Compact high performance hybrid reluctance actuated fast steering mirror system

This work presents the design, analysis, control and evaluation of a novel compact and highly integrated fast steering mirror (FSM) system, which is based on a hybrid reluctance tip/tilt actuator. The actuator design employs a permanent magnet for biasing the magnet circuit with a constant flux and two pairs of coils to generate a steering flux for rotating the mover around the two system axes. The system, designed to be used as scanning unit in compact optical metrology systems, uses a custom made eddy current sensor system for position measurement and a titanium flexure, which compensates the negative actuator stiffness, for suspending the mover. The FSM provides a mechanical angular range of +/- 3 degrees ( +/- 52.4 mrad) and a small signal closed-loop bandwidth of 1.5 kHz in the tip and tilt axis, has a small diameter of 32 mm and a system height of only 30 mm. Compared to a state-of-the-art hybrid reluctance actuated FSM system the volume of the system is reduced by one order of magnitude, while the product of range times bandwidth, representing a measure for the system performance, is concurrently improved by 50%.