Dj. Leo et Dj. Inman, POINTING CONTROL AND VIBRATION SUPPRESSION OF A SLEWING FLEXIBLE FRAME, Journal of guidance, control, and dynamics, 17(3), 1994, pp. 529-536
An analytical and experimental control system design for a slewing fra
me containing active members is presented. This testbed is a model for
the slewing of dynamically complex structures such as solar arrays an
d space trusses. Two of the frame's passive members are replaced by ac
tive elements that contain piezoceramic material. The active members a
re integral in suppressing vibrations because the torsional vibrations
are difficult to control with the slewing actuator. The design is per
formed with a finite element-based model that contains significant err
or; therefore, both control loops must have performance and stability
robustness. Suppression of the torsional motion is accomplished with a
n active member in a positive position feedback (PPF) loop designed wi
th frequency domain and Nyquist techniques. The pointing controller is
designed using mu synthesis to maximize the robustness of the control
law. This compensator slews the structure with a two second settling
time, 7 % overshoot, and less than a 2 % steady-state error due to sta
tic friction. With the supplementary PPF control loop closed, the sett
ling time of the torsional vibrations is reduced from over 30 s to app
roximately 6 s. Thus, vibration suppression and satisfactory step resp
onse is obtained using robust control laws in multiple feedback loops.