Superfast Configuration-Space Convex Set
Computation on GPUs for Online Motion Planning
Peter Werner, Richard Cheng, Thomas Stewart, Russ Tedrake, and Daniela Rus
Peter Werner, Richard Cheng, Thomas Stewart, Russ Tedrake, and Daniela Rus
TLDR - We leverage GPUs to construct probabilistically collision-free convex sets in robot configuration space on the fly. We propose an algorithm that inflates collision-free piecewise linear (PWL) paths into sequences of convex sets (SCS) that are probabilistically collision-free using massive parallelism. We then show a possible way to integrate this algorithm into a motion planning pipeline, which leverages dynamic roadmaps (DRMs) to rapidly find one or multiple collision-free paths, and inflates them. We then optimize the trajectory through the probabilistically collision-free sets, simultaneously using the candidate trajectory to detect and remove collisions from the sets.
EIZO inflates a line segment to a probabilistically collision-free polytope in robot configuration space. This polytope is guaranteed to contain the original line segment. It does this using a zero-order optimization approach that is massively parallelizable.
We propose a possible way of integrating EIZO into a motion planning pipeline that uses DRMs to find initial PWL paths. First, the DRM is constructed offline. Online, the DRM is then utilized to rapidly find a collision-free path, which is subsequently inflated and used by a decomposition-based motion planner to optimize a trajectory. The optimized trajectory may be in collision since the sets are only probabilistically collision-free. To remedy this, we use the collisions found by the candidate trajectories to refine the sets until we find a collision-free trajectory.
We demonstrate the efficacy of our approach in simulation benchmarks in two and seven dimensions and validate the approach on hardware using a KUKA iiwa with perception in the loop. Relative to the nonlinear trajectory optimization baseline, our approach produces slightly higher-cost trajectories but increases the success rate from around 72% to 100% on our simulation benchmark while computing trajectories around 17 times faster. The video demonstrates the hardware setup. For more details, please refer to the paper.