Parameter Self-turning Fuzzy PID Controller Design for Atomic Force Microscopy in Z-axis

In order to improve the imaging quality of an atomic force microscopy (AFM), it is necessary to improve the control precision for a piezoelectric scanner in z-axis. However, the traditional proportional-integral-derivative (PID) control for an AFNI in z-axis still has some disadvantages, to solve this problem, in this paper, we design a parameter self-turning fuzzy ND controller to replace the traditional one in z-axis, which improves the control performance and the image quality. To be specific, firstly the error between the given voltage value and reflected voltage value is chosen as an input of the fuzzy PID controller, the derivative of this error is calculated as another input of the controller. Afterwards, we fuzzify these two inputs to map the range of inputs to the corresponding domain of discourse, and determine the membership degree functions for inputs and outputs. Then, we complete the fuzzy inference according to the membership degree functions and fuzzy rules base. Through the fuzzy inference, the fuzzy outputs are obtained and further defuzzified to produce the true outputs, which are applied to the ND controller to achieve the parameter self-turning Simulation results demonstrate that this designed fuzzy controller can effectively improve the control effect.