Perceived CT-Space for Motion Planning in Unknown and Unpredictable Environments

One of the ultimate goals in robotics is to make high-DOF robots work autonomously in unknown changing environments. However, motion planning in completely unknown environments is largely an open problem and poses many challenges. One challenge is that in such an environment, the configuration-time space (CT-space) of a robot is not known beforehand. This paper describes how guaranteed collision-free regions in the unknown CT-space can be discovered progressively via sensing in real time based on the concept dynamic envelope, which is not conservative, i.e., does not assume worst-case scenarios, and is robust to uncertainties in obstacle behaviors. The introduced method can be used in general by real-time motion planners for high-DOF robots to discover the existence of guaranteed collisionfree future motions efficiently. The utility is further confirmed both in simulation and in real-world testing involving a 5-DOF robot manipulator.