The Process of Control Design for the NASA Langley Minimast Structure

The NASA Langley Minimast Facility is an experimental flexible structure designed to emulate future large space structures. The Minimast system consists of a 18 bay, 20 meter-long truss beam structure which is cantilevered at its base from a rigid foundation. It is desired to use active control to attenuate the response of the structure at bay 10 and 18 due to impulse disturbances at bay 9 while minimizing actuator torque commanded from the torque wheel actuators. This paper details the design process used to select sensors for feedback and performance weights on the Minimast facility. Initially, a series of controllers are synthesized using H2 optimal control techniques for the given structural model, a variety of sensor locations and performance criteria to determine the "best" displacement sensor and/or accelerometers to be used for feedback. Upon selection of the sensors, controllers are formulated to determine the affect of using a reduced order model of the Minimast structure instead of the higher order structural analysis model for control design and the relationship between the actuator torque level and the closed-loop performance. Based on this information, controllers are designed using ¿-synthesis techniques and implemented on the Minimast structure. Results of the implementation of these controllers on the Minimast experimental facility are presented.