Singularity Analysis of ABB's GoFa 5 Robot Arm

Abstract

In the past decade, manipulator arms with non- traditional architectures — once found mainly in space and painting applications — have become popular as collaborative robots. Examples include ABB’s YuMi and GoFa, Kinova’s Link 6, and Fanuc’s CRX. These cobots lack closed-form inverse kinematics solutions, making it impossible to unambiguously select one configuration among the 16 (or infinitely many) that correspond to a given end-effector pose, which may create safety risks. Moreover, they exhibit far more singularities than typical manipulators, and most of them are far more complex to describe. Nevertheless, many authors argue these manipulators can provide improved dexterity and a larger workspace. In this paper, we analyze the singularities of ABB’s GoFa using Grassmann line geometry and provide straightforward, sufficient (though conservative) conditions for avoiding them. Then, while GoFa can exhibit over a dozen distinct singularities compared to only three (wrist, shoulder, and elbow) for traditional robot arms, we attempt to quantify which architecture actually possesses a greater amount of singular and near-singular configurations.