Multilevel Path Planning for Nonholonomic Robots Using Semiholonomic Subsystems

Abstract

We present a new and complete multi-level approach for solving path planning problems for nonholonomic robots. At the rst level a path is found that disrespects some of the nonholonomic constraints. At each next level a new path is generated, by transformation of the path generated at the previous level. The transformation is such that more nonholonomic constraints are respected than at the previous level. At the nal level all nonholonomic constraints are respected.We present t wo techniques for these transformations. The rst, which w e call the Pick and Link technique, repeatedly picks pieces from the given path, and tries to replace these by more feasible ones. The second technique restricts the free con guration space to a tube" around the given path, and a roadmap, capturing the free space connectivity within this tube, is constructed by the Probabilistic Path Planner. F rom this roadmap we retrieve a new, more feasible, path.In the intermediate levels we plan paths for what we refer to as semi-holonomic subsystems. Such a system is obtained by taking the real physical system, and removing some of its nonholonomic constraints.In this paper, we apply the scheme to car-like robots pulling trailers, that is, tractor-trailer robots. In this case, the real system is the tractor-trailer robot, and the ignored constraints in the semi-holonomic subsystems are the kinematic ones on the trailers. These are the constraints of rolling without slipping, on the trailers wheels.Experimental results are given that illustrate the time-e ciency of the resulting planner. In particular, we show that using the multi-level scheme leads to signi cantly better performance in computation time and path shape than direct transformations to feasible paths.

Motion planning for a reversing general 2-trailer configuration using Closed-Loop RRT

“…One and two trailer planning simulations are presented but obstacles are omitted. Impressive results on global planning with obstacles for a 2-trailer is presented in [8]. However, the approaches presented above consider the case with on-axle hitching despite that most practical applications have off-axle hitching making the kinematics more challenging and the system equations more complicated.…”

Kinodynamic motion planning: connecting exploration trees using trajectory optimization Methods

“…Solutions based on local methods have been proposed for the nonholonomic systems for which a local method could be designed [6], [9], [10]. Most of these methods produce a path and the additional kinematic constraints imposed by the maximal velocities and accelerations of the systems are considered in a second step.…”

Path Optimization for Nonholonomic Systems: Application to Reactive Obstacle Avoidance and Path Planning

“…First, this type of kinematic systems are not well understood in control theory : it is not differentially flat nor is it nilpotent. In other words, there is no known steering method for this type of vehicles and thus path planning methods using a steering method [2,5,6] are difficult to use. Other classical path planning methods explore the configuration space by expanding a tree [1,3].…”