Model-based feedforward for inferential motion systems, with application to a prototype lightweight motion system

In high-performance motion systems, e.g. wafer-stages or pick-and-place machines, there is an increasing demand for higher throughput and accuracy. In the current design paradigm, i.e. rigid-body design, higher demands for throughput and accuracy will lead to a heavier machine. This paradigm does not scale anymore with higher throughputs, i.e. a new paradigm is required. The new paradigm is to design a lightweight machine and to deal with the resulting flexibilities by over-actuation and over-sensing. This class of systems offers freedom to explore new control strategies that exploit the over-actuation and -sensing. This paper presents a model-based feedforward method for over-actuated flexible motions systems, with non-collocated sensor and performance locations. Inferential control is considered as the point of interest for performance is typically different from the location of the measured feedback signals.