Partial motion planning framework for reactive planning within dynamic environments

This paper addresses the problem of motion planning in dynamic environments. As dynamic environments impose a real-time constraint, the planner has a limited time only to compute a motion. Given the intrinsic complexity of motion planning, computing a complete motion to the goal within the time available is, in many real-life situations, impossible to achieve. Partial Motion Planning (PMP) is the answer proposed in this paper to this problem. PMP calculates a motion until the time available is over. At each iteration step, PMP returns the best partial motion to the goal computed so far. Like reactive decision scheme, PMP faces a safety issue: what guarantee is there that the system will never end up in a critical situations yielding an inevitable collision? In this paper the safety issue relies upon the concept of Inevitable Collision States that account for both the system dynamics and the moving obstacles. By computing ICS-free partial motion, the system safety can be guaranteed. Application of PMP to the case of a car-like system in a dynamic environment is presented.