Frequency Based Combination Control Strategy for AFMs

This paper analyzes the relationship between the resonant phenomenon of piezo-scanner and the control system bandwidth in an atomic force microscopy system (AFMs). Based on the results, a novel frequency based combination control strategy is proposed and then implemented with the currently utilized proportional-integral (PI) controller in Z-axis for AFMs. That is, the regulation error is separated into two parts of high frequency content and low frequency content, for which two different controllers are designed to generate two auxiliary control signals, which are then synthesized to actuate the piezo-scanner to improve the performance of AFMs. The designed strategy is analyzed in frequency domain to show that it provides much enhancement for control system bandwidth, and the conclusion is verified by both simulation and experimental results, demonstrating that superior imaging performance for high-speed scanning tasks can be obtained by the proposed combination control strategy.