In this paper a new variable structure PID controller is designed for stabilization of robot manipulator systems with parameter perturbations. The sufficient conditions for the existence of a sliding mode is considered. The techniques of matrix norm inequalities are used to cope with robustness issues. Some effective parameter independent conditions are developed in a concise manner for the global asymptotic stability of the multivariable system using LMI’s techniques and principle of Rayleigh’s minmax matrix eigenvalue inequality. The stability conditions are derived by using the Lyapunov full quadratic form for the first time. The parameter perturbations of the robot motion are evaluated by introducing Frobenius norm. Simulation results have shown that the control performance of the robot system is satisfactory. Copyright 2002 IFAC