Path Generation for Robot Vehicles Using Composite Clothoid Segments

Abstract

The response of an autonomous vehicle in tracking a reference path depends partly on the nature of the path. The condition for paths that are intrinsically amenable to follow are briefly presented, and then a method for the generation of amenable paths is proposed in this paper. Previous path generation methods have sought to simplify a path by using arcs, superarcs, polynomial curves, and clothoid curves to round corners, which result from poly-line fits through a given sequence of points. The developed method consists of two steps: First, a sequence of postures is obtained using given points, then each pair of neighboring postures is connected with three clothoid curve segments. In the second step, a completely general method to connect a path of clothoid curves between two completely arbitrary postures was not envisioned and method for a pair of adjacent postures was developed. By virtue of the property of clothoid curves, a generated path is continuous with respect to position, tangent direction, and curvature, and is linear in curvature. Aside from the properties innate to clothoid curves, the generated paths transition smoothly into turns, pass through all the way points, and sweep outside the corners. For interpolating around obstacles that are commonly inside the corner, these properties are especially useful.