A novel adaptive rejection control approach for multiple narrow-band disturbances in nano-manipulating systems

This paper presents an innovative method for rejecting multiple narrow-band disturbances in nano-manipulating servo systems. The proposed control scheme consists of a robust controller and a multiple optimal phase filter structure. The baseline robust controller is synthesized with mixed sensitivity optimization for the purpose of robust stability and servo performance. A novel adaptive digital multiple optimal phase filter structure is then developed with a parallel connection, such that online estimation and suppression of the narrow-band disturbances with unknown or time-varying frequencies can be achieved without sacrificing the stability robustness of the closed-loop systems. The proposed control scheme is evaluated via simulations and implemented on a piezoelectric-actuator driven nanopositioner, where high precision positioning is demonstrated in the presence of both unmodeled dynamics and multiple disturbances.