Sliding mode fuzzy control

Fuzzy controllers work like modified sliding mode controllers (SMCs). Compared to ordinary SMCs, fuzzy controllers (FCs) have the advantage of higher robustness. The structure of a FC is derived from a nonlinear state equation representing a large class of physical systems. The following aspects are discussed: stability conditions, scaling of the state vector, choice of the switching line, and determination of the break frequencies of the controller. By the choice of an additional boundary layer in the phase plane the FC is modified so that drastic changes of the manipulated variable can be avoided, especially at the boundary of the normalized phase plane. In this context, the higher robustness of the modified FC over the modified SMC is discussed. An FC for a higher-order system is proposed