As part of my coursework for my MSME at UT Austin, I took a modeling/simulation of physical systems course, and a feedback control of systems course. I enjoyed both of these courses very much, and I thought it would be fun to apply those skills for a mini project to reinforce what I have learned. One of the products I worked on at L3Harris SSG was a Fast Steering Mirror (FSM). I always thought it was a fascinating piece of technology and its system components are simple and understandable enough that I thought it would make a good modeling project.
The system is composed several key components:
Mirror
2-axis flexurized hinge
Mirror actuators
Mirror position sensors
Control electronics
The mirror and flexure hinge constitute the ‘plant’ of the system and can easily be modeled as a 2nd order rotational system (for each axis of rotation). The dynamics of this system are modeled above assuming a 3in diameter, .25in thick aluminum mirror, and a flexure mount with 10 .025in x .5in x .05in flexure segments. This yields a mass moment of inertia J = .0014 kg-m^2, a rotational stiffness K of 1.47 N-m/rad, and a damping coefficient B of 9.1e-4 kg-s. I think the challenge of this project will be understanding how to model the dynamics of the actuation and position sensing system.