An Electric Field Pretouch System for Grasping and Co-Manipulation

Pretouch is a sense that is longer range than touch, but shorter than vision. Using electric field sensing hardware that I designed to fit inside a robot’s fingers, several robotic manipulation tasks are made easier or possible.

Human-to-robot and robot-to-human handoff

In this work, the robot is programmed to accept an object from a human, and then hand it to another human.

• First, the e-field pretouch sensors are used to detect the presence of an object that a human is holding up and track the object to center the robot’s hand on it as a human might be moving around.
• Once the sensors detect that the object has stopped moving, the sensors are again used to servo the positions of the fingers to equal distances from the object’s surface, about a centimeter away. This ensures that when the fingers close, they will make simultaneous contact to avoid displacing the object.
• After grasping the object, the robot waits for the human to let go before trying to move away. The human holding onto the object provides an AC path to ground, which the e-field sensors can detect. When the human lets go, this current path goes away and is easily observed in the sensor readings.
• The robot moves its arm to hand the object to another human. Again, the e-field sensors are used to detect whether the human has accepted the object so that it does not let go prematurely.

Picking up stationary objects

We also demonstrated the use of the e-field pretouch sensors to pick up stationary objects from surfaces when only the approximate position of the object is known. Using closed-loop controllers, the sensor inputs are used to correct the positioning of the arm and fingers to facilitate reliable grasps.

Demonstrations

This technology has been featured in several high-profile demos, including:

• CeBIT opening ceremony, Hannover, Germany March 2009
• Intel Developer Forum, San Francisco, CA, September 2008
• Intel Developer Forum, Taipei, Taiwan, October 2008

Videos

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