Tracking of Extended Objects with High-Resolution Doppler Radar

Abstract

In an urban environment, one of the key challenges remains to be the reliable estimation of the other traffic participants' motion state. Due to the highly nonlinear motions in city traffic, an instant and precise estimation of heading direction, velocity, and, particularly, yaw rate is required. Radar sensors are well suited for this task due to their robustness to environmental influences and direct measurement of the radial (Doppler) velocity. High-resolution radars receive multiple reflections from an extended object. In comparison to state-of-the-art approaches, not only is the Doppler velocity of a single reference point taken into account, but also is the distribution of the Doppler velocity across the vehicle analyzed. The velocity profile is derived with characteristic features and a corresponding sample covariance. These are fused into an unscented Kalman filter, resulting in a significant accuracy improvement and a reduction in the latency of the filter to almost zero during a change in motion or initialization. This yields a great improvement in determining the trajectories of potential critical objects, increasing the time to avoid collisions. Furthermore, the approach enables simultaneous identification of the rotation center of the object, which is essential for the tracking of highly dynamic maneuvers. All approaches were implemented and evaluated on a large experimental data set using highly precise reference systems as ground truth. The results show an impressive improvement in the accuracy of the yaw rate estimation of a factor of 3–4 compared with state-of-the-art approaches in a dynamic scenario.