Abstract:
The present invention provides systems and methods that reduce the number of mis-routed trolleys in an AGV system. The invention provides a solenoid driven automatic coupling for coupling a trolley to an AGV. When an AGV arrives at a particular preprogrammed destination, as determined for example by track patches read by the AGV, the AGV system switches the solenoid power causing the automatic coupling to free the trolley to disengage from the AGV. The AGV may then pull away from the trolley, leaving the trolley at its programmed destination. The system substantially eliminates the risk of a trolley not being uncoupled prior to the AGV&#39;s departing from the trolley&#39;s intended destination.

Description:
TECHNICAL FIELD 
     The present invention generally relates to automated guided vehicle systems, and in particular relates to a system for automatically uncoupling trolleys. 
     BACKGROUND OF THE INVENTION 
     Automatic guided vehicles (AGV) are widely used in a variety of industrial environments, including factories and hospitals. They move automatically from one location to another, generally following a guide wire or track. They are intended to efficiently transport materials from location to location without requiring a vehicle driver. 
     AGV&#39;s generally pull carriers, referred to as trolleys, on which goods to be transported are placed. Trolleys are attached to the AGV, usually at the back, by couplings. When an AGV arrives at a preprogrammed destination, an operator is responsible for decoupling any trolleys that have reached their destination. 
     Generally, AGV&#39;s are programmed to stop at particular destinations for short periods of time. In most instances, an AGV is programmed to stop for about 1 to 4 minutes. Short waiting periods increase transport system efficiency. However, if an operator fails to meet the AGV while the AGV is stopped and waiting, the AGV continues on to the next destination with the trolley still attached. When this happens, the AGV needs to be rerouted (reprogrammed) through the facility, which diminishes the AGV system&#39;s productivity and worker efficiency. There is an unsatisfied need for more efficient AGV systems. 
     SUMMARY OF THE INVENTION 
     The present invention provides systems and methods that reduce the number of mis-routed trolleys in an AGV system. The invention provides a solenoid driven automatic coupling for coupling a trolley to an AGV. When an AGV arrives at a particular preprogrammed destination, as determined for example by track patches read by the AGV, the AGV system switches the solenoid power causing the automatic coupling to free the trolley to disengage from the AGV. The AGV may then pull away from the trolley, leaving the trolley at its programmed destination. The system substantially eliminates the risk of a trolley not being uncoupled prior to the AGV&#39;s departing from the trolley&#39;s intended destination. 
     One aspect of the invention provides a coupling system adapted to couple an automatic guided vehicle to a trolley including an engagement member and a keeper, the engagement member moveable between an engaging position for engaging the keeper in an interference fit and a disengaging position for releasing the keeper from the interference fit, an actuator, which may be the same structure as the engagement member, moveable between a locking position and an unlocking position, a solenoid acting against the actuator according to a control current, and a controller for switching the control current, wherein switching the control current causes the actuator to move from the locking to the unlocking position, in the locking position, the engagement member is restricted from moving from the engaging position to the disengaging position, and in the unlocking position, the engagement member is either in the disengaging position or is free to move to the disengaging position. 
     Another aspect of the invention provides an automatic guided vehicle including a body and a coupling including a solenoid, the coupling being attached to the body and adapted to engage the automatic guided vehicle with a trolley, wherein switching a control current to the solenoid permits a trolley engaged by the coupling to the automatic guided vehicle to be disengaged from the automatic guided vehicle. 
     A further aspect of the invention provides a method for automatically disengaging a trolley from an automatic guided vehicle including providing an automatic guided vehicle with a coupling and a system for automatically disengaging the coupling and configuring the system to disengage the trolley according to a programmed location. 
     A further aspect of the invention provides an automatic guided vehicle including means for coupling the automatic guided vehicle to a trolley and means for automatically disengaging the trolley from the automatic guided vehicle. 
     A further aspect of the invention provides an automatic guided vehicle system including a plurality of automatic guided vehicles, a plurality of trolleys, and automatically operable couplings for engaging the automatic guided vehicles to the trolleys, wherein the automatically operable couplings release the trolleys according to location of the automatic guided vehicles. 
     The invention extends to features hereinafter fully described and particularly pointed out in the claims. The following description and the annexed drawings set forth in detail certain illustrative examples of the invention. These examples are indicative, however, of but a few of the various ways in which the principles of the invention may be employed. Other objects, advantages and novel features of the invention will become apparent from the following detailed description of the invention when considered in conjunction with the drawings. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     FIG. 1 is a high level schematic of an AGV system according to one aspect of the present invention. 
     FIG. 2 is a high level schematic of a coupling system according to another aspect of the present invention. 
     FIG. 3 is a high level schematic of an AGV system according to a further aspect of the present invention. 
     FIG. 4 a  is a top view illustration of a coupling according to one aspect of the present invention with the actuator in the locking position and the keeper in the engaging position. 
     FIG. 4 b  is a top view illustration of a coupling according to one aspect of the present invention with the actuator in the unlocking position and the keeper in the disengaging position. 
     FIG. 4 c  is a side view illustration along line  3  of FIG. 4 a.    
     FIG. 4 d  is a side view illustration along line  4  of FIG. 4 b.    
     FIG. 5 is an oblique view illustration of a coupling according to one aspect of the present invention with the actuator in the locking position and the keeper moving into the engaging position. 
     FIG. 6 is an oblique view illustration of a coupling according to one aspect of the present invention with the actuator in the locking position and the keeper in the engaging position. 
     FIG. 7 is finite state machine programming diagram illustrating a method according to one aspect of the present invention. 
     FIG. 8 is flow diagram illustrating a method according to another aspect of the present invention. 
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
     FIG. 1 is a high level schematic of an automatic guided vehicle (AGV) system  100  provided by one aspect of the invention. AGV system  100  includes coupling system  110 , which is adapted to couple AGV  130  to trolley  120 . Coupling system  110  includes a solenoid that actuates to disengage trolley  120  according to a control current. Coupling system  110  allows AGV  130  of AGV system  100  to pull trolley  120  and release it automatically upon arriving at a destination. 
     Coupling system  110  is illustrated schematically in FIG.  2 . Coupling system  110  includes engagement member  112 , actuator  114 , solenoid  116 , controller  118 , and keeper  111 . Engagement member  112  moves to engage keeper  111  in an interference fit. Actuator  114  moves to lock the engagement. Controller  118  operates to switch the power to solenoid  116 . When the power to solenoid  116  is switched, actuator  114  is moved to release the lock, whereupon engagement member  112  and keeper  111  may be disengaged. 
     Engagement member  112  is moveable between an engaging and a disengaging position. In the engaged position, engagement member  112  forms an interference fit with keeper  111 . In the disengaging position, keeper  111  may be pulled away from engagement member  112 . Engagement member  112  may be a hook, a latch, a clamp, or any other structure suitable for forming an interference fit with a keeper. Keeper  111  is generally a stationary structure, but it may be a structure that moves as long as it permits engagement member  112  to disengage from keeper  111  when engagement member  112  is in the disengaging position. The interference fit creates a coupling between an AGV and a trolley such that the AGV may pull the trolley along the track. In one aspect of the invention, schematically illustrated in FIG. 3, the engagement member is attached to an AGV and the keeper is attached to a trolley. In another aspect of the invention, the engagement member is attached to a trolley and the keeper is attached to an AGV. 
     Actuator  114  is moveable between a locking position and an unlocking position. When actuator  114  is in the locking position, engagement member  112  is prevented from moving from the engaging position to the disengaging position. When actuator  114  is moved to the unlocking position, engagement member  112  either moves to the disengaging position or is made free to move to the disengaging position. Optionally, actuator  114  and engagement member  112  are combined in a single part, in which case, engagement member  112  necessarily moves to the disengaging position when actuator  114  moves to the unlocking position. Actuator  114  and engagement member  112  are generally attached to a single frame, which is attached to either and AGV or a trolley. 
     When solenoid  116  is energized, it acts against actuator  114 . Switching the power to solenoid  116  causes actuator  114  to move to the unlocking position. In one aspect of the invention, solenoid  116 , when energized, holds actuator  114  in the locking position, and when solenoid  116  is de-energized, a biasing force, a spring for example, moves actuator  114  to the unlocking position. In another aspect of the invention, solenoid  116  when energized move the actuator to the unlocking position. An advantage of this latter configuration is that there is less risk of disengagement due to accidental loss of power to solenoid  116 . The risk of accidental disengagement is further reduced by providing a biasing force, such as a spring, to bias actuator  114  toward the locking position. 
     Solenoid  116  may be any device with an electromagnetically moveable member. Generally, solenoid  116  includes a coil of wire that when carrying a current act as a magnet so that a moveable core is drawn into, or pushed out of, the coil. The moveable core acts against actuator  114  when solenoid  116  is energized. 
     Solenoid  116  is generally attached to a frame along with actuator  114  and engagement member  112 . Where the frame is attached to AGV  130 , the control current for solenoid  116  is generally supplied by AGV  130 . A wire from AGV  130  to the solenoid  116  can be used to carry the control current. Where the frame is attached to trolley  120 , the control current is supplied either by trolley  120  or to trolley  120 . Trolley  120  may carry batteries to supply the power. Alternatively, the control current may be supplied via coupling system  110 , the power source being carried on, for example, AGV  130  to which trolley  120  is coupled. In other words, engagement member  112  and keeper  111  may form electrical connections in their engaged positions and the current thus carried may be used to energize solenoid  116  when solenoid  116  is carried by trolley  120 . 
     The control current for solenoid  116  is switched by controller  118 . Controller  118  is generally mounted on AGV  130  and may be a controller for AGV  130 . Alternatively, controller  118  may be mounted elsewhere, for example on trolley  120  or at a station along the AGV track. Controller  118  typically includes a microprocessor, but may be any device that is capable of switching the control current for solenoid  116  after AGV  130  arrives at a destination. The controller may be analog or digital. If the controller is digital, its instructions may be implemented in either hardware or software. When AGV  130  arrives at station, or shortly thereafter, controller  118  switches the control current causing the engagement member  112  to move to the disengaging position. 
     Controller  118  is generally configured to avoid having engagement member  112  return to the engaging position prior to separation of engagement member  112  from keeper  111 . In one aspect of the invention, controller  118  directs AGV  130  to pull forward prior to switching back the control current. In another aspect of the invention, the destination for the trolley is defined to be at least several feet long, as in a station area, and controller  118  maintains the control current in the switched state until the AGV pulls past the destination. 
     Controller  118  detects, or is notified, by a detection system when AGV  130 , and any attached trolley  120 , has arrived at a destination, such as a station along an AGV track. The detection system includes a sensor, which is usually contained in AGV  130 . For example, controller  118  may be a controller for AGV  130  and AGV  130  may have a sensor for reading patches or other markings on an AGV track that indicate that AGV  130  has reached a station along the AGV track. Alternatively, the sensor could be mounted on trolley  120  or next to the AGV track at the destination. For example, a station along the AGV track may have an electric eye and may signal controller  118  with a radio signal when AGV  130  arrives. 
     AGV  130  may be of any type commonly used to transport goods from location to location within a factory, hospital, or like facility following a predetermined path, referred to herein as a track. Generally, AGV  130  is guided along the track, for example by following a wire, reflective tape, or aluminum foil. The AGV may be provided with a system for following such a track. The AGV may employ any suitable system for follow the track, such as a system providing a laser beam and detecting the beam&#39;s reflections off the track. Alternatively, the AGV may be provided with a GPS system, or similar system, and may follow a path defined in software. 
     Couplings, AGVs and AGV systems of the invention may be conveniently constructed by upgrading existing couplings, AGVs and AGV systems. An AGV with a manually operable coupling may be upgraded to an AGV of the invention by installing a solenoid in a position such that when energized, the solenoid moves an actuator of the coupling to an unlocking position. For example, the coupling may have for an actuator a paddle, which is a broad generally flat member that is conveniently operated by hand or by foot. The solenoid may be installed underneath the paddle, whereby the solenoid moves the paddle as though the paddle where being pressed by an operator. In this configuration, the coupling may be operated either manually or automatically. 
     In the upgraded AGV, if the AGV has a controller, the controller for switching the control current may be the AGV&#39;s controller. In such a case, a wire may be installed to carry the control current from the AGV to the solenoid and the current to that wire may be switched by a controller on the AGV. Alternatively, a controller and or a position sensor may be added to the AGV, as needed. 
     FIGS. 4 a - 4   d  illustrates a particular coupling  400  according to one aspect of the invention. Coupling  400  include frame  410 , solenoid  420 , actuator  430 , and locking bar  450 . Actuator  430  includes paddle  432 , paddle axle  434 , and locking cantilever  440 . Paddle axle  434  pivots around paddle shaft  436  held in paddle housing  437  mounted on frame  410 . Paddle spring  438  biases actuator  430  to the locking position, in which paddle  432  is up and paddle axle  432  is down. Paddle axle  432  is connected to locking cantilever  440 . Locking cantilever  440  pivots about locking cantilever shaft  442  and is biased to the locking (lower) position by locking cantilever spring  444 . Locking bar  450 , which is the engagement member, pivots about locking bar shaft  452  and is biased by locking bar spring  454 . 
     Coupling  400  engages with keeper  460 , which includes a vertical bar. When locking bar  450  is rotated counterclockwise to what may be referred to as the disengaging position, keeper  460  may be pressed into end  412  of frame  410 . As illustrated in FIGS. 5 and 6, keeper  460  causes locking bar  450  to rotate against the force of locking bar spring  450 . Keeper  460  turns locking bar  450  until locking bar  450  reaches a clockwise rotated position, the engaging position, wherein keeper  460  is trapped in an interference fit formed by locking bar  450  and front end  412  of frame  410 . In the engaging position, end  446  of locking cantilever  440  may engage corner  456  of locking bar  450  and thereby lock locking bar  450  in the engaging position. The lock is formed if actuator  430  is in the locking position and is released if actuator  430  is moved to the unlocking position. The engagement between locking bar  450  and locking cantilever  440  is secured by locking bar spring bar spring  454  and locking cantilever spring  444 . 
     Coupling  400  may be disengaged by energizing solenoid  420 . When energized, solenoid  420  overcomes the biasing force of paddle spring  438 , lowers paddle  432  and raises paddle axle  434 . This is the disengaging position. When paddle axle  434  is raised to the disengaging position, locking cantilever  440 , which is connected to paddles axle  434 , is also raised, causing locking cantilever  440  to disengage with locking bar  450 . Once locking cantilever  440  is disengaged from locking bar  450 , locking bar  450  is free to turn to the disengaging position and the keeper will pull easily away from coupling  400 . 
     When solenoid  420  is de-energized, actuator  430  returns to the locking position. If locking bar  450  is still in the engaged position, locking bar  450  will again be locked in the engaged position. A trolley engaged to an AGV by coupling  400  must therefore be separated from the AGV before the solenoid is de-energized, if it is desired to leave the trolley behind. Separation from the trolley may be accomplished by keeping solenoid  420  energized until the AGV has pulled forward a short distance. For example, a system using coupling  400  may keep solenoid  410  energized until the AGV leaves the trolley&#39;s destination area. 
     FIG. 7 is a finite state machine programming diagram of a method of operation for an AGV according to one aspect of the present invention. Initially, the controller is in the Base Station state, the AGV is at the base station, and the control current is in what will be referred to as the un-switched state, whereby the actuator is in the locking position. After a user attaches a trolley and programs its destination, the controller moves to the In Transit state and the AGV proceeds down the track. When a destination is detected, the controller moves to the Destination Check state. If the destination is an attached trolley&#39;s destination, the controller moves to the Decoupling state. If not the controller proceeds to the Base Station Check state. If at the Base Station, the controller waits for further programming. Optionally, while in the Base Station Check state, the AGV may stop at the destination and allow time for an operator to couple a trolley and program its destination, perhaps an empty trolley to be taken to the base station. 
     In the Decoupling State, the AGV stops and the power to the control current is switched, whereby the actuator moves to the unlocking position. If the destination is the Base Station, the controller proceeds to the Base Station state, wherein the control current is un-switched. Optionally, before returning to the Base Station state, the AGV may pull forward slightly to uncouple the trolley. If the destination is not the base station, the control current remains switched until either the destination area has been left or an operator has attached another trolley and programmed its detination. In either case, the controller goes to the In Transit state where the control current is un-switched. The AGV may wait in the Decoupling state for a few minutes to allow time for an operator to attach a trolley and program its destination. 
     The base station and destination areas may be defined in any convenient manner. For example, the base station may be a storage area of a warehouse, hospital, or factory. The base station may also be a charging station for AGV&#39;s. Destinations may be, for example, a work area, another storage area, or a loading stations. The AGVs generally travel in a closed loop along a pre-programmed route, but the methods of the invention are easily adapted to allow the AGVs to be routed more dynamically. 
     FIG. 8 is a flow diagram illustrating another methodology for carrying out the present invention that permits several trolleys having differing destinations to be pulled by one AGV. In step  600 , an operator couples, with couplings of the invention, a train of trolleys to the AGV. The operator programs a controller with the trolleys&#39; destinations and performs any other necessary initialization steps. In steps  610  the trolley leaves the base station and begins following the AGV track. In steps  620  and  630 , the controller checks whether the AGV has reached the destination for the end trolley in the train. In step  640 , if the AGV has reached the end trolley&#39;s destination, the AGV stops and the controller switches the appropriate solenoid to disengage the end trolley. In step  650  the controller checks whether more trolleys are attached. If so, the AGV continues down the track checking for the end trolley&#39;s destination. If not, the AGV returns to the base station and waits for reprogramming and reloading. The method is easily modified to permit additional trolleys to be added at the destination stations. 
     What is described above is the present invention and several of its specific aspects. It is, of course, not possible to describe every conceivable combination of components or methodologies for purposes of describing the present invention, but one of ordinary skill in the art will recognize that many further combinations and permutations of the present invention are possible. Accordingly, the present invention is intended to embrace all such alterations, modifications and variations that fall within the spirit and scope of the appended claims.