Simulation of combined adaptive feedforward and spatio-temporal control of an Earth observing telescope

Abstract

An active vibration control method incorporating a spatio-temporal filter (STF) and an adaptive feedforward controller is presented as an approach to meet the motion stability requirements for next generation, segmented, optical space systems. In such systems, pointing accuracy must be maintained under conditions that include periodic disturbances such as those induced by the Reaction Wheel Actuators (RWA). When a tachometer signal is available, it can be used in an adaptive feedforward control scheme to cancel the periodic disturbance in the output. A model for the RWA is used that includes harmonics that can excite the flexible modes of the system. The STF controller can be used to increasing damping on these modes, thereby allowing for higher gains and quicker convergence by the feedforward controller. Here, this control method is applied to a state-space model of AFRL's Deployable Optical Telescope (DOT), where the control goal is to maintain the mirror positions while undergoing an RWA disturbance.