Trajectory tracking of frictional direct-drive motors using fuzzy-linear-model-based robust variable structure control

First, a one-degree-of-freedom of the frictional direct-drive motor is approximated by nine linear state-space dynamic subsystems obtained by the local linearization about the operating point. Then the same fuzzy sets of the system rule are applied to design the fuzzy-linear-model-based robust variable structure control, including a fuzzy equivalent control and fuzzy switching control. The fuzzy equivalent control is designed to obtain the desired control behavior. The fuzzy switching control is applied to tackle the uncertainty caused by the approximation error of fuzzy-model and the interaction dynamics resulting from the other subsystems. The proposed control does not require the solution of linear matrix inequalities for obtaining a common positive definite matrix to ensure the stability of the closed-loop system. The simulations are also presented to confirm the usefulness of the proposed control