M. Velasco-Villa

The disturbance decoupling problem for time-delay nonlinear systems

In this paper, the disturbance decoupling problem (DDP) for a class of SISO nonlinear systems with multiple delays in the input and the state is studied. A pioneering mathematical approach is introduced for this class of systems and is claimed to be the cornerstone of the problem. Necessary and sufficient conditions are given for the existence of a bicausal feedback that solves the DDP. Sufficient conditions for the existence of a solution within other classes of compensators are included as well.

Discrete-time sliding mode path-tracking control for a wheeled mobile robot

In this work, it is presented a discrete time control strategy for the solution of the path-tracking problem for a wheeled mobile robot of the type (2,0). It is assumed that the mobile robot is remotely controlled over a communication network that induces a transport delay. The exact discrete-time model of the mobile robot including the induced delay is developed. It is presented a discrete-time strategy control based on a sliding mode approach that allows to solve the path-tracking problem. The closed loop stability of the overall system is clearly stated. The proposed control strategy is evaluated by mean of computer simulation

GLOBAL PATH-TRACKING FOR A MULTI-STEERED GENERAL N-TRAILER

Abstract A multi-steered general n-trailer is considered in this work. A global path-tracking control strategy for the n-trailer is proposed. Three nonlinear control laws are used to solve the problem by means of a commutation scheme. This commutation scheme allows to avoid the singularities inherent to a feedback linearization scheme. Simulation results show that the proposed scheme has good performance.

Observability and observers for nonlinear systems with time delays 1

Basic properties on linearization by output injection are investigated in this paper. A special structure is sought which is linear up to a suitable output injection and under a suitable change of coordinates. It is shown how an observer may be designed using theory available for linear time delay systems.

Passivity-based control of switched reluctance motors with nonlinear magnetic circuits

In this paper, the torque/speed/position tracking control problem of switched reluctance motors is approached from a passivity-based control perspective. The main characteristics of the presented result are: it belongs to the class of control schemes that take into account the saturation effects present in stator windings and, regarding torque generation, it considers the use of sharing functions. The contribution of the paper is threefold: The controller design is developed using energy-dissipation ideas, the mathematical formalization of the current engineering practice of controlling this kind of machines with a cascade approach, and an extension to previously reported passivity-based controllers for electric machines in the sense that Blondel-Park transformability properties are not required.

Trajectory Tracking for aWheeled Mobile Robot Using a Vision Based Positioning System and an Attitude Observer

The trajectory tracking problem for a wheeled mobile robot is addressed and solved by means of a partial state feedback strategy based on measurements from an indoor vision based absolute positioning system. The Cartesian coordinates provided by the localization system are fed to the proposed observer in order to estimate the orientation of the vehicle. It is shown that the combination of a classical dynamic full information controller with an asymptotically convergent vehicle attitude observer, designed using the immersion and invariance technique, yields a locally asymptotically stable closed-loop system. Real time experiments show the performance of the proposed control scheme.

Path-Tracking Dynamic Model Based Control of an Omnidirectional Mobile Robot

Abstract Considering the dynamic model of an omnidirectional mobile robot (also known of a type (3,0)), in this work is addressed the Path-tracking control problem of this class of systems. The solution of the problem is obtained by considering some suitable modifications of the well known computed-torque control strategy usually used on the field of robot manipulators. The modifications considered in this work are due to the structural differences between a mobile robot and a classical rigid robot manipulator. It is formally proved that the proposed control strategy allows the convergence of the tracking errors and assures the closed loop stability of the system. The tracking strategy is evaluated by simulation, showing an acceptable performance.

Bi-causal solutions to the disturbance decoupling problem for time-delay nonlinear systems

In this paper, the disturbance decoupling problem for a class of single-input single-output nonlinear systems with multiple delays in the input and the state is studied. Based on a pioneering mathematical frame, a bicausal compensator that solves the problem is considered, giving necessary and sufficient conditions for the existence of such a compensator.

On the Control of Unstable First Order Linear Systems with Large Time Lag: Observer Based Approach

This work considers the problem of stabilization and control of a class of unstable first order linear systems subject to a relatively large input–output delay. As a first step, the conditions to ensure the stability of the system in closed loop with an output injection strategy are presented. In a second step, the stability conditions are used to design an observer-based scheme that provides a forward output estimation together with a feedback compensation to guarantee prediction convergence. The robustness of the overall observer-based strategy is analyzed when considering uncertainties on the magnitude of the time delay associated with the plant and the one considered on the design of the observer. A stability region as a function of these two time delays is obtained. The proposed prediction scheme is complemented by the use of a PI compensator to track step reference signals and to reject step disturbances.

Discrete-Time Control of an Omnidireccional Mobile Robot Subject to Transport Delay

This paper deals with the discrete time control of an omnidirectional mobile robot subject to transport delays. A discrete-time model of the vehicle is obtained by considering an exact discretization of the continuous time model of the robot where the time delay induced by the communication network is previously considered. Instead of the original continuous-time delay system, a discrete-time model free of delay for which the consideration of a classical control strategy is possible. It is shown that the stability of the system is assured under the proposed strategy.