Smart tong grippers for micro-parts

In this paper a new approach for the design of tong grippers for micro-parts is presented. The grippers are made up of two independent jaw-actuator-sensor units that are coupled by an electronic control instead of a mechanical transmission. Electronic coupling of the jaws lowers the need for expensive-precision mechanics and allows extracting information about the gripping situation. Each unit can very precisely position the gripping jaw and measure very small forces. The units act like small adjustable weighing machines. The gripping jaw is guided by a flexure hinge structure. The major characteristic is the frictionless and even movement of the gripping jaws. The jaw movement is driven by a moving coil actuator that takes advantage of the characteristics of the flexure hinge structure. The displacement of the gripping jaw is monitored by a magnetic displacement sensor. This approach allows building smart grippers that are able to analyze the gripping situation. Appropriate actions of the robot could be triggered based upon the gripper's information. Thereby the efficiency of the assembly process could be improved. Prototypes using this approach have been realized. The properties of these prototypes have been tested in an experimental evaluation.