Feedback control implementation for AFM contact-mode scanner

The atomic force microscope (AFM) has become a standard technique to measure the topography properties of sample surfaces with nanometer resolution. And the AFM tip based Nano manipulation system plays an important role in the field of Nano research. However, nearly all the systems are designed in the commercial AFM machine, in which the software and hardware is not open to perform the Nano manipulation related research. This paper describes a feedback control system implementation for AFM contact-mode scanner, as part of work in building a Nano manipulation system. With PSD sensor and piezoceramic driver, we designed an embedded control system to fulfill the scanning experiments. The imaging results of silicon steps using regular PED feedback control scheme show that the scanning performance is limited by the inherent piezoelectric actuator nonlinear characteristics. In order to achieve better scanning image, we add a Preisach model based feedforward loop into the PED feedback controller to compensate for the hysteresis effect of the piezoceramic actuator, and the performance has been improved moderately. This AFM platform will be used as a testbed for future research work and experiments on AFM scan and manipulation.