Automated Guided Vehicles Systems in Production and Operation Management

An automated or automatic guided vehicle system (AGVS) is a materials handling system that uses independently operated, self-propelled vehicles that are guided along defined pathways in the floor. The vehicles are powered by means of on-board batteries that allow operation for several hours (8 to 16 hours is typical) between recharging. The definition of the pathways is generally accomplished using wires embedded in the floor or reflective paint on the floor surface. Guidance is achieved by sensors on the vehicles that can follow the guide wires or paint.

1. Types of AGVS

The types of Automated Guided Vehicles Systems (AGVS) can be classified as follows:

1. Driverless trains: The type consists of a towing vehicle (which is the AGV) that pulls one or more trailers to form a train. It was the first type of AGVS to be introduced and is still popular. It is useful in applications where heavy payloads must be moved large distances in warehouses of factories with intermediate pickup and drop-off points along the route.
2. AGVS pallet trucks: Automated guided pallet trucks are used to move palletized loads along predetermined routes. In the typical application the vehicle is backed into the loaded pallet by a human worker who steers the truck and uses its forks to elevate the load slightly. Then the worker who steers the truck to the guide path, programs its destination, and the vehicle proceeds automatically to the destination for unloading. A more recent introduction related to the pallet truck is the forklift AGV. This vehicle can achieve significant vertical movement of its forks reach loads on shelves.
3. AGVS unit load carriers: This type of AGVS is used to move unit loads from one station to another station. They are often equipped for automatic loading and unloading by means of powered rollers, moving belts, mechanized lift platforms, or other devices. The light-load AGV is a relatively small vehicle with a corresponding light load capacity. It does not require the same large aisle width as the conventional AGV. Light-load guided vehicles are designed to move small loads through plants of limited size engaged in light manufacturing. The assembly line AGVS is designed to carry a partially completed subassembly through a sequence of assembly workstations to build the product.

AGVS technology is far from mature, and the industry, and the industry is continually working to develop new systems in response to new application requirements. An example of a new and evolving AGVS design involves the placement of a robotic manipulator on an automated guided vehicle to provide a mobile robot for performing complex handling tasks at various locations in a plant.

2. Applications of Automated Guided Vehicle Systems

Automated guided vehicle systems are used in a growing number and variety of applications. Its applications can be categorised into the following types:

1. Driverless train operations: These applications involve the movement of large quantities of materials over relatively large distances. For example, the moves are within a large warehouse or factory building, or between buildings in a large storage depot. For the movement of trains consisting of 5 to 10 trailers, this becomes an efficient handling method.
2. Storage/Distribution systems: Unit load carries and pallet trucks are typically used in these applications. These storage and distribution operations involve the movement of materials in unit loads (sometimes individual items are moved) from or to specific locations. The applications often interface the AGVS with some other automated handling or storage system, such as an automated storage/retrieval system (AS/RS) in a distribution centre. The AGVS delivers incoming items of unit loads from the receiving dock to the AS/RS, which places the items in storage, and the AS/RS retrieves individual pallet loads or items form storage and transfer them to vehicles
   for delivery to the shipping dock. When the rates of incoming loads and the outgoing loads are in balance, this mode of operation permits loads to be carried in both directions by the AGVS vehicles, thereby increasing the handling system efficiency.
3. Assembly line operations: AGV systems are being used in a growing number of assembly-line applications. In these applications, the production rate is relatively low and there are a variety of different models made on the production line. Between the workstations, components are kitted and placed on the vehicle for the assembly operations that are to be performed on the partially completed product at the next station. The workstations are generally arranged in parallel configurations to add to the flexibility of the line. Unit load carries and light-load guided vehicles are the type of AGVS used in these assembly lines.
4. Flexible manufacturing systems: Another application of AGVS technology is in flexible manufacturing systems (FMS). In this application, the guided vehicles are used as the materials handling system in the FMS. The vehicles deliver work from the staging area (where work is placed on pallet fixtures, usually manually) to the individual workstations in the system. The vehicles also move work between stations in the manufacturing system. At a workstation, the work is transferred from the vehicle platform into the work area of the station for processing. At the completion of processing by that station a vehicle returns to pick up the work and transport it to the next area. AGV systems provide a versatile material handling system to complement the flexibility of the FMS operation. Example: Using roborts and automation together, manufacturing is carried out without using manpower (unmanned) from raw material to finished products.
5. Miscellaneous applications: Other applications of automated guided vehicle systems include non-manufacturing and non-warehousing applications, such as, mail delivery in office buildings and hospital material handling operations. Hospital guided vehicles transport meal trays, linen, medical and laboratory supplies, and other materials between various departments in the building. These applications typically require movement of the vehicles between different floors of the hospital and will use elevators for this purpose.

Source: KumarAnil, Suresh N. (2009), Production and operations management, New Age International Pvt Ltd; 2nd Ed. edition.