METHOD AND ARRANGEMENT FOR DETERMINING A CURRENT PRECISE POSITION OF AN ELEVATOR CAR IN AN ELEVATOR HOISTWAY

Abstract

A method and position determining arrangement determine a current precise position of an elevator car driven by a drive engine along a hoistway. An encoder cooperating with the drive engine provides a first signal indicating with a high precision the position of the car within a partial hoistway range extending along a fraction of the entire car travel path. A rough position indicator provides a second signal indicating with a low precision the position of the car within the hoistway. A current rough position of the car is determined based on the second signal and deviating from an exact real position of the car up to an first inaccuracy length; and the current precise position of the car is based on the first signal taking into account the current rough position and deviating from the exact real position up to a second inaccuracy length smaller than the first inaccuracy length.

Claims

1-14. (canceled)

15. A method for determining a current precise position of an elevator car driven by a drive engine along an elevator hoistway of an elevator arrangement, the method comprising the steps of: generating a first signal using an encoder cooperating with the drive engine, wherein the first signal indicates with a first precision a position of the elevator car within a partial hoistway range, the partial hoistway range extending along a fraction of an entire length of a travel path of the elevator car throughout the hoistway and the partial hoistway range being one of a plurality of directly neighboring partial hoistway ranges together extending along the entire length of the travel path; generating a second signal using a rough position indicator, the second signal indicating with a second precision the position of the elevator car within the entire hoistway length, the second precision being lower than the first precision; determining a current rough position of the elevator car within the entire hoistway length based on the second signal, the current rough position deviating from an exact real position of the elevator car by up to a first inaccuracy length; determining the current precise position of the elevator car within the entire hoistway length based on the first signal and taking into account the current rough position, the current precise position deviating from the exact real position of the elevator car by up to a second inaccuracy length being smaller than the first inaccuracy length; determining, based on the second signal, as the current rough position in which one or neighboring two of the plurality of partial hoistway ranges the elevator car is currently situated and subsequently, based on the first signal, determining as the current precise position where in the selected one or neighboring two partial hoistway ranges the elevator car is currently situated; wherein the drive engine drives the elevator car along the hoistway by rotating a drive disk engaging with a belt connected to the elevator car; and wherein the partial hoistway ranges each correspond to a distance travelled by the elevator car during one revolution of the drive engine and the encoder generates the first signal correlating to a current rotational orientation of the drive disk.

16. The method according to claim 15 wherein the partial hoistway ranges are longer than the first inaccuracy length.

17. The method according to claim 15 including executing a learning procedure prior to a normal operation of the elevator arrangement, wherein during the learning procedure, a learned correlation relation between a current exact real position of the elevator car and the first signal is learned at each of multiple positions along the entire travel path of the elevator car, and wherein the method further comprises determining the current precise position of the elevator car within the entire hoistway length taking into account the learned correlation relation.

18. The method according to claim 15 wherein the drive disk is a toothed drive disk and the belt is a toothed belt.

19. The method according to claim 15 wherein the rough position indicator generates the second signal by measuring a distance between a fixed position in the elevator hoistway and the elevator car using a contactless measuring technique.

20. The method according to claim 15 wherein the rough position indicator generates the second signal by measuring a run-time required by an electromagnetic signal for travelling along a distance between a fixed position in the elevator hoistway and the elevator car.

21. The method according to claim 20 wherein the electromagnetic signal is an ultra-wide-band signal.

22. The method according to claim 15 wherein the rough position indicator generates the second signal by measuring a local air pressure in the hoistway at a current position of the elevator car.

23. The method according to claim 15 wherein the rough position indicator generates the second signal by detecting RFID tags arranged at various positions along the travel path of the elevator car.

24. A position determining arrangement for determining a current precise position of an elevator car driven by a drive engine along an elevator hoistway of an elevator arrangement, the position determining arrangement comprising: an encoder cooperating with the drive engine to generate a first signal indicating with a first precision a position of the elevator car within a partial hoistway range, the partial hoistway range extending along a fraction of an entire length of a travel path of the elevator car throughout the hoistway and the partial hoistway range being one of a plurality of directly neighboring partial hoistway ranges together extending along the entire length of the travel path; and a rough position indicator generating a second signal indicating with a second precision the position of the elevator car within the entire hoistway length, the second precision being lower than the first precision; and wherein the position determining arrangement is adapted to perform the method according to claim 15.

25. An elevator arrangement comprising: an elevator car movable in a hoistway; a drive engine driving the elevator car along the elevator hoistway; and a position determining arrangement according to claim 24 for determining the current precise position of the elevator car within the elevator hoistway.

26. The elevator arrangement according to claim 25 wherein the drive engine drives the elevator car by rotating a toothed drive disk engaging with a toothed belt connected to the elevator car and wherein the encoder of the position determining arrangement generates the first signal correlating to a current rotational orientation of the drive disk.

27. The elevator arrangement according to claim 25 including two of the drive engine driving the elevator car and wherein the position determining arrangement includes two of the encoder, each of the encoders cooperating with an associated one of the drive engines to generate respective ones of the first signal based on a current rotational orientation of the associated drive engine.

28. The elevator arrangement according to claim 27 including an elevator controller controlling operation of the drive engines, the elevator controller receiving the first signals for determining the current precise position of the elevator car.

Description

DESCRIPTION OF THE DRAWINGS

[0072] FIG. 1 shows an elevator arrangement comprising a position determining arrangement according to an embodiment of the present invention.

[0073] FIG. 2 shows a drive engine of an elevator arrangement according to an embodiment of the present invention.

[0074] FIG. 3 shows signals of an encoder of a drive engine of an elevator arrangement according to an embodiment of the present invention.

[0075] FIG. 4 shows a determination of the current precise position of an elevator car with a method according to an embodiment of the present invention.

[0076] The figures are only schematic and not to scale. Same reference signs refer to same or similar features.

DETAILED DESCRIPTION

[0077] FIG. 1 shows an elevator arrangement 1. The elevator arrangement 1 comprises an elevator car 3 which may be displaced within an elevator hoistway 5 along a travel path 7. The elevator arrangement 1 further comprises two counterweights 9 travelling along travel paths arranged at opposite sides of the elevator car 3. Weights of the elevator car 3 and the counterweights 9 are suspended by suspension means 11 such as belts or ropes which are held at an upper end of the elevator hoistway 5 by pulleys 13.

[0078] The elevator car 3 and the counterweights 9 are displaced along the respective travel paths 7 using two drive engines 15. The drive engines 15 are arranged at a lower end of the hoistway 5. Each drive engine 15 comprises a toothed drive disk 17 driven into rotation by an electric motor. The toothed disc 17 engages with a toothed belt 19. One end of the toothed belt 19 is fixed to a lower end of one of the counterweights 9 whereas an opposite end of the toothed belt 19 is fixed to one side of a lower end of the elevator car 3.

[0079] An operation of both drive engines 15 is controlled by a controller 21. Particularly, the controller 21 communicates via a communication line 29 with an encoder 23 provided at each one of the drive engines 15.

[0080] As shown in FIG. 2, the toothed drive disk 17 of the drive engine 15 is coupled to a shaft 25 of a rotor of the drive engine's 15 electric motor 27. The electric motor 27 is controlled using, inter-alia, first signals provided by the encoder 23, these first signals indicating a current orientation of the rotor of the electric motor 27.

[0081] The encoder 23 may be a one revolution absolute encoder which may be provided in a very cost-effective manner. Therein, within one revolution, it is always possible to determine a current orientation of the rotor of the electric motor 27. Particularly, such orientation determination may be possible without having to rotate the rotor and the drive disk 17 attached thereto. The encoder 23 practically delivers a first signal 39 (FIG. 3) on the communication line 29 that may be proportional for example in degrees to the rotation status of the drive engine 15, i.e. to the current orientation of the rotor of the electric motor 27.

[0082] FIG. 3 exemplarily shows a first signal 39 provided by the encoder 23 as a dependence of a signal strength S of the rotations R of the rotor of the electric motor 27. Upon a full rotation “1” of the rotor, the first signal 39 linearly increases from an initial value until the rotation reaches a 360° orientation. Upon further rotating the rotor, the first signal 39 restarts from its initial value. In other words, the first signal 39 provided by the encoder 23 repeats every 360°. Accordingly, upon continuously rotating the rotor over several rotations, the first signal 39 shows a saw-tooth pattern. Therein, within each single linear increase of the first signal 39, there is an unambiguous correlation between the first signal 39 and the current orientation of the rotor of the electric motor 27.

[0083] As the toothed drive disk 17 is driven by the electric motor 27 and engages without slippage with the toothed belt 19, ends of which are attached to the elevator car 3 and one of the counterweights 9, respectively, the rotation of the rotor of the electric motor 27 directly correlates with the current position of the elevator car 3.

[0084] In other words, there is a timing belt connection between each one of the drive engines 15 and the elevator car 3 that ensures that, beyond a possible load induced elongation of the toothed belt 19, the current position of the elevator car 3 may generally be determined precisely based on the first signal 39 provided by the encoder 23 indicating a current rotational status (=orientation) of the toothed drive disk 17 that drives the toothed belt 19.

[0085] However, as the first signal 39 of the encoder 23 only indicates the current rotational status of the electric motor 27, but not the number of full rotations executed by the electric motor 27, this first signal 39 alone may not be used to unambiguously determine the current precise position of the elevator car 3 along its entire travel path 7. Instead, based on this first signal 39, the position of the elevator car 3 may only be indicated within a partial hoistway range 53 (see FIG. 4) representing a fraction of the entire length of the travel path 7. Assuming for example a diameter of the drive disk 17 of 70 mm, one complete rotation of the rotor of the electric motor 27 corresponds to a shift of the actual position of the elevator car 3 of about 220 mm (70 mm*Pi), because the traction has a reeving factor of 1:1. Accordingly, in this example, based on the first signal 39 of the encoder 23 alone, the current position of the elevator car 3 may only be determined within a partial hoistway range 53 having a length of less than 220 mm.

[0086] In principle, it may be possible to determine the current precise position of the elevator car 3 throughout the entire length of the travel path 7 by additionally counting the full rotations performed by the drive engine 15 for example since determining an initial reference position of the elevator car 3. In such case, the number of rotations would have to be continuously tracked during the operation of the elevator arrangement 1.

[0087] However, there may be a risk that the information received by counting the rotations may be lost, for example as a result of a power loss in the elevator arrangement 1. In such case, upon for example the power supply being resumed, it would not be possible to determine the current position of the elevator car 3 along its travel path 7 only based on the first signal 39 provided by the encoder 23.

[0088] In order to overcome such problem, it is therefore suggested herein to determine the current precise position of the elevator car 3 with a two-step approach. Therein, a position determining arrangement 55 comprises the encoder 23 and a rough position indicator 37.

[0089] First, a current rough position of the elevator car 3 within the entire length of the hoistway 5 is determined based on a second signal provided by the rough position indicator 37. This rough position indicator 37 may indicate the position of the elevator car 3 within the entire hoistway length but suffers from a relatively low precision. For example, the rough position indicator 37 may provide position information only with a first inaccuracy length, i.e. with measurement values including a substantial error band.

[0090] Only after the current rough position of the elevator car 3 has been determined based on the second signals from the rough position indicator 37, the current precise position of the elevator car 3 is determined based on the first signal 39 provided by the encoder 23 and taking into account the previously determined current rough position.

[0091] In other words, the information provided by the encoder 23 indicating a precise position within one of a multiplicity of partial hoistway ranges 53 is supplemented using an absolute positioning system including the rough position indicator 37 that gives the absolute position of the elevator car 3 in the elevator hoistway 5 with a rough accuracy.

[0092] The rough position indicator 37 may preferably be implemented using components provided in the elevator arrangement 1 originally for other purposes.

[0093] For example, the elevator arrangement 1 may comprise a first transceiver 31 communicating with the controller 21 and being arranged at a stationary reference position within the elevator hoistway 5. Furthermore, the elevator arrangement 1 may comprise a second transceiver 33 communicating with components such as a car operation panel (COP) in the elevator car 3 and being attached to the elevator car 3. The first and second transceivers 31, 33 may establish a data communication path 35 via which the controller 21 may communicate with components in the elevator car 3.

[0094] For determining the current rough position of the elevator car 3, the first and second transceivers 31, 33 may be used for determining a current distance of the elevator car 3 carrying the second transceiver 33 from the stationary location of the first transceiver 31. For that purpose, one of the transceivers 31, 33 may emit an electromagnetic signal and a run-time required by this electromagnetic signal for travelling along the distance between the first transceiver 31 and the second transceiver 33 may be measured in a TOF measurement. The electromagnetic signal may be for example an ultra-wide-band signal.

[0095] As an alternative, the current rough position of the elevator car 3 may be determined by measuring a local air pressure at the current position of the elevator car 3 using an air pressure sensor 45.

[0096] As a further alternative, the current rough position of the elevator car 3 may be determined by detecting RFID tags 43 arranged at various positions along the travel path 7 of the elevator car 3 using an RFID reader 41 attached to the elevator car 3.

[0097] Before the position determining method described herein is applied during normal operation of an elevator arrangement 1, a learning procedure may be executed. In this learning procedure, a correlation relation between exact real positions of the elevator car 3 and the first signals 39 provided by the encoder 23 when the elevator car 3 is at a respective position may be learned for each of multiple positions along the entire travel path 7.

[0098] In other words, in the learning procedure, first data provided by the encoder 23, i.e. the first signals 39, second data provided by an absolute position determination device for example temporarily installed in the elevator arrangement during the learning trip and, optionally, third data provided by the rough position indicator 37 are acquired and set into a correlation in order to form a database referred to herein as correlation relation.

[0099] FIG. 4 shows a graph of the first signal S.sub.1 39 generated by the encoder 23 and the second signal S.sub.2 47 generated by the rough position indicator 37 in dependence of the current exact real position P of the elevator car 3. Therein, the second signals 47 are acquired with a predetermined first inaccuracy length 51, thereby defining error bands 49 extending above and below the second signal 47.

[0100] In normal operation of the elevator arrangement 1, i.e. preferably after the correlation data has been learned in the learning procedure, the current precise position of the elevator car 3 may then be determined as follows: [0101] the current rough position is determined based on the second signals 47 from the rough position indicator 37 (reference point “A”). Particularly, it is determined in which one or neighboring two of the partial hoistway ranges 53 spanning the entire length of the travel path 7 the elevator car 3 is currently situated. [0102] Then, based on the first signal 39 from the encoder 23, the orientation status of the drive disk 17 is determined (reference point “B”). [0103] Upon optionally additionally taking into account the correlation relation learned during the learning procedure, the current precise position of the elevator car 3 may be determined for example by finding the correct car position “C” from the graph that matches the partial hoistway a range 53 indicated by the rough position indicator 37 as well as the rotation orientation indicated by the encoder 23.

[0104] The method proposed herein allows precisely determining the current position of the elevator car 3 as long as the first inaccuracy length 51 describing the precision of determination of the current rough position is shorter than the partial hoistway ranges 53 in which the current precise position of the elevator car 3 may be determined based on the first signals 39 from the encoder 23. In other words, the proposed process works as long as the inaccuracy of the rough position indicator 37 is well below 50% of the distance travelled by the elevator car 3 within one rotation of the drive disk 17 of the drive engine 15. If this condition does not apply, it may not be possible to determine the precise positions of the elevator car 3 because the same imprecise position may map to two different precisely determined orientations of the drive disk 17.

[0105] Finally, it should be noted that the term “comprising” does not exclude other elements or steps and the “a” or “an” does not exclude a plurality. Also, elements described in association with different embodiments may be combined.

[0106] In accordance with the provisions of the patent statutes, the present invention has been described in what is considered to represent its preferred embodiment. However, it should be noted that the invention can be practiced otherwise than as specifically illustrated and described without departing from its spirit or scope.