Assist Control of Lifting Motion of Lumbar-Powered Exoskeleton Using IMU Sensors

Abstract

According to Japan’s Ministry of Health, Labour and Welfare, work-related lower back pain is prevalent in industries such as commerce, finance, health, and hygiene. Such pain is primarily caused by performing tasks involving heavy lifting and carrying in various fields, including caregiving, transportation, and agriculture. This study proposes a lumbar-powered exoskeleton to assist lifting movements. Passive exoskeletons use springs or rubber belts for assistive force, thus rendering them lightweight but unable to provide controlled assistance based on the wearer’s movements. Active exoskeletons, such as the Hybrid Assistive Limb robot suit, use surface electromyography (sEMG) to detect movement characteristics. However, sEMG is susceptible to noise owing to factors such as sweating and skin contamination. This study proposes a lumbar exoskeleton control method using a nine-axis inertial measurement unit (IMU) that is easy to attach and less affected by the wearer’s state. Convolutional neural networks and long short-term memory models are adopted for posture classification. Tests involving 10 subjects show that integrated electromyographic activity decreased significantly.