适用于AFM的数字智能反馈控制器设计

Design of the digital intelligent feedback system applied to AFM

原子力显微镜(AFM)是进行纳米测量和操作的一种重要工具。近年来,纳米科技的迅速发展使得传统AFM越来越无法满足纳米测量快速和高分辨率的测试需求,而反馈控制器的速度是限制AFM成像速度和分辨率的关键因素之一。为此,本文搭建基于高速数字信号处理器(DSP)的数字反馈控制系统,将模糊控制算法与比例积分PI控制算法结合,利用模糊规则自动选择合适的比例和积分参数,改善Z向反馈系统的鲁棒性。基于自制的AFM系统,将该方法与传统PI控制算法进行对比实验,在相同的扫描条件下,该数字智能反馈控制器可在扫描范围为30μm×30μm时,将AFM的行扫描速度由3 Hz提高到40 Hz,验证了该方法能够有效改善AFM的扫描速度和成像分辨率。

Atomic force microscopy （AFM） is a powerful tool for nano measurement and manipulation. Recently, the conventional AFM cannot satisfy measurement requirements for high speed and high resolution due to the rapid development of the nano science and technology. The bandwidth of the feedback controller is one of the key factors which limits the scanning rate and resolution of AFM. Thus the paper proposes a digital feedback controller based on the high-speed digital signal processor （DSP） , implemented with an intelligent fuzzy proportional integral （PI） control algorithm. Combining the fuzzy controller with the PI controller, the algorithm utilizes the fuzzy rules to select appropriate proportional and integral parameters for the PI controller, resulting in the improvement of the response rate of the z feedback loop. Experiments are carried out on a customed AFM system. Compared with the conventional PI controller, the digital intelligent controller could improve the scanning rate from 3 Hz to 40 Hz with the scanning range of 30 μm × 30μm. The new method is demonstrated to improve scanning speed and the image resolution.