Method and monitoring device for monitoring an operation of an elevator door arrangement

Abstract

An elevator door arrangement is monitored wherein the elevator door arrangement includes at least one door wing and an electric actuator for displacing the door wing in at least one of an opening direction and a closing direction during a door motion event. A method for performing the monitoring includes a learning phase and an application phase. During the learning phase, different types of door motion events are identified and for each type of event a reference motion event duration is determined. During the application phase, a door arrangement operation is observed such as to detect door motion events and the different types of door motion events are distinguished upon comparison of the reference motion event durations with actual motion event durations measured during the application phase. Using the method, door motion events in an elevator may be recognized and monitored in an automatic manner.

Claims

1. A method for monitoring an operation of an elevator door arrangement having at least one door wing and an electric actuator for displacing the door wing in at least one of an opening direction and a closing direction during a door motion event, the method comprising the steps of: performing a learning phase during which different types of the door motion event are detected and identified, and learning a reference motion event duration for each the types of the door motion events; and performing an application phase during which an operation of the door arrangement operation is observed to detect subsequent ones of the door motion events, measuring an actual motion event duration for each of the detected door motion events and distinguishing the type of each of the detected door motion events by comparing the learned reference motion event durations with the actual motion event duration of the detected door motion event.

2. The method according to claim 1 wherein, during the learning phase, a door arrangement operation is observed to detect the door motion events that occur, the identifying of the different types of the door motion events is performed automatically based on the detected door motion events and the determining of the reference motion event duration for each type of door motion events is performed automatically based on the detected door motion events.

3. The method according to claim 1 wherein the door motion events are detected by measuring and analyzing electric supply currents flowing to the electric actuator.

4. The method according to claim 3 wherein the door motion events are detected by inspecting a time profile of the measured electric supply currents for a presence of edges with a gradient of the electric supply currents exceeding a predetermined gradient value.

5. The method according to claim 1 wherein the identifying of the different types of the door motion events during the learning phase comprises: a first step of measuring an electric supply current flowing to the electric actuator during a first time period including a plurality of the door motion events, detecting a minimum current value v.sub.min and a maximum current v.sub.max occurring during the first time period and setting a threshold current value equal to v.sub.min+(α*(v.sub.max−v.sub.min)) with α being a predefined factor value between 0 and 1; and a second step of measuring the electric supply current flowing to the electric actuator during a second time period including another plurality of the door motion events and identifying the different types of the door motion events during the second time period based on characteristics of time periods when the measured electric supply current exceeds the threshold current value.

6. The method according to claim 5 wherein, in the second step, the different types of the door motion events are identified based on durations of the time periods with the measured electric supply current exceeding the threshold current value.

7. The method according to claim 5 wherein a reference motion duration for each of the types of the door motion events is determined based on analyzing a measured duration in which the electric supply current as measured during the second step exceeds the threshold current value.

8. The method according to claim 5 including pre-setting the factor value to a default value of between 0.3 and 0.7 and wherein the factor value is tunable to values between 0 and 1 in an expert configuration step.

9. The method according to claim 5 including, during the application phase, counting numbers of occurrences of the door motion events for each of the types of the door motion events and generating monitoring results based on the counted numbers.

10. A monitoring device for monitoring an operation of an elevator door arrangement, the monitoring device being adapted to perform the method according to claim 1.

11. An elevator comprising: an elevator door arrangement and a monitoring device according to claim 10 monitoring the operation of the elevator door arrangement.

12. A non-transitory computer readable medium comprising: computer readable instructions stored thereon which, when loaded into and performed by a processor of a monitoring device, instruct the monitoring device to perform the method according to claim 1.

13. A computer program product comprising the non-transitory computer readable medium according to claim 12 stored thereon for performing the method.

Description

DESCRIPTION OF THE DRAWINGS

(1) FIG. 1 shows an elevator door arrangement to be monitored with a method in accordance with an embodiment of the present invention.

(2) FIG. 2 shows a time-dependency of a supply current of an elevator door arrangement to be monitored with a method in accordance with an embodiment of the present invention.

(3) The figures are only schematic and not to scale. Same reference signs refer to same or similar features.

DETAILED DESCRIPTION

(4) FIG. 1 shows an elevator door arrangement 1 of an elevator 100, in which a method for monitoring an operation of the elevator door arrangement 1 in accordance with an embodiment of the present invention may be implemented. The elevator door arrangement 1 may be provided at an entrance to an elevator car 2. Particularly, the elevator door arrangement 1 may be implemented as an elevator car door arrangement or, alternatively, as an elevator shaft door arrangement.

(5) The elevator door arrangement 1 comprises two door wings 3 which may be displaced relative to a door frame 7 in opposite opening and closing directions 17 for opening and closing an access to the elevator car 2. A displacement of the door wings 3 may be driven by an electric actuator 5. Such electric actuator 5 may comprise an electric motor which pushes and draws, respectively, the door wings the 3 during opening and closing motions and which is controlled and supplied with electric energy via a door controller 9 connected to the electric actuator 5 via a cable 10.

(6) A monitoring device 11 may be used for monitoring the operation of the elevator door arrangement 1. The monitoring device 11 is configured to observe door motion events performed by the elevator door arrangement 1. In principle, various means for observing such door motion events are possible. For example, a door motion may be observed using a camera system or various other types of sensors directly or indirectly supervising components of the elevator door arrangement 1.

(7) In the embodiment shown in FIG. 1, the monitoring device 11 comprises or is connected to a sensor 13 which may sense an electric energy supply from the controller 9 to the electric actuator 5. For example, the sensor 13 may be a Hall sensor which may sense magnetic fields generated upon an electric current flowing through the cable 10. Accordingly, the sensor 13 may be attached to or arranged in close proximity to the cable 10. The monitoring device 11 may be adapted for receiving and/or analyzing signals from the sensor 13 such as to derive information about a current status of the elevator door arrangement 1. For that purpose, the monitoring device 11 may comprise a central processing unit and/or some electronic memory. Alternatively or additionally, the monitoring device 11 may communicate with a remote control center 15. Therein, the monitoring device 11 may directly forward signals received from the sensor towards the remote control center 15 or, alternatively, the monitoring device 11 may first perform some analysis with such sensor signals before forwarding some pre-processed analysis results to the remote control center 15. Based on the signals and information received from the monitoring device 11, the remote control center 15 may derive valuable information about a current status of the elevator door arrangement 1.

(8) While the hardware of the elevator door arrangement 1 and its monitoring device 11 may be similar to the one described in the applicant's prior application WO 2017/016876 A1, it may be operated in a more automated manner by performing the method for monitoring the operation of the elevator door arrangement 1 described herein.

(9) Particularly, when detecting elevator door events based on electric current signals measured from for example an energy supply to an elevator door actuator, thresholding current signal values may allow detection of these door events.

(10) However, for example a variability of motor types may require different threshold values and, in the prior art approaches, this was set manually by inspecting the current signal. Accordingly, technical expertise was required and additional work efforts where necessary for initializing the monitoring device and/or calibrating suitable threshold values.

(11) In contrast to prior art approaches, it is proposed herein that threshold values may be learned and set automatically, for example by suitably analyzing an electric current signal obtained upon inspecting energy supply to the electric actuator 5 of the elevator door arrangement 1.

(12) The proposed method may be divided into a learning phase and an application phase. During the learning phase, in a first step, different types of door motion events such as “door closing”, “door opening” and “door reversal” may be distinguished such that every occurring door motion may be attributed or categorized to one of such types of door motion events. Subsequently, in a second step, a reference motion event duration is determined for each type of door motion event.

(13) Later, during the application phase, the door arrangement operation is continuously or repeatedly observed such as to detect door motion events. In case, a door motion event is detected, its identity or type may be distinguished from other door motion events upon comparison of the reference motion event duration with an actual motion event duration as it is measured during the application phase.

(14) Next, an example of an embodiment of the proposed monitoring method will be explained with reference to FIG. 2. Therein, FIG. 2 represents a time-dependence profile of an electric current v which is supplied from the door controller 9 via the cable 10 to the electric actuator 5 of the elevator door arrangement 1 and which has been measured using the sensor 13 in order to then be analyzed in the monitoring device 11.

(15) During the learning phase, a signal representing the electric current v is collected during a first time period such as to ensure that multiple door motion events 19, 21 have been captured for the learning phase. While only two door motion events 19, 21 are represented in FIG. 2, it may be noted that the entire first time period generally covers a multiplicity of such door motion events, for example more than ten or preferably more than 100 of such door motion events.

(16) A threshold current value v.sub.thresh may be determined as follows: a minimum current v.sub.min and a maximum current v.sub.max occurring throughout the first time period may be detected. Upon having determined these minimum and maximum current values v.sub.min, v.sub.max, the threshold current value v.sub.thresh is set somewhere between these two extremes, i.e.
v.sub.thresh=v.sub.min+(α*(v.sub.max−v.sub.min))
with the factor value α being between 0 and 1.

(17) Then, in a second time period of the learning phase, the electric supply current v to the electric actuator 5 is again measured over a plurality of door motion events 19, 21. Therein, a door motion event 19, 21 may be recognized upon the electric current v exceeding the previously determined current threshold value v.sub.thresh. In other words, when the measured electric supply current v starts exceeding the threshold current value v.sub.thresh at points in time t.sub.1, t.sub.3, it may be assumed that a door motion event starts, and when the measured electric supply current v stops exceeding the threshold current value v.sub.thresh at points in time t.sub.2, t.sub.4, it may be assumed that a door motion event ends. The points in time t.sub.1 to t.sub.4 may be detected using for example edge detection techniques.

(18) From the dashed vertical lines in FIG. 2, the ending of the actual door opening and door closing events 19, 21 may be slightly offset based on decision boundaries set by the threshold values. Since this offset is generally constant with respect to the electromechanical properties of the door actuator 5, domain experts may manually correct this offset if desired. For applications such as defect detection or anomaly detection, where a key signal is a change in door event timings as opposed to actual timings, an offset correction may not be mandatory.

(19) Then, each recognized door motion event 19, 21 may be identified as being one of a plurality of possible door motion events. Therein, identifying the different types of door motion events may be based on characteristics of time periods Δt with the measured electric supply current v exceeding the threshold current value v.sub.thresh.

(20) For example, it may be known that there are three different types of door motion events 19, 21 including a door opening event 19, a door closing event 21 and a door reversal event (not explicitly represented in the figure). Furthermore, it is generally known that the door closing event 21 requires more time than the door opening event 19. This is true as elevator doors are generally displaced more slowly during closing operations than during opening operations for passenger safety. Furthermore, it is generally known that a door reversal event in most cases takes less time than door opening events and door closing events. However, there may be exceptions when the elevator door has already almost completely closed before being reversed. In other words, the door reversal events have larger tolerances with respect to the durations compared to the door opening events and door closing events. Furthermore, as an additional information, it may be taken into account that, during normal operation of the elevator, the number of door opening events and the number of door closing events corresponds to each other with a difference of at most one, as the elevator door may only be closed when it has been opened before and vice versa.

(21) Taking all this information into account, the door motion events 19, 21 collected during the second time period of the learning phase may be categorized. Therein, it may be assumed that those door motion events 21 having the longest motion event duration Δt.sub.c correspond to door closing events 21 and those door motion events 19 having a shorter motion event duration Δt.sub.o generally correspond to door opening events 19. For all other observed door motion events, it may be assumed that they belong to door reversal events.

(22) If there are ambiguities upon determining a category of a door motion event, additional information such as the correspondence of the number of door openings and door closings may be taken into account for coming to a categorization.

(23) After having categorized all encountered door motion events 19, 21, reference motion event durations may be attributed to each type of door motion event 19, 21. For example, an average of motion event durations Δt.sub.c of door closing events observed during the learning phase may be attributed as the reference motion event duration of the door closing events 21. Similarly, an average of motion event durations Δt.sub.o of door opening events observed during the learning phase may be attributed as the reference motion event duration of the door opening events 19.

(24) In FIG. 2, another possible implementation of elevator door operation is indicated. In this implementation, upon receiving a call for elevator operation, i.e. a call requesting the elevator car to come to a specific floor, the actuator 5 is first brought from an idle mode to a standby mode at a point in time t.sub.0. While, in the idle mode, the elevator door arrangement 1 is in its unlocked state and the actuator 5 consumes almost no electricity, in the standby mode, the elevator door arrangement 1 is locked and the actuator 5 is provided with a small amount of electricity while waiting for becoming active to displace the door wings 3. The step 23 in the electric supply current v occurring upon transition to this standby mode may be taken into account upon subsequent door motion event detection.

(25) Based on the preparations performed during the learning phase, the monitoring method may then, during the application phase, differentiate between various types of door motion events 19, 21 by comparing actual motion event durations as measured during the application phase with those reference motion event durations determined during the learning phase.

(26) For example, upon being able to distinguish different types of door motion events, numbers of occurrences of each type of door motion event 19, 21 may be counted. Such information may be for example transmitted to the remote control center 15 and may be taken into account upon planning any future maintenance work.

(27) The approach proposed herein may allow various advantages compared to prior art approaches. For example, compared to manual threshold labelling, the described approach may allow for higher generalizability with lower manual effort. Furthermore, the approach described does not necessarily require training data where labelled signal segments are used to “teach” a machine learning system by example. Furthermore, sensor based door segmentation may be enabled for a wide range of elevator models.

(28) Finally, it should be noted that the term “comprising” does not exclude other elements or steps and the “a” or “an” does not exclude a plurality. Also, elements described in association with different embodiments may be combined.

(29) In accordance with the provisions of the patent statutes, the present invention has been described in what is considered to represent its preferred embodiment. However, it should be noted that the invention can be practiced otherwise than as specifically illustrated and described without departing from its spirit or scope.