The Basics of Automatic Guided Vehicle Systems

Traffic Management: Forward Sensing Control

Traffic management by forward sensing control uses a sensing system onboard the guided vehicles that detect the presence of a vehicle in front of it. Three types of sensors are used: sonic, which works on a radar principal; optical, which uses an infrared light sources; and bumper, which uses a physical contact of vehicles to cause traffic control. These methods are not effective in path intersection or convergence areas since the vehicle's forward sensing controls look straight ahead and not to the side for intersecting or converging traffic. Therefore, in those areas, these methods have to be augmented by some form of zone traffic control.

In general, forward sensing control is useful where is a lot of straight path in the system and where that straight path is not interrupted by intersection curves. In these methods, wherever the sensing system sees a vehicle in front of it the vehicle goes into a hold and when the lead vehicle moves out of the range of the sensing device the trailing vehicle automatically restarts.

One advantage of forward sensing for traffic management is that vehicles can come quite close to one another and there are no fixed holding points as in zone control methods. This permits a greater density of vehicles in a given area. A drawback is that it can not be used where paths are very dense and complex.