As tactile as a human

Jon Lawson

In the latest robot application from APT Automation, a Mitsubishi Electric overhead SCARA robot demonstrates the tactile skills of a human as it handles delicate products with high sensitivity. Real time control and a force sensor enable the robot to seal test tubes gently and securely with a plastic stopper.

In the robot cell designed by APT Automation, the MELFA RH-3FHR overhead SCARA robot carries out the delicate task of inserting plastic stoppers into test tubes and then removing them again. There is no doubt that this process is demanding as handling the fragile test tubes requires an extremely delicate touch.

Malte Stahnke, MD of APT Automation, describes the process: "The robot approaches the test tubes relatively quickly and inserts the stoppers. As the resistance and corresponding force to be applied increase, the speed of the robot decreases until a preset maximum force is reached and the stopper is positioned correctly. It works in exactly the same way as a human would when inserting the stopper manually."

The robot also has a force sensor mounted directly on the gripper which is linked to a control computer. That computer measures the force applied continuously and sends updated positional data to the robot at 3.5 millisecond intervals. As the stoppers are not identical due to manufacturing tolerances, force control needs to be appropriately sensitive. Communication in real time enables the robot to react immediately to increasing resistance.

Malte Stahnke explains: "The robot's actions will depend on the force required and consequently it is as tactile as a human. This calls for real time control – a feature that only Mitsubishi Electric robots offer." The robot is integrated directly in the control system, where the operator can monitor the development of force quickly and easily via a display.

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