Applications of tuned mass dampers to improve performance of large space mirrors
Yingling, Adam J.
Agrawal, Brij N.
MetadataShow full item record
In order for future imaging spacecraft to meet higher resolution imaging capability, it will be necessary to build large space telescopes with primary mirror diameters that range from 10m to 20 m and do so with nanometers surafce accuracy. Due to launch vehicle mass and volume constraints, these mirrors have to be deployable and lightweight, such as segmented mirrors using active optics to correct mirror surfaces with closed loop control. As a part of this work, system identification tests revealed that dynamic disturbances inheret in a laboratory environment are significant enough to degrade the optical performance of the telescope. Research was performed at the Naval Postgraduate School to identify the vibration modes most affecting the optical performance and evaluate different techniques to increase damping of those modes. Based on this work, tuned mass dampers (TMDs) were selected becaues of their simplicity in implementation and effectiveness in targeting specific modes. The selected damping mechanism was an eddy current damper where the damping and frequency of the damper could be easily changed. System identification of segments was performed to derive TMD specifications. Several configurations of the damper were evaluated, including the number and placement of TMDs, damping constant, and targeted structural modes. The final configuration consisted of two dampers located at the edge of each segment and resulted in the 80% reduction in vibrations. The WFE for the system without dampers was 1.5 waves, with one TMD and the WFE was 0.9 waves, and the two TMDs and the WFE was 0.25 waves. This paper provides details of some of the work done in this area and includes theoretical predictions for optimum damping which were experimentally verified on a large aperture segmented system.
Showing items related by title, author, creator and subject.
Cronauer, Joseph T. (1987);The strain dependence and temperature dependence of damping in the thermoelastic martensitic (shape memory) alloys titanium-nickel and copper-zinc-aluminum was compared to predetermined optimum damping behavior in the ...
Song, G.; N. Buck; Agrawal, B.N. (1997);Minimizing vibrations of a exible spacecraft actuated by on-off thrusters is a challenging task. This paper presents the rst study of pulse-width pulse-frequency modulated thruster control using command input shaping. ...
Active damping of vibrations on space station freedom using Linear Quadratic Gaussian control and H∞ control McClusky, Jacqueline R. (Monterey, California. Naval Postgraduate School, 1991-12);Active damping of modal oscillation is critical to the success of future versions of Space Station Freedom. Vibratory motion may be induced by external disturbances such as solar and gravity gradient torques, extra ...