Development and Flight Test Of A Robust Optical-Inertial Navigation System Using Low-Cost Sensors

摘要

There is a great need to develop navigation systems that do not depend up GPS, for use in situations where GPS is not available. One such approach is to use a combination of image and inertial data. Significant work has been done at the Advanced Navigation Technology (ANT) Center and elsewhere demonstrating the capability of using a combination of image and inertial data for navigation in cases where the system is observing unknown objects at unknown locations. This paper describes the development and flight test of an optical-inertial system using low cost sensors (including an inexpensive commercial-grade IMU, which is unsuitable for navigation by itself). This prototype system was built and installed on a C-12 aircraft and was flight tested by the U.S. Air Force Test Pilot School (TPS). The algorithm that was implemented used images from a single camera. It was shown that, for the low-cost sensors in the conditions of the flight environment, a significant improvement in performance was obtained by aiding with a barometric altimeter and a magnetic compass, and by using a Digital Terrain Elevation Data (DTED) database. This result was explained by the observability analysis, which showed a significant increase in observability when adding these sensors. With the addition of these additional sensors and the DTED database, the (still) low-cost system demonstrated performance comparable to a high quality navigation-grade inertial navigation system, which costs more than an order of magnitude more than the underlying sensors used for this optical-inertial prototype.