Near Time-Optimal Hybrid Motion Planning for Timber Cranes

2025-06-25

AI Summary

Motion planning for hydraulic-driven timber cranes with passive joints remains challenging due to unaddressed pump flow constraints, nonholonomic dynamics, and stringent payload swing suppression requirements. Method: This paper proposes a near-time-optimal hybrid planning framework integrating: (i) an enhanced VP-STO planner incorporating pump flow limits and a novel collision cost function; (ii) TOPP-based path parameterization; (iii) Informed RRT* for global sampling; (iv) gradient-based local optimization; and (v) explicit passive-joint dynamic modeling with real-time dynamic compensation. Contribution/Results: The method generates high-quality, dynamically feasible trajectories in a single query. Experiments demonstrate significant improvements over state-of-the-art baselines in time-optimality, obstacle avoidance robustness, and operational stability—particularly under hydraulic actuation limitations. It provides a systematic, engineering-ready solution for autonomous control of complex hydraulic manipulators.

Technology Category

• Intelligent Robots: Motion and Path Planning
• Planning, Routing, and Scheduling: Mixed Discrete/Continuous Planning
• Search and Optimization: Sampling/Simulation-based Search

Application Category

• Responsible Web: Machine-in-the-loop, human agency and autonomy
• Search and Retrieval-Augmented AI: Web learning to rank, online learning, and counterfactual learning for ranking
• Systems and Infrastructure for Web, Mobile and WoT: Applied ML and AI for Web-based mobile applications

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.

Problem

• Time-optimal motion planning for hydraulic timber cranes
• Addressing hydraulic constraints and passive joints in planning
• Combining global and local planners for collision-free operation

Innovation

• Enhanced VP-STO with pump flow constraints
• Novel collision cost formulation for robustness
• Hybrid planner combining global and local strategies