Techniques for Real-Time Control of
Flexible Structures Using GPS

E. Teague, Harris, Jonathan P. How, London G. Lawson
Michael Boerjes, and Bradford W. Parkinson

Department of Aeronautics and Astronautics
Stanford University

Presented at the American Astronautical Society, Guidance, Navigation
and Control Conference, Breckenridge, Colorado, Feb. 1996

ABSTRACT

This paper describes the most recent advances in our research on GPS (Global Positioning System) for real-time structural motion sensing and control. The goal of this work is to bring to light the important issues that arise when expanding GPS to deformation sensing, to find and show solutions to these issues, and to demonstrate this technology experimentally. We have shown 20 Hz differential carrier phase measurements with ~5 mm relative position accuracy on a test structure which emulates the dynamic motions of a flexible orbiting structure. The GPS receivers provide measurements from an array of antennas mounted on the test structure. Simultaneous measurements from rate-gyro sensors are used for comparison and verification.

In this paper, we discuss and quantify errors which are encountered when using signals from pseudolites (GPS-like signal generators) whose wavefronts are not well approximated as planar, and we explore, in general, the use of multiple receiver, multiple antenna sensor arrays. The corresponding impact of these topics on our experiment is discussed. Also, details of the test structure and current data are presented and analyzed.

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