Cedrat Technologies, innovation in mechatronicsCedrat Technologies, innovation in mechatronics

Cedrat Technologies, innovation in mechatronics

Large stroke fast steering mirror for space free-space optical communication

Free-Space Optics and Deep Space Optical Communication request new compact low-power high-stroke high-bandwidth Fast Steering Mirrors. To address this need, CEDRAT TECHNOLOGIES (CTEC) has developed a Magnetically-actuated Fast Steering Mirror called M-FSM, taking heritage of its MICA™ technology. This mechanism offers Rx Ry strokes larger than +/-2° with a 250Hz bandwidth when tilting a 10mm-diameter mirror. Closed loop control is achieved using integrated eddy current sensors. Requested power is reduced leading to low heating and allowing high duty cycle. Vibration tests allow to define first limits and conditions for the M-FSM to bear external vibrations.

Low-power high-stroke high-bandwidth Fast Steering Mirrors (FSM) are demanded for Freespace optical communication (FSO) in future constellations inter-satellite links as well as in Deep Space Optical  communications (DSOC). For 20 years, CTEC has provided piezoelectricallyactuated Fast or Fine Steering Mirrors (FSM) for space missions (PHARAO, ATLID) and optronics. Currently, CTEC is in charge of delivering the piezo FSM required for PSYCHE DSOC of NASA JPL. These piezo FSM offer a large bandwidth (up to 2kHz) and very fine resolution but strokes below 1°. As such small strokes are constraining for optical and control design according to customers, CTEC has developed a new FSM based on magnetic actuation called M-FSM, targeting larger tilt stroke, typically more than +/-2 mechanical degrees (+/-35mrad), low power, low heating and high bandwidth: 200Hz full stroke and 1kHz at low level.

M-FSM Technology

The most conventional magnetically-actuated FSMs for space rely on Voice Coil Motors generating Lorentz / Laplace forces. Although CTEC manufactures also Voice Coil actuators for space applications, another type of magnetic actuators is selected for the M-FSM: The M-FSM exploits a derivation and an integration of the CTEC MICA™ based on variable reluctance forces to drive a mobile part in Rx and Ry motions in an efficient way. Some FSM have already been designed using variable reluctance forces to provide improvements above Voice Coil but they exploit attraction forces by reducing the air gap thickness leading to some drawbacks: Contact with attracting poles is responsible for strokes limitations and may generate damages, especially under launching vibrations and shocks. Torques that are not constant versus position are complexifying the drive of such devices. CTEC patent-pending M-FSM removes these limitations thanks to a derived MICA concept.