Nonlinear Disturbance Observer for Robot Manipulators in 3D Space

Abstract

Requirements for fast and accurate motion in industrial robot manipulators demand more advanced control techniques. To meet this problem, several methods have been reported. The Disturbance Observer (DOB) problem has been widely utilized in high-precision and high-speed motion control applications. However, most works done in this area are based on linear control theories even the dynamic of the manipulators are highly nonlinear. In this paper, a nonlinear disturbance observer is proposed for three-DOF robot manipulators operating in 3D space and the stability analysis of the proposed disturbance observer is performed by using Lyapunov’s method. Using this nonlinear disturbance observer, it does not require an accurate dynamic model to achieve high precision motion control. The effectiveness of the proposed observer is investigated by numerical simulation. The results show that controller with nonlinear disturbance observer has more superior tracking performance, with a wide range of payloads and in the presence of friction.KeywordsNonlinear disturbance observerLyapunov’s direct methodcomputed torque method