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Emerald Group Publishing Limited
Copyright © 2000, MCB UP Limited
Keywords: Robots, Gripper
Applicant: Univ. South Florida (US)Patent number: US5871248Publication date: 16 February 1999Title: Robot gripper
The invention is a robot gripper which uses a non-elastic, flexible material disposed on each gripper's surface so that when the surfaces simultaneously apply compression and lifting forces to the object, a shear force will be generated which will distort the material. When the distortion begins to decrease, it will be safe to lift the object. The method of controlling the gripping force is similar to the way a human controls the gripping force when he or she lifts an object with unknown weight. The lifting and gripping are simultaneously increased in such a manner that the amount of gripping force needed is felt at all times. More specifically, the invention comprises a pair of gripper surfaces with a flexible, non-elastic membrane disposed on each gripper surface. When each gripper surface has made initial contact with the object to be lifted, they simultaneously compress and lift the object. The friction between the gripper surfaces and the object generates a shear force which distorts the membranes. This friction enables the object to be lifted. The principal aspect of the invention is its ability to grip objects of varying mass without having prior knowledge of the object's mass. The membranes disposed on each gripper's surface are composed of cubic cells filled with a compressible fluid and whose walls are made of a non-elastic, flexible fabric. It is the applicants' present belief that as the gripper surfaces simultaneously apply compression and lifting forces to the object, a shear force will be generated which will distort the membrane, and hence the cubic cells contained therein. As the compression and lifting forces are simultaneously increased, the distortion to the cubic cells will also increase until it reaches a maximum. The applicants believe that at this point, the pressure inside the cubic cells is large enough to provide sufficient friction force to lift the object. If the cubic cells are further compressed by increasing the gripper force, the distortion decreases because of the tendency of the fluid inside the cubic cells to maximize its volume. The point at which the distortion starts to decrease is the point at which it is safe to lift the object.