GPS/encoder based precise navigation for a 4WS mobile robot

In this paper, position and orientation estimation with high accuracy based on GPS and encoders for a four-wheel-steering vehicle (4WS) mobile robot is addressed. An architecture of position and orientation estimation is proposed, which consists of two Extended Kalman Filters and a processing unit of Runga-Kutta-based dead reckoning. The first EKF fuses data from six encoders to estimate the velocity of vehicle and sideslip angle. The second EKF is applied to the estimation of position and orientation based on the measurement from precise GPS data and output from first EKF. To obtain better accuracy of estimation, an arbitrator is designed to switch between EKF2 and dead reckoning. The results and analysis of experiments are presented to show the effectiveness of the proposed approach.