CONTROL OF FLEXIBLE STRUCTURES USING GPS - METHODS AND EXPERIMENTAL RESULTS

Active control of the attitude and vibration of a flexible structure u sing the Global Positioning System (GPS) is demonstrated. Measurements of the carrier phase of the GPS signal at several antennas are used t o estimate the deformation and orientation of the structure. This dist ributed measurement capability, combined with excellent zero-frequency performance, makes the GPS sensor an excellent choice for a wide rang e of applications, including space structures, suspension bridges, and skyscrapers. The control system developed around the GPS sensor is pr esented for a particular structure modeled after the Space Station. Th e 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 technique s are sufficiently 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 deformation s. These experiments culminate in a fast slew maneuver under feedback control, which provides a clear demonstration of the application of ca rrier-phase GPS for both alignment and vibration control. This work sh ows the potential for GPS as a high-precision, real-time structural se nsor.