Implementing an AGV System

Controls

Controls/User Interface – This area is somewhat related to the degree of automation issue, but is more specific to the way in which the user interfaces with the controls of the AGV system. There are many ways to approach the user interface with the AGV system.

Onboard AGV Controls – For many standalone AGV systems, particularly tow type systems, the user directs the AGVs via an onboard keypad terminal. This is a very flexible and low cost method, which allows users to select the AGV destinations and respond to varying conditions.

If your system is relatively simple and/or people load or unload AGVs (by hand, with forklift, etc.), then you may only need to use onboard AGV dispatching to operate your system.

Central Control with Distributed Operator Terminals – Systems that incorporate some level of automation with respect to vehicle dispatching or utilize automatic load transfer often employ a centralized control system. These systems have less need for operators to manage the dispatching of AGVs.

Typically, a central controller (usually a PC) manages the AGV dispatching in response to ‘AGV call and dispatching’ requests that are input via operator terminals distributed throughout the system. For example, an operator may place a load on a stand and call for an AGV to pickup the load via a terminal. They may also input a destination for the load. Operators may also use terminal to request a specific product be delivered to their location by an AGV.

Central Control Schemes with Distributed Electronic Interfaces – This approach is also used for AGV systems that employ a level of automated AGV system management and/or automated load transfer. However, rather than employing remote operator terminals, these systems utilize electronic interfaces to initiate AGV calling and dispatching via the central controller.

The AGV central controller receives inputs from these distributed electronic interfaces, which may include photocells, limit switches, PLCs. other PCs or higher level plant computer systems. For example:

• A photocell may be placed at the end of an AGV pickup conveyor to signal when a load is present and ready for transport.
• A PLC controlling a stretchwrapper or palletizer would send a message to the central AGV controller when a load is ready for pickup.
• Or, a plant production control system may send a message to the AGV system that product should be transported from a given location to another location.

In each case, the AGV central controller takes the inputs and manages the AGV dispatching to accomplish the desired task.

Upgrading Controls Approaches – It is not necessary to start with the most automated level of control for a new AGV project. Typically, you can upgrade the level of control at any time. If you are unsure whether a more sophisticated controls approach is warranted or even desirable, specify a simpler scheme to start out with. Also, it is possible to combine approaches in the same system.

Taking Care Not To Over-Specify – When you over-specify you may unnecessarily limit your choices from different AGV companies. Avoid specifying a brand of device or specific type of display or control, etc. Concentrate on functionality desired as this is often achieved differently by different AGV companies.

Over-specifying will cause some AGV companies to considerable increase their price to meet your requirements. Unfortunately, this biases the comparison between competitive proposals and may not be in your best interest because it may mask other weaknesses in an already compliant company.