A Super-responsive Tip-Tilt Motion Control of a Mirror Driven by Electromagnetic Force and Supported by an Elastic Rod Made of Super Elastic Alloy

Fast steering mirrors (FSMs), which are mounted on observation satellites to realize a shake correcting function, are required to have large aperture, high responsivity and multi control axes. This paper presents a tip-tilt motion controlled FSM having an 80 mm diameter mirror driven by four compact voice coil motors and supported by an elastic rod made of super elastic alloy called GUMMETAL®. Four rubber dampers are also attached to the mirror to suppress an unexpected low-frequency vibrational mode. To evaluate the effect of the elastic rod and rubber dampers on the static and dynamic performance, tip-tilt range and open-loop frequency responses of the FSM were measured with or without dampers. Each PID controller for tip-tilt and axial motion was designed based on the FSM dynamic model. The control result showed that the bandwidth of more than 2,500 Hz in the tip-tilt direction was achieved suppressing the low-frequency vibrational mode.