Calibration of a load weighing device of an elevator

Abstract

A method for calibrating a load weighing device (110) of an elevator is provided, wherein: performing (310) a motion control operation for the elevator for determining a balance load of the elevator; performing (320) a zero load calibration to of the load weighing device (110) by setting an output to correspond to a zero load of the elevator; performing a non-zero load point calibration of the load weighing device (110), the non-zero load point calibration comprises: receiving (330) data indicative of a locking of an elevator car (120) in a position in an elevator shaft; receiving (340) data indicative of that a traction sheave (190) of the elevator is free-to-rotate; setting (350) an output signal of the load weighing device (110) to correspond to the balance load. Also a computing apparatus, a computer program and an elevator are provided to.

Description

[0001] CALIBRATION OF A LOAD WEIGHING DEVICE OF AN ELEVATOR

[0002] TECHNICAL FIELD

[0003] The invention concerns in general the technical field of elevators. More particularly, the invention concerns a commissioning of a load weighing device in the elevator.

[0004] BACKGROUND

[0005] Information on a load of an elevator car is needed to perform control operations at least in relation to a motion of the elevator car. In order to determine the load of the elevator car various approaches have been introduced. In some commonly applied approaches the load of the elevator car is obtained with one or more load sensors that are configured to measure a tension of an elevator rope either directly or indirectly. In some other commonly applied approaches load sensor(s) are positioned between an elevator car and a sling into which the elevator car is mounted to. In the latter case the load sensor(s) are configured to directly measure the load in the car.

[0006] The commissioning of the load weighing device is traditionally performed by using so-called test weights having known weights. Those are loaded in the elevator car to make the elevator system balanced and in such a situation the load weighing device is calibrated for use. The approach with the test weights is operable as such but the handling of the weights is laborious and time consuming. Furthermore, the methods based on an operation of a technician are open to human errors thus causing a permanent deviation in the measurement of the load weighing device calibrated in an erroneous manner.

[0007] In a more sophisticated approach the calibration of the load weighing device is conducted by measuring the tension of the elevator rope wherein the calibration is implemented without the test weights. However, these approaches are inaccurate due to that the operational parameters of the elevator are input in the elevator system by the technician but these do not necessarily correspond to the real values of the elevator system in question. In other words, an impact of an installation of the elevator, an impact of a quality of material used in the elevator and further impacts of random root causes are present in the calibration and that cause inaccuracy in the operation of the load weighing device.

[0008] Due to drawbacks of the prior art solutions there is room for introducing improved approaches for the calibration of the load weighing device in order to generate more accurate data.

[0009] SUMMARY

[0010] The following presents a simplified summary in order to provide basic understanding of some aspects of various invention embodiments. The summary is not an extensive overview of the invention. It is neither intended to identify key or critical elements of the invention nor to delineate the scope of the invention. The following summary merely presents some concepts of the invention in a simplified form as a prelude to a more detailed description of exemplifying embodiments of the invention.

[0011] An object of the invention is to present a method, a computing apparatus, a computer program and an elevator for calibrating a load weighing device.

[0012] The objects of the invention are reached by a method, a computing apparatus, a computer program and an elevator as defined by the respective independent claims.

[0013] According to a first aspect, a method for calibrating a load weighing device of an elevator is provided, the method, performed by a computing apparatus, comprises: performing a motion control operation for the elevator for determining a balance load of the elevator, performing a zero load calibration of the load weighing device, the zero load calibration is performed with respect to an elevator car of the elevator without a load in the elevator car by setting an output of the load weighing device to correspond to a zero load of the elevator, the method further comprises: performing a non-zero load point calibration of the load weighing device, the non-zero load point calibration comprises: receiving data indicative of a locking of an elevator car of the elevator in a position in an elevator shaft, receiving data indicative of that a traction sheave of the elevator is set free- to-rotate in response to the locking of the elevator car, setting an output signal of the load weighing device to correspond to the balance load of the elevator determined by performing the motion control operation for the elevator.

[0014] The motion control operation may comprise: generating a control signal to cause the elevator to drive at least one elevator test run, preferably comprising at least one back and forth run between bottom and top floors.

[0015] A torque of an electric motor of the elevator may be determined during the motion control operation.

[0016] Further, the motion control operation may comprise: setting an output of the load weighing device to correspond to a zero load during the motion control operation.

[0017] The motion control operation may also comprise: determining a balance parameter, determining computationally the balance load with the balance parameter.

[0018] The motion control operation may also comprise: determining computationally the balance load based at least on torque data of an electric motor of the elevator, the torque data determined through the at least one elevator test run.

[0019] The balance parameter may be determined by means of the balance load determined computationally based at least on the torque data of the electric motor of the elevator.

[0020] Still further, the determination of the balance parameter may comprise: adjusting the balance parameter with a correction factor wherein the correction factor compensates at least in part a friction in a roping solution of the elevator.

[0021] A detection that the elevator car is without load when performing the zero load calibration may be based on at least one of the following: data received from a sensor system, a signal received from a control entity of the elevator.

[0022] On the other hand, the zero-load calibration of the load weighing device may be performed by: setting an output of the load weighing device to filter out a weight of at least an elevator rope by determining the weight of at least the elevator rope in at least two positions of an elevator car in an elevator shaft.

[0023] A detection of the locking of the elevator car may be based on at least one of the following: a receipt of an acknowledgement of a generation of a control signal to lock the elevator car; a signal received from a control entity of the elevator; a test result controlled by the computing apparatus.

[0024] Still further, the data indicative of that the traction sheave of the elevator is free- to-rotate may be based on at least one of the following: a detection of a release of machinery brakes; a detection that a generation of a torque by the electric motor of the elevator is canceled; a detection of a motion from an encoder of the electric motor; a detection of a motion with a position determination system; a signal received from a control entity of the elevator.

[0025] According to a second aspect, a computing apparatus for calibrating a load weighing device of an elevator is provided, the computing apparatus is configured to: perform a motion control operation for the elevator for determining a balance load of the elevator, perform a zero load calibration of the load weighing device, the zero load calibration is performed with respect to an elevator car of the elevator without a load in the elevator car by setting an output of the load weighing device to correspond to a zero load of the elevator, the computing apparatus is further configured to: perform a non-zero load point calibration of the load weighing device, wherein the non-zero load point calibration the computing apparatus is configured to: receive data indicative of a locking of an elevator car of the elevator in a position in an elevator shaft, receive data indicative of that a traction sheave of the elevator is set free- to-rotate in response to the locking of the elevator car, set an output signal of the load weighing device to correspond to the balance load of the elevator determined by performing the motion control operation for the elevator.

[0026] The computing apparatus may be configured to perform at least part of the motion control operation by: generating a control signal to cause the elevator to drive at least one elevator test run, preferably comprising at least one back and forth run between bottom and top floors. Further, the computing apparatus may be configured to determine a torque of an electric motor of the elevator during the motion control operation.

[0027] The computing apparatus may also be configured to perform at least part of the motion control operation by: setting an output of the load weighing device to correspond to a zero load during the motion control operation.

[0028] The computing apparatus may be configured to perform at least part of by: determining a balance parameter, determining computationally the balance load with the balance parameter.

[0029] The computing apparatus may also be configured to perform at least part of by the motion control operation by: determining computationally the balance load based at least on torque data of an electric motor of the elevator, the torque data determined through the at least one elevator test run.

[0030] For example, the computing apparatus may be configured to determine the balance parameter by means of the balance load determined computationally based at least on the torque data of the electric motor of the elevator.

[0031] The computing apparatus may be configured to perform the determination of the balance parameter at least by: adjusting the balance parameter with a correction factor wherein the correction factor compensates at least in part a friction in a roping solution of the elevator.

[0032] Moreover, the computing apparatus may be configured to perform a detection that the elevator car is without load when performing the zero load calibration on a basis of at least one of the following: data received from a sensor system, a signal received from a control entity of the elevator. The computing apparatus may also be configured to perform the zero-load calibration of the load weighing device by: setting an output of the load weighing device to filter out a weight of at least an elevator rope by determining the weight of at least the elevator rope in at least two positions of an elevator car in an elevator shaft.

[0033] Still further, the computing apparatus may be configured to perform a detection of the locking of the elevator car on a basis of at least one of the following: a receipt of an acknowledgement of a generation of a control signal to lock the elevator car; a signal received from a control entity of the elevator; a test result controlled by the computing apparatus.

[0034] Also, the computing apparatus may be configured to use, as the data indicative of that the traction sheave of the elevator is free to rotate, at least one of the following: a detection of a release of machinery brakes; a detection that a generation of a torque by the electric motor of the elevator is canceled; a detection of a motion from an encoder of the electric motor; a detection of a motion with a position determination system; a signal received from a control entity of the elevator.

[0035] For example, the computing apparatus may be an elevator controller configured to receive measurement data from a load sensor.

[0036] According to a third aspect, a computer program is provided, the computer program comprising instructions to cause the computing apparatus according to the second aspect as defined above to execute the steps of the method according to the first aspect as defined above.

[0037] According to a fourth aspect, an elevator is provided, the elevator comprising: an elevator car, an electric motor configured to move the elevator car, a blocking device configured to lock the elevator car, and a computing apparatus according to the second aspect as defined above.

[0038] The expression "a number of” refers herein to any positive integer starting from one, e.g. to one, two, or three.

[0039] The expression "a plurality of” refers herein to any positive integer starting from two, e.g. to two, three, or four.

[0040] Various exemplifying and non-limiting embodiments of the invention both as to constructions and to methods of operation, together with additional objects and advantages thereof, will be best understood from the following description of specific exemplifying and non-limiting embodiments when read in connection with the accompanying drawings.

[0041] The verbs “to comprise” and “to include” are used in this document as open limitations that neither exclude nor require the existence of unrecited features. The features recited in dependent claims are mutually freely combinable unless otherwise explicitly stated. Furthermore, it is to be understood that the use of “a” or “an”, i.e. a singular form, throughout this document does not exclude a plurality.

[0042] BRIEF DESCRIPTION OF FIGURES

[0043] The embodiments of the invention are illustrated by way of example, and not by way of limitation, in the figures of the accompanying drawings.

[0044] Figure 1 illustrates schematically a portion of an elevator according to a first example.

[0045] Figure 2 illustrates schematically a portion of an elevator according to another example.

[0046] Figure 3 illustrates schematically a method according to an example.

[0047] Figure 4 illustrates schematically a computing apparatus according to an example. DESCRIPTION OF THE EXEMPLIFYING EMBODIMENTS

[0048] The specific examples provided in the description given below should not be construed as limiting the scope and / or the applicability of the appended claims. Lists and groups of examples provided in the description given below are not exhaustive unless otherwise explicitly stated.

[0049] Figure 1 illustrates a portion of an elevator in order to describe at least some aspects of the present invention for calibrating a load weighing device 1 10 that is configured to determine a load of an elevator car 120 on a basis of a tension of an elevator rope 130 either directly or indirectly. The implementation according to Figure 1 is based on a measurement of the tension of the elevator rope 130 directly with the load sensor that is configured to generate data indicative of a strain of the elevator rope 130 in accordance with the load in the elevator car 120. A non-limiting example of an applicable load sensor may be a strain gauge coupled to the elevator rope 130. Hence, the load weighing device 1 10 comprises the applied sensor but also other necessary electronics to generate data indicative of the load in the elevator car 120. Even if the load weighing device 1 10 as a whole is shown in the enclosed figures to reside in the various measurement locations, it may be arranged that the applied load sensor is positioned in the respective measurement position(s), but the electronics, i.e. an electric circuit receives the measurement result from the load sensor over an applied communication channel, such as over a wired or wireless communication channel. In one advantageous implementation of the invention the load weighing device 1 10 may be implemented so that the load sensor is positioned in a measurement location, cf. e.g. the description of an applicable location in the context of the description of Figure 1 and Figure 2, and the measurement data is conveyed to the electronics unit that is implemented and integrated in the elevator controller. In other words, the elevator controller may be provided with necessary means, such as hardware and software, to perform the method to calibration the operation of the load weighing device 110 and also operate as a part of the load weighing device as is described herein. Moreover, for describing the at least some aspects of the invention the elevator may be implemented so that the elevator car 120 is arranged to travel along a number of guide rails 140. The elevator comprises an arrangement by means of which the elevator car 120 may be locked to a position in an elevator shaft wherein the arrangement may be blocking device 150 by means of which the elevator car 120 may be locked in terms of motion e.g. with respect to the number of guide rails 140 as schematically illustrated in Figure 1. The locking with the blocking device 150 may also be arranged with respect to another entity than the guide rails 140, such as with respect to the elevator shaft e.g. with an arrangement mounted to a wall of the elevator shaft. The blocking device 150 may be mounted to a sling of the elevator car 120 in case the sling approach is applied to. The term blocking device 150 shall be understood also to cover safety gear that is a device which prevents free fall and excessive speed of the elevator car 120 in the downward direction, but also prevents overspeed in the upward direction. Hence, such safety gear may be applied as the blocking device 150 for the purpose of the present invention as is described in the forthcoming invention. Also in case the elevator car is provided with a parking brake it may be used as the blocking device 150 for the purpose of implementing the present invention. Generally speaking, an applicable blocking device 150 is a device that may prevent a motion of the elevator car 120 in at least one predefined direction as is described later. The elevator in accordance with the illustration of Figure 1 also comprises a counterweight that resides on the other side of a traction sheave 190 over which the elevator rope 130 is arranged to travel. A motion of the traction sheave 190 is arranged with an elevator motor 170 in a known manner by controlling the operation of the elevator motor 170 with a drive system in accordance with control signals received from an elevator controller. Furthermore, the elevator comprises a number of machinery brakes 180 that are used to hold the elevator car stationary e.g. at landings. In addition to the above- mentioned entities the elevator rope 130 may be arranged to travel over a number of pulleys (denoted with P in Figure 1 ), such as sling pulleys / elevator car pulleys, counterweight pulleys, diverter pulleys etc. in order to establish the roping system as desired. With the number of applied pulleys it is possible to adjust a rope reeving ratio in a manner as selected for the elevator in question. Figure 2 illustrates a portion of an elevator according to another embodiment for describing at least some aspects of the present invention for calibrating a load weighing device 1 10 that is configured to generated data indicative of a load of an elevator car 120 on a basis of a tension of an elevator rope 130 either directly or indirectly. In the embodiment schematically illustrated in Figure 2 the load weighing device 1 10 comprising the number of load sensors are arranged between a fixed structure 210 and a mounting structure 220, such as a bedplate, of the electric motor 170 and the traction sheave 190 wherein the mounting structure 220 is arranged as a floating structure. The floating structure refers to an arrangement in which the mounting structure 220, and thus the electric motor 170 and the traction sheave 190 are arranged to float, i.e. to move at least vertically, with respect to the fixed structure 210. The movement may occur in response to a change in the load of the elevator car 120 and be experienced as the floating movement in the structure as described. In other words, the change in the load of the elevator car 120 changes the tension in the elevator rope 130 and, thus, the floating structure also moves and the movement may be detected with the number of load sensors of the load weighing device 110. The load sensors of the load weighing device 1 10 in the embodiment of Figure 2 may e.g. be strain gauges that may generate a measurement value e.g. representing a force affecting in the vertical direction, e.g. downwards in accordance with the change in the load of the elevator car 120. As a conclusion it is worthwhile to mention that also the approach shown in Figure 2 may generate information on the tension the elevator rope 130 is experiencing indirectly based on the relative movement of the mounting structure 220 with respect to a fixed structure. Hence, any load sensors with the arrangement e.g. as shown in Figure 1 are not necessary.

[0050] As described in the foregoing description Figure 1 and Figure 2 schematically illustrate arrangements for measuring load of the elevator car 120 and the present invention for calibrating the load weighing device 1 10 may be applied in those elevator arrangements. In order to describe at least some aspects relating to the calibration of the load weighing device 1 10 Figure 3 is referred to wherein a method for performing the calibration according to an example is schematically illustrated. For performing the calibration of the load weighing device 1 10 the elevator may be controlled e.g. through the elevator controller of the respective elevator e.g. from an external source, such as from data centre arranged to manage the respective elevator or from a terminal device of a technician, for example. The calibration process may be a computer-controllable process e.g. initiated by a user, such as a technician, willing to cause the calibration.

[0051] The calibration may be initiated with a tuning process as referred in Figure 3 with the reference 310. In the step 310 of the method the elevator is tuned 310 which refers to an operation in which a motion control of the elevator is optimized without of load in the elevator car 120, i.e. the elevator car 120 is empty. In order to perform the tuning process the load weighing device 1 10 is reset so that the output of the load weighing device corresponds to zero load during the tuning process. In other words, a motion control of the elevator, such as an elevator controller, sees the output of the load weighing device to correspond to zero load. Thus, the output of the load weighing device 1 10 may be set to generate zero output, or any other value desired to correspond to the zero load situation. The tuning process 310 may be an automatic process, controlled through the motion control of the elevator with applicable control signal(s) to perform the drive(s) as described herein, wherein the empty elevator car 120 is first instructed to travel to a bottom floor. In response to this the elevator is instructed to perform a test run to a top floor. After that the elevator car 120 is instructed to travel back to the bottom floor. The travels may be repeated a number of times. The test run may also be initiated from the top floor and the elevator car 120 is instructed to travel to the bottom floor and then back to the top floor. The test run follows a predefined motion pattern, such as the elevator car is driven at a constant speed in the both directions and a torque of the electric motor is determined e.g. by measuring it directly or indirectly, typically indirectly e.g. through obtaining information on the electrical quantities in driving the electric motor (cf. supplied power, current and / or voltage) and determining the torque from these in a known manner. In case the test run complies with preset requirements, the automatic tuning process comprises a step in which drive parameters of the elevator are refreshed according to ones that generated the successful test drive and, as a result, the elevator in question applies them in the operation. In association with the tuning various parameters of the elevator setup are known. Namely, a radius of a traction sheave (r), a rope reeving ratio, a nominal load (mL,nom) and a shaft height (Hs) are made available for the tuning process e.g. as a design parameters of the elevator or determined otherwise. Hence, the drive parameters, which can e.g. be automatically tuned in the described manner, can be for example: a balance parameter (b), an effective rope and car cable mass (ptot), total non-changing masses (Ma), a shaft efficiency (q) and / or torque gain. The optimization of the drive parameters and application of them generate a torque of the electric motor 170 of the elevator over the travel path of the elevator car 120. Now, as an output of the tuning process 310 a balance load (mbai) is determined which may be performed by means of the balance parameter (b) determined as the drive parameter. Hence, the computing apparatus is arranged to determine the balance load mbai computationally with an equation: bai=bmnorn wherein b is the balance parameter determined in the step 310 of the method as described and mnOm is the nominal load mass of the elevator that comes from the design of the elevator in question.

[0052] Another approach to the balance load mbai and its calculation by means of torque can be expressed with the following equation:

[0053] The equation indicates that the balance load mbai may be determined by determining an average of average torques measured and determined in upward direction and downward direction movement of the elevator car 120 in the tuning process. The determined average of the average torques is then multiplied with the reeving ratio ir and the result is divided by a product of the radius of the traction sheave r and the gravitational acceleration g. The equation links the torques, or averages of them in both directions e.g. obtained with one or more elevator test runs, with physical specifications of the elevator in question. In response to the determination of the balance load rribai with the equation above the balance parameter may be calculated with the preceding equation by inputting the determined balance load rribai value therein. As said, the application of the equation above requires a measurement of the torques, and determinations of the averages from the measurement data, through the test run thus enabling further use of the calculated balance load mbai.

[0054] According to the invention the calibration process itself is continued with a step 320 as shown in Figure 3 wherein the elevator load weighing device 1 10 is calibrated for zero load, e.g. in the implementation of the elevator as schematically illustrated in Figure 1 or in Figure 2. The zero load calibration is performed to an elevator car without load, i.e. that the elevator car is empty. In other words, the zero load calibration to the load weighing device 1 10 is performed 320 with respect to an elevator car of the elevator without a load in the elevator car by setting an output of the to load weighing device to correspond to a zero load of the elevator. The aim of the step 320, i.e. performing 320 the zero-load calibration, is that an effect of a weight of the elevator rope 130 and any other cables and entities traveling at least in part with the elevator car 120 in the shaft, such as the travelling cable, can be compensated. In accordance with one advantageous approach this is achieved by performing 320 the zeroload calibration at two different positions in the elevator shaft. For example, the elevator car 120 may be instructed to travel to a bottommost floor, cf. the bottom floor, if not already residing there and the load weighing device 1 10 is calibrated to the zero load at the bottom floor position. For example, the output of the load weighing device 1 10 may be set to zero, or to any other value decided to correspond to the zero load situation. Next, the elevator car 120 is instructed to travel to another position, which may be the topmost floor, cf. the top floor, and, correspondingly, the load weighing device 1 10 is calibrated to the zero load at the top floor position. For example, the output of the load weighing device 110 may be set to zero, or to the any other value decided to correspond to the zero load situation. As a result, by assuming a linear behavior in respect to the car position the weight of the elevator rope 130 and the cable(s) throughout a travel path of the elevator car, i.e. in any position in the shaft, may be compensated.

[0055] The zero load calibration of the load weighing device 1 10 may also be performed so that it is defined in more than two positions in the shaft, even throughout a height of the elevator shaft. In case the zero load calibration is performed at two positions, the calibration result is the most accurate if the two positions are the extreme positions of the elevator car in the shaft, i.e. the topmost and the bottommost positions. For sake of completeness it is worthwhile to mention that the zero load calibration may be performed 320, in some rough accuracy, using only one position in the elevator shaft, but such an approach does not enable filtering out the weight of roping.

[0056] For sake of completeness it is worthwhile to mention that even if the steps 310 and 320 are herein described to be executed in the described (and illustrated) order, they may also be executed in an opposite order, i.e. the step 320 is executed prior to the step 310. Furthermore, the steps 310 and 320 may be based on data obtained in one or more travels of the elevator car 120 as described.

[0057] As mentioned herein, the zero load calibration is performed with respect to an elevator car without load, i.e. the elevator car is empty. The entity performing the calibration may be configured to confirm that the elevator car is empty e.g. prior to initiating the zero load calibration. For example, the emptiness of the elevator car 120 may e.g. be confirmed by obtaining measurement data from a measurement system indicative of the loading state of the elevator wherein the measurement system may refer to a sensor system, such as a image capturing device based system that is configured to obtain image data from inside the elevator car 120 that image data is analyzed either manually or automatically to confirm the state inside the elevator car 120. The same may also be achieved through a visual inspection of the state in the elevator car e.g. by a technician and through a generation of a signal indicative of the state, especially confirming the emptiness of the elevator car 120 towards the computing apparatus performing the calibration. Generally speaking, the computing apparatus responsible for the calibration may receive such a signal from a control entity of the elevator wherein the control entity may e.g. be a remote server, a computing device of a technician (in case it is other than the computing apparatus implementing the method or internally therein if the device is the same as the computing apparatus implementing the method) or even to a communication interface of the elevator through which e.g. the technician may directly or indirectly provide data on the state inside the elevator car 120 as described.

[0058] In accordance with the embodiment schematically illustrated in Figure 3 the method for calibrating the load weighing device 1 10 is continued by performing so-called non-zero load point calibration to the load weighing device 110 from that perspective. The non-zero load point calibration phase comprises a number of steps as shown in Figure 3 and discussed in the forthcoming description. Namely, in order to perform the non-zero point calibration the elevator car 120 is locked in a position in the elevator shaft. The locking may be performed in a predefined position in the shaft wherein a blocking device 150, or at least a part of it, is arranged to. Alternatively, e.g. in a situation that the elevator car 120 is provided with a specific blocking arrangement, such as with a specific braking device (cf. the parking brake), the position may be freely selected in the shaft. In the case of having an arrangement that a part of the blocking device 150 is mounted to the elevator car 120 and a counterpart of the blocking device 150, such as a blocking plate, is arranged in another structure, such as to a guide rail or to the elevator shaft, the elevator car 120 driven to the position and the locking is performed by instructing the blocking device 150 to activate the locking. Hence, the locking of the elevator car 120 in the described manner prevents a movement of the elevator car 120 even if the machinery brakes 180 are released. The blocking device 150 may be manually controlled or controlled with control signals generated remotely. In the latter case, the blocking device 150 is provided with necessary communication means, such as wireless modem, that is communicatively connected, e.g. through a control circuit to an electrically controllable actuator that causes the locking either directly or indirectly. As a non-limiting example of the locking mechanism an electrically controllable shaft, or a pin, of the blocking device 150 may be instructed to engage with the blocking plate with a control signal generated remotely over a communication interface and a release of the locking mechanism may also be controlled with another control signal. Hence, in response to the locking of the elevator car 120 with the blocking device 150 in the described manner the computing apparatus arranged to perform the method according to the invention is configured to receive 330 data indicative of the locking of the elevator car 120 of the elevator in the position in the elevator shaft and a detection of the locking is detected based on the receipt of the data. The data indicative of the locking may be based on an acknowledgement that a control signal is generated to lock the elevator car 120. The acknowledgement may also be received in response the recipient of the control signal, such as the blocking device 150, receives the control signal. Alternatively or in addition, the locking of the elevator car may be detected by the computing apparatus on a basis of a signal received from a control entity of the elevator wherein the control entity may e.g. be a remote server or a computing device of a technician (in case it is other than the computing apparatus implementing the method or internally therein if the device is the same as the computing apparatus implementing the method) or even a communication interface of the elevator through which e.g. the technician may directly or indirectly provide data on the state of the locking and especially on that the elevator car 120 is locked in the position. Alternatively or in addition, the computing apparatus performing the method may also cause a testing procedure to test if the elevator car 120 is locked in its position in a required manner and the test result indicates the result, such as the locking is in place. The testing procedure may e.g. comprise controlling of an electric motor 170 or measuring control signals of the electric motor 170 so as to confirm the locking situation.

[0059] As said, the elevator car 120 is locked in any of the described manners in a position of the elevator shaft and in response to this data indicative of that a traction sheave 190 of the elevator is set, or was set, to a state that it is free-to- rotate is received 340. This may e.g. be confirmed by detecting by the computing apparatus that machinery brakes 180 are in a released position, i.e. do not cause braking to the traction sheave 190, and / or to the roping system in general. To achieve this may e.g. require a generation of a control signal to cause releasing of the machinery brakes 180 and this may e.g. be achieved by instructing the elevator controller to perform the releasing of the brakes 180 wherein the instructing may be generated from a device, such as the computing apparatus, managing the calibration of the load weighing device 1 10. Thus, the data indicative of the free-to-rotate state may be based on the generation of the control signal to release the machinery brakes 180 or to any acknowledgement signal from the braking system or any testing signal, or procedure indicating the released state of the machinery brakes 180. A cycle of releasing and activating the machinery brakes may be performed a plurality of times in accordance with the calibration process. When the machinery brakes are released and the elevator car 120 is locked in the described manner, it means that the weight of the elevator car 120 as well as other entities relating to the elevator car 120, such as the sling and the travelling cable, is filtered out from the elevator rope 130 tension and, thus, the tension experienced by the elevator rope 130 results from the weight of the counterweight 160 and the tension is detected with the load weighing device 1 10 under calibration. For sake of completeness it is worthwhile to mention that the traction sheave 190 and the pulleys P are freely rotatable naturally causing some friction with respect to the elevator rope 130 when braking is not impacted to the respective entities in any manner. Hence, the output from the load weighing device 1 10 is indicative of the weight of the counterweight 160 naturally affected by the reeving ratio of the elevator rope 130 in accordance with the implementation of the roping. In any case, the output value from the load weighing device 1 10 in the described situation corresponds to a balance load of the elevator car 120 in the elevator setup in question. This is because the situation in which the elevator car 120 is locked in the described manner corresponds to a balance situation without the locking. In other words, in both situations the counterweight is stationary, i.e. the force affecting the rope in the counterweight side (from the viewpoint of the traction sheave) is the same. Moreover, since the traction sheave is set freely rotatable, also the force affecting the rope in the elevator car side (from the viewpoint of the traction sheave) is also the same. All this corresponds to the balance situation without locking. As a result, the balance load obtained in the calibration in the described manner is set accordingly in the load weighing device 1 10. It is worthwhile to mention that the approach to set the traction sheave to the state that it is free- to-rotate aims to cause the tension to the elevator rope 130 only from the counterweight. In response to achieving this the machinery brakes 180 may again be activated since the tension remains therein and the further steps in the calibration may be taken as described in the forthcoming description.

[0060] For sake of completeness it is worthwhile to mention that the receipt of data indicative of that the traction sheave 190 is free-to-rotate may also comprise a detection that a generation of a torque by the electric motor 170 of the elevator is canceled. In other words, the aim is to confirm that the electric motor 170 does not generate any torque in the system which makes the traction sheave 190 not free-to-rotate. The detection may be based on that the data received by the computing apparatus represents the control signal of the electric motor 170, e.g. received from a drive system of the electric motor 170. Moreover, the step 340 may also be based on that the detection of the free movement, cf. free-to-rotate state, is detected with a sensor system, such as by receiving measurement data from an encoder of the electric motor 170 or from any other movement detection system of the elevator, such as from a position determination system implemented in the elevator shaft the elevator in question resides (e.g. based on predefined codes (e.g. QR codes) implemented and read in the elevator shaft and a detection of the position at landings and so on). In the described manner it is possible to detect e.g. if the locking of the elevator car has failed or any other situation is occurring. In response to such a detection necessary safety mechanisms may be initiated. Moreover, the receipt of data indicative of that the traction sheave 190 is free-to-rotate may also refer to an implementation that the computing apparatus receives a signal from a control entity of the elevator that signal carries data indicative on that the traction sheave 190 is in a state that it is free-to-rotate. The control entity may again refer to a remote server, a computing device of a technician (in case it is other than the computing apparatus implementing the method or internally therein if the device is the same as the computing apparatus implementing the method) or even to a communication interface of the elevator through which e.g. the technician may directly or indirectly provide data on the state of the traction sheave 190 as described.

[0061] Finally, in response to a detection that data indicative of that the elevator car 120 is locked in the position is received 330 and that data indicative of that the traction sheave 190 is free-to-rotate is received 340 the computing apparatus is configured to set 350 an output signal of the load weighing device 1 10 to correspond to the balance load of the elevator determined by performing 310 the motion control operation for the elevator. Thus, the calibration of the load weighing device 1 10 is achieved in this regard, i.e. in relation to the non-zero load point calibration.

[0062] For sake of completeness, it is schematically illustrated in Figure 3 that the steps 330 and 340 are consecutive to each other but the operations leading to the receipt of the data by the computing apparatus may be executed at least in part parallel to each other and the computing apparatus performs the step 350 in response to that the received pieces of data fulfill the requirements for allowing to set the output signal of the load weighing device 1 10 to correspond to the balance load.

[0063] It is also worth mentioning that the zero-load calibration 320 and the non-zero load calibration comprising the steps referred with 330, 340, 350 in Figure 3 may be performed in any order as long as the tuning step 310 is performed prior to the non-zero load point calibration in order to have the information on the balance load in place.

[0064] By considering the non-zero point calibration, and the above-described aspects, mathematically as a whole the balance load may be expressed, as already mentioned, with formula: fTIbal=b / Inom wherein b is the balance parameter determined in the step 310 of the method as described and mnOm is the nominal load mass of the elevator that comes from the design of the elevator in question. Hence, by having two points determined through the method as described, i.e. the zero load point based on the step 320 of the method and the balance load point as defined through the steps 330 and 340 as described, and by assuming that the operation of the load weighing device 110 is linear, it is possible to derive load in the elevator car 120 in an improved accuracy based on the output of the load weighing device 110. In case the load in the elevator car 120 in the measurement situation is larger than the balance load determined with the step 330, an extrapolation approach may be applied in the determination due to the linear operation of the load weighing device 1 10.

[0065] In some embodiments the balance parameter determined in the step 310 as described may be adjusted to be more accurate for the purpose of calibrating the load weighing device 1 10. The approach in the adjustment may be that a correction factor is applied to the balance parameter b wherein the correction factor may be determined e.g. throughout an analysis of an accuracy of the calibration according to the invention e.g. with a testing with test weights. In some approaches the correction factor may be at least in part dependent on a friction due to the roping solution in the elevator. Typically, the correction factor causes that the balanced load value used for calibration is slightly smaller than the balance load obtained through the tuning process.

[0066] An example of a computing apparatus 400 configurable to implement the operation in accordance with the invention is schematically illustrated in Figure 4. The computing apparatus 400 may be configured to perform at least the method according to the invention as described with the examples in the foregoing description. Thus, the computing apparatus 400 of Figure 4 may be configured to perform a calibration of a load weighing device of an elevator. For sake of clarity, it is worthwhile to mention that the block diagram of Figure 4 depicts some components of an apparatus that may be employed to implement a functionality of the computing apparatus 400. The apparatus of Figure 4 comprises a processor 410 and a memory 420. The memory 420 may store data, such as pieces of data as described, but also computer program code 425 causing the operation in the described manner. In at least some embodiments, the computing apparatus 400 may further comprise a communication interface 430, such as a wireless communication interface or a communication interface for wired communication, or both to communicate with other entities as described. The communication interface 430 may thus comprise one or more modems, antennas, and any other hardware and software for enabling an execution of the communication e.g. under control of the processor 410. Furthermore, I / O (input / output) components may be arranged, together with the processor 410 and a portion of the computer program code 425, to provide a user interface for receiving input from a user, such as from a technician, and / or providing output to the user of the apparatus when necessary. The user interface may e.g. refer to the control interface 300 as described. In particular, the I / O components may include user input means, such as one or more keys or buttons, a keyboard, a touchscreen, or a touchpad, etc. The I / O components may include output means, such as a loudspeaker, a display, or a touchscreen. The components of the computing apparatus 400 may be communicatively connected to each other via data bus that enables transfer of data and control information between the components.

[0067] The memory 420 and at least a portion of the computer program code 425 stored therein may further be arranged, with the processor 410, to cause the computing apparatus 400 to perform at least a portion of a method as is described herein. The processor 410 may be configured to read from and write to the memory 420. Although the processor 410 is depicted as a respective single component, it may be implemented as respective one or more separate processing components. Similarly, although the memory 420 is depicted as a respective single component, it may be implemented as respective one or more separate components, some, or all of which may be integrated I removable and I or may provide permanent I semi-permanent I dynamic I cached storage.

[0068] The computer program code 425 may comprise computer-executable instructions that implement functions that correspond to steps implemented in the method when loaded into the processor 410 of the respective system, such as the computing apparatus 400. As an example, the computer program code 425 may include a computer program consisting of one or more sequences of one or more instructions. The processor 410 is able to load and execute the computer program by reading the one or more sequences of one or more instructions included therein from the memory 420. The one or more sequences of one or more instructions may be configured to, when executed by the processor 410, cause the computing apparatus 400, such as a computer, to perform a method as described. Hence, the apparatus may comprise at least one processor 410 and at least one memory 420 including the computer program code 425 for one or more programs, the at least one memory 420 and the computer program code 425 configured to, with the at least one processor 410, cause the apparatus implementing the computing apparatus 400 to perform the method.

[0069] The computer program code 425, or at least some portion of it, may be provided e.g. a computer program product comprising at least one computer-readable non-transitory medium having the computer program code 425 stored thereon, which computer program code 425, when executed by the processor 410 causes the computing apparatus 400 to perform the method. The computer- readable non-transitory medium may comprise a memory device or a record medium, such as a CD-ROM, a DVD, a Blu-ray disc, or another article of manufacture that tangibly embodies the computer program. As another example, the computer program may be provided as a signal configured to reliably transfer the computer program.

[0070] Still further, the computer program code 425 may comprise a proprietary application, such as computer program code for causing an execution of the method in the manner as described in the description herein.

[0071] Any of the programmed functions mentioned may also be performed in firmware or hardware adapted to or programmed to perform the necessary tasks.

[0072] For sake of completeness it is worthwhile to mention that the entity performing the method in the role of the computing apparatus 400 may also be implemented with a plurality of apparatuses, such as the one schematically illustrated in Figure 4, as a distributed computing environment. For example, one of the apparatuses may be communicatively connected with the other apparatuses, and e.g. share the data of the method, to cause another apparatus to perform at least one other portion of the method. As a result, the method performed in the distributed computing environment generates the control interface as described. The functionalities of the computing entity 1 10 as described may also be integrated to an entity configured also to perform other operations.

[0073] As a non-limiting examples it may be arranged that the functionality of the computing apparatus 400 is implemented in an elevator controller, for example, which is arranged to execute a calibration procedure in accordance with the method as described. In some approaches the computing apparatus 400 may be an external device, such as a computer like a laptop computer, a tablet computer or any other handheld device, that is connectable to the elevator system and to the load weighing device in order to generate one or more control signals for performing the calibration of the load weighing device 1 10 in the manner as described herein. Such a handheld device may be carried by a technician assigned with a task to perform the calibration.

[0074] The calibration of the load weighing device 1 10 in accordance with the invention improves an accuracy of a calibration of the load weighing device 1 10 compared to the prior art solutions as described. This is at least in part due to that the calibration is based on data, or information, obtained with a number of test drives and, thus, is based on a real operation of the elevator in question. For sake of completeness it is worthwhile to mention that the calibration in the described manner covers the calibration of the whole load weighing device 1 10 wherein any inaccuracies in the output of the device 1 10 may origin from inaccuracy in an operation of the sensor entity of the load weighing device 110 and / or in an operation of the electronics of the load weighing device 1 10 among any other roots of inaccuracies.

[0075] The specific examples provided in the description given above should not be construed as limiting the applicability and / or the interpretation of the appended claims. Lists and groups of examples provided in the description given above are not exhaustive unless otherwise explicitly stated.

Claims

WHAT IS CLAIMED IS:

1. A method for calibrating a load weighing device (110) of an elevator, the method, performed by a computing apparatus (400), comprises: performing (310) a motion control operation for the elevator for determining a balance load of the elevator, performing (320) a zero load calibration of the load weighing device (110), the zero load calibration is performed with respect to an elevator car (120) of the elevator without a load in the elevator car (120) by setting an output of the load weighing device (110) to correspond to a zero load of the elevator, the method further comprises: performing a non-zero load point calibration of the load weighing device (110), the non-zero load point calibration comprises: receiving (330) data indicative of a locking of an elevator car (120) of the elevator in a position in an elevator shaft, receiving (340) data indicative of that a traction sheave (190) of the elevator is set free-to-rotate in response to the locking of the elevator car (110), setting (350) an output signal of the load weighing device (110) to correspond to the balance load of the elevator determined by performing the motion control operation for the elevator.

2. The method according to claim 1 , wherein the motion control operation comprises: generating a control signal to cause the elevator to drive at least one elevator test run, preferably comprising at least one back and forth run between bottom and top floors.

3. The method according to any of the preceding claims, wherein a torque of an electric motor (170) of the elevator is determined during the motion control operation.

4. The method according to any of the preceding claims, wherein the motion control operation comprises: setting an output of the load weighing device (110) to correspond to a zero load during the motion control operation.

5. The method according to any of the preceding claims, wherein the motion control operation comprises: determining a balance parameter, determining computationally the balance load with the balance parameter.

6. The method according to any of the preceding claims 1 -4, wherein the motion control operation comprises: determining computationally the balance load based at least on torque data of an electric motor (170) of the elevator, the torque data determined through the at least one elevator test run.

7. The method according to claim 6, wherein the balance parameter is determined by means of the balance load determined computationally based at least on the torque data of the electric motor (170) of the elevator.

8. The method according to any of the claims 5-7, wherein the determination of the balance parameter comprises: adjusting the balance parameter with a correction factor wherein the correction factor compensates at least in part a friction in a roping solution of the elevator.

9. The method according to any of the preceding claims, wherein a detection that the elevator car (120) is without load when performing (320) the zero loadcalibration is based on at least one of the following: data received from a sensor system, a signal received from a control entity of the elevator.

10. The method according to any of the preceding claims, wherein the zeroload calibration of the load weighing device (110) is performed by: setting an output of the load weighing device (1 10) to filter out a weight of at least an elevator rope (130) by determining the weight of at least the elevator rope (130) in at least two positions of an elevator car (120) in an elevator shaft.1 1 . The method according to any of the preceding claims, wherein a detection of the locking of the elevator car (120) is based on at least one of the following: a receipt of an acknowledgement of a generation of a control signal to lock the elevator car (120); a signal received from a control entity of the elevator; a test result controlled by the computing apparatus (400).

12. The method according to any of the preceding claims, wherein the data indicative of that the traction sheave (190) of the elevator is free to rotate is based on at least one of the following: a detection of a release of machinery brakes (180); a detection that a generation of a torque by the electric motor (170) of the elevator is canceled; a detection of a motion from an encoder of the electric motor (170); a detection of a motion with a position determination system; a signal received from a control entity of the elevator.

13. A computing apparatus (400) for calibrating a load weighing device (1 10) of an elevator, the computing apparatus (400) is configured to: perform (310) a motion control operation for the elevator for determining a balance load of the elevator, perform (320) a zero load calibration of the load weighing device (1 10), the zero load calibration is performed with respect to an elevator car (120) of the elevator without a load in the elevator car (120) by setting an output of the load weighing device (110) to correspond to a zero load of the elevator, the computing apparatus (400) is further configured to:perform a non-zero load point calibration of the load weighing device (1 10), wherein the non-zero load point calibration the computing apparatus (400) is configured to: receive (330) data indicative of a locking of an elevator car (120) of the elevator in a position in an elevator shaft, receive (340) data indicative of that a traction sheave (190) of the elevator is set free-to-rotate in response to the locking of the elevator car (1 10), set (350) an output signal of the load weighing device (1 10) to correspond to the balance load of the elevator determined by performing the motion control operation for the elevator.

14. The computing apparatus (400) according to claim 13, wherein the computing apparatus (400) is configured to perform at least part of the motion control operation by: generating a control signal to cause the elevator to drive at least one elevator test run, preferably comprising at least one back and forth run between bottom and top floors.

15. The computing apparatus (400) according to claim 13 or claim 14, wherein the computing apparatus (400) is configured to determine a torque of an electric motor (170) of the elevator during the motion control operation.

16. The computing apparatus (400) according to any of the preceding claims 13-15, wherein the computing apparatus (400) is configured to perform at least part of the motion control operation by: setting an output of the load weighing device (1 10) to correspond to a zero load during the motion control operation.

17. The computing apparatus (400) according to any of the preceding claims 13-16, wherein the computing apparatus (400) is configured to perform at least part of by:determining a balance parameter, determining computationally the balance load with the balance parameter.

18. The computing apparatus (400) according to any of the preceding claims 13-16, wherein the computing apparatus (400) is configured to perform at least part of by the motion control operation by: determining computationally the balance load based at least on torque data of an electric motor (170) of the elevator, the torque data determined through the at least one elevator test run.

19. The computing apparatus (400) according to claim 18, wherein the computing apparatus (400) is configured to determine the balance parameter by means of the balance load determined computationally based at least on the torque data of the electric motor (170) of the elevator.

20. The computing apparatus (400) according to any of the claims 17-19, wherein the computing apparatus (400) is configured to perform the determination of the balance parameter at least by: adjusting the balance parameter with a correction factor wherein the correction factor compensates at least in part a friction in a roping solution of the elevator.21 . The computing apparatus (400) according to any of the preceding claims 13-20, wherein the computing apparatus (400) is configured to perform a detection that the elevator car (120) is without load when performing (320) the zero load calibration on a basis of at least one of the following: data received from a sensor system, a signal received from a control entity of the elevator.

22. The computing apparatus (400) according to any of the preceding claims 13-21 , wherein the computing apparatus (400) is configured to perform the zeroload calibration of the load weighing device (110) by:setting an output of the load weighing device (1 10) to filter out a weight of at least an elevator rope (130) by determining the weight of at least the elevator rope (130) in at least two positions of an elevator car (120) in an elevator shaft.

23. The computing apparatus (400) according to any of the preceding claims 14-23, wherein the computing apparatus (400) is configured to perform a detection of the locking of the elevator car (120) on a basis of at least one of the following: a receipt of an acknowledgement of a generation of a control signal to lock the elevator car (120); a signal received from a control entity of the elevator; a test result controlled by the computing apparatus (400).

24. The computing apparatus (400) according to any of the preceding claims 13-23, wherein the computing apparatus (400) is configured to use, as the data indicative of that the traction sheave (190) of the elevator is free to rotate, at least one of the following: a detection of a release of machinery brakes (180); a detection that a generation of a torque by the electric motor (170) of the elevator is canceled; a detection of a motion from an encoder of the electric motor (170); a detection of a motion with a position determination system; a signal received from a control entity of the elevator.

25. The computing apparatus (400) according to any of the preceding claims 13-24, wherein the computing apparatus (400) is an elevator controller configured to receive measurement data from a load sensor.

26. A computer program comprising instructions to cause the computing apparatus (400) of claim 13 to execute the steps of the method of claim 1 .

27. An elevator comprising: an elevator car (120), an electric motor (170) configured to move the elevator car (120), a blocking device (150) configured to lock the elevator car (120), and a computing apparatus (400) according to any of the preceding claims 13-25.

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