WO2004106210A1

WO2004106210A1 - Absolute position reference system for an elevator using magnetic sensors

Info

Publication number: WO2004106210A1
Application number: PCT/US2003/015245
Authority: WO
Inventors: Vlad Zaharia; Gary L. Nuschler
Original assignee: Otis Elevator Compagny
Priority date: 2003-05-15
Filing date: 2003-05-15
Publication date: 2004-12-09
Also published as: AU2003243237A1

Abstract

An absolute position reference apparatus for an elevator car (10) uses a magnetic strip (40) which has at least an absolute position track (22) by which position of the car can be determined and an incremental position track (24) by which speed can be determined.

Description

ABSOLUTE POSITION REFERENCE SYSTEM FOR AN ELEVATOR USING MAGNETIC SENSORS

BACKGROUND OF THE INVENTION The present invention relates generally to an elevator, and more specifically to an apparatus and a method for determining the position of an elevator car as the car moves along a hoistway. 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 opening the car doors. To carry out these functions accurately, it is necessary to know the car's exact position at all times. 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. 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 unit 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 l 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. 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, are difficult to adjust, and costly to maintain. Error correction is necessary at each landing in order to compensate for rope slippage and the like. The car'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 reference 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 It is therefore an object of the present invention to improve elevators, and in particular to improve positioning systems used to control elevators . 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. The foregoing objects are achieved by the apparatus and method of the present invention. In accordance with the present invention, an absolute position reference system for an elevator broadly comprises an elevator car mounted for reciprocal movement along a vertical path of travel within a hoistway between a series of landings. At least one magnetic strip is secured to a static structure. The at least one magnetic strip has at least one of an absolute position track formed by a plurality of magnets arranged in different encoded patterns and an incremental position track formed by a plurality of magnets arranged in a regular pattern. At least one sensor is used for detecting the position of the car via the absolute track. The speed of the car can be detected directly via the incremental position track or can be calculated from consecutive measurements of absolute position. Further, in accordance with the present invention, a method for providing absolute position information for an elevator broadly comprises the steps of securing at least one magnetic strip having at least one of an absolute position track formed by a plurality of magnets arranged in different encoded patterns and incremental position track formed by a plurality of magnets arranged in a regular pattern to a static structure, mounting at least one sensor to an elevator car mounted for reciprocal movement along a vertical path of travel within a hoistway between a series of landings, detecting the position of the car using the at least one sensor to measure a magnetic field produced by the absolute position track, and detecting the speed of the elevator car using the at least one sensor to measure a magnetic field produced by the incremental position track. Other details of the absolute position reference system for an elevator using magnetic sensors, as well as objects and advantages attendant thereto, are set forth in the following detailed description and the accompanying drawings wherein like reference numerals depict like elements.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 illustrates one embodiment of an absolute position reference system in accordance with the present invention; FIG. 2 illustrates an alternative embodiment of an absolute position reference system in accordance with the present invention; FIG. 3 illustrates another embodiment of an absolute position reference system in accordance with the present invention; and FIG. 4 illustrates still another embodiment of an absolute position reference system in accordance with the present invention.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT (S) Referring now to FIG. 1, there is shown an elevator car 10 that is suspended by ropes (not shown) suspended between a pair of guide rails (not shown) . As is well known in the art, the car 10 is arranged to move reciprocally over a vertical path of travel within a hoistway 12 that is housed within a structure having several floors. A controller 14 which contains a processor (not shown) that is programmed to carry out a number of car related control functions and a memory (not shown) for storing position related data may be located in a machine room. To perform these and other control functions accurately, it is necessary that the processor in the controller 14 receives accurate and sufficient information to enable it to determine the car's exact location at all times within the hoistway 12. In one embodiment of the present invention, at least one magnetic strip 20 is provided. Each strip 20 has an absolute position track 22. It may also have an incremental position track 24. The length of the strip 20 depends on whether one strip 20 will extend the entire length of the hoistway 12 or whether multiple, spaced apart strips 20 will be installed in the hoistway 12. The absolute position track 22 comprises a plurality of magnets 26 of different sizes arranged in a single, unique, non- repeatable pattern. In other words, the track 22 is magnetized in a series of non-repeatable, encoded patterns made up of a plurality of the magnets 26. As can be seen from FIG. 1, there may be a first pattern I in which there are alternating small and large magnets 28 and 30, a second pattern II having two larger magnets 32 and three smaller magnets 34 between the two larger magnets 32, and a third pattern III having two magnets 36 of the same size. Due to their differences, each pattern generate a unique magnetic field having a unique strength. The incremental position sensor track 24 comprises a plurality of equally spaced apart magnets 38. The magnets 38 each have the same size and the same field strength. The track 24 preferably is magnetized in a regular pattern. A suitable magnetic strip 20, having an absolute position track 22 and an incremental position sensor track 24, which can be used in the apparatus of the present invention is produced by Siko GmbH. In a preferred embodiment, a plurality of spaced apart strips 20 are placed along the hoistway 12. They may be mounted to any suitable stationary structure such as the guide rails, brackets secured to the guide rails, or the door frame at each floor. At least one magnetic sensor 40 is secured to the elevator car 10 and its output is supplied to the controller 14. The sensor (s) 40 may be secured in any desired location such as at the bottom and/or the top of the car 10. When two sensors 40 are used, the spacing between adjacent ones of the strips 20 must be less than the spacing between the sensors 40. Each sensor 40 may comprise any suitable array of magnetoresistive and/or Hall effect sensors known in the art, such as a magnetoresistive sensor manufactured by Siko GmbH, for detecting and measuring the strength of the magnetic fields generated by the magnets forming the patterns in the absolute position track 22 and the magnets forming the incremental position sensor track 24. In operation, each sensor 40 detects the unique magnetic field signature of a particular pattern of the absolute position track 22. In this way, the controller 14 knows the position of the car 10 within the hoistway 12, particularly at the landing zones. The sensor (s) 40 also detect the magnet field generated by the magnets forming the incremental position track 24 and from this can determine the speed of the elevator car 10 - a check which is required in the door zones and at the terminal landings. At terminal landings, the length of the strip 20 may be extended to provide position information for terminal stopping functions, as may be required by various elevator safety codes. Using a plurality of the magnetic strips 20, a continuous absolute positioning system can be created, as long as appropriate spacing is kept between sensors and between strips. Referring now to FIG. 2, in some elevator systems, it is not possible to position a strip 20 with both tracks on a surface of a guide rail 50. In such systems, a strip 20' containing only an absolute position track 22 may be placed on one side 52 of the rail 50 and a strip 20" containing only an incremental position track 24 may be placed on the other side 54 of the rail 50. In such a configuration, an absolute position sensor 40' and an incremental position sensor 40" may preferably be mounted to the car 10. As before, the sensors 40' and 40" may comprise any suitable sensor known in the art . The output of the sensors 40' and 40" are provided to the controller 14. Referring now to FIG. 3, this embodiment shows magnetic strip sections 20 mounted on landing doors via landing door strut 70 and mounting brackets 72. Two sensors 40 are mounted on the car 10. The distance D between the sensors 40 is larger than the gap G between the magnetic strips 20, in such way that at least one sensor 40 'reads' a magnetic strip 20 at any car position in the hoistway. The advantage of this embodiment is that a continuous absolute position system can be created from a number of discrete sections and that the absolute floor positions can automatically be updated in case of building settling, without additional sensors. Referring now to FIG. 4, this embodiment shows a continuous magnetic strip 20 mounted on a guide rail 50 via a mounting bracket 74. Since the strip is continuous, there is no constraint on the distance between the sensors 40 on the car 10, so they are shown mounted close to each other via mounting bracket 76 attached to car 10. When a building settles, the position of the landings can shift on a vertical axis at a rate that is different from that of the guide rails. In order to determine the new absolute positions of the landings, each landing needs to have a reference point rigidly attached to it (can be attached to the door sill, door frame, etc.) . FIG. 4 shows a sill reflector 80 as one of these reference points. The sill reflector 80 may be mounted to a landing door sill 86. A corresponding sill sensor 82 is attached to the car. The sill sensor 82, which can be of photoelectric, inductive or other type, produces a signal every time it passes a reflector 80. Thus, by having the controller 14 read the position from the magnetic strip 20 and the signal from the sill sensor 82 at the same instant, the absolute position of the landing can automatically be updated. The apparatus of the present invention provides several advantages over existing technologies. These include significant installed cost savings, maintenance-free, the elimination of correction runs, automatic floor table adjustment when building settlement is detected, elimination of a third track on a machine speed encoder and the circuitry currently associated with the independent speed check, and the absence of smoke, dust, and water effects. It is apparent that there has been provided in accordance with the present invention an absolute position reference system for an elevator using magnetic sensors which fully satisfies the objects, means, and advantages set forth hereinbefore. While the present invention has been described in the context of specific embodiments thereof, other alternatives, modifications, and variations will become apparent to those skilled in the art having read the foregoing description. Accordingly, it is intended to embrace those alternatives, modifications, and variations as fall within the broad scope of the appended claims.

Claims

WHAT IS CLAIMED IS:

1. An apparatus for determining the position of an elevator car within a hoistway comprising: an elevator car mounted for reciprocal movement along a vertical path of travel within a hoistway between a series of landings; at least one magnetic strip secured to a static structure, said at least one magnetic strip having at least one of an incremental position track formed by a plurality of magnets arranged in a regular pattern and an absolute position track formed by a plurality of magnets arranged in different encoded patterns; and at least one sensor for detecting the position of the car via the absolute position track and for detecting the speed of the car via the incremental position track.

2. An apparatus according to claim 1, wherein said incremental position track is formed by a plurality of equally sized and equally spaced magnets .

3. An apparatus according to claim 1, wherein said absolute position track is formed by a plurality of magnets arranged in a single, unique, non-repeatable pattern.

4. An apparatus according to claim 1, further comprising a plurality of spaced apart magnetic strips arranged within the hoistway, a pair of sensors mounted to said elevator car, and said magnetic strips being spaced apart a distance less than the distance between said sensors so that at least one sensor reads at least one magnetic strip at any position of said car.

5. An apparatus according to claim 4, wherein each said magnetic strip is mounted to a landing door strut via a mounting bracket.

6. An apparatus according to claim 1, wherein said at least one magnetic strip comprises a first magnetic strip having an incremental position track mounted to a first surface of a guide rail and a second magnetic strip having an absolute position track mounted to a second surface of said guide rail and wherein said at least one sensor comprises an incremental position sensor and an absolute position sensor.

7. An apparatus according to claim 1, wherein an output from said at least one sensor is supplied to a controller.

8. An apparatus according to claim 1, further comprising means for updating an absolute position of a landing.

9. An apparatus according to claim 8, wherein said landing updating means comprises a reflector mounted to a landing door sill, a sill sensor for producing a signal when said sill sensor passes said reflector, said sill sensor being mounted to the car, and means for reading a position from said at least one magnetic strip and said signal from said sill sensor.

10. A method for determining the position of an elevator car in a hoistway comprising the steps of:

securing at least one magnetic strip having at least one of an incremental position track formed by a plurality of magnets and an absolute position track formed by a plurality of magnets arranged in different encoded patterns to a static structure;

mounting at least one sensor to an elevator car mounted for reciprocal movement along a vertical path of travel within a hoistway between a series of landings; and

detecting the position of the car using said at least one sensor to measure a magnetic filed produced by the absolute position track.

11. A method according to claim 10, further comprising detecting the speed of the elevator car using said at least one sensor to measure a magnetic field produced by the incremental position track.

12. A method according to claim 10, wherein said mounting step comprises mounting a pair of sensors to said elevator car and wherein said securing step comprising placing a plurality of spaced apart magnetic strips within the hoistway with said magnetic strips being spaced apart a distance less than the distance between said sensors .

13. A method according to claim 10, wherein said securing step comprises securing a first magnetic strip having an incremental position track to a first surface of a guide rail and securing a second magnetic strip having an absolute position track to a second surface of said guide rail and wherein said mounting step comprises mounting an incremental position sensor and an absolute sensor to said elevator car.

14. A method according to claim 10, further comprising supplying an output from said at least one sensor to a controller.

15. A method according to claim 10, further comprising updating an absolute position of a landing.

16. A method according to claim 15, wherein said updating step comprises :

providing a reflector mounted to a landing door sill and a sill sensor mounted to the car for producing a signal when said sill sensor passes said reflector; and

reading at the same instant a position from said at least one magnetic strip and said signal from said sill sensor.