Experimental Demonstration of an Indoor GPS-Based Sensing System for Robotic Applications

Abstract

The objective of this research is to demonstrate that an indoor sensing system consisting of pseudo-satellites (pseudolites) and modified commercial GPS receivers can be used to sense and control the relative position and attitude of prototype robotic space vehicles in a laboratory environment. The long-term goal for this research is to develop technologies that will enable robotic vehicles to perform complex maneuvers such as autonomous navigation, rendezvous, multivehicle formation flying, and assembly in space. An experimental hardware system consisting of a prototype space robot, target vehicle, and GPS system has been devised to closely emulate real space systems. Since the experiments take place indoors where GPS satellite signals cannot be received, several GPS pseudolite transmitters have been built and installed around the perimeter of the laboratory to provide the GPS signals. The indoor GPS environment created by the close-range pseudolite transmitters required development of new algorithms for resolving vehicle positions and attitudes from the carrier-phase measurements. Therefore, the most novel aspect of this research has been the development of GPS for indoor sensing, where it has the potential to be applied to indoor mobile robots and to automated manufacturing systems. This paper presents the theoretical formulation and experimental results of the use of this indoor GPS system for performing rendezvous between a prototype space robot vehicle and a passive target vehicle.