Sliding mode control synthesis using fuzzy logic

In variable structure control algorithms, sliding mode plays a crucial role in making the closed loop system insensitive to modeling uncertainties and external disturbances, and also in transforming the original system dynamics into prescribed reduced order dynamics restricted to a switching manifold on which desired system dynamic behavior is achieved. The control law used to realize the desired sliding mode dynamics is discontinuous on the switching manifold. However, due to imperfections in switching, such as time delays, the system trajectory chatters instead of sliding along the switching manifold. This chattering is undesirable because it may excite unmodeled high-frequency dynamics in the physical system. To overcome this drawback, in this paper, a new sliding mode control algorithm using concepts from fuzzy theory and fuzzy logic is developed. The eccentricity of the new sliding mode control algorithm resides in generalized form of switching manifold which allows for a smooth transition between the reaching mode and the sliding mode. To demonstrate its performance, the proposed control algorithm is applied to a one-degree of freedom robot arm