This method has been developed to handle the object of unknown weight or unknown surface condition with the most suitable grasping force, by which an object could be grasped in no slip condition nor over grasping force condition. The gripper adapted for this method is constructed by parallel two fingers : one finger is composed of vibrating roller and receiving roller, and another is constructed only by pressing roller. The vibrating roller drives the object by vibrating force and the receiving roller detects the follow-up motion of the object. The slip phenomenon is evaluated by comparing the waveform of receiving roller with that of vibrating roller, and this phenomenon is characterized by the frequency of controlled vibration and grasping force. With this gripper so arranged as mentioned above, the most suitable grasping force can be obtained through the observation of slip phenomena. By the result of experiments, it has been cleared that this method was applicable to real purposes. In the case of grasping objects that surface material is acrylic resin with surface roughness less 1 S, polyurethane rubber with hardness of HS 80-HS 90 is most effective as roller material.
