The topology image of an atomic force microscope is obtained by picking up a controlled output of a force-feedback loop that is proportional to the height of a sample under the assumption that no dynamics in a z-axis actuator exist. However, the dynamic effects such as hysteresis and creep in a PZT driving z-axis actuator cannot be ignored. To solve this problem, a strain-gage sensor is used as an additional sensor, which enables measurement of the absolute displacement of a z-axis PZT nano scanner. The advantage of using an additional sensor is experimentally provided and validated in topology images.
The performance of Atomic Force Microscope depends on the control gains. However, the optimal gains have uncertainties which are impacted by cantilever properties, sample properties and measurement environment. In commercial AFM, it is not easy to get good AFM imaging results since the controller is manually tuned by user. In this paper, auto gain tuning algorithm is suggested for the high performance and automation of AFM. Auto gain tuning algorithm is evaluated by step responses, frequency responses and AFM imaging results.