Two and Three-fingered gripper
It's also costly to order custom-made handlers for special parts. To solve these problems, engineers at Barrett Technology Inc., Cambridge, Mass. (barrett.com), developed the Barrett Hand, a three-fingered gripper that can securely hold a wide variety of shapes and parts.
The device has three articulated fingers. The center finger is fixed, and the other
two rotate up to 180˚ around the outside of grips and configurations. Each finger has two sections which act in concert to grab objects.
When the first section touches an object, the second section continues retracting until it is also in contact. With all the fingers in play, and including the palm, the hand can have a seven-point grip on the object. This lets it deal with objects of unknown or inconsistent shapes. The hand can lift about 1.2 kg.
The hand's eight joints are controlled by four brushless-dc motors, all in the wrist section. A torque switch lets four motors control eight axes of motion. The gripper's communications, five microprocessors, sensors, and signal processor are packed inside the palm body. A small umbilical cable connects the hand to an array of robotic arms from different manufacturers.
The mechanism driving the fingers of this Gripper is optimized to obtain two distinct contact regions. The first one, ca base of the fingers, while the second one, end/tip. The boundary between these two adjacent regions is called t
When the contact of the finger with the object to be
grasped occurs in the encompassing grip region, the finger automatically adapts
to the shape of the object and curls around it. On the other hand, when the
contact is made in the pinch grip region, the finger maintains its parallel
motion and the object is pinched.
Since the finger keeps its parallel motion when a contact is made above the equilibrium point during a pinch grip, the same is true for a contact made below the equilibrium point during an inside grip, i.e. for a force applied at the back of the finger. This unique feature allows the Gripper to pick up objects from the inside, which proves to be very useful in many situations.
Coupling between the fingers
In addition to the mechanism used inside each of its fingers, the Gripper also relies on a special coupling architecture between the fingers. In fact, it is mechanically designed to ensure that the two fingers move in conjunction with each other in order to center the object grasped in the middle of the Gripper. This self-centering avoids the need to use expensive sensor sand is above all safer.
In the same vein to make this Robot Gripper as reliable as possible, a self-locking feature has been incorporated into it between the actuator and the fingers. By doing so, we are sure that the Gripper will never release the object and let it fall if the power is shut down. It is also
economically interesting, ase continually the when actuatoran object do is grasped, thus in addition to the power saved, the lifespan of the Gripper is thereby maximized.