Abstract
The authors have been developing the tracking control system of the scanning tunneling microscope tip along the crystalline lattice on HOPG surface to achieve a real-time atomic encoder using crystalline lattice as reference scale. In order to overcome acoustic and vibration disturbances and then extend the tracking range to micrometer, a new control method is employed. The new PI controller consists of two PI control units. Each of them is tuned for the acoustic noise of high frequency and the vibration of low frequency, respectively. By varying the amplitude and the frequency of disturbance which applied directly to the STM as parameters, critical boundary areas in relationship-charts between the amplitude and the frequency are made for both the new proposed and conventional PI controllers. The experimental results show that the new proposed controller has the robustness higher than the conventional one. The stabilized tracking control of the STM tip along crystalline lattice on crystalline surface using the new proposed PI controller can be utilized to extend the control range upto micrometer range.
