Vehicle Trajectory Estimation Using a High-Gain Multi-Output Nonlinear Observer

This paper focuses on the design of a multi-output high gain observer for a vehicle trajectory tracking application. Tracking the trajectories of other vehicles on the road is needed for many applications ranging from collision avoidance to autonomous driving. Previously, such trajectory tracking has been done using linearized dynamic models, interacting-multiple-model (IMM) filters, or else by using LMI-based nonlinear observers. These estimation techniques suffer from some crucial shortcomings. Hence, this paper develops a high gain nonlinear observer for this application. The high gain observer approach offers the advantages of guaranteed feasibility and stability with just one constant observer gain for a wide range of motion. The challenges of transforming the vehicle dynamic model into the required companion form for applying the high gain observer technique are addressed. A coordinate transformation that allows for varying velocity and varying slip angle is shown to be appropriate. The high gain observer methodology for a dynamic system with multiple outputs is presented. Finally, simulation and experimental results on vehicle tracking are demonstrated. The experimental results show that, with a high gain observer, vehicle trajectories that span a large range of orientations can be accurately tracked using just one constant observer gain.