Improved high frequency bandwidth magnetic Fast Steering Mirror for free space optical communication using model-based control

Fast Steering Mirrors (FSM) play a crucial role in both optical communication and space imagery, serving a wide range of functions such as Point Ahead Mechanisms (PAM), Raster Scanning, Beam Steering Mirrors (BSM), Fine Pointing Mechanisms (FPM), and Line of Sight stabilization (LOS). The need for static and dynamic precision control is growing rapidly. Thus, the quality of an image obtained with optical instrumentation, a camera or a telescope is very dependent on the stability obtained at the heart of the optical chain. The control gives the system its final value: the impact of control on accuracy and bandwidth is often considerable. With a substantially identical mechanism, an advanced control makes it possible to provide from 4/3 to 4 times more bandwidth and precision than a simple PID control.
This paper presents the current development in control capabilities of the entire system. The analysis and the results are provided for the Magnetic Fast Steering Mirror 45 (M-FSM45) which is a Magnetic Fast Sterring Mirror optimized for a stroke of 30 mrad, but can go up to 50 mrad. It is driven by magnetic actuators, supplied by the MCLA18 driver. This electronic is able to supply 1 𝐴 , and up to 32 𝑉 on each one of its two channels. The M-FSM45 is equipped with Eddy Current Probes (ECP) to determine the angle of its mirror on both axes. These probes are conditioned by the ECS45 conditioner (Eddy Current Sensor 45). To complete the test setup, a Software In the Loop (SIL) Speedgoat platform is used both to acquire data and to compute the controller in real time. To acquire the mirror angle and characterise the ECS45, a high-speed autocollimator is used.
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Schematic Test setup of the M-FSM45