Internal reference model based optimal LQG controller for atomic force microscope

This paper presents a design of an internal reference model based optimal linear quadratic Gaussian controller (LQG) for a piezoelectric tube (PZT) actuator used in the atomic force microscope (AFM). This control scheme minimizes the steady-state error and provides improved closed-loop bandwidth and enables the controller to track reference triangular signal. The proposed scheme places the closed-loop poles in the left half of the s-plane such that significant damping of the resonant modes of the PZT actuator can be achieved. Experimental results with the AFM show that the proposed control approach is able to scan faster and improves the quality of images by minimizing blurring, tilting, and edge distortion of the image as compared to the existing PI controller of the AFM.