Towards Standard Test Artefacts for Synchronous Tracking of Human-Exoskeleton Knee Kinematics

A repeatable evaluation of human-exoskeleton kinematics is needed to assess an exoskeleton's impact on worker biomechanics and safety. Standard measurement methods and metrics facilitate technology adoption and effective specification of the exoskeleton's intended use. This study assesses the feasibility and repeatability of a measurement method that enables synchronous tracking of human and exoskeleton kinematics using a set of lower-limb human motion capture test artefacts and exoskeleton motion capture plates. Experimental validation was conducted on 30 subjects. The inter-trial repeatability of the human knee joint angle was within 1.2° to 2.7° and within 1.3° to 3.1° for the exoskeleton joint angle (50th to 99th percentile). To apply the measurement of the test artefacts rigid body position and orientation, two potential metrics, human-exoskeleton fit and stability, were implemented based on the exoskeleton-human alignment offset and the stability of the exoskeleton frame.