Patent Publication Number: US-9416554-B2

Title: Vehicle parking with automated guided vehicles and vehicle lifts

Description:
CROSS-REFERENCE TO RELATED APPLICATION 
     This application claims priority on U.S. Provisional Patent Appl. No. 61/914,014 filed on Dec. 10, 2013, the entire disclosure of which is incorporated herein by reference. 
    
    
     BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     The invention relates to an automated parking facility with automated guided vehicles for moving trays with or without the passenger vehicles thereon and vehicle lifts to permit plural vehicles to be stored in a single space. 
     2. Description of the Related Art 
     Municpalities throughout the world continue to grow in size and population density, and the number of vehicles in a municipality varies directly with the population size and density. Most municipalities have zoning ordinances that control the number of parking spaces required for all new construction so that real estate developers provide sufficient parking for residents, tenants employees and customers of new real estate developments. The required number of parking spaces generally is a function of the number of residential units and the square footage of office and retail space. 
     Suburban real estate developers generally can provide a sufficient number of parking spaces with grade level lots in proximity to the real estate development. Parking garages generally are not required for suburban real estate development and those parking garages that may be required generally do not present complicated design difficulties. 
     Real estate developments in urban areas are much more likely to require parking garages, and parking garages in urban areas are much more likely to present design problems. For example, profitability of an urban real estate development is a function of the ratio between the size of the lot and the amount of development that can be placed on that lot. Tall buildings are more likely to be profitable, but also require more parking. A parking garage can be built adjacent to the residential, retail or office building. However, the parking garage adjacent to the new construction limits the amount of the site that can be used for developing the residential, retail or office space. As a result, parking garages often are built below the building that will be served by the parking garage. Above grade parking garages are less costly than below grade parking garages. However, above grade parking garages often are aesthetically unattractive and detract from the architectural appearance of the new building. Below grade parking garages are aesthetically more attractive, but can be cost prohibitive, particularly in coastal areas where flooding is a concern. 
     Municipal ordinances also are likely to control the size of each parking space and the width of parking aisles to ensure that parkers have sufficient room to maneuver into and out of parking spaces and throughout the parking garage. 
     Real estate developers can request zoning variances in situations where the zoning ordinance is too burdensome for a particular site. However, the real estate developer must demonstrate that an acceptable alternate can be provided to the specific parking requirements established by the zoning ordinance. 
     Devices have been available for decades to permit two or more cars to be arranged vertically in a single parking space. The typical device of this type has a platform with sufficient structural rigidity to support a vehicle thereon. Piston/cylinder arrangements or pulleys with chains or cables are provided to raise or lower the parking platform with or without the vehicle thereon. The typical parking platform has a sloped entrance ramp that the vehicle negotiates to enter onto the parking platform. An employee of the parking facility then actuates the lift mechanism to elevate the parking platform with the vehicle thereon. Another vehicle then can be driven into the space below the parking platform. Many such parking devices have more than one parking platform and hence permit more than two vehicles to be parked in a vertical array. Examples of parking devices of this type are shown in U.S. Pat. No. 4,772,172 and in U.S. Pat. No. 7,597,521. 
     Parking lots that rely upon vehicle lift devices require considerable room for the vehicle owner and/or the parking lot operator to maneuver vehicles from the entrance of the facility to the appropriate vehicle lift device. Most parking lots and parking garages that rely upon this technology do not have automated systems for locating the vehicle or for organizing the stacked arrangement of vehicles. As a result, a significant amount of maneuvering is required to park or retrieve a vehicle. These parking systems tend to be very labor intensive and create the potential for minor accidents as the vehicles are being maneuvered by employees of the parking lot. 
     Recent work by the assignee of the subject invention has related to the use of automated guided vehicles (AGVs) to move vehicles throughout a parking facility. AGVs are highly maneuverable and precisely controllable. Therefore, an AGV is well-suited for moving vehicles in the tightly confined spaces of a parking facility. AGVs typically would be used in combination with parking trays. More particularly, each parking tray may have a generally planar supporting platform on which the vehicle can be parked and legs extend down from the supporting platform to keep the supporting platform and the vehicle thereon in a slightly elevated position. The AGV is dimensioned to move between the legs and under the supporting platform. Elevating mechanisms on the AGV then can be activated to lift the tray and the depending legs slightly from the floor of the parking facility. The AGV then will maneuver the parking tray and the vehicle thereon to an appropriate parking space in the facility. The AGV then may leave the parked car and the tray and move to another location in the parking facility for moving another tray and another vehicle either into or out of the parking facility. The combination of AGVs and parking trays typically will be used with vertical reciprocating conveyors (VCRs) to permit vehicles to be moved between floors of a parking garage. Systems of this type avoid the need to have the parker drive to and from the parking space. Rather, the parker merely deposits the car on a tray at and ingress bay and retrieves the car later from a tray that has been moved to an egress bay. Parking systems of this type also reduce the labor costs associated with having workers move cars through a parking facility and into the parking spot and then having workers retrieve the cars from the designated parking spot. The recent work in connection with parking facilities that use AGVs, parking trays and VRCs can achieve operational efficiencies and some modest space efficient sees in view of the ability of AGVs to maneuver precisely in confined spaces. However, the systems that use AGVs, parking trays and VRCs generally are not expected to achieve large space savings or vastly improved parking densities. 
     AGVs have not been considered suitable for use with the above-described devices that enable a plurality of vehicles to be arrayed vertically in a single parking space. More particularly, the very low riding AGV that is suitable for a parking facility is not capable of negotiating the ramp that leads onto the parking platform of the prior art lift device. Additionally, the mechanism of the prior art parking lift device generally is actuated by an employee who has driven the car onto the parking platform. As a result, the manual control of the parking lift device would offset labor efficiencies of the AGV 
     Accordingly, an object of the subject invention is to provide a highly automated parking facility that can achieve significant increases in parking density. 
     SUMMARY OF THE INVENTION 
     The invention relates to an automated parking system with a parking structure or location that has at least one level, and typically plural levels or floors. The parking structure or location has at least one bay for ingress and/or egress of vehicles. At least one vertically reciprocating conveyor (VRC) is provided for moving vehicles between the access point and a parking floor in the parking structure. The system further includes at least one automated guided vehicle (AGV) that can transport at least one vehicle within the parking structure. The system may also include a plurality of trays, each of which has a parking platform and a plurality of legs depending down from the parking platform so that the parking platform is supported in a sufficiently elevated position to enable the AGV to drive between the legs and under the parking platform of the tray. The AGV is configured to left the tray with the vehicle thereon slightly from the floor of the parking facility so that the AGV and can transport the tray with the vehicle thereon. 
     The parking structure or location comprises a plurality of parking spaces, each of which has a lift device that preferably is suspended from the ceiling of the parking structure. Each lift device comprises a tray support and a hoist mechanism that preferably includes a motor, pulleys and chains or cables extending from the tray support around the pulleys and to the hoist mechanism. Thus, the hoist mechanism enables the tray support to be moved from a lower position where the tray support is on the floor of the parking facility and an elevated position where the tray support is spaced sufficiently from the floor of the parking facility to enable a vehicle to be driven under the tray support. The tray support preferably is a generally U-shaped structure with two parallel arms having opposite front and rear ends and a transverse beam extending between the rear ends of the arms. The front ends of the arms of the tray support either are not connected to one another or are connected by a thin flat plate material that can rest on the floor. The arms of the tray support are spaced sufficiently apart to enable an AGV to be driven between the arms. Each tray support may have a plurality of brackets disposed to engage the legs of the respective tray. More particularly, the brackets may be formed with sockets or apertures that are configured to nest with the lower ends of the legs of each tray. The sockets or apertures of each tray support may have a tapered entry to ensure efficient guiding of the legs of the tray into the corresponding socket or aperture. Portions of each arm in proximity to the front and rear ends thereof are connected to the chains or cables of the lift device. The hoist mechanism can act on the chains or cables to lift or lower the tray support with or without the tray and the vehicle supported thereon. 
     The parking system of the invention operates by using the AGV to transport empty trays from the egress bay either to the ingress bay or to a storage magazine near the ingress bay. The empty tray may be deposited in a recess in the ingress bay or the egress bay so that the top parking surface of the tray is substantially flush with the approach surface for a vehicle entering the ingress bay or the exit surface for the vehicle leaving the egress bay. An approaching vehicle is guided by electro-optical signage and/or by audio instructions so that the vehicle can be positioned properly on the tray. The positioning of the vehicle on the tray is assessed by photo-optical sensors in the ingress bay and signage that will guide the driver of the vehicle to a proper stop position at which the vehicle is supported properly on the tray. The driver will exit the vehicle and may receive a receipt that can be used to reclaim the vehicle. The receipt can be a paper or cardboard receipt or an electronic receipt that can be loaded electronically onto a cell phone or other electronic device. Alternatively, the driver can use a credit card and a regular parker may merely use an assigned PIN. The sensors in the ingress bay may be operative for determining when the driver and any passengers have departed the vehicle and the ingress bay. The sensors also may determine the condition of the vehicle so that pre-existing damage can be documented. The tray with the vehicle thereon then is prepared for transport to the VRC. This preparation can include elevating the tray/vehicle combination sufficiently for engagement by an AGV that will transport the tray/vehicle combination to a VRC. Preferably, however, the AGV driving surface in the parking structure may be at the same level as the surfaces in the ingress and egress bays that support the trays. Thus, the AGV merely drives under the trays, lifts the tray and the vehicle thereon with the platform lifts and then transports the tray/vehicle combination from the egress bay toward the VRC. The parking structure can include a queue area between the ingress bay and the VRC for storing the tray/vehicle combinations while waiting for an elevator to become available. 
     The tray/vehicle combinations are loaded onto a VRC either by the conveyor system or by an AGV, which then leaves the VRC with the tray and the vehicle therein. The VRC then transports the tray/vehicle combination to a selected floor for storing the vehicle. The floor and the storage location are selected and stored by the central controller of the parking facility. The location may be selected based on an intended parking duration or pickup time designated by the driver at the ingress bay. Once at the proper floor, another AGV will move between the legs of the tray and into a position for supporting the tray and the vehicle thereon. The platform lifts of the AGV then will activate to lift the tray sufficiently for the weight of the tray and vehicle to be supported by the AGV with the legs of the tray at a slight distance from the floor. The control unit of the AGV then will control the drive devices to move the AGV with the tray/vehicle combination thereon to the selected location on the floor of the parking structure. In this regard, the motors of the respective drive devices can be operated in accordance with independent instructions received from the control device on the AGV so that the wheels can be powered independently for guiding the AGV along an appropriate route to the selected parking location. Movement of the AGV to the selected parking location is dictated by input received by Hall effect sensors on the AGV upon passing in proximity to magnets on the floor. Alternatively, movement can be guided by embedded wires in the floor of the parking facility or by bar code readers on the AGVs and bar codes on the floor. Hall effect sensors are preferred. In this regard, the information sensed by the Hall effect sensors can be used to adjust the alignment of the AGV, to turn the AGV about an axis perpendicular to the parking floor, to reverse the movement of the AGV and to change the movement from, for example, and X direction to a Z direction. 
     While the AGV is approaching the selected parking location, the lift device at the selected parking space will lower the tray support, if no vehicle currently is on the tray support or in the parking space. The AGV then will move between the front ends of the arms of the lowered tray support and toward the transverse beam at the rear end of the tray support. The AGV will align the legs of the tray to engage with the sockets or apertures in the brackets that project from the arms of the tray support. The platform lifts of the AGV then will lower so that the legs of the tray will nest with or engage in the sockets or apertures on the respective arms of the tray support. The AGV then may depart from the tray/vehicle combination and may proceed back to the VRC, as guided by the Hall sensor on the AGV and the magnet arrays on the floor. The AGV then may await the next arriving tray/vehicle combination. Alternatively, the AGV may travel to retrieve a vehicle that must be delivered to the egress bay or may remain parked at the parking space to which the vehicle had been delivered. Meanwhile, the lift device at the parking space at which the vehicle had been delivered is activated to lift the tray and the vehicle to an elevated position, thereby freeing the floor surface of the parking space to receive another vehicle therein. 
     The above described process for parking a vehicle is substantially reversed for retrieving the vehicle. More particularly, an AGV will be guided to the vehicle location by the Hall sensor on the AGV and the magnet arrays on the floor and will move between the legs and under the tray is supported directly on the floor. The platform lifts of the AGV will activate to raise the tray sufficiently for the legs to be spaced slightly from the floor. The AGV then will transport the tray/vehicle combination from the space and either back to the VRC so that the vehicle can be transported to the egress bay for pickup by the driver or to another space so that a previously elevated vehicle can be accessed. In the latter situation, the lift device will lower the tray support with the tray and the vehicle thereon down to the floor. The AGV then we will move between the arms of the tray support from the front end of the tray support toward the rear end. The platform lifts of the AGV then will activate to raise the trays sufficiently for the legs to be separated from the sockets or apertures of the tray support so that the AGV with the tray and the vehicle thereon can be moved from the parking space and toward the VRC. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is a front elevation view of a parking structure that includes the system of the subject invention. 
         FIG. 2  is a cross-sectional view taken along line  2 - 2  of  FIG. 1 , and showing the ground floor where vehicles enter and exit a multi-floor parking facility. 
         FIG. 3  is a cross-sectional view taken along line  3 - 3  of  FIG. 2 . 
         FIG. 4  is a cross-sectional view taken along line  4 - 4  of  FIG. 2 . 
         FIG. 5  is a top plan view of a portion of an upper level floor of the parking facility where vehicles are parked, and further showing the magnet arrays on the upper level floor of the parking facility. 
         FIG. 6  is a top plan view of one embodiment of a magnet array in accordance with the invention. 
         FIG. 7  is a perspective view of a tray in accordance with the invention. 
         FIG. 8  is a side elevational view of the tray. 
         FIG. 9  is a side elevational view of an automated guided vehicle in accordance with the invention. 
         FIG. 10  is a top elevational plan view of the automated guided vehicle on a parking floor and in proximity to two of the magnet arrays. 
         FIG. 11  is a bottom perspective view of the automated guided vehicle of  FIG. 9 . 
         FIG. 12  is a bottom plan view of one end of the automated guided vehicle. 
         FIG. 13  is a cross-sectional view taken along line  13 - 13  in  FIG. 12 . 
         FIG. 14  is a cross-sectional view taken along line  14 - 14  in  FIG. 12 . 
         FIG. 15  is a perspective view of a drive device for the automated guided vehicle. 
         FIG. 16  is a top plan view of the drive device. 
         FIG. 17  is a bottom plan view of the drive device. 
         FIG. 18  is a side elevational view of the drive device. 
         FIG. 19  is a cross-sectional view of a parking facility showing two floors and front elevational views of vehicles parked on those floors. 
         FIG. 20  is a cross-sectional view of the parking facility shown in  FIG. 19 , but showing the vehicles viewed from the side. 
         FIG. 21  is a top elevational view of the tray support of the vehicle lift device. 
     
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT 
     A parking garage in accordance with the invention is identified generally by the numeral  10  in  FIGS. 1-5 . The parking garage  10  includes an ingress bay  12  and an egress bay  14 , each of which is dimensioned to receive an automotive vehicle. At least one vertical reciprocating conveyor (VRC)  16  is disposed in proximity to the ingress and egress bays  12  and  14 . Additionally, a queue area  18  is disposed between the ingress bay  12  and the VRC  16  to accommodate vehicles that are waiting for the VRC  16  to become available. Automated doors preferably are provided between the queue area  18  and in the ingress and egress bays  12  and  14  to prevent customers from accessing the queue area  18 . The doors to the queue area  18  will be open only after the customer has left the ingress or egress bays  12  and  14 . The parking garage  10  further includes a plurality of floors that can be accessed by the VRC  16 . Each floor includes a plurality of areas where vehicles can be parked. Each floor has a plurality of magnet arrays  20  affixed to the floor at positions spaced apart, for example, by approximately 10 feet. Each magnet array  20  includes a plurality of magnets  22 . The pattern of positive and negative poles of each magnet  22  within each magnet array  20  is specified to define unique addresses or signatures for the magnets  22  and the magnet arrays  20 . Each magnet  22  preferably is a thin planar structure attached to a sheet  23  or laminated between two sheets  23 . The sheet  23  of their respective magnet array  20  band is affixed to the floor by adhesive or mechanical attachment members at a specified location and in a specified orientation. 
     The parking system of the invention utilizes a plurality of trays  24 , as shown in  FIGS. 3, 4, 7 and 8 . Each tray  24  includes a substantially rectangular parking platform  26  with a top surface  28  for supporting a vehicle thereon and a bottom surface  29 . Legs  30  project down from the parking platform  26  for supporting the parking platform  26  in a spaced position from the floor. The legs  30  may flare outward or inward slightly so that a plurality of parking trays  24  can be nested vertically for storage and transportation. 
     The ingress and egress bays  12  and  14  each include a recessed floor  20  dimensioned to receive one of the trays  24  or a magazine of trays  25 , as shown in  FIGS. 3 and 4  and as explained further below. The recessed floor  20  is lower than the floor  21  at other locations in the ingress or egress bays  12  or  14  by a distance substantially corresponding to the height of the tray  24  or a height of the magazine. Thus, the top surface  28  of the parking platform  26  will be substantially flush with the floor  21  adjacent the recessed floor  20  when the tray  24  is positioned on the recessed floor  20  in the ingress or egress bay  12  or  14 , as shown in  FIGS. 3 and 4 . As a result, a vehicle that enters the ingress bay  12  can drive across the floor  21  and onto the upper surface  28  of the parking platform  26  of the tray  24 . Similarly a vehicle on a tray  24  in the egress bay  14  can drive from the upper surface  28  of the parking platform  26  of the tray  24  onto the floor  21  of the egress bay  14  and out of the parking garage  10 . The floor in the queuing area  18  is substantially flush with the floor in the recess  20  as shown most clearly in  FIG. 3 . At least one movable platform  31  is provided in proximity to the recessed floor  20  in the ingress bays  12  and the egress bay  14  and can be moved between first and second positions. The upper surface of the movable platform  31  is flush with the floor  21  and flush with the upper surface  28  of the parking platform  26  of the tray  24  when the movable platform  31  is in the first position so that a passenger easily can exit or enter the vehicle in the ingress bay  12  or the egress bay  14  by walking across the movable platform  31 . The upper surface of the movable platform  31  is displaced sufficiently in the second position so that the space under the tray  24  can be accessed for lifting and moving the tray  24 , as explained further herein. The movement of the platform  31  between the first and second positions can be vertical, horizontal or a combination of vertical and horizontal movements. 
     The parking system of the invention also includes automated guided vehicles (AGV)  32  for transporting the trays  24  throughout the parking garage  10  with or without vehicles thereon, as shown in  FIGS. 9-18 . Each AGV  32  includes a substantially rectangular frame  34  that includes an interior  36  for accommodating the operative parts of the AGV  32 . More particularly, the interior  36  of the frame  34  includes an array of rechargeable batteries  38  for providing power to operate the AGV  32 . The batteries  38  communicate with one or more recharging connectors  40  in a peripheral region of the frame  34 . Additionally, the interior of the frame  34  includes a controller  42  for controlling the various operative parts of the AGV  32  as explained herein. The controller  42  further includes a transmitter and a receiver for communicating with a central control for the parking garage  10 . The interior of the frame  34  of the AGV  32  further includes a Hall effect sensor apparatus  43  that communicates with the controller  42 . The Hall effect sensor apparatus  43  includes an array of Hall effect sensors  45  to sense the magnets  22  in each magnet array  20  as the Hall sensors  45  moves into a position opposed to the respective magnets  22  of the corresponding magnet array  20 . The number of Hall effect sensors  45  in the Hall effect sensor array  43  can be selected in accordance with the desired sensitivity and the size and complexity of the parking garage  10 . In one embodiment, the Hall effect sensor array  43  has 16 rows and 27 columns. 
     The AGV  32  further includes four platform lifts  44  disposed within the interior  36  of the frame  34 . More particularly, two platform lifts  44  are disposed in proximity to each of the respective longitudinal ends of the AGV  32 . The two platform lifts  44  at each end of the AGV  32  are connected to a tray support platform  46  that can be raised or lowered relative to the frame  34 . At the lowered or retracted position, the tray support platforms  46  are substantially flush with the upper surface of the frame  34 . In the raised or extended position, the tray support platforms  46  project slightly above the upper surface of the frame  34 . The platform lifts  44  and the respective tray support platforms  46  are used to raise and lower the trays  24  with or without vehicles thereon as explained herein. 
     The AGV  32  further includes four drive devices  50  disposed at corners of a rectangle and disposed inwardly of the elevator mechanisms  44 . Each drive device  50  includes two wheels  52  mounted for rotation about a horizontal axis  54 . The two wheels  52  of each drive device  50  are driven respectively by two drive motors  56  so that each wheel  52  has a dedicated drive motor  56 . The assembly of wheels  52  and drive motors  56  on each drive device  50  is mounted to a turntable  60  so that the assembly of wheels  52  and drive motors  56  on each of the drive devices  50  can be rotated about a vertical axis. The turntable  60  freely rotatable about a vertical axis and is driven rotatably by the wheels  52  and their respective drive motors  56 . The drive motors  56  are operated independently pursuant to signals received from the controller  42  of the respective AGV  32 , which in turn is driven by controls of the parking garage. 
     The longitudinal and lateral dimensions of each AGV  32  enable the AGV  32  to fit between the legs  30  of a tray  24 . Additionally, the height dimensions of each AGV  32  enable the AGV  32  to fit beneath the parking platform  26  of the tray  24  when the tray is supported on the legs  30 . 
     In use, a tray  24  will be positioned on the recessed floor  20  in the ingress bay  12  of the parking garage  10  at a position so that a vehicle can drive across the floor  21  of the ingress bay  12  and onto the parking surface  28  of the parking platform  26  of the tray  24 . Electro-optical signage in the ingress bay  12  will guide the driver of the vehicle to a proper position on the tray  24 . The driver then will exit the vehicle and issue appropriate instructions regarding parking duration and payment method. The instructions may be delivered verbally to an employee of the parking garage  10  or may be delivered electronically, as explained above. The movable platform  31  will move to the second position after the driver and any passengers exit the ingress bay  12 . An AGV  32  then will move from the queue area  18  and into the space beneath the parking platform  26  of the tray  24  so that the tray  24  and the vehicle thereon can be raised and moved to the queue area  18  and/or the VRC  16 . This process can be carried out in reverse at the egress bay  14 . More particularly, an AGV  32  can deliver a tray  24  and the vehicle thereon onto the recessed floor  20  in the egress bay  14 . The AGV  32  then will exit the egress bay  14  and return to the queue area  18 . The movable platform  31  then will move from the second position to the first position where the upper surface of the movable platform  31  is flush with the floor  21  in the egress bay  14 . The driver and any passengers then will be permitted to enter the egress bay  14  so that the vehicle can exit the parking garage  10 . 
     The tray  24  with the vehicle thereon then will be transported to the VRC  16 . This transportation between the ingress bay  12  and the VRC  16  can be carried out by any of several optional means. Preferably, an AGV  32  will move beneath the tray  24 . The platform lifts  44  of the AGV  32  then will be moved into their extended positions so that the tray  24  with the vehicle thereon is elevated slightly from the floor  20  so that the AGV  32  can transport the tray  24  and the vehicle thereon to the VRC  16 . Alternatively, a conveying mechanism can move the vehicle from the ingress bay  12  to the VRC  16 . 
     The VRC  16  will move the tray  24  with the vehicle thereon to a selected floor in the garage  10  for parking. An AGV  32  then will transport the tray  24  and the vehicle to a preselected parking location. More particularly, the AGV  32  will move between the legs  30  of the tray  24  and into a position for properly supporting the tray  24 . This accurate positioning can be determined by the Hall sensor  43  on the AGV  32  and the magnet arrays  20  on the floor. The proper positioning of the AGV  32  relative to the tray  24  will be transmitted to the controller  42  of the AGV  32 , which will generate a signal to operate the platform lifts  44  of the AGV  32 . The platform lifts  44  will cause the tray support platforms  46  to move into the extended position so that the tray  24  with the vehicle thereon is lifted sufficiently for the legs  30  of the tray  24  to be spaced from the floor. The controller  42  of the AGV  32  then will issue appropriate signals for operating the drive devices  50  of the AGV  32 . More particularly, the control of the AGV  32  will cause the drive motors  56  to drive the wheels  52  so that the AGV  32  delivers the tray  24  and the vehicle thereon to an appropriate pre-designated parking location. In this regard, the drive motors  56  all can be operated independently of one another pursuant to instructions received from the controller  42 . In some instances, the motors  56  on a single drive device  50  will be operated in opposite directions for turning the turntable  60  to steer the AGV  32  in the required direction. The operation of the drive devices  50  will be carried out in coordination with the signals received by the Hall effect sensors  45  on the AGV  32  as the AGV moves over the respective magnet arrays  20 . As noted above, the magnets  22  of each magnet array  20  has a unique combination of positive and negative poles so that the Hall effect sensors  45  can identify a particular magnet  22  as the AGV  32  moves the Hall effect sensors  43  over the magnet array  20 . The Hall effect sensor array  43  will be able to identify the particular magnet array  20 , and hence can determine the specific location of the AGV  32  on the floor of the parking garage  10 . Additionally, the Hall effect sensor array  43  will identify the particular magnetic  22  in the magnet array  20  to determine both the position and the alignment of the AGV  32 . The magnet array  20  and the Hall effect sensor array can be considered to have rows of magnetics  22  extending in a left to right direction relative to the primary travel direction of the AGV  32  and columns extending in the primary travel direction of the AGV  32 . The Hall effect sensor array  43  also has rows and columns of Hall effect sensors  45  will be able to identify the left-right position of the AGV  32  depending upon the particular magnetic  22  in the first row of magnetics in the magnet array  20  that is sensed as the respective Hall effect sensors  45  of the Hall effect sensor array  43  move into a position above the magnetic array  20 . If the next magnetic grid  22  sensed by the Hall effect sensor  43  is in the same column, the controller  42  will determine that the AGV  32  is traveling parallel to the columns. However, if the second magnetic  22  sensed by a particular one of the Hall effect sensors  43  is in a different column of the magnet array  20 , then the controller  42  will determine that the AGV  32  is moving in a direction skewed with respect to the alignment of the columns of magnetic grids  22 . Thus, an appropriate corrective instruction can be issued to the drive devices  50  of the AGV. 
     Each designated parking space  70  is provided with a vehicle lift device  72  suspended from the ceiling  74  of the parking facility  10 . The vehicle lift device  72  includes a motor  76 , a general U-shaped tray support  78  and cables or chains  80  extending between the motor  76  and the corners of the tray support  78 . The U-shaped tray support  78  includes two parallel arms  82  having opposite front and rear ends  84  and  86  and a transverse beam  88  extending between and the rear ends  86 . Brackets  90  project in from the arms  82 . The brackets  90  are configured and disposed to engage the legs  30  of a tray  24 . The motor  76  preferably is actuated to lower the tray support  78  to the floor of the parking facility  10 . 
     Once at the designated parking location, the controller  42  of the AGV  32  will him cause the AGV to move between the arms  82  of the tray support  78  and into a position where the legs  30  of the tray  24  align with the brackets  90  of the tray support  78 . The controller  42  of the AGV  32  then will issue instructions to the respective platform lifts  44  to retract the tray support platforms  46  sufficiently for the legs  30  of the tray  24  to rest on and engage with the brackets  90  of the tray support  78 . The controller  42  of the AGV  32  then may operate the drive motors  56  to move the AGV  32  away from the tray  24 . The AGV  32  then will be guided to another location by the Hall effect sensor array  43  and the magnet arrays  20  for performing more work, such as returning another tray  24  and the vehicle thereon to the appropriate VRC  16  to have the vehicle delivered to the egress bay  14 . The motor  76  of the vehicle lift device  72  then lifts the tray support  78 , the tray  24  and the vehicle thereon to the elevated position so that another tray  24  with another vehicle thereon can be moved into the space beneath the tray support  78  as shown in the figures. In each occurrence, the AGV  32  can leave the parking space after depositing the tray  24  and the vehicle so that additional work can be performed by the AGV  32 . Alternatively, as shown in  FIGS. 19 and 20 , the AGV  32  may remain parked temporarily at the parking spot while awaiting an additional assignment. 
     The invention has been described with respect to certain preferred embodiments. However, other changes within the scope of the invention will be apparent to those skilled in the art after having read this description of the preferred embodiments and the accompanying drawings.