On identification and sensorless control of nonlinear torsion in elastic robotic joints

In this paper, we address the identification and design of the sensorless torsion control of elastic robotic joints which has been proposed in our previous work. We discuss some practical aspects of the proposed method which should be accounted for a ready-assembled robotic manipulator at hand. The series of identification experiments required for determining the model-based components is designed and accomplished under constraints of the joint actuation and load motion. The efficiency of sensorless torsion control is shown experimentally for both, trajectory tracking at constant velocity and positioning of the joint load. The experiments are performed on the laboratory setup of a stand-alone elastic joint with inertial and gravity loads. We also comment on the applicability of the proposed method to standard robotic manipulators, while assuming that the joint output is available during the identification.