Abstract: A nonlinear L₂ robust active vibration isolation control approach is proposed for the active vibration isolation platform based on Stewart parallel mechanism.The entire dynamic model of the vibration isolation platform driven by the linear voice coil motors is developed with Newton-Euler method.Without knowing the upper bound of the unmatched uncertainties of the model,the influence factors of vibration isolation,such as the nonlinear characteristics of the dynamic model,the parameter perturbation and the unmodeled dynamics,are fully taken into account.A tuning rule is designed to estimate the unknown upper bound of the unmatched uncertainties.Moreover,a robust active vibration isolation controller is derived.By constructing appropriate storage functions,the controller stability and the L₂ performance criterion based vibration isolation performance are verified theoretically.The simulation results demonstrate that the controller can effectively attenuate low-frequency vibrations in all six degrees of freedom and the satisfactory vibration isolation performance can be achieved.