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“© 20XX IEEE. Personal use of this material is permitted. Permission from IEEE must be obtained for all other uses, in any current or future media, including reprinting/republishing this material for advertising or promotional purposes, creating new collective works, for resale or redistribution to servers or lists, or reuse of any copyrighted component of this work in other works.”, The objective and quantitative assessment of physical human-exoskeletons interaction (pHEI) represents a pressing necessity in the wearable robots field. This process remains of difficult execution, especially for early stage devices, in which the inclusion of human testing could pose ethical and safety concerns. This manuscript proposes a methodology for pHEI assessment based on an active dummy leg named Leg Replica, which is able to sense interaction forces while wearing an exoskeleton. We tested this methodology on a wearable active knee exoskeleton prototype, with the goal to evaluate the effects of a misalignment compensation mechanism. Through this methodology, it was possible to show how the misalignment compensation mechanism was able to reduce the interaction forces during passive exoskeleton motion. Such reduction was less evident when the exoskeleton was active. The tests allowed to identify specific points of improvements for the exoskeleton, enabling a more specific upgrade of the device based on these experimental results. This study demonstrates the ability of the proposed methodology to objectively benchmark different aspects of pHEI, and to accelerate the iterative development of new devices prior to human testing., This work was supported by the project EXOSAFE, awarded by the COVR European Project under grant agreement No. 779966. The exoskeleton prototype used in this work was developed with funding received from the European Union’s Horizon2020 research and innovation programme under Marie Skłodowska-Curie grant agreement No. 801342(Tecniospring INDUSTRY) and the Government of Catalonia’s Agency for Business Competitiveness (ACCIÓ)., Peer Reviewed, Postprint (author's final draft)

Exoskeletons and exosuits have witnessed unprecedented growth in recent years, especially in the medical and industrial sectors. In order to be successfully integrated into the current society, these devices must comply with several commercialization rules and safety standards. Due to their intrinsic coupling with human limbs, one of the main challenges is to test and prove the quality of physical interaction with humans. However, the study of physical human–exoskeleton interactions (pHEI) has been poorly addressed in the literature. Understanding and identifying the technological ways to assess pHEI is necessary for the future acceptance and large-scale use of these devices. The harmonization of these evaluation processes represents a key factor in building a still missing accepted framework to inform human–device contact safety. In this review, we identify, analyze, and discuss the metrics, testing procedures, and measurement devices used to assess pHEI in the last ten years. Furthermore, we discuss the role of pHEI in safety contact evaluation. We found a very heterogeneous panorama in terms of sensors and testing methods, which are still far from considering realistic conditions and use-cases. We identified the main gaps and drawbacks of current approaches, pointing towards a number of promising research directions. This review aspires to help the wearable robotics community find agreements on interaction quality and safety assessment testing procedures.

One of the main problems in studies involving exoskeletons for assisting gait of Spinal Cord Injury (SCI) users is recruitment of a suitable number of subjects, especially when age, gender, and pathologies are considered. Studies involving able-bodied subjects could instead rely on a considerable number of subjects, but the reliability of the results when transferred to real exoskeleton users is limited. This limitation could be partially solved using able-bodied subjects for preliminary tests. In this paper, we describe a first approach to train able-bodied subjects to behave as SCI subjects during walking. An audio feedback driven by a pair of instrumented crutches has been used to train healthy subjects during exoskeleton walking. To test the system, 22 able-bodied subjects have been analyzed during a straight walk with and without the audio feedback. Results show that the audio feedback induces a learning effect and a persistency effect in the participants.