Coupling Vanishing Point Tracking with Inertial Navigation to Produce Drift-Free Attitude Estimates in a Structured Environment

摘要

The Air Force’s need for accurate navigation informa- tion is often met through the combination of inertial and satellite navigation systems. However, the increased use of smaller and smaller unmanned aerial systems opens the possibility of flight in environments where satellite navigation signals are either significantly degraded or unavailable entirely, such as indoors and in dense urban areas. Fortunately, the intrinsic structure of man-made environments can be exploited to aid in determining a vehicle’s attitude when satellite signals are unavailable. This research aims to obtain accurate and stable estimates of a vehicle’s attitude by coupling consumergrade inertial and optical sensors. This goal is pursued by first modeling both inertial and optical sensors and then developing a technique for identifying vanishing points in perspective images of a structured environment. The inertial and optical processes are then coupled to enable each one to aid the other. The vanishing point measurements are combined with the inertial data in an extended Kalman filter to produce overall attitude estimates. This technique is experimentally demonstrated in an indoor corridor setting using a motion profile designed to simulate flight. Through comparison with a tacticalgrade inertial sensor, the combined consumer-grade inertial and optical data are shown to produce an attitude solution that is accurate to within 1.5 degrees and free of long-term drift. A measurement bias is manifested which degrades the accuracy by up to another 2.5 degrees.