WO2011147456A1

WO2011147456A1 - Elevator and elevator rope monitoring device

Info

Publication number: WO2011147456A1
Application number: PCT/EP2010/057366
Authority: WO
Inventors: Tuomo Hakala; Sami Saarela; Jaakko KALLIOMÄKI
Original assignee: Kone Corporation
Priority date: 2010-05-27
Filing date: 2010-05-27
Publication date: 2011-12-01
Also published as: HK1181370A1; CN102906001A; CN102906001B

Abstract

The invention relates to an elevator rope monitoring device (21) for monitoring the rope tension of at least one rope in a set of elevator ropes, the monitoring device comprising a rope tension sensor (18a-18e) and a control means (22), whereby the output signal of the rope tension sensor is fed to the control means, which control means comprises an processing unit (30) which is adapted to initiate a predetermined action if the output signal of the rope tension sensor or a signal derived therefrom reaches a preset relationship with respect to at least one predetermined reference value, characterized in that the control means comprises a oscillation detection means comprising - a frequency monitoring means (24) for determining at least one oscillation frequency of the output signal of the rope tension sensor, and - an amplitude determining means (26, 28) determining the amplitude of the at least one oscillation frequency determined by the frequency monitoring means, whereby the processing unit initiates the predetermined action if the oscillation frequency and/or its amplitude has a preset relationship to corresponding predetermined reference values.. By this invention the status or behaviour of the elevator ropes as well as of other elevator components can be monitored.

Description

Elevator and elevator rope monitoring device

The present invention relates to elevators having an elevator rope monitoring device for monitoring the rope tension of at least one rope in a set of elevator ropes.

On this behalf the rope monitoring device comprises a rope tension sensor and a control means, whereby the output signal of the rope tension sensor is fed to the control means. The rope monitoring device comprises an processing unit which is adapted to generate a trigger signal for initiating maintenance or emergency actions if the output signal of the rope tension sensor exceeds at least one predetermined reference value.

A device of this type as claimed in the present invention is known from US 6,123,176. In this document the rope tension of different ropes are compared with each other and with a predetermined reference value so as to generate a warning signal if this comparison leads to the result that the tension of one rope essentially deviates from the tension of the other ropes or from a reference value. Accordingly, the arrangement and method described in this document is quite well adapted to ensure that the tension of the different elevator ropes correspond to given tension value ranges.

With this known arrangement of US 6,123,176 it is anyway not possible to determine a sway of the elevator ropes and the reasons for the sway in the elevator system.

Accordingly, the object of the invention is to provide an elevator rope monitoring device as well as an elevator having such a device which allows a more detailed information about the rope status or behaviour of the elevator system.

This object is obtained with an elevator rope monitoring device according to claim 1, with an elevator according to claim 9 as well as with a monitoring method according to claim 13. Preferred embodiments of the invention are subject matter of the corresponding sub-claims.

According to the invention an elevator rope monitoring device comprises an oscillation detection unit which is adapted to detect any oscillation frequency of the tension signal obtained from a rope tension sensor as well as the amplitude thereof. On this behalf the oscillation detection unit comprises a frequency monitoring means for determining at least one oscillation frequency of the output signal of the rope tension sensor as well as an amplitude determining means determining the amplitude of the at least one rope oscillation frequency determined by the frequency monitoring means.

It should be clear that the invention analyses the tension signal obtained from the tension measurement via the rope tension sensor to obtain an oscillation frequency and amplitude of the tension signal. To clarify technical terms it is emphasized that the term "sway" means a lateral swinging motion of the elevator rope which can be measured by the rope tension sensor as an oscillating output signal with a corresponding frequency.

The base idea of the invention is that

1. the tension of the ropes is measured from which tension the amplitude and the frequency spectrum are collected, e.g. recorded,

2. the collected data is analysed, preferably by FFT, in real-time mode to identify steady and transient changes in the rope tension,

3. together with known elevator and rope data the frequency and amplitude of these steady and transient tensions are used identify and quantify any events which are imposing an effect to the rope, whereby

4. one of these transient events happening to the rope is (lateral) rope sway, which has an identifiable fingerprint since its frequency varies in a certain range on the elevator status, as e.g. the car position, car load, acceleration, deceleration etc.. Therefore, with above mentioned components it is possible to deduce on the rope sway or on other elevator components which have an effect on the rope tension.

By the inventive determination of the oscillation of the tension signal not only the status or behaviour of the rope, as e.g. rope sway frequency and amplitude, can be monitored but also the operational status or behaviour of other elevator components, e.g. of the elevator motor, of the rail guides guiding the elevator car or the counterweight along the corresponding guide rails, the movement of the elevator car, the speed governor, car doors etc.. All these components produce in operation steady or transient tension effects, e.g. vibrations with a certain frequency, which are transmitted to the elevator ropes and can be measured by the rope tension sensors. Thus, deviations or a sway with a very low frequency can occur when the rail guides of the elevator car are not running smooth along the guide rails. Thus, elevator components may exert either by their position, motion or operation an impact on the rope tension e.g. in form of vibrations or oscillations with lower frequencies. With the invention it is now possible to monitor these vibrations or oscillations and to make deductions on the status or behaviour of elevator components.

The measured oscillation frequency and amplitude of the tension signal may be compared in a comparator of the processing unit with corresponding predetermined reference values, e.g. to check whether the oscillations are within an allowed range. The result of the comparison may lead to a preset relationship of the measured values and the predetermined values. If said preset relationship between these values is achieved, e.g. the predetermined values are reached by the measured values or exceeded or approached, optionally with given threshold values, a predetermined action, as e.g. a maintenance or emergency action may be initiated. The predetermined reference value may be a threshold value or may be a range of values which is acceptable as reflecting normal elevator operation. The predetermined actions also can comprise one or more of the following actions

- elevator car is stopped, and/ or

- new runs are prohibited from starting, and/ or - elevator is set into another mode (e.g. car speed mode, elevated safety mode, such as emergency mode), and/ or

- elevator car speed is reduced,

- a diagnosis of at least a part of the elevator system is performed.

Thus, the options of predetermined actions are quite broad and can comprise the immediate till stand of the elevator, e.g. be remote opening of the safety circuit or the safe run of the elevator to the next landing but may also comprise the recording of the rope tension sensor output signals or of signal derived therefrom (e.g. FFT processed output signals). These records can be used e.g. for diagnosis purposes. Maintenance actions may comprise a notice for future regular inspections or the immediate scheduling of an extraordinary elevator inspection or even the remote checking of components via per se known remote inspection via the elevator control.

The frequency monitoring means is a per se known means which is able to detect from a signal at least one oscillation frequency. Preferably the frequency monitoring means is able to make a frequency scan of the rope tension sensor output signals over a wide frequency range, e.g. from 0,1 Hz to 50 kHz, particularly from 1 Hz to 20 kHz.

The amplitude determining means is a per se known device which is able to check the amplitude of a currently checked oscillation frequency. Such devices can e.g. calculate the difference of opposite peak values or the difference between peak values and main values of the output signal.

To ensure that these measurements are not affected by other oscillation frequencies preferably a filter means, particularly a bandpass filter, is provided to limit the operation at least of the amplitude determining means to the oscillation frequency currently to be checked. This filter means can be provided in connection with the frequency monitoring means. The term "unit" in this application does not mean that the functionality of a component has to be realised in one unit. The component can be arranged distributed and can also be integrated in other components. Thus, e.g. the frequency monitoring means maybe provided as separate modules or may be integrated with the rope monitoring device or the control means thereof or even with an elevator control or elevator group control.

The amplitude determining means may e.g. have an integrator for integrating the output signal of the rope tension sensor over a predetermined time period to obtain a mean rope tension value, and a peak value detecting means determining the maximum value of deviations of the output signal from the mean rope tension value or subtracting opposing peak values of the oscillating signal within the predetermined time window.

The oscillation frequency and oscillation amplitude is fed to a processing unit of the rope monitoring device. The processing unit is a part of the rope monitoring unit but could also be integrated in the elevator control or realized not as unit but in a distributed manner.

Preferably the elevator rope monitoring device comprises a communication interface to connect the control means with the elevator control. By this means it can be ensured that the output signal of the elevator rope monitoring device can be used by the elevator control for general safety purposes. In this connection it has to be carried out that the processing unit and/or any control means of the elevator rope monitoring device can be provided as a separate unit or module or it can also be implemented in the elevator control or in the elevator group control.

In a preferred embodiment of the invention the frequency monitoring means is configured to set a measurement time window of the amplitude determining means in accordance with at least one detected oscillation frequency. By this means a discrete measurement of the oscillation amplitude of each single oscillation frequency can be obtained, which is mostly unaffected by other oscillation frequencies. Preferably the frequency monitoring means checks in a frequency scan of the output signal of the rope tension detector different oscillation frequencies successively. By adjusting the measurement time window to a value which corresponds to one discrete frequency during this frequency scan it is possible to measure the amplitude of one oscillation frequency unaffected by other oscillation frequencies.

Preferably, a filter means, particularly a bandpass filter is used in the elevator rope monitoring device to suppress the influence of other oscillation frequencies when the amplitude of a certain oscillation frequency is measured. These filters are preferably also controlled by or integrated with the frequency monitoring means.

Preferably the measurement of the amplitudes of the different oscillation frequencies in a frequency scan is performed successively so that a discrete set of different oscillation frequencies and corresponding amplitudes is obtained. Of course, in that case each frequency /amplitude set is checked in the processing unit whether it corresponds to predetermined reference values.

There are several parameters which interact on the rope tension which establishes a constantly changing multivariable system. The rope tension changes due to

Changes in car position. This has major impact on rope tension level. This change happens gradually during movement. Car position information can be received from elevator control and used to help in sway analysis

Changes in car load. This can change only on landings, stepwise change.

Changes in car speed, i.e. acceleration/ deceleration of the ropes and car.

These affect the system behaviour. In addition, there is the factor of building sway. The building sway may cause presence of a bad resonance frequency. Due to these multiple factors numerous predetermined reference values can be provided which reflect these different parameters. Therefore, preferably the processing of the oscillation data takes place under consideration of the free rope length. On this behalf the position of the elevator car and/ or counterweight is considered for the

comparison of the oscillation frequency and/ or amplitude with the at least one predetermined value. By getting the car or counterweight position it is possible to calculate the free rope length. The free rope length is a decisive parameter for rope sways. Therefore, by considering this free rope length via the car or counterweight position it is possible to obtain more specified and exact information about allowable oscillation frequencies and amplitudes. This knowledge can be used for evaluating if an abnormal rope sway is present under consideration of the free rope length. The predetermined value can thus e.g. be established in correlation with the free rope length obtained by car or counterweight position.

As already mentioned above, further parameters which might be relevant for the evaluation of oscillations of the rope tension sensor signals are the car load and/ or the car speed /acceleration/ deceleration. These parameters can be fed to the control means of the rope monitoring device to be considered in the comparison whether a measured oscillation is allowable or not, e.g. by affecting the predetermined values. The corresponding values can be obtained via car load sensors and speed/ acceleration sensors, e.g. from the common elevator control or elevator group control.

Preferably, the elevator rope monitoring device comprises a memory for at least one reference tension value and the processing unit is adapted to generate a trigger signal for the initiation of a predetermined action if the difference between output signal of the rope tension sensor (or a value derived there from) and the reference tension value exceeds a predetermined threshold value. By this means it can be ensured that the general tension level of one or several elevator ropes doesn't drop below or rise above a predetermined level.

In an advantageous embodiment of the invention a Fourier transformation analysis is carried out for the output of the tension sensor signal(s) so as to recognize

frequencies caused by the sway of the elevator rope. Preferably, a fast Fourier transformation analysis (FFT) is carried out. By analysing the rope tension sensor signals with FFT different event which have easily identifiable "fingerprints" can easily be separated from another. Such events are e.g.:

a) car position, which causes gradual change in tension level corresponding to elevator speed

b) car loading / unloading, which causes "stepped" changes in tension level and only when car is not running (case a) is not happening) c) car acceleration, which causes gradual change in tension level corresponding to elevator nominal acceleration/ deceleration.

By using FFT lateral rope sway which also causes oscillation in the rope tension, can be easily differentiated or separated from changes in tension level that is caused by other events as e.g. by the cases a, b and c above.

Since FFT permits us to separate the level changes from oscillation change, the frequency of the rope sway can also be used to determine the position of the car (at least to a certain level and when ropes are swaying) since the rope & elevator characteristics are known.

Advantageously, for each elevator rope a separate rope tension sensor is provided so that not only changes of the rope tension of each rope with respect to a reference value can be checked but also the mutual tension value difference of each rope with respect to the others or a to a mean value thereof. This also allows to trigger a predetermined action when a preset relationship between the measured values and the predetermined values is obtained, e.g. if the difference between the measured tension values of the different elevator ropes exceeds a given or predetermined threshold value.

The elevator rope monitoring device preferably comprises a memory with a table of oscillation frequencies and amplitudes corresponding to the operation of different components in the elevator from which table the at least one predetermined reference value is derived. By this means it is possible to check whether a certain elevator component, e.g. the drive machine which transfers a certain vibration to the elevator rope is working in a normal condition. Normally, this vibration has a certain frequency corresponding to the running frequency of the drive machine as well as a certain corresponding amplitude. When the amplitude and/or frequency of the vibration transferred to the rope deviates from the corresponding preset values stored in the table it can be concluded that the operating condition of the drive machine unit is not correct so that maintenance steps can be taken. The invention also refers to an elevator comprising an elevator rope monitoring device according to the above specifications.

Preferably, the elevator has a bidirectional communication and face the remote monitoring unit so that stators information obtained by the elevator rope monitoring device can be communicated to the remote monitoring unit for processing and initiating further steps with regard to maintenance and emergency actions.

In this connection it has to be carried out that at least one component or several of the components of the elevator rope monitoring device except the rope tension sensors can be located separately or integrated in the rope monitoring device or even in connection or integrated with the elevator control or elevator group control.

Furthermore, the invention relates to monitoring the method for the rope tension of an elevator rope using rope tensions sensors According to the invention the output signal of the rope tension sensor is frequency scanned to obtain at least one oscillation frequency. Furthermore, the amplitude of at least one, preferably of each oscillation frequency is determined. By this method it is possible to check the rope tension sensor signal on different oscillation frequencies and their corresponding oscillation amplitudes which can discretely be evaluated, preferably by FFT to provide information about status or behaviour of the elevator ropes as well as of other elevator components.

Preferably, the output signal of the rope tension sensor is compared with at least one reference value to initiate maintenance or emergency actions on the elevator in result of the comparison. Predetermined action as mentioned above is then initiated if the oscillation frequency and /or its amplitude reaches a preset relationship to at least one predetermined reference value.

Preferably, the measurement time window of the amplitude determining means is adjusted to each oscillation frequency detected in the frequency scan. Preferably, the time period and the time window are set to a range of 1 to 50, particularly one to ten wave lengths of the corresponding oscillation frequency so as to suppress the influence of other three oscillation frequencies to the result of the amplitude determination. Preferably the suppression of other frequencies can be enhanced by using filters, preferably adjustable bandpass filters which can be adjusted to each evaluated oscillation frequency. This allows an unaffected measurement of the amplitude of each oscillation frequency.

By using a FFT analysis of the output signals of the rope tension sensors the above mentioned advantages which are explained in connection with FFT are obtained.

Preferably, the processing unit of the rope monitoring device comprises a record memory for the record of the output signal of the rope tension sensor over a predetermined time period for performing the FFT.

The above mentioned preferred embodiments can be combined with each other as long as this is not excluded by technically contradicting features. By this way advantages of different preferred embodiments can be combined with or may contribute to each other.

The invention is now described schematically by the aid of the drawing. This shows in Figure 1 parts of an elevator in coaction with the elevator rope monitoring device.

Figure 1 shows very schematically parts of an elevator 10 comprising a mounting structure 12 in the upper part of the elevator for fastening elevator ropes 14a - 14d of the elevator to a support structure, e.g. the wall or ceiling of a building. The ropes 14a - 14d are fixed to the support structure 12 of the elevator 10 via hangers 16a - 16e. The figure shows a rope monitoring unit 21 for monitoring the rope tension. On this behalf the rope monitoring unit 21 comprises at the base of each hanger 16a - 16e a rope tension sensor 18a - 18e. The output lines 20a - 20e of the rope tension sensors 18a- 18e are connected to a processing unit 22 of the rope monitoring unit 21. Further connected to the processing unit 22 is the output of a car /counterweight position detection device 23 of the elevator or the input for signals derived from the car /counterweight position as e.g. velocity and acceleration. Further the output signal of a car load sensor 25 can be fed to the processing unit 22. The processing unit 22 comprises a frequency monitoring means 24, an integrator 26, a peak value detecting means 28, a comparator 30 as well as a memory 32. The integrator 26 and the peak value detecting means 28 build one embodiment of an amplitude determining means. Of course these components can be substituted by other components per se know in the art for this purpose. The output lines 20a - 20e are connected to the frequency monitoring means 24, the integrator 26 as well as the peak value detecting means 28. The comparator 30 is connected via an interface 34 to the elevator control 36, whereby the interface 34 is preferably a serial communication bus. The elevator control 36 is connected, e.g. via telephone, broadcast network or internet 38 to a remote monitoring unit 40. The processing unit as part of the rope monitoring device can be a separate unit or may be part of the elevator control 36 or of a group control (not shown). Of course the processing unit may comprise or may be part of a separate control means of the rope monitoring unit 21. The processing unit may comprise a microprocessor and needs not to be realized as one unit.

The connections between the different components are as follows: The frequency monitoring means 24 comprises a filter 25 and is connected via lines 42, 44 and 46 to the integrator 26, to the peak value detecting means 28 as well as to the comparator 30. The integrator 26 is connected via line 48 to the peak value detecting means 28, and the integrator 26 is connected via line 50 to the processing unit 40. The memory 32 is connected to the comparator 30 via a line 52, whereby the memory 32 can also be integrated in the comparator 30. Further, the peak value detecting means 28 is connected via line 54 to the comparator 30.

The function of the elevator rope monitoring device 21 is as follows:

The frequency monitoring means 24 of the processing unit 22 performs a frequency scan of the signals of the rope tension detectors 18a - 18e received by the output lines 20a - 20e. In the frequency scan the frequency monitoring means 24 performs a successive measurement of each oscillation frequency of the rope sensor output signals. The frequency monitoring means adjusts a filter 25, preferably a bandpass filter, such that only a small frequency range to be evaluated is transmitted further to the integrator 26 as well as to the peak value detecting means 28. Furthermore, the frequency monitoring means 24 sets the time period for the integrator 26 to a value of e.g. five wave lengths. Of course, the value can also be chosen differently. Also the predetermined time window of the peak value detecting means 28 is adjusted to several wave lengths, e.g. half wave lengths of the evaluated oscillation frequency. By this means the integrated rope tension value is obtained as mean value and the maximum values of deviations (peaks) are measured. From these peaks the mean value is subtracted and this value forms the amplitude of the oscillation frequency. The peak value determining device may also subtract opposing peaks for getting the frequency amplitude. In this case no integrator is necessary. The amplitude of the oscillation frequency (ies) is/ are then communicated via line 54 to the comparator 30 which also receives the evaluated oscillation frequency from the frequency monitoring means 24 via line 56. Furthermore, the integrator 26 communicates the integrated rope tension value to the comparator 30 via line 50.

The comparator 30 compares the evaluated oscillation frequency as well its amplitude, eventually under consideration of signals of car position detector 23 and car load sensor 25 with predetermined values or value ranges stored in the memory 32. When allowable ranges are exceeded it either initiates any action as e.g. emergency or maintenance actions as already mentioned before or it runs a diagnosis program, which even may run continuously. In this diagnosis program any of the above data or data obtained by FFT analysis may processed and/or be communicated via interface 34 to the elevator control unit 36 which can monitor all the necessary data (e.g. oscillation frequency and amplitude) or transmit this data or data derived therefrom via internet or broadcast 38 to the remote monitoring unit. In the elevator control 36 or in the remote monitoring unit 40 corresponding actions as maintenance or emergency steps can be taken automatically or by persons working in the remote monitoring unit. Preferably, data obtained from a FFT analysis of the rope sensor output signals in the processing unit are communicated to the remote monitoring unit.

Furthermore, the output signal of the rope tension sensor or the integrator, particularly if measured over a longer time period or continuously, can be compared in the comparator 30 with a corresponding reference value stored in the memory 32. By this comparison it can be evaluated whether the general tension level of the elevator ropes is within allowed ranges.

The memory 32 can also comprise the tension values or integrated tension values of each elevator rope so that the processing unit can compare these values with each other to generate a trigger signal when deviations between the tension values of the single ropes exceed a certain threshold.

Accordingly, the invention provides safety improvement on one hand by checking the status or behaviour of the elevator ropes themselves as well as by indirectly checking the status or behaviour of other components which can be detected by vibrations or oscillation transmitted via the elevator rope(s).

In the above embodiments the number of ropes can differ from what is shown. Furthermore, the rope monitoring device 21, the processing unit 22 as well as in the single components 24, 25, 26, 28 and 30 of the oscillation detection unit can be integrated fully with the elevator rope monitoring device and /or can be integrated fully with the elevator control 36, e.g. as a module of the elevator control. Also the memory 32 can be a memory of the elevator control and must not be a separate memory of the elevator rope monitoring device.

Furthermore it should be understood, that the functional components of the invention, e.g. the rope monitoring device, the processing unit, the oscillation detection means, the control means, the frequency monitoring means , the amplitude determining means, the comparator as well as the memory can also be provided at several places in a distributed manner.

It should further be understood that instead of elevator ropes also belts or chains or other hoisting means can be monitored with the invention.

The scope of invention is not restricted by the above embodiment but may vary within the scope of the independent claims.

Claims

Claims:

1. Elevator rope monitoring device (21) for monitoring the rope tension of at least one rope in a set of elevator ropes, the monitoring device comprising a rope tension sensor (18a-18e) and a processing unit (22) for the signal of the rope tension sensor, whereby the output signal of the rope tension sensor is fed to the processing unit, characterized in that the processing unit comprises an oscillation detection means comprising

- a frequency monitoring means (24) for determining at least one oscillation frequency of the output signal of the rope tension sensor, and

- an amplitude determining means (26, 28) determining the amplitude of the at least one oscillation frequency determined by the frequency monitoring means,

whereby the processing unit (22) makes deductions from the oscillation frequency and/ or its amplitude to the status or behaviour of the elevator rope and/ or any elevator component having an effect on the rope tension.

2. Elevator rope monitoring device according to claim 1, wherein the processing unit (22) comprises a comparator (30) and a memory (32) having a number of oscillation frequencies and amplitudes corresponding to the operation of different elevator components or data derived therefrom, from which the deduction is derived.

3. Elevator rope monitoring device (21) according to claim 1 or 2, in which the processing unit (22) initiates a predetermined action if the oscillation frequency and/ or its amplitude or a signal derived therefrom reaches a preset relationship to a predetermined reference value.

4. Elevator rope monitoring device (21) according to claim 2 and 3, in which the predetermined reference value is obtained from the memory (32).

5. Elevator rope monitoring device according to one of the preceding claims for an elevator having a set of independent elevator ropes (14a-14e), whereby the rope monitoring device comprises a rope tension sensor (18a-18c) for each of the ropes.

6. Elevator rope monitoring device according to claim 3 and 5 or 3, 4 and 5, wherein the processing unit (22) is adapted to generate the predetermined action if the difference between the output signals of the different rope tensions sensors exceeds a predetermined threshold value.

7. Elevator rope monitoring device according to one of the preceding claims, wherein the processing unit (22) is configured to perform a FFT analysis on the output signal of the rope tension sensor.

8. Elevator rope monitoring device according to one of the preceding claims, wherein the frequency monitoring means (24) comprises at least one bandpass filter (25).

9. Elevator comprising at least one elevator rope (14a-14e) and a rope monitoring device (21) according to one of the preceding claims.

10. Elevator according to claim 9, comprising an elevator car and/ or counterweight position detection device (23), whereby the output of the car and/ or counterweight position detection device is connected with the processing unit (22) of the rope monitoring device (21).

11. Elevator according to claim 9 or 10, having a set of independent elevator ropes (14a-14e), whereby each of the ropes is provided with a rope tension sensor (18a-18e).

12. Elevator according to one of claims 9 to 11, wherein the control means of the rope monitoring device (21) is part of an elevator control (36) or elevator group control.

13. Method for monitoring the rope tension of an elevator rope (14a-14e), in which method the rope tension is measured via a rope tension sensor (18a-18e), whereby the output signal of the rope tension sensor is processed to obtain information about the status of the elevator rope,

characterized in that any oscillation of the tension signal of the rope tension sensor is monitored

- by frequency scanning the output signal of the rope tension sensor to obtain at least one oscillation frequency, and

- by determining the amplitude of each determined oscillation frequency,

deductions are made from the frequency and amplitude information on the status or behaviour of the elevator rope and/ or of elevator components having an effect on the rope tension

14. Method according to claim 13, wherein the position and/ or velocity and/ or acceleration and/ or deceleration of the elevator car and/ or counterweight is measured and considered for the deductions.

15. Method according to any of claims 13 or 14, wherein the load of the elevator car and/ or counterweight is considered for the deductions.

16. Method according to any of claims 13 to 15, wherein the deductions comprise the comparison of measured and predetermined reference values and the initiation of a predetermined action if the oscillation frequency and/ or its amplitude has reached a preset relationship to at least one predetermined value.

17. Method according to claim any of claims 13 to 16, wherein during the frequency scan other frequencies than the currently checked frequency are filtered via a filter, preferably a bandpass filter (25).

18. Method according to any of claims 13 to 17, wherein a fast fourier transformation (FFT) analysis is carried out on the output signal of the tension sensor signal(s).