Control of Flexible Structures Using GPS: Methods and Experimental Results

Abstract

Active control of the attitude and vibration of a e exible structure using the Global Positioning System (GPS) is demonstrated. Measurements of the carrier phase of the GPS signal at several antennas are used to estimate the deformation and orientation of the structure. This distributed measurement capability, combined with excellent zero-frequency performance, makes the GPS sensor an excellent choice for a wide range of applications, including space structures, suspension bridges, and skyscrapers. The control system developed around the GPS sensor is presented for a particular structure modeled after the Space Station. The results from several new experiments demonstrate that the GPS sensor provides rotational accuracies better than 0.1 deg for static tests. Measured spectra also demonstrate that the carrier-phase GPS techniques are sufe ciently accurate to resolve many of the modes of vibration. Several feedback control experiments are used to show that the sensor provides an accurate and robust measure of the structural deformations. These experiments culminate in a fast slew maneuver under feedback control, which providesa cleardemonstration oftheapplication of carrier-phaseGPS forboth alignment and vibration control. This work shows the potential for GPS as a high-precision, real-time structural sensor.