Vision based Target Tracking/ Following and Estimation of Target Motion

Abstract

The vision based target tracking/ following is presented. There is no interior communication between the target and tracker and their relative displacement is measured with the 3D visual sensors. The tracking/ following control law is designed in the half North-EastDown (NED) frame with the dynamic inversion and the robust perfect tracking (RPT)techniques. The half NED frame is formed by moving the origin of the NED frame to the mass center of the target and then rotating the X axis along the Z axis to be aligned with the flight direction of the target. The RPT technique is one of the better techniques to design the tracking control laws for the linear plants. It involves with the high-order derivatives of the reference to improve the tracking/ following performance. In order to implement the RPT control law, a novel algorithm is developed to estimate the velocity and acceleration of the target with the measured relative displacement between the target and tracker. The algorithm is developed based on the extended Kalman filtering and under assumption of the quasi steady states in which the derivatives of the target ground speed, flight path and directional angles are constant. The simulation results demonstrate that the resulting the closed-loop system is capable of tracking/ following the 3D maneuvering target in the scheduled relative distance and orientation with respect to the target.Keywords: estimation of target motion, extended Kalman filtering, filtering and estimations, vision based tracking, vision based applications. NomenclatureB bc Transformation matrix from the body frame to the camera frame B gb Transformation matrix from the NED frame to the body frame B gc Transformation matrix form the NED frame to the camera frame B ψst Transformation matrix form the NED frame to the half NED frame C a Camera intrinsic parameter matrix F Feedback gain matrix H Matrix of the CCD camera model I Identity matrix with appropriate dimensions P Homogenous coordinates of the points in the image frame, pixel P P= ( P x P y 1 ) P i Homogenous coordinates of the i-th point in the image frame, pixel P g Coordinates of the points in the NED frame, m P gmc Coordinates of the tracker mass center in the NED frame, m P gt Coordinates of the points on the target in the NED frame, m P gti Coordinates of the i-th point on the target in the NED frame, m ΔP gti Coordinates of the i-th point on the target in the NED frame with respect to the tracker, m ΔP tracked Coordinates of the tracked point associated with the target in the NED frame with respect to the tracker, m T v Sampling period of the visual measurement, s ΔT h Demanded change of the thrust, N V a Air speed, m/s V g Ground speed of the tracker, m/s V gt Ground speed of the target, m/s V gg Velocity of the tracker with respect to ground in the NED frame, m/s V ggt Velocity of the target with respect to ground in the NED frame, m/s a gg Acceleration of the tracker in the NED frame, m/s 2 a ggc Expected acceleration of the tracker in the NED frame, m/s 2 a ggt Acceleration of...

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