Touch Sensor for RobotsNASA's Jet Propulsion Laboratory, Pasadena, California
A touch sensor for robot hands provides information about the shape of a grasped object and the force exerted by the gripper on the object. Pins projecting from the sensor create electrical signals when pressed against the object. The tactile sensor (see figure) is packaged in a small, rugged box that fits on the gripper pad. The projecting pins are arranged in a regular matrix on one face of the box. The inner ends of the pins bear on individual circuit elements. An element may be a switch that turns on when a pin is pushed and makes contact with it, or it may be a variable resistor, the conductance of which increases with the force on the pin. The prototype box is milled from a solid slab of aluminum. In it rests a printed-circuit board carrying the switch electrodes (or pressure-sensitive resistors) and the common electrode. Insulating gaps separate the electrodes from the surrounding electrode plane. Covering the printed-circuit board is a plastic insulating spacer, which confines the pins laterally. On the spacer is a rubber spring sheet. The pins pass through the rubber sheet, which restores the pins to their normal positions when a tactile force is removed. Since the holes in the spring sheet are smaller than the heads and feet of the pins, the sheet confines the pins axially. The sensing pins are electrically and mechanically separated from each other. The circuit for each pin is well defined and independent of the circuits for other pins; crosstalk is thus reduced to a minimum. The rubber spring sheet provides an effective seal around each pin and around the box wall. The sensitive portions of the sensor are deep in the box, protected from the environment; grease, dirt, and fumes have little effect on these portions. Since the box bottom supports the printed-circuit board. the board and the pins are protected from damage by overpressure and overtravel.
Point of Contact:
Howard C. Primus
Jet Propulsion Laboratory
4800 Oak Grove Drive
818-248-2638
Telerobotics Program
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Maintained by: Dave Lavery
Last updated: May 10, 1996