Development of the Vibration Gripper with the Triangular Grasping Force

This paper describes the fundamental principles of a new vibration gripper. The gripper is able to handle an object of unknown weight and unknown surface conditions with the most suitable grasping force. In this gripper, the grasping force is vibrating with the triangular waveform, and a slip time which the object begins to slip and a cramp time which the slip stops are detected at every period. And the most suitable grasping condition is obtained by such the regulations of the upper and lower values of the triangular grasping force as these times correspond to the references. Because, when these times are the references, the values of the grasping force always becomes the most suitable values. This paper is summarized as follows: (1) Relations between these times and the values of the grasping force against unknown parameters of the object are made clear by the theoretical analysis. (2) The values of the most suitable grasping force are determined by the performance index which evaluates the grasping condition. (3) The references of these times are determined and it is proved that the references are constant against any objects. (4) The control algorithm for this gripper is indicated. (5) The fundamental principles are confirmed in experiments.