Abstract
We have been investigating a method to operate an electric prosthetic hand by measuring swelling or hardness changes of muscle with a soft-body pressure sensor instead of myoelectric potential. We found that this method is much more stable and easier to operate than myoelectric potential. In addition, it has been shown that it is possible to grasp silken tofu (very soft and fragile food) with an electric prosthetic hand by attaching a soft pressure sensor to the fingertip of the prosthetic hand. We also developed a sensor with three photo-reflectors embedded in a hemispherical balloon-shaped silicone rubber to measure not only the pressure but also the direction of the pressure. In this report, we newly developed fingertip sensors for the fingers of the prosthetic hand. It includes 7 photo reflector elements (4 for 4 soft pressure sensors and 3 for one direction indicator) on the nail and it can measure the attaching position of the finger pad, shear displacement of the finger pad and the compression force of the nail. By using this fingertip sensors, we can pick soft material and we can also break hard objects if necessary. We succeeded in peeling off the shell of a boiled egg by these fingertip sensors installed prosthetic hand.
