Nanopositioning with multiple sensors: MISO control and inherent sensor fusion

There is a strong motivation for using multiple sensors for feedback control in ultrahigh accuracy data storage devices such as a probe-based data storage device. One elegant way to design such controllers using multiple sensors is to design a direct multi-input-single-output (MISO) controller using either the H2 or H∞ control design paradigm. In this paper we discuss the control of a micro-scanner used in a probe-based data storage device. Two sensors, a global position sensor and medium derived positional information, are employed simultaneously. MISO controllers are designed to obtain the desired frequency separation in closed loop performance. These controllers are investigated in detail to understand their underlying structure and the inherent sensor fusion that takes place during the control. Comparisons are made with conventional Kalman filtering and H∞ filtering problems.