Abstract :
The robustness properties of collocated velocity feedback controllers used for damping enhancement in large, flexible space structures are investigated. It is proved that the closed-loop system using such controllers is asymptotically stable in the large when: 1) unmodeled linear time-invariant dynamics (such as sensors/actuators) are present, provided that the phase angle of such dynamics is between -90° and 90°, 2) time-varying or invariant nonlinearities lying in the first and the third quadrant (i. e., belonging to the (0, ¿) sector) are present, or 3) sector-type nonlinearities following first-order stable dynamics are present in the feedback loop.
