Flight Tests of an Unmanned Air Vehicle with Integrated Multi-Antenna GPS Receiver and IMU: Towards a Testbed for Distributed Control and Formation Flight

Stanford University's GPS Laboratory has integrated a new multiple-antenna GPS receiver with an inertial measurement unit into the DragonFly unmanned air vehicle. Recent successful flight tests have demonstrated the performance of the new avionics and illustrated the great potential to use the aircraft as a testbed for navigation and control experiments. Unmanned air vehicles (UAVs) are attracting a great amount of current interest in the navigation and control communities. Not only do UAVs provide excellent lowcost testbeds for GPS and GPS/INS integration experiments, but their design and control facilitate the exploration of many exciting new research areas in control theory, ranging from low-level flight control algorithm design to high-level multiple aircraft coordinated mission planning, all for autonomous flight. The DragonFly UAV is a heavily modified model airplane with a twelve-foot wing span. Four GPS antennas on top of the aircraft provide GPS position, velocity and attitude measurements during flight operations. Designed to be modular and expandable, the DragonFly carries approximately ten pounds of sophisticated electronics and sensors in the forward section of the fuselage. These electronics include a new Trimble Navigation-designed GPS receiver with up to 5 antenna inputs and 40 parallel channels; a Honeywell HG1700 tactical grade inertial measurement unit; and an embedded single board computer (SBC). Fast communications through the SBC allow for inertial aiding signals to be fed into the GPS receiver. Tightly coupled, these avionics create a powerful, robust and easy-toembed flight control system. The DragonFly is flight tested at Moffett Federal Airfield. Current research includes the development of a modular real-time controller design platform and the design and verification of flight control algorithms for optimal flight mode switching and high maneuverability (including aerobatics). In addition, Stanford recently purchased a second UAV that will be similarly equipped. Future research will focus on the issues of multiple aircraft coordination (for formation flying), sensor fusion and control over air-to-air datalink.