On the Synthesis of Reactive Collision-Free Whole-Body Robot Motions: A Complementarity-based Approach

TL;DR

This paper introduces FLIQC, a novel optimization-based motion planner for high-DOF robots that generates real-time, collision-free, reactive motions by solving complementarity constraints efficiently.

Contribution

The paper presents a new motion planning approach using complementarity constraints that achieves real-time collision-free motion for complex robots in cluttered environments.

Findings

FLIQC outperforms state-of-the-art planners in speed and reliability.

Generates continuous, reactive motions at 1 kHz in simulation and hardware.

Ensures non-penetration through a novel constraint formulation.

Abstract

This paper is about generating motion plans for high degree-of-freedom systems that account for collisions along the entire body. A particular class of mathematical programs with complementarity constraints become useful in this regard. Optimization-based planners can tackle confined-space trajectory planning while being cognizant of robot constraints. However, introducing obstacles in this setting transforms the formulation into a non-convex problem (oftentimes with ill-posed bilinear constraints), which is non-trivial in a real-time setting. To this end, we present the FLIQC (Fast LInear Quadratic Complementarity based) motion planner. Our planner employs a novel motion model that captures the entire rigid robot as well as the obstacle geometry and ensures non-penetration between the surfaces due to the imposed constraint. We perform thorough comparative studies with the state-of-the-art, which demonstrate improved performance. Extensive simulation and hardware experiments validate our claim of generating continuous and reactive motion plans at 1 kHz for modern collaborative robots with constant minimal parameters.