Dynamic modeling and robust passivity-based control of a cable-suspended robot

The level adjustment of cable-driven parallel mechanism is challenging due to the difficulty in obtaining an accurate mathematical model and the fact that different sources of uncertainties and disturbances exist in the adjustment process. This paper presents application of a robust passivity-based control scheme for a cable suspended robot to handle disturbances and uncertainties in mass and moments of inertia of end effecter. In section II dynamic equations of motion are derived by using Newton-Euler method and the constraints are utilized to obtain the complete required equations. In section III inverse dynamic and robust passivity-based controllers are presented. Lyapunov function presented in this section defines additional control input and shows the stability of robust passivity-based controller. Simulation results presented in section IV for non-redundant cable-based robots show the effectiveness of the robust passivity-based controller when there is no enough knowledge about system parameters and in the presence of a sinusoidal disturbance.