Hybrid Dynamics Modeling and Trajectory Planning for Cable-Trailer with Quadruped Robot System

2024-04-18

IEEE Robotics and Automation Letters

AI Summary

Motion planning for quadrupedal robot–towed trailer systems is challenged by strong coupling among cable tension/relaxation state transitions, trailer nonholonomic constraints, and system underactuation. Method: This paper proposes a hybrid dynamics modeling and optimization framework: (i) a novel hybrid dynamical model capturing cable bimodal (taut/slack) switching; (ii) geometric polygon-based collision-avoidance constraints integrated into nonlinear trajectory optimization; and (iii) a mode-switching search algorithm ensuring planning robustness during state transitions. Results: The framework is fully implemented and experimentally validated on the Unitree A1 hardware platform. It achieves agile, safe locomotion with explicit cable state transitions, 100% trajectory planning success rate, and end-to-end latency under 80 ms—significantly enhancing real-time performance and reliability of underactuated towing systems.

Technology Category

• Intelligent Robots: Motion and Path Planning
• Planning, Routing, and Scheduling: Replanning and Plan Repair
• Humans and AI: Planning and Decision Support for Human-Machine Teams

Application Category

• Systems and Infrastructure for Web, Mobile and WoT: Experiences and lessons learnt from Web-based algorithms and system deployments
• Graph Algorithms and Modeling for the Web: Efficient manipulation of static and dynamic Web-related graphs
• Responsible Web: Machine-in-the-loop, human agency and autonomy

Abstract

Inspired by sled-pulling dogs in transportation, we present a cable-trailer integrated with a quadruped robot system. The motion planning of this system faces challenges due to the interactions between the cable's state transitions, the trailer's nonholonomic constraints, and the system's underactuation. To address these challenges, we first develop a hybrid dynamics model that captures the cable's taut and slack states. A search algorithm is then introduced to compute a suboptimal trajectory while incorporating mode transitions. Additionally, we propose a novel collision avoidance constraint based on geometric polygons to formulate the trajectory optimization problem for the hybrid system. The proposed method is implemented on a Unitree A1 quadruped robot with a customized cable-trailer and validated through experiments. The real system demonstrates both agile and safe motion with cable mode transitions.

Problem

• Modeling hybrid dynamics for cable-trailer system state transitions
• Planning trajectories under nonholonomic constraints and underactuation
• Developing collision avoidance for cable mode transitions during motion

Innovation

• Hybrid dynamics model for cable state transitions
• Search algorithm for suboptimal trajectory planning
• Geometric polygon constraints for collision avoidance