A series of tags and reader/writers from Escort Memory   Systems Inc. monitor the position and destination of several part-carrying   carts on an 800-ft track in an assembly plant.

A series of tags and reader/writers from Escort Memory Systems Inc. monitor the position and destination of several part-carrying carts on an 800-ft track in an assembly plant.


Hexcel Corp. builds body parts for the Chevrolet Avalanche truck, but due to the large size of the parts, a traditionally sized conveyor system to move components during assembly would be too costly and cumbersome. As an alternative, Hexcel Corp., Stamford, Conn., turned to Ward Systems Inc. in Grass Valley, Calif., for one of its PowerPallet systems. PowerPallet uses intelligent, motorized pallets running on a simple track. But to get the pallets where they need to go, the system needed one more layer of intelligence. Engineers added radio-frequency identification devices (RFIDs) from Escort Memory Systems in Scotts Valley, Calif.

The units, passive reader/writers mounted on the carts and passive ID tags mounted at various intersections along the track, let the carts determine where they are and download approach information for their next programmed stop. This information is used to decelerate and stop at scheduled stations. Since the devices use RF, there's no need for sensor or actuator wiring, no proximity detectors or motors to connect, and RFIDs resist dirt, oil and dust. RFIDs can also be reliably read by the carts despite their speed.