Where driverless forklifts work

Simplicity of operation, high quality pallets, and consistent interfaces are among factors that figure into automating the conventional lift truck.

By -- Modern Materials Handling, 12/1/2000

My October column examined the evolution of automatic guided vehicles (AGVs). In particular, I asked whether the development of technology for driverless, conventional lift trucks fits into that progression. It does, up to a point.

Pallet or unit load handling is one area where AGV-like, or automated forklifts, can take over from manned vehicles to some extent. Simplicity of operation, pallet quality, and system interfaces all impact whether we can use an AGV or are limited to a conventional lift truck and operator.

Humans have capabilities ideal for operating a lift truck in a modern warehouse. Probably the most important human skill is the versatility to rapidly adapt to change and to operate under widely different circumstances.

Lift trucks are mobile equipment operating in changing and diverse environments in even the smallest warehouse. It is difficult to define all of these forklift handling tasks precisely. That's why it has been so hard to automate many of them up until now.

In contrast, defining and then automating the more limited number of handling steps at a fixed work station is far easier, generally. This fact explains why robots have made greater headway in replacing humans in fixed location functions such as palletizing.

Before we can have a driverless forklift application, there are several critical interfaces that have to be considered or reengineered.

Certainly, the pallet is one key system interface for using any driverless technology. Consistent pallet quality coupled with a need for achieving proper orientation of the pallet and forklift vehicle performing load pick up or dropoff are both very critical. AGV companies have shown they can readily automate horizontal travel once the vehicle's forks are holding the pallet. But automatically finding the pallet load and positioning the forks prior to lifting the load is far more difficult.

In partially automated warehouses with automatic storage and retrieval systems, there often is a need to bring loads to these systems or take them away. Fixed, unit-load pick up and dropoff locations, sometimes called P & D stations, often serve as the interfaces between these storage/staging systems and other handling activities such as dock staging.

Servicing these P & D stations is an ideal application for driverless forklift technology. The P & D stations are often within 4 feet or less of the floor. An automated forklift readily can make these load transfers. Similarly, an AGV-like lift truck can pick up or drop off at a conveyor interfacing with these systems.

Vertical lifting with an automated forklift, especially as lift heights increase, becomes more of a challenge. Floor flatness, forklift mast sway, and rack system alignment are among the critical interfaces to control. If the floor isn't flat this unevenness is magnified in the deviation of the forklift mast from the true vertical. Lifting height in any particular application will depend upon these and other factors; with automated forklifts we don't have human eyeballs adjusting for off-center pallets in racking and positioning forks correctly. In some systems, lifting by an automated forklift, such as a straddle or stacker vehicle, which also performs horizontal travel, may be limited to 15 feet or so. In other systems it is possible to go higher by controlling mast sway, floor flatness, and rack alignment and, perhaps, by using specialized, in-aisle vehicles.