Improved disturbance rejection for high precision systems through estimation of the flexible modes

This paper demonstrates applications of a state observer in high precision control systems that improve low frequency disturbance rejection. By changing the plant transfer function as seen by the feedback controller the effect of flexible modes on the feedback loop is reduced. This allows a redesign of the feedback controller for improved control bandwidth and, consequently, improved low frequency disturbance rejection. Simulation and experimental validation results are presented for the applications to elucidate their (combined) effects.