Patent Description:
Known elevators comprise an elevator car adapted to move in an elevator shaft along a vertical trajectory which is defined by guide rails. The elevator car has guide shoes, such as sliding guide shoes or guide rollers, which meet the guide rails to guide the movement of the elevator car.

The guide rails are mounted to vertical hoistway structures of the elevator, such as to the walls thereof. They consist of a plurality of guide rail sections placed one after the other. The guide rail sections are fixed to the hoistway structures by means of fixing members, such as brackets.

The guide rails can, however, buckle and bend under certain circumstances. This may affect the elevator ride comfort and may even be a reliability issue and lead to malfunctions. Therefore, it is necessary to detect such a condition. It is known to use different kind of measurement and monitoring equipment for detecting guide rail alignment. However, the pieces of equipment are often expensive. They can also be large, heavy and inconvenient to use in the elevator hoistway.

Document <CIT> presents a safety actuation device for an elevator system including an elevator car and a guide rail. The safety actuation device includes a safety brake disposed on the car and adapted to be forced against the guide rail when moved from a non-braking state to a braking state. An electronic safety actuator is operably connected to the safety brake. The electronic safety actuator includes at least one sensor configured to monitor one or more parameters associated with a ride quality of the elevator car, such as the condition of the guide rail.

Document <CIT> presents a method in which an elevator hoistway rail profile is made during an elevator car learning run by summing a doubly integrated car horizontal acceleration signal with a relative rail-car displacement signal and storing the summed signal according to the vertical position of the car in the hoistway. Elevator car horizontal vibrations are actively controlled by retrieving data stored in memory indicative of the out-of-straightness of the guide rails.

Document <CIT> which discloses the preamble of claims <NUM> and <NUM>, presents an elevator apparatus which can adapt to changes in the distance between guide rails. The elevator apparatus is equipped with a car which ascends and descends in an elevator shaft, a pair of guide rails which are provided in the elevator shaft and whose mutual distance changes partially, a car guide device which is provided in the car, can freely move forward and backward to any horizontal position with respect to the car, and constantly abuts against the guide rails by responding to changes in the mutual distance of the guide rails. The elevator apparatus is also equipped with a safety gear device which is provided in the car, can freely move forward and backward to any horizontal position with respect to the car, is constantly opposed to the guide rails with equal spacing therefrom by responding to changes in the mutual distance of the guide rails, and brings the car to an emergency stop by grasping the guide rails during a fall of the car at an overspeed.

An objective of the present invention is to provide a method for determining a degraded guide rail condition in an elevator system, a computer program product, and an elevator system. Another objective of the present invention is that the method, the computer program product, and the elevator system enable detecting a degraded guide rail conditions, such as misaligned guide rail.

The objectives of the invention are reached by a method, a computer program product and an elevator system as defined by the respective independent claims.

According to a first aspect, a method for determining a degraded guide rail condition, such as related to misalignment thereof, in an elevator system is provided.

The elevator system may refer herein to a conventional elevator in which an elevator car is moved in a vertical direction, that is up and down, by a hoisting rope in connection with a hoisting motor. However, the elevator system may alternatively refer to an elevator utilizing an electric linear motor, that is to a ropeless or rope-free elevator, for moving the elevator car in vertical direction or in any direction. Still further, the elevator system may alternatively refer to a conveyor system.

The method according to the first aspect of the invention comprises:.

In various embodiments, the comparison may relate to comparing a first distance in the first data and a second distance in the second data to each other. The distances may have been determined during certain time interval and/or at certain positions of the guide rail or rails. Alternatively or in addition, the comparison relates to comparing a first speed in the first data and a second speed in the second data to each other. The compared speed values may be average speed values or instantaneous speed values.

Alternatively, in some embodiments, the second data may be or may correspond to a movement reference curve of an elevator car.

Yet in another embodiments, the second data may include information about movement of an elevator car, such as relative to a longitudinal direction of a hoistway. Thus, the second data may have been obtained by utilizing a motor encoder in connection with the hoisting motor. The elevator component may, preferably, be coupled to the elevator car.

In various embodiments, the deviation criterion may be at least one percent, or at least five percent, or at least ten percent difference between the first and the second data, or between the characteristics of said data.

Additionally, the first data and the second data may include information about movement during same time instances or intervals.

In some embodiments, the first or the second elevator component, or both, may comprise a guide element arranged to move in contact with the first or the second guide rail, respectively, or at least along a path, a shape of which corresponds to a shape of a guide surface of the first guide rail or the second guide rail. The elevator component may further comprise, or at least be in connection thereto, determining means for determining at least one of the following: a position, a distance travelled, a speed of the first or the second elevator component relative to the first or the second guide rail, respectively. In such cases, the method may comprise determining, by the determining means, at least one of the following: the position, the distance travelled, the speed of the first or the second elevator component relative to the first or the second guide rail, respectively. The first or the second data, or both data, may then be arranged to include the determined information. Optionally, the guide element may be a guide roller, such as of a guide roller shoe.

In some embodiments, the determining means may comprise a rotary encoder, such as in connection with the guide roller. In such cases, the method may comprise determining, by the rotary encoder, at least one of the following: the position, the distance travelled, the speed of the first or the second elevator component relative to the first or the second guide rail, respectively. Still further, the rotary encoder may be a magnetic encoder or an optical encoder or a capacitive encoder, or an inductive encoder, such as arranged to the first or the second elevator component or at least in functional connection thereto.

In various embodiments, the first or the second guide rail, or both, may comprise at least partly along its length position markings or at least one strip of position marks, such as including magnets; and the first or the second elevator component, or both, comprise a reader device for reading the position markings or marks, respectively. In such embodiments, the method may comprise determining, by the reader device, at least one of the following: a position, a distance travelled, a speed of the first or the second elevator component relative to the first or the second guide rail, respectively, wherein the first or the second data is or both data are arranged to include the determined information.

In some embodiments, the method may comprise sending information about the degradation of a guide rail, preferably information about the degree of degradation of the guide rail, to a remote maintenance server. The information may be used for preventive maintenance of elevators (elevator maintenance service may be provided before the progressing degradation causes interruption of elevator operation).

According to a second aspect of the invention, a computer program product, such as stored in a device including a non-volatile or a non-transitory memory storage medium, is provided. The computer program product comprises program instructions which when executed by a control unit cause the elevator system according to the third aspect described hereinbelow to perform the method according to the first aspect.

According to a third aspect of the invention, an elevator system is provided. The elevator system comprises elevator components, including a first elevator component and a second elevator component. The elevator system also comprises guide rails, including a first guide rail and a second guide rail, wherein the elevator components are arranged to move relative to, preferably in a longitudinal direction of, the guide rails. Still further, the elevator system comprises a control unit, such as comprising at least one processor and at least one memory for storing at least one portion of computer program code therein. The control unit configured to:.

In various embodiments, the elevator system may comprise a guide element, such as a guide roller, arranged to move in contact with the first or the second guide rail, or at least along a path, a shape of which corresponds to a shape of a guide surface of the first or the second guide rail. The elevator system may further comprise determining means, such as a magnetic encoder arranged in connection with the guide roller, arranged to determine at least one of the following: a position, a distance travelled, a speed of the first or the second elevator component relative to the first or the second guide rail. Still further, the first or the second data, or both data, may be arranged to include the determined information.

The present invention provides a method, a computer program product and an elevator system. The present invention provides advantages over known solutions in that the condition of a guide rail of an elevator with respect to the alignment of the rail can be detected without expensive monitoring equipment making the solution simple and cost-effective. The present invention can also be implemented to determine the quality of the guide rails.

Various other advantages will become clear to a skilled person based on the following detailed description.

The expression "a number of" may herein refer to any positive integer starting from one (<NUM>).

The expression "a plurality of" may refer to any positive integer starting from two (<NUM>), respectively.

The terms "first", "second" and "third" are herein used to distinguish one element from other element, and not to specially prioritize or order them, if not otherwise explicitly stated.

The exemplary embodiments of the present invention presented herein are not to be interpreted to pose limitations to the applicability of the appended claims. The verb "to comprise" is used herein as an open limitation that does not exclude the existence of also unrecited features.

The novel features which are considered as characteristic of the present invention are set forth in particular in the appended claims. The present invention itself, however, both as to its construction and its method of operation, together with additional objectives and advantages thereof, will be best understood from the following description of specific embodiments when read in connection with the accompanying drawings.

Some embodiments of the invention are illustrated by way of example, and not by way of limitation, in the figures of the accompanying drawings.

<FIG> illustrates schematically a non-claimed elevator system <NUM>. The elevator system <NUM> may comprise a hoistway <NUM>, such as a vertical hoistway <NUM>. Furthermore, the system <NUM> may further comprise an elevator car <NUM> arranged to be moved in the hoistway <NUM>, such as by a hoisting rope <NUM> coupled to a hoisting motor <NUM>. Alternatively or in addition, the elevator car <NUM> may be arranged to be moved by an electric linear motor.

The elevator system <NUM> may further comprise at least one guide rail <NUM>, <NUM>, for example two parallel guide rails <NUM>, <NUM>, and at least one elevator component <NUM>, such as a first elevator component <NUM>. The elevator component <NUM> may, preferably, be arranged to move relative to a guide rail <NUM>, <NUM> and configured to meet the guide rail <NUM>, <NUM> to guide the movement of the elevator car <NUM>. The elevator component <NUM> may, preferably, be arranged to be coupled to the elevator car <NUM>.

The elevator system <NUM> may further comprise a control unit <NUM> for controlling various tasks related to the operation of the elevator system <NUM>. The control unit <NUM> may be a separate device or may be comprised in the other components of the elevator system <NUM>. The control unit <NUM> may be arranged in distributed manner (instead of being a single device) at more than two locations or in more than two devices whereas the elevator system <NUM> may comprise electrical and/or data connections between the control unit <NUM> and various other elements of the elevator system <NUM>, such as the elevator components <NUM>, <NUM> and/or the parts of the determining means, and/or connections between different portions of the control unit <NUM> for enabling controlling the operation of the elevator system <NUM>.

The control unit <NUM> may comprise one or more processors, one or more memories being volatile or non-volatile, or non-transitory, for storing portions of computer program code and any data values and possibly one or more user interface units. The mentioned elements may be communicatively coupled to each other with e.g. an internal bus.

The processor of the control unit <NUM> may be configured to implement at least various tasks of the elevator system <NUM>, such as one or several of the method steps described hereinafter. The implementation of the tasks may be achieved by arranging the processor to execute at least some portion of computer program code stored in the memory causing the processor, and thus the control unit <NUM>, to implement the tasks. The processor may thus be arranged to access the memory and retrieve and store any information therefrom and thereto. For sake of clarity, the processor herein refers to any unit suitable for processing information and control the operation of the control unit <NUM>, among other tasks. The operations may also be implemented with a microcontroller solution with embedded software. Similarly, the memory is not limited to a certain type of memory only, but any memory type suitable for storing the described pieces of information may be applied in the context of the present invention.

In various embodiments, the elevator component <NUM>, such as the first elevator component <NUM>, may comprise a guide element arranged to move in contact with the guide rail <NUM>, <NUM>, or at least along a path, a shape of which corresponds to a shape of a guide surface of the guide rail <NUM>, <NUM>. In an embodiment, the guide element may be a guide roller, such as of a guide roller shoe.

In addition, the elevator system <NUM> may comprise determining means for determining at least one of the following: a position, a distance travelled, a speed of the elevator component <NUM> relative to the guide rail <NUM>, <NUM>.

In some embodiments, the determining means may comprise a rotary encoder, such as in connection with the elevator component <NUM>, for example, with the guide roller. Furthermore, the rotary encoder may be a magnetic encoder, that is comprising at least one magnet, or an optical encoder, or a capacitive encoder.

Alternatively, the guide rail <NUM>, <NUM> may comprise at least partly along its length position markings or at least one strip of position marks, such as including magnets, whereas the elevator component <NUM> may comprise a reader device for reading the position markings or marks, respectively. The reader device may be in contact with the guide rail <NUM>, <NUM>, or may read the position markings or marks from a distance, such as at least one centimeter away from the guide rail <NUM>, <NUM>, or at least two centimeters, or even at least five centimeters distance from the guide rail <NUM>, <NUM>. The reading of the markings or marks by the reader device may be based on magnetic interaction, optical interaction or capacitive interaction between the markings or marks and the reader device. Thus, the reader device may be configured to determining at least one of the following: a position, a distance travelled, a speed of the elevator component <NUM> relative to the guide rail <NUM>, <NUM> based on reading the position markings or marks.

<FIG> illustrates schematically an elevator system <NUM> according to an embodiment of the present invention. The elevator system <NUM> comprises two guide rails <NUM>, <NUM>, such as two parallel guide rails <NUM>, <NUM>, and two elevator components <NUM>, <NUM>, a first elevator component <NUM> and a second elevator component <NUM>. The elevator components <NUM>, <NUM> are arranged to move relative to the guide rails <NUM>, <NUM> and configured to meet the guide rails <NUM>, <NUM>, respectively, to guide the movement of the elevator car <NUM>. The elevator component <NUM> may, preferably, be arranged to be coupled to the elevator car <NUM>. The first <NUM> and the second <NUM> elevator components may, preferably, be arranged to move along different guide rails <NUM>, <NUM>, such as shown in <FIG>.

In some embodiments, the elevator system <NUM> may comprise even further elevator components, such as shown with dashed lines in <FIG>. Thus, there can be, for example, three, four, five, six, or even more elevator components. In various embodiments, the elevator components <NUM>, <NUM>, such as the first elevator component <NUM> and the second elevator component <NUM>, may comprise guide elements arranged to move in contact with the guide rails <NUM>, <NUM>, or at least along a path, a shape of which corresponds to shapes of the guide surfaces of the guide rails <NUM>, <NUM>, respectively. In an embodiment, the guide elements may be guide rollers, such as of guide roller shoes.

In addition, the elevator system <NUM> may comprise determining means for determining at least one of the following: a position, a distance travelled, a speed of the elevator components <NUM>, <NUM> relative to the guide rails <NUM>, <NUM>, that is, one determining means or, preferably, one determining means for each elevator component <NUM>, <NUM>.

<FIG> illustrates schematically an elevator component <NUM> and determining means according to an embodiment of the present invention. In <FIG>, the elevator component <NUM> is a guide roller <NUM>, such as of a guide roller shoe, which is arranged to be in contact and rotate along a surface of the guide rail <NUM>, such as along the guide surface. The guide roller <NUM>, or the guide roller shoe, may be coupled to the elevator car <NUM> by a support element <NUM>. The guide roller <NUM> is arranged to rotate around its axis <NUM>. The determining means in <FIG> comprise a magnet <NUM>, such as a magnet ring, on the guide roller <NUM>, and a magnetic sensing element <NUM>, such as a quadrature sensor, arranged to sense when the magnet <NUM> passes the magnetic sensing element <NUM> when the guide roller <NUM> rotates. Thus, the determining means may be configured to determine at least one of the following: a position, a distance travelled, a speed of the guide roller <NUM>, or the rotation thereof, relative to the guide rail <NUM>.

In an embodiment, the magnetic ring may comprise alternating, evenly spaced north and south poles around its circumference.

In an embodiment, the quadrature sensor may be a Hall sensor, for example. Furthermore, the quadrature sensor may have quadrature output signals in channels A and B for the measurement of magnetic poles of the magnet ring. Furthermore, the quadrature sensor may be configured to detect changes in the magnetic field as the alternating poles of the magnet pass over it.

It is clear to a skilled person that based on the rotation of the guide roller <NUM>, the position, the distance travelled, and/or the speed of the guide roller <NUM>, or the rotation thereof, relative to the guide rail <NUM> may be determined when taking into account the dimensions of the guide roller <NUM> and/or the properties of the determining means.

Alternatively, the determining means may comprise an optical element, such as a hole or a reflecting element, arranged instead of the magnet, or arranged in similar manner, to the guide roller <NUM>. Furthermore, there may be an optical sensing element arranged in similar manner as the magnetic sensing element <NUM> in <FIG> to sense when the optical element passes the optical sensing element when the guide roller <NUM> rotates. Thus, the determining means may be configured to determine at least one of the following: a position, a distance travelled, a speed of the guide roller <NUM>, or the rotation thereof, relative to the guide rail <NUM>.

<FIG> illustrates schematically an elevator component <NUM> and determining means according to an embodiment of the present invention. In <FIG>, the elevator component <NUM>, such as portion of the elevator car <NUM> and/or a support portion <NUM>, comprises a reader device <NUM> based on magnetic interaction, optical interaction or capacitive interaction. The reader device <NUM> may also comprise necessary electronics for processing the signals being read by the sensor of the reader device <NUM>. The reader device <NUM> may, preferably, be comprised in the determining means. Furthermore, the guide rail <NUM>, such as on a surface thereof, may comprise position markings <NUM> or marks <NUM>, such as based on magnets, ferromagnetic material, optical elements, or capacitive or inductive elements; the markings <NUM> or marks <NUM> forming one portion of the determining means. Thus, the determining means may be configured to determine at least one of the following: a position, a distance travelled, a speed of the support portion <NUM> and/or the reader device <NUM> relative to the guide rail <NUM>.

<FIG> illustrates schematically an elevator system <NUM> according to an embodiment of the present invention. In <FIG>, the first or the second data, or at least parts thereof, may be obtained by utilizing the hoisting motor <NUM> of the elevator system <NUM>.

Thus, in some embodiments, one measurement of the movement of an elevator component <NUM> relative to the first guide rail <NUM>, which condition is to be monitored, and another measurement of the movement of the elevator car <NUM> relative to the second guide rail <NUM> in the hoistway <NUM> may be obtained. The movement of the elevator car <NUM> may be determined based on the rotation of the hoisting motor <NUM> (with a motor encoder <NUM>) or, alternatively, from a speed reference curve of elevator car <NUM>, especially during constant speed phase of elevator car travel. The motor encoder <NUM> may, thus, be regarded as an embodiment of the determining means.

<FIG> illustrates schematically a characteristic of the first <NUM> and second <NUM> data according to an example of the present invention. The vertical axis <NUM> represents a position of the elevator component <NUM>, <NUM> or a distance being travelled or moved relative to the guide rail <NUM>, <NUM>. The horizontal axis <NUM> represents time. Thus, as can be seen, the first <NUM> and the second data <NUM> may include information about the movement of the elevator component <NUM>, <NUM> in relation to a guide rail <NUM>, <NUM> in the form of data of the position or the distance as a function of time. Furthermore, <FIG> shows a deviation <NUM> between the sets of first and second data <NUM>, <NUM>, or at least between characteristics determined based on the data <NUM>, <NUM>, for example, the final position/total distance.

As can be seen in <FIG>, the final position or the distance travelled according to the first data <NUM> is greater or longer than the corresponding values based on the second data <NUM>. One example of this can be seen in <FIG> in which the first guide rail <NUM> is bent or buckled whereas the second guide rail <NUM> is essentially straight. Thus, if the position or distance are being determined such as shown in <FIG>, the alignment of the guide rails <NUM>, <NUM> can be monitored.

In <FIG>, the first data <NUM> and the second data <NUM> with respect to the elevator components <NUM>, <NUM> may have been determined substantially simultaneously from the first guide rail <NUM> and the second guide rail <NUM>, respectively.

<FIG> illustrates schematically a characteristic of the first <NUM> and second <NUM> data according to an example of the present invention. The vertical axis <NUM> represents an instantaneous speed of the elevator component <NUM>, <NUM>. The horizontal axis <NUM> represents time. Thus, as can be seen, the first <NUM> and the second data <NUM> may include information about the movement of the elevator component <NUM>, <NUM> in relation to a guide rail <NUM>, <NUM> in the form of data of the speed as a function of time. Furthermore, <FIG> shows a deviation <NUM> between the sets of first and second data <NUM>, <NUM>, or at least between characteristics determined based on the data <NUM>, <NUM>, for example, the speed at some instance of time or an average speed during the total measurement period.

As can be seen in <FIG>, instantaneous speed according to the first data <NUM> at the time instance of the deviation <NUM> is lower than the corresponding value based on the second data <NUM>. Thus, the elevator component <NUM>, <NUM> must move faster when the guide rail <NUM> , <NUM> is bent or buckled because the distance to move is longer. Thus, if the speeds are being determined such as shown in <FIG>, the alignment of the guide rails <NUM>, <NUM> can be monitored.

In <FIG>, the first data <NUM> and the second data <NUM> may have been determined substantially simultaneously from the first guide rail <NUM> and the second guide rail <NUM>, respectively.

Related to both of <FIG>, the portions of the guide rails <NUM>, <NUM> of which the data <NUM>, <NUM> are being determined should be substantially the same, that is, the same distance of both guide rails <NUM>, <NUM> determined simultaneously or at different time instances in order to obtain comparable data. However, the portions of the guide rail or rails <NUM>, <NUM> may be just a part of the total length of the guide rail <NUM>, <NUM>, or even the total length of the guide rail <NUM>, <NUM>.

<FIG> shows a flow diagram of a method according to an embodiment of the present invention. The embodiments of the method may be performed in an elevator system <NUM> as shown in <FIG>, and <FIG>, and described in connection thereto. Furthermore, the elevator component <NUM>, <NUM> and/or the determining means being utilized may be as shown in <FIG>, and described in connection thereto.

Step <NUM> refers to a start-up phase of the method. Suitable equipment and components are obtained, and systems assembled and configured for operation.

Step <NUM> refers to obtaining a first data including information about movement of a first elevator component <NUM>, relative to a first guide rail <NUM>.

Step <NUM> refers to obtaining a second data including information about movement of a second elevator component <NUM>, relative to a second guide rail <NUM>.

As can be seen in <FIG>, steps <NUM> and <NUM> may be performed substantially simultaneously (of a plurality of guide rails) or subsequently (of the same guide rail or of different guide rails) as described hereinbefore with respect to <FIG>.

In an embodiment, the first data <NUM> may include information about the movement of a first elevator component <NUM> relative to a first guide rail <NUM>, and the second data <NUM> may include information about the movement of a second elevator component <NUM> relative to a second guide rail <NUM>. Additionally, the first data <NUM> and the second data <NUM> may include information about movement during same time instances or intervals.

In a non-claimed example, the first data <NUM> may include information about the movement of a first elevator component <NUM> relative to a first guide rail <NUM> during a first time interval, and the second data <NUM> may include information about the movement of the first elevator component <NUM> relative to the first guide rail <NUM> during a second time interval.

In some embodiments, the elevator component <NUM>, <NUM>, such as the first <NUM> and/or the second elevator component <NUM>, may comprise a guide element arranged to move in contact with the guide rail <NUM>, <NUM>, or at least along a path, a shape of which corresponds to a shape of a guide surface of the guide rail <NUM>, <NUM>. The elevator component <NUM>, <NUM> may further comprise, or at least be in connection thereto, determining means for determining at least one of the following: a position, a distance travelled, a speed of the elevator component relative to the guide rail. In such cases, the method may comprise determining, by the determining means, at least one of the following: the position, the distance travelled, the speed of the elevator component <NUM>, <NUM> relative to the guide rail <NUM>, <NUM>. The first <NUM> and/or the second data <NUM> may then be arranged to include the determined information. Optionally, the guide element may be a guide roller, such as of a guide roller shoe.

In some embodiments, the determining means may comprise a rotary encoder, such as in connection with the guide roller <NUM>. In such cases, the method may comprise determining, by the rotary encoder, at least one of the following: the position, the distance travelled, the speed of the elevator component relative to the guide rail. Still further, the rotary encoder may be a magnetic encoder or an optical encoder or a capacitive encoder, or an inductive encoder, such as arranged to the elevator component <NUM>, <NUM> or at least in functional connection thereto.

In various embodiments, the guide rail <NUM>, <NUM> may comprise at least partly along its length position markings <NUM> or at least one strip of position marks <NUM>, such as including magnets; and the elevator component <NUM>, <NUM>, such as the first <NUM> and/or the second elevator component <NUM>, may comprise a reader device <NUM> for reading the position markings <NUM> or marks <NUM>, respectively. In such embodiments, the method may comprise determining, by the reader device <NUM>, at least one of the following: a position, a distance travelled, a speed of the elevator component relative <NUM>, <NUM> to the guide rail <NUM>, <NUM>, wherein the first <NUM> and/or the second data <NUM> may be arranged to include the determined information.

Alternatively, in some embodiments, the second data <NUM> may be or may correspond to a movement reference curve of an elevator car <NUM>.

Yet in another embodiments, the second data <NUM> may include information about movement of an elevator car <NUM>, such as relative to a longitudinal direction of a hoistway <NUM>. Thus, the second data <NUM> may have been obtained by utilizing a motor encoder <NUM> in connection with the hoisting motor <NUM>. The elevator component may, preferably, be coupled to the elevator car <NUM>.

Step <NUM> refers to comparing the first data and the second data, or characteristics based on said data to each other. The comparison may be performed, for example, based on what is shown in <FIG>, and described in connection thereto. For example, the comparison may be done by comparing the final position or total distance travelled. Alternatively, the comparison may be based on comparing instantaneous or average speeds defined based on the data <NUM>, <NUM>.

Step <NUM> refers to detecting, based on the comparison, a deviation fulfilling a deviation criterion. In some embodiments, the deviation criterion may be at least one percent, or at least five percent, or at least ten percent difference between the first <NUM> and the second data <NUM>, or between the characteristics of said data <NUM>, <NUM>, such as between the final positions, the total distance, instantaneous speeds, or average speeds.

Thus, in various embodiments, the method may comprise determining, by the determining means, at least one of the following: the position, the distance travelled, the speed of the elevator component relative to the guide rail, wherein the first <NUM> and/or the second data <NUM> is arranged to include the determined information.

As can be seen in <FIG>, if the deviation <NUM> does not fulfill the deviation criteria, performing the method may, for example, be ended, or a new set of second data <NUM> may be obtained for performing a new comparison.

Step <NUM> refers to creating a signal indicating the degraded, such as misaligned, guide rail condition, such as of the first or the second guide rail. The signal may be created or generated in the control unit <NUM>, for instance, and then provided to the operator by means of an alert or report. The information of the degraded condition may be sent to a service center via a remote link, such that guide rail maintenance can be added to a future maintenance schedule.

In some embodiments, the method may comprise sending information about the degradation of a guide rail, that is related to said created signal, preferably information about the degree of degradation of the guide rail, to a remote maintenance server. The information may be used for preventive maintenance of elevators (elevator maintenance service may be provided before the progressing degradation causes interruption of elevator operation).

Method execution is ended at step <NUM>. The method may be performed once, intermittently, periodically, continuously or, on demand.

Claim 1:
A method for determining a degraded guide rail condition, such as related to misalignment thereof, in an elevator system (<NUM>), wherein the method comprises:
- obtaining (<NUM>) a first data (<NUM>) including information about movement of a first elevator component (<NUM>) relative to a first guide rail (<NUM>);
- obtaining (<NUM>) a second data (<NUM>) including information about movement of a second elevator component (<NUM>, <NUM>) relative to a second guide rail (<NUM>);
characterized in that the method comprises:
- comparing (<NUM>) the first data (<NUM>) and the second data (<NUM>), or characteristics based on said data (<NUM>, <NUM>) to each other;
- detecting (<NUM>), based on the comparison, a deviation (<NUM>) fulfilling a deviation criterion; and, subsequently,
- creating (<NUM>) a signal indicating the degraded, such as misaligned, guide rail condition, such as of the first or the second guide rail (<NUM>, <NUM>).