Whether you're working in a warehouse or manufacturing plant, how you move product from Point A to Point B will have a lot to do with the productivity of your facility.

While conveyors and lift trucks are the most common solutions, automatic guided vehicles, or AGVs, are an increasingly viable alternative to both in the right application.

An AGV is an operatorless, battery-driven vehicle with programming capabilities for path selection and positioning. While AGVs have traditionally been used in the automotive industry as an alternative to lift trucks, new applications—and new vehicle types—are emerging.

“The automotive and related transportation industries use more AGVs than any other industry,” says Randy Winger, product manager for HK Systems. “But today, we're seeing systems going into other industries, as the vehicles are applied to more diverse applications.”

Those new systems also represent smaller and more strategic applications of the technology: While automotive plants may install 30 or more vehicles, it's not uncommon today to see systems with just four to six vehicles in strategic applications.

“AGVs excel in applications where the pick-up and drop-off points are repeatable, where the vehicle travels to predictable stops, especially over a long distance, and where you're dealing with the regular delivery of palletized or stable loads,” says Mark Longacre, marketing manager for FMC Technologies Automated Systems.

Applications include:

Implementations are typically justified based on savings in three areas:

1. Labor, especially in facilities that require lift truck operators on more than one shift;
2. Improved safety conditions, which can lead to lower workmen's compensation costs;
3. Reduced product damage, since the movements of automatic guided vehicles can be carefully calibrated and programmed.

Anyone considering an AGV system has to make two choices. One involves the type of vehicle needed for the job. The other involves the type of navigation technology that will guide the vehicle.

When it comes to traditional AGVs, four types of vehicles are most commonly used.

Tow vehicles, also known as tuggers, are simple and inexpensive. Like a locomotive pulling rail cars, a tow vehicle tugs trailers or carts. Add multiple trailers and a tow capacity of up to 60,000 pounds, and you can move more loads at one time than with a single lift truck. “Tow vehicles are used where you have a set path with distinct pick up and deposit locations,” says Winger. “They follow a route and stop at stations while people load or unload them.” Customers who use tow vehicles aren't taking all the labor out of their processes, but they are able to automate the movement of materials between workstations.

Unit load vehicles carry pallets, slipsheets, cartons or subassemblies on their decks. These decks may be equipped with:

• lifts that can raise or lower the deck;
• powered or non-powered conveyor to interface with other equipment; or
• multiple compartments to carry two, three or four pallets at one time.

Typically, unit load vehicles are used in totally automated processes. A unit-load vehicle with a section of roller conveyor can integrate with a conveyor line, a production area or an automated storage and retrieval system.

Fork truck vehicles operate just like lift trucks, but without drivers. “Fork vehicles are the most popular vehicle because they are the most flexible,” says Longacre. “They can interface with automated systems, like a unit load vehicle, but they can also pick up or drop off a load onto the floor.”

Custom vehicles can be engineered to handle very large loads like a 20,000-pound roll of steel; unusual loads like a school bus body; or specialized loads like a vehicle designed to handle two different types of pallets or two different sizes of totes.

In addition to selecting the right type of vehicle, you can also select from several different methods to guide the vehicles, called navigation.

Wire-guidance is the simplest form of navigation. An RF signal is transmitted from a wire buried in a slot below the floor to a sensor under the vehicle. The sensor detects the signal and adjusts the position of the vehicle to keep it on the path. Because the slot must be cut into the floor, wire-guided systems are most commonly used where paths are unlikely to change. Despite that limitation, wire-guided systems are still used in applications that require a high degree of accuracy on a path, like an AGV traveling back and forth between two workstations in a congested area.

Magnetic tape and magnetic paint are used to guide vehicles in applications that are relatively simple and where flexibility is paramount. “Customers who change their path all the time can easily reconfigure their routes because neither the tape nor the paint is permanent,” says Winger.

Laser-guidance is the most common non-wire-guided navigation system. An onboard laser reflects off of targets mounted above the floor on columns, walls, machines or posts approximately 25 feet apart. The system automatically measures the distance and angle of the reflected light to calculate and adjust the AGV's position on the preplanned guide paths. “The combination of accuracy and flexibility has made laser the most popular form of guidance,” says Longacre. In fact, last year, laser guidance systems accounted for 43% of the vehicles in Europe and 57% of the vehicles in the United States, Longacre says.

Inertial, or gyro, navigation systems are often used in facilities with a significant amount of random floor storage that might interrupt a laser signal. An onboard gyroscope senses very small deviations in the AGV direction of travel, while small magnets or passive RF tags are installed in the floor approximately every 25 feet along to serve as position points.

In addition to the traditional vehicles most often found in the field, new types of AGVs are coming into the market. Often, these meet specific needs or fill niches not already covered by standard vehicles.

Automatic truck loading vehicles, for instance, have been designed to load pallets and other unitized loads into truck trailers or storage units without an operator. “Truck loading vehicles can work with any standard dock and semi trailer without any modification to the facility,” explains Brian Stewart Sr., vice president and COO of Jervis B. Webb. “And they can load up to four pallets simultaneously.”

While traditional AGVs are often used over long distances, sorting transfer vehicles travel on rails to shuttle loads back and forth between work areas at speeds of up to 600 feet per minute, according to Perry Shore, senior systems engineer for Daifuku America Corporation.

Finally, the market has seen the introduction of a new class of light duty vehicles designed for smaller loads, sometimes referred to as automatic guided carts. In the automotive industry, carts are used to replenish parts at the assembly line or move chassis between workstations. Still others have been designed to handle loads of 1,000 to 3,000 pounds in split case picking and order sortation operations.

“These systems use sophisticated software technology to have the vehicle bring a shelving unit to a worker and then directs picking from that unit,” explains Rob Stevens, vice president of business development for Kiva Systems. “It's taking traditional AGV technology and applying it to new processes.”