Hierarchical Collision-Free Configuration Planning for a Soft Manipulator

Abstract

Soft manipulators (SMs) have shown great potential for interactive tasks in confined environments. However, avoiding obstacles of SMs may conflict with the manipulator’s configuration, the planned trajectory for tracking control, and the target position for grasping. To coordinate configuration planning, tracking control, and target grasping in obstacle avoidance, this study proposes a hierarchical configuration planning framework with three levels: behavior planning, configuration planning, and shape/position control. At the behavior planning level, a Discrete Event System (DES)-based planner is designed to orchestrate mode transitions among obstacle avoidance, tracking control, and target grasping. The configuration planning level adopts the Bézier curve to model the SM backbone curve and constructs a repulsive potential field to quantify obstacle effects on the entire manipulator configuration. Under the constraints of grasping distance and material physical limit, the control points of the Bézier curve corresponding to the optimal configuration that minimizes the repulsive potential energy are computed. Experiments demonstrate the effectiveness of the proposed framework in achieving collision-free configuration planning for object grasping and placement in confined operational scenarios.