Robust Inverse Kinematics at Position Level by Means of the Virtual Redundant Axis Method

Abstract

Several techniques have been developed in the past to handle the inverse kinematics of serial robots passing through or close to singular configurations. As a common line, these approaches operate at velocity level, seeking a trade-off between tracking accuracy and joint velocity feasibility. While providing robust control, some difficulties arise in these methods for predicting end-effector errors and their spread in SE(3). In a previous paper, the virtual redundant axis (VRA) method was introduced at velocity level, by which end-effector velocity errors could be concentrated in non-controllable directions. The present paper extends the VRA method to position level, allowing for a precise motion tracking and the handling of singularity paths in the same way as regular motions.