Automatic Warehouse Locating System

Active RFID Systems, Inc. has developed a highly accurate locating system using a family of inexpensive RFID tags that is exceptionally easy to install and set up. The ARS solution provides its customers with a turnkey system that allows them to bypass the complex and costly obstacles often associated with the installation and maintenance of other types of warehouse-locating infrastructures.

The system consists of battery-powered tags that are placed on the ceiling of the warehouse to form a grid. In figure 1 below, a grid formation of ceiling mounted tags with their attendant infrared signal zones and a typical pallet are depicted. This grid is the means by which forklift (and therefore pallet) locations are determined by row and length. The third dimension – stack position – is derived from a sensor attached permanently to the forklift. All data is written to a tag affixed to a pallet and transmitted wirelessly from this tag to the forklift truck and then relayed to a wireless network in the warehouse.

Figure 1: Locating system

The ceiling grid utilizes battery-powered tags which can be adhesively bonded to the ceiling of the storage warehouse. These provide a signal telling the forklift automatically where it is located within the warehouse when it is positioned under one of these tags. These tags are spaced according to the desired warehouse location precision. We recommend a tag be placed every 4-6 feet apart on the ceiling. These tags can operate for 10+ years.

The system also utilizes battery-powered tags, one each, located on the front of each pallet. These pallet tags are dual-mode in that they operate with both infrared and RF. Location data is “written” to these tags automatically when the pallet is positioned within the warehouse. This location and pallet identification value is then wirelessly transmitted to the forklift and then to a network. These tags have a 10-year battery life.

The forklift is equipped with an Active RFID Systems, Inc. customized reader assembly. This device performs the following tasks automatically (without operator interfacing):

  The tag ID is “read” when the forklift is in an area not covered by overhead tags. This becomes the “reference” pallet ID for association with location.

  The pallet row is recorded as the forklift passs beneath the ceiling-mounted tags (see Figure 1).

  The reader continuously monitors the position of the forklift tines as “height above ground”.

  The reader monitors forklift motion and pallet position on the tines to determine when a pallet was actually being placed in a stack.

  When the above occurs, the reader transmits an infrared signal to the tag indicating its height above ground (vertical stack position 1-4); the row the forklift is in, and the location from the reference wall (particular grid tag the forklift is under at time of pallet placement).

  This data is then transferred from the tag back to the forklift reader via RF when the pallet is in position.

  The forklift reader then transmits this data to a central database for processing.

This system does not require new wiring or expensive location mapping. Location mapping is consistent with building walls and overhead tag locations.

This system is expected to have a one-time installation and set-up cost and should operate for a period of 10 years without additional cost. The system provides the location of each pallet within the errors associated with grid spacing. No operator interface would be required for the system to operate.