Design, identification and control of a fast nanopositioning device

This paper presents the design, identification and control of a nanopositioning device. The device is actuated by a piezoelectric stack and its motion is sensed by a linear variable differential transformer (LVDT). A fourth order single input single output model has been identified to describe its dynamics. It is demonstrated that PI control law does not meet the bandwidth requirements for positioning. This motivated the design and implementation of an H_∞ controller which demonstrates substantial improvements in the positioning speed and precision besides eliminating the undesirable nonlinear effects of the actuator. The characterization of the device in terms of bandwidth, resolution, and repeatability is also shown.