Abstract
In this paper an indirect approach to the variable structure model reference adaptive control (VS-MRAC) is proposed. This approach is applied to the speed control of a three-phase induction motor. In the direct approach, the switching laws are designed for the parameters of the controller, and in this case the main difficulty is to find the bounds which must be used in the control laws. On the other hand, in the indirect approach, the switching laws are designed for the plant parameters, which are uncertain, but their bounds can be easily found, since they are related to physical parameters of the system. The idea is to design an indirect variable structure approach and to apply it to the speed control of a three-phase induction motor.

Abstract
This paper presents a Variable Structure Adaptive Backstepping Controller (VS-ABC) for linear plants with arbitrary relative degree, using only input/output measurements. In order to improve the transient response, switching laws are proposed in the adaptive backstepping approach via modular design, instead of the integral adaptive laws. Furthermore, simplified algorithms are presented for the VS-ABC, motivating applications on industrial environments. Simulation results for an unstable system with relative degree three are shown.

Abstract
This paper presents the stability and robustness analysis of an indirect adaptive control based variable structure algorithm for uncertain plants with relative degree one. The indirect approach has been proposed as a way to get an easier design of the switching laws, compared to the direct relationship between the plant transfer function parameters and the physical parameters of the system. Here, a singular perturbation approach is used to establish the robustness of the controller in the presence of unmodelled dynamics and disturbances. It is shown that, for sufficiently small parasitics, the system remains stable with respect to some small residual set.

Abstract
This paper presents a robust output feedback controller based on sliding modes and indirect adaptive control applied to the angular shaft speed control of a three-phase induction motor. This approach has remarkable stability properties and offers a straightforward and intuitive tuning of its parameters. Moreover, a simplified version of the algorithm, named compact indirect variable structure model reference adaptive control (CIVS-MRAC), provides not only an easy design procedure, but also a computational implementation of low complexity, thus motivating its application in industrial environments.

Abstract

Abstract