The quest to develop a driverless vehicle has taken a long time. A traditional lift truck is a mobile piece of equipment that must operate in multi-functional environments in even the smallest warehouse. It is much more difficult to define the tasks needed to replace the human factor in this type of operation than in a fixed-workstation environment. As a result, robots have made greater headway in replacing humans in fixed-location warehousing functions, such as palletization.
While driverless fork truck technology has been round for longer than a generation, the new models demonstrate enhanced functional capability. To appreciate these, we should consider the evolution of key automated guided vehicle (AGV) functional abilities. The evolution generally progressed through these warehouse applications:
- Horizontal unit load travel (including pick-up and put-down) between fixed points. This was the first typical application for AGVs, and has existed for a considerable period of time.
- Horizontal and vertical unit load travel between a fixed point and certain types of storage systems. This has been around for over a decade.
- Handling of unit load operations between general dock staging and storage. This started within the last ten years.
- Picking a pallet (or two) from a palletizer or storage rack and loading it into a trailer in any configuration. This was the last major hurdle before general replacement of fork truck drivers became possible, and it is now available.
With the exception of full pallet handling, order-picking is still beyond the reach of driverless technology today.
When considering any materials handling application, especially one involving as much change as an AGV, it is just as important to identify what the application cannot do as well as what it can.
A typical sit-down counterbalanced forklift requires a human driver working in tandem with the truck. The truck component for both AGV and a traditional forklift is functionally very similar, particularly in electric battery-powered equipment. But it is more complex for an AGV to complete typical propane truck applications outside the warehouse walls. Muddy surfaces and differing ground dynamics make it tough for the AGV to complete weather-sensitive outside yard work.
When we think of a lift truck and driver combination, we must consider the role a human driver fills. Most importantly, a driver is a control and guidance system directing the vehicle. Operationally, on this level, the task is simple: we have to design an AGV control and guidance system to replace the driver. Secondary functions performed by the driver, including hand-balming and maintenance, are more difficult to substitute for.
Logically, we should thus limit driverless technology applications to unit load handling (the traditional pallet-in, pallet-out scenario) with objects that are able to palletize functionally. If we must handle unstable unit loads of garden racks or shovels, we are back to relying on good old Homo sapiens.
Until very recently, the problem of interfacing trucks with the loading dock has posed a major challenge in adapting driverless technology. But with advances in laser and inertial guidance systems, this is no longer the case.
Initial applications of these advancements can be seen in some shipping interface and local receiving areas (say, to an offsite warehouse under control of a single owner). Because of load shifting, there are still some concerns with receiving long-distance shipments in this way, although this is less of an issue in tightly controlled work environments.
Once the application is properly selected, the AGV system can get to work. A human-driven lift truck has several limitations, many of which are associated with the human workday. In a multi-shift operation, there can be three or even four human drivers to every truck. Replacing these with AGVs in a larger multi-shift application can create payouts in less than two years.
Other benefits include reduced maintenance costs (as abuse by operators is not a problem), the ability to be programmed to work anywhere in the warehouse and the configuration of pre-loads as single or double, depending on the load patterns required.
It is surprising that industry people have not also considered the possible indirect benefits of AGV technology. Take a look at the standard lift truck designs used to carry a driver: stand-up and sit-down. Sit-down designs take much more aisle space than stand-up designs unless specialized VNA designs are employed. But these commonly are two to four times more expensive than a standard counterbalanced truck. By using the driverless model, future designers have the potential to shorten the truck further, further decreasing aisle space.
