Nonlinearities Compensation Method for Application to Robot Manipulators Using Time-Delay Estimation

Abstract

The challenging and difficult issue in controlling multi-joint robot manipulators is high nonlinearity, strong coupling, and payload gravity in the system dynamics of the manipulator. This paper proposes a straightforward approach for motion control applied to robot manipulators using the nonsingular terminal sliding mode control design working together with time-delay estimation technique (TDE). In this approach, each joint actuator is considered as a free-inertia system without modeling nonlinear terms such as dynamic couplings, Coulomb friction, and gravitational payload thanks to the TDE. Implementation of the proposed control scheme is simple because it does not need to calculate the highly complicated dynamic equations of the robot. In this sense, this technique does not require the exact model of the joint actuator. Despite its simplicity, the proposed control scheme provides high-precision control and robustness against parameter variations. Experiments are implemented on a 2-DOF robot arm to verify the simplicity and feasibility of the proposed scheme, and the results are compared to those of the tuned PID controller. The results reveal that the proposed control scheme is realistic and simple for applying on practical robot manipulators.