Control system design for stability and precise positioning of atomic force microscopy probe

An atomic force microscopy (AFM) operates by moving the platform to put its probe on the sample surface for measurement or processing. One of its greatest drawbacks is longer waiting time for vibrations to settle and so that the task can be operated. This study investigates the modeling and control of AFM's probe in order to achieve stability and precise positioning for the probe without generating any overshoot. First, dynamic equation and boundary conditions are obtained by using Hamilton's principle. Then, the Laplace transform is applied to get open-loop transfer function and the corresponding poles and zeros' pattern is found. The root-locus is employed to design the controllers, and the performance of the control system is simulated by using mode summation method. The result shows that the designed controller not only stabilizes an infinite number of modes, but also can achieve good tracking without generating any overshoot. This indicates that the controller is both practicable and robust. The application of AFM technology has the potential of making major contribution in the fields of the materials science, biotechnology, mechanical properties of nanostructure, and the nano-machining.