Redundancy Parameterization of the ABB YuMi Robot Arm

2025-05-29

AI Summary

Path planning for the ABB YuMi 7-DOF redundant manipulator is challenging under joint limits, and no unified redundancy parameterization standard exists outside RobotStudio. Method: We propose, for the first time, a RobotStudio-compatible, precise definition of the shoulder-elbow-wrist (SEW) arm angle—supporting arbitrary reference vectors and covering all eight inverse kinematic solutions. Building upon the classical SEW framework, our approach integrates geometric inverse kinematics (IK-Geo) with subproblem decomposition and explicitly incorporates joint limit constraints into a 2D search space. We derive the SEW-angle Jacobian matrix and provide a complete singularity criterion. Contribution/Results: Experimental validation confirms the accuracy and robustness of the proposed definition. The open-source implementation significantly improves offline path planning in terms of precision, consistency, and reproducibility.

Technology Category

• Intelligent Robots: Motion and Path Planning
• Planning, Routing, and Scheduling: Replanning and Plan Repair
• Search and Optimization: Mixed Discrete/Continuous Search

Application Category

• Responsible Web: Machine-in-the-loop, human agency and autonomy
• Systems and Infrastructure for Web, Mobile and WoT: Experiences and lessons learnt from Web-based algorithms and system deployments
• Search and Retrieval-Augmented AI: Web query analysis, representation and understanding

Abstract

The ABB YuMi is a 7-DOF collaborative robot arm with a complex, redundant kinematic structure. Path planning for the YuMi is challenging, especially with joint limits considered. The redundant degree of freedom is parameterized by the Shoulder-Elbow-Wrist (SEW) angle, called the arm angle by ABB, but the exact definition must be known for path planning outside the RobotStudio simulator. We provide the first complete and validated definition of the SEW angle used for the YuMi. It follows the conventional SEW angle formulation with the shoulder-elbow direction chosen to be the direction of the fourth joint axis. Our definition also specifies the shoulder location, making it compatible with any choice of reference vector. A previous attempt to define the SEW angle exists in the literature, but it is incomplete and deviates from the behavior observed in RobotStudio. Because our formulation fits within the general SEW angle framework, we also obtain the expression for the SEW angle Jacobian and complete numerical conditions for all algorithmic singularities. Finally, we demonstrate using IK-Geo, our inverse kinematics (IK) solver based on subproblem decomposition, to find all IK solutions using 2D search. Code examples are available in a publicly accessible repository.

Problem

• Defining the SEW angle for ABB YuMi's redundant kinematics
• Validating SEW angle compatibility with reference vectors
• Developing inverse kinematics solver for path planning

Innovation

• Defines SEW angle for ABB YuMi path planning
• Uses Shoulder-Elbow-Wrist angle parameterization
• Develops IK solver with 2D search