A friction compensation approach of a 6 axis hybrid robot by considering joint inertia change

The feedforward compensation based on friction model is an effective way to reduce the influence of friction on mechanical system. This paper presents an approach for friction compensation by considering the inertia change of the actuated joints of a 6-axis hybrid robot named TriMule. First, the tracking errors of each actuated joint of the parallel mechanism at high and low inertia configurations are displayed. Then, a compensation approach considering inertia change is developed by introducing the inertia term of the joint driving force into the traditional Stribeck model as thrust. Furthermore, the improved approach based on radial basis function interpolation without using the dynamic model is proposed, which has a simple calculation expression and acceptable compensation effect. Experiment results on a prototype machine show that compared to otherwise similar compensation method not considering joint inertia change, the tracking accuracy can be improved up to 25.73% at high inertia configurations.