Feedforward for flexible systems with time-varying performance locations

Increasing demands for higher throughput in high-performance motion systems, e.g. waferstages or pick-and-place machines, lead to more aggressive motion profiles (higher accelerations), a stiffer design and/or larger wafer sizes (higher mass). Therefore, larger actuation forces are required, which puts stricter demands on actuators, amplifiers and cooling. However, this design paradigm has reached the boundary of its scalability. Therefore, the next generation of high-performance motion systems are designed to be lightweight. For this class of systems the location where the tool operates, e.g. the area to be exposed or component to be placed, is constantly varying. Due to the lightweight design and the changing position of the performance output location, the system dynamics to be considered for feedforward are changing as well, i.e. the flexible modes are observed differently. This paper presents a model-based feedforward method for flexible systems with time-varying performance locations. This method is experimentally validated on a two-mass setup with flexible shaft.