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  The mechanical structure has been designed considering as basic specifications the possibility of simultaneous application of the contacts and a limited complexity of the kinematic architecture, with not more than three controlled degrees of freedom.

The gripper is shown in a `open' and in a `close' configuration. Three articulated fingers are present and contacts with the grasped object can occur along three intersecting lines equally spaced of 120. Each articulated finger has a distal phalanx, that gets in touch with the object, and two intermediate phalanxes, coupled by means of internal transmissions so that pure translation of the distal link is generated. In addition to the advantage of using only revolute pairs, this kinematic structure presents a high ratio between maximum and minimum extension, obtaining a very large workspace with respect to the size of the gripper body: the positions of the contacts can range from a diameter of 3 mm up to 195 mm, being 120 mm the external diameter of the gripper.

Actuation of each finger is provided by a linear actuator, as shown in figure. The linear actuator is manufactured by Wittenstein Gmbh, Germany, and is composed of a high-speed brushless motor integrated with a high-ratio, high efficiency roller-screw mechanism, that allows direct generation of linear motion

Since the fingers move independently, the grasping configuration may be any triangle with vertices on the approach trajectory segments. This feature allows to grasp irregular objects, even if not positioned in a central configuration with respect to the workspace of the gripper itself.



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