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Chapter: Mechanical : Robotics : Robot Drive Systems and End Effectors


In robotics, an end effector is the device at the end of a robotic arm, designed to interact with the environment.



In robotics, an end effector is the device at the end of a  robotic arm, designed to interact with the environment. The exact nature of this device depends on the application of the robot.In the strict definition, which originates from serial robotic  manipulators, the end effector means the last link (or end) of the robot. At this endpoint the  tools are attached. In a wider sense, an end effector can be seen as the part of a robot that interacts with the work environment. This does not refer to the wheels of a  mobile robot or the feet of  ahumanoid robot which are also not end effectors—they are part of the robot's mobility.

End effectors may consist of a gripper or a tool. When referring to robotic prehension there are four general categories of robot grippers, these are:


1.   Impactive –jaws or claws which physically grasp by direct impact upon the object.


2.   Ingressive –pins, needles or hackles which physically penetrate the surface of the object (used in textile, carbon and glass fibre handling).


3.   Astrictive –suction [vague] forces applied to the objects surface (whether by vacuum, magneto- or  electroadhesion).


4.   Contigutive –requiring direct contact for adhesion to take place (such as glue,  surface  tension or freezing).


They are based on different physical effects used to guarantee a stable grasping between a gripper and the object to be grasped. Industrial grippers can be mechanical, the most diffused in industry, but also based on suction or on the magnetic force. Vacuum cups and electromagnets dominate the automotive field and in particular metal sheet handling. Bernoulli grippers exploit the airflow between the gripper and the part that causes a lifting force which brings the gripper and part close each other (i.e. the  Bernoulli's principle). Bernoulli grippers are a type of contactless grippers, namely the object remains confined in the force filed generated by the gripper without coming into direct contact with it. Bernoulli gripper is adopted in Photovoltaic cell handling in  silicon wafer handling but also in textile or leather industry. Other principles are less used at the macro scale (part size >5mm), but in the last ten years they demonstrated interesting applications in micro-handling.


A gripper is a motion device that mimics the movements of people, in the case of the gripper, it is the fingers. A gripper is a d evice that holds an object so it can be manipulated. It has the ability to hold and release an object while some action is being performed. The fingers are not part of the gripper, they are specialized custom tooling used to grip the object and are referred to as "jaws." Two main types of action are performed by grippers:


External: This is the most popular method of holding objects, it is the most simplistic and it requires the shortest stroke length. When the gripper jaws close, the closing force of the gripper holds that object.


Internal: In some applications, the object geometry or the need to access the exterior of the object will require that the object is held from the center. In this case the opening force of the gripper will be holding the object.

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Mechanical : Robotics : Robot Drive Systems and End Effectors : Grippers |

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