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Human arm sensors help to make robots smarter

17 January 2014

Using arm sensors that can 'read' a person's muscle movements, researchers have created a control system that could make robots more intelligent.

The arm sensors send muscle movement signals to a computer, which provides the robot with the operator’s level of muscle contraction (photo: Georgia Institute of Technology)

The sensors, developed by researchers at Georgia Institute of Technology, send information to the robot, allowing it to anticipate a human's movements and correct its own. The system is intended to improve time, safety and efficiency in manufacturing plants.

Humans seldom work next to fast-moving robots because of safety reasons. Some jobs, however, require people and robots to work together. For example, a person hanging a car door on a hinge uses a lever to guide a robot carrying the door. The power-assisting device sounds practical but isn't easy to use.

"It turns into a constant tug of war between the person and the robot," says Georgia Tech post doctoral student and project leader, Billy Gallagher. "Both react to each other's forces when working together. The problem is that a person's muscle stiffness is never constant, and a robot doesn't always know how to correctly react."

For example, as human operators shift the lever forward or backward, the robot recognises the command and moves appropriately. But when they want to stop the movement and hold the lever in place, people tend to stiffen and contract muscles on both sides of their arms. This creates a high level of co-contraction.

"The robot becomes confused. It doesn't know whether the force is purely another command that should be amplified or 'bounced' force due to muscle co-contraction," says Georgia Tech's Professor Jun Ueda. "The robot reacts regardless."

The robot responds to that bounced force, creating vibration. The human operators also react, creating more force by stiffening their arms. The situation and vibrations become worse. "You don't want instability when a robot is carrying a heavy door," says Ueda.

The Georgia Tech system eliminates these vibrations by using sensors worn on a controller's forearm. The devices send muscle movements to a computer, which provides the robot with the operator's level of muscle contraction. The system judges the operator's physical status and intelligently adjusts how it should interact with the human. The result is a robot that moves easily and safely.

"Instead of having the robot react to a human, we give it more information," says Gallagher. "Modelling the operator in this way allows the robot to actively adjust to changes in the way the operator moves."

"Future robots must be able to understand people better," Ueda says. "By making robots smarter, we can make them safer and more efficient."

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