Nonlinear robust control method for active vibration isolation using a Stewart platform

This paper focuses on developing a nonlinear robust controller to solve the active vibration isolation problem using a Stewart platform. The dynamics of the Stewart platform driven by voice coil actuators is derived by the Newton-Euler method. The influence factors of vibration isolation are taken into account, such as the nonlinear characteristics of the dynamic model, the parameter perturbation and the unmodeled dynamics, etc. The favorable feature of the proposed controller is that it is not necessary for the upper bound of the unmatched uncertainties to be known in advance. A tuning rule is designed to deal with the estimation problem of the uncertainties. The uniformly ultimately bounded (UUB) stability of the controller is demonstrated by applying the Lyapunov approach and a UUB lemma. The simulation results illustrate that the controller can effectively attenuate low frequency vibrations in all six degrees of freedom (DOFs) and the satisfactory vibration isolation performance can be achieved.