Abstract
G2 lane-change path imposes symmetric conditions on the path geometric properties. This paper presents the comparative study of time-optimal velocities to minimize the time needed for traversal of three planar symmetric parametric polynomial lane-change paths followed by an autonomous vehicle, assuming that the neighboring lane is free. A simulated model based on unicycle that accounts for the acceleration and velocity bounds and is particularly simple for generating the time-optimal path parameterization of each lane-change path is adopted. We base the time-optimal trajectory simulations on numerical integration on a path basis under two different end conditions representing sufficient and restricted steering spaces with remarkable difference in allowable maximum curvature. The rest-to-rest lane-change maneuvering simulations highlight the effect of the most relevant path geometric properties on minimal travel time: a faster lane-change curve such as a quintic Bezier curve followed by a unicycle tends to be shorter in route length and lower in maximum curvature to have achievable highest speed at the maximum curvature points. The results have implications to path selection for parallel parking and allow the design of continuous acceleration profile via time scaling for smooth, faster motion along a given path. This could provide a reference for on-road lane-change trajectory planning along a given path other than parametric polynomials for significantly more complex, complete higher-dimensional highly nonlinear dynamic model of autonomous ground vehicle considering aerodynamic forces, tire and friction forces of tire-ground interaction, and terrain topology in real-world.
Highlights
As an essential part of the active safety system of autonomous driving or human-driven cars [1,2,3], a lane-change maneuver performed by a vehicle on a terrain [4, 5] is a path following or trajectory tracking task for avoiding vehicle-tovehicle collisions
We set up two scenarios of loose and hard curvature constraints for emulating the constrained maneuver space under given velocity and acceleration bounds. e unicycle is required to reach the final configuration with zero velocity in minimum travel time, by following the lane-change curve starting at rest from the same initial configuration in two scenarios. e two scenarios are sufficient to reveal the curve geometric properties most related to travel time along a given path, as was observed in [27] for ground mobile robot navigation experiments. e simulation is performed on Intel Core i5 2.7 GHz, 8G LPDDR3 Linux on a standard laptop computer with codes written based on the open-source code of TOPP library in
Minimum-time lane-change maneuvering along symmetric parametric polynomial paths under the constraints given by bounds on velocity and acceleration of a vehicle is studied by simulation-based evaluation on a path basis. e vehicle model we simulate is a unicycle, which is effective and simple for generating the time-optimal velocity profile
Summary
As an essential part of the active safety system of autonomous driving or human-driven cars [1,2,3], a lane-change maneuver performed by a vehicle on a terrain [4, 5] is a path following or trajectory tracking task for avoiding vehicle-tovehicle collisions. Unicycle is a popular model for control and trajectory planning of nonholonomic wheeled mobile robots in that it offers very good compromise between accuracy and computational efficiency for simulation and prediction of nonholonomic autonomous vehicle motion (e.g., [12, 25, 27,28,29]), that is, zero lateral velocity for emulating the vehicle performance. (i) Simulation results based on unicycle provides a good understanding of velocity and acceleration characteristics and the switching structure defined by the velocity limit curve caused by all the constraints of time-optimal solution along parametric polynomial lane-change curves It provides a supplementary comparative study of assessment of least amount of travel time along parametric polynomial lanechange curves, as compared to earlier work [8].
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a call
