Hollingum, J. (2000), "Guidance system for AGV", Assembly Automation, Vol. 20 No. 3. https://doi.org/10.1108/aa.2000.03320cad.019
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Copyright © 2000, MCB UP Limited
Guidance system for AGV
Guidance system for AGV
Keywords: AGV, Guidance Systems
Applicant: Jervis B Webb Int. Co. (USA)Patent number: EP0942345Publication date: 15 September 1999Title: Guidance system for an automated guided-vehicle
The present invention provides an AGV control system that uses rails for controlling an AGV through high speed portions of a pathway and non-rail controls for guiding it through turns and other low speed portions of the pathway. It eliminates the need to use track or rail switches. The system does not require the monitoring of switches or constant communication with each vehicle because the vehicles are physically constrained to a guide path over the majority of the pathway that they traverse. In the preferred embodiment, a pathway is designed which connects various loading and unloading sites and includes straight sections, branches, and curves. Guiding rails are laid out along the straight sections and gaps are left at the curves and near branches. A non-rail guidance system, such as an in-the-ground wire, is used to continue the pathways between the ends of the rails. The AGVs are provided with steering arms for engaging and following the rail or track sections and sensors for following the in-the-ground wires. Machine-readable tags are positioned at various points along the rail sections to provide information concerning the identity and length of the rail, and the radii of the turns which might be made at the end of the section. The AGVs also include sensors for reading the in-the-ground wires. In operation, a central controller provides an AGV with instructions for travelling from an origin to a destination which tell it which rails to follow and how to turn at the end of each segment. The AGV is inserted into the system at the entrance end of a straight rail section and moved along the rail until it passes an initial reference marker that tells the vehicle where it is. If this location is consistent with its instructions for reaching a destination, it will accelerate to a high speed and travel along the rail looking for additional reference markers. One of these reference markers will tell the AGV the distance to the end of the rail. If the AGV's instructions are to continue in a straight line to the next rail section, the AGV will lock its steering wheels, maintain its speed, and travel past the end of the first rail and on to the entrance to a second rail collinear with the first rail. If the AGV's instructions provide that the vehicle is to make a 90 degree turn to the right at the end of the first rail, the AGV will begin to decelerate when the reference marker indicates that the end of the rail is approaching. The AGV will decelerate to a safe turning speed by the time it reaches the end of the rail and then use its onboard sensors to follow the in-the-ground wire that leads from the end of one rail segment to the beginning of the next. The AGV travels on to the second rail and resumes its high speed. This process continues until the vehicle reaches its final destination.