Differential reflectometry for position reference in an elevator system

Abstract: An apparatus for determining if an elevator car is level with respect to a landing in a hoistway comprises a transceiver (26) for transmitting a signal (50), first and second reflectors (28,30), each having a varying reflectance along their lengths between a maximum reflectance end and a minimum reflectance end, and a processor (32). The reflectors (28,30) reflect first and second signal (52,54) in response to the transmitted signal (50), and are adjacently aligned such that the maximum reflectance end of the first reflector is adjacent to the minimum reflectance end of the second reflector, and the minimum reflectance end of the first reflector is adjacent to the maximum reflectance end of the second reflector. The processor (32) determines if the elevator car (12) is level with respect to the landing in response to a comparison of the first and second reflected signals (52,54).

Description: The present invention relates generally to elevators and, in particular, relates to position reference in an elevator system. To stop an elevator smoothly and level with a sill, an elevator system must know when to initiate a stop, when to go into a levelling mode of operation, and when to begin opening the landing doors. The elevator doors must not be opened when the elevator car is not within the door zone. It is therefore necessary to know the exact location of the elevator car. As a consequence, elevator position devices are used to monitor elevator car position. Such a device is known for example from US-A-3749203. One existing elevator position device includes steel bars, vanes or magnets attached to a floating steel tape running the length of the hoistway, and a hoistway position reader box mounted on the car, which are used to monitor the car position. The steel bars, vanes or magnets are located on the steel tape with respect to their corresponding landing sills to mark the approximate distance from the door zone. The reader box contains sensors that sense the location of each steel bar, vane or magnet as the car travels up and down the hoistway such that the elevator system may determine if the elevator car is level with respect to a particular landing in the hoistway. Other techniques for determining if an elevator car is level with respect to the landing are sought, and it is to this end that the present invention is directed. It is an object of the present invention to provide improved detection of a landing in an elevator hoistway. According to the present invention, an elevator car position reference device comprises an emitter means for transmitting one or more detection signals; first and second reflectors having varying reflectances along their lengths and generating first and second reflected signals respectively in response to the one or more detection signals transmitted by the emitter means; and a processor for comparing the first and second reflected signals to determine the position of the elevator car. In a preferred embodiment, an apparatus for determining if an elevator car is level with respect to a landing in a hoistway comprises a transceiver for transmitting a signal, a first reflector having a varying reflectance between a maximum reflectance end and a minimum reflectance end, a second reflector having a varying reflectance between a maximum reflectance end and a minimum reflectance end, and a processor. The first reflector transmits a first reflected signal in response to the signal transmitted by the transceiver and the second reflector transmits a second reflected signal in response to the signal transmitted by the transceiver. The first reflector and the second reflector are adjacently aligned such that the maximum reflectance end of the first reflector is adjacent to the minimum reflectance end of the second reflector, and the minimum reflectance end of the first reflector is adjacent to the maximum reflectance end of the second reflector. The processor determines if the elevator car is level with respect to the landing in response to the first and second reflected signals. An embodiment of the present invention will now be described, by way of example only, with reference to the drawings, in which: Fig. 1 is a perspective view of an elevator system in a building; Fig. 2 is a simplified block diagram illustrating an apparatus in accordance with one embodiment of the present invention; Fig. 3 is a front view of a first reflector and a second reflector; Fig. 4 is a side view of an elevator car in a hoistway incorporating a preferred embodiment of the present invention; and Fig. 5 is a graphical illustration of a difference of two reflected signals versus position in accordance with an embodiment of the present invention. Referring to Fig. 1, an elevator system 10 in a building is shown. An elevator car 12 is disposed in a hoistway 14 such that the elevator car 12 travels in a longitudinal direction along elevator guide rails 16 disposed in the hoistway 14. An elevator controller 18 is disposed in a machine room 20 and monitors and provides system control of the elevator system 10. A travelling cable 22 is used to provide an electrical connection between the elevator controller 18 and electrical equipment in the hoistway 14. Of course, it should be realized that the present invention can be used in conjunction with other elevator systems including hydraulic and linear motor systems, among others. Referring to Fig. 2, an elevator position apparatus 24 according to the present invention is used in conjunction with the elevator system 10 to accurately determine the position of the elevator car 12 in the hoistway 14. The elevator position apparatus 24 includes a transceiver 26, a first reflector 28, a second reflector 30, and a processor 32 for determining if the elevator car is level with respect to a landing 46 (shown in Fig. 4). The transceiver 26 is a device which transmits and receives an energy signal such that the intensity of the received signal may be measured. For example, the transceiver 26 comprises an emitter and a sensor. The emitter may be any radiation emitting device; for example, an infrared emitter that is modulated so that its radiated energy is distinguishable from background radiation of the surroundings. In one embodiment, the emitter is a conventional LED. The sensor is any device that is sensitive to the radiation of the emitter; yet preferably adapted to be insensitive to radiation other than that from the emitter. For example, the detector may be a photodiode or phototransistor which is designed to pass signals at the emitter modulation frequency and wavelength. In an alternative embodiment, the sensor comprises a bandpass filter so that the transceiver is insensitive to radiation other than radiation emitted from the transceiver. The transceiver 26 transmits at least one signal and detects at least two signals. Accordingly, the transceiver 26 comprises at least one emitter and either one sensor with the capability of receiving two signals or two discrete sensors. In one embodiment, the transceiver transmits two signals and receives two signals. The term "transceiver" is intended to include a unitary device or a transceiver consisting of a combination of discrete transmitting and receiving elements. In one embodiment, the transceiver 26 is disposed on the elevator car 12. Referring to Figs. 2 and 3, the first reflector 28 has a maximum reflectance end 34, a minimum reflectance end 33 and a varying reflectance 36 between the two ends. Likewise, the second reflector 30 has a maximum reflectance end 40, a minimum reflectance end 38 and a varying reflectance 42 between the two ends. In one embodiment, each varying reflectance 36, 42 varies linearly between the maximum and minimum reflectance ends. The first reflector 28 and the second reflector 30 are adjacently aligned such that the maximum reflectance end 34 of the first reflector 28 is adjacent to the minimum reflectance end 38 of the second reflector 30. The minimum reflectance end 33 of the first reflector 28 is adjacent to the maximum reflectance end 40 of the second reflector 30. In one embodiment, the first and second reflectors 28,30 are disposed on a hoistway wall 44 proximate to the landing 46 (shown in Fig. 4). The reflectors 28, 30 are aligned such that the reflectance varies in the direction of elevator travel. Moreover, the reflectors 28, 30 and the transceiver 26 are aligned such that the transceiver 26 detects the reflected signal from the reflectors 28, 30. However, the reflectors do not need to be precisely placed with respect to the landing in the direction of elevator travel because a compensation routine may be utilized by the processor 32 as is explained herein below. Referring to Fig. 2, the processor 32 is used for determining if the elevator car 12 is level with respect to the landing 46. In one embodiment, the processor comprises a memory 48 for storing data and software. The software is embedded in the memory using methods known to those skilled in the art and is used to determine if the elevator car 12 is level with respect to the landing 46 as is explained below. In an alternative embodiment, the processor 32 comprises hardware for determining if the elevator car 12 is level with respect to the landing 46. The processor 32, for example, may be implemented in the elevator controller 18. The implementation of either the software or the hardware of the processor 32 should be known to those of ordinary skill in the art in the light of the present specification. Referring to Figs. 2, 4 and 5, an illustrated embodiment of the present invention operates as follows. As the elevator car 12 travels in the hoistway 14 and approaches the landing 46, the processor 32 causes the transceiver 26 to transmit a detection signal 50. In one embodiment, the transceiver 26 transmits the detection signal 50 continuously and in another embodiment the transceiver 26 transmits the detection signal 50 only as the elevator car 12 is in the door zone. In the latter embodiment, an approximate position transducer such as, but not limited to, a governor shaft encoder or a motor shaft encoder may be used to provide an approximate position signal to the processor. These types of transducers are well known to one of ordinary skill in the art. The processor uses the approximate position signal to determine if the elevator car is near the landing, i.e. in the door zone. As the elevator car 12 is approximately level with the landing 46, the detection signal 50 transmitted by the transceiver 26 is reflected by the first and the second reflectors 28, 30 such that a first and a second reflected signal 52, 54 are received by the transceiver 26. The transceiver 26 in turn transmits a first level signal 56 to the processor 32 in response to the first reflected signal 52 and a second level signal 58 to the processor 32 in response to the second reflected signal 54. The values of the first and second level signals 56, 58 vary according to the intensities of the first and second reflected signals 52, 54. The intensities of the first and second reflected signals 52, 54 vary according to the variable reflectances 36, 42 of the reflectors 28, 30 and, thus, according to the position of the transceiver 26 with respect to the first and second reflectors 28,30. For example, a reflected signal from the maximum reflectance end has a higher intensity than a reflected signal from the minimum reflectance end. Moreover, if the minimum reflective end 33 of the first reflector 28 and the maximum reflective end 40 of the second reflector 30 are positioned proximate to the elevator car 12 then the first reflected signal 52 will vary from low intensity to high intensity and the second reflected signal 54 will vary from high intensity to low intensity as the elevator car 12 approaches the landing 46. The processor 32 compares both reflected signals 52, 54 to determine the intensity of each signal. The processor 32 determines, in one embodiment, that the elevator car 12 is level with the landing 46 if both of the reflected signals 52, 54 are of equal intensity. For example, the processor 32 determines that the elevator car 12 is level with the landing 46 if the intensity of the first reflected signal 52 minus the intensity of the second reflective signal 54 equals zero, as shown in Fig. 5. In another embodiment, a compensation table is stored in the memory 48 and used by the processor 32. The compensation table allows for various placements of the reflectors 28, 30. A value of the difference of the first and second level signals as the elevator car is level with respect to each landing in the hoistway is stored in the compensation table. Once the table is completed during a calibration run, it may be used as a look-up table to provide compensation during normal elevator operation. During normal operation, the value which corresponds to the landing is used to level the elevator car with respect to that particular landing. For example, the processor 32 determines that the elevator car 12 is level with a first landing if the intensity of the first reflected signal 52 minus the intensity of the second reflective signal 54 equals a value stored in the compensation table for the first landing. Various changes to the above description may be made without departing from the scope of the present invention, which is defined by the claims.

Claims: An elevator car position reference device comprising: an emitter means (26) for transmitting one or more detection signals (50); a first reflector (28) having a varying reflectance (36) along its length, said first reflector (28) generating a first reflected signal (52) in response to the one or more detection signals (50) transmitted by said emitter means (26); a second reflector (30) having a varying reflectance (42) along its length, said second reflector (30) generating a second reflected signal (54) in response to one of the one or more detection signals (50) transmitted by said emitter means (26); and a processor (32) for comparing the first and second reflected signals (52,54) to determine the position of the elevator car (12). The device according to Claim 1, wherein said first reflector (28) has a location with maximum reflectance (34), wherein said second reflector (30) has a location with minimum reflectance (38), and wherein the maximum reflectance (34) of said first reflector (28) and the minimum reflectance (38) of said second reflector (30) are aligned. The device according to Claim 1 or 2, further comprising a transceiver (26) including said emitter means and a sensor means, wherein said sensor means receives at least one of the reflected signals (52,54). The device according to Claim 1, 2 or 3, wherein the reflectance of said first and second reflectors (28,30) varies linearly. The device according to any preceding claim, wherein the device determines the position of an elevator car (12) relative to a landing (46) in a hoistway (14), and wherein said emitter means (26) is disposed on said elevator car (12) and said first and second reflectors are disposed in the hoistway (14) and proximate to the landing (46). The device according to Claim 5, wherein the device determines that the elevator car (12) is level with respect to the landing (46) if the first and second reflected signals (52,54) have equal values. The device according to Claim 5, wherein the device determines that the elevator car (12) is level with respect to the landing (46) if the difference between the first and second reflected signals (52,54) is equal to a predetermined value. A method to determine the position of an elevator car (12), the car (12) being disposed for movement in a hoistway (14), the car (12) including an emitter means (26) for transmitting detection signals (50) and a sensor means (26) for receiving reflected signals (52,54), and the hoistway (14) including first and second reflectors (28,30) having varying reflectance along their lengths, each of the reflectors (28,30) generating a reflected signal (52,54) in response to the detection signals (50), the method including the steps of: emitting one or more detection signals (50) from the emitter means (26); reflecting one of the detection signals (52) from the first reflector (28); reflecting one of the detection signals (54) from the second reflector (30); receiving the reflected signals (52,54) at the sensor means (26); and comparing the reflected signals (52,54) to determine the position of the elevator car (12). The method according to Claim 8, wherein the hoistway (14) includes a landing (46), wherein the first and second reflectors (52,54) are disposed proximate to the landing (46), and wherein the step of comparing the reflected signals (52,54) includes determining the difference between the reflected signals (52,54) and comparing the difference to a predetermined value associated with the position of the landing (46). A method of determining the position of an elevator car in a hoistway comprising the steps of providing in the hoistway a pair of reflectors having varying reflectances along their lengths, reflecting signals off of the reflectors from transmitter and receiver means on the elevator car, and comparing the intensities of the reflected signals.

Inventors: DURAND CHRISTOPHE, DURAND, CHRISTOPHE
Applicants: OTIS ELEVATOR CO, OTIS ELEVATOR COMPANY
Application year: 1997
Main classification: B66B1
IPC codes: B66B1, B66B13