Analytically and numerically derived H-infinity controller designs for Hubble Space Telescope

Efforts in designing controllers that improve the performance of the Hubble Space Telescope pointing control system in the presence of thermally induced solar array vibration disturbances are presented. The controller redesign provides an excellent opportunity to apply state-of-the-art design techniques to a realistic multi-input, multi-output plant. Available plant models are examined with regard to their utility for controller design and simulation. The performance of existing flight controllers is studied, yielding a redesign philosophy of providing high, broadband controller gain in the frequency ranges where significant disturbance power exists to achieve improved disturbance attenuation. Under this philosophy, a controller is obtained using a standard //oc design approach and an alternative design is accomplished through a numerical search-based algorithm. The new controllers are compared to an existing flight-tested controller via frequency response analysis and through a time-domain simulation that includes vehicle torque limits and an emulation of fixed-point arithmetic effects.