Near Time-Optimal Hybrid Motion Planning for Timber Cranes

TL;DR

This paper presents a novel hybrid motion planning method for timber cranes that achieves near time-optimal, collision-free trajectories by enhancing stochastic optimization with hydraulic constraints and passive joint considerations.

Contribution

It introduces an improved VP-STO algorithm incorporating hydraulic pump constraints and a new collision cost, tailored for timber cranes with passive joints.

Findings

Enhanced VP-STO outperforms RRT* in time-optimal planning.

The hybrid planner effectively manages passive joint dynamics.

Method improves collision avoidance and sway damping in crane motion planning.

Abstract

Efficient, collision-free motion planning is essential for automating large-scale manipulators like timber cranes. They come with unique challenges such as hydraulic actuation constraints and passive joints-factors that are seldom addressed by current motion planning methods. This paper introduces a novel approach for time-optimal, collision-free hybrid motion planning for a hydraulically actuated timber crane with passive joints. We enhance the via-point-based stochastic trajectory optimization (VP-STO) algorithm to include pump flow rate constraints and develop a novel collision cost formulation to improve robustness. The effectiveness of the enhanced VP-STO as an optimal single-query global planner is validated by comparison with an informed RRT* algorithm using a time-optimal path parameterization (TOPP). The overall hybrid motion planning is formed by combination with a gradient-based local planner that is designed to follow the global planner's reference and to systematically consider the passive joint dynamics for both collision avoidance and sway damping.