Evaluating Path Tracker Performance for Outdoor Mobile Robots

Accurate, high precision path tracking is an important capability for mobile robots in certain applications. In this paper, we discuss a formal method for comparing and evaluating the performance of path tracking algorithms. This method provides a way to quantify both the stability and performance of a tracker, and is of particular interest when high-accuracy off-road tracking is required. Previous work on path tracker performance has focused on the average and maximum position error over the entire path, or has dealt with simulated results. Overall, there is little analysis of tracking error at a lower level, which can provide insight into the behavior of the tracker, along with overall weaknesses and strengths. Our method includes measuring the tracker’s response to particular situations such as discontinuities in the path’s x, y coordinates and path curvature. We also examine the time for the tracker to settle onto the path and the distribution of tracking error vs. path curvature. We apply this method to two commonly used path trackers operating on an outdoor mobile robot. The first is based on a pure-pursuit model, and the second is based on work by Zhang et al (1997). By using this method we were able to evaluate the performance of these two trackers, and discover their relative strengths and weaknesses. The insight gained through this analysis has led to recommendations for path tracker development that will be presented.