Technique for estimating elongation of suspension of elevator car

Abstract

The invention relates to a technique for estimating the elongation of an elevator car. An embodiment of a method for estimating the elongation of a suspension device (104) of an elevator car (102) includes deriving a vibration property of a system (114) formed by the car (102) and the suspension device (104) based on measurements of oscillatory position changes generated when the car (102) is temporarily accelerated; and estimating the elongation of the suspension device (104) based on the vibration property.

Description

Technical Field

[0001] The invention relates to a method for estimating the elongation of a suspension device of an elevator car. The invention also relates to a system for estimating the elongation of a suspension device of an elevator car, as well as to a corresponding computer program product and a computer-readable storage medium. Background Art

[0002] An elevator system or elevator is understood herein as a system capable of transporting people and / or objects, loads or cargo in a moving car, cabin, cage, platform, etc., in a vertical or inclined direction between two or more horizontal planes (e.g., floors). The car is suspended on a suspension device, such as one or more ropes, belts, chains or a combination thereof. For example, the rope may have one end fixed to the car and the other end fixed to a counterweight, and is driven and / or guided by a drive pulley or a traction pulley.

[0003] Ropes and any kind of suspension device are subject to ageing, wear, etc. and are replaced based on inspections of various properties such as including monitoring and controlling tension, twisting, diameter thinning, corrosion, loose strands, brittle fractures, etc. Since human inspections are expensive, other monitoring is often required that can supplement human inspections, for example, which can allow early scheduling of maintenance, service and repairs if necessary.

[0004] A manifold of sensor devices may be provided by the manufacturer of the elevator system built into or integrated with the car, drive motor, traction sheave, etc., and may provide data relating to the status and operation of the elevator system. Such data may be stored locally, e.g. associated with a local control unit of the elevator system, for readout by local personnel, and / or may be transmitted to a remote control center.

[0005] Various parties may be involved in the management, operation and control of an elevator system. Typically, an elevator may be operated by a management company of which the elevator is part of its property, while maintenance is the responsibility of a corresponding service company, which may be a subsidiary of the manufacturer of the elevator system, or may be an independent company with some contractual relationship with the manufacturer. In common cases, the service company does not have full access to the sensor equipment and corresponding data of the elevator system provided by the manufacturer. The service company is then faced with the task of obtaining the required data. This may include installing its own sensors and establishing proprietary management of monitoring, maintenance, etc.

[0006] In a more specific example, a manufacturer will typically provide a large number of sensor devices for monitoring the condition of a rope or other suspension device. If a service provider has limited access to such a suspension device monitoring system, an alternative or supplementary system is needed that can measure the important parameters of the rope.

[0007] Therefore, there is a need for a method for estimating the status of an elevator system, in particular the suspension of an elevator system. There is also a need for establishing such status in situations where access to built-in sensing devices is limited. There is also a need for a monitoring system based on such a method, wherein such a system can be used as a supplementary monitoring system, such as an auxiliary or backup system for performing rationality checks, or as a supplementary monitoring system in the event of a failure of a built-in measuring system, or in situations where a service company has to establish its own proprietary monitoring system. There is also a need for such a method and system that enables cost-effective and / or remote monitoring of elevators and their suspension. Further, there is a need for corresponding computer programs and computer-readable media for implementing such a method and system.

[0008] At least one or more of these and other needs are met by the subject matter defined in the independent claims. Particularly advantageous embodiments are defined in the dependent claims and are discussed in the following description. Summary of the invention

[0009] According to a first aspect of the invention, a method for estimating the elongation of a suspension device of an elevator car is proposed. The method comprises: deducing vibration properties of a vibration system formed by a car and a suspension device based on measurements of oscillation position changes produced when the car is temporarily accelerated; and estimating the elongation of the suspension device based on the vibration properties.

[0010] The term "car" as used herein should be understood to include, in addition to a car or cabin, a cage, a platform, and any other device suitable for transporting persons and / or other loads (such as items, cargo, etc.).

[0011] The suspension or traction device may include one or more ropes, cables, chains, belts, combinations thereof, etc. In this document, sometimes for the sake of brevity, only "rope" may be mentioned; however, unless otherwise expressly stated, the term should be understood to include any kind of suspension, traction, suspension / traction device, etc.

[0012] The elongation or elongation of a suspension device may include any kind of tension, strain, stretching, elongation, extension, expansion, its ability thereto (particularly in its elastic manner, etc.). The stiffness or rigidity of a suspension device may be understood as a complementary property related to the elongation of the suspension device, i.e. elongation and stiffness may be converted into one another, and in this sense the terms "elongation" and "stiffness" are understood herein as interchangeable. In case the suspension device comprises a plurality of ropes, cables, etc., each rope may have its individual elongation or stiffness assigned, and the collection or set of all ropes (and any subset thereof) may have a corresponding (sub)set elongation or stiffness assigned.

[0013] The vibrating or oscillating system formed by the car and the suspension will be considered specifically to include those one or more parts or portions of the suspension that can be excited to vibrate, and this may in particular include the portion of the rope or suspension that extends between one or more fixing points thereof at the car and a pulley that releases or receives the rope (e.g. at the top of the elevator shaft, such as a traction pulley, a deflection pulley, a rope or cable drum, etc.). Other parts of the rope may also contribute to the vibrating or elastic properties of the system, for example, the behavior of the rope extending on the other side of the pulley may be transmitted through the pulley towards the car. However, this should not be understood as excluding other or further influences that may cause the vibrating properties of the vibrating system. For example, when the drive engine is stopped, the pulley or drum itself may tend to vibrate (such as rolling back and forth slightly), the bearings or mountings of the pulley may show vibrations, and the attachment of the suspension to the car may also tend to vibrate.

[0014] In more detail, the system formed by the car and the suspension device can be considered as a vibrating system based on any elastic properties of the system (in particular one or more elastic properties of the suspension device). Such properties may cause movement of the system, in particular small-scale movement. More specifically, when the car is actively driven, the car can move between floors, but during active drive and when it is not actively driven (for example, when parked at a floor), there may be other positions and position changes and movements. For the purpose of illustration only, one can consider "large-scale movement" such as actively driven movement or movement between floors, which can usually be measured in m (meters) or floors or other types of horizontal planes, while "small-scale movement" can refer to the movement of the car that occurs in principle due to the above-mentioned elastic properties of the car / rope system, and such small-scale movement of the car can usually be in the range of, for example, centimeters (cm) or millimeters (mm).

[0015] Small-scale movements may in particular include oscillations, more precisely oscillatory position changes of the car, caused by the car being excited, for example, by the car stopping (e.g. more or less suddenly), the door opening or closing, one or more persons entering or leaving, a person putting down luggage, accumulating goods, the traction sheave stopping, and rolling back and forth slightly, etc. Any such exciting event may be understood as a force impulse for temporarily accelerating the car, in particular in a direction along the elevator shaft, parallel to the large-scale movement of the car, etc., wherein such an impulse may operate on a "short" time scale compared to the time scale associated with large-scale movements, for example when the car is driven between floors, and thus "short" shall be understood in the sense of "sudden" or "sudden". It should also be noted that temporary accelerations may be caused by excitations such as a person's walking steps and / or may be caused by an oscillatory or vibratory response of the car / rope system to such excitations.

[0016] Measurements of oscillatory position changes of the car are intended to include any type of measurements of position, velocity and / or acceleration of the car that are indicative of positional behavior of the car (such as the position and changes of the car), which may be measured relative to an absolute reference (such as an absolute reference related to the elevator shaft in which the car moves) or relative to a relative reference (such as a stopping point or position that the car may approach, the damped vibration or oscillation about such a point being reflected by the measurement). It should be understood that such measurements and behaviors of interest may be related to vertical movement (i.e., parallel to gravity), for example in an upward or downward direction in a vertical elevator shaft, which does not exclude measurements and behaviors of the car in elevator configurations that deviate from a purely vertical arrangement.

[0017] The above discussion is not meant to be limiting with respect to other sources of small-scale movement of the car, such as oscillations from the building. However, it is believed that the technical effects and advantages of the present invention may be understood and achieved without detailed reference to such further influences. For example, the contribution of these further influences may be considered small compared to those discussed elsewhere herein, and / or may be offset when changes in the vibration properties of the vibration system are to be determined, and it may be believed that it is advantageous to trigger the measurement using other triggering events, such as resonant excitation, if such can be identified.

[0018] For the sake of simplicity only, the system consisting of a car and a suspension is sometimes referred to herein simply as a "car / rope system". Similarly, the vibration properties of such a system are sometimes referred to simply as "the vibration properties of the car", and it should be understood that what is meant here is the vibration properties of the car and the suspension (any type of suspension). This is also clear from the point of view that the car itself is usually or therefore may not be considered to have vibration properties relevant to the present discussion.

[0019] For example, the position behavior of the car, such as, in particular, its oscillatory position changes, can be measured by one or more position sensors, position measurement systems, position detection systems, distance measurement systems, distance measurements, etc., and also by speed sensors and / or acceleration sensors. A person skilled in the art is aware of the wide variety of sensing devices available in this regard. As just one example, an acceleration sensor or vibration sensor can be used that is sensitive enough to measure the acceleration of the car that causes / is caused by the above-mentioned small-scale movements, wherein such accelerations can typically be in the range of, for example, tens of mm / s. 2 (mm per second to the power of 2) range.

[0020] As another example, the elevator may be configured to re-level, i.e., correct or adapt the position of the car during a stop at a floor in response to a changing load of the car due to, e.g., people leaving or entering. It will be appreciated that such a re-leveling operation may result in oscillating position changes of the car of discrete steps of, e.g., +1 mm or -1 mm. For the purposes of the present invention, the measurement of the position behavior of the car may include, for example, retrieving a corresponding position indication from a re-leveling control / management system, or measuring the position adaptation in any other manner, e.g., a proprietary manner.

[0021] Compared to placing the sensor, for example, at some intermediate point of the rope or near the pulley, it may be preferable to measure the movement of the car (e.g., small-scale movement or corresponding acceleration in the millimeter range) directly at the car to achieve the desired accuracy. For example, the measuring sensor may be arranged at the top of the car or on the roof of the car, or at the bottom of the car or under the floor. Positioning sensors (such as active or passive optical sensors, infrared or lidar sensors, radar sensors, ultrasonic sensors, etc.) may measure the position of the car relative to the elevator shaft, wherein it should be noted that such measurements may be performed in a vertical or inclined direction (i.e., along the shaft) or in a horizontal direction, for example relative to a small-scale or finely graded position indication at a stop position arranged at each floor in the elevator shaft.

[0022] As another example, an accelerometer or acceleration sensor may preferably be arranged near a fixed point at the top of the car, where the car is attached or mounted or otherwise engaged to one of the ropes or ropes or a suspension device typically used to suspend / tow the car. Although one may assume that this can optimize the accuracy of the measurement, other suitable locations for arranging the sensor may also be envisioned, such as at the rope or with a view to the rope, at the middle top or bottom of the car, or even inside the car. For example, the accelerometer may be arranged inside the car, at the side wall, or under the top of the car or under the floor of the car. One reason why an accelerometer may be considered superior to other position sensor devices may be that the accelerometer can be freely arranged at the car (or ropes near the car) or anywhere in the car (or ropes near the car). However, some places in the car (such as the interior floor or panel, etc.) may be prone to secondary vibrations, which may obscure the measurement results.

[0023] The sensing device for measuring the oscillating position changes of the car may include a plurality of sensors. For example, in the case where the suspension arrangement includes a plurality of ropes, belts, etc., an accelerometer may be arranged at or near each corresponding fixing point at the car. The data provided by the plurality of sensors may be processed for each sensor, or may be processed to average a plurality of measurements, perform error correction, etc., and this may enable, for example, correction of effects caused by small-scale movements of the car in the elevator shaft, vibrations of attachments at one or more fixing points of the ropes, etc.

[0024] The terms "vibration" and "oscillation" are used synonymously herein. Calculating or determining the vibration or oscillation properties of the car / rope system may include calculating or determining the vibration frequency, vibration amplitude and / or other properties, such as vibration (oscillation) time, angular frequency, energy of oscillation, etc., and also calculating or determining the envelope of the amplitude measured within the measurement time, etc.

[0025] The vibration or oscillation frequency of the car may also be referred to as the bounce frequency, which may be considered to take into account that the elevator shaft and the movement of the car therein are arranged vertically (i.e., parallel to gravity), and these terms are therefore also used interchangeably herein. This should not be misunderstood as excluding elevator shafts (and corresponding car movements) that are not arranged strictly vertically.

[0026] The vibration or oscillation frequency of the car can be considered as the resonant frequency (or natural or eigenfrequency) of the car / rope system, as will be discussed further below, and therefore these terms may be used interchangeably herein. The use of these terms is not intended to limit the invention in any particular physical interpretation or modeling.

[0027] The terms "determine" and "estimate" may also be used synonymously herein. It should be understood that given the complexity of the vibration system being measured as discussed throughout this document, as well as the measurements themselves and their analysis, the determination of the vibration properties (or changes thereto) and the corresponding rope elongation (or changes thereto) may provide useful results, however with limited accuracy depending on the design of the determination / estimation system, cost effectiveness, etc. However, the use of any such terms is not intended to limit the present invention or exclude the technical effects or advantages of the present invention.

[0028] Estimating rope elongation from derived vibration properties of the car / rope system may include any given relationship between reference elongation and vibration properties, where such relationship may be expressed as a formula or equation, a table, a database, a combination thereof, etc., and where such relationship may be based on theoretical modeling, measurements, experience, etc. Any such relationship may be generally applicable, or specifically applicable to a given rope, rope model, type or series, etc.

[0029] Estimating the rope elongation may include estimating a change in the elongation, in particular based on a change in a derived vibration property of the car / rope system. For example, determining or estimating a change in a vibration property of the car / rope system may include analyzing and comparing a plurality (i.e., two or more) measurements of a change in an oscillating position of the car, and one or more of the corresponding calculated vibration properties. For example, a change in frequency, amplitude, an envelope of the amplitude, etc. may be determined or estimated.

[0030] Multiple measurements of oscillation position changes to be combined, compared, or otherwise included in the estimate may have one or more common properties for meaningful analysis. It should be noted that any such measurements may be generated by the same or similar trigger conditions or triggers, and / or may be identified in the available measurement data as being similar in terms of desired configuration, properties, etc.

[0031] For example, measurement results can be correlated to each other, which are performed as much as possible by the same sensor or sensor device under comparable operating conditions of the sensors, such as, for example, sampling frequency, measurement or sampling time, accuracy, sensor internal error correction, software / firmware version of the sensor, etc.

[0032] As another example, the change in elongation or stiffness may preferably be estimated based on measurements where the cars have the same mass or weight, such as where the cars are the same or similar model or type, series, etc., and the equipment of the cars is similar, such as interior equipment (e.g., wall coverings, metal or glass labels, mirrors, etc.), including the same or similar interior doors, but also the same or similar with respect to exterior equipment (e.g., components on top of the car or under the floor, etc.).

[0033] Furthermore, it may be intended that, in order to correlate the measurements, the car loads should be identical or similar. The "load" or "car load" or "cabin load" of a car is understood to be the payload, load capacity, working load, etc. carried by the car or cabin. More specifically, the load may include one or more persons or passengers and / or cargo carried by the car. Such a load may be expressed as a mass or weight, for example in kg (kilograms) or t (tonnes), or as a number of persons (wherein a "person" may have an assumed average weight), or as a fraction of the total or maximum load allowed.

[0034] As a specific example, measurements may be correlated where the operation of an elevator includes people entering a car (such as the first or a single person entering an empty car), or people leaving a car (such as a single or a last person leaving a car).

[0035] In practice, the measurements differ from each other because, for example, people have different weights, carry or do not carry luggage, etc. For measurements that can be related to each other, the car load can be considered "similar" or "comparable" if the weight difference is small compared to the total weight of, for example, an empty car, a system of car and ropes, etc., where "small" can mean some fraction, such as less than 25% of the total weight, preferably less than 10%, more preferably less than 3%, most preferably less than 1%. It should also be understood that the question of "similar" or "comparable" loads or "small" differences also depends on the expected accuracy of the result (i.e. the estimated rope elongation or stiffness or its change).

[0036] According to another example, measurements may be related to each other, which are performed at the same or adjacent floors (or other types of levels). For example, where a measurement may be performed when the car is stopped at floor "N" (e.g., at floor "1" or "10" or "30" or "100" or "-10"), such measurement may be compared with other measurements made at the same floor N or (e.g., in the absence of such measurements) at nearby floors (such as, at N+1, N-3, etc.).

[0037] The term "adjacent" may be understood as defining a set of floors that are expected to have comparable vibration properties of the car / rope system. For the example of the vibration frequency of the car during a stop at a particular floor, as long as the length of the rope between the drive or traction sheave and the car (traction length) is comparable, the measurements may be considered comparable. In particular, "comparable or comparable" may relate to the accuracy of the estimate of the rope elongation or stiffness that is expected or that can actually be achieved. For example, if the vibration frequency or the variation of the estimated car load between nearby floors can be expected to be below a given accuracy, then such floors may be considered "adjacent" and the corresponding measurements "comparable".

[0038] In practice, the number of "adjacent" floors may be small compared to the total number of floors, the total length of elevators (elevator shafts), etc. For example, a given fraction of all floors may be considered "adjacent" to each other, e.g., 1 / 10 of all floors may be considered adjacent to each other, or 1 / 5, or 1 / 4, or 1 / 3, or 1 / 2 of all floors may be considered adjacent to each other.

[0039] According to another practical example, the traction lengths of the ropes may be considered comparable to each other, wherein the difference in length (between the pulley and the fixed point at the car) is 1 / 10, or 1 / 5, or 1 / 4, or 1 / 3, or 1 / 2. However, it should be noted that examples can be envisaged, wherein, for example in the case of a freight elevator, the length of the rope from the traction sheave to the car at the uppermost floor may be longer than the difference between the uppermost floor and the lowermost floor. For such examples, the measurements taken at all floors may be considered comparable, i.e. all floors are "adjacent" to each other.

[0040] As another example, measurements may be repeated (and then correlated to each other) over a time scale where detectable changes in rope elongation or stiffness may be expected. Specifically, if it is believed that rope conditions, such as characterized by stiffness or elongation, may change over time scales of months and years until the rope is to be replaced after a year or more, then changes in stiffness or elongation may be estimated from measurements performed at time intervals between which are a reasonable fraction of the replacement time scale, where the term "reasonable" may relate to the expected accuracy of the estimate. For example, rope conditions may be considered constant over "short" time scales compared to replacement times, and for example, for a replacement time of 1 year (yr), "short" may mean time intervals or timespans of 1 month or less, or for a replacement time of 10 years, 25 years, etc., "short" may mean measurement time intervals or timespans of 1 year or less.

[0041] It should be noted that in the case of a suspension device comprising a plurality of ropes, cables, etc., replacing only one of these may not significantly change the properties of the suspension device as a whole. In this case, it may be difficult to estimate the change in elongation of a single rope from the measurement of a vibration system comprising the entire suspension device. However, in other cases, the measurement may be expressive in the case of replacing all or part of all ropes at once. For example, in the case of a suspension device comprising two ropes and replacing one of the ropes alternately every few years, when the measurements are taken at intervals of, for example, 1 yr, the state or aging of the suspension device formed by the two ropes can be measured and the measurements compared to each other.

[0042] According to some embodiments, the car / rope system (more generally, the vibration or oscillation system formed by the car and the suspension device) can be considered as a spring pendulum, a spring oscillator or a spring mass system. The elongation or stiffness of the rope or suspension device can then be estimated based on the spring-mass-vibration or oscillation formula or equation.

[0043] As an example, the following equation can be used:

[0044] ,

[0045] Where f is the vibration frequency of the system, c is the stiffness of the suspension, m1 is the vibrating mass of the system, F is the force, and ε is the elongation of the suspension.

[0046] It should be noted that the oscillating mass m1 may comprise the (current) mass or weight of the car at the time of measurement, i.e. the mass of the car in the case of an empty car only, or the mass of the car including the load if there are any persons, cargo etc. in the car. Furthermore, the mass m1 may comprise at least a part of the mass of one or more ropes (e.g. a part extending between the traction sheave and the car), if not included, the mass of the one or more ropes may be negligible compared to the mass of the (loaded) car. The amount or part of the ropes that is considered to contribute to the mass of the vibrating / oscillating system may vary between elevator systems, cars etc. and may be determined based on, e.g., tests, a series of test measurements, corresponding tables, experience etc.

[0047] According to some embodiments, the vibration frequency f can be used to estimate the stiffness c and / or elongation ε of the car / rope system, wherein the car can be assumed to be rigid, so that the stiffness c and the elongation ε are the stiffness and elongation of the suspension device in the suspension / movement direction of the car. In one example, the rope elongation can be determined from a table, a database, etc., in which the values ​​of the (measured) oscillation frequency f are associated with or mapped to the (effective) values ​​of the corresponding elongation ε / stiffness c. Such a mapping can be prepared and provided based on test measurements, auxiliary measurements, theoretical calculations, experience, etc. Instead of a table, an equation or tool can be provided, which, optionally, calculates other parameters (such as parameters related to the elevator, elevator system, rope, rope type, etc.) as output for the corresponding or effective value of elongation or stiffness when the measured frequency is input.

[0048] As a specific example, it may be recalled that the elongation of the rope estimated from the measured oscillating position changes of the car may not only be due to the elastic properties of those parts of the rope extending between its fixing point at the car and the (first) pulley, but that the rope also extends further on the other side of this pulley and further one or more parts of the rope may also contribute to the effective measured and estimated elongation. Therefore, it may be considered preferable to perform a test measurement, a series of test measurements for an elevator type, a system, a specific elevator, etc., in order to represent the complex behavior of the oscillating system in a map, a table, an equation, etc., which then allows the effective elongation to be determined from a single measured frequency.

[0049] As a further example, the values ​​of the stiffness or elongation of the free rope and parts thereof may be known, e.g. for a new rope, or may be measured for an old rope, e.g. after replacement. Further measurements are performed at test measurements or during normal operation, where such ropes are used in a particular elevator system. Measured and estimated values ​​of the effective stiffness or elongation of the built-in rope may be associated with the stiffness and elongation values ​​of the free rope, and this may be stored in a database or the like, which may then be used to estimate the "free" elongation or stiffness of the built-in rope as a parameter defining the rope state.

[0050] In the above formulas, as described above, the relevant changes in the spring constant, or the rope stiffness, or the elastic strain or elasticity c of the rope, and / or the elongation, strain or unit elongation ε can be assumed on a time scale of a reasonable fraction of the replacement time, and such time scales may also be known from, for example, theoretical considerations, tables, experience, etc.

[0051] According to some embodiments, the change in the vibration frequency f can be used to estimate the change in the stiffness c and / or elongation ε of the car / rope system. In a specific example, the current elongation of the rope can be determined as follows: in the absence of other changes such as in the (effective) mass m1 of the vibrating car / rope system, the estimated difference or change in the vibration frequency f is converted into a difference or change in the elongation ε. More specifically, measurements that are related or comparable to each other can preferably be made with the same car, car load and / or at the same given floor, as discussed above and elsewhere herein.

[0052] For example, measurements of an empty car in response to a single person entering may be preferred over measurements of a car filled with multiple people in response to another person entering, in order to minimize weight differences; however, the test measurements may rely on standardized car loading. More generally, various differences in measurements may be considered negligible, such as discussed elsewhere herein for adjacent floors, different car loadings, etc. As another example, differences in rope length due to measurements at different (nearby) floors may be accounted for by corrections to mass m1 in the above formula, since the mass of a rope extending between one floor, two floors, etc. may be approximately known.

[0053] Comparing the currently measured oscillation frequency with the earlier measured frequency may yield a stiffness or elongation ratio. For example, such a ratio may be understood as expressing the current stiffness / elongation according to the initial stiffness / elongation when, for example, the rope was new. Such a value may be considered as an indication as to whether the rope must be replaced according to a table, map, etc. provided by, for example, the manufacturer of the rope, etc.

[0054] According to some embodiments, the estimated change in stiffness or elongation may enable a value to be assigned to the current stiffness or elongation of the suspension device, and this may be based on, for example, a relevant number of measurements, which refer to guesses at the resulting change in vibration frequency, knowledge of the extreme values ​​of vibration frequency for new ropes, aged ropes, ropes to be replaced, etc., and this knowledge may be represented in a mapping, table, equation, calculation tool, a combination thereof, etc., as discussed for the case of estimating elongation / stiffness from only a single measurement.

[0055] As a specific example, the measurements made for comparison may involve an empty car, wherein the oscillation frequency of the empty car may involve exciting the empty car to vibrate simply by having it parked at a given floor, or by having the first or a single person enter or leave the car when the car is parked at a given floor. Preferably, such measurements may be arranged as a measurement campaign comprising measurements on all floors, (e.g. once a year), thereby generating a series of estimated elongations per floor, which may enable a more comprehensive overview of the rope status than a single measurement on a given floor.

[0056] In yet another example, the measurements may relate to a non-zero car load, such as the car carrying multiple persons and / or one or more persons, in particular the last person to enter the car. If the measurements are to be made during normal operation, such measurements may preferably be related to each other. For example, various measurements may be made and stored in a database from which measurements with comparable or equivalent parameters may be identified, guessed, etc., and selected in a post-processing operation.

[0057] As discussed above, this generally depends on the desired accuracy of the stiffness / elongation estimate, which affects the vibration properties of the car / rope system under consideration, and which corrections are applied or included in formulas such as those described above. As an example, depending on the expected accuracy, the estimated difference or change in the vibration property (such as the oscillation frequency f) may be ignored or discarded if the difference is below a given threshold, i.e., in this case, it may be determined that the current stiffness or elongation is substantially unchanged compared to the previously measured stiffness or elongation.

[0058] As already discussed above, a general method for estimating the state of a rope based on its stiffness / elongation properties may comprise performing one measurement or correlating a plurality of series of measurements with one another, wherein each series comprises measurements at a plurality of floors (e.g. a subset of all floors). The measurements or measurement results correlated with one another may also be weighted according to similarity (e.g. with respect to the same or adjacent floors, the same or different loads, etc.) and the respective assumed accuracy of the estimation.

[0059] It should be noted that estimating the current rope stiffness or elongation based on a comparison of the current or most recent measurement with older measurements, e.g., 1 year ago, 10 years ago, combinations thereof, etc., is only one practical application of the present invention, wherein of course all measurements made "older" with respect to the processing time may be compared or correlated with each other, e.g., to generate a timeline of measured / estimated rope elongations. For example, such an approach may include batch processing of measurements stored in a database for one or more elevators to be categorized by building, rope manufacturer, rope properties, etc. It should be reminded that the expected accuracy of the stiffness / elongation estimate may depend on its intended use, and for such statistical properties, the limited accuracy provided by cost-effective sensing and processing equipment may be sufficient.

[0060] According to embodiments of the present invention, an indication of the estimated stiffness or elongation may be provided or forwarded to a monitoring and / or control system, for example, for maintenance control. For example, embodiments may assist, supplement, or replace monitoring based on OEM sensor equipment of an elevator system. For example, a stiffness / elongation estimation system according to the present invention may be provided external to the car at any time after manufacture and installation of the elevator system, and may operate completely independently of any built-in sensing and monitoring systems. Thus, for example, embodiments may be used to monitor an elevator system with limited access to a built-in monitoring system.

[0061] Embodiments of the present invention are particularly suitable for remote monitoring. For example, one or more of the proposed derivation or estimation steps, actions or operations can be initiated, executed and / or controlled by a remote monitoring facility such as in a corresponding control or operation center. According to a specific example, although the start of a specific measurement can be triggered locally, for example, by detecting an event indicating a car stop, door opening, etc., a remote signal or command can also activate, for example, a sensor device, a local trigger detection mechanism, etc. The remote signal can start and / or control a local measurement activity covering measurements at multiple floors within a given time (e.g., one hour, one day, etc.). Data representing the measurement results can be pushed to a remote repository for further processing, or can be stored locally and accessed from a remote monitoring center as needed.

[0062] The derivation of the vibration properties can be performed locally and / or at a remote server or monitoring facility, e.g. depending on whether and which other data are accessed or retrieved, querying a database, etc. Similarly, the estimation of stiffness or elongation can be performed locally or at a server. In general, server-based or platform-based solutions can enable more complex derivation or estimation processes. As an example, a server can be configured to access a database storing, e.g., elevator systems of different manufacturers, technical properties of a specific elevator, parameters, etc., and can retrieve parameters as needed for a specific measurement or measurement campaign.

[0063] As another example, the server may be configured to access a database storing, for example, earlier measurements in the same or similar buildings, measurements of similar elevator systems, types, etc., which may enable appropriate selection of one or more earlier measurements to compare with the current measurement. Similarly, any kind of post-processing may also preferably be implemented at the server, such as generating a timeline of elongation per rope, rope type, model, etc., which may allow the service company to build a knowledge database for the facilities it serves.

[0064] According to another aspect of the present invention, a computer program product is proposed, the computer program product including a program code portion, when the computer program product is executed on one or more computing devices, the program code portion is used to perform and control at least one of the one or more methods described herein. Generally, embodiments of the various methods proposed herein can be computer-implemented. For example, any one or more steps can be performed in a processing unit such as a central processing unit, a CPU, a microprocessor, a controller, a microcontroller, etc. Such a processing unit may have a memory associated therewith for storing control commands for executing a computer program, such as a cache memory.

[0065] According to another aspect of the invention, the computer program product may be stored on a computer-readable medium, such as a permanent or rewritable memory within or associated with a computing device, such as a flash memory, a ROM, a PROM, an EPROM or a removable CD-ROM, a DVD or a USB-stick. Alternatively, the computer-readable medium may be a fixed device, such as another computer or a server, which may be part of a server farm, a data cloud or other distributed storage facility, where the computer program may be provided for access, for example, by downloading via a data network (such as the Internet, a WAN and / or a LAN) or a communication line (such as a telephone line or a wireless link).

[0066] According to another aspect of the present disclosure, a system for estimating the stiffness and / or elongation of a suspension device of an elevator car is provided. The system comprises: a module configured to derive a vibration property of a vibration system formed by the car and the suspension device based on a measurement of an oscillation position change produced when the car is temporarily accelerated; and a module configured to estimate the elongation of the suspension device based on the vibration property.

[0067] The system may also include a sensor for making measurements of oscillatory position changes of the car. The sensor may include a positioning sensor or positioning measurement system suitable for measuring position changes of the car, particularly on a small scale as described above, including but not limited to re-leveling measurements. Specific examples may include position sensors (such as photoelectric sensors, laser sensors, ultrasonic sensors, inductive sensors, magnetic sensors, capacitive sensors), but also mechanical sensors, strain sensors, etc. Additionally or alternatively, one or more sensors may include one or more velocity sensors, acceleration sensors or accelerometers, vibration or shock sensors, gravimeters, combinations thereof, etc.

[0068] Any one or more sensors may be configured to be arranged at a fixed point (fixed point, fixed point) at the car of a suspension device (such as a mounting piece attached to a rope at the car). For example, the sensor may be integrated in a box or housing with one or more system modules, and the box may be arranged at the fixed point. According to other examples, in the case where the car is suspended by multiple ropes, cables, etc., each (or some, subset) of the multiple fixed points may be equipped with a positioning sensor, an acceleration sensor, a combination thereof, etc.

[0069] In general, it should be noted that any sensor need not necessarily or exclusively be mounted or attached to the car, although this may be preferred for measuring the behavior of a vibrating car / rope system. Sensors may also or even only be placed at one or more points at the ropes. Although oscillation position changes, shifts or vibrations may be less noticeable than at the measurement point directly at the car, so that the measured vibration amplitude may appear damped, the estimate of the oscillation or vibration frequency should be consistent. Therefore, sensor positioning at the car and / or ropes can be considered as an option, where the measurements from various places can be added to each other, complement each other, etc., depending on, for example, the available space, the cost of sensor attachment at the car or ropes, etc.

[0070] The stiffness and / or elongation estimation system can be implemented by a data processing device, a data storage device, optionally one or more of the above-mentioned sensor devices, wherein the system can be arranged locally at the car and / or at a remote location (for example, in a remote monitoring facility), wherein the local processing can include pre-processing, such as receiving commands from a distance and preparing commands for local processing accordingly, starting and performing measurements, buffering or storing measurement data, providing or sending measurement data, and the remote processing can include any kind of post-processing based on the measurement data, intermediate data or final data, such as processing for deriving vibration frequency and / or estimating rope elongation.

[0071] As a specific example, a housing, a casing, a box, etc. can be arranged locally or on-site at the car, the box including one or more of a power supply device, a data communication device, a data processing device, a storage device for storing commands, data (such as, a database, a data log, a command and measurement history, a measurement data, a received data, a data to be sent, etc.). One or more sensors can be arranged in the housing or separately and connected via a cable and / or wirelessly for independently attaching the box and the sensor to the car, the elevator shaft, the rope, etc. According to another example, in the case of multiple rope fixing points at the car, each fixing point can be equipped with a box with an integrated sensor. Alternatively, one or more fixing points can be equipped with sensors, and the sensors are connected to one or more boxes arranged near the car top, near the stopper at the elevator shaft, etc.

[0072] It should be noted that some embodiments of the present invention are described herein with respect to methods for estimating the stiffness or elongation of a rope, while other embodiments are described with respect to systems configured to implement such methods. It will be readily appreciated by those skilled in the art that features may be appropriately transferred between these various embodiments, and features may be modified, adapted, combined and / or replaced, etc. to implement other embodiments of the present invention. BRIEF DESCRIPTION OF THE DRAWINGS

[0073] In the following, advantageous embodiments of the invention are described with reference to the accompanying drawings. However, neither the drawings nor the description should be interpreted as limiting the invention.

[0074] Figure 1 is a functional block diagram schematically showing an elevator system equipped with a rope elongation estimation system according to an embodiment of the present invention.

[0075] Figure 2 Schematically shows Figure 1 The elevator car responds to people entering.

[0076] Figure 3 By way of example Figure 2 The sensor measurements of the responses shown in FIG.

[0077] The drawings are schematic and not to scale. Identical reference numerals indicate identical or similar features. DETAILED DESCRIPTION

[0078] Figure 1Schematically illustrated is an embodiment of an elevator system 100 comprising an elevator car 102 suspended by a suspension arrangement, which for simplicity is shown as comprising a single rope 104. A vibration sensor 106 is arranged at a fixed point of the rope 104 at the car 102. For example, the sensor 106 may be a single-axis accelerometer that measures acceleration / vibration in a direction along an elevator shaft (not shown) in which the car 102 is moving.

[0079] The sensor 106 is controlled by a sensor control module 108. For example, the module 108 may trigger the sensor 106 to begin measuring each time the car 102 stops, which may be determined based on data also provided by the vibration sensor 106 (such as, for example, data permanently transmitted from the sensor 106 at a low sampling rate). Measurements intended to represent oscillatory small-scale movements or position changes of the car 102 may include acquiring data at a higher sampling rate, sensitivity, etc., for a predetermined time (such as 10 seconds or 30 seconds) or any time span deemed sufficient to cover a typical stop of the car 102 with passengers entering and / or leaving. For example, a typical sampling rate may be 10 Hertz (Hz) or 5 Hz, as described below. The control module may buffer the measurement data in a buffer 110 for further processing.

[0080] The derivation module 112 is configured to derive the vibration properties of the vibration or vibrating system 114 formed by the car 102 and the rope 104. In particular, the module 112 can calculate the vibration frequency of the system 114 based on the measurement data in the buffer 110, as discussed and shown in more detail below. The calculation may include identifying oscillations in the data. More specifically, an oscillation event may be identified in the data, and the calculation result may include one or more corresponding oscillation frequencies. It should be understood that the oscillation may be caused by an excitation event, such as, for example, one or more people entering or leaving, but may also be caused by a more or less sudden stop of the car, the drive pulley, a person putting down luggage, etc. A weight or ranking value or position may also be assigned to the identified oscillation frequency, which indicates the absolute or relative strength or intensity of the identified oscillation, which may, for example, help identify a resonant oscillation (if any). The derivation module 112 may store its calculation results in the buffer 116.

[0081] The estimation module 118 retrieves (push or pull) vibration property data from the buffer 116 for determining or estimating a change in the oscillation frequency compared to an earlier measurement, estimating a change in the elongation of the rope 104, and optionally indicating a current elongation of the rope 104. Data on the (non-)detected change in oscillation frequency, stiffness and / or elongation of the rope or ropes involved (which optionally estimates a relative / absolute value of the current rope stiffness and / or elongation) may be provided to various other facilities 120, e.g. for presentation, storage, further processing.

[0082] Figure 2 Schematically shows Figure 1 The vibration response of the car / rope system 114 to an excitation event, specifically, a single (e.g., first) person entering the car 102 during the time when the car 102 is parked at a given floor. Specifically, for the first case 200, it is assumed that at a given point in time (such as on a specific calendar date of a year), the measurement is performed under defined conditions, including an empty car 102 parked at a given floor, one or more doors open, and a person (such as a test person, an operator, etc.) entering the car 102, which causes the vibration system 114 to be excited to vibrate or oscillate at a first frequency f1, as schematically shown by the wave train 202. The second case 204 assumes that the measurement is repeated under the same or similar conditions as much as possible, a test person of the same weight, etc., on the same calendar date, for example, one year later. The vibration response of the car is measured again and characterized by a second frequency f2 as shown by the second wave train 208.

[0083] As shown by the difference in wave trains 202 and 208, without prejudice, it can be considered that the frequencies f1 and f2 differ from each other due to differences in the stiffness or elongation of the rope 104, and that the conditions of the vibration system 114 and other parameters are as identical or similar as possible for both cases 200 and 204, which can be achieved by arranging the test campaign accordingly or by selecting appropriate measurements from a set of measurements performed during normal operation of a measurement campaign lasting, for example, a full day. Therefore, the vibrating mass m1 can include the mass of the same car 102, the same (multiple) portions of the rope 104 (defined by the same given floor), and a comparable test person (e.g., any person of average weight) entering the car 102. Based on the specific example of the spring mass formula discussed above, one can expect the ratio of the rope elongation to be ε2 / ε1 = (f1 / f2) 2 , and the elongation change of the rope during the time interval between measurements (eg 1 year (yr)) can be estimated from the determined frequencies f1, f2.

[0084] Figure 3 is shown in more detail by the corresponding measurement 300 Figure 2Example temporary acceleration / time diagrams for cases 200 and 204. Assuming that the vibration sensor 106 on the car 102 (see Figure 1 ) measures the vertical acceleration of the car 102 and is expressed in mm / s 2 The measured data 302 in units of seconds are graphically represented along a time axis 304 in units of arbitrary seconds (s). The individual time points at which local maxima of the acceleration have been exemplarily identified for the case 200 are also indicated for illustration purposes only. From the identified local maxima (or minima, or other characteristic parts of the measurement), the oscillation frequency (or frequencies) can be derived. This does not mean that other frequency detection or calculation algorithms are excluded, such as calculation algorithms based on (fast) Fourier transform mechanisms.

[0085] Although shown for ease of comparison on a continuous time axis 304, it is reasonable to consider the data representing situation 204 as measured later, for example, 1 year later, as described above. The derivation of the oscillation frequency can be performed similarly to that discussed above for the measured data representing situation 200, the change in frequency can be estimated, and the change in the elongation of the rope 104 can be estimated from this.

[0086] Also like Figure 3 As shown, in addition to evaluating the change in oscillation frequency, one may also consider the change in oscillation amplitude, including the change in the envelope of the oscillation / excitation event, where a slight increase in elongation may not only result in a decrease in the oscillation or bounce frequency, but also in an increase in the amplitude and a difference in the envelope. However, it is to be noted that a focus on the vibration frequency may be considered preferred, since, for example, the amplitude and / or envelope of the oscillation may be affected by the response of the re-leveling mechanism (if present), and this effect may be different for different rope elongations, i.e. may be difficult to take into account.

[0087] Figure 3 Typical car oscillations are shown in the range of 2 Hz-3 Hz, and thus a suitable sensor for measuring small-scale oscillations of the car / rope system 114 may have a sampling frequency of, for example, 5 Hz or higher.

[0088] It should be noted that the human walking frequency is usually assumed to be about 2 Hz, which may be close to the natural or eigenfrequency of the elevator car / rope system, such as Figure 3 Thus, a person entering the car (or exiting the car) can be considered as a resonant excitation, and thus the measurement of the oscillating position change of the car / rope system can simply be arranged at the time of entry or exit, for example after the car has stopped during normal operation.

[0089] The foregoing discussion is not meant to limit or exclude other interpretations of the technical effects and advantages of the embodiments of the present invention. In fact, exciting the car or car / rope system to respond with oscillatory behavior does not require resonant excitation such as caused by multiple walking steps of a person, but a single force impact or excitation with a frequency (spectrum) other than the resonant frequency may also cause system oscillations that can be measured and analyzed, such as, for example, the stopping of the car itself, or the accumulation of items or cargo in the car, where the relevant momentum will be transferred to the car during the accumulation.

[0090] Return to reference Figure 1 For example, the load estimation system 105 can be implemented in one or more boxes and data can be read out during maintenance inspections. However, the various functional modules of the system 105 are suitable for implementation in a distributed manner. In a specific example, the sensor 106, the control module 108, the buffer 110 and the frequency derivation module 112 can be arranged locally, for example, they can be integrated on a single printed circuit board PCB, which can be easily arranged at the car. It should be noted that according to an example embodiment, the minimum sensing device can only include a single (unidirectional) acceleration sensor. For example, the same such sensor can be used to detect a triggering event (such as a car stop), and then record or measure the excitation event and the response to the excitation event, such as the oscillating position change of the car caused by a temporary acceleration related to one or more sudden force impacts, such as from a person's walking steps.

[0091] Furthermore, the current vibration frequency can be calculated immediately from the measurement, so that there is no need to store the measurement data permanently, and this may also help to make the footprint of the local installation small.

[0092] Any data in the buffer 116 (such as a record storing the calculated or derived frequency using, for example, a timestamp, floor number, etc.) can be stored and / or transmitted to a remote monitoring center 124 implementing the estimation module 118 via the network 122. This enables efficient remote monitoring of, for example, rope elongation, rope status, etc. of a third-party elevator system.

[0093] Finally, it should be noted that the term "comprising" does not exclude other elements or steps, and "a" or "an" does not exclude a plurality. Elements described in association with different embodiments may be combined. It should also be noted that reference signs in the claims should not be construed as limiting the scope of the claims.

[0094] Reference numerals list

[0095] 100 Elevator System

[0096] 102 Car

[0097] 104 Rope

[0098] 105 Elongation Estimation System

[0099] 106 Vibration Sensor

[0100] 108 sensor control module

[0101] 110 Buffer for measurement data

[0102] 112 Derivation Module

[0103] 114 Vibration System

[0104] 116 Buffer for result data

[0105] 118 Estimation Module

[0106] 120 Follow-up Processing

[0107] 122 Data Transmission Network

[0108] 124 Remote Monitoring Center

[0109] 200 First Car Situation

[0110] 202 First Wave

[0111] 204 Second Car Situation

[0112] 208 Second Wave

[0113] 300 measurements

[0114] 302 Measured acceleration

[0115] 304 Timeline

Claims

1. A method for estimating the elongation of a suspension device of an elevator car, the method comprising: deriving vibration properties of a system (114) formed by the car and the suspension device (104) based on measurements (300) of oscillating position changes that occur when the car (102) is temporarily accelerated; and An elongation of the suspension device (104) is estimated based on the vibration properties.

2. The method according to claim 1, in, The oscillating position change occurs when the car (102) is temporarily accelerated due to a person entering the car (102) or leaving the car (102).

3. The method according to claim 1 or 2, in, Deriving the vibration property includes calculating a resonant frequency of the vibration system (114).

4. The method according to any one of the preceding claims, in, The vibration properties are derived based on considering the system formed by the car (102) and the suspension device (104) as a spring-mass system.

5. The method according to claim 4, in, The vibration properties are calculated according to the following formula: ， Wherein, f is the vibration frequency of the system (114), c is the stiffness of the suspension device (104), m1 is the vibration mass of the system (114), F is the force, and ε is the elongation of the suspension device (104).

6. The method according to any one of the preceding claims, in, Estimating the elongation of the suspension device includes estimating a change in elongation based on a change in the vibration property.

7. The method according to claim 6, in, The change in stiffness or elongation is estimated from measurements performed at the same or adjacent floors.

8. The method according to claim 6 or 7, in, Estimate the change in stiffness or elongation from measurements performed at the same or comparable load.

9. The method according to any one of claims 6 to 8, in, The change in stiffness or elongation is estimated from measurements performed at time intervals of at least three months, preferably at least six months, more preferably at least one year.

10. The method according to any one of the preceding claims, An indication of the estimated elongation is provided to a remote elevator monitoring and / or control system, such as maintenance control.

11. A computer program comprising instructions which, when executed by a computing device, cause the computing device to perform a method according to any one of the preceding claims.

12. A computer-readable storage medium having stored thereon a computer program according to the preceding claim.

13. A system (105) for estimating the elongation of a suspension device (104) of an elevator car (102), the system (105) comprising: a module (112) configured to derive vibration properties of a system (114) formed by the car (102) and the suspension device (104) based on measurements of oscillating position changes produced when the car (102) is temporarily accelerated; and A module (118) is configured to estimate an elongation of the suspension device (104) based on the vibration property.

14. The system according to claim 13, The device further comprises a sensor (106), wherein the sensor (106) is used to perform the measurement, and the sensor (106) preferably comprises at least one of a position sensor and an acceleration sensor, and more preferably comprises a vibration sensor.

15. A system according to claim 13 or 14, in, The sensor (106) is configured to be arranged at a fixing point of the suspension device (104) at the car (102).

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