New Danger and Discomfort Evaluation Measures for Mobility-Assistance Robots: Formulation and Preliminary Experiments

Abstract

This paper proposes new danger and discomfort evaluation measures for the elderly users of mobility assistive robots. Previous danger evaluation measures, primarily developed for manipulation assistance scenarios, are not applicable for mobility assistance. In mobility assistance, a user is in continuous physical contact with the robot during the assistive task whereas in the manipulation assistance, the physical contact is only for short durations in the accidental conditions. In addition to safety issue, the continuous efforts of researchers to make the assistive robots more and more comfortable for their intended users suggest that a measure to evaluate the comfortableness of assistive robots would also be very useful. Our proposed evaluation measures are based on the significant factors (determined through subjective tests) that affect the safety and comfortableness of a user in mobility assistance scenarios. The proposed danger evaluation measure is based on the velocity mismatch between user and robot and the distance between user and obstacles whereas the discomfort evaluation measure considers the physical and mental burdens of a user while assisted by a robot for mobility. The usefulness of proposed evaluation measures is established through experiments using SpiderBot-II, a parallel wire mechanism for assisting elderly and handicapped persons inside homes. Preliminary experimental results indicate that these evaluation measures can be used effectively for pointing out the potential dangerous and uncomfortable situations during mobility assistance of elderly persons.