In atomic force microscopy (AFM) the imaging speed is strongly limited by the bandwidth of the feedback loop that controls the interaction between the measurement tip and the sample. A significant increase in closed-loop bandwidth can be achieved by combining a long-range, low-bandwidth actuator with a short-range, high-bandwidth actuator, forming a dual actuated system. This contribution discusses the design of a model-based feedback controller that controls the tip-sample interaction in dual actuated AFM. In order to guarantee closed-loop stability, the dynamic uncertainties of the system are identified and taken into account in the controller design. Two different design cases are discussed, showing the trade-off between the positioning range at lower frequencies and the positioning range at higher frequencies. The designed feedback controller is implemented on the prototype AFM system and demonstrates a disturbance rejection bandwidth of 20 kHz.
5th IFAC Symposium on Mechatronic Systems. Proceedings of the 5th IFAC Symposium on Mechatronic Systems (Cambridge, MA September 13-15, 2010) p. 220-226