Model-based spatial feedforward for over-actuated motion systems

In high-performance motion systems, e.g. wafer-stages and pick-and-place machines, there is an increasing demand for higher throughput and accuracy. The rigid-body design paradigm aims at very stiff designs, which lead in an evolutionary way to increasingly heavier systems. Such systems require more and more power, such that this paradigm rapidly approaches the boundary of its scalability. An alternative paradigm is to design a lightweight machine with over-actuation and over-sensing, to deal with the resulting flexibilities. This paper presents a spatial feedforward method for over-actuated flexible motions systems, which aims at reducing the vibrations over the complete flexible structure during motion. The proposed method is experimentally validated on an industrial prototype and compared to mass feedforward and the standard input shaping technique. (C) 2013 Elsevier Ltd. All rights reserved.