Dual-Variable Force Characterisation method for Human-Robot Interaction in Wearable Robotics

TL;DR

This paper introduces a dual-variable force characterization method for wearable robotics that captures both normal and tangential forces, improving the understanding of complex human-robot interactions involving soft tissues.

Contribution

It presents a novel dual-variable approach to force characterization, addressing limitations of single-variable methods in multi-degree-of-freedom interactions.

Findings

Incorporating two variables reduces modeling errors.

The method improves force and torque response predictions.

Enhanced simulation accuracy for cuff-limb interactions.

Abstract

Understanding the physical interaction with wearable robots is essential to ensure safety and comfort. However, this interaction is complex in two key aspects: (1) the motion involved, and (2) the non-linear behaviour of soft tissues. Multiple approaches have been undertaken to better understand this interaction and to improve the quantitative metrics of physical interfaces or cuffs. As these two topics are closely interrelated, finite modelling and soft tissue characterisation offer valuable insights into pressure distribution and shear stress induced by the cuff. Nevertheless, current characterisation methods typically rely on a single fitting variable along one degree of freedom, which limits their applicability, given that interactions with wearable robots often involve multiple degrees of freedom. To address this limitation, this work introduces a dual-variable characterisation method, involving normal and tangential forces, aimed at identifying reliable material parameters and evaluating the impact of single-variable fitting on force and torque responses. This method demonstrates the importance of incorporating two variables into the characterisation process by analysing the normalized mean square error (NMSE) across different scenarios and material models, providing a foundation for simulation at the closest possible level, with a focus on the cuff and the human limb involved in the physical interaction between the user and the wearable robot.