Robots developing a sense of touch

UP UNTHL NOW, ROBOTS HAVE NOT been able to tell the difference between something hard like a baseball and something soft like marshmallow.

A robot's sensitivity to touch could soon vastly improve using an array of polymerbased tactile sensors in tandem with a robust signal-processing algorithm to classify surface textures.

The work, performed by a team of researchers at the University of Illinois at Urbana-Champaign, is essential in the development of robots that can identify and manipulate objects in unstructured environments.

"We are developing artificial tactile sensors that will imitate the functionality and efficiency found in biological structures such as human fingers/'said Chang Liu, a professor of electrical and computer engineering at Illinois. "We have shown that simple, lowcost sensor arrays can be used to analyze and identify surface textures."

Biological sensors provide a wealth of information concerning the shape, hardness, and texture of an object. Robots, which typically possess a single pressure sensor in their grip, can't determine whether an object is hard or soft, or how hard it is squeezing an objectOne of the unsolved problems in robotics is the handling of delicate objects such as eggs," said Douglas Jones, a professor of electrical and computer engineering.

"The distributed sensing we have in our hands allows us to grab an egg with enough force that it won't slip, but without so much force that it breaks. One of our goals is to develop an array of sensors that provides robotic systems with a similar source of tactile feedback," he said.

The sensors are from an inexpensive polymer sheet using photolithographic patterning techniques. In the reported work, the researchers created a 4x4 array (16 sensors) and evaluated its performance.

"Each sensor resembles a little drum head about 200 microns in diameter with a tiny bump in the center/'Engel said/On the surface of the drum head, we deposit a thinmetal strain gauge that changes resistance when stretched. Pressure on the sensor is converted into digital data that is sent to a computer and analyzed with a signal-processing algorithm."