Modelling and Control of an Articulated Robot with Flexible Links/Joints

A main goal in production lines is to reduce cycle times. As a result the industrial robots should be accelerated. One possibility to gain higher performance is to build lightweight constructions and to allow elastic deformations in joints and links. The upcoming problems such as modeling the elastic deformations and the control of the hybrid system of rigid and flexible parts are the focus of this paper. An articulated robot with 6 joints and 2 flexible links is under examination. For simulation and control purposes the equations of motion are derived using the Projection Equation in subsystem representation. In addition a recursive scheme to evaluate the equations of motion with O(n) efficiency is applied. The control strategy is a combination of feed forward control and a linear PD joint controller. Furthermore the elastic deflections are pre-calculated for the vibration control and to modify the desired track reducing the resulting end point displacement. Measured results are presented to point out the functionality of the proposed control strategy.