AGVS: Pick Up and Deliver

Aug. 1, 2005
Now that guidance systems have matured, user interfaces have improved, and the installation process has been simplified, automated guided vehicle systems are hitting their stride.

Most people's perception of mobile robotics is some goofy Mars rover," says Robert Wolf, the material handling team manager at Ford Motor Co.'s Romeo (Mich.) Engine Plant. Even though system sales have almost tripled in recent years, Wolf is alluding to a big reason why automated guided vehicles systems (AGVS) aren't even more popular in the United States. Compared to the number of conveyor engineers, for example, relatively few people have the technology exposure and knowledge to recognize good AGV applications within a factory.

Other barriers to the adoption of AGVS have been system complexity, vehicle reliability and costs. At one time only the largest companies—primarily automotive, but also paper-making and printing operations—could justify and afford to put in these multi-million-dollar, robotic material handling systems. Then, following some widely publicized failures, there was the stigma AGVS earned among many of the executives who have to sign off on capital expenses.

"People who don't understand the technology, the Luddites of the world, they can hold up those disasters as an example that the technology doesn't work," says Wolf. He likens such thinking to not getting on an airplane because of the space shuttle disaster. The technology does work, when the application is right, and the installation is managed well. It does require more engineering work than putting in 20 lift trucks. To replace 20 lift trucks with 20 robots "requires a degree of expertise and engineering up front magnitudes above buying fork trucks," he adds.

Today, the biggest driver of AGVS sales is the pressure that all U.S. manufacturers are under to squeeze as much cost out of their operations as possible. While there is no one who couldn't run their factory without an AGVS, many plant managers are finding that the technology can optimize their material flow and achieve a respectable return on investment despite the high upfront costs.

As a rough rule of thumb, the first vehicle tends to cost around $250,000— because of the initial engineering costs— and each additional vehicle costs around $100,000. These costs can be significantly higher or lower depending upon the specific application and vehicle features. Some of the initial outlay can be mitigated through leasing, which a few non-automotive manufacturers are beginning to explore. Because of the accounting benefits, and how rapidly the technology continues to develop, U.S. automakers tend to lease their automated guided vehicles.

The forks themselves offer a good example of why automated guided vehicles are so expensive. Standard AGV forks have optical sensors on the ends to detect the fork pockets and the height marks on racking. The tips are spring-loaded, tripping a limit switch if they encounter too much resistance. Before moving a load, position sensors on the back of the fork detect if a pallet is properly seated.

The primary cost justification for AGVS is reduced labor, usually the most routine kind of labor, moving parts from one location in a facility to another. Other benefits include reduced accidents and product damage. Even though users have difficulty attaching specific cost savings to it, the safety benefits can be significant. This is especially true in automotive, where lift truck drivers often have to drive backward because of the size of the loads, which strains the neck and back. AGVS accelerate and decelerate as they are programmed, and will stop loading a pallet if they run into a broken board, rather than continuing to drive the fork into the load. Monitoring material flow is also simpler compared to operator-driven tuggers or lift trucks. Managers can look at a computer screen and see where all vehicles are located and what their status is.

"The problem was yes, 20 years ago they were a nightmare. Chrysler had them in some plants 20 years ago and tore them out. They couldn't keep them running. That's all changed now," says Jim Petruna, a material handling manager at DaimlerChrysler's Twinsburg (Ohio) stamping facility. "My new units I'll be getting next spring have a new Windows operating system, they have fewer parts, they are simpler to maintain." Improved software will also make it easier for his department to adjust vehicle guidepaths.

Petruna managed the installation of the first AGVS at Twinsburg in 1999. Manufactured by FMC Technologies (Chalfont, Pa.), each of the 32 vehicles now in place has two laser scanners from SICK, Inc. ( Minneapolis). The lasers continually scan in the direction the vehicles are moving, and 30 to 45 degrees to the right and left.

The ANSI standard for guided industrial vehicles (ANSI B56.5) was updated last year to explicitly state that these laser bumpers were acceptable. The previous version of the standard was vague enough that it was up to the manufacturer to decide if they were safe or not. Lasers are better than traditional mechanical hoop bumpers because they can scan further out—the scan distance increases with the vehicle speed—and the vehicle response to various types of obstacles can be programmed. This allows them to move faster. With the increased travel speed an old 10-vehicle system might only require 9 vehicles, lowering the system's initial and operating costs.

At DaimlerChrysler Twinsburg, the "jitney" department performs all of the programming for the laser scanners, as well as the maintenance and repair of the vehicles. This repair and maintenance team of UAW hourly employees has received extensive training on how to repair and service the vehicles. Although he doesn't have data comparing what it now costs to outsourcing such work, Petruna believes AGV maintenance is best done in house because employees have a better understanding of what the machines need to do. They're on site every day, over all three shifts, and they take a certain ownership and pride in their work.

Both inertial and laser-guidance systems have matured in recent years, offering the reliability of wire-in-the-floor systems with much more flexibility, which has always been one of AGVS selling points when compared to conveyors. The first several generations of wireless technology—because of software glitches and hardware that hadn't been proven out in the field— failed to achieve the promised flexibility, ease of installation and cost savings of not having a wire in the floor.

In some cases, those failures were triggered as much by cultural problems associated with putting in automated processes as the technology itself. Perceiving a threat to their jobs, if people wanted to sabotage it they could easily damage the reflectors, or simply drop a box in the vehicle path and stop the system.

Today's wireless technology is as robust as wire-guided systems, with all of the promised flexibility and ease of installation. Of the 120 orders for AGVS in 2004, 88% were for non-wire guided-systems, according to the Automated Guided Vehicles Systems Product Section of the Material Handling Industry of America.

"Laser guidance by itself doesn't make the system flexible. Laser guidance gives it the ability to be flexible but then you need some kind of software tool to be able to redefine your road system," says Mark Longacre, marketing manager for FMC.

What makes today's technology so flexible are tools such as layout wizards that allow engineers to adjust the path and download it wirelessly to the vehicles, which is a far cry from the thousands of dollars it once cost to bring in the equipment vendor to adjust a vehicle path. It also gives users the confidence that they're not spending millions of dollars on a system that will only work with their current plant layout.

"We have customers who change their configurations, change their routings, once per week to adapt their production to match what their customers need," notes Longacre.

In the final analysis the key to the success of any automated system is the installation process, which is a combination of implementing new technology and changing the culture. At Twinsburg, as Petruna relates, the AGVS replaced manual operations in a union facility. In the first year they only installed two vehicles. That time allowed people to become comfortable with the technology, to see that it was safe, and to believe management's message that jobs wouldn't be eliminated. Then they rolled out additional vehicles, adding 6, then 15, followed by eight more. The net result was a better utilization of the workforce, with lift truck drivers staying at the press lines where they were most needed rather than roaming through the plant. Such roaming, they've found, is best left to the robots.

For More Information: The website of the Automatic Guided Vehicle Systems Product Section found on the Material Handling Industry Association site ( features a video explaining the benefits of AGVS, case histories featuring applications in a variety of industries, and electronic lessons that introduce various technical aspects.

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