Data processing: vehicles – navigation – and relative location – Vehicle control – guidance – operation – or indication – Automatic route guidance vehicle
Reexamination Certificate
2002-07-31
2004-09-28
Cuchlinski, Jr., William A. (Department: 3661)
Data processing: vehicles, navigation, and relative location
Vehicle control, guidance, operation, or indication
Automatic route guidance vehicle
C701S200000, C701S201000, C701S207000, C340S995190
Reexamination Certificate
active
06799099
ABSTRACT:
BACKGROUND OF THE INVENTION
This invention relates generally to material handling systems, including sortation systems, monorail systems and the like and more particularly to navigation and/or communication systems for material handling systems.
Automatic guided vehicles, or AGVs for short, are used extensively today in a wide variety of material handling applications. AGVs come in a wide variety of types, from those that carry cargo on their back, to those that tow trains of cargo behind them on carts, to still other types. In order for each AGV to be able to automatically guide itself throughout a factory or plant, it must be able to determine its position within the factory. In the past, the determination of the vehicle's position has been carried out in several different ways. Some AGVs use laser targets positioned at known locations throughout the factory to reflect a laser beam emitted from the AGV. The reflection of the laser beams are detected by the AGV and used to determine the position of the AGV relative to the targets. Using three or more targets, the vehicle can then calculate its position. An example of such a prior art AGV system is disclosed in U.S. Pat. No. 4,790,402 issued to Field et al., the disclosure of which is hereby incorporated herein by reference.
In another type of AGV, the vehicle uses a combination of incremental sensors and one or more beacon sensors to determine its position. The incremental sensors detect changes in the vehicle's position or bearing, while the beacon sensors make absolute measurements of the vehicle's position or heading with respect to one or more fixed beacons positioned throughout the factory. By combining the use of both incremental and beacon sensors, the vehicle is able to determine its position and/or heading sufficiently often and with sufficient accuracy to guide itself to its intended destination. Examples of incremental sensors used on AGVs include wheel encoders that measure the rotations of one or more wheels on the AGV, and gyroscopes that measure changes in the vehicle's orientation. Examples of beacons include magnets buried in the floor, transponders positioned at known locations, laser targets such as those described above, and various other detectable marks or objects. One prior art AGV system that uses wheel encoders, a gyro, and magnets positioned in the floor for navigation is disclosed in U.S. Pat. No. 5,281,901 issued to Yardley et al., the disclosure of which is hereby incorporated herein by reference.
In the past, the various types of AGV systems have each suffered from certain disadvantages. In virtually all of the prior AGV systems, the measurement of the position of the beacons during their installation—whether they are magnets, transponders, reflectors, or other types—has often been a labor-intensive and expensive task. In addition, with respect to the laser-reflector AGVs, these systems require a visual line-of-sight between the vehicle and the target which can often be difficult to obtain in a crowded factory or plant environment. The use of magnets or transponders buried in the floor requires drilling or other operations that can be disruptive to the operation of the factory, and which can have significant costs. Further, the magnets or transponders must be placed on or adjacent to the vehicle pathways in order for the vehicle to be able to detect them. Changes in the pathway therefore often require the installation of additional magnets.
In addition to the foregoing disadvantages of the various navigation systems, prior art AGV systems have also had certain disadvantages in their communications systems. For example, some prior art AGV systems rely on a central controller or repeater that issues or repeats communications received from vehicles. In such systems, the vehicles do not directly contact each other, but instead channel their messages to the central controller or repeater. If a communications failure occurs with the central controller or repeater, then the whole communications system fails. Such single point of failure communication systems are desirably avoided, if possible. Additionally, prior art AGV systems have often used RF communications which are susceptible to interference, especially in plants that have extensive metal structures and electrical/electronic equipment that may emit its own radiation. These problems are also desirably avoided. The need can therefore be seen for an AGV system which overcomes the aforementioned disadvantages.
Prior AGVs have also typically included one or more bumpers on their front and/or back ends that allow the vehicle to safely stop or slow down when objects in its path are detected. Such bumpers may consist of a physical structure that produces an electric signal when impacted, optical sensors that optically detect obstacles in the vehicle's path, laser sensors that detect laser signals emitted from the vehicle and reflected off of obstacles, or combinations of these various types of sensors. One such system is described in more detail in U.S. Pat. No. 5,048,637 issued to Lomasney. While such systems have proven to be adequate, they are often expensive to implement. Furthermore, their detection range for detecting obstacles is often limited such that it is possible for small objects to escape detection by the sensor and possibly cause damage to the vehicle, the undetected object, or both. More inexpensive sensors with a broader field of vision are therefore desirable.
In addition to the use of AGVs to move material between different locations within a warehouse, conveyors and other types of material handling equipment are often used. In order to ensure that the materials are properly moved to their intended destination, they often include a bar code on one of their sides. These bar codes are read by a scanner which is in communication with the appropriate control circuitry to ensure that, after reading the bar code, the material handling system will deliver the article to its intended destination. In order for the bar code scanner to work properly, it is often necessary to make sure that all of the articles are properly oriented so that their bar codes can be read by the scanner. Further, it is often necessary to re-scan articles whose bar codes have become covered in dirt, wrinkled, or otherwise unreadable. A method of tagging articles such that these and other difficulties could be overcome is also desirable.
Sortation systems, such as of the type described in commonly assigned patent application Ser. No. 10/163,788 filed Jun. 6, 2002 by Zeitler et al., use a distributed control having modules that are distributed along a conveying surface. The relative position of the modules is often desirably known so that a higher level controller can properly control the various components of the conveyor system. In the past, the relative position of such components was often determined by normal surveying or measuring technologies. Those techniques are labor-intensive and expensive. A method of reducing those costs is therefore desirable.
Material handling systems that employ overhead electrified monorails to transport material typically use hard-wired communications to communicate with a master controller. These hard wire connections decrease the ease at which the system is installed and/or modified. These systems also typically employ relatively expensive sensors for allowing the monorail vehicle to determine when it has arrived at a particular workstation. The desirability of overcoming these and other disadvantages can be seen.
SUMMARY OF THE INVENTION
Accordingly, the present invention provides improved material handling methods that overcome the aforementioned disadvantages, as well as others. The present invention includes a material handling system that utilizes high frequency radio location transmitters and receivers, also known as transceivers or beacons, for use in navigation, communication, and/or guidance. The use of these types of transmitters and receivers eases the installation of the material handling systems,
Koff Garry
Werner Matt
Zeitler David W.
Cuchlinski Jr. William A.
Hernandez Olga
Rapistan Systems Advertising Corp.
Van Dyke Gardner, Linn & Burkhart, LLP
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