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We address the design of parameter-dependent dynamic output feedback controllers for discrete-time systems with time-varying parameters and subject to actuators saturations. The particularity of the proposed controller is that all its matrices are dependent of the varying parameters, differently from a previous proposed compensator that was partially dependent of the parameters. The proposed LMI stability and stabilization results are based on the use of a parameter dependent Lyapunov function and on the λ-contractivity of the associated level set to guarantee the local stability and some time performance. Two control strategies are addressed: avoiding saturation and allowing saturation, in both cases taking into account the realistic consideration of local validity of the plant model. The proposed numerical example shows the control design for a nonlinear system represented by a Takagi-Sugeno Fuzzy model.

This paper addresses the problem of stabilization of discrete-time systems including a cone-bounded nonlinearity and a saturating actuator. In the sense of Lyapunov stability, we introduce a new candidate Lyapunov function which takes nonlinearity behavior into account. The local stability criterion is formulated as a set of Bilinear Matrix Inequalities (BMI) conditions. We present an optimization problem in order to guarantee the closed-loop stability aiming the largest basin of attraction, which may be nonconvex, and/or, nonconnected. Furthermore, a simple iterative algorithm is proposed in order to solve our BMI problem. Some numerical examples are presented to highlight the relevance of the new Lyapunov function in regard to the classical quadratic function.

In the present work a systematic methodology for computing output stabilizing feedback control laws for nonlinear systems subject to saturating inputs is presented. In particular, the class of L'ure type nonlinear systems is considered. Based on absolute stability tools and a modified sector condition to take into account input saturation effects, an LMI framework is proposed to design the controller. Both regional (local) and global stabilization results are presented. The controller structure is composed by a linear part, an anti-windup loop and a term associated to the output of the dynamic nonlinearity. Convex optimization problems are proposed in order to compute the controller matrices aiming at the maximization of the basin of attraction, or the performance enhancement with a guaranteed region of stability. A numerical example illustrates the potentialities of the methodology.

In this paper the position control of robot manipulators considering joint flexibilities and friction compensation is presented. For the control purposes a cascade control strategy is presented and the friction compensation is described using the Generalized Maxwell-Slip (GMS) model. The GMS parameters are identified and a friction observer based on this model is proposed and incorporated to the cascade strategy so that the stability and performance can be improved. An experimental setup was constructed to validate the proposed control and friction compensation strategy: a planar two degrees of freedom robot with joint flexibilities prototype. The behavior of the cascade control with GMS model was tested in simulation and it was validated in the experimental setup.

This paper deals with designing Linear-Parameter Varying state feedback controls for systems including structured uncertainties described by a poly-tope, in the multiobjective framework. These controls are obtained by noncon-vex coupled Semi-Definite Programs for linear-quadratic nonzero-sum differential games on infinite time horizon. An example illustrates the proposed generic algorithm.

Conditions for existence of observer-based faults detection and isolation systems for continuous linear descriptor systems are presented. These conditions are associated, in a first phase, to the solution of a generalized Sylvester equation and, in a second phase, to the solution of a Sylvester equation under a constraint that describes the faults decoupling of the corresponding estimation error. Two observer structures are used to residual generation and faults reconstruction/isolation, respectively. The proposed results put in evidence some degrees of freedom that can be used for design purposes. Thus, an eigenstructure assignment algorithm to design the FDI system and a illustrative example are presented.

Linear matrix inequality (LMI) conditions are given for the computation of H ∞ guaranteed costs for neutral systems with time-varying delay in the state vector. All the system matrices are supposed to be uncertain and time-invariant, belonging to a polytope with known vertices. The H ∞ guaranteed costs are assured by means of a parameter- dependent Lyapunov-Krasovskii functional providing less conservative results than those available in the literature in the context of delay independent conditions. LMI conditions for special cases such as delay free systems and retarded systems with time-varying delays can be obtained from the proposed conditions by congruence transformations.

Conditions for the existence of disturbance decoupled minimal-order observers for a class of descriptor systems are presented. Basically, these conditions are associated to the solution of a generalized Sylvester equation under a constraint that describes the disturbance decoupling of the estimated state. Thus, under some structural conditions of the considered descriptor system, a sequence of coordinate transformation allows to define a reduced-order normal system. Both eigenstructure assignment and regional pole placement techniques can be applied to solve the constrained reduced-order Sylvester equation. For regional pole placement, a LMI technique is proposed and a illustrative numerical example i reported.

This paper addresses the problem of controlling a continuous-time linear system subject to actuator saturations and to L 2 -bounded disturbances. We propose LMI conditions that allow to design a state feedback saturating control law in order to satisfy the closed-loop Input-to-State stability (ISS). By considering a quadratic candidate Lyapunov function, two particular tools are used to derive the LMI conditions: a modified sector condition , which encompasses the classical sector-nonlinearity condition considered in previous works, and Finsler’s Lemma , which allows to derive stabilization conditions which are potentially adapted to be cast into multiple objective control optimization problems. Relative to a previous work which proposed BMI conditions for treating a similar problem, the given LMI conditions allow to propose a more efficient convex programming design technique.

Although published in the first part of the twentieth century, Finsler's Lemma has shown to be a very attractive mathematical tool to treat stability of linear systems only recently. It is shown in this paper how this tool may be used to reformulate delay-independent stability conditions for neutral linear time-delay systems. The conditions allow, in particular, to construct parameter-dependent Lyapunov-Krasovskii functions for uncertain polytopic neutral systems. Extensions to stabilization problems can also be derived.

This paper presents a robustness analysis of the Dynamic Matrix Controller (DMC) for dead-time processes. The study considers a wide class of industrial processes, those that can be modeled by a first order transfer function with a dead-time. The analysis shows that DMC can be described using a predictor plus a primary control structure. This description allows to analyze the effect of the dead-time in the robustness of DMC. The results are illustrated with some simulations that compare DMC to the Generalized Predictive Controller (GPC).