Output integral sliding mode control to stabilize position of a Stewart platform

The problem of the realization of integral sliding mode controllers, based only on output information, is applied to a Stewart platform. This platform has three degrees of freedom and it is used as a remote surveillance devise. We consider the hierarchical sliding mode observer, allowing the reconstruction of the system states from the initial moment if we suppose that there exist ideal sliding modes and equivalent output injections. This allows the implementation of an output integral sliding mode controller ensuring the insensitivity of the state trajectory with respect to the matched uncertainties from the initial moment. The discrete realization output integral sliding mode controller requires the filtration to obtain the equivalent output injections. It is shown that the observation error can be made arbitrarily small after an arbitrary small time without any adjustment of the observer parameters, only by decreasing the sampling step and filter time constant. The results obtained are illustrated by simulations.