Abstract
Our objective is to develop soft pressure sensors to control the electric arm prosthesis by measuring the movement of muscles for the control signals instead of EMG. In our previous research, we made refined sensors that has black inner sidewall white inner ceiling at the topside. By using this refined sensor, we succeeded match better controllability of the finger opening speed and finger grasping force. Furthermore, we made a wrist-unit to give a rotational function of hand and drove it by the additional pressure sensors to measure the movement of the ulna and radius. In this study, we tried to install a soft grasping function by monitoring the electric current of the finger driving motor. After the experiment, we knew that the sensitivity is not so good by this current monitoring method. We succeeded to pick up a piece of firm tofu by the arm prosthesis but we could not pick up silken tofu. An over-pushing motion was also necessary to detect the softness by this function. Therefore, we decided to install soft sensors in the fingertips for the refinement of the soft object grasping function. As a result, it had become possible to stably grip without crushing those soft objects in the prosthetic hand. Furthermore, we succeeded in stable gripping the silken tofu. We also developed the pressure detection system around all lower limb surface to detect the suitable points for the control signals. We also demonstrated that we could estimate the wrist angle for the pronation-supination movements by two sensors and trained neural network. According to the estimation of palm flexion - dorsal flexion, the required sensor is only one.
