these numbers are equal.     

Delay-dependent robust exponential stabilization foruncertain systems with interval time-varying delays

New robust exponential stabilization criteria for interval time-varying delay systems with norm-bounded uncertainties are proposed. Based on the free-weighting matrices and new Lyapunov-Krasovskii functionals, such criteria are obtained by dealing with system model directly and designing memoryless state feedback controllers and expressed in terms of linear matrix inequalities （LMIs）. Moreover, the criteria are applicable to the case whether the derivative of the time-varying delay is bounded or not. The state decay rate is estimated by the corresponding LMIs. Numerical examples are given to illustrate the effectiveness of the proposed method.     

Stability analysis for linear time-varying systems using bicoprime factorization

This paper presents a bicoprime factorization (BCF) approach to deal with various stability problems for linear discrete time-varying (LTV) systems within the framework of nest algebra. Based on the bicoprime factorization, we give necessary and sufficient conditions for (strongly) simultaneous stabilization of three systems, which generalize similar results for systems by coprime factorization (CF). Finally, when the bicoprime factorization for the plant and controller has additive perturbations, we derive sufficient conditions using the norm inequality for robust stability of the system.     

Non-smooth simultaneous stabilization of nonlinear systems: An interpolation method

In this paper, we introduce a method which enables us to construct a continuous simultaneous stabilizer for pairs of systems in which cannot be simultaneously stabilized by means of C¹ feedback. We extend this method to higher-dimensional systems and show that any pair of asymptotically stabilizable nonlinear systems can be simultaneously stabilized (not asymptotically) by means of continuous feedback.     

Some new results on the simultaneous stabilizability of a family of single input, single output systems

In this paper, we obtain sufficiency conditions on the problem of simultaneous stabilization of a parameterized family of single input, single output plants by a non-switching compensator. The sufficiency conditions include simultaneous stabilization and simultaneous pole assignment of a finite number of plants.     

Global asymptotic stabilization for controllable systems without drift

This paper proves that the accessibility rank condition on ⁿ {0} is sufficient to guarantee the existence of a global smooth time-varying (but periodic) feedback stabilizer, for systems without drift. This implies a general result on the smooth stabilization of nonholonomic mechanical systems, which are generically not smoothly stabilizable using time-invariant feedback.     

Exponential stabilization of nonholonomic dynamic systems by smooth time-varying control

A general dynamic model is proposed for describing a large class of nonholonomic systems including extended chained systems, extended power systems, underactuated surface vessel systems etc. By introducing an assistant state variable and a time-varying state transformation based on the concept of minimal dilation degree, this class of nonholonomic systems is transformed into linear time-varying control systems, and the asymptotic exponential stability is thus achieved by using a smooth time-varying feedback control law. The existence and uniqueness of the minimal dilation degree for the discussed systems are also proved under certain conditions.     

Rank-one LMI approach to simultaneous stabilization of linear systems

Following a polynomial approach to control design, the simultaneous stabilization by a controller of given fixed order of a family of SISO linear systems is interpreted as an NP-hard BMI feasibility problem. Upon formulating this BMI problem as an LMI problem with an additional non-convex rank constraint, two simultaneous stabilization methods are then proposed. The first method is a heuristic algorithm performing rank minimization by potential reduction. The second method hinges upon necessary conditions and sufficient conditions for simultaneous stabilization derived from geometric properties of the intersection of a set of ellipsoids. Both methods are then illustrated by numerical examples.     

时变线性系统同时强镇定控制器设计

在套代数框架下, 应用素分解的方法, 设计能同时强镇定两个时变线性系统的稳定控制器, 并给出了所有控制器的参数化. 应用该控制器参数化, 对某类同时鲁棒强镇定问题进行研究, 给出了两个时变线性系统可被同时强鲁棒镇定的充分条件. 针对所得的控制器设计结果给出了数值例子, 数值结果表明了该设计是有效和可行的.