Precision motion control of a manipulator as a step to force control

If a dextrous manipulator could be given the functions of programmed compliance and force reflectance, in addition to the easier functions of programmed motion and teleoperation, then many more remote handling tasks could be performed. This paper briefly describes how one area of manipulator research at ISSL is addressing this problem. It begins by describing two sources of inaccuracy in robot manipulators and goes on to describe how model-based control can be used to improve accuracy for high precision and high speed motions. Although force control typically occurs at very low speeds, the effectiveness of model-based control is shown to be relevant still-but the emphasis is now on the friction modelling. Since a good model is central to this discussion, some aspects of the modelling are described, especially friction effects. Finally, a few preliminary results are given, some principles for improved manipulator design are presented by example and some concluding remarks are made