Robotic Leg Illusion: System Design and Human-in-the-Loop Evaluation

Abstract

The question how humans integrate artificial lower limb devices into their body schema has distinct potential for engineering motion assistance systems, e.g., the design of robotic prostheses. Adding robotic technology to existing psychological experiments enables a deeper investigation of multisensory interaction between proprioceptive, visual, and tactile stimuli during motion. This paper reports the design and control of a robot to investigate embodiment with regard to the lower limbs. In an evaluation study, the rubber hand illusion is transferred to the whole leg for the first time. Participants performed knee bends according to three different conditions being imitated by a robotic leg. The occurrence of a robotic leg illusion was subjectively assessed by a questionnaire and objectively measured by the proprioceptive drift. Considering both metrics, the results show a successful integration of the robotic leg into the body schema. Motion synchronization appears to be a paramount factor, whereby the study indicates that acoustical stimulation might also be relevant. The interrelation between mechatronic design and control of the human-in-the-loop experiment and the factors influencing the illusion are discussed and alternative experimental setups are suggested. Index Terms-Body schema, human-in-the-loop, human-robot interaction, multisensory integration, robotic leg illusion (RobLI). I. INTRODUCTION A FTER amputation of extremities, people are encouraged to wear prostheses when starting the rehabilitation process [1] and for the rest of their lives in order to maintain

Coordination Between Partial Robotic Exoskeletons and Human Gait: A Comprehensive Review on Control Strategies

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Human-Robot Body Experience: An Artificial Intelligence Perspective

“…Several studies using such technical augmentations outlined how robot design and control influence embodiment and, particularly, the relevance of (haptic) human-machine interfaces: a similar contribution of haptic and motor feedback to embodiment has been found in the upper limbs [11]. Moreover, embodiment was shown to be an appropriate assessment metric to consider users' experiences in interface design using human-in-the-loop approaches [8] and outlined to be promising for the lower limbs as well [17]. It should be noted that non-instrumental aspects of haptic feedback might decisively contribute to device embodiment and should be considered in interface design, e.g., the mediation of affective and social information [3].…”

Robotic exoskeleton embodiment in post-stroke hemiparetic patients: an experimental study about the integration of the assistance provided by the REFLEX knee exoskeleton

“…Extra analysis can be carried out following the same methodology previously reported to assess the embodiment of prosthesis or wheelchairs 43 . In this regard, subjective questionnaires or personal interviews could be used to evaluate if users consider the device as a part of their own body 44,45 or the proprioceptive drift could be measured as a direct and objective sign of a change in the body schema 46,47 .…”