Method of operating an elevator system and elevator system

Abstract

The invention relates to a method of operating an elevator system and an elevator system, comprising a calibration unit (14) obtaining car load information from a load weighing device (11, 12), the information indicating a position of a car (3), motor load information from an elevator drive unit (4, 17). The calibration unit (14) calculates calibration data for the car load information after the start of a first elevator run, based on a difference between the car load information obtained before the first elevator run and the motor load information obtained during the start of the first elevator run, and taking into account an imbalance and un-compensation at the position of the start of the first elevator run. The elevator system (1) utilizes the calculated calibration data to correct car load information obtained from the load weighing device (11, 12) in relation to subsequent elevator runs.

Description

TECHNICAL FIELD

[0001] The present invention relates to a solution for operating an elevator system in a safe and efficient manner. More specifically, the solution makes it possible to obtain correct information about the state of the elevator system when the elevator system is in operation. BACKGROUND

[0002] In order to operate an elevator in a safe and efficient manner, information about the load of the elevator car in operation is needed. This information is necessary to ensure smooth movement and is also essential for safety. The size of the elevator brake is adapted to a certain full load rating, which should not be exceeded for safety reasons and for the comfort of the passengers. Furthermore, the elevator system is utilizing solutions for automatic monitoring and testing of the brake. In order to obtain reliable data from such monitoring and testing, it is important to know the actual load during brake testing.

[0003] In order to obtain information about the current load, the elevator system is provided with a load weighing device (LWD) to measure the elevator car load. The car load information is provided to the elevator control unit, which is provided with a user interface with a manual potentiometer or other convenient means by which a service person can manually calibrate the car load measurement at different car positions and at different loads. This requires that different reference weights are loaded onto the elevator car in turn in order to obtain the required measurements at different loads at different positions.

[0004] The drawback of the previously known solution is that it is very laborious and time-consuming, especially since occasional recalibration is required. For example, calibration can become necessary in the event of modifications to the elevator car, to the counterweight, or to the ropes of the elevator system. SUMMARY

[0005] It is an object of the present invention to solve the above-mentioned drawbacks and to provide a simple and efficient solution for obtaining correct information about the state of the elevator system. This object is achieved by the method according to the independent claim 1 and by the elevator system according to the independent claim 5, wherein the calibration data for the car load information is calculated based on the motor load information taking into account unbalance and uncompensation at the position.

[0006] Preferred embodiments of the invention are disclosed in the dependent claims. BRIEF DESCRIPTION OF DRAWINGS

[0007] The invention will be described in more detail below by way of example and with reference to the drawings, in which

[0008] Figure 1 is a flow chart of a method for operating an elevator system, and

[0009] Figure 2 An elevator system is illustrated. DETAILED DESCRIPTION

[0010] Figure 1 A method for operating an elevator system is shown, which is suitable for use, for example, in Figure 2 The elevator system 1 shown uses.

[0011] In step A, an imbalance between the weight of the elevator counterweight 2 and the weight of the empty elevator car 3 is determined. This can be done by measuring the motor 4 current, i.e. the motor load, during upward and downward test runs of the empty elevator car 3 before the first elevator run for transportation purposes is started and by storing the determined imbalance information into the memory 16 of the elevator system 1. In practice, the imbalance can be determined when the elevator system in question is first put into use after installation. If necessary, the measurement can be repeated later.

[0012] A solution for determining the imbalance of an elevator system is previously known and disclosed in US2019330016A1, especially in equation 1.4 (in which it is called elevator system balance m b Step A can be implemented, for example, by utilizing such a solution.

[0013] In step B, the uncompensated mass of the elevator system at different locations of the elevator shaft is determined. This step can also be done before the first elevator run for transportation purposes is started after the elevator system is installed, at which stage the imbalance information is stored into the memory of the elevator system, for example into the memory 16 of the calibration unit 14.

[0014] The uncompensated mass of the elevator system depends, for example, on the difference in the weight of the hoisting ropes 6, 7 suspended on different sides of the traction sheave 5. The uncompensated mass changes when the elevator car 3 and the counterweight 2 move between different locations in the elevator shaft 8, for example between different floors 9 and 10. Thus, the uncompensated mass is different at different locations of the elevator.

[0015] In step B, the uncompensated mass can be determined from equation 3.2 of US2019330016A1. (in which it is called compensation error AB). Alternatively or additionally, measurements can be made at at least two different locations with the load weighing device 11 or with other suitable measuring devices, for example by means of motor load information, while the elevator car is kept stationary at locations 9 and 10 during the measurements, assuming that the uncompensated mass changes linearly between these locations. This makes it possible to calculate the uncompensated mass at any point between these locations 9 and 10 by taking into account the distance between these points.

[0016] In some elevator systems a so-called compensation rope has been installed under the elevator car and counterweight to reduce un-compensation. In case such a compensation rope is used, it can be sufficient to determine this point in step B and determine that the un-compensation is zero or so small that it can be neglected.

[0017] In step C, car load information is obtained from load weighing devices before the first elevator run (for transportation purposes) is initiated. In the shown example two different positions of load weighing devices are illustrated by way of example, but in practice it is sufficient to use only one load weighing device for the elevator car. The weighing device 11 is a load cell connected to the knot of the elevator hoisting rope 6, while the second alternative position of the load weighing device 12 is connected with the elevator car 3 floor, the load weighing device can for example be suspended by springs, so that the load on the elevator floor can be measured. The car load information can be obtained from the load weighing device 11 or 12 to the input 13 of a calibration unit 14 included in the elevator control 15.

[0018] A check in step D is performed to ensure that the car load is below an overload threshold. This check can be performed by the elevator controller 15. In case the car load is not below the overload threshold, initiation of the elevator run can be prevented.

[0019] Elevator systems are manufactured with a rated load and should not be allowed to operate in case the car load is too large. Therefore, the elevator control can keep in a memory 16 an overload threshold which is used for comparison with the obtained car load information to determine whether initiation of the elevator run is allowed. In some cases it can be preferred to set the overload threshold slightly above the rated load of the elevator system. One alternative is to set the overload threshold to 110% of the rated load of the elevator system. In some alternative cases the overload threshold is set to slightly above the rated load but below the 110% limit.

[0020] In step E, the first elevator run (for transportation purposes) is initiated. In this phase of step F, motor load information of the elevator drive unit 17 is obtained based on the motor current achieved during initiation of the first elevator run. The elevator drive unit 17 can be part of the elevator controller 15 and it can comprise for example a frequency controller for controlling the motor 4 of the elevator system. One alternative is that after initiation of the first elevator run, the elevator car is kept stationary in the starting position under the torque action of the elevator drive unit 4, 17. In particular in modern vector controlled drives, said holding torque coincides with the motor current. This is in particular the case with synchronous permanent magnet motors.

[0021] In step G, calibration data is calculated for the car load information based on the difference between the car load information and the motor load information.

[0022] To improve the accuracy of the required calibration, the determined unbalance and the uncompensated at the start position of the first elevator run have been taken into account. By subtracting these known elements of unbalance and uncompensation from the motor load information, a highly accurate second value for the car load information is established, wherein the second value for the car load information can then be used as a reference for the car load information in generating the calibration data.

[0023] To this end, the elevator system is provided with one or more position sensors 17 providing an indication of the position of the elevator car 3 to an input 18 of the calibration unit 14. Naturally, the position or type of sensor or sensors can differ from implementation to implementation.

[0024] In step H, the calculated calibration data is used to correct the car load information from the load weighing devices 11, 12 in relation to subsequent runs, preferably during normal elevator operation. Thus, inaccuracies regarding the weight of the load elevator car can be minimized and eliminated, which makes the elevator runs more comfortable for the user, improves the safety of the brakes during use, and also makes the automatic testing of the brakes more reliable.

[0025] The illustrated calibration unit can be configured to automatically repeat the calculation of calibration data for the car load information and use the newly calculated calibration data. For example, such calculation can be performed for each run, or periodically according to a predetermined schedule. Alternatively, the elevator system can be provided with a user interface 19 connected to the elevator controller 15, so that a maintenance person can provide control commands through the user interface 19 to control the calibration unit to repeat the calculation of calibration data.

[0026] It will be appreciated that the above description and drawings are only intended to illustrate the application. It will be apparent to a person skilled in the art that changes and modifications can be made to the application without departing from the scope thereof.

Claims

1. A method for operating an elevator system (1), characterized in that, The method includes: (A) Determine the imbalance between the elevator counterweight (2) and the empty elevator car (3). (B) Determine the uncompensated mass of the elevator system at different locations (9, 10) in the elevator shaft (8), the uncompensated mass of the elevator system depending on the weight difference of the lifting ropes suspended on different sides of the elevator's traction pulley. (C) Obtain car load information from the load weighing devices (11, 12) before starting the first elevator operation. (F) During the initial elevator operation, motor load information is obtained from the elevator drive unit based on the realized motor current, and (G) By taking into account the uncompensated and determined imbalance at the position where the elevator starts its first run, and based on the difference between the car load information and the motor load information, calibration data for the car load information is calculated, and (H) The calculated calibration data of the elevator system (1) is used to correct the car load information related to subsequent elevator operation obtained from the load weighing devices (11, 12).

2. The method according to claim 1, wherein the motor load information is obtained by using torque from the elevator drive unit to keep the elevator car (3) stationary at the starting position of the first elevator run.

3. The method according to claim 1 or 2, wherein the motor load is determined based on the motor current.

4. The method according to claim 1 or 2, wherein the imbalance is determined by measuring the motor load during upward and downward test runs of the empty elevator car (3) before initiating the first elevator run.

5. The method according to claim 1 or 2, wherein the uncompensated condition is determined by measuring the imbalance at at least two different elevator car positions (9, 10) and by assuming that the imbalance varies linearly between the two different elevator positions (9, 10).

6. The method according to claim 1 or 2, wherein The overload threshold is maintained in memory (16). (D) Compare the car load information with the overload threshold, and When the car load information indicates that the car load exceeds the overload threshold, the elevator operation is prevented from starting.

7. The method according to claim 6, wherein, The overload threshold is selected as 110% of the rated load of the elevator system (1).

8. The method according to any one of claims 1, 2, and 7, wherein, The elevator system (1) automatically repeats the calibration data for the car load information and uses the newly calculated calibration data.

9. An elevator system, characterized in that, The elevator system (1) includes a calibration unit (14), which includes: An input unit for receiving car load information provided by the load weighing devices (11, 12), An input unit for receiving information indicating the position of the elevator car (3), An input section for receiving motor load information from the elevator drive unit, and The memory (16) stores imbalance information indicating the imbalance between the elevator counterweight (2) and the empty elevator car (3), as well as uncompensated elevator system mass information at different locations (9, 10) in the elevator shaft (8), wherein the uncompensated elevator system mass depends on the weight difference of the lifting ropes suspended on different sides of the elevator's traction pulley, wherein The calibration unit (14) calculates calibration data for the car load information after starting the first elevator operation, based on the difference between the car load information obtained before the first elevator operation and the motor load information obtained during the start of the first elevator operation, and taking into account the imbalance and uncompensated conditions at the start position of the first elevator operation. The imbalance and uncompensated conditions at the start position of the first elevator operation are indicated by the imbalance and uncompensated information stored in the memory (16). The elevator system (1) uses the calculated calibration data to correct the car load information related to subsequent elevator operation obtained from the load weighing devices (11, 12).

10. The elevator system according to claim 9, wherein The elevator system (1) includes a memory (16) that maintains an overload threshold. The elevator system compares the car load information with the overload threshold, and When the car load information indicates that the car load exceeds the overload threshold, the elevator system prevents the elevator from starting.

11. The elevator system according to claim 9 or 10, wherein the calibration unit (14) automatically repeats the calibration data for the car load information and automatically uses the newly calculated calibration data.

12. The elevator system according to claim 9 or 10, wherein the calibration unit (14) repeatedly calculates the calibration data for the car load information, and in response to a control command from the user interface (19) of the elevator system, the calibration unit (14) uses the newly calculated calibration data.

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