Development of upper-limb type HAL and reaching movement for meal-assistance

Having a meal is one of the most basic human activities. There are several hundred thousand patients with upper limb disorders in Japan, who need to be nursed when eating. By letting the patients to perform meals with their own arms, it is expected to promote a more independent life and improvement in their quality of life. In our group we have researched and developed Robot Suit HAL, which is an assistive system to expand, intensify and support human physical function by wearing it. The purpose of this research is developing the upper-limb type HAL(HAL-UL) for meal-assistance. In this paper, we develop a hardware which is able to perform reaching movements of an end-point position and a control method for it. The structure of the HAL-UL has a shoulder joint (three-degree-of-freedom) and an elbow joint (one-degree-of-freedom). The shoulder joint encompasses a ring-shaped rotation mechanism with gears for rotation. Furthermore, a grasp-assistance system is built in the forearm of HAL-UL and performs grasp-assistance. The whole system is fixed to a chair so that weight applied on the user. The control method used for reaching operation is the trajectory tracking control method. In order to calculate a smooth trajectory and the target angles considering the human range of motion, we propose a trajectory calculation method using weighted-pseudo-inverse-matrix and minimum jerk model. The effectiveness of it is investigated through experiments with a healthy person and the HAL-UL actualized reaching movements for meal-assistance.