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2nd Quarter 2009 Other technologies

A Technews exclusive from Frost & Sullivan

Robots used along production lines generally operate in protected enclosures to prevent accidents to humans in the factory area. However, an innovative and low-cost robust force sensor has been developed, which helps add sensitivity to the robots in case of collisions.

Consider a hypothetical situation where the arm of an industrial robot moves continuously closer to an employee who is completely absorbed in his work and fails to notice the looming risk. However, as soon as the robot makes contact with the person, it immediately retracts its steel arm or grip away from the person. This kind of solution could be an ideal method to prevent accidents in the production environment. Such a solution is on the verge of becoming a reality.

Silicon sensor

A cost-efficient force and torque sensor developed by scientists at the Fraunhofer Institute for Silicon Technology ISIT, based in Itzehoe, Germany, can be attached to the outer joint of the arm of an industrial robot. The sensor is glued to a steel plate and can be screwed in between the arm and the grabber. Frost & Sullivan understands that this technology would enable robotic assistants to work safely side-by-side with their human counterparts.

The sensor functions by measuring the forces and torques exerted by the robotic arm. Functioning much the same way as a strain gauge, it consists of a long wire that conducts electricity. Upon stretching, the wire becomes elongated, increasing the resistance, and causing less current to flow through it.

The sensor is fabricated on a single square piece of silicon, constituting electrical resistance bridges on either side. In a situation where the robotic arm bumps into a person or obstacle, the shape of the silicon undergoes a minute change of a few micrometers. This change causes a fluctuation in the current flowing through the wire, depending on whether the resistance bridge has stretched or buckled during a collision.

As the sensor consists of just a tiny piece of silicon, it is less vulnerable to errors when compared to conventional techniques, where manufacturers typically glue resistances on to the system separately. This type of arrangement leads to inaccurate positioning of the resistances. This is overcome by the newly developed device in which the resistances are accurately aligned.

The sensor’s size can be customised based on requirements of the application and it is also expected to be less expensive than conventional force sensors when such sensors begin to be mass produced. Such attributes would render the sensors suitable for wide-scale deployment across production areas.

Teach by touch

The sensors could also aid in programming the robots. When in a learning mode, the sensor measures the force used by the employee in guiding the robot arm. As opposed to the tedious task of entering the movements’ coordinates into the computer, a person can merely guide the robot by touch in order to teach the robot the required motion sequences.

For more information on Frost & Sullivan’s technical and market analysis contact Patrick Cairns, Frost & Sullivan, +27 (0)18 468 2315, [email protected], www.frost.com

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