BACKGROUND OF THE INVENTION

FIELD OF THE INVENTION

[0001] This invention relates to a solution for monitoring an elevator, and in particular to a solution improving maintenance work of an elevator.

DESCRIPTION OF PRIOR ART

[0002] A problem with elevators is that during use wear occurs to the different components of the elevator or the surrounding building. An elevator which has operated perfectly after installation or after maintenance work, may not operate as perfectly when some time has passed from the installation or maintenance work.

[0003] In order to evaluate how well the elevator operates, in other words the ride quality, regular maintenance inspections are needed. However, all potential problems may not be detected during a maintenance inspection.

[0004] In case a potential problem develops before the next maintenance inspection, the ride quality may deteriorate and users of the elevator may notice this problem before the maintenance personal.

SUMMARY OF THE INVENTION

[0005] An object of the present invention is to solve the above-mentioned drawback and to provide solution improving the ride quality of an elevator in such a way that maintenance personnel can detect problems more easily and rapidly. This object is achieved with a method according to independent claim 1 and with an elevator system according to intendent claim 11 .

[0006] When travel parameter data is obtained during an elevator run and this obtained travel parameter data is analyzed to generate a quality performance indicator, a maintenance need for the elevator can be determined based on the quality performance indicator.

[0007] Preferred embodiments of the invention are disclosed in the dependent claims. BRIEF DESCRIPTION OF DRAWINGS

[0008] In the following the present invention will be described in closer detail by way of example and with reference to the attached drawings, in which [0009] Figure 1 is a block diagram of an elevator system,

[0010] Figure 2 is a flow diagram of a method for monitoring an elevator,

[0011] Figures 3a and 3b illustrate comparison of travel parameter data with a target profile during a start phase,

[0012] Figure 4 illustrates a constant speed phase, and

[0013] Figure 5 illustrates comparison of travel parameter data with a target profile during a stopping phase.

DESCRIPTION OF AT LEAST ONE EMBODIMENT

[0014] Figure 1 is a block diagram of an elevator system 1. The elevator system comprises an elevator car 2 and a counterweight 3 which are moved in an elevator hoistway 12 by a hoisting machine 4 including an electric motor 5. An elevator control 6 with a motor drive 7, such as a frequency converter, supplies electricity to the electric motor 5 of the hoisting machine 4 to control the operation of the elevator car 2 while the elevator car moves between landings 28 of a building, for instance.

[0015] A challenge with an elevator system 1 is that during use wear occurs to the different components of the elevator or the surrounding building. An elevator which has operated perfectly after installation or after maintenance work, may not operate as perfectly when some time has passed from the installation or maintenance work.

[0016] In praxis there are several different parts in the elevator system which may cause problems over time, due to which the ride quality of the elevator system may be affected. Examples of such problems include:

[0017] - Start accuracy problems. If a Load Weighting device (LWD) of the elevator system is not perfectly calibrated, the measured load may be different from the real load, due to which the elevator car may "roll-forward" or "roll-back" during the start phase when the brakes are released, causing a start of the elevator ride which is not smooth.

[0018] - Constant speed problems. Problems in the shaft (such as tight spots in the guide rails or inadequate lubrication of the guide rails) may cause sudden changes in the speed due to quickly changed friction in the guide rails, for instance, during the phase of the elevator ride where the speed should remain constant. Due to this the ride is not smooth.

[0019] - Stopping problems. If the position measurement fail for some reasons, the stopping of the elevator car is not as quick, smooth and precise as it should be. Due to this the passengers may notice that the stopping sequence may take longer time than ideally or the elevator may even stop at a height in the hoistway which differs from the height of the landing.

[0020] In the illustrated example of Figure 1 , the elevator system is provided with a sensor device 8, 8' providing travel parameter data, such as measured elevator position, speed, acceleration, during the elevator runs. By way of example Figure 1 illustrates two different sensor devices 8 and 8'. These devices are both capable of monitoring the movement of the elevator car, and they are alternatives to each other. In praxis only one of the illustrated sensor devices is needed in each elevator car installation.

[0021] The first alternative is to implement the sensor device 8 with a motor encoder mounted on a rotation axis of the hoisting machine 4. In Figure 1 it is by way of example assumed that the sensor device 8 is arranged in the electric motor 5 of the hoisting machine 4 from where it can provide travel parameter data to a monitoring unit 9 located in the elevator control 6, for instance. The monitoring unit 9 may be a part of the motor drive 7, though Figure 1 indicates that it may be separate from the motor drive 7. In some implementations it is also possible that the monitoring unit 9 is located in a remotely located monitoring center 10. In praxis the monitoring unit 9 may be implemented as software stored in a memory and run by a processor.

[0022] The second alternative is to implement the sensor device 8' with an acceleration sensor. In Figure 1 such a sensor device 8' is by way of example attached to a roof of the elevator car 2. In that case the sensor device may via a wired or wireless connection transmit travel parameter data to the monitoring unit 9 in the elevator control 6. Alternatively, as also illustrated in Figure 1 , the sensor device 8' and the monitoring unit 9' may be integrated as one single module to the elevator car 2, in which case this module may generate the quality performance indicator directly at the elevator car. In that case the quality performance indicator may be transmitted directly from the monitoring unit 9' to the monitoring center 10. This makes it possible to easily retrofit an old elevator with such a module in order to facilitate monitoring of the elevator in question. [0023] The monitoring unit 9, 9' analyzes the obtained travel parameter data to generate a quality performance indicator based on the obtained travel parameter data. One alternative to carry out this analyzing is that the monitoring unit directly obtains (by calculating, for instance) a numerical value from the travel parameter data and includes this value into the quality performance indicator. Alternatively, the monitoring unit may carry out the analyzing by comparing travel parameter data with a target profile and generate a quality performance indicator based on a difference between the obtained travel parameter data and the target profile. Irrespectively of how the analyzing is carried out, this quality performance indicator is provided to a monitoring center 10. Alternatively, it is possible that the monitoring unit is located at the monitoring center, in which case the travel parameter data is provided to the monitoring center where the monitoring unit carries out the comparison and generation of the quality performance indicator.

[0024] In some implementations the monitoring center can be implemented at the elevator installation site 11 , in which case it may be a part of the elevator control 6. However, in Figure 1 it is by way of example assumed that the monitoring center 10 is remotely located from the installation site 11 of the elevator car, in which case the monitoring unit 9, 9' transmits the quality performance indicator via a communication system 13 by utilizing a wired or wireless connection. In some implementations it is also possible that use of a communication system is not needed, in which case the quality performance indicator is transmitted directly from the monitoring unit to the remotely located monitoring center.

[0025] The monitoring center 10 may in praxis be implemented as a cloud service provided by a server for instance, which is used to monitor the performance of several elevator installations over a large geographical area, for instance. Quality performance indicators obtained from elevator cars 2 at different installation sites 11 are maintained in a memory of the monitoring unit 10 available for access by service personnel handling the maintenance work of the different elevators via mobile terminals 14, for instance. This memory may for each elevator car contain a statistics about obtained quality performance indicators over a longer time period, which makes it possible to compare recently obtained quality performance indicators to older ones.

[0026] In case one of the monitored elevator cars 2 has a quality performance indicator suggesting a need of maintenance, this elevator car and quality performance indicator may be emphasized to provide an indication of a maintenance need on a user interface of a mobile terminal 14, for instance, when service personnel accesses the monitoring unit during routine tasks. Alternatively, the monitoring center 10 can provide an indication of a maintenance need for the elevator car 2 in question or a maintenance schedule for the car 2, for example by transmitting a message to a mobile terminal 14 of a person who is in charge of that specific elevator car 2.

[0027] Depending on the implementation, the monitoring unit 9, 9' may be configured to analyze travel parameter data separately for different phases of an elevator run. Possible phases may in that case include one or more of the following: start phase, constant speed phase and stop phase. For each phase a separate phase indicator may be included in the quality performance indicator. Consequently, service personnel obtaining an indication of a maintenance need via the monitoring center 10, simultaneously obtain information about in which phase of the elevator run a problem exits. This simplifies and speeds up the maintenance work.

[0028] Figure 2 is a flow diagram of a method for monitoring an elevator. The illustrated method may be implemented for the elevator system illustrated in Figure 1 , for instance.

[0029] In step A an analyzing solution for the elevator run is defined. A first alternative is that the monitoring unit directly obtains (by calculating, for instance) a numerical value from the travel parameter data and includes this value into the quality performance indicator. A second alternative is that the monitoring unit carries out the analyzing by comparing travel parameter data with a target profile and generates a quality performance indicator based on a difference between the obtained travel parameter data and the target profile. It is also possible the above mentioned first and second alternatives are both selected simultaneously for use in the defined analyzing solution. It that case the start and stop phase may be analyzed by utilizing the second alternative, while the first alternative is used to analyze the constant speed phase of the elevator run.

[0030] When the second alternative is implemented, a target profile is defined. This target profile, which may include data for different phases of an elevator run, such as for a start phase, a constant speed phase and stop phase, is defined in such a way, that in case the elevator runs during subsequent use with passengers are according to the target profile, the ride quality provided by the elevator in question is acceptable.

[0031] A first alternative to define the target profile is to define the target profile for the elevator as a factory default target profile. In that case, each and every elevator of a same type which is manufactured, and provided with the same default control parameters, may during manufacturing or commissioning obtain the same target profile which has been determined appropriate for this type of elevator. Consequently, the defining may include calculating the target profile from said default control parameters or storing the target profile into a memory of a monitoring unit 9, 9.

[0032] A second alternative is to utilize a test run instead of a factory default. In that case one alternative is to carry out one or more elevator test runs with the elevator car 2 in question, and to obtain travel parameter data with a sensor device 8, 8' during each test run. The test runs are carried out with the elevator in such a condition, that each test run results in a ride quality which is on an acceptable level. Subsequently, the travel parameter data is analyzed, and a target profile is generated based on the analysis. In this way the elevator in question will obtain an individual elevator specific target profile, which is stored in a memory of a monitoring unit 9, 9. Test run may be a normal elevator run used for establishing a target profile to which subsequent elevator runs are compared.

[0033] In step B travel parameter data is obtained with a sensor device 8, 8' during daily use of the elevator. This step of obtaining travel parameter data may be repeated during each elevator run with or without passengers of the elevator car, or alternatively only for some elevator runs selected randomly or preformed with predetermined intervals, for instance.

[0034] In step C, the obtained travel profile data is analyzed by the monitoring unit 9, 9' to the target profile, for instance, to generate a quality performance indicator based on a difference between obtained travel parameter data and the target profile. The comparison may be carried out separately for the different phases of the elevator run, such as during start, constant speed and stop. Ongoing elevator run phase may be deduced from the target profile. Based on the comparison a quality performance indicator is generated to indicate how well (or poorly) the travel parameter data corresponds to the target profile. In case the comparison is done separately for the different phases of the elevator run, a phase indicator may be included in the quality performance indicator separately for each phase.

[0035] In step D a maintenance need is determined based on the quality performance indicator. Depending on the implementation this may involve manual comparison of quality performance indicators obtained for an elevator car during different time periods, or alternatively, a monitoring center 10 with a server may be programmed to automatically carry out the comparison and to indicate a maintenance need when a predetermined criterion is fulfilled. The predetermined criterion may be fulfilled immediately when a quality performance indicator out of a predefined range is detected for an elevator car. Alternatively, the predetermined criterion may be fulfilled when statistical processing of quality performance indicators reveals that a specific elevator car has for a longer time period had a quality performance indicator out of range or the statistical processing indicates that the trend of the changes for the quality performance indicator is such that the criterion is fulfilled.

[0036] Figures 3a and 3b illustrate comparison of a target profile and travel parameter data during a start phase of an elevator run for an elevator car 2. Such a solution may be utilized in the elevator system of Figure 1 or in the method of Figure 2.

[0037] The dotted line illustrates the target profile 15, in other words how the position P of the elevator car 2 should change (vertical axis) at different moments of time T (horizontal axis) after start, while the continuous line illustrates the obtained travel parameter data 16 after the brakes have been opened and the weight of the elevator car 2 is carried by the hoisting machine 4 with the electric motor 5.

[0038] In Figure 3a drifting can be seen in the form of a positive (moved too much upwards) roll-forward, as the elevator car 2 has drifted upwards more than intended as compared to the target profile 15.

[0039] In Figure 3B, which illustrates another elevator run than Figure 3A, a negative (moved too much downwards) roll-back can be seen, as the elevator car 2 has drifted downwards more than intended, as compared to the target profile 15.

[0040] The phase indicator of the quality performance indicator can be generated to indicate the start accuracy of the elevator car 2, as the maximum deviation in position during the start sequence. The start phase indicator can have a positive or negative sign to separate cases where the elevator car jumps up or drops down during the starting.

[0041] Maintenance personnel can from on the start phase indicator of the quality performance indicator get information about how well the Load Weighing Device of the elevator car works. If the Load Weighting Device has not been properly calibrated with test masses, or if there is a failure mode, the measured load of the elevator car is different from the real load, which may affect the ride quality during the start phase. Statistical analysis, for instance, makes it possible to detect a problem like this at an early stage.

[0042] Figure 4 illustrates speed during a constant speed phase. A phase indicator included in the quality performance indicator can be generated for the constant speed phase in the elevator system of Figure 1 or method of Figure 2, as follows.

[0043] During the time (T, horizontal axis [sec]) of the constant speed phase 17, the actual speed 21 (S, right vertical axis [m/sec]) of the elevator car 2 while traveling between different positions 20 (P, left vertical axis [m]) in the elevator hoistway 12 should vary as little as possible.

[0044] Quality of the constant speed phase may bee included as a phase indicator in the quality performance indicator, which expresses the speed deviation, as:

[0045] Speed deviation = max ( | speed | ) - min ( | speed | ),

[0046] in other words, as the difference between a maximum speed (such as an absolute value) and a minimum speed (such as an absolute value) of the elevator car during the constant speed phase 17.

[0047] Maintenance personnel can from the constant speed indicator of the quality performance indicator get information possible problems in guide rails (poor lubrication or tight spot) or motion controller parameterization (e.g. somebody has tuned wrongly speed controller gain which affects ride comfort). Statistical analysis, for instance, makes it possible to detect a problem like this at an early stage.

[0048] Figure 5 illustrates comparison of a target profile 15 and travel parameter data 21 during stopping of an elevator 2 run. Such a solution may be utilized in the elevator system of Figure 1 or in the method of Figure 2.

[0049] In Figure 5 the target profile 15, in this case representing the speed during an elevator run, is illustrated as a thick dotted line. In this Figure 5, the stopping phase occurs during time period dT, which is the part of the elevator run analyzed to determine a stopping quality. Acceleration of the elevator car is illustrated with line 18 (A, left vertical axis [m/s ² ]), jerks [m/s ³ ] possibly detectable by a passenger are illustrated with line 19, the position of the elevator car 2 with line 20 (P, left vertical axis [m]) and the actual speed of the elevator car at the end of the elevator run with line 21 .

[0050] From the moment of time illustrated as 4.5 on the horizontal axis T, the last jerk begins. From this moment until the brakes close command is given and the elevator car 2 comes to a final stop, consequently during time period dT, it can be seen from Figure 5 that the actual speed of the elevator, in other words the travel parameter data 21 , deviates from the intended speed, in other words the target profile 15.

[0051] The stopping quality SQ is obtained by analyzing a difference of the actual change of speed and a reference change of speed for the elevator car, which may be implemented by calculating an integral of absolute differences between the speed reference and actual speed:

[0052] during a time period beginning at a last jerk and ending when closing of brakes is initiated. This stopping quality can be included as a stopping phase indicator in the quality performance indicator. Maintenance personnel can from the stopping phase indicator of the quality performance indicator get information possible problems in position measurement or magnets at landings, for instance. Statistical analysis, for instance, makes it possible to detect a problem like this at an early stage.

[0053] In addition, or as an alternative, the stopping phase indicator may also be determined as a position difference between a position where the elevator car 2 has actually stopped in the hoistway and a desired stopping position at a landing 28 of the hoistway 12.

[0054] It is to be understood that the above description and the accompanying figures are only intended to illustrate the present invention. It will be obvious to a person skilled in the art that the invention can be varied and modified without departing from the scope of the invention.