Effects of postural control by personal mobility on human joint movements-prototype of a new alert system for personal mobility devices

Purpose: This study aimed to develop a prototype Personal Mobility (PM) system with human-robot synchronous motion measurement and sensory feedback as an attention reminder to ensure the safe performance of sustained, step-by-step rehabilitation tailored to the daily living conditions of elderly individuals. Methods: Five healthy adults were fitted with a simulation tool to experience the elderly, and inertial measurement unit sensors were placed on the subjects and the PM device to measure joint movements during two postural movements (sitting to supine and supine to standing). In addition, vibration stimulation and voice guidance were implemented as alerts at a certain set threshold of the joint motion angle. We analyzed the deviation of each joint motion between the subject and the PM device regarding the angle measurements of the trunk, hip, knee, and ankle joints. Results: Trunk angle misalignment was high in the sitting-to-supine position. Hip angle misalignment was greater in the supine to standing position. As an alert system, vibration and voice guidance could be presented to the subject with a 0.3-second delay after the set threshold was reached. Conclusion: The misalignment between a human and a motorized wheelchair in contact with the human is more than several tens of degrees when expressed as the angle change value of the joint motion. We believe that a system that can constantly sense and alert the user regarding whether the user and the PM device are in sync is necessary for PM devices being used in rehabilitation or as daily life support.