Smooth variable structure observer controller with adaptive gains: Application to robot manipulators control

In this paper, an observer based controller is developed, both of them working in sliding mode, applied to the square MIMO non-linear systems control. An application to the rigid robots with n links and n revolute joints (n-degree of freedom) is presented. In order to reduce the chattering, a parameterised smooth switching function is used: the tangent hyperbolic function both in the observer and controller. The gain of the switching functions is adaptively updated, depending on the state estimation error and tracking error, respectively. Using the adaptive gains, the transient and tracking response are improved. Closed loop simulations with a 2-degree of freedom robot manipulator, in the presence of parameter uncertainties, are presented in order to show the robustness of the approach.