An automated guided vehicle, or AGV, is essentially a driverless industrial truck. It is steerable, driven by electric motors using storage batteries, and it follows a predefined path along an aisle. AGVs may be designed to operate as a tractor, pulling one or more carts, or may be unit load carriers.

The path followed by an AGV may be a simple loop or a complex network, and there may be many designated load/unload stations along the path. The vehicle incorporates a path-following system, typically electromagnetic, although some optical systems are also in use.

Types of AGV Paths:

Figure 4. Automatic guided vehicle (AGV), designed to transport the world's largest industrial robot. (United Technologies (UTC), Pratt & Whitney Waterjet Systems, Huntsville, AL)

The movable robot is designed to efficiently strip paint from large military aircraft, such as KC-135's and B-1B's using high pressure water. The movable robot may be programmed to accommodate virtually any aircraft configuration, military or commercial, and is easily modified for painting. Under its present configuration, it's estimated that paint stripping costs will be reduced by at least 50%. It's also estimated that paint removing material costs will be reduced by 70% and disposal and treatment costs will decline by 95%.

Figure 6. Laser guided AGV designed to transport steel plates ranging length from 8 to 40 feet. The 43 foot long AGV has a 50,000 pound capacity and is the first "all outdoor" laser guided AGV in the world.

Figure 7. AGV at Saturn used to transport dies.

Figure 8. An AGV that moves the largest jumbo rolls in the world. This type of AGV is used primarily in paper mills and has a capacity of up to 60 tons. Vehicle can be laser or wire guided.

AGV Path Following Systems:

With an electromagnetic path following system, a guide wire carries a radio frequency (RF) signal buried in the floor. The vehicle employs two antennae, so that the guide wire can be bracketed. Changes in the strength of the received signals are used to determine the control signals for the steering motors so that the guide wire is followed accurately.

When it is necessary to switch from one guide wire to another, two different frequencies can be used, with the vehicle being instructed to switch from one frequency to another. The vehicle routing and dispatching system employs programmable controllers, minicomputers or even mainframe computers.

Electromagnetic path following system also supports communication between a host control computer and the individual vehicles. In systems with a number of vehicles, the host computer may be responsible for both the routing and dispatching of the vehicles and collision avoidance.

Optical path following systems use an emitted light source and track the reflection from a special chemical stripe painted on the floor. Optical path control system uses proximity sensors to permit several vehicle to share a loop without a collision.

Smart vehicle can navigate for short distances without an electromagnetic or optical path. These vehicles are equipped with sufficient on-board computing capability to manage some of the routing control and dispatching functions.

Automated guided vehicles (AGVs) classification includes the following types of AGVs:

Figure 10. Unit load AGV

Figure 11. Small load AGV

Figure 12. Tow AVG

Figure 13. Assembly AGV

Figure 14. Storage/Retrieval AGV

These systems are also known as self-powered monorails (SPMs). An SPM moves along an overhead monorail, but rather than being driven by a chain, it is driven by its own electric motor. One of the advantages of SPM is that it does not create obstructions on the factory floor. Since it can be self powered and programmable, it offers a great deal of route flexibility. In contrast to the AGV, it may use a bus bar to provide the electric current required by the drive motors, rather than carrying a storage battery.

Figure 15. Self-powered monorail (SPM)

Another distinctive feature of SPMs is that they require no sophisticated path following system, because the path must conform to the monorail structure. On the other hand, path selection requires coordination between a vehicle-tracking function and a physical track-switching function.

Sorting transfer vehicles,(STVs), automatically load and unload large and small unit loads at pickup and deposit points located around a conveyor loop. The vehicle's rapid and precise acceleration and deceleration, (270 fpm), creates a high throughput unit load handling system.

Figure 16

Figure 17. Sorting transfer vehicles