Cable branch box terminal crimping quality determination method based on resistance dynamic monitoring

Abstract

The present application belongs to the technical field of electrically conductive connection crimping quality detection, and particularly relates to a cable branch box terminal crimping quality determination method based on resistance dynamic monitoring, which comprises the following steps: synchronously acquiring a terminal voltage sequence and a terminal current sequence at both ends of the terminal in a monitoring period; acquiring resistance distribution parameters representing static and time domain characteristics of a crimping interface; calculating a resistance fluctuation index; calculating a contact defect index; obtaining an abnormal section and an abnormal section characteristic parameter; obtaining an average defect degree; calculating a quality risk index; determining a terminal fault grade, and generating visualized data; and generating a factory quality detection report. The present application solves the technical problems that the prior art cannot capture transient jitter and thermal drift, and lacks thermal damage evaluation.

Description

Technical Field

[0001] This invention relates to the field of conductive connection crimping quality testing technology. More specifically, this invention relates to a method for judging the crimping quality of cable branch box terminals based on dynamic resistance monitoring. Background Technology

[0002] Cable distribution boxes are used for node distribution and load transfer in urban power grids. The quality of the crimping of their internal terminals affects power transmission. During operation, the terminal crimping points are subjected to thermal expansion and contraction caused by alternating current and environmental mechanical vibration. If the crimping process does not meet the standards, the contact interface is prone to oxidation, leading to increased contact resistance and causing localized overheating or fire. Therefore, it is necessary to inspect the terminal crimping quality.

[0003] Current crimping quality inspection methods include mechanical pull-out force testing and static loop resistance testing. Mechanical pull-out force testing is a destructive test and cannot be used for the full inspection of finished products. Portable loop resistance testers usually measure the resistance value at a certain point in time when no large current is applied. Poor crimping can lead to instability of micro-contact spots. Under current-carrying conditions, this instability manifests as rapid fluctuations in resistance value and nonlinear increases with temperature.

[0004] Existing static testing equipment has a low sampling frequency and uses steady-state calculation methods, making it unable to capture these dynamic resistance change characteristics. This results in some terminals whose values ​​are within the acceptable range in static testing still exhibiting contact instability and overheating risks during actual operation. Due to thermal expansion and contraction caused by alternating loads and the influence of environmental micro-vibrations, simply measuring the transient resistance under conditions without high current flow cannot capture the dynamic contact behavior of terminals under actual operating conditions in real time. More importantly, existing steady-state sampling models struggle to distinguish between stable terminals with acceptable numerical values ​​but tight micro-contact and terminals with acceptable numerical values ​​but micro-looseness or nonlinear fluctuations upon heating. This confusion leads to extremely low sensitivity in identifying microstructural anomalies in crimping, making it difficult to effectively identify and warn of overheating faults in their early stages. Consequently, it fails to meet the requirements for distinguishing dynamic contact differences between terminals and achieving high-reliability quality control in complex current-carrying environments. Summary of the Invention

[0005] To address the technical problems of existing technologies failing to capture transient jitter and thermal drift, and lacking thermal damage assessment, this invention provides a method for judging the crimping quality of cable branch box terminals based on dynamic resistance monitoring, including:

[0006] The system synchronously acquires terminal voltage and current sequences at both ends of the terminals within the monitoring period. It compares the data from the same time point in the terminal voltage and current sequences to obtain a dynamic resistance sequence in chronological order. Based on statistical analysis, it obtains resistance distribution parameters characterizing the static and temporal characteristics of the crimping interface. According to the deviation of the resistance data in the dynamic resistance sequence from the overall level, it calculates the resistance fluctuation index to characterize the high-frequency vibration characteristics of the terminal contact surface. Based on the interaction between resistance fluctuation drift and thermal deviation during crimping failure, and the resistance fluctuation index, it calculates the contact defect index to characterize the degree of defects at the crimping point. Based on the statistical distribution characteristics of all contact defect indices within the monitoring period, it obtains abnormal sections and their characteristic parameters. It calculates the arithmetic mean of the contact defect indices corresponding to the abnormal sections to obtain the average defect degree. Based on the principle of thermal damage accumulation in crimping failure and the average defect degree, it calculates the quality risk index characterizing the probability of crimping failure. Based on the magnitude of all quality risk indices within the monitoring period, it judges the terminal fault level and generates visualized data. Finally, it packages the visualized data to generate a factory quality inspection report.

[0007] This invention achieves comprehensive and dynamic monitoring of terminal crimping quality through a series of steps, including data collection, feature extraction, relevant index calculation, anomaly identification, and risk assessment. This avoids the limitations of traditional single-data, static monitoring and reduces misjudgments and omissions. It enables early detection of potential quality issues, providing support for timely problem-solving, improving the accuracy and reliability of crimping quality assessment, meeting the needs of terminal quality control in complex environments, and ensuring the safe and stable transmission of electrical energy.

[0008] Preferably, the synchronous acquisition of the terminal voltage sequence and terminal current sequence across the terminals during the monitoring period includes:

[0009] During the monitoring period, the voltage data at both ends of the terminal and the current sequence of the circuit are captured synchronously using a high-frequency acquisition card, and the voltage and current data are denoised using a low-pass filter to obtain the terminal voltage sequence and terminal current sequence.

[0010] Preferably, obtaining resistance distribution parameters characterizing the static and time-domain features of the crimp interface includes:

[0011] By comparing the voltage and current data at the same time stamp in the terminal voltage sequence and terminal current sequence, a dynamic resistance sequence is obtained in chronological order. The arithmetic mean of the dynamic resistance sequence, the second central moment of the resistance distribution of the dynamic resistance sequence, the location of the first resistance data in the dynamic resistance sequence, the calculation of the first absolute value of the difference of the dynamic resistance sequence, the acquisition of the mean of the first absolute value of the difference of the dynamic resistance sequence, and the extraction of the resistance maxima and minima in the dynamic resistance sequence are recorded as resistance distribution parameters.

[0012] Preferably, the resistance fluctuation index satisfies the following expression:

[0013] ;

[0014] In the formula, Indicates the resistance fluctuation index; This refers to the resistance data in a dynamic resistance sequence. It is a uniform resistor; The rate of change of resistance; The average resistance gradient; The standard deviation of resistance; It is the first minimum positive number; This represents an exponential function with the natural constant as its base.

[0015] This invention can accurately capture subtle changes during terminal contact, clearly presenting imperceptible abnormal fluctuations, helping staff to promptly identify potential problems before they become serious, thus assisting in early troubleshooting and reducing the likelihood of subsequent failures.

[0016] Preferably, the contact defect index satisfies the following expression:

[0017] ;

[0018] In the formula, The contact defect index; This is the resistance fluctuation index; and These are the maximum and minimum resistance values, respectively. Used as a reference resistor; It is a uniform resistor; and These are the second and third smallest positive numbers; Represents the hyperbolic tangent function; Represents a logarithmic function.

[0019] This invention comprehensively considers various factors that may affect crimping quality, fully measures the degree of defects in terminal crimping, avoids the limitations of single-dimensional judgment, and makes the assessment of defects more in line with the actual situation. It neither misses out on real problems nor misjudges normal fluctuations as defects, thus improving the accuracy of defect judgment.

[0020] Preferably, obtaining the abnormal segment and its characteristic parameters includes:

[0021] The Otsu's method is used to adaptively segment all contact defect indices within the monitoring period using thresholds, identify anomalies with high defect responses, and connect temporally adjacent anomalies to form continuous anomaly segments. The duration of the anomaly segments is recorded as the anomaly segment duration, and the maximum deviation of the resistance data within the anomaly segment from the reference resistance is recorded as the resistance peak deviation. The anomaly segment duration and the resistance peak deviation are recorded as the anomaly segment characteristic parameters.

[0022] Preferably, obtaining the average defect rate includes:

[0023] Based on the duration of the abnormal segment, a corresponding subsequence is extracted from the contact defect index sequence consisting of all contact defect indices within the monitoring period, and the arithmetic mean of all contact defect indices in the subsequence is calculated to obtain the average defect degree.

[0024] Preferably, the quality risk index satisfies the following expression:

[0025] ;

[0026] In the formula, For quality risk index; The average defect rate; Duration of abnormal segments; This refers to the peak resistance deviation. Used as a reference resistor; It is the fourth smallest positive number; Represents an exponential function with the natural constant as its base; Represents a logarithmic function.

[0027] This invention scientifically assesses the risk level of terminal crimping by combining factors such as the severity and duration of defects. It can distinguish the urgency of different risks, help staff to rationally prioritize handling, use limited resources on high-risk issues, and improve the efficiency of quality control.

[0028] Preferably, terminal fault level is determined and visualized data is generated, including:

[0029] Three times the standard deviation of resistance is used as the first-level failure threshold, and six times the standard deviation of resistance is used as the second-level failure threshold. Terminals with quality risk indices less than the first-level failure threshold within the monitoring period are considered qualified. Terminals with quality risk indices greater than or equal to the first-level failure threshold and less than or equal to the second-level failure threshold within the monitoring period are considered suspected loose. Terminals with quality risk indices greater than the second-level failure threshold within the monitoring period are considered crimped failures. Visualized data containing terminal fault level and location information is generated.

[0030] This invention presents the fault level in a simple and easy-to-understand way, allowing staff to quickly grasp the terminal quality status without spending a lot of time interpreting complex data. At the same time, it intuitively marks the abnormal location and situation, facilitating subsequent tracing and troubleshooting, and improving the efficiency of work communication and processing.

[0031] Preferably, a factory quality inspection report is generated, including:

[0032] Once a crimping failure is detected, all visual data within the monitoring period are stored in the database in chronological order to generate a factory quality inspection report.

[0033] The beneficial effects of this invention are as follows: This invention provides a scientific and feasible solution for the quality inspection of cable branch box terminal crimping. The entire judgment process is clear and easy to operate, reducing the uncertainty caused by manual intervention, improving inspection efficiency, and lowering quality control costs. The generated inspection reports and related data provide strong support for production, operation, and maintenance, helping to standardize industry quality standards and promote the optimization and improvement of related processes. Simultaneously, by accurately identifying quality problems and providing early warnings of risks, it reduces subsequent failures caused by terminal crimping issues, ensuring the stable operation of related equipment and contributing to the safe and efficient development of related fields. Attached Figure Description

[0034] Figure 1 This diagram illustrates a flowchart of the cable branch box terminal crimping quality judgment method based on dynamic resistance monitoring in this invention.

[0035] Figure 2 The diagram illustrates the evolution mechanism of the quality risk index in this invention.

[0036] Figure 3 The schematic diagram illustrates the resistance dynamic monitoring grading determination and closed-loop feedback interface in this invention. Detailed Implementation

[0037] This invention discloses a method for judging the crimping quality of cable branch box terminals based on dynamic resistance monitoring, referring to... Figure 1 This includes steps S1-S4:

[0038] S1: Synchronously acquire the terminal voltage sequence and terminal current sequence at both ends of the terminal within the monitoring period.

[0039] It should be noted that in the terminal crimping quality inspection of cable branch boxes, the contact resistance is not a constant parameter, but a dynamic variable driven by the current thermal effect, microscopic contact surface roughness, and mechanical stress. Microscopically, the crimping interface consists of discrete contact spots. When there are defects in the crimping quality, these spots will generate extremely weak arc discharges or local breakdown of the oxide layer under high current pulses, manifesting as milliohm-level resistance jumps. If conventional low-frequency sampling is used, these high-frequency transient characteristics with failure precursors will be completely lost due to aliasing effects. Therefore, this invention utilizes high-frequency data acquisition technology to lock in real-time voltage and current fluctuations under pulsed current excitation. At the same time, considering the complex electromagnetic environment of industrial sites, the acquired signals are often superimposed with high-frequency random noise. Low-pass filtering is used for preprocessing to remove irrelevant electromagnetic interference, ensuring that the extracted voltage and current sequences can accurately reproduce the microscopic physical response of the crimping interface, laying a high signal-to-noise ratio data foundation for the subsequent construction of accurate dynamic resistance sequences.

[0040] Specifically, the terminal voltage sequence and terminal current sequence at both ends of the terminal are acquired synchronously during the monitoring period, including:

[0041] During the monitoring period, the voltage data at both ends of the terminal and the current sequence of the circuit are captured synchronously using a high-frequency acquisition card, and the voltage and current data are denoised using a low-pass filter to obtain the terminal voltage sequence and terminal current sequence.

[0042] Thus, the terminal voltage sequence and terminal current sequence at both ends of the terminal are obtained.

[0043] S2: Compare the data at the same time in the terminal voltage sequence and the terminal current sequence to obtain the dynamic resistance sequence in chronological order. Based on statistical analysis, obtain the resistance distribution parameters that characterize the static and time-domain characteristics of the crimping interface. According to the degree of deviation of the resistance data in the dynamic resistance sequence from the overall level, calculate the resistance fluctuation index to characterize the high-frequency jitter characteristics of the terminal contact surface. According to the interaction between the resistance fluctuation drift and thermal deviation when the crimp fails, and the resistance fluctuation index, calculate the contact defect index to characterize the degree of defects at the crimping point.

[0044] It should be noted that due to differences in material conductivity and contact area among different terminal models, their resistance reference values ​​exhibit a non-uniform distribution. From a statistical perspective, the mean resistance and standard deviation define the overall electrical boundary of the test, while the reference resistance captures the initial contact state of the terminal before thermal drift. The average gradient is introduced in this invention to calculate the dynamic rate of resistance evolution over time; this indicator can sensitively reflect the microscopic displacement frequency of the crimp interface under stress. The stability factor is set to eliminate singularities caused by hardware evaluation errors in subsequent nonlinear calculations. These fundamental characteristic parameters collectively constitute a multidimensional coordinate system, transforming abstract electrical signals into physically meaningful and comparable indicators. This allows subsequent anomaly diagnosis to effectively break free from dependence on fixed thresholds and achieve adaptive evaluation based on the terminal's own characteristics.

[0045] Specifically, by comparing data from the same time point in the terminal voltage sequence with those from the terminal current sequence, a dynamic resistance sequence is obtained in chronological order. Based on statistical analysis, resistance distribution parameters characterizing the static and time-domain features of the crimp interface are acquired, including:

[0046] By comparing the voltage and current data at the same time stamp in the terminal voltage sequence and terminal current sequence, a dynamic resistance sequence is obtained in chronological order. The arithmetic mean of the dynamic resistance sequence, the second central moment of the resistance distribution of the dynamic resistance sequence, the location of the first resistance data in the dynamic resistance sequence, the calculation of the first absolute value of the difference of the dynamic resistance sequence, the acquisition of the mean of the first absolute value of the difference of the dynamic resistance sequence, and the extraction of the resistance maxima and minima in the dynamic resistance sequence are recorded as resistance distribution parameters.

[0047] Thus, the resistance distribution parameters characterizing the static and time-domain features of the press-fit interface were obtained.

[0048] It should be noted that the resistance of a well-pressed terminal exhibits a smooth evolution trend with current flow, showing a low local gradient. However, terminals with microcracks or looseness will experience intermittent poor contact under current stress, causing high-frequency transient fluctuations in resistance. Physically, this fluctuation is characterized by a significantly higher local gradient than the global average. To address this phenomenon, relying solely on the absolute value of the deviation can easily misjudge normal resistance drift caused by ambient temperature rise as a contact defect. Therefore, it is necessary to introduce the local gradient as a weighting factor for the fluctuation characteristics and nonlinearly modulate the grayscale deviation energy. This invention constructs an exponential sensitive response operator, enabling the extracted resistance fluctuation index to specifically amplify high-frequency jump characteristics, thereby suppressing smooth, slowly changing signals. This allows for the accurate extraction of core indicators reflecting the physical stability of the contact surface from complex dynamic sequences, directly linking this index to the microstructural integrity of the press-fit surface.

[0049] Preferably, based on the degree of deviation of the resistance data in the dynamic resistance sequence relative to the overall level, a resistance fluctuation index is calculated to characterize the high-frequency jitter characteristics of the terminal contact surface, including:

[0050] The resistance fluctuation index satisfies the following expression:

[0051] ;

[0052] In the formula, Indicates the resistance fluctuation index; This refers to the resistance data in a dynamic resistance sequence. It is a uniform resistor; The rate of change of resistance; The average resistance gradient; The standard deviation of resistance; It is the first minimum positive number; This represents an exponential function with the natural constant as its base.

[0053] In the formula, In a physical sense, it reflects the deviation of the local resistance from the global background energy; As a sensitive response operator, a variant of the negative exponential structure is used to amplify the contribution of local high-frequency jitter to the fluctuation exponent, thereby suppressing low-frequency slow-varying interference and highlighting the characteristic transients caused by poor crimping; in the denominator Adaptive normalization for global background noise levels has been achieved.

[0054] For example, if =10mΩ, Case 1 exists: For tightly crimped terminals, the resistance curve is smooth. Extremely small, calculated The value is 1.05; Scenario 2: For terminals with microcracks, the resistance exhibits high-frequency fluctuations after heating. Increase, calculated The result is 45.6. The calculation results 1.05 and 45.60 are rounded to two decimal places.

[0055] Thus, the resistance fluctuation index, used to characterize the high-frequency jitter characteristics of the terminal contact surface, was obtained.

[0056] It should be noted that terminal crimping failure is usually accompanied by the coexistence of three physical phenomena: transient jitter, static temperature rise, and significant extreme value drift. While a single-dimensional fluctuation index can capture jitter, it may be insensitive to persistent high-temperature drift caused by insufficient contact area, i.e., an overall increase in resistance and a decrease in fluctuation. Therefore, this invention constructs a comprehensive evaluation model that integrates transient and steady-state characteristics. From the perspective of electrical contact, the resistance range reflects the dynamic instability width of the contact interface, while the ratio of the mean to the reference value is directly related to the Joule heat accumulation at the crimping point. By coupling the fluctuation index sequence with the nonlinearly mapped drift amplitude and thermal deviation, the defect index will only jump when the detection point simultaneously exhibits unstable fluctuation, large dynamic displacement, and a significant increase in resistance. This ensures that the extracted index accurately reflects the true defect degree of the crimping point and eliminates false warnings caused by single-point spike pulses.

[0057] Preferably, based on the interaction between the resistance fluctuation drift and thermal deviation during crimping failure, and the resistance fluctuation index, a contact defect index is calculated to characterize the degree of defects at the crimping point, including:

[0058] The contact defect index satisfies the following expression:

[0059] ;

[0060] In the formula, The contact defect index; This is the resistance fluctuation index; and These are the maximum and minimum resistance values, respectively. Used as a reference resistor; It is a uniform resistor; and These are the second and third smallest positive numbers; Represents the hyperbolic tangent function; Represents a logarithmic function.

[0061] In the formula, The relative drift amplitude is saturated and mapped to the (0,1) interval to determine the absolute macroscopic scale of fluctuations and suppress the numerical shock of outliers. By characterizing the thermal rise effect of resistance during current flow, the heating caused by the heat generation is investigated. Much larger than the initial The physical phenomenon provides nonlinear gain; Cross-validation of crimping defects in terms of fluctuation, displacement, and temperature rise was achieved.

[0062] For example, if the reference parameters are fixed, there is a case where: when the pressing is good, the temperature rise is small and there is no fluctuation, and the calculation yields... The value is 0.02; Case 2 exists: when the crimp connection is faulty, it is accompanied by rapid temperature rise and resistance jump, and the calculated value is... The result is 18.90. The above calculation results, 0.02 and 18.90, are rounded to two decimal places.

[0063] Thus, the contact defect index was obtained.

[0064] S3: Based on the statistical distribution characteristics of all contact defect indices within the monitoring period, obtain the abnormal sections and their characteristic parameters; calculate the arithmetic mean of the contact defect indices corresponding to the abnormal sections to obtain the average defect degree; based on the principle of thermal damage accumulation in crimping failure, calculate the quality risk index used to characterize the possibility of crimping failure based on the average defect degree.

[0065] It should be noted that physical failures often exhibit temporal persistence and spatial clustering, rather than being isolated random noise points. During continuous monitoring of crimp terminals, sporadic exponential jumps may occur due to external vibrations or instantaneous high currents, but these signals typically lack sustained physical destructive power. To define true quality defects, this invention, from a probability distribution perspective, seeks response intervals in the exponential sequence that significantly deviate from the conventional distribution. Using the OTSU maximum inter-class variance method, anomaly detection thresholds can be adaptively determined, automatically separating background and defect states. Further, clustering and connection are performed using time windows to extract physically continuous anomalous segments. By statistically analyzing the duration and peak deviation of these segments, abstract algorithmic values ​​can be transformed into physical representations consistent with power operation and maintenance practices. In other words, these segments reflect the energy release scale and impact range of the terminal during the crimp failure evolution process.

[0066] Specifically, based on the statistical distribution characteristics of all contact defect indices within the monitoring period, abnormal sections and their characteristic parameters are obtained, including:

[0067] The Otsu's method is used to adaptively segment all contact defect indices within the monitoring period using thresholds, identify anomalies with high defect responses, and connect temporally adjacent anomalies to form continuous anomaly segments. The duration of the anomaly segments is recorded as the anomaly segment duration, and the maximum deviation of the resistance data within the anomaly segment from the reference resistance is recorded as the resistance peak deviation. The anomaly segment duration and the resistance peak deviation are recorded as the anomaly segment characteristic parameters.

[0068] Thus, the abnormal segment and its characteristic parameters were obtained.

[0069] It should be noted that while a single peak deviation reflects the most severe instant, it cannot represent the average damage level throughout the entire abnormal period. To more comprehensively assess risk, this invention incorporates the overall defect level within the abnormal section. From the evolutionary pattern of crimping defects, the microscopic damage to the terminal crimping interface is a gradual cumulative process. The contact defect index within the abnormal section is not constant and may exhibit multiple fluctuating peaks and flattening sections. Furthermore, the subsequent calculation of the quality risk index requires a basis in the overall defect level of the abnormal section. Peak deviation only reflects the extreme degree of the defect and cannot provide comprehensive numerical support for risk assessment. Therefore, this invention introduces the parameter of average defect degree. By taking the arithmetic mean of all contact defect indices within the abnormal section, the interference of instantaneous extreme values ​​is smoothed out, and the average damage state of the crimping interface throughout the entire abnormal period is accurately calculated.

[0070] Preferably, the arithmetic mean of the contact defect indices corresponding to the abnormal sections is calculated to obtain the average defect degree, including:

[0071] Based on the duration of the abnormal segment, a corresponding subsequence is extracted from the contact defect index sequence consisting of all contact defect indices within the monitoring period, and the arithmetic mean of all contact defect indices in the subsequence is calculated to obtain the average defect degree.

[0072] It is important to note that the final evaluation of crimping quality must be based on long-term operational safety, i.e., risk assessment. From a reliability engineering perspective, failure risk is a composite function of defect intensity and defect duration. A disturbance with an extremely high peak but a very short duration causes far less cumulative thermal damage to the terminal than a loose contact with a lower peak but a longer duration. Therefore, a hazard tradeoff operator needs to be introduced. By nonlinearly coupling the average defect intensity within a section with a logarithmically corrected time factor and an exponentially corrected intensity operator, a risk assessment index that comprehensively reflects the activity of defect evolution and the scale of hazard can be established. The exponential operator is introduced to simulate the squared growth trend of heat generation power after the resistance deviates from the reference, while the logarithmic operator is used to balance the contribution of long-term data to the risk value, ensuring that the output risk index can scientifically guide the classification of terminals and prioritize the treatment of potential hazards with high-intensity heat accumulation risk.

[0073] Preferably, based on the principle of thermal damage accumulation in crimping failure, and based on the average defect degree, a quality risk index is calculated to characterize the probability of crimping failure, including:

[0074] The quality risk index satisfies the following expression:

[0075] ;

[0076] In the formula, For quality risk index; The average defect rate; Duration of abnormal segments; This refers to the peak resistance deviation. Used as a reference resistor; It is the fourth smallest positive number; Represents an exponential function with the natural constant as its base; Represents a logarithmic function.

[0077] In the formula, It is used to measure the cumulative failure risk caused by defect persistence, that is, to use the linear divergence of the logarithmic suppression time scale. As an intensity evolution operator, when the resistance deviates from the amplitude Approximate reference resistance At this time, the exponential term triggers a nonlinear surge in the risk value, thus reflecting the risk of ablation caused by the dramatic increase in the heating power of the crimping point.

[0078] For example, if Similarly, scenario one exists: an occasional, short-term interference, in which... Small and Small, calculated The value is 5.4; Scenario 2 exists: a persistent loose contact, in which... large and achieve 50%, calculated The result is 38.5. The above calculation results, 5.4 and 38.5, are rounded to one decimal place.

[0079] It should be noted that, Figure 2 This diagram illustrates the evolution mechanism of the quality risk index, showing how it changes under different combinations of resistance peak deviation and abnormal segment duration. Two typical examples are included: Example 1 represents an intermittent interference situation (T=2, V=0.5m, Q=5.4); Example 2 represents a continuous loosening situation (T=5100, V=5.0m, Q=38.5). The diagram also presents the evolution trend of the quality risk index with resistance peak deviation under three different duration dimensions: short-duration pulse, medium-duration, and continuous fault. This variation reflects the correlation between the quality risk index and resistance peak deviation and abnormal segment duration; that is, the larger the resistance peak deviation and the longer the abnormal segment duration, the higher the quality risk index, providing data support for risk assessment of terminal crimping quality.

[0080] Thus, a quality risk index was obtained to characterize the probability of crimping failure.

[0081] S4: Based on the magnitude of all quality risk indices within the monitoring period, determine the terminal fault level and generate visualized data; package the visualized data and generate a factory quality inspection report.

[0082] It should be noted that industrial testing decisions require extremely simple logical feedback, while the algorithm must possess strong scenario robustness. Because cable terminals produced in different batches and on different production lines exhibit slight fluctuations in their initial processes, a single, fixed judgment threshold can easily lead to misjudgments of qualified products or missed detections of defective products. This invention constructs a tiered threshold by using the standard deviation of the environment's resistance as a dynamic reference base. Essentially, it sets a quality assessment system for each tested terminal based on its own electrical background. This dynamic threshold mechanism is similar to setting a floating water level for the sensor, which automatically shields interference caused by fluctuations in the process baseline. Through thermodynamic pseudo-color mapping, the judgment result is intuitively superimposed on the original resistance waveform, transforming the complex mathematical model into a color space that is discernible to the naked eye. This assists in rapid human decision-making, realizing the transformation from abstract data to intuitive quality rating.

[0083] Specifically, based on the magnitude of all quality risk indices within the monitoring period, the terminal fault level is determined, and visualized data is generated, including:

[0084] A dynamic grading threshold is constructed based on the second-order features of the resistance distribution. The quality risk index is then discretized and mapped to different levels, and pseudo-color visual enhancement processing is applied to obtain grading and rating conclusions, including:

[0085] Take three times the standard deviation of the resistance as the first - level failure threshold, and six times the standard deviation of the resistance as the second - level failure threshold. Determine that the terminal quality at the corresponding moment of the quality risk index less than the first - level failure threshold among all quality risk indexes within the monitoring period is qualified, and output a green safety instruction; determine that the terminal quality at the corresponding moment of the quality risk index greater than or equal to the first - level failure threshold and less than or equal to the second - level failure threshold among all quality risk indexes within the monitoring period is suspected of being loose, and output a yellow warning signal; determine that the terminal quality at the corresponding moment of the quality risk index greater than the second - level failure threshold among all quality risk indexes within the monitoring period is crimping failure, and output a red stop signal; use the pseudo - color mapping technology to mark the abnormal section on the resistance - time curve to generate visualization data containing terminal fault levels and location information.

[0086] It should be noted that in the anomaly detection of industrial big data, the present invention constructs a hierarchical defense line based on the statistical normal distribution law. For a qualified crimping process in a steady state, most of the data fluctuation amplitudes should be limited within three times the standard deviation range. Therefore, three times the standard deviation is set as the first - level warning threshold. When the quality risk index breaks through this defense line, it indicates that the current resistance fluctuation is an abnormal event in terms of probability, which physically corresponds to micro - loosening or initial oxidation of the crimping interface. Further, six times the standard deviation is set as the second - level failure threshold. If the fluctuation amplitude exceeds six times the background noise, it means that the signal contains extremely strong non - random mutation energy, which physically corresponds to macroscopic contact separation or arc ablation, and is confirmed as crimping failure.

[0087] It should be noted that Figure 3 is the interface for hierarchical determination and closed - loop feedback of dynamic resistance monitoring. This figure shows the change of dynamic resistance value during the monitoring time, the marking of abnormal sections, and the hierarchical determination results of quality risk indexes. The interface includes a suspected - loosening threshold line and a crimping - failure determination threshold line. When the quality risk index is 5.4, it corresponds to an occasional interference situation, and its value is lower than the suspected - loosening threshold, and the terminal state meets the requirements; when the quality risk index reaches 38.5, it corresponds to a continuous loosening situation, and its value is higher than the crimping - failure determination threshold, and the system triggers a stop instruction and generates a quality inspection report. The interface marks the abnormal section through pseudo - color mapping, visually presenting the fluctuation of dynamic resistance value over time and the quality risk level, which can assist in quickly identifying different states of terminal crimping and providing a clear basis for subsequent processing.

[0088] Thus, visualization data containing terminal fault levels and location information is obtained.

[0089] It should be noted that the ultimate goal of dynamic monitoring is to build a closed-loop management system for production quality. In the production and maintenance of power fittings, simple offline testing cannot intervene in process deviations in real time. This invention establishes a real-time communication link with the crimping equipment. When the system detects a significant crimping failure response, it automatically issues a shutdown command. This is an advanced preventive mechanism based on defect early warning rather than post-failure repair. This closed-loop control can minimize the production of defective products and reduce the company's quality costs. At the same time, the waveform characteristics, risk index, and judgment results of the entire process are structured and stored to generate a legally valid factory quality inspection report. This not only provides quality traceability evidence throughout the product's lifecycle but also provides core data samples for subsequent analysis of the correlation between the crimping process and terminal performance using big data methods, promoting continuous improvement and iteration of the crimping process.

[0090] Preferably, the visualized data is packaged to generate a factory quality inspection report, including:

[0091] Once a crimping failure is detected, all visual data within the monitoring period are stored in the database in chronological order to generate a factory quality inspection report.

[0092] Thus, a method for judging the crimping quality of cable branch box terminals based on dynamic resistance monitoring was completed.

[0093] While various embodiments of the invention have been shown and described in this specification, it will be apparent to those skilled in the art that such embodiments are provided by way of example only. Many modifications, alterations, and alternatives will occur to those skilled in the art without departing from the spirit and essence of the invention.

Claims

1. A method for judging the quality of cable branch box terminal crimping based on dynamic resistance monitoring, characterized in that, include: Simultaneously acquire the terminal voltage sequence and terminal current sequence at both ends of the terminal within the monitoring period; By comparing the data at the same time in the terminal voltage sequence and the terminal current sequence, a dynamic resistance sequence is obtained in chronological order. Based on statistical analysis, resistance distribution parameters characterizing the static and time-domain characteristics of the crimping interface are obtained. According to the degree of deviation of the resistance data in the dynamic resistance sequence from the overall level, the resistance fluctuation index used to characterize the high-frequency jitter characteristics of the terminal contact surface is calculated. According to the interaction between the resistance fluctuation drift and thermal deviation when the crimp fails, and the resistance fluctuation index, the contact defect index used to characterize the degree of defects at the crimping point is calculated. Based on the statistical distribution characteristics of all contact defect indices within the monitoring period, abnormal sections and their characteristic parameters are obtained; the arithmetic mean of the contact defect indices corresponding to the abnormal sections is calculated to obtain the average defect degree. Based on the principle of thermal damage accumulation in crimping failure, a quality risk index is calculated to characterize the probability of crimping failure, based on the average defect degree. Based on the magnitude of all quality risk indices within the monitoring period, the terminal fault level is determined and visualized data is generated; the visualized data is packaged and a factory quality inspection report is generated. The resistance fluctuation index satisfies the following expression: In the formula, Indicates the resistance fluctuation index; This refers to the resistance data in a dynamic resistance sequence. It is a uniform resistor; The rate of change of resistance; The average resistance gradient; The standard deviation of resistance; It is the first minimum positive number; Represents an exponential function with the natural constant as the base; The contact defect index satisfies the following expression: In the formula, The contact defect index; and These are the maximum and minimum resistance values, respectively. Used as a reference resistor; and These are the second and third smallest positive numbers; Represents the hyperbolic tangent function; Represents a logarithmic function; The quality risk index satisfies the following expression: In the formula, For quality risk index; The average defect rate; Duration of abnormal segments; This refers to the peak resistance deviation. Used as a reference resistor; It is the fourth smallest positive number.

2. The method for judging the terminal crimping quality of cable branch boxes based on dynamic resistance monitoring according to claim 1, characterized in that, The synchronous acquisition of the terminal voltage sequence and terminal current sequence at both ends of the terminal during the monitoring period includes: During the monitoring period, the voltage data at both ends of the terminal and the current sequence of the circuit are captured synchronously using a high-frequency acquisition card, and the voltage and current data are denoised using a low-pass filter to obtain the terminal voltage sequence and terminal current sequence.

3. The method for judging the terminal crimping quality of cable branch boxes based on dynamic resistance monitoring according to claim 1, characterized in that, The acquisition of resistance distribution parameters characterizing the static and time-domain features of the press-fit interface includes: By comparing the voltage and current data at the same time stamp in the terminal voltage sequence and terminal current sequence, a dynamic resistance sequence is obtained in chronological order. The arithmetic mean of the dynamic resistance sequence, the second central moment of the resistance distribution of the dynamic resistance sequence, the location of the first resistance data in the dynamic resistance sequence, the calculation of the first absolute value of the difference of the dynamic resistance sequence, the acquisition of the mean of the first absolute value of the difference of the dynamic resistance sequence, and the extraction of the resistance maxima and minima in the dynamic resistance sequence are recorded as resistance distribution parameters.

4. The method for judging the terminal crimping quality of cable branch boxes based on dynamic resistance monitoring according to claim 1, characterized in that, The acquisition of the abnormal segment and its characteristic parameters includes: The Otsu's method is used to adaptively segment all contact defect indices within the monitoring period using thresholds, identify anomalies with high defect responses, and connect temporally adjacent anomalies to form continuous anomaly segments. The duration of the anomaly segments is recorded as the anomaly segment duration, and the maximum deviation of the resistance data within the anomaly segment from the reference resistance is recorded as the resistance peak deviation. The anomaly segment duration and the resistance peak deviation are recorded as the anomaly segment characteristic parameters.

5. The method for judging the terminal crimping quality of cable branch boxes based on dynamic resistance monitoring according to claim 1, characterized in that, The process of obtaining the average defect rate includes: Based on the duration of the abnormal segment, a corresponding subsequence is extracted from the contact defect index sequence consisting of all contact defect indices within the monitoring period, and the arithmetic mean of all contact defect indices in the subsequence is calculated to obtain the average defect degree.

6. The method for judging the terminal crimping quality of cable branch boxes based on dynamic resistance monitoring according to claim 1, characterized in that, The process of determining the terminal fault level and generating visualized data includes: Three times the standard deviation of resistance is used as the first-level failure threshold, and six times the standard deviation of resistance is used as the second-level failure threshold. Terminals with quality risk indices less than the first-level failure threshold within the monitoring period are considered qualified. Terminals with quality risk indices greater than or equal to the first-level failure threshold and less than or equal to the second-level failure threshold within the monitoring period are considered suspected loose. Terminals with quality risk indices greater than the second-level failure threshold within the monitoring period are considered crimped failures. Visualized data containing terminal fault level and location information is generated.

7. The method for judging the terminal crimping quality of cable branch boxes based on dynamic resistance monitoring according to claim 1, characterized in that, The generation of the factory quality inspection report includes: Once a crimping failure is detected, all visual data within the monitoring period are stored in the database in chronological order to generate a factory quality inspection report.

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