The Basics of Automatic Guided Vehicle Systems

Load Transfer: Power Roller, Belt, Chain

Powered roller belt or chain transfer for guided vehicles has been a standard technique for many years. Unit load carriers can be equipped with these power decks so that they may automatically transfer loads to and from fixed stations. In certain cases, under light load conditions, parasitic drives can be used which allow the AGV unit load carrier vehicle to interface with a non-powered roller stand. Most applications involve the AGV vehicle dropping off to a powered or gravity type conveyor. A roller deck transfer method can be used on AGVS towing systems where the towed trailers are equipped with powered transfer deck mechanisms. In all cases, the vehicles must precisely align with the given transfer station before the load transfer can be achieved. Normal stopping tolerances are + or -1/2" which is well within the tolerances required at conveyor transfer stations.

Whenever a vehicle is automatically transferring a load, a method or "handshake" logic must be employed. Handshake logic is the method by which the vehicle checks to make sure a load stand is empty before it automatically transfers a load onto the stand. Or when a vehicle comes to pickup a load it must make sure that there is a load on the stand for pickup before the load transfer occurs. The handshake signals between the vehicle and the load stand allow transfer drives to be activated simultaneously to achieve the load transfer. The signals also turn off the drives when the transfer is complete. The handshake method usually involve sensors onboard the vehicle which interface with sensors on the stand that exchange signals when a load transfer is about to occur. If the proper signals are not exchanged, then the vehicle will not attempt the transfer. It can blow its horn or abort the mission and proceed to another destination.