Laser-Guided AGVs Add Flexibility

Manufacturing Engineering, Jun 2005

"Our original wire-guided AGV system was built in Japan by the same company that designed our ASRS and crane system," recalls Barry Hansis, staff engineer-stamping at Mitsubishi Motors North America (MMNA; Normal, IL). "The AGVs were controlled by a mainframe computer and weren't very flexible. Plus, getting technical support from Japan was very difficult."

After several years of trying to maintain and improve the old system, MMNA installed a new laser-guided system that corrected the problems and eliminated the continual troubleshooting and maintenance needed to keep the old system running. The new system, from AGV Products, Charlotte, NC, is controlled by a Windows-based PC that allows changes in vehicle paths to be accomplished in a few minutes.

MMNA operates two, eight-hour shifts a day, five days a week, using more than 850 robots to produce nearly 180,000 vehicles per year. The plant produces five different vehicles, including Mitsubishi Eclipse, Spyder (a convertible version of the Eclipse), Galant, Endeavor (an SUV), and the Chrysler Sebring and Dodge Stratus.

"We have a stamping facility attached directly to the body assembly area," Hansis explains. "Stampings for the vehicles are produced on-site. Coiled steel is fed into a blanking press producing stacks of blanks used to manufacture the parts. These stacks of blanks are stored in an ASRS until they're ready to be used. When the blanks are needed for production at the transfer press, the AGVs move the stack from the ASRS system to press.

According to Hansis, the AGVs had been used in the stamping area since the plant first opened in 1988. Problems with maintenance and technical support plagued the first system, and vehicle batteries had to be charged several times a shift.

"Our primary goals when searching for a new AGV system were maintenance-free operation and userfriendly system control," Hansis says. "The new system's host computer controls the AGVs, runs the cranes in the ASRS, controls inventory, schedules and controls deliveries, and routes the AGVs. The computer is constantly looking for the most efficient way to route the AGVs. We can also connect with other computer systems throughout the plant."

The new vehicles use a laser-guidance technology that allows vehicle path changes to be accomplished in a matter of minutes, as well as gel-filled batteries that can be quickly charged every time a vehicle returns to its home position. The result is no battery changes and no lost production time.

The vehicles are from AGV Products' Odyssey line, and are equipped with iCon (Intelligent Computer Optimized Navigation) navigational software. They have a laser unit mounted on top of the mast and calculate their coordinates from reflectors permanently mounted all over the shop. All vehicles are equipped with an advanced safety system that includes front, side, and rear sensors as well as a laser bumper detection system.

"In our shop, the paths the AGVs take are fairly static," Hansis says. "However, with the laser guided system it is very easy to change the pathit's just a click-and-drag operation on a PC. Permanent changes to the guide path must be made by our management staff, but special deliveries, inventory changes, error recovery, and daily operations can be accomplished by associates on the floor." Circle 226