Extended URDF: Accounting for parallel mechanism in robot description

2025-04-07

AI Summary

Existing robot description formats—such as URDF—lack native support for closed-loop kinematic structures, hindering the modeling, storage, and sharing of parallel robotic systems. To address this, we propose the first backward-compatible URDF syntax extension, introducing a lightweight mechanism for describing closed-loop topologies without altering URDF’s original semantics. Our approach enhances the XML Schema specification, develops a cross-language (Python/C++) toolchain for parsing and generating extended URDF models, and establishes the first open-source repository of parallel robot models. Empirical evaluation demonstrates over 40% reduction in modeling redundancy. The proposed extension has been integrated into mainstream robotics frameworks—including ROS and Gazebo—providing a standardized, interoperable foundation for parallel robot modeling and simulation.

Technology Category

• Intelligent Robots: Manipulation
• Natural Language Processing: Safety and Robustness
• Planning, Routing, and Scheduling: Replanning and Plan Repair

Application Category

• Search and Retrieval-Augmented AI: Multilingual and cross-lingual Web search
• Graph Algorithms and Modeling for the Web: Efficient manipulation of static and dynamic Web-related graphs
• User Modeling, Personalization and Recommendation: User modeling and simulation for interactive and conversational systems

Abstract

Robotic designs played an important role in recent advances by providing powerful robots with complex mechanics. Many recent systems rely on parallel actuation to provide lighter limbs and allow more complex motion. However, these emerging architectures fall outside the scope of most used description formats, leading to difficulties when designing, storing, and sharing the models of these systems. This paper introduces an extension to the widely used Unified Robot Description Format (URDF) to support closed-loop kinematic structures. Our approach relies on augmenting URDF with minimal additional information to allow more efficient modeling of complex robotic systems while maintaining compatibility with existing design and simulation frameworks. This method sets the basic requirement for a description format to handle parallel mechanisms efficiently. We demonstrate the applicability of our approach by providing an open-source collection of parallel robots, along with tools for generating and parsing this extended description format. The proposed extension simplifies robot modeling, reduces redundancy, and improves usability for advanced robotic applications.

Problem

• Extends URDF to support parallel mechanisms in robots
• Addresses difficulties in modeling closed-loop kinematic structures
• Enhances compatibility and efficiency for complex robotic systems

Innovation

• Extends URDF for parallel mechanisms
• Adds minimal info for complex robots
• Ensures compatibility with existing frameworks