Vibration reduction for flexible spacecraft attitude control using PWPF modulator and smart structures

This paper presents a new approach to vibration reduction of flexible spacecraft during attitude control by using pulse width pulse frequency (PWPF) modulator for thruster firing and smart materials for active vibration suppression. The experiment was conducted on the Naval Postgraduate School (NPS)´s Flexible Spacecraft Simulator (FSS), which consists of a central rigid body and an L-shape flexible appendage. A pair of on-off thrusters are used to reorient the FSS. To actively suppress vibrations introduced to the flexible appendage, embedded piezoelectric ceramic patches are used as both sensors and actuators to detect and counter react to the induced vibration. For active vibration suppression using the piezoelectric ceramic patches, Positive Position Feedback (PPF) control targeting at the first two flexible modes of the FSS system is used. Experimental results demonstrate the effectiveness of the control strategy of PWPF modulation for attitude control and PPF for active vibration suppression