Robust sliding-mode controller design for a Stewart platform

The focus is on robust sliding-mode control design for regulation control of a Stewart platform with uncertain dynamics in presence of nonlinearities. The position and velocities are the major feedback to the controller. First of all a sliding surface s ∈ R⁶, composed of system states vectors, is chosen. Then actual payload's mass uncertainties are used to calculate the upper bounds of perturbation in the Lyapunov sense and then these estimates are used as reachabilty gains to eliminate the uncertain dynamics of the system. It leads us to a control law which guarantees global asymptotic and exponential convergence. In the last a boundary layer is introduced to provide a chatter-free control. The control performance of the proposed algorithm is verified by computer simulations. These simulations show that system follows the desired trajectory and errors converge to equilibrium points efficiently.