Towards autonomous ergonomic upper-limb exoskeletons: A computational approach for planning a human-like path

Computational path planning approaches can enable development of autonomous rehabilitation and assistive exoskeletons. Using a human-like reference behavior for such wearable systems can ensure safe, effective, and intuitive human-robot interaction. This is of significant importance since the quality of interaction and ergonomic considerations have a substantial effect on technology usability and acceptance by the users. This paper proposes a novel framework for generating human-like paths for wearable exoskeletons in the shoulder-elbow level. The introduced method is a two-stage process where a human-like reference path is planned in the configuration space of the human arm, followed by an analytical transformation that directly maps the derived path to the configuration space of the exoskeleton. The analytical mapping presented is a function of the kinematic parameters of the system and can be adapted for other upper-limb exoskeletons. As a case study, the proposed method is used for generating human-like reference motions for a six-degree-of-freedom exoskeleton supporting scapulohumeral rhythm, glenohumeral rotations, and elbow flexion/extension. Firstly, it is shown that reaching motions associated with activities of daily living can be predicted with high accuracy in the human joint space. This is demonstrated by analyzing the experimental data collected from healthy subjects. Subsequently, it is verified through kinematic analysis that the transformation of generated paths to the exoskeleton configuration space does not alter their spatial profile in the task space. (C) 2021 Elsevier B.V. All rights reserved.