Fuzzy adaptive VSC systems

To design robust control systems, Variable Structure Control (VSC) is one of the modern control methods that could be used. This method is implemented using a discontinuous type control which usually includes linear feedback terms and signum terms. The signum terms are used to neutralize the effects of general perturbations in the system. It is well known in the theory of VSC that large magnitude signum terms increase the amplitude of chattering which exists in VSC systems with time delays in their switching mechanism. This study proposes a new approach to achieve low chattering in a VSC system.

In this study, the suggested approach is to implement fuzzy adaptive algorithms to the reaching and sliding modes of a VSC system to reduce chattering. The approach incorporates an adaptive adjustment mechanism and a fuzzy decision mechanism into the VSC system. Two fuzzy adaptive algorithms are used, one provides a VSC on demand feature and the other reduces the chattering of the state variables caused by switching delay. The result is a low chattering robust VSC system without compromising the robustness property of the system.