Abstract:
Apparatus for determining the position of an elevator car within a hoistway that includes a code rail containing optically readable indicia that is being mounted within the hoistway adjacent to the path of travel of the car. At least one camera is mounted upon the car for movement therewith for scanning the code rail indicia and providing data indicative of the car&#39;s position to the car controllers.

Description:
FIELD OF THE INVENTION  
         [0001]    This invention relates generally to an elevator, and more specifically to method and apparatus for determining the position of an elevator car as the car moves along a hoistway.  
         BACKGROUND OF THE INVENTION  
         [0002]    In order to bring an elevator car to a smooth, safe stop, level with a landing, the car controller must have reliable information concerning the movement and position of the car in order to know when to initiate car leveling and stop procedures as well as the opening the car doors. To carry out these functions accurately, it is necessary to know the car&#39;s exact position at all times.  
           [0003]    Many existing reference systems are based on incremental encoders and vanes which can be mounted in a variety of arrangements within the hoistway. In one arrangement, an endless tape having slots formed along its length is attached to the car and is trained about idler sheaves located at the top and the bottom of the hoistway. One sheave contains teeth that mate with the slots in the tape so that the sheave is driven by the endless tape. An encoder is driven by the toothed sheave and provides primary car position information to the car controller. Additional discrete position sensors and vanes are located at each landing to provide secondary car position information that is used to bring the car to a smooth, safe stop at each landing.  
           [0004]    A second widely employed position determining system involves an encoder that is mounted upon the shaft of the elevator drive motor. Car position data is determined by the encoder unite and is processed and used to derive the car speed and the distance to a landing information concerning the various floors. Additional sensors and vanes are again needed at each landing and the position of the elevator car as derived by the encoder is checked and corrected if needed each time the car passes a vane at a landing.  
           [0005]    Although these existing systems work well in practice, they have certain drawbacks in that most prior art systems of this type are relatively expensive to install, and are difficult to adjust and costly to maintain. Error correction is also necessary at each landing in order to compensate for rope slippage or the like. The car&#39;s position relative to the landings is generally measured indirectly by an encoder and the position information is acquired incrementally. This data, therefore, must be saved in memory in case of a system shutdown. This, in turn, requires the use of batteries to power the memory during a shutdown. When position data is lost, correction runs must be carried out to reestablish position references and the system must be recalibrated often as the building housing the elevator system settles. Finally, as noted above, most prior art position reference systems require redundant position sensors and vanes at the landings to insure positive detection of the car, as it approaches the landings.  
         SUMMARY OF THE INVENTION  
         [0006]    It is therefore an object of the present invention to improve elevators, and, in particular, to improve positioning systems used to control elevators.  
           [0007]    It is a further object to provide a non-contact absolute positioning system for an elevator that will not be adversely affected by side-to-side or front-to-back movement of the elevator car.  
           [0008]    A still further object of the present invention is to eliminate the need for correction runs and recalibration of an elevator position system after a power loss.  
           [0009]    Another object of the present invention is to reduce the cost of installing and maintaining an elevator system.  
           [0010]    Yet another object of the present invention is to provide a redundant speed measuring system for an elevator without the need of providing additional encoders.  
           [0011]    Yet a further object of the present invention is to continually correct an elevator positioning system as a building in which the system is housed settles.  
           [0012]    These and other objects of the present invention is attained by a system for determining the position of an elevator car within a hoistway in which the elevator car is mounted for reciprocal movement. In one form of the invention, a vertically disposed code rail containing optically discernable information is mounted within the hoistway adjacent to the car&#39;s path of travel. An optical sensor is mounted upon the car for movement therewith. The sensor is positioned to optically read code rail indicia related to the hoistway and feed this information to the car controller. The code rail can be a continuous strip running along the vertical length of the hoistway or code rail indicia on independent code rail sections, each of which being located at a particular landing.  
           [0013]    In another form of the invention, a single sensor is arranged to read a code rail strip extending along the length of the hoistway to acquire primary position data and at the same time, read individual code rail sections at each landing to acquire secondary position data.  
           [0014]    In a further embodiment of the invention, two sensors are secured to the elevator car in vertical spaced apart alignment and arranged to read two vertically separated code rail sections simultaneously to acquire a range of position related information. 
       
    
    
     BRIEF DESCRIPTION OF THE DRAWING  
       [0015]    For a further understanding of these and other objects of the present invention, reference will be made to the following detailed description of the invention which is to be read in connection with the accompanying drawing, wherein:  
         [0016]    [0016]FIG. 1 is a perspective view of an elevator system embodying the teachings of the present invention;  
         [0017]    [0017]FIG. 2 is an enlarged side elevation in section showing a CCD equipped camera suitable for use in the practice of the present invention;  
         [0018]    [0018]FIG. 3 is an enlarged view showing the image of the code rail that is projected onto a camera&#39;s CCD imager;  
         [0019]    [0019]FIG. 4 illustrates a further embodiment of the invention wherein a pair of vertically aligned cameras are mounted upon the elevator car so that each camera can view a separate code rail sections mounted upon the door frames of adjacent landings;  
         [0020]    [0020]FIG. 5 is a view similar to FIG. 4 further illustrating how the two-camera system can be used to find the relative positions of two adjacent code rail sections once the building has settled;  
         [0021]    [0021]FIG. 6 is a view similar to FIG. 4 illustrating how the relative distance between adjacent landings and between all landings can be calculated using information acquired by the present two camera system; and  
         [0022]    [0022]FIG. 7 is a view similar to FIG. 4 illustrating how the present two camera system can be used to calculate the gap between two adjacent code rail sections.  
         [0023]    [0023]FIG. 8 is a view similar to that illustrated in FIG. 8 showing the camera image of the same landing after the building housing the elevator has settled; and  
         [0024]    [0024]FIG. 9 is a further embodiment of the invention showing the use of a continuous code rail strip mounted in a side-by-side relationship with individual code rail sections that are located at adjacent landings and further illustrating the camera image of the code rail strip and a code rail section recorded by the image sensor;  
         [0025]    [0025]FIG. 10 is a partial view in perspective illustrating a further embodiment of the invention. 
     
    
     DETAILED DESCRIPTION OF THE INVENTION  
       [0026]    Turning initially to FIG. 1, there is shown an elevator car, generally referenced  10 , that is suspended by rope  11  between a pair of guide rails, one of which is depicted at  12 . As is well known in the art, the car is arranged to move reciprocally over a vertical path of travel within a hoistway  15  that is housed within a structure having several floors. The car is equipped with a controller  30  which contains a processor that is programmed to carry out a number of car related control functions and a memory for storing position related data. To perform these and other control functions accurately, it is necessary that the processor receives accurate and sufficient information so that it is able to determine the car&#39;s exact location at all times within the hoistway. As will be described in greater detail below, the present invention employs one or two non contact sensors to acquire data for determining the car&#39;s position within the hoistway at all times and conveys this information to the elevator controller where it can be processed and utilized in carrying out various related control functions. As will further be explained in greater detail below, the sensor may be an optical device such as a CCD or CMOS equipped camera or an LED equipped reader for reading spaced apertures in a coded strip. Other forms of readers are also contemplated for use in the practice of the present invention such as infrared sensors or the like.  
         [0027]    The car, in one embodiment of the invention, is equipped with a pair of cameras that include a lower camera  19  and an upper camera  20  that are focused upon a series of adjacent code rail strip  22  so that the cameras can record images of indicia  23  carried upon the strip. The two cameras are spaced apart so that the center axis  24  and  25  of the cameras are located at a fixed vertical distance D from one another. Accordingly, each camera scans a different area of the code rail strip as the car moves over its vertical path of travel. Although two cameras are employed in this embodiment of the invention, it will become evident from the disclosure below that one camera can be utilized in a further embodiment of the invention without departing from the teachings of the present invention.  
         [0028]    As further illustrated in FIGS. 2 and 3, the cameras  19  and  20  are both of similar construction and include a charge couple device (CCD)  21  for recording scanned images of the code rail strip. Each camera contains a lens or lens system  32  located at the distal end of the camera housing  26  for focusing an image of a code rail target  34  that surrounds the center axis of each camera upon the CCD imager. The CCD imager is mounted within the housing upon a substrate  28  along with the imager support circuitry. The image data from the imagers are fed to a signal amplifier  29  and is then forwarded to the cab controller  30  where the position data is processed and utilized in various related elevator control functions. Some of the data may also be stored in memory and periodically updated as necessary.  
         [0029]    [0029]FIG. 3 illustrates a section of a code rail strip  22  in which each indicia is given a specific number with the indicia value increasing in an upward direction. The division or space between adjacent numbers is of equal distance along the length of the hoistway section. Although the divisions may be of any desired value, the division numbers are given in centimeters in the present example. The enlarged image of the scan area  34  that is recorded upon the CCD imager is depicted at  33  with the center axis  24 ,  25  of the camera being shown at point  36  where the vertical and horizontal diameters intersect. In this example, the axis of the camera is focused at a point somewhere between the upper position number which is 70 centimeters and the lower position number which is 60 centimeters. The camera, in association with the controller, optically identifies the upper and lower division number using well known optical character recognition techniques. The CCD imager contains a large number of pixels that are arranged in a raster pattern of horizontal rows and vertical columns. The position of the camera axis with respect to the code rail is now determined by counting the number of pixel rows separating the axis of the camera from the upper and lower division numbers which, in this example, is 237 pixel rows from the upper division marker and 198 pixel rows from the lower division number. Applying the following relationship: 
           ABSPOS−LOWPOS+N 2·( HIGHPOS−LOWPOS )/( N 1+ N 2)  (1) 
         [0030]    where:  
                                       ABSPOS   is the position of the camera axis       LOWPOS   is the lower division number       HIGHPOS   is the high division number       N1   is the number of pixel rows separating the camera axis and the           upper division number, and       N2   is the number of pixel rows separating the camera axis and the           lower division number.                  
 
         [0031]    Solving the relationship for this example: 
           ABSPOS= 60+198·(70−60)/(237+198)=64.55 cm 
         [0032]    The location of the camera axis is at a vertical location of 64.55 cm above the lower datum plane of the code rail strip.  
         [0033]    In this embodiment, each camera takes a picture of the tape at predetermined intervals as for example 5.0 milliseconds. Based on the position of the camera relative to the numbered indicia on the strip, the camera image determines the position of the elevator in the hoistway using both optical character recognition and pixel counting. The code rail may be a continuous strip as shown, or can consist of a series of individual code rail sections that are applied directly to the door frames at each landing or any other fixed position relative to each of the landings. The cameras are positioned so that at least one camera sees at least one of the code rail sections at all times. This arrangement allows for on the fly generation of a continuous position reference.  
         [0034]    As should be evident front to rear or side to side motion of the car will not adversely effect the measurements provided that the camera can see both the high and low divisions and their associated numbers because the term ABSPOS is dependent upon the ratio of N1/N2.  
         [0035]    A fully redundant position references system can also be implemented using two vertically spaced cameras  19  and  20  separated a distance D, as illustrated in FIG. 1. As further illustrated in FIG. 4, in this embodiment of the invention a vertical series of individual code rail sections  35 - 38  are utilized, with each individual section being located at one of the landings. Each section contains a series of indicia markers  39  which are spaced 0.25 m apart. The code rail sections are each separated by a gap distance (d) as shown between code rail sections  35  and  36 . The gap distances can be equal or unequal provided each gap distance is less than the vertical separation (D) between the cameras. The code rail sections are encoded as shown with numerals, each of which indicates a position within the hoistway. Although the numbers represent absolute distances from a given reference point, it should be evident to one skilled in the art that the numbers may represent any value that will enable the elevator controller to determine the exact car position within the hoistway in a unique, non-repetitive manner. Code rail sections may also be mounted in express zones that do not have landings, provided that the gap between the sections remains less than the vertical distance between the cameras. Although at times a first camera may be traveling in the gap zone between code rail sections, the second camera is providing data to the controller. The position of the first camera, however, in relation to the second camera is always ascertainable by the controller because the first camera will remain a given distance (D) from the second camera. As should now be evident, the system utilizes discrete code rail sections to provide continuous absolute positioning data to the car controller.  
         [0036]    An elevator car  10  is shown in FIG. 4 with the car platform  40  being level with the door sill  41  at landing  4 . The lower camera  19  at this time is positioned to read data on the code rail section  35  which is mounted upon the door frame, of the landing  4  with the reading being taken along the axis  24  of the camera at 15.00 meters. The central axis  25  of the upper camera  20  is spaced vertically a distance D from that of the lower camera. At this time, when the elevator car platform is level with the sill at landing  4 , the axis of the upper camera is reading division marker 29.25 meters of code rail section  36  which is mounted upon the door frame of the next higher landing which is landing  5 . The table associated with FIG. 4 shows the division markers that are read by the two cameras at the various floors when the car platform is level with the landing door sills at floors  4 - 7 . This data can be placed in the memory of controller  30  for use in carrying out a number of position related functions. Although the division between the markers is given in 0.25 meters, there does not have to be any correlation between these markers and the actual positions of landings relative to each other.  
         [0037]    [0037]FIG. 5 shows the same landing and code arrangement as explained above with regard to FIG. 4, however, the positioning of the landing relative to each other has now changed because the building in which the elevator is housed has settled somewhat between landings  4  and  5 . The car platform  40  is again shown level with the door sill  41  at landing  4  and still reads 15.00. However, landing  5 , at this time, has sagged slightly and the upper camera now reads 29.75, clearly showing that the distance between the code rail sections located at landings  4  and  5  has been shortened by 0.5 meters. The table associated with FIG. 5 shows the change in camera reading resulting from the building sagging between landings  4  and  5 . The distance between the remaining floors, however, remains unchanged in the present example. The processor memory is updated with this new information.  
         [0038]    [0038]FIG. 6 illustrates how the relative distance between adjacent landings can be calculated using the two camera system described above to provide corrected data to the elevator control system so that it can carry out the various car functions relating to motion control. In the example shown in FIG. 6, the initial position between landings  5  and  6  as illustrated in FIG. 5 can be found by the following relationship: 
           DIS.=P 1 L6−P2L5+D  (2) 
         [0039]    where:  
                                       DIS   is the distance between adjacent landings.       P1L6   is the reading along the axis of camera 19 when the elevator           platform is level with the sill at landing 6.       P2L5   is the position of camera 20 when the elevator platform is level           with the landing sill at landing 5, and       D   is the vertical spacing between cameras which in this example is           2.5 meters.                  
 
         [0040]    Prior to the building settling, the distance between landing as taken form the table in FIG. 4 was: 
           DIS = 38.00−37.25+2.50=3.25 m 
         [0041]    After the building has settled, as described with reference to FIG. 5, the distance between landings  5  and  6 , as taken from the table in FIG. 5 is now: 
           DIS= 38.00−37.50+2.50=3.00 m 
         [0042]    The key to the above is that P1L6 and P2L5 are both determined by reading the same code rail section which in this case, is the code rail section at landing  6 . As noted above, it should now be obvious that the absolute marker readings are unimportant. For example, in the case where the code rail section at landing  6  were encoded from 93.00 m and 95.0 meters, the calculated distance between landings  5  and  6  will remain the same as noted above. 
           P 1L6−P2L5+D=94−93.50+2.50=3.00 m 
         [0043]    Accordingly, motion control of the system will also be unaffected. This information is fed into the controlled processor, and the marker locations at each landing is corrected accordingly.  
         [0044]    As should now be evident, the absolute code rail numbers at the various landings are unimportant providing the numbers are not repeated and the spacing between numerical markers is such that the upper and lower numbers are clearly identified so that the motion control based on the readings is not adversely effected.  
         [0045]    It should be further noted that in some high rise applications express elevators may be employed wherein landings between certain floors are not used or are not contained within the hoistway. In this case, code rail sections can be mounted within the express zone of the hoistway to provide coded data to the processor that provides information telling the processor where the car is in reference to the express zone.  
         [0046]    [0046]FIG. 7 illustrates how the two-camera system may be employed to calculate the gap between two adjacent code rail sections. This is an important parameter because the gap distance between code rail sections must always be less than the spacing D between cameras in the two camera embodiment of the invention. As illustrated, the gap between the adjacent code rail section at landings  5  and  6  can be determined by taking readings of code rail sections  36  and  37  as the elevator car moves first in an upward direction and then as the car returns moving in the opposite direction. As the car moves upward past landing  6 , and the axis of the lower camera leaves the associated code rail section  36 , a reading of the upper camera is taken to provide an indication of the lower gap reading which, in this case, is 38.50. A second reading is now taken as the car moves downwardly through the two landings. The second reading is taken by the upper camera  20  as the axis of the lower camera  19  leaves the code rail section  37  which, in this case is 39.25. Subtracting the first reading from the second reading provides the gap distance between rail sections  36  and  37  which in this case, is 0.75m. The gap distances can be continually monitored and, in the event a gap distance that approaches the spacing (D) between cameras and an alert is provided by the processor so that corrective action can be taken in a timely manner to insure that the gap distance does not exceed the (D) distance.  
         [0047]    Referring now to FIGS. 8 and 9, there is illustrated a further embodiment of the present invention wherein a single camera mounted upon the elevator car can be used to obtain both primary and secondary position data. In this embodiment, a continuous code rail strip  50  is vertically extended along the length of the hoistway. The strip is mounted close to each of the landings in the vicinity of the landing door frame. A series of code rail sections, such as sections  52  and  53 , are mounted adjacent to and in parallel alignment with the code rail strip with a rail section being located at each landing so that a camera mounted on the elevator car can view indicia on both the code rail strip and a code rail section simultaneously. The code rail strip is used to provide primary position data to the controller and the code rail sections are used to provide secondary position data to the controller. The primary data relates to the position of the car within the hoistway while the secondary data relates to the position of the car in relation to one of the associated landing sites. The code rail sections are numbered so that the contained indicia identifies the floor and the location of the door sill. As the elevator car approaches a landing, the camera reads both code rails and provides both primary and secondary position data simultaneously to the controller.  
         [0048]    [0048]FIG. 9 illustrates the relative positions of the primary and secondary indicia when the car platform is level with the door sill at landing  8 . At this time the secondary reading is 800 and the primary position is 4257 cm. FIG. 8 illustrates the reading taken by the camera after the building has settled. At this time, the primary reading has changed to 4240cm. As can be seen, using a single camera to view both the code rail strip and the code rail sections, a stream of data can be continually provided to the controller as the elevator car moves along the hoistway which can be used to determine the absolute position of the car within the hoistway as well as providing correction data to the controller in the event the building sags between floors.  
         [0049]    Referring now to FIG. 10, there is illustrated a further embodiment of the invention wherein individual code rail sections  70  and  71  are vertically mounted at intervals along the hoistway. Each code rail section contains position related data thereon in the form of clear apertures  72 . Preferably, each individual section is mounted adjacent the car&#39;s path of travel upon or near the door frame at each landing or any other convenient place within the landing zone. In case there exists an express region within the hoistway, that has no landings, the sections are positioned at given intervals along the express region and again contain data relating to the cars position as it moves through the express region.  
         [0050]    In this embodiment, a pair of read heads  73  and  74  are mounted upon the car at a vertical separation distance (D) that is greater than the gap (d) between each adjacent code rail section. Each read head contains a light tight slot  75  with the slots being vertically aligned so that the code rail sections can be drawn through each read head as the car moves through the hoistway. Although not shown, an array of light emitting diodes are mounted along one side of the slot in each read head and an array of light detectors are mounted along the opposite side of the slot to sense the light emitted by the diodes. As a code rail is drawn through the housing, the light from the diode array is chopped by the strip in a coded fashion to provide non-repeatable positioning data to the detectors which, in turn, supply this data to the car controller via data lines  78 . Read heads of the type herein described are commercially available from R. Stahl Foerdertecnik, Gmbh of Künzelsau, Germany.  
         [0051]    As should now be evident, this embodiment of the invention again employs two discrete sensors to provide continuous absolute positioning data to the car controller.  
         [0052]    While the present invention has been particularly shown and described with reference to the preferred mode as illustrated in the drawing, it will be understood by one skilled in the art that various changes in detail may be effected therein without departing from the spirit and scope of the invention as defined by the claims.