Rapid Motion Estimation of a Target Moving with Time-Varying Velocity

Abstract

This paper describes the development of a vision-based motion estimation and target tracking system for a small unmanned air vehicle (SUAV) equipped with an inertially stabilized gimballed camera. The work concentrates on the design of a new rapid motion estimation algorithm for a ground target moving with time-varying velocity. The capability to estimate target motion for tracking significantly improves operational utility of an inexpensive tactical SUAV. This work extends previous results in which a SUAV simultaneously tracked a ground target moving at constant speed and estimated its motion (position and velocity). In this paper, we allow for time-varying unknown target velocity. The target velocity estimation problem is formulated such that the recently developed L1 rapid estimator can be applied. The estimator uses two real-time measurements: the target position in the camera frame, provided by image processing software, and the relative altitude above the target, provided by an external geo-referenced database. Simulations show that the proposed algorithm is effective at tracking a non-cooperating target moving with unknown velocity, despite repeated out-of-frame events. The paper also describes the development of a Hardware-in-the-Loop simulation, reflecting a realistic tactical scenario, that is intended to provide further validation in advance of flight tests.