Robots are no longer restricted to being used behind physical barriers; they are now entering new fields of application in the manufacturing and healthcare sectors, as well as in households and elsewhere. Researchers form the Fraunhofer Institute say that the requisite safety can be provided by means of a tactile sensor system that can be integrated in a floor or applied directly to robots as an artificial skin.
Consisting of conductive foam, textiles and an intelligent evaluation circuit, a 'skin' type sensor system detects points of contact and differentiates between gentle and strong contact, so it can register contact with people immediately. The shape and size of the sensor cells implemented in the skin can be varied, depending on the application; the higher the number of sensor cells, the more precisely a point of collision can be detected. A sensor controller processes the measured values and transmits them to the robot or, alternatively, a computer, a machine or production line.
Researchers at the Fraunhofer Institute for Factory Operation and Automation (IFF) in Magdeburg, Germany, designed and patented this sensor system in 2008 for its assistant robot Lisa, which stocks incubators and measuring instruments in biotech labs with sample cups and relieves lab staff from such work. Since then the engineers have refined the sensor system for a wide array of applications such as industrial robots and flooring. Contact with humans or objects will be reliably detectable in the future, which is a basic prerequisite for the implementation of robots in human environments without protective barriers.
Markus Fritzsche, researcher at the Fraunhofer IFF, states: "Our artificial skin can be adapted to any complex geometry, including curved or very flat. We use large-area floor sensors to define safety zones that people may not enter. These areas can be changed dynamically."
The tactile skin now also functions as an input medium - for instance, to guide robots by translating contact into motion. Fritzsche continues: "This requires little force. If I touch the robot, it attempts to evade the pressure. Thus, I can direct even a 200kg robot in the desired direction." Another of the artificial skin's distinctive features is the integrated damping elements that additionally diminish any collisions by cushioning impacts.
Diverse variants of the tactile sensor system now exist, and the shell material ranges from breathable to waterproof. Fritzsche says: "This opens entirely new fields of application such as medical engineering or manufacturing. Pressure-sensitive flooring is ideal for monitoring workspaces in factories or instantly registering fallen patients in a nursing home, for instance. Robots and mobile equipment outfitted with the artificial skin register any collision and brake immediately. In addition, we can provide robot grippers a sense of touch and thus detect whether they are actually gripping something."
Numerous variants of the artificial skin have been prototyped. Fritzsche concludes: "We will encounter all sorts of forms of artificial skin in everyday life in the near future."
For more information, visit www.fraunhofer.de
