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Proceedings Paper

Position loop compensation for flex pivot mounted gimbal stabilization systems
Author(s): Benigno Maqueira
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Paper Abstract

Line-of-Sight (LOS) stabilization of a two axis gimbal (i.e., Elevation and Cross-Elevation) can be improved considerably with the addition of a second set of gimbals (inner and outer) mounted on the X-EL gimbal via flex pivots rather than bearings. With this configuration, a position loop is closed around the inner set for two main functions: 1) stabilize the inner set from a control systems point of view and 2) provide one—to—one coupling between the inner and outer gimbal sets at low frequencies for tracking purposes (less than 2 Hz).

Flex pivots introduce very low coulomb and viscous friction coupling making possible a -40 dB/dec roll-off in the position closed loop (mass stabilization) . This roll-off, beginning at about 2 Hz, increase possible the increase in stabilization from the outer to the inner set. However, special attention must be given to the effects of the relatively large spring rate coupling associated with flex pivots. For the system considered, the flex pivot gimbal resonance limits the minimum bandwidth to 3.5 Hz using conventional derivative control.

This paper discusses a positive feedback solution implementing band limited derivative control to compensate for the flex pivot resonance while minimizing the bandwidth to 2.0 Hz for an additional 11 dB of attenuation above 3 Hz. Trade-off studies are discussed and a closed form solution is presented which solves for the compensator parameters as a function of flex pivot stiffness, plant characteristics, and desired bandwidth. Three examples are presented.

Paper Details

Date Published: 1 September 1990
Proc. SPIE 1304, Acquisition, Tracking, and Pointing IV, (1 September 1990); doi: 10.1117/12.2322212
Show Author Affiliations
Benigno Maqueira, Texas Instruments, Inc. (United States)

Published in SPIE Proceedings Vol. 1304:
Acquisition, Tracking, and Pointing IV
Sankaran Gowrinathan, Editor(s)

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