Joint radar alignment and odometry calibration

An unsupervised online procedure for the precise alignment of fully integrated Doppler radar sensors is proposed. Alignment is the precise determination of the angle between the principal beam direction of the radar sensor and the thrust axis of the vehicle. The method is based on the accurate determination of the sensor movement through the analysis of the Doppler distribution of stationary targets over the azimuth angle. The precise alignment facilitates estimating the ego motion of the vehicle. The approach is long-term stable and bias free and therefore predestined for the calibration of standard vehicle's odometry (gyroscope and wheel sensors). A hierarchical optimization strategy to obtain the systematic errors is presented and Maximum Likelihood estimators are derived for each step. A Monte-Carlo simulation is used to identify critical impact factors and determine them quantitatively. The performance of all approaches is finally evaluated with promising results using measurements obtained by a pre-series 77 GHz Doppler radar sensor. An alignment precision on the order of 0.01-0.05° is achieved.