Compensação de atrito no controle de sistemas mecânicos: uma abordagem utilizando estratégias inteligentes

Abstract

Friction can be found in almost all mechanical systems. In many cases, however, it is undesirable and has to be minimized and/or compensated. Besides of speeding up the wear of its components, friction is strongly associated with the nonlinear behavior of a mechanical system. It should also be noted that when the system has to be controlled, friction hampers the achievement of an efficient control law, due to its nonlinear feature and the issues related to the development of a mathematical model that accurately describes it. In this context, based on an adaptive sliding mode control approach, this work presents the development of a friction identification/control strategy. In addition to the ability to compensate for friction, the proposed control scheme an also cope with other unmodeled dynamics. The proposed strategy is able to identify the dynamics of the plant as well as its variation due to changes in friction characteristics. Moreover, the proposed scheme can also indicate the precise moment that friction’s variation occurs. The following contributions should be highlighted: (i) the introduction of a unifying approach, capable of combining different algorithms of computational intelligence; (ii) the development of a new adaptation scheme that reduces the computational complexity of the adjustment method; (iii) an index related to friction variation, which is based on the real-time evaluation of the approximate model of the system; (iv) an intelligent sliding mode controller that does not require prior knowledge of the dynamics of the plant and can retain its performance even when there are significant changes in operating conditions. The stability of the proposed intelligent controller is demonstrated by means of a Lyapunov-like analysis. The efficacy of the designed control scheme is evaluated by means of both numerical and experimental studies with electro-hydraulic actuated system.