Computer-controlled and wheel-based, automatic guided vehicle (AGV) systems navigate throughout a manufacturing plant or warehouse (or on pavement outside) to retrieve, transport and deliver loads from one point to another. Just as there are a variety of different types of AGVs available to accommodate a broad range of handling needs, there are multiple on-board technologies utilized to ensure the vehicles navigate, maneuver and operate safely.
To help you gain a general idea of the types of technologies that enable AGV operation, here’s an overview of each based on function.
Navigation: Although it may appear that AGVs intuitively know where to go, a variety of sophisticated technologies are used by manufacturers to control the vehicles’ navigation. Navigation systems include:
- Laser Triangulation: A laser scanner mounted on the vehicle continuously strobes to detect reflective targets mounted at known locations. Utilizing triangulation, the vehicle’s control algorithms calculate its precise position.
- Inertial: A sensor on-board the AGV detects reference points (such as barcodes, RFID tags, magnets or other targets) embedded into the floor as the vehicle passes over them. Additionally, an on-board gyroscope measures and maintains the vehicle heading while an on-board wheel encoder calculates travel distance. The vehicle uses feedback from the devices to determine its location.
- Magnetic Tape: The vehicle follows magnetic tape paths adhered to the floor as detected by a sensor mounted to its underside. Navigation is via dead reckoning.
- Grid: A matrix of reference points (typically magnets) embedded into the floor in a grid pattern triggers assigned coordinates stored in the vehicle’s memory as an on-board sensor detects them. Like inertial navigation, the AGV also utilizes feedback from an on-board gyroscope and wheel encoder to determine its location.
- Natural Feature: A camera or laser records and senses uniquely identifiable, naturally occurring features within the vehicle’s operating area, which are used by the AGV to calculate its relative position.
- Wire: Outfitted with on-board antennas that detect the signal emitted by a continuous wire embedded in the floor, the vehicle also uses on-board encoders on its wheels to calculate travel distance and determine its position.
- Optical: On-board sensors detect a chemical or tape strip that has been painted or affixed to the floor.
Safety: Obstacle detection systems prevent collisions between AGVs and people, other moving vehicles, or stationary objects within a facility. Two primary types are used:
- Optical Obstacle Detection Systems: These utilize one or more cameras or safety-rated laser sensors mounted on the vehicle to detect objects within the path.
- Mechanical Bumpers: Physically mounted on the vehicle and made of a flexible material embedded with a limit switch, contact with an object compresses the bumper to trigger the switch and stop the AGV.
Maneuvering: The drive configuration and wheel arrangement of an AGV determines its degree of maneuverability. There are three commonly deployed types:
- Tricycle Drive: The most frequently used type, the vehicles travel atop three wheels: two fixed and one that swivels for steering.
- Differential Drive: Maneuverable enough to rotate around the center of the vehicle, these AGVs feature four wheels — two driven that do not swivel, and two swivel casters. The differing speed and direction of the drive wheels controls the vehicle’s movement.
- Quad Drive: Equipped with two steering and drive wheels, as well as two swivel casters, these AGVs can both rotate around the center of the vehicle and move sideways.
Looking for more details into how AGVs operate? The members of MHI’s AGVS Industry Group recently published a free white paper, “Automatic Guided Vehicle Systems: How They Work,” with more information.