Continuous-curvature paths for autonomous vehicles

The paths followed by autonomously guided vehicles (AGVs) are generally made up of line and circular-arc segments. For most AGVs, the steering functions required to keep the position and heading of the cart continuously aligned with such paths have discontinuities at the line-arc-line transitions points, because the curvature of the path is discontinuous at these points. For applications where continuous-curvature paths are desired, two types of curves are proposed; polar polynomials in place of circular-arc segments, and Cartesian polynomials in place of arc-arc or arc-line-arc segments for lane change maneuvers. Both curves have computationally simple, closed-form expressions that provide continuous curvature and precise matching of the boundary conditions at the line-curve junctions on the paths. The use of these curves in place of circular arcs for the reference-path generator on an experimental AGV has improved its tracking accuracy during the following turns, particularly at higher speeds.>