Development of Passive Hip-Exoskeleton to Prevent Back Pain during Lifting Work with Cam Mechanism

Abstract

This paper deals with developing a passive hip-exoskeleton designed to prevent musculoskeletal Low Back Pain(LBP) disease which threatens industry worker by supporting lumbar muscle. We selected passive type of exoskeleton as a driving method. Unlike the active type exoskeleton, passive exoskeleton is more low about production cost because it does not use any motor. And passive exoskeleton is not limited by the battery because it does not use any battery. To develop a passive hip-exoskeleton, we first set the lifting technique to the stoop technique. We set the target torque based on the required lumbar moment during lifting 15kg lower-object in stoop technique. Since the objective torque had a sine wave shape, the cam was applied to the passive mechanism to generate the objective torque by providing moment arm with increasing cam radius. And the spring was also applied in mechanism to passive energy storage and release during lifting work. Through this, a passive actuator using cam and spring was made. In an experiment to evaluate the performance of the exoskeleton, subjects lift a 15kg weight with a 3-routine task which similar to real work in the industry. To evaluate the performance, the borg scale and heart rate measurement were used comparing with wearing exoskeleton and not wearing exoskeleton. At result, all wearer had lower borg scale level with the exoskeleton on borg scale during lifting experiment. and all wearer had average reduction rate about increases of average heart rate from starting heart rate by 34.73% than not wearing the hip-exoskeleton and average reduction rate about increases of maximum heart rate from starting heart rate by 26.83% than not wearing the hip-exoskeleton. And all subjects equally did not feel a back pain at lumbar. With the exoskeleton from all wearer feedback in borg scale comparing with without the exoskeleton. So, the exoskeleton can be a solution to assist wearer in actual workplace and to prevent musculoskeletal LBP disease.