Two complete system architectures for a guidance, navigation and control solution of small UAVs is presented. These systems (developed at the University of California Santa Cruz and the University of Minnesota) are easily reconfigurable and are intended to support testbeds used in navigation, guidance and control research. The systems described both integrate a low cost inertial measurement unit, a GPS receiver, a triad of magnetometers to generate a navigation solution (position, velocity and attitude estimation) which, in turn, is used in the guidance and control algorithms. The navigation solution described is a 15 state Extended Kalman Filter which integrates the inertial sensor and GPS measurement to generate a high-bandwidth estimate of a UAV's state. Guidance algorithms for generating a flight trajectory based on waypoint definitions are also described. A PID controller which uses the navigation filter estimate and guidance algorithm to track a flight trajectory is detailed. The architecture: the hardware, software and algorithms is included for completeness. Hardware in the loop simulation and flight test results documenting the performance of these two systems is given.
IntroductionIn current usage, the term Uninhabited Aerial Vehicles or UAVs refers to aircraft which fly without a human operator onboard. They span a wide range in size and complexity. The largest UAVs such as Predator or Globalhawk can weigh several thousand pounds and have wing spans on the order of 10 to 100 feet. At the other end of the size spectrum are UAVs whose maximum dimensions and mass are on the order of centimeters and grams, respectively. In general, these vehicles are being used or envisioned for use in operations where they serve primarily as a platform for a sensor payload. The sensor payload can be as simple as an Electro-Optical camera or as complex as synthetic aperture radar used for remote sensing.