Control of a 4 DoF Barrett WAM robot — Modeling, control synthesis and experimental validation

Abstract

Precise model based control of robotic manipulators necessitates the requirement of an accurate model of the robotic system. The main contribution of this work is the development of a dynamic model for a 4 Degree of Freedom (DoF) Barrett Whole Arm Manipulator (WAM), and its validation through rigorous experimentation. The nominal model of the system has been developed using the recursive Newton-Euler technique. The accuracy of the model so developed is analysed by performing several trajectory tracking experiments (in the joint space) using two popular nonlinear control strategies-Backstepping and Sliding Mode. While several papers have addressed the trajectory tracking problem in simulation studies on two link planar rigid manipulators, the differences existing between the nominal model and the real model, owing to friction and other unmodeled dynamic terms, make experimental validation a challenging task. We present a detailed comparative study of the two control techniques, and through the precision achieved in our experiments, we validate the developed model.