Sensorless Assistive Torque Design for a Lower Extremity Exoskeleton

For improving mobility of the elderly, it is desirable to use a lower limb exoskeleton to enhance strength and endurance for their daily life activities. This paper presents a novel design of assist torque generation and compliant motion of a knee joint for an exoskeleton robot. Based on a sensorless approach, a method is suggested to estimate the external torque and generate the assistance torque of the attached DC motor. The developed lower limb exoskeleton joint provides assistive torque in order to comply with motion of the user. In comparison with existing lower limb exoskeletons, the proposed exoskeleton robot can execute various training programs by adjusting the assisting torque with less sensors and reduced hardware complexity. Experimental results on a knee exoskeleton validate the proposed method. Desirable assistive torque can be generated to be compliant with a swing motion.