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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).

This paper presents H/sub /spl infin// and H/sub 2/ techniques for the design of a certain class of prefilters. In order to avoid high order prefilters we use a particular structure in which both prefilter and feedback controller share the same dynamics. The suboptimal H/sub /spl infin// design problem is shown to be equivalent to a linear matrix inequality (LMI) constraint, and the solution of the H/sub 2/ optimal design may be obtained by a simple formula. The H/sub 2/ technique developed is illustrated on a helicopter example and compared with classical techniques.

International audience; The paper addresses the control problem of discrete-time switching systems subject to modal nonlinearities satisfying sector conditions and to saturating actuators. Such a switching system consists of a nite family of dierence processes that is supervised by logical decisionmaking algorithms. Conditions based on LMIs are provided to obtain regions of absolute $\lambda$-contractivity as large as possible. An illustration is presented to enlight the relevance of the proposed approach.

In this paper, a trajectory tracking control for a nonholonomic mobile robot by the integration of a kinematic controller and neural dynamic controller is investigated, where the wheel actuator (e.g., dc motor) dynamics is integrated with mobile robot dynamics and kinematics so that the actuator input voltages are the control inputs. The proposed neural dynamic controller (PNDC), based on the sliding mode theory, is applied to compensate the mobile robot dynamics, bounded unknown disturbances, and influence of payload. This controller is obtained by modeling the Radial Basis Functions Neural Networks (RBFNNs) of the centripetal and Coriolis matrix through of the inertia matrix of the mobile robot dynamics. Thus, PNDC is constituted of static RBFNNs only, what makes possible the reduction of the size of the RBFNNs, of the computational load and the implementation in real time. Stability analysis and numerical simulations are provided to show the effectiveness of the PNDC.

In this paper a methodology to the analysis of bifurcations of variable structure systems is proposed. This methodology, based on the use of symbolic computation packages, is derived from the conditions of the existence of variable structure bifurcations of planar systems, allowing a multi-parametric analysis, without intensive numeric computations. The proposal is applied to a predator-prey model with human intervention.

This paper deals with the control problem of linear stabilizable systems under linear symmetrical input constraints using output feedback control law. The basic idea consists of extending the problem to the case of static output feedback, the partial eigenstructure assignment used in the case of full-state feedback invariant controllers. A static output feedback is realized when the number of unstable eigenvalues of the open-loop system is less than the number of outputs. The methodology allows one to determine some suitable positively invariant sets of admissible initial states. An application illustrates the results.

In this paper is done the experimental identification of friction parameters in LuGre model using the two degree of freedom controllers (TDOF). With identified parameters, friction compensation is implemented in SCARA industrial robot. For friction compensation is used a velocity observer. Controllers and friction compensation are implemented using the real time language XO/2. Analyses of experimental results for low velocities are presented.

The problem of local stabilization of linear continuous-time descriptor systems subject to saturating controls is addressed. The saturated closed-loop system is locally described as a polytopic model. The method of synthesis via generalized Riccati or Lyapunov equations consists in determining simultaneously a state feedback control law and an associated domain of safe admissible states for which the asymptotic stability and the absence of impulsive behavior for the closed-loop system are guaranteed, when control saturations effectively occur.

Considers linear discrete-time singular systems with state constraints and subject to constrained additive disturbances. The objective consists in determining the maximal admissible set of initial conditions for which the resulting motions of the system satisfy the state constraints for all admissible disturbances. Due to the specificities of singular systems in terms of initial conditions (consistent or not), the notions of maximal weak, strong and strict admissible sets are defined.

In this paper we present a biconvex programming approach for the design of output feedback controllers for discrete-time systems. The method is based on necessary and sufficient conditions for the existence of stabilizing static output feedback controllers. An interesting feature of the solution is that the matrix of output feedback gains is given explicitly. Then, we show how convex design constraints can be incorporated in the proposed design approach. Mixed frequency and time domain specifications for the closed-loop system like H/sub /spl infin// performance requirements and state constraints in the presence of disturbances are considered.

The stabilization of linear constrained discrete-time systems via minimal-order observer is addressed. The problem of local stabilization is considered. From a state feedback control law guaranteeing the positive invariance and the asymptotic stability of a certain domain D/sub 1/, the influence of the estimation error is analyzed in terms of the linear control trajectory. The observer design considering the minimization of the influence of the estimation error is also studied.

Linear matrix inequality conditions are given for the robust stability of neutral systems with time-varying delays in the state vector. All the system matrices are supposed to be time-invariant, belonging to a known polytope. The robust stability is assured by means of a parameter-dependent Lyapunov-Krasovskii functional, independently of the size of the time-varying delays. A numerical example illustrates the results.