Method for determining torque constant of lifting motor of elevator, elevator control unit, elevator system and computer readable storage medium

Abstract

A method for determining a torque constant of a lift motor (302) of an elevator system (300). The method includes causing an elevator car (310) to perform (110) a round trip in an elevator hoistway (340) with a lifting motor (302), wherein the round trip includes a constant speed portion (21) in a first direction and a constant speed portion (22) in an opposite second direction. The method comprises: determining (120) a motor current of the lifting motor (302) at least during a constant speed portion, for example recording a sampled value thereof; determining (130) an average value of the motor current in the constant speed portion (21, 22); and determining (140) a torque constant based on the average value, an elevator balance condition, and one or more mechanical parameters related to force transfer between the lift motor (302) and the elevator car (310). An elevator system (300), an elevator control unit (1000) and a computer readable storage medium are also disclosed.

Description

Technical Field

[0001] The present invention generally relates to elevator systems and hoist motors thereof. However, in particular, but not exclusively, the present invention relates to a method, a control unit and a computer readable storage medium for use in an elevator system for determining a torque constant of a hoist motor. Background Art

[0002] The elevator car is transferred in the elevator shaft through the landings by means of an elevator hoisting motor (such as a permanent magnet motor). The movement of the car is controlled by supplying current to the hoisting motor via a frequency converter.

[0003] The motor current is regulated by a frequency converter to control the movement of the car. Modern elevators require high operating quality. The movement of the car should be smooth and comfortable for elevator passengers.

[0004] A smooth and comfortable ride requires the inverter's control unit to have the most accurate motor control parameters possible. On the other hand, control parameters are usually determined for a certain motor type, which means that there may be tolerances and deviations between individual hoist motors.

[0005] Typically, in known elevator machinery, the nominal torque constant, or KTC value, is printed on the motor plate and defined during motor type testing. Currently, drive units do not use the provided KTC value, as it has been found to be too inaccurate. Instead, a substitute is calculated based on the nominal current and power values, which in many cases leads to an even less accurate estimate of the KTC parameter. KTC is an important parameter for controlling the movement of the elevator car, as it indicates how much motor current is required to produce a certain amount of motor torque. Summary of the Invention

[0006] The object of the present invention is to provide a method, an elevator control unit, an elevator system, and a computer-readable storage medium for determining the torque constant of a hoisting motor of an elevator. Another object of the present invention is that the method, the elevator control unit, the elevator system, and the computer-readable storage medium provide a solution for determining the specific torque constant of an elevator and hoisting motor, which increases accuracy and eliminates possible errors in the parameter determination process.

[0007] The objects of the invention are achieved by a method for determining a torque constant of a hoisting motor of an elevator, an elevator control unit, an elevator system and a computer-readable storage medium as defined by the respective independent claims.

[0008] According to a first aspect, a method for determining a torque constant of a hoisting motor of an elevator system is provided. The method comprises:

[0009] - performing a round trip in an elevator hoistway by an elevator car using the hoisting motor, wherein the round trip comprises a constant speed portion in a first direction and a constant speed portion in an opposite second direction,

[0010] - determining the motor current of the hoisting motor during at least the constant speed portion, such as recording sampled values thereof,

[0011] - determining the average value of the motor current in the constant speed portion, and

[0012] - determining the torque constant based on the average value, the elevator balance and one or more mechanical parameters related to the force transmission between the hoisting motor and the elevator car.

[0013] A round trip may include only an empty portion of the elevator shaft in its longitudinal direction, or a round trip may be an empty ride between the bottom floor and the top floor, covering the entire elevator shaft.

[0014] Furthermore, elevator balance refers to a measure of the imbalance between the elevator car and its counterweight, particularly at a reference point, such as the midpoint of the elevator shaft. As a non-limiting example, if an empty elevator car were perfectly balanced with its counterweight (connected to each other via a force-transmitting element / device) at a reference point, the elevator balance would be zero. This means that the hoist motor would draw the same amount of electrical power regardless of whether the empty elevator car was moving in a first direction or in an opposite, second direction from a reference point (e.g., the midpoint of the shaft).

[0015] Regarding the constant speed portion, in the constant speed portion, the elevator car may preferably be arranged to move past the midpoint of the elevator shaft. Thus, a round trip should at least cover the portion of the elevator shaft including the midpoint, regardless of whether the round trip includes only a portion of the shaft or the entire shaft.

[0016] Alternatively or additionally, the elevator car can be arranged to move in the same section of the elevator shaft in both constant speed sections, i.e. in both directions. Thus, when moving in a first direction or in an opposite second direction, the start and end of the constant speed section are in both cases at the same position relative to the shaft.

[0017] In various embodiments, the one or more mechanical parameters may include at least the traction sheave radius and / or the elevator roping ratio. As will be appreciated, these parameters affect the overall balance condition associated with the elevator car and its counterweight and may vary from one elevator system to another.

[0018] In some preferred embodiments, the torque constant is determined based on the following equation:

[0019] ,

[0020] Where Rts is the traction sheave radius, MB is the elevator balance, g is the acceleration due to gravity, Im,mean is the average value of the motor current, and Rrope is the elevator rope ratio.

[0021] The roping ratio may refer to the length of hoisting rope that the hoisting motor must move in order to raise the elevator car the required distance.

[0022] In various embodiments, the average value of the motor current Im,mean may be determined based on the following equation:

[0023] ,

[0024] Where K is the number of motor current samples in the constant speed section, and Im,n is the motor current sampling value.

[0025] In various embodiments, information about the elevator balance can be predefined before performing a test run or even a round trip, or can be received or obtained during the test run or even a round trip. For example, the elevator balance may have been determined during a previous test run or elevator commissioning phase and then stored in memory for use in embodiments of the present invention. The previous test run or commissioning phase may have included moving the elevator car in the elevator hoistway, for example, at a constant speed, even similar to that during a round trip.

[0026] Alternatively, in various embodiments, the method can include determining the elevator balance based on data collected during the round trip. For example, the method can include determining the elevator balance based on at least a difference in electric power of the hoist motor between constant speed portions (preferably at or on average around the midpoint of the elevator hoistway) before determining the torque constant but during or after the round trip.

[0027] In some embodiments, elevator balance may be determined based on the following equation:

[0028] ,

[0029] Wherein, Pme,mid,up is the electric power of the elevator car hoisting motor during the constant speed portion in the first direction, Pme,mid,down is the electric power of the elevator car hoisting motor during the constant speed portion in the second direction, g is the acceleration due to gravity, and v_cs is the absolute value of the speed of the elevator car in the constant speed region, which may be the same as or different from the rated speed of the elevator car. Preferably, the electric power value is determined at or near the midpoint of the hoistway when the elevator car is traveling at a constant speed.

[0030] According to a second aspect, an elevator control unit is provided. The elevator control unit includes at least a processing unit and a memory, such as a processor and a non-transitory / volatile storage medium, and a data receiving unit for receiving data including information about a motor current of a hoisting motor. The elevator control unit is configured to cause an elevator car to perform a round trip in an elevator shaft using the hoisting motor, wherein the round trip includes a constant speed portion in a first direction and a constant speed portion in an opposite second direction, and is configured to determine the motor current of the hoisting motor at least during the constant speed portion, such as by recording a sampled value thereof. Furthermore, the elevator control unit is configured to determine an average value of the motor current during the constant speed portion and to determine a torque constant based on the average value, elevator balance, and one or more mechanical parameters related to force transmission between the hoisting motor and the elevator car.

[0031] The one or more mechanical parameters may include at least a traction sheave radius and / or an elevator roping ratio.

[0032] The torque constant can be determined based on the following equation:

[0033] ,

[0034] Where Rts is the traction sheave radius, MB is the elevator balance, g is the acceleration due to gravity, Im,mean is the mean value of the motor current, and Rrope is the elevator roping ratio.

[0035] In various embodiments, the elevator control unit can be configured to determine the elevator balance based on at least the difference in electric power of the hoist motor between constant speed sections, preferably at or on average around the midpoint of the elevator shaft, before determining the torque constant.

[0036] According to a third aspect, an elevator system is provided. The elevator system comprises an elevator car movable in an elevator shaft by a hoisting motor and an elevator control unit according to the second aspect (with one or more embodiments thereof).

[0037] According to a fourth aspect, there is provided a computer-readable storage medium, such as a non-transitory storage medium or device, comprising instructions which, when executed by a processing unit (such as comprising one or more processors), cause the processing unit to perform a method according to the first aspect (i.e. one or more embodiments thereof).

[0038] The present invention provides a method, an elevator control unit, an elevator system, and a computer-readable storage medium for determining the torque constant of an elevator hoist motor. The present invention offers advantages over known solutions because the specific torque constant of an elevator or hoist motor can be easily and accurately determined. Accurate torque constants are important and necessary for many purposes, such as when controlling motors, including motion control, torque-assisted brake testing, parameter estimation, and energy calculations.

[0039] Various other advantages will become apparent to the skilled person based on the following detailed description.

[0040] The expression "plurality" may refer to any positive integer starting from two (2), ie, two, at least two, three, at least three, etc.

[0041] The terms “first,” “second,” and “third” are used herein to distinguish one element from other elements and do not particularly prioritize or rank them unless explicitly stated otherwise.

[0042] The exemplary embodiments of the present invention presented herein should not be interpreted as limiting the applicability of the appended claims. The verb "comprise" is used herein as an open limitation that does not exclude the presence of unlisted features. Unless expressly stated otherwise, the features recited in the appended claims may be freely combined with each other.

[0043] The novel features which are believed to be characteristic of the invention are set forth with particularity in the appended claims.The invention itself, however, both as to its construction and its method of operation, together with additional objects and advantages thereof, will be best understood from the following description of specific embodiments when read in connection with the accompanying drawings. BRIEF DESCRIPTION OF THE DRAWINGS

[0044] Some embodiments of the invention are illustrated by way of example and not limitation in the accompanying drawings.

[0045] FIG1 shows a flow chart of a method according to an embodiment of the present invention.

[0046] Figure 2 Features of a round trip of a method according to an embodiment of the invention are schematically illustrated.

[0047] Figure 3 An elevator system according to one embodiment of the present invention is schematically illustrated. DETAILED DESCRIPTION

[0048] Figure 1A flow chart of a method according to an embodiment of the present invention is shown. Item or method step 100 refers to the start-up phase of the method. Appropriate equipment and components are obtained, and the system is assembled and configured for operation. This may mean that the elevator system is manufactured and set up, or the elevator system may be prepared for commissioning and / or test runs. Alternatively, the elevator may already be in use but (temporarily) set to maintenance mode, etc.

[0049] In various embodiments, the elevator can be configured to be in a maintenance mode prior to executing item 110. Maintenance mode differs from normal operating mode, in which the elevator car is arranged to serve landings based on elevator car calls. Maintenance mode can be initiated locally or remotely, or even automatically, by the elevator control unit when certain conditions for the maintenance mode are met.

[0050] Additionally, the method may optionally include verifying that the elevator car is empty prior to performing item 110. Verification may include visual inspection by maintenance personnel and / or utilizing sensors, such as sensors for determining the weight of the car or a load within the car, or optical sensors for determining that the elevator is empty by monitoring the interior space of the car.

[0051] Item or method step 110 is to perform a round trip in an elevator hoistway by an elevator car using a hoist motor, wherein the round trip includes a constant speed portion in a first direction and a constant speed portion in an opposite second direction. The first direction and the second direction are preferably vertical directions. The first direction can be, for example, upward, and the second direction can be downward.

[0052] In the constant speed portion, the elevator car may be arranged to move past the midpoint of the elevator shaft. In some embodiments, in the constant speed portion, the elevator car is arranged to move in the same section of the elevator shaft, therefore also including the midpoint.

[0053] A round trip may include only an empty portion of the elevator shaft in its longitudinal direction, or a round trip may be an empty ride between the bottom floor and the top floor, covering the entire elevator shaft.

[0054] Alternatively or additionally, the elevator car can be arranged to move in the same section of the elevator shaft in both constant speed sections, i.e. in both directions. Thus, when moving in a first direction or in an opposite second direction, the start and end of the constant speed section are in both cases at the same position relative to the shaft.

[0055] Item or method step 120 refers to determining the motor current of the hoist motor during at least the constant speed portion, such as by recording a sampled value thereof. For example, the motor current can be determined by an electrical converter (or a current sensor thereof) arranged to operate or drive the motor, or by a dedicated current sensor connected to the elevator control unit.

[0056] Item or method step 130 is to determine the average value of the motor current in the constant speed portion. The motor current values recorded over the two constant speed portions should be considered. For example, the average value of the motor current can be determined based on the following equation:

[0057] ,

[0058] where K is the number of samples of the motor current Im,n during the two constant speed sections.

[0059] Item or method step 140 refers to determining a torque constant based on the average value, the elevator balance and one or more mechanical parameters related to the force transmission between the hoist motor and the elevator car.

[0060] Elevator balance can refer to a measure of the imbalance between an elevator car and its counterweight, particularly at a reference point, such as the midpoint of an elevator hoistway. As a non-limiting example, if an empty elevator car were perfectly balanced with its counterweight (connected to each other via a force-transmitting element / device) at a reference point, the elevator balance would be zero. This means that the hoist motor would draw the same amount of electrical power regardless of whether the empty elevator car was moving in a first direction or an opposite, second direction from a reference point (e.g., the midpoint of the hoistway).

[0061] In various embodiments, the method may include, at item 132, determining the elevator balance prior to item 140. For example, it may be received or obtained as predefined in the system, or it may be determined based on data collected during a separate, previous test run or during the round trip at item 110.

[0062] In this method, the characteristics of the mechanical coupling between the hoisting motor and the elevator car are preferably taken into account. As can be understood, in different elevators, the force applied by the hoisting motor to move the elevator car results in different resulting movements of the car, depending on, among other things, the mechanical parameters of the specific elevator.

[0063] In some embodiments, the mechanical parameters may include at least the traction sheave radius Rts and the elevator roping ratio Rrope. These may optionally be calculated before determining the torque constant. Figure 1 Defined, obtained or received at item 134 in.

[0064] In some embodiments, the determined torque constant may be based on the following equation:

[0065] ,

[0066] Where Rts is the traction sheave radius, MB is the elevator balance, g is the acceleration due to gravity, Im,mean is the mean value of the motor current, and Rrope is the elevator rope ratio.

[0067] Method execution may be stopped at item 199. The determined torque constant may be input or stored into a memory and optionally used to control operation of the hoist motor, such as via an electrical converter, which may be a frequency converter. As previously described, the determined torque constant may be used for a variety of purposes.

[0068] In some embodiments, the method may include, before determining the torque constant, determining the elevator balance based at least on a difference in electric power of the hoist motor between constant speed portions, preferably at or on average around a midpoint of the elevator hoistway.

[0069] For example, elevator balance can be determined based on the following equation:

[0070] ,

[0071] where Pme,mid,up is the electric power of the hoisting motor during the constant speed portion in the first direction, Pme,mid,down is the electric power of the hoisting motor during the constant speed portion in the second direction, g is the acceleration due to gravity, and v_cs is the absolute value of the elevator car's velocity in the constant speed region.

[0072] Figure 2 The characteristics of a round trip in connection with a method according to an embodiment of the invention are schematically illustrated. Figure 2 A round trip is shown as a graph with time in seconds on the horizontal axis, the elevator car's speed in meters per second on the left vertical axis, and the elevator car's position in the elevator shaft on the right vertical axis. The position can be in meters, for example relative to the bottom floor (zero), or a floor number, etc.

[0073] exist Figure 2 , the speed curve is marked with reference numeral 20. On the speed curve 20, two constant speed portions 21, 22 are indicated between vertical lines. The position curve is marked with reference numeral 25. A positive value of the speed indicates that the elevator car is moving in a first direction, preferably upwards. A negative value of the speed indicates that the elevator car is moving in an opposite second direction, preferably downwards.

[0074] The center point H0 of the elevator shaft is marked with a circle on the position curve 25. In this graph, the center point of the shaft coincides with zero speed, as can be seen in the graph. This is simply a choice to make the graph as easy to read as possible.

[0075] In this particular example, an embodiment is described in which the elevator car covers substantially the same section of the elevator hoistway during the two constant speed portions 21, 22, which becomes clear when observing the portion of the position curve 25 defined by the vertical line that also defines the constant speed portions 21, 22 on the speed curve 20. Furthermore, the midpoint H0 of the elevator hoistway is (although not necessarily) located substantially in the center of the section of the hoistway covered by the elevator car during the constant speed portions 21, 22.

[0076] In addition, Figure 2 , an example of an elevator car moving from the bottom floor (coinciding with "-3" on the left vertical axis) to the top floor (coinciding with "3" on the right vertical axis) is shown. In some embodiments, the height of the shaft may be in the range of 5 to 100 meters, preferably 10 to 80 meters, for example about 60 meters.

[0077] As in Figure 2 As can be further seen in Figure 2, during a round trip, the elevator car may additionally stop for one or more periods of time (with a speed of zero) at some parts of the round trip, such as at the extreme points of the round trip (e.g., at the bottom-most and top-most floors). These stop portions do not qualify as constant speed portions, since the absolute value of the speed v_cs of the elevator car must be above zero during the constant speed portion.

[0078] Figure 3 An elevator system 300 according to an embodiment of the present invention is schematically illustrated. The elevator system 300 includes a hoist motor 302, such as a permanent magnet electric motor, for moving an elevator car 310 included in the elevator system 300. The elevator car 310 can preferably be mechanically coupled to the electric motor 302 via hoist ropes 306. The operation of the electric motor 302 can be controlled by an electrical converter 304, such as a frequency converter or inverter. In a normal operating mode, the elevator car 310 moves in an elevator hoistway 340 to serve landings 350.

[0079] The lifting rope 306 may comprise, for example, steel or carbon fiber. The term "lifting rope" does not limit the form of the element in any way. For example, the lifting rope 306 may be implemented as a rope or a belt.

[0080] The hoisting motor 302 may be arranged to be mechanically coupled to the traction sheave 308. Furthermore, the hoisting ropes 304 may be arranged to travel via the traction sheave 308 so that the hoisting motor 302 can move the elevator car 310 coupled to the hoisting ropes 302. Furthermore, connected to the hoisting ropes 302 may preferably be a counterweight 314 for the elevator car 310. Although in Figure 3 3. The hoisting rope 306 is shown as being attached from one end to the elevator car 310 and from the opposite end to the counterweight 314, and then simply running through the traction sheave 308, but in practice, the hoisting rope 306 can run through one or more other pulleys and components, as known to those skilled in the art. Thus, depending on how the hoisting rope 306 is arranged to run, e.g., through how many pulleys and how this configuration is designed and arranged, the roping ratio can be different from one elevator system 300 to another.

[0081] The elevator system 300 may include an elevator control unit 1000 for controlling the operation of the elevator system 300, for example, various devices of the elevator system 300. The elevator control unit 1000 may be a separate device, or may be included in other components of the elevator system 300, such as in or as part of the power converter 304. In various embodiments, the elevator control unit 1000 includes the power converter 304.

[0082] The elevator control unit 1000 can also be implemented in a distributed manner, so that, for example, a part of the elevator control unit 1000 can be included in the electrical converter 304 and another part in the elevator car 310. The elevator control unit 1000 can also be arranged in a distributed manner at more than two locations or in more than two devices. Figure 3 As can be seen in FIG. 1 , the elevator control unit 1000 may be arranged to communicate with at least various devices of the elevator system 300 (examples of such connections are shown with dashed double-headed arrows).

[0083] The elevator system 300 may include an elevator braking device 312 including an elevator brake, preferably an electromechanical elevator brake.

[0084] Figure 3 Other elements shown in FIG. 3 are a main power source 325 (such as a three-phase or single-phase electrical grid), an electrical connection 330 between the power source 325 and the electrical converter 304 , and another electrical connection 335 between the electrical converter 304 and the electric motor 302 .

Claims

1. A method for determining a torque constant of a hoist motor (302) of an elevator system (300), the method comprising: causing an elevator car (310) to perform a round trip (110) in an elevator hoistway (340) using a hoist motor (302), wherein the round trip comprises a constant speed portion (21) in a first direction and a constant speed portion (22) in an opposite second direction, determining (120) a motor current of the hoist motor (302) at least during the constant speed portion, for example recording a sampled value thereof, determining (130) the average value of the motor current during the constant speed portion (21, 22), and A torque constant is determined (140) based on the average value, the elevator balance, and one or more mechanical parameters related to force transmission between the hoist motor (302) and the elevator car (310).

2. The method according to claim 1, wherein In the constant speed section (21, 22), the elevator car (310) is set to pass through the middle point (H0) of the elevator shaft (340).

3. The method according to claim 2, wherein In the constant speed portion (21, 22), the elevator car (310) is arranged to move within the same section of the elevator shaft (340).

4. The method according to any one of claims 1 to 3, wherein The mechanical parameters include at least the traction sheave radius (Rts) and the elevator roping ratio.

5. The method according to any one of claims 1 to 4, wherein The elevator balance is a measure of the degree of imbalance between the elevator car (310) and its counterweight (314).

6. The method according to any one of claims 1 to 5, wherein The determination of the torque constant, KTC, is based on the following equation: ， Where Rts is the traction sheave radius, MB is the elevator balance, g is the acceleration due to gravity, Im,mean is the average value of the motor current, and Rrope is the elevator rope ratio.

7. The method according to any one of claims 1 to 6, wherein: The average value of the motor current, Im,mean, is determined based on the following equation: ， where K is the number of samples of the motor current Im,n during the constant speed portion (21, 22).

8. Method according to any one of claims 1 - 7, before determining (140) the torque constant, determining the elevator balance based on at least the difference in electric power of the hoisting motor (302) between the constant speed sections (21, 22), preferably at or near the midpoint (H0) of the elevator shaft (340).

9. The method according to claim 8, wherein The elevator balance, or MB, is determined based on the following equation: ， where Pme,mid,up is the electric power of the hoisting motor in the constant speed portion in the first direction, Pme,mid,down is the electric power of the hoisting motor in the constant speed portion in the second direction, g is the acceleration due to gravity, and v_cs is the absolute value of the elevator car velocity in the constant speed region.

10. An elevator control unit (1000), comprising at least a processing unit and a memory, such as a processor and a non-transitory storage medium, and a data receiving unit for receiving data including motor current information of a hoisting motor (302), wherein the elevator control unit (1000) is configured to: causing an elevator car to perform (110) a round trip in an elevator hoistway using a hoisting motor, wherein the round trip comprises a constant speed portion (21) in a first direction and a constant speed portion (22) in an opposite second direction, determining (120) a motor current of the hoisting motor (302) at least during the constant speed portion (21, 22), for example recording a sampled value thereof, Determine (130) the average value of the motor current during the constant speed portion (21, 22), and A torque constant is determined (140) based on the average value, the elevator balance, and one or more mechanical parameters related to force transmission between the hoist motor (302) and the elevator car (310).

11. The elevator control unit (1000) according to claim 10, wherein: The mechanical parameters include at least the traction sheave radius (Rts) and the elevator roping ratio.

12. The elevator control unit (1000) according to claim 11, wherein: The determination of the torque constant, KTC, is based on the following equation: ， where Rts is the traction sheave radius, MB is the elevator balance, g is the acceleration due to gravity, Im,mean is the mean value of the motor current, and the elevator roping ratio.

13. An elevator control unit (1000) according to any one of claims 10 - 12, configured to determine the elevator balance before determining (140) the torque constant based on at least the difference in electric power of the hoisting motor (302) between the constant speed sections (21, 22), preferably at or near the average of the midpoint (H0) of the elevator shaft (340).

14. An elevator system (300), comprising: an elevator car (310) movable in an elevator hoistway (340) by a hoist motor (302), and An elevator control unit (1000) according to any one of claims 10 to 13.

15. A computer-readable storage medium comprising instructions which, when executed by a processing unit, such as a computer comprising one or more processors, cause the processing unit to perform the method according to any one of claims 1 to 9.

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