Automatic guided vehicle system

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A tugger AGV, courtesy of CICMHE/MHIA Multimedia Bank

An automatic guided vehicle system (AGV), or AGVS, consists of one or more computer-controlled, wheel-based load carriers (normally battery powered) that run on the plant floor (or if outdoors on a paved area) without the need for an onboard operator or driver. AGVs have defined paths or areas within which or over which they can navigate. Navigation is achieved by any one of several means, including following a path defined by buried inductive wires, surface mounted magnetic or optical strips, or by way of inertial or laser guidance. See also guidance system and self-guided vehicle.^[1]

History

A unit load AGV, courtesy of CICMHE/MHIA Multimedia Bank

AGVs were first invented in 1953 by an inventor intending to automate the standard "man-on-board" tow truck traditionally employed in factories and warehouses. A wire "track" was imbedded in the factory floor on which the unmanned vehicles traveled. Guidance systems were then developed in order to direct the AGV. These systems employed sensors on the bottom of the truck that looked for a magnetic field. The field was created by running a current through the embedded wire. The truck was then able to follow a given path according to the location of the wire and the data received by the sensor. Using station codes based on north/south combination in magnets, the vehicle could be instructed to stop at a designated station.

A fork AGV, courtesy of CICMHE/MHIA Multimedia Bank

This technology dominated AGV systems until the mid 1970s when solid state controls were developed, which allowed the systems increased capabilities and flexibility. The development of these controls proved to be a catalyst for extreme popularity of AGVs.^[2] In 1973, a Swedish Volvo manufacturer converted its system from a typical conveyor assembly line to a computer-controlled AGV system comprised of 280 AGVs. Soon after, in 1976, the first unit load AGV was produced and implemented. Today, unit load AGVs are used for a wide variety of applications, including automotive assembly and unit load delivery.^[3]

The technology revolving around AGVs continues to evolve. Many systems have moved away from the traditional wire-imbedded AGV and are being equipped with computers used to communicate, direct and manage the system. New vehicle configurations have also proliferated. The basic AGV towing systems still exists. However, automatic call systems, opportunity charging, automatic loading/unloading, and automatic coupling and uncoupling are now available for the right towing application.^[4]

Means of Guidance

Two means of guidance systems can be used for AGV systems:

Fixed path: Fixed path guidance refers to a physical guidepath (e.g., wire, tape, paint) on the floor that is used for guidance.
1. Wire-guided
2. Rail-guided
Free-ranging: Free-ranging guidance has no physical guidepath, thus it is easier to change the vehicle's path (in software), but absolute position estimates (from, e.g., lasers) are needed to correct dead-reckoning error.^[5]
1. Optical-guided
2. Laser-guided