Low-order feedforward control schemes for flexible motion systems with different rigid-body damping

Lightweight stages are becoming the new trend in industrial high performance motion systems. They are generally less stiff than the traditional designs and more pronounced resonant dynamics usually appear in low frequency region. Control design methods to deal with these flexible modes effectively are known as the Beyond Rigid Body (BRB) control. In high performance tracking control, such as wafer scanning and lithography, feedforward control is widely used to improve their tracking accuracy. In this paper, novel feedforward controllers are proposed to reduce tracking error of light-weight motion systems with presence of different rigid-body damping. Their performances are then compared with the traditional rigid body feedforward controller as well as the recently proposed snap feedforward controller to show the advantages.