Disturbance observer estimating frictions and external forces for robot manipulators

This paper presents a novel nonlinear disturbance observer for robot manipulators in which the disturbance consists of frictions in joints and external forces exerting on a link. The method permits to estimate the frictions and the external forces separately without of measurement of joint accelerations. Global exponential convergence of the estimated disturbances to the true values is proven based on the Lyapunov theory. Computational simulation is presented for a 2 link robot manipulator to show the effectiveness of the proposed disturbance observer.