Elevator door lock circuit fault detection method based on time domain reflection and difference analysis

Abstract

This application belongs to the field of elevator safety inspection technology, specifically disclosing a fault detection method for elevator door lock circuits based on time-domain reflection and difference analysis. The method includes: inputting an incident signal into the elevator door lock circuit and receiving a reflected signal from the circuit; determining whether an open-circuit fault has occurred in the elevator door lock circuit based on the incident and reflected signals using the time-domain reflection method; if no open-circuit fault is found, comparing the waveform difference between the reflected signal and a reference waveform (obtained by inputting an incident signal and receiving a reflected signal when the circuit is in a healthy state); and analyzing the risk of poor contact at the door lock contacts based on the waveform difference and a preset threshold. This application enables efficient detection of open-circuit faults and early warning of poor contact problems, ensuring elevator operational safety.

Description

Technical Field

[0001] This application belongs to the field of elevator safety inspection technology, and more specifically, relates to an elevator door lock circuit fault detection method based on time-domain reflection and difference analysis. Background Technology

[0002] As an indispensable vertical transportation tool in modern buildings, the safety of elevators is always a core concern. The elevator door lock circuit is a core component of the elevator safety system, responsible for monitoring the closing status of the car and landing doors, ensuring that the elevator operates only when all doors are fully closed and locked. A malfunction in the door lock circuit will directly affect the elevator's operation and may even pose a risk of causing a safety accident.

[0003] Elevator door lock circuits typically consist of multiple door lock contacts connected in series, including the car door lock contacts and the landing door lock contacts for each floor. When the elevator doors close, all contacts should be closed, forming a complete circuit. If any contact fails to close, the circuit will break, and the elevator will not start. This design ensures that the elevator can only operate when all doors are safely closed, thus preventing the elevator from moving when the doors are not closed and avoiding the risk of passengers falling or being trapped.

[0004] There are two main types of common door lock circuit faults. The first type is caused by the door lock contacts not being fully closed, the circuit being broken, or the connection being loose, resulting in a broken circuit and the elevator being unable to start. The second type is caused by the door lock contacts being oxidized, dust accumulating, or the door lock springs aging, resulting in insufficient contact pressure, which causes poor contact. This will cause the circuit to be intermittent, affecting the stability of the elevator operation. This type of fault has a gradual characteristic and is not easy to detect in the early stages. Over a long period of time, it may eventually evolve into an open circuit fault.

[0005] In existing technologies, the detection of elevator door lock circuit faults mainly relies on manual floor-by-floor troubleshooting. This method is inefficient, requiring maintenance personnel to check the door lock contact status on each floor one by one. Simultaneously, it leads to prolonged elevator downtime, impacting user experience, especially in high-rise buildings where its limitations are more pronounced. Furthermore, manual troubleshooting suffers from response lag; it can only detect existing open-circuit faults and cannot effectively troubleshoot and intervene in the early stages of door lock contact malfunctions to prevent further failures.

[0006] In summary, current methods for detecting elevator door lock circuit faults suffer from drawbacks such as difficulty in fault location, low efficiency in fault diagnosis, and insufficient early detection of poor contact at door lock contacts. How to efficiently detect open circuit faults in elevator door lock circuits and effectively provide early warnings of poor contact at door lock contacts is a pressing technical problem that needs to be solved in this field. Summary of the Invention

[0007] In view of the shortcomings of the existing technology, the purpose of this application is to achieve efficient detection of elevator door lock circuit open circuit faults and effective early warning of poor contact of door lock contacts.

[0008] To achieve the above objectives, in a first aspect, this application provides a method for detecting elevator door lock circuit faults based on time-domain reflectometry and difference analysis, the method comprising: The incident signal is input to the elevator door lock circuit, and the reflected signal reflected back from the elevator door lock circuit is received. The incident signal is a pulse-type signal. Based on the incident and reflected signals, the time-domain reflection method is used to determine whether there is an open circuit fault in the elevator door lock circuit. If it is determined that there is no open circuit fault in the elevator door lock circuit, the waveform difference between the reflected signal and the reference waveform is compared. The reference waveform is obtained by inputting an incident signal into the elevator door lock circuit and receiving the reflected signal when the elevator door lock circuit is in a healthy state. Based on waveform differences and preset thresholds, the risk of poor contact of the elevator door lock circuit is analyzed.

[0009] It should be noted that the reflected signal is a fluctuating waveform, the duration of which is related to the time it takes for the signal to propagate in the door lock circuit, and the amplitude at each point is related to the characteristic impedance at each point in the door lock circuit.

[0010] Understandably, by inputting a pulse incident signal into the elevator door lock circuit and receiving the reflected signal, the time-domain reflectometry method is used to quickly determine if there is an open circuit fault. If no open circuit is detected, the waveform of the current reflected signal is compared with a reference waveform obtained beforehand under healthy conditions. Poor contact at the door lock contacts will cause a change in the impedance at the door lock contacts compared to the healthy state, thus altering the waveform of the reflected signal at the door lock contacts. These changes will be reflected in the waveform difference. By comparing and analyzing the waveform difference with a preset threshold, the risk of poor contact at the door lock contacts can be effectively assessed, thereby achieving efficient detection of open circuit faults and early warning of poor contact problems, ensuring the safe operation of the elevator.

[0011] In one possible implementation, the waveform difference between the waveform of the compared reflected signal and the reference waveform includes: Based on the time window of the reflected signal corresponding to the elevator door lock contact of each floor, the received reflected signal is segmented to obtain the real-time waveform segment corresponding to the elevator door lock contact of each floor (the real-time waveform segment can characterize the impedance characteristics at the current elevator door lock contact). The reflected signal time window is used to characterize the time interval between the reflected signal and the incident signal in time sequence. For each floor's elevator door lock contact, compare the waveform differences between the real-time waveform segment corresponding to the elevator door lock contact and the corresponding waveform segment in the reference waveform.

[0012] Specifically, after the incident signal is input to the elevator door lock circuit, the reflected signals corresponding to the elevator door lock contacts on each floor can be received. Combined with the time window of the reflected signal to characterize the time interval between the reflected signal and the incident signal in terms of timing, the received reflected signal can be segmented based on the time window of the reflected signal corresponding to the elevator door lock contacts on each floor, and the real-time waveform segment corresponding to the elevator door lock contacts on each floor can be determined.

[0013] Since the reference waveform is acquired when the elevator door lock circuit is in a healthy state, it includes the reflected signals corresponding to the elevator door lock contacts on each floor. Furthermore, the reflected signals in the reference waveform characterize the impedance characteristics of the elevator door lock contacts in a healthy state. Therefore, after acquiring the real-time waveform segments corresponding to the elevator door lock contacts on each floor, these segments can be compared with the corresponding waveform segments in the reference waveform to determine the waveform differences.

[0014] In one possible implementation, waveform differences include: correlation coefficient and mean square error.

[0015] In one possible implementation, the above analysis of the risk of poor contact at the elevator door lock circuit based on waveform differences and preset thresholds includes: Perform a risk analysis of poor contact at the elevator door lock contacts on each floor; The procedure for analyzing the risk of adverse reactions includes: Compare the correlation coefficient of the elevator door lock contact point on the current floor with the preset correlation coefficient threshold, and compare the mean square error of the elevator door lock contact point on the current floor with the preset mean square error threshold. If the correlation coefficient of the elevator door lock contact on the current floor is less than the preset correlation coefficient threshold or the mean square error of the elevator door lock contact on the current floor is greater than the preset mean square error threshold, then it is determined that there is a risk of poor contact at the elevator door lock contact on the current floor; otherwise, there is no risk of poor contact at the elevator door lock contact on the current floor.

[0016] In one possible implementation, the time window for the reflected signal corresponding to the elevator door lock contacts on each floor is determined by the following steps: When the elevator door lock circuit is in good condition, perform time window calibration operation for the elevator door lock contacts on each floor; The time window calibration operation includes: Disconnect the elevator door lock contacts on the current floor, and keep the elevator door lock contacts on all floors except the current floor closed. The incident signal is input to the elevator door lock circuit, and the signal reflected back from the elevator door lock circuit is received. The time window in which the target signal is located in the reflected signal is determined to be the time window of the reflected signal corresponding to the elevator door lock contact on the current floor. The difference between the amplitude of the target signal and the amplitude of the incident signal is less than the preset amplitude difference (that is, the amplitude of the target signal is close to the amplitude of the incident signal), and the phase of the target signal is the same as the phase of the incident signal.

[0017] It should be noted that, since the door locks are disconnected, according to the principle of time-domain reflection, there will be a waveform (target signal) at the disconnection point with an amplitude close to the incident signal and the same phase. This is used to determine the time window of the reflected waveform at each door lock.

[0018] In one possible implementation, the above method of determining whether an elevator door lock circuit has an open circuit fault using time-domain reflection includes: Determine whether the target signal is present in the reflected signal. If it is, it is determined that there is an open circuit fault in the elevator door lock circuit. Otherwise, it is determined that there is no open circuit fault in the elevator door lock circuit. The difference between the amplitude of the target signal and the amplitude of the incident signal is less than the preset amplitude difference, and the phase of the target signal remains the same as the phase of the incident signal.

[0019] One possible implementation also includes: If it is determined that there is an open circuit fault in the elevator door lock circuit, the time window of the reflected signal in the reflected signal is determined. The difference between the amplitude of the target signal and the amplitude of the incident signal is less than the preset amplitude difference. The phase of the target signal and the phase of the incident signal are kept the same. The time window of the reflected signal is used to characterize the time interval between the reflected signal and the incident signal in terms of timing. The location of the circuit breaker fault (which can be a certain floor or between two floors) is determined by comparing the time window of the reflected signal of the target signal with the time window of the reflected signal of the elevator door lock contacts on each floor.

[0020] Specifically, assuming the time window of the reflected signal where the target signal is located is At any given time, for two adjacent floors (floor A and floor B), the time window for the reflected signal corresponding to the elevator door lock contact on floor A is... At any given time, the time window for the reflected signal corresponding to the elevator door lock contact on floor B is... At that moment. If The time is equal to (or close to) At that moment, the fault location is at the elevator door lock contact on floor A. If The time is equal to (or close to) At that moment, the fault location is at the elevator door lock contact on floor B. If... Time is located Time and At any given moment, the fault location is in the elevator door lock circuit between floor A and floor B.

[0021] Understandably, the technical principle behind this method's ability to accurately locate an open circuit fault in the elevator door lock circuit lies in identifying a specific target signal indicating the open circuit fault from the received reflected signals and determining the specific time window in which this target signal is located. This time window precisely reflects the time interval between the incident signal encountering the open circuit point and being reflected back. Since the door lock contacts on each floor of the elevator are physically located differently, the time required for the reflected signal to reach the signal acquisition point varies. Therefore, the time window for the reflected signal corresponding to each floor's door lock contact can be known in advance. By accurately comparing the detected target signal's time window with these pre-defined time windows corresponding to each floor, it is possible to accurately determine which specific floor the open circuit fault occurred on, or the section between which two floors it is located in, thus achieving precise fault location.

[0022] Secondly, this application also provides an elevator door lock circuit fault detection system based on time-domain reflection and difference analysis, the system comprising: a signal transmitting subsystem and a signal receiving subsystem; The signal transmission subsystem is used for: The incident signal is input to the elevator door lock circuit; The signal receiving subsystem is used for: It receives the incident signal and the reflected signal reflected back from the elevator door lock circuit; the incident signal is a pulse-type signal. Based on the incident and reflected signals, the time-domain reflection method is used to determine whether there is an open circuit fault in the elevator door lock circuit. If it is determined that there is no open circuit fault in the elevator door lock circuit, the waveform difference between the reflected signal and the reference waveform is compared. The reference waveform is obtained by inputting an incident signal into the elevator door lock circuit and receiving the reflected signal when the elevator door lock circuit is in a healthy state. Based on waveform differences and preset thresholds, the risk of poor contact of the elevator door lock circuit is analyzed.

[0023] In one possible implementation, the signal transmitting subsystem includes: a pulse signal generation module, a power amplifier circuit, and an impedance matching circuit; The pulse signal generation module is used to generate the incident signal and provide the incident signal to the power amplifier circuit; Power amplifier circuits are used to amplify the power of incident signals; Impedance matching circuits are used to adjust the impedance relationship between the signal source and the load, and to input the amplified incident signal into the elevator door lock circuit.

[0024] In one possible implementation, the signal receiving subsystem includes: a signal conditioning module, a data acquisition module, and an analysis and display module; The signal conditioning module is used to receive the reflected signal, perform noise reduction on the reflected signal, and provide amplitude limiting protection when the amplitude of the reflected signal exceeds the preset amplitude. The data acquisition module is used to acquire the incident signal provided by the signal transmission subsystem and the reflected signal after being conditioned by the signal conditioning module; The analysis and display module is used to perform the following operations on the incident and reflected signals acquired by the data acquisition module: Based on the incident and reflected signals, the time-domain reflection method is used to determine whether there is an open circuit fault in the elevator door lock circuit. If it is determined that there is no open circuit fault in the elevator door lock circuit, compare the waveform difference between the reflected signal and the reference waveform. Based on waveform differences and preset thresholds, the risk of poor contact of elevator door lock contacts is analyzed, and the analysis results are displayed.

[0025] It is understandable that the beneficial effects of the second aspect mentioned above can be found in the relevant descriptions in the first aspect mentioned above, and will not be repeated here.

[0026] Overall, the technical solutions conceived in this application have the following beneficial effects compared with the prior art: (1) By inputting a pulse incident signal into the elevator door lock circuit and receiving the reflected signal, the time domain reflection method is used to quickly determine whether there is a circuit failure. By comparing and analyzing the waveform difference with the preset threshold, the risk of poor contact of the door lock contact can be effectively assessed, thereby achieving efficient detection of circuit failure and early warning of poor contact problem, and ensuring the safe operation of the elevator.

[0027] (2) By accurately comparing the time window of the detected target signal (the difference between the amplitude of the target signal and the amplitude of the incident signal is less than the preset amplitude difference, and the phase of the target signal is the same as the phase of the incident signal) with the time windows corresponding to each preset floor, it is possible to accurately determine which specific floor the circuit breaker fault occurred on, or which section between two floors, thereby achieving accurate fault location. Attached Figure Description

[0028] Figure 1 This is a flowchart illustrating the elevator door lock circuit fault detection method based on time-domain reflection and difference analysis provided in the embodiments of this application. Figure 2 This is a schematic diagram of the elevator door lock circuit fault detection system based on time-domain reflection and difference analysis provided in the embodiments of this application. Detailed Implementation

[0029] To make the objectives, technical solutions, and advantages of this application clearer, the following detailed description is provided in conjunction with the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are merely illustrative and not intended to limit the scope of this application.

[0030] In the embodiments of this application, the terms "exemplary" or "for example" are used to indicate that something is an example, illustration, or description. Any embodiment or design that is described as "exemplary" or "for example" in the embodiments of this application should not be construed as being more preferred or advantageous than other embodiments or design. Specifically, the use of the terms "exemplary" or "for example" is intended to present the relevant concepts in a specific manner.

[0031] In the description of the embodiments of this application, unless otherwise stated, "multiple" means two or more, for example, multiple processing units means two or more processing units, multiple elements means two or more elements, etc.

[0032] The embodiments of this application are described below with reference to the accompanying drawings.

[0033] This application proposes a method and system for detecting elevator door lock circuit faults based on time-domain reflectometry (TDR) and difference analysis. This technology sends narrow pulse signals to the door lock circuit, utilizes the characteristics of the reflected waveform to locate impedance discontinuities, and combines difference analysis to compare the real-time waveform with a reference waveform, achieving high-precision location and early warning of poor contact and open circuit faults in the door lock contacts.

[0034] Transmission line detection (TDR) is a measurement technique for analyzing reflected waves, primarily used to measure the characteristic impedance of transmission lines. Its principle is that when a signal propagates along a path, if the impedance changes at a certain point, part of the signal will be reflected, while the other part will continue to propagate along the path. The amplitude and polarity of the reflected signal are directly related to the impedance change. By measuring the voltage amplitude of the reflected signal, the specific impedance change can be calculated; simultaneously, based on the time difference between the reflection point and the signal input point, the distance from the impedance change point to the signal input location can be calculated.

[0035] The relevant formulas for the time-domain reflectometry principle are as follows: ; in, The reflection coefficient, The amplitude of the reflected signal. The amplitude of the incident signal, The characteristic impedance of the transmission line, This represents the load impedance. In an elevator door lock circuit, the characteristic impedance of the transmission line is typically approximately 50Ω.

[0036] If an open circuit fault occurs at the door lock contacts, cable connection points, or other locations, it will cause a significant change in impedance. The reflection coefficient can be calculated. The signal is reflected at this point, and the amplitude and polarity of the reflected wave are equal to those of the incident wave.

[0037] By measuring the time delay of the reflected signal and combining it with the signal propagation speed It can calculate the distance to the fault point: ; Where L is the distance from the fault point to the injection point of the incident wave. The speed at which a signal propagates in the cable medium is related to the dielectric constant of the medium. , These represent the time when the incident wave is sent and the time when the reflected wave returns to the point of origin, respectively.

[0038] Generally, due to differences in material between the door lock contacts and the wires, variations in contact geometry, and the presence of contact resistance, impedance changes occur at the door lock contacts. Therefore, even under normal conditions, reflected waves are generated at the door lock contacts. The degree of impedance change varies among different door lock models, resulting in variations in the amplitude of the reflected wave. Furthermore, early contact problems at door lock contacts (such as oxidation, dust accumulation, and wear) often manifest as gradual impedance changes rather than abrupt changes. In such cases, the amplitude change of the reflected signal is not significant, making it difficult for traditional TDR technology to directly identify such minute changes. Additionally, although TDR technology can accurately measure the distance between the open circuit fault point and the signal injection point, the wiring length of the elevator door lock circuit is usually difficult to determine, making it impossible to accurately pinpoint the specific floor where the fault occurred.

[0039] To address the issue of insignificant amplitude changes in TDR reflected signals due to poor contact at early door lock contacts, this system introduces difference analysis. By comparing the real-time acquired TDR reflected waveform with the pre-stored reference waveform (the TDR response waveform of the door lock circuit in a healthy state) point by point, the system quantifies the differences, thereby enabling effective identification of minute impedance changes at the door lock contacts.

[0040] Figure 1 This is a flowchart illustrating the elevator door lock circuit fault detection method based on time-domain reflectometry and difference analysis provided in this application embodiment. Figure 1 As shown, the method includes steps S101 to S104.

[0041] Step S101: Input the incident signal into the elevator door lock circuit and receive the reflected signal reflected back from the elevator door lock circuit. The incident signal is a pulse-type signal. Step S102: Based on the incident signal and the reflected signal, determine whether there is an open circuit fault in the elevator door lock circuit by using the time domain reflection method; Step S103: If it is determined that there is no open circuit fault in the elevator door lock circuit, the waveform difference between the reflected signal and the reference waveform is compared. The reference waveform is obtained by inputting an incident signal into the elevator door lock circuit and receiving the reflected signal when the elevator door lock circuit is in a healthy state. Step S104: Based on waveform differences and preset thresholds, analyze the risk of poor contact of the elevator door lock circuit.

[0042] Understandably, by inputting a pulse incident signal into the elevator door lock circuit and receiving the reflected signal, the time-domain reflectometry method is used to quickly determine if there is an open circuit fault. If no open circuit is detected, the waveform of the current reflected signal is compared with a reference waveform obtained beforehand under healthy conditions. Poor contact at the door lock contacts will cause a change in the impedance at the door lock contacts compared to the healthy state, thus altering the waveform of the reflected signal at the door lock contacts. These changes will be reflected in the waveform difference. By comparing and analyzing the waveform difference with a preset threshold, the risk of poor contact at the door lock contacts can be effectively assessed, thereby achieving efficient detection of open circuit faults and early warning of poor contact problems, ensuring the safe operation of the elevator.

[0043] Optionally, during implementation, the time window for the TDR reflected signal corresponding to each floor's door lock contact is first defined. Then, the system segments the fully acquired TDR waveform according to the aforementioned time window, with each segment corresponding to the reflection response of a specific floor's door lock contact area. A unique identifier (such as a floor number) is added to the waveform segment corresponding to each floor, and this is stored in the system as a standard reference waveform for that floor. Furthermore, if a circuit breaker fault occurs, comparing the time of the circuit breaker fault reflected signal with the time window for the TDR reflected signal corresponding to each floor's door lock contact allows for accurate determination of the specific floor where the fault occurred.

[0044] To accurately quantify the difference between real-time waveforms and reference waveforms, this application employs two main difference metrics: correlation coefficient (CC) and mean squared error (MSE). The correlation coefficient measures the strength of the linear relationship between two sets of data, and its calculation formula is as follows: ; in and These represent the values ​​of the real-time waveform and the reference waveform at the i-th sampling point, respectively; and These represent the average values ​​of all sampling points of the real-time waveform and the reference waveform, respectively; N is the total number of sampling points.

[0045] The mean squared error is used to measure the average squared difference between two sets of data, and its calculation formula is: ; In subsequent operation, after each real-time waveform is acquired, the system segments it according to the same rules and compares it with the reference waveform for the corresponding floor. For each floor's waveform segment, the correlation coefficient and mean square error between the real-time waveform and the reference waveform are calculated. If the correlation coefficient value for a certain floor is significantly lower than its preset threshold or the mean square error value exceeds its preset threshold, it is preliminarily determined that there is a potential risk of poor contact at the door lock contacts on that floor. In this way, the system can detect subtle differences between waveforms, thereby achieving early warning of poor contact problems.

[0046] The entire system consists of a signal transmitting subsystem and a signal receiving subsystem. The signal transmitting subsystem includes a pulse signal generation module, a power amplifier circuit, and an impedance matching circuit. The signal receiving subsystem includes a signal conditioning module, a data acquisition module, a data storage module, and an analysis and display module. Figure 2This is a schematic diagram of the elevator door lock circuit fault detection system based on time-domain reflection and difference analysis provided in this application embodiment. The pulse signal generation module uses an ultra-high-speed FPGA to generate a high-precision narrow pulse signal with a rise and fall time of less than 1 ns to ensure the detection of minute impedance changes. To improve signal strength and overcome potential transmission losses, the generated pulse signal is then amplified by a power amplifier circuit and simultaneously sent to the data acquisition module to mark the start of the pulse signal, ensuring the data acquisition module can accurately record the arrival time of the reflected signal. The power amplifier circuit adjusts the signal amplitude according to actual needs, ensuring the signal has sufficient energy to drive subsequent loads while maintaining the integrity of the signal waveform. The amplified signal then passes through an impedance matching circuit, which adjusts the impedance relationship between the signal source and the door lock circuit cable to minimize signal reflection and distortion, thereby improving signal transmission efficiency. The signal is then injected into the elevator door lock circuit. During transmission, when encountering impedance discontinuities, part of the signal is reflected back. The reflected signal returns along the original path and is received by the signal conditioning module. The signal conditioning module includes components such as a bandpass filter and amplitude limiting protection circuit to suppress noise interference and protect subsequent circuits from abnormally high-amplitude signals. The conditioned reflected signal is captured by the data acquisition module, which features a high sampling rate (GHz level). Each sampling point has a precise timestamp, recording the time offset and amplitude information of the reflected signal relative to the trigger signal. The reference TDR waveform of the door lock circuit used for difference analysis is stored in the data storage module. Finally, the real-time acquired data is transmitted to the analysis and display module. First, the reflected signal is analyzed to determine if an open-circuit fault has occurred in the door lock circuit. If an open-circuit fault has occurred, the specific floor where the fault occurred is determined by combining the delay of the reflected signal with the stored time windows of the door lock reflected signals for each floor. If no open-circuit fault has occurred, the signal is segmented according to time windows. For each floor's waveform segment, the correlation coefficient and mean square error between the real-time waveform and the reference waveform are calculated. Combined with a set threshold, it is determined whether the door locks on each floor exhibit early characteristics of poor door lock contact.

[0047] When using this system to perform TDR testing on the door lock circuit, selecting the pulse signal input point is a crucial step. Typically, the voltage for the elevator door lock circuit is provided by the elevator main control board. Therefore, the ideal pulse signal injection point should be selected at the connection between the main control board and the door lock circuit, ensuring that the signal covers the entire door lock circuit.

[0048] Before using this system to diagnose and locate poor contact or open circuit faults in the door lock circuit of an elevator, it is first necessary to establish a reference waveform reflecting the healthy state of the elevator door lock circuit and determine the time window for the occurrence of reflected signals at each floor. The specific implementation steps are as follows: First, complete reference waveform acquisition. After ensuring that the elevator door lock contacts are free from oxidation, dust accumulation, wear, or other contact defects, and that all door lock contacts are in a normally closed state, this system performs a complete TDR scan of the elevator door lock circuit. The acquired reflected waveform accurately reflects the health status of the door lock circuit. After acquisition, the obtained waveform is used as the reference waveform for the elevator door lock circuit and stored in the data storage module.

[0049] Second, floor-level waveform segmentation. After the baseline waveform is acquired, the door lock contacts of each floor are disconnected sequentially, and then an independent TDR scan is performed. Since only one floor's door lock contacts are disconnected at a time, that floor becomes the unique break point, thus generating a uniquely identifiable break-circuit reflection signal characteristic in the TDR waveform. By analyzing the timing and location of this reflection signal, the signal response time window corresponding to that floor can be uniquely determined. To ensure the accuracy of the test data, after each door lock contact is disconnected, the system must be allowed to stabilize before performing a TDR scan. After the scan is completed, the reflection signal time window information corresponding to each floor is stored in the data storage module, and an independent signal response time window is established for each floor, serving as the basis for waveform segmentation processing during subsequent real-time detection.

[0050] After establishing the baseline waveform and calibrating the floor time window, it is necessary to pre-set the threshold values ​​for the correlation coefficient (CC) and mean square error (MSE) based on the experience of domain experts. For example, the threshold for the correlation coefficient can be set to 0.95, and the threshold for the mean square error can be set to 0.05. These thresholds can be adjusted according to the actual operation of the system to adapt to the impact of different door lock models and environmental changes.

[0051] Next, actual testing can be conducted. When an open-circuit fault is suspected in the elevator door lock circuit or during routine maintenance testing, the TDR testing process of this system is initiated. Before starting the test, the power supply from the elevator main control board to the door lock circuit must be disconnected to ensure the safety and signal integrity of the testing process. Subsequently, a high-precision narrow pulse signal with rise and fall times both less than 1ns is generated by the pulse signal generation module. The signal strength is enhanced by the power amplification circuit, and the impedance matching circuit is used to reduce signal reflection and distortion. Finally, the pulse signal is injected into the end of the door lock circuit. After the reflected signal returns along the original path, it is improved by the signal conditioning module to protect the subsequent circuits. The processed signal is captured by the high-speed data acquisition module. Each sampling point has precise timestamp information and is temporarily stored in the system. The acquisition results are presented as a visualized TDR waveform by the analysis and display module, while also marking the signal response time window corresponding to each floor, which facilitates subsequent analysis and fault location.

[0052] Circuit breaker identification and location. If a significant abrupt change in amplitude and phase, close to the incident signal, is observed at a certain location in the displayed TDR waveform, a circuit breaker can be identified at that location. Combined with pre-calibrated floor time window information, the system can accurately identify the specific floor or between which two floors the circuit breaker occurred on.

[0053] Fault diagnosis and location for poor contact. If no obvious open circuit fault characteristics are found, the system will segment the real-time acquired TDR waveform according to the same time window division rules as the reference waveform, and compare it point by point with the reference waveform of the corresponding floor. For the waveform segment corresponding to each floor, the system calculates the correlation coefficient and mean square error between the real-time waveform and the reference waveform, and compares them with preset thresholds. If the correlation coefficient of a certain floor is lower than the set threshold, or its mean square error is higher than the set threshold, the system initially determines that there is a potential risk of poor contact in the door lock contacts of that floor, and issues a warning to the maintenance personnel, suggesting further inspection and maintenance of that floor.

[0054] It is understood that the various numerical designations used in the embodiments of this application are merely for the convenience of description and are not intended to limit the scope of the embodiments of this application.

[0055] Those skilled in the art will readily understand that the above description is merely a preferred embodiment of this application and is not intended to limit this application. Any modifications, equivalent substitutions, and improvements made within the spirit and principles of this application should be included within the scope of protection of this application.

Claims

1. A method for detecting a fault in an elevator door lock circuit based on time domain reflection and differential analysis, characterized by, include: The incident signal is input to the elevator door lock circuit, and the reflected signal reflected back from the elevator door lock circuit is received. The incident signal is a pulse-type signal. Based on the incident and reflected signals, the time-domain reflection method is used to determine whether there is an open circuit fault in the elevator door lock circuit. If it is determined that there is no open circuit fault in the elevator door lock circuit, the waveform difference between the reflected signal and the reference waveform is compared. The reference waveform is obtained by inputting an incident signal into the elevator door lock circuit and receiving the reflected signal when the elevator door lock circuit is in a healthy state. Based on waveform differences and preset thresholds, the risk of poor contact of elevator door lock contacts is analyzed. The waveform difference between the waveform of the compared reflected signal and the reference waveform includes: Based on the time window of the reflected signal corresponding to the elevator door lock contact on each floor, the received reflected signal is segmented to obtain the real-time waveform segment corresponding to the elevator door lock contact on each floor. The reflected signal time window is used to characterize the time interval between the reflected signal and the incident signal in time sequence. For the elevator door lock contacts on each floor, compare the waveform differences between the real-time waveform segment corresponding to the elevator door lock contact and the corresponding waveform segment in the reference waveform. The analysis of the risk of poor contact at the elevator door lock circuit based on waveform differences and preset thresholds includes: Perform a risk analysis of poor contact at the elevator door lock contacts on each floor; The procedure for analyzing the risk of adverse reactions includes: Compare the correlation coefficient of the elevator door lock contact point on the current floor with the preset correlation coefficient threshold, and compare the mean square error of the elevator door lock contact point on the current floor with the preset mean square error threshold. If the correlation coefficient of the elevator door lock contact on the current floor is less than the preset correlation coefficient threshold or the mean square error of the elevator door lock contact on the current floor is greater than the preset mean square error threshold, then it is determined that there is a risk of poor contact at the elevator door lock contact on the current floor; otherwise, there is no risk of poor contact at the elevator door lock contact on the current floor.

2. The method for detecting an elevator door lock circuit fault based on time domain reflection and difference analysis according to claim 1, characterized in that, The waveform differences include: correlation coefficient and mean square error.

3. The elevator door lock circuit fault detection method based on time-domain reflection and difference analysis according to claim 1, characterized in that, The time window for the reflected signal corresponding to the elevator door lock contacts on each floor is determined through the following steps: When the elevator door lock circuit is in good condition, perform time window calibration operation for the elevator door lock contacts on each floor; The time window calibration operation includes: Disconnect the elevator door lock contacts on the current floor, and keep the elevator door lock contacts on all floors except the current floor closed. The incident signal is input to the elevator door lock circuit, and the signal reflected back from the elevator door lock circuit is received. The time window in which the target signal is located in the reflected signal is determined to be the time window of the reflected signal corresponding to the elevator door lock contact on the current floor. The difference between the amplitude of the target signal and the amplitude of the incident signal is less than the preset amplitude difference, and the phase of the target signal is the same as the phase of the incident signal.

4. The elevator door lock circuit fault detection method based on time-domain reflection and difference analysis according to claim 1, characterized in that, The method of determining whether there is an open circuit fault in the elevator door lock circuit using the time-domain reflection method includes: Determine whether the target signal is present in the reflected signal. If it is, it is determined that there is an open circuit fault in the elevator door lock circuit. Otherwise, it is determined that there is no open circuit fault in the elevator door lock circuit. The difference between the amplitude of the target signal and the amplitude of the incident signal is less than the preset amplitude difference, and the phase of the target signal remains the same as the phase of the incident signal.

5. The elevator door lock circuit fault detection method based on time-domain reflection and difference analysis according to claim 1, characterized in that, Also includes: If it is determined that there is an open circuit fault in the elevator door lock circuit, the time window of the reflected signal in the reflected signal is determined. The difference between the amplitude of the target signal and the amplitude of the incident signal is less than the preset amplitude difference. The phase of the target signal and the phase of the incident signal are kept the same. The time window of the reflected signal is used to characterize the time interval between the reflected signal and the incident signal in terms of timing. The location of the circuit breaker fault is determined by comparing the time window of the reflected signal of the target signal with the time window of the reflected signal of the elevator door lock contacts on each floor.

6. A fault detection system for elevator door lock circuits based on time-domain reflectometry and difference analysis, characterized in that, The elevator door lock circuit fault detection method based on time-domain reflection and difference analysis as described in claim 1 includes: a signal transmitting subsystem and a signal receiving subsystem; The signal transmission subsystem is used for: The incident signal is input to the elevator door lock circuit; The signal receiving subsystem is used for: It receives the incident signal and the reflected signal reflected back from the elevator door lock circuit; the incident signal is a pulse-type signal. Based on the incident and reflected signals, the time-domain reflection method is used to determine whether there is an open circuit fault in the elevator door lock circuit. If it is determined that there is no open circuit fault in the elevator door lock circuit, the waveform difference between the reflected signal and the reference waveform is compared. The reference waveform is obtained by inputting an incident signal into the elevator door lock circuit and receiving the reflected signal when the elevator door lock circuit is in a healthy state. Based on waveform differences and preset thresholds, the risk of poor contact of the elevator door lock circuit is analyzed.

7. The elevator door lock circuit fault detection system based on time-domain reflectometry and difference analysis according to claim 6, characterized in that, The signal transmission subsystem includes: a pulse signal generation module, a power amplifier circuit, and an impedance matching circuit; The pulse signal generation module is used to generate the incident signal and provide the incident signal to the power amplifier circuit; Power amplifier circuits are used to amplify the power of incident signals; Impedance matching circuits are used to adjust the impedance relationship between the signal source and the load, and to input the amplified incident signal into the elevator door lock circuit.

8. The elevator door lock circuit fault detection system based on time-domain reflectometry and difference analysis according to claim 6, characterized in that, The signal receiving subsystem includes: a signal conditioning module, a data acquisition module, and an analysis and display module; The signal conditioning module is used to receive the reflected signal, perform noise reduction on the reflected signal, and provide amplitude limiting protection when the amplitude of the reflected signal exceeds the preset amplitude. The data acquisition module is used to acquire the incident signal provided by the signal transmission subsystem and the reflected signal after being conditioned by the signal conditioning module; The analysis and display module is used to perform the following operations on the incident and reflected signals acquired by the data acquisition module: Based on the incident and reflected signals, the time-domain reflection method is used to determine whether there is an open circuit fault in the elevator door lock circuit. If it is determined that there is no open circuit fault in the elevator door lock circuit, compare the waveform difference between the reflected signal and the reference waveform. Based on waveform differences and preset thresholds, the risk of poor contact of elevator door lock contacts is analyzed, and the analysis results are displayed.

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