Interaction Force Estimation Using Extended State Observers: An Application to Impedance-Based Assistive and Rehabilitation Robotics

• Published in: IEEE robotics and automation letters Vol. 4; no. 2; pp. 1156 - 1161
• Main Authors: Sebastian, Gijo, Li, Zeyu, Crocher, Vincent, Kremers, Demy, Tan, Ying, Oetomo, Denny
• Format: Journal Article
• Language: English
• Published: Piscataway IEEE 01.04.2019; The Institute of Electrical and Electronics Engineers, Inc. (IEEE)
• Subjects: Actuation; compliance and impedance control; Computer simulation; Dynamic models; Dynamics; Force; Manipulator dynamics; Manipulators; Observers; Position measurement; Rehabilitation robotics; Rehabilitation robots; Robot arms; Robotics; State observers; Torque sensors (robotics)
• ISSN: 2377-3766; 2377-3766
• DOI: 10.1109/LRA.2019.2894908

This letter presents a force observer that estimates the external interaction forces from the measured joint position and joint actuation for a class of robotic manipulators. This is done without an explicit (physical) force or torque sensor, through an extended state observer (ESO) assuming a known model of the dynamics of the manipulator. It is designed to be capable of estimating relatively fast time-varying external forces. The main result shows that the proposed ESO is theoretically able to estimate unknown time-varying external forces to an arbitrary accuracy for any initial condition starting in a given compact set. Simulation results demonstrate the effectiveness of the proposed ESO. Moreover, first experimental evaluations with a healthy subject and a poststroke patient on a rehabilitation robotic platform show the feasibility of the approach in this context and highlight the importance of the quality of the dynamic model.