METHOD FOR DETECTING A HEAT SITUATION IN A LIFT SYSTEM, CONTROL DEVICE FOR A LIFT SYSTEM, LIFT SYSTEM, COMPUTER PROGRAM AND COMPUTER-READABLE MEDIUM

Description

[0001] The present invention relates to a method for detecting a jam situation in an elevator installation. Furthermore, the invention relates to a control device for the elevator installation, a computer program, and a computer-readable medium for executing such a method. Furthermore, the invention relates to an elevator installation equipped with such a control device.

[0002] Fig. 1shows a typical elevator system 20, such as a passenger or freight elevator. Such an elevator system 20 typically comprises an elevator shaft 22, a car 24, a counterweight 26, an electric motor 30 having a traction sheave 32, suspension means 28, and a brake 34, which can be located on the axis of the electric motor 34 or on the car. The suspension means 28 can, for example, comprise one or more ropes, belts, or straps. For the sake of simplicity, the suspension means 28 will be used in the singular below. However, it should be noted that this does not preclude the presence of two or more suspension means 28. The elevator car 24 is arranged so as to be vertically displaceable in the elevator shaft 22. The counterweight 26 is connected to the elevator car 24 via the suspension means 28. The traction sheave 32 is rotatable by means of the electric motor 30.The support means 28 runs over the traction sheave 32 and optionally over a deflection pulley 33 and is movable by means of the traction sheave 32, so that the car 24 and the counterweight 26 can be vertically displaced by operating the electric motor 30 in cooperation with the support means 28. The brake 34 enables the car 24 to be decelerated and / or immobilized. Alternatively or additionally, a further brake can be arranged for decelerating and / or immobilizing the counterweight 26. A control device 40 is communicatively coupled to the electric motor 30 and / or the brake 34 for controlling the electric motor 30 and / or the brake 34.

[0003] A load 46 can be introduced into or removed from the elevator car 24 via a first access 36 on a first floor. The load 46 can be introduced into or removed from the elevator car 24 via a second access 38 on a second floor above the first floor. The load 46 can stand in the elevator car 24 on a floor 44 of the elevator car 24, wherein a weight sensor 42 for detecting a weight of the load 46 can be arranged on the floor 44. The load 46 can be transported by means of the elevator car 24 from the first floor to the second floor or from the second floor to the first floor. Furthermore, further floors and corresponding accesses (not shown) can be provided, which can be reached by means of the elevator car 24.

[0004] When the elevator car 24 is moved vertically, due to the coupling between the elevator car 24 and the counterweight 26 by means of the support means 28, the counterweight 26 is also moved vertically, in the opposite direction to the elevator car 24. This can happen that either the elevator car 24 or the counterweight 26 gets stuck. In general, four different stuck situations can occur. A first stuck situation refers to a dynamic stuckness of the elevator car 24. In this case, the elevator car 24 initially moves and then gets stuck. A second stuck situation refers to a statistical stuckness of the elevator car 24. In this case, the elevator car 24 gets stuck before it can be set in motion. A third stuck situation refers to a dynamic stuckness of the counterweight 26. In this case, the counterweight 26 initially moves and then gets stuck.A fourth jamming situation refers to a statistical jamming of the counterweight 26. In this case, the counterweight 26 remains stuck before it can be set in motion.

[0005] If, for example, the elevator car 24 becomes stuck, the counterweight 26 may initially be raised further due to the friction between the suspension element 28 and the traction sheave 32. As soon as this friction is no longer sufficient to further raise the counterweight 26, the counterweight 26 drops until the suspension element 28 is tensioned again. This can transfer large forces to the suspension element 28 and, via the suspension element 28, to the elevator car 24, which can damage or injure the car and / or loads, such as persons, in the elevator car 24.

[0006] If, for example, the counterweight 26 gets stuck, the elevator car 24 may initially be raised further due to the friction between the suspension element 28 and the traction sheave 32. As soon as this friction is no longer sufficient to further raise the elevator car 24, the elevator car 24 falls until the suspension element 28 is tensioned again.

[0007] In this case, large forces can be transmitted to the support element 28 and, via the support element 28, to the counterweight 26, causing damage. Furthermore, loads, such as persons, in the car 24 can be damaged or injured due to the falling of the car 24.

[0008] It is known to prevent such exclusive lifting of the counterweight 26 or the car 24 by designing the traction sheave 32 and / or the support means 28 such that, if the car 24 or the counterweight 26 becomes stuck, it slides over the traction sheave 32 and no longer lifts the counterweight 26 or the car 24. Furthermore, it is known to alternatively or additionally arrange an electronic safety device, also referred to as KSS or KSS1, which is designed to detect when the tension of the support means 28 on the side of the car 24 or the counterweight 26 decreases to such an extent that the support means 28 is slack on the corresponding side.However, due to the great danger that can arise if the stuck situations are not detected or not detected in time, it would be desirable to provide an additional safety function and / or to integrate the safety function into the control device 40 of the elevator system 20, independently of the aforementioned electronic safety device KSS / KSS1.

[0009] Methods for detecting a stuck situation are known from US2020283259A1 and US2015114761A1.

[0010] There may therefore be a need for an alternative or additional method for detecting a stuck situation in an elevator installation. In particular, there may be a need for a method by which the stuck situation is reliably and quickly detected and / or that can be implemented in a control device of the elevator installation. Furthermore, there may be a need for the control device, a computer program product, and a computer-readable medium for executing the method, as well as for an elevator installation equipped with such a control device.

[0011] Such a need may be met by the subject matter of one of the independent claims. Advantageous embodiments are defined in the dependent claims and in the following description.

[0012] A first aspect of the invention relates to a method for detecting a jam situation in an elevator system. The elevator system comprises an elevator shaft, a car arranged in the elevator shaft, a counterweight coupled to the car via a support means, an electric motor having a traction sheave rotatable by means of the electric motor, over which the support means runs, and by means of which the support means is movable, so that the elevator car and the counterweight can be vertically displaced by operating the electric motor, and a brake by means of which the elevator car and / or the counterweight can be braked and / or locked.The method comprises: receiving a load signal representative of the weight of a load located in the elevator car and to be transported by the elevator car; determining a pre-torque as a function of the load signal; receiving a speed signal representative of the actual speed of the elevator car; monitoring a correction torque over a predetermined monitoring period, wherein the correction torque is determined as a function of the speed signal and a predetermined reference speed such that the actual speed of the elevator car approaches the reference speed; detecting a stuck situation in which the elevator car or the counterweight becomes stuck in the elevator shaft if the monitored corrective torque meets at least one predetermined criterion; and implementing a predetermined safety measure upon detection of the stuck situation.

[0013] The method can, for example, be carried out automatically by a processor of the control device of the elevator system.

[0014] In summary, the method described here and below, in particular the monitoring of the correction torque and the detection of the stuck situation when the monitored correction torque meets the specified criterion, enables a reliable and / or rapid detection of all possible stuck situations and can be implemented easily and / or with little effort in a control device for controlling the electric motor of the elevator system.

[0015] A particularly advantageous feature is that, from a technical perspective, no separate electronic safety device is required to detect the jammed condition. However, the method can optionally be implemented in a separate electronic safety device, which can be arranged in addition to and / or independently of the control device of the elevator system.

[0016] Possible features and advantages of embodiments of the invention may be considered, among other things and without limiting the invention, to be based on ideas and findings described below.

[0017] The load signal can be generated by a sensor, for example, by the weight sensor 42 in the floor 44 of the car 24, and received by the control device, e.g., the control device 40. Alternatively, the load signal can be determined by determining a difference between a weight hanging on one side of the traction sheave, from which the counterweight hangs, and a weight hanging on one side of the traction sheave, from which the car hangs. Since the weight of the car, the weight of the counterweight, the position of the car, and a specific weight of the support means are known, this difference is representative of the weight of the load and can be encoded in the load signal.

[0018] The speed signal can be generated by a speed sensor, e.g., an encoder comprising, for example, a magnet and a magnetic sensor, which detects the speed of the electric motor or the traction sheave, and received by the control device. The reference speed can be determined and / or specified by the control device; for the sake of simplicity, it is assumed below that the reference speed is specified by the control device.

[0019] The aforementioned stuck situations can be divided into different stuck cases, whereby a distinction is made between the different stuck cases as to whether there is a load in the car.

[0020] Fig. 2 shows eight different stuck cases, each of which falls under one of the aforementioned stuck situations. In particular, Figure 2four different jamming scenarios 1 to 4 with the car 24 empty and four different jamming scenarios 5 to 8 with the car 24 loaded with the load 46. Furthermore, a distinction is made in the jamming scenarios as to the direction in which the traction sheave 32 rotates; the arrows drawn above the traction sheaves 32 indicate a direction of rotation of the traction sheave 32 (counterclockwise for jamming scenarios 1, 2, 5, and 6; clockwise for jamming scenarios 3, 4, 7, and 8). Furthermore, a distinction is made in the jamming scenarios as to whether the car 24 (in jamming scenarios 1, 3, 5, and 7) or the counterweight 26 (in jamming scenarios 2, 4, 6, and 8) remains stuck.

[0021] In jamming case 1, the elevator car 24 is intended to be moved downwards but remains stuck. If the traction sheave 32 is rotated further, the counterweight 26 can be raised further, the suspension element 28 can lose tension on the car 24 side, and at a later point in time, the counterweight 26 can fall uncontrollably downwards into the suspension element 28. In this case, before jamming, a first motor axle torque TM, which is applied by the electric motor 30 to lower the elevator car 24, is equal to a negative second torque TME, the negative system torque. After jamming, the first torque TM is much smaller than the negative second torque TME, since the electric motor 30 must now continue to raise the counterweight 26 without the support of the weight of the elevator car 24. The application torque is the maximum torque required by the system during constant travel. This occurs when the car is full or, alternatively, when the car is empty.The worst case scenario regarding car position, rope weight and friction in the system is taken into account.

[0022] In jamming case 2, the elevator car 24 is to be moved downward, but the counterweight 26 remains stuck. The support element 28 cannot be moved any further, which is why the elevator car 24 cannot be moved any further downward. In this case, before the jamming, the first torque TM is equal to the negative second torque TME. After the jamming, the first torque TM is much smaller than the negative second torque TME, since the electric motor 30 attempts to lift the blocked counterweight 26.

[0023] In jamming case 3, the elevator car 24 is intended to be moved upward, but remains stuck. The support element 28 cannot be moved any further, which is why the counterweight 26 cannot be moved any further downward. In this case, before jamming, the first torque TM is equal to the negative second torque TME. After jamming, the first torque TM is much greater than the positive second torque TME, since the electric motor 30 attempts to raise the blocked elevator car 24.

[0024] In jamming case 4, the elevator car 24 is to be moved upward, but the counterweight 26 remains stuck. If the traction sheave 32 is rotated further, the elevator car 24 can be raised further, the support element 28 can lose tension on the counterweight 26 side, and at a later point in time, the elevator car 24 can fall uncontrollably downward into the support element 28. In this case, before jamming, the first torque TM is equal to the negative second torque TME. After jamming, the first torque TM is much greater than the positive second torque TME, since the electric motor 30 must now continue to lift the elevator car 24 without the support of the counterweight 26.

[0025] In jamming case 5, the elevator car 24 with the load 46 is to be moved downwards, but remains stuck. If the traction sheave 32 is rotated further, the counterweight 26 can be raised further, the support element 28 can lose tension on the side of the elevator car 24, and at a later point in time, the counterweight 26 can fall uncontrollably downwards into the support element 28. In this case, before jamming, the first torque TM is equal to the positive second torque TME. After jamming, the first torque TM is much smaller than the negative second torque TME, since the electric motor 30 must now continue to lift the counterweight 26 without the support of the weight of the elevator car 24 and the load 46.

[0026] In jamming case 6, the elevator car 24 with the load 46 is to be moved downward, but the counterweight 26 remains stuck. The support element 28 cannot be moved any further, which is why the elevator car 24 cannot be moved any further downward. In this case, before jamming, the first torque TM is equal to the positive second torque TME. After jamming, the first torque TM is much smaller than the negative second torque TME, since the electric motor 30 attempts to lift the blocked counterweight 26.

[0027] In jamming case 7, the elevator car 24 with the load 46 is supposed to be moved upward, but it remains stuck. The support element 28 cannot be moved any further, which is why the counterweight 26 cannot be moved any further downward. In this case, before jamming, the first torque TM is equal to the positive second torque TME. After jamming, the first torque TM is much greater than the positive second torque TME, since the electric motor 30 attempts to lift the blocked elevator car 24 and the load 46.

[0028] In jamming case 8, the elevator car 24 with the load 46 is to be moved upwards, but the counterweight 26 remains stuck. If the traction sheave 32 is rotated further, the elevator car 24 can be raised further, the support element 28 can lose tension on the counterweight 26 side, and at a later point in time, the elevator car 24 can fall uncontrollably downwards into the support element 28. In this case, before jamming, the first torque TM is equal to the positive second torque TME. After jamming, the first torque TM is much greater than the positive second torque TME, since the electric motor 30 must now continue to lift the elevator car 24 and the load 46 without the support of the counterweight 26.

[0029] This means that Figure 2It is clear that in all jamming cases, and thus also in all jamming situations, the amount of torque that the electric motor must apply to achieve the desired acceleration and / or speed increases rapidly and sharply—in other words, abruptly. This can be reliably and quickly detected, for example, by monitoring the correction torque. Thus, all jamming situations can be reliably and quickly detected using the aforementioned method.

[0030] A second aspect of the invention relates to a control device having a processor configured to execute the method according to an embodiment of the first aspect of the invention. The control device can be part of the elevator installation or part of a stand-alone safety device for the elevator installation, in addition to the normal elevator control. The control device can comprise hardware and / or software modules. In addition to the processor, the control device can comprise a memory and data communication interfaces for data communication with peripheral devices. Features of the method according to an embodiment of the first aspect of the invention can also be features of the control device, and vice versa.

[0031] A third aspect of the invention relates to an elevator system, for example, a freight or passenger elevator. The elevator system comprises an elevator shaft, a car arranged in the elevator shaft, a counterweight arranged in the elevator shaft and coupled to the car via a support means, an electric motor having a traction sheave rotatable by means of the electric motor, over which the support means runs, and by means of which the support means is movable, so that the car and the counterweight can be vertically displaced by operating the electric motor, a brake by means of which the car and / or the counterweight can be braked and / or locked, and a control device according to an embodiment of the second aspect of the invention.

[0032] A fourth aspect of the invention relates to a computer program comprising instructions which, when the computer program is executed by the processor, cause a processor to carry out the method according to an embodiment of the first aspect of the invention.

[0033] A fifth aspect of the invention relates to a computer-readable medium on which the computer program according to an embodiment of the fourth aspect of the invention is stored. The computer-readable medium may be a volatile or non-volatile data storage device. For example, the computer-readable medium may be a hard disk, a USB storage device, a RAM, ROM, EPROM, or flash memory. The computer-readable medium may also be a data communications network enabling a download of program code, such as the Internet or a data cloud.

[0034] Features of the method according to an embodiment of the first aspect of the invention may also be features of the computer program and / or the computer-readable medium and vice versa.

[0035] According to one embodiment, when monitoring the correction torque, a maximum correction torque and a minimum correction torque are determined within a predetermined period of time, wherein the predetermined criterion is met if a difference between the maximum correction torque and the minimum correction torque is greater than a predetermined threshold value.

[0036] Determining the difference and comparing it with the specified threshold value makes it easy to detect the jamming situation. In particular, this monitoring can reliably detect all possible jamming situations and jamming cases mentioned above, as explained in more detail below. The period during which the minimum and maximum correction torque and the corresponding difference are determined can be referred to, for example, as the monitoring period or time window. Since monitoring can run continuously, the time window can be sliding. In this context, the time window can also be referred to as a sliding window or monitoring window.

[0037] According to one embodiment, a total torque is determined based on the pre-torque and the correction torque, and at least one reference current for operating the electric motor is determined based on the total torque. Determining the reference current based on the pre-torque and the correction torque can easily contribute to moving the elevator car at the desired speed and / or comfortably, i.e., with little or no jerking. The total torque can, for example, be the sum of the pre-torque and the correction torque.

[0038] According to one embodiment, the pre-torque comprises a load torque and an acceleration torque. Determining the pre-torque based on the load torque and the acceleration torque can help ensure that the car moves smoothly and / or without jerking, especially during start-up. The pre-torque can, for example, be the sum of the load torque and the acceleration torque.

[0039] According to one embodiment, the load torque is determined in such a way that, when the brake is released, the elevator car does not move based solely on the determined load torque. Thus, if the load torque were applied exclusively by the electric motor, the elevator car would not move when the brake was released. This can contribute to the smooth and / or jerk-free movement of the elevator car, especially when starting off.

[0040] According to one embodiment, the load signal is representative of a difference between a weight hanging on one side of the traction sheave, from which the counterweight hangs, and a weight hanging on one side of the traction sheave, from which the car hangs. The load torque is determined based on the load signal. The load torque can also be determined based on a traction sheave diameter, a gear ratio, and a reeving factor (also called a rope reversal factor). Since the weight of the car, the weight of the counterweight, the position of the car, and a specific weight of the support means are known, this difference is representative of the weight of the load and can be encoded in the load signal.

[0041] According to one embodiment, the acceleration torque is determined such that the car moves at a reference acceleration due to the acceleration torque. It can be assumed that the acceleration torque is not required to maintain the car's speed, since the load torque is sufficient for this purpose. The acceleration torque thus refers exclusively to the portion of the total torque, in particular the pre-torque, that is required to keep the car moving at a constant accelerated speed. The reference acceleration can be determined and / or specified by the control device.

[0042] According to one embodiment, a current moment of inertia is determined, which is representative of the current mass inertia of the elevator system. The acceleration torque is determined based on the current moment of inertia and a reference acceleration. The acceleration torque can also be determined based on the traction sheave diameter, the transmission ratio, and the reeving factor. The current moment of inertia depends on the load of the elevator car. The load can be generated by a sensor, e.g., a weight sensor in the floor of the elevator car, and received by the control device.

[0043] According to one embodiment, the specified safety measure comprises stopping the electric motor and / or generating an error message. Stopping the electric motor simply contributes to preventing the counterweight from being raised further if the elevator car becomes stuck, or to ensuring that the elevator car continues to be raised if the counterweight becomes stuck. Generating the error message makes it possible to log one or more stuck situations and, if necessary, to determine whether a system error exists.

[0044] According to one embodiment, monitoring of the correction torque is started when at least one predefined start condition is met. This can help prevent safety measures related to the stuck situation from being triggered in situations where a stuck situation cannot occur or where the occurrence of the stuck situation is uncritical.

[0045] According to one embodiment, the start condition includes determining the correction torque at least twice in succession and meeting the specified criterion in both determinations. In other words, monitoring can be started without delay, but the stuck situation is only detected when the specified criterion is met the second time. Alternatively, but technically equivalent, monitoring can only be started after the specified criterion is met for the first time. Alternatively or additionally, the start condition can include the reference speed being non-zero. Alternatively or additionally, the start condition can include a specified start-up time having elapsed after the start of a car travel.These starting conditions can be used individually or in any combination to prevent a jerk of the car at the beginning of a travel, which can cause a sudden change in the correction torque, from being mistakenly interpreted as a stuck situation.

[0046] Embodiments of the invention are described below with reference to the accompanying drawings, wherein neither the drawings nor the description are to be construed as limiting the invention. Fig. 1 shows an elevator system according to an embodiment of the invention. Fig. 2 shows a table illustrating various stuck cases. Fig. 3 shows a control device according to an embodiment of the invention. Fig. 4 shows an example of a torque difference between a maximum correction torque and a minimum correction torque. Fig. 5shows a flowchart of a method according to an embodiment of the invention.

[0047] The figures are merely schematic and not to scale. The same reference numerals designate identical or equivalent features in the various figures.

[0048] Fig. 1 shows an elevator installation 20, as described above in the introduction. The elevator installation 20 has an elevator shaft 22, a car 24, a counterweight 26, an electric motor 30 having a traction sheave 32, support means 28, optionally a deflection pulley 33, a brake 34, and a control device 40 for controlling the electric motor 30. In the car 24 is a load 46, which is to be transported by means of the car 24. In a floor 44 of the car 24, a weight sensor 42 for detecting a weight (or difference in weight, also UB) (see Figure 3 ) of the load 46.

[0049] Fig. 2shows the table explained above, which illustrates the various possible jamming situations. Figure 2 It emerges, among other things, that in all stuck cases and thus also in all stuck situations that include the stuck cases, the amount of torque that the electric motor must generate in order to achieve the desired acceleration and / or speed increases sharply.

[0050] Fig. 3shows a control device 40 according to an embodiment of the invention. The control device 40 serves to control the electric motor 30 depending on the weight of the load 46, a predetermined reference acceleration ak_ref, and a predetermined reference speed vk_ref, so that the elevator car 24 moves at the predetermined reference acceleration ak_ref and at the predetermined reference speed vk_ref. Furthermore, the control device 40 serves to quickly and reliably detect a jam situation in which either the elevator car 24 or the counterweight 26 becomes stuck in the elevator shaft 22. Figure 3Only those components of the control device 40 that are relevant for executing the method for detecting the stuck situation are shown. In fact, the control device 40 may include additional components, which, however, are not shown in the figures in order not to unnecessarily obscure the subject matter of the present invention.

[0051] The control device 40 includes an acceleration torque determiner 50, a load torque determiner 52, a speed torque determiner 54, a torque limiter 56, a reference current determiner 58, a sliding window determiner 60, and a comparator 62.

[0052] The acceleration torque determiner 50 determines an acceleration torque TM_REF_ACCEL based on the specified reference acceleration ak_ref and a current mass moment of inertia IA_ACTUAL, which is representative of the current mass inertia of the elevator system 20. The current mass moment of inertia IA_ACTUAL depends, among other things, on the load 46, which can be determined using the weight sensor 42 in the floor 44 of the driver's cabin 24. The acceleration torque determiner 50 determines the acceleration torque TM_REF_ACCEL, in particular, such that the elevator car 24 moves at the reference acceleration ak_ref due to the acceleration torque TM_REF_ACCEL. The acceleration torque TM_REF_ACCEL can be determined, for example, using the following formula: TM _ REF _ ACCEL = 2 ⋅ KZU ⋅ IW DD ⋅ IA _ ACTUAL ⋅ ak _ ref with a traction sheave diameter DD, a reeving factor KZU, and a transmission ratio IW. The current moment of inertia IA_ACTUAL can be defined as follows: IA _ ACTUAL = IA _ Para − GQ ⋅ 1 − KG 100 − unbalance ⋅ DD 2 2 KZU ⋅ IW 2

[0053] IA_Para is an inverter parameter representative of the total inertia of the elevator system at full payload. KG is a balancing factor that indicates the percentage of the car mass for which the counterweight mass is designed. GQ is the permissible total weight.

[0054] The load torque detector 52 uses a first load signal to determine a load torque TM_REF_LOAD such that, when the brake 34 is released, the elevator car 24 does not move based solely on the determined load torque TM_REF_LOAD. The load torque TM_REF_LOAD can be determined, for example, using the following formula: TM _ REF _ LOAD = g ⋅ DD 2 ⋅ KZU ⋅ IW ⋅ UB with the gravitational constant g. The load signal is representative of a difference UB between a weight hanging on one side of the traction sheave 32 from which the counterweight 26 hangs and a weight hanging on one side of the traction sheave 32 from which the car 24 hangs. It should be noted that the weight hanging on the side of the traction sheave 32 from which the counterweight 26 hangs also includes the weight of the support means 28 which extend at the corresponding time from the counterweight 26 to the reversing pulley 33, and that the weight hanging on one side of the traction sheave 32 from which the car 24 hangs also includes the weight of the support means 28 which extend at the corresponding time from the car 24 to that of the traction sheave 32.Since the weight of the car 24 and the counterweight 26, the specific weight of the support means 28, and the current position of the car 24 are known, the weight of the load 46 can be determined based on the difference UB. In other words, the difference UB is representative of the load 46.

[0055] The acceleration torque TM_REF_ACCEL and the load torque TM_REF_LOAD are added to a pre-torque TM_REF_FF.

[0056] The speed torque determiner 54 determines a correction torque TM_REF_PID depending on the reference speed vk_ref and an actual speed vk_act of the car 24. In particular, the speed torque determiner 54 determines the correction torque TM_REF_PID depending on a difference between the reference speed vk_ref and the actual speed vk_act of the car 24. For example, the speed torque determiner 54 can have an assignment rule, an assignment table, and / or an assignment function by means of which a correction torque TM_REF_PID is uniquely assigned to a predetermined difference between the reference speed vk_ref and the actual speed vk_act. The correction torque TM_REF_PID is determined such that the car moves at the reference speed vk_ref or at least approaches the reference speed vk_ref.

[0057] The correction torque TM_REF_PID is added to the pre-torque TM_REF_FF, resulting in a total torque TM_REF_SUM. Reference currents for controlling the electric motor are generated from TM_REF_SUM.

[0058] The sliding window detector 60 determines within a predetermined period of time, which can be represented, for example, by a sliding window T mon (see Figure 4 ), depending on the correction torque TM_REF_PID, a maximum correction torque TM_REF_PID_STALLING_MAX and a minimum correction torque TM_REF_PID_STALLING_MIN. By subtracting the minimum correction torque TM_REF_PID_STALLING_MIN from the maximum correction torque TM_REF_PID_STALLING _MAX, a torque difference TM_REF_PID_STALLING between the maximum correction torque TM_REF_PID_STALLING_MAX and the minimum correction torque TM_REF_PID_STALLING_MIN can be determined.

[0059] The comparator 62 compares the torque difference TM_REF_PID_STALLING with a predetermined threshold value TM_CHANGE_LIMIT and outputs a signal representative of the occurrence of a stuck situation if the torque difference TM_REF_PID_STALLING is greater than a predetermined threshold value TM_CHANGE_LIMIT, and outputs a signal representative of normal operation if the torque difference TM_REF_PID_STALLING is smaller than the threshold value TM_CHANGE_LIMIT.

[0060] Fig. 4 shows an example of the torque difference TM_REF_PID_STALLING between the maximum correction torque TM_REF_PID_STALLING_MAX and the minimum correction torque TM_REF_PID_STALLING_MIN. Furthermore, Figure 4The sliding window T mon, which is representative of the time period within which the torque difference TM_REF_PID_STALLING is determined as a function of the maximum correction torque TM_REF_PID_STALLING _MAX and the minimum correction torque TM_REF_PID_STALLING_MIN. As soon as the torque difference TM_REF_PID_STALLING is greater than the threshold value TM_CHANGE_LIMIT, the stuck state of the car 24 or the counterweight 26 is detected, thus indicating the presence of a stuck state.

[0061] Fig. 5 shows a flowchart of a method according to an embodiment of the invention. The method serves to reliably and quickly detect the stuck situations described above. The method can be processed, for example, by the control device 40.

[0062] In a step S2, the load signal is received which is representative of the weight of the load 46 which is located in the elevator car 24 and which is to be transported by means of the elevator car 24.

[0063] In a step S4, the pre-torque TM_REF_FF is determined depending on the load signal, for example as with reference to Figure 3 explained.

[0064] In a step S6, the speed signal representative of the actual speed vk_act of the car 24 is received.

[0065] In a step S8, the correction torque TM_REF_PID is monitored over a predetermined monitoring period, wherein the correction torque TM_REF_PID is determined depending on the speed signal and the predetermined reference speed vk_ref such that the actual speed vk_act of the car 24 approaches the reference speed vk_ref, for example by means of the Figure 3shown control loop.

[0066] In step S10, a check is performed to determine whether the monitored correction torque TM_REF_PID meets at least one specified criterion. The specified criterion can be met, for example, if the torque difference TM_REF_PID_STALLING is greater than the specified threshold value TM_CHANGE_LIMIT. If the condition of step S10 is met, processing can continue in step S12. If the condition of step S10 is not met, processing can continue in step S8.

[0067] In step S12, the presence of the stuck situation in which the elevator car 24 or the counterweight 26 gets stuck in the elevator shaft 22 is detected.

[0068] In a step S14, a predetermined safety measure can be implemented. For example, the elevator car 24 and / or the counterweight 26 can be secured using appropriate brakes, for example, the brake 34. Alternatively or additionally, the electric motor 30 can be switched off.

[0069] The method can be started when the elevator system 20 is put into operation. Alternatively, the method can be started when the elevator car 24 begins its journey. Alternatively, the start of the method can be linked to a start condition and only started when the city condition is met. This can help prevent a jerk phase, in which a jerk is transmitted to the elevator car 24 and which can occur when the elevator car 24 starts moving, from being incorrectly identified as a stuck situation. The start condition can be met, for example, if the reference speed vk_ref is not equal to zero. Alternatively or additionally, the start condition can be met when a predetermined period of time, for example, from a few milliseconds to a few seconds, has elapsed after the elevator car 24 begins its journey.Alternatively or additionally, the correction torque TM_REF_PID can be determined before the procedure is started and the procedure can only be started when the torque difference TM_REF_PID_STALLING between the maximum correction torque TM_REF_PID_STALLING _MAX and the minimum correction torque TM_REF_PID_STALLING_MIN within the specified time window is greater than the threshold value TM_CHANGE_LIMIT.

[0070] Finally, it should be noted that terms such as "having," "comprising," etc., do not exclude other elements or steps, and terms such as "a" or "an" do not exclude a plurality. Furthermore, it should be noted that features or steps described with reference to one of the above embodiments may also be used in combination with other features or steps of other of the above embodiments. Reference signs in the claims are not to be considered as limitations.

Claims

1. A method for identifying a situation of being stuck in an elevator system (20), wherein the elevator system (20) has an elevator shaft (22), a car (24) which is arranged in the elevator shaft (22), a counterweight (26) which is coupled to the car (24) by way of suspension means (28), an electric motor (30) which has a traction sheave (32) which can be rotated by means of the electric motor (30), over which the suspension means (28) runs and by means of which the suspension means (28) can be moved so that the car (24) and the counterweight (26) can be displaced vertically by means of operating the electric motor (30), and a brake (34) by means of which the car (24) and / or the counterweight (26) can be braked and / or stopped; the method comprising: receiving a load signal which is representative of a weight of a load (46) which is located in the car (24) and is intended to be transported by means of the car (24); determining a preliminary torque (TM_REF_FF) depending on the load signal; receiving a speed signal (vk_act) which is representative of an actual speed of the car (24); monitoring a correction torque (TM_REF_PID) over a specified monitoring time period, wherein the correction torque (TM_REF_PID) is determined depending on the speed signal (vk_akt) and a specified reference speed (vk_ref) such that the actual speed of the car (24) approximates the reference speed (vk_ref); identifying the situation of being stuck, in which the car (24) or the counterweight (26) remains stuck in the elevator shaft (22) when the monitored correction torque (TM_REF_PID) meets at least one specified criterion; and performing a specified safety measure when the situation of being stuck is identified.

2. The method according to claim 1, wherein, when monitoring the correction torque (TM_REF_PID), a maximum correction torque (TM_REF_PID_STALLING_MAX) and a minimum correction torque (TM_REF_PID_STALLING_MIN) are determined within the specified time period, and wherein the specified criterion is met if a difference (TM_REF_PID_STALLING) between the maximum correction torque (TM_REF_PID_STALLING_MAX) and the minimum correction torque (TM_REF_PID_STALLING_MIN) is greater than a specified threshold (TM_CHANGE_LIMIT).

3. The method according to any one of the preceding claims, wherein a total torque (TM_REF_SUM) is determined depending on the preliminary torque (TM_REF_FF) and the correction torque (TM_REF_PID), and at least one reference current (isq_ref, isd_ref) for operating the electric motor (30) is determined depending on the total torque (TM_REF_SUM).

4. The method according to any one of the preceding claims, wherein the preliminary torque (TM_REF_FF) comprises a load torque (TM_REF_LOAD) and an acceleration torque (TM_REF_ACCEL).

5. The method according to claim 4, wherein the load torque (TM_REF_LOAD) is determined such that, when the brake (34) is released, the car (24) does not move as a result of the determined load torque (TM_REF_LOAD) alone.

6. The method according to either claim 4 or claim 5, wherein the load signal is representative of a difference (UB) between a weight suspended on a side of the traction sheave (32) on which the counterweight (26) is suspended and a weight suspended on a side of the traction sheave (32) on which the car (24) is suspended, and the load torque (TM_REF_LOAD) is determined depending on the first load signal.

7. The method according to any one of claims 4 to 6, wherein the acceleration torque (TM_REF_ACCEL) is determined such that the car (24) moves with a reference acceleration (ak_ref) due to the acceleration torque (TM_REF_ACCEL).

8. The method according to any one of claims 4 to 7, wherein a current mass moment of inertia (IA _ACTUAL) which is representative of the current mass inertia of the elevator system (20) is determined, and the acceleration torque (TM_REF_ACCEL) is determined depending on the current mass moment of inertia (IA _ACTUAL) and a reference acceleration (ak_ref).

9. The method according to any one of the preceding claims, wherein the specified safety measure comprises stopping the electric motor (30) and / or generating an error message.

10. The method according to any one of the preceding claims, wherein monitoring of the correction torque (TM_REF_PID) is started when at least one specified starting condition is met.

11. The method according to claim 10, wherein the starting condition comprises the fact that the correction torque (TM_REF_PID) is determined at least twice in a row, and the correction torque (TM_REF_PID) meets the specified criterion in both determinations; the reference speed (vk_ref) is not equal to zero; and / or after the car (24) has started traveling, a specified run-up period has elapsed.

12. A control device (40) for an elevator system (20), wherein the control device (40) comprises a processor and sensors, in particular a weight sensor, rotational speed sensor, speed sensor, and / or current sensor, which are configured to carry out the method according to any one of the preceding claims.

13. An elevator system (20), comprising: an elevator shaft (22); a car (24) which is arranged in the elevator shaft (22); a counterweight (26) which is arranged in the elevator shaft (22) and is coupled to the car (24) via a suspension means (28); an electric motor (30) having a traction sheave (32) which is rotatable by means of the electric motor (30), over which the suspension means (28) runs and by means of which the suspension means (28) can be moved, so that the car (24) and the counterweight (26) can be displaced vertically by operating the electric motor (30); a brake (34) by means of which the car (24) and / or the counterweight (26) can be braked and / or stopped; and a control device (40) according to claim 12.

14. A computer program comprising commands which cause the device of claim 12 to carry out the method steps according to any one of claims 1 to 11.

15. A computer-readable medium on which the computer program according to claim 14 is stored.