Integration of Motion and Stereo Sensors in Passive Ranging Systems

The automation of rotorcraft flight at low altitudes requires on-board acquisition of information about the location of objects in and around the flight path of the vehicle. Due to the covert nature of certain missions, it is desireable to use passive sensors to acquire the range information. Range information about the objects can be computed by combining the optical flow resulting from the sensor motion with vehicle states from an inertial navigation system. However, the range information provided by a single passive sensor is sensitive in the direction of flight referred as the focus of expansion. This problem can be overcome by the use of more than one sensor, referred to as stereo methods. This paper describes a recursive approach for processing a sequence of stereo images which will be the basis for an integrated stereo and motion method to provide more accurate range information using a passive ranging system. Results based on motion sequences of stereo images are presented. The approach presented in this paper will also be applicable to other autonomous systems and in robotics.