Short-circuit overload protection device and method for small general-purpose aircraft circuit

Abstract

The invention relates to the technical field of aircraft electrical systems, in particular to a small general-purpose aircraft circuit short circuit overload protection device and method. According to the technical scheme, the circuit short circuit and overload protection device for the small general-purpose aircraft comprises a fuse box, and a fuse, a fuse seat, a relay and a connector are integrated in the fuse box; the fuse is installed through a fuse seat and is used for circuit short circuit protection. The relay is used for monitoring current overload and controlling on-off of a circuit. The connector is configured to be two-way input and one-way output and supports 28.5 VDC voltage, the input current is smaller than 25A, and the output current is 2A. The integrated structure remarkably improves the space utilization efficiency, and installation and maintenance are more convenient and efficient. The intelligent protection mechanism can accurately identify various fault features, and ensures the accuracy and timeliness of the protection action. The self-adaptive capability of the system enables the system to dynamically optimize protection parameters according to the actual operation condition, and the optimal working state is kept.

Description

Technical Field

[0001] This invention relates to the field of aircraft electrical systems technology, and in particular to a short-circuit overload protection device and method for small general-purpose aircraft circuits. Background Technology

[0002] The traditional fuse boxes commonly used in existing small general aviation aircraft have significant limitations. This device is currently discontinued, leading to serious difficulties in maintenance and replacement. Due to the specific requirements of the aviation industry, the procurement cycle for new equipment is lengthy and costly, failing to meet the urgent needs of continuous aircraft operation. More importantly, the lack of effective circuit protection devices directly jeopardizes flight safety, potentially causing damage to electrical equipment in the event of short circuits or overloads. This technological gap not only affects the normal operation of aircraft but also makes it difficult for existing aircraft to meet increasingly stringent airworthiness regulations.

[0003] Traditional protection schemes are relatively simple in design and lack intelligent protection mechanisms, making them unable to meet the development needs of modern avionics systems. The absence of protection devices leaves aircraft circuit systems without effective protection under abnormal operating conditions, potentially triggering a chain reaction of equipment failures. This current technological situation severely restricts the improvement of reliability and safety in small general aviation aircraft.

[0004] Therefore, the core issues that need to be addressed are how to achieve coordinated protection of multiple circuits, how to ensure the accuracy and timeliness of protection actions, and how to simplify the installation and maintenance process.

[0005] Secondly, it is crucial to integrate comprehensive protection functions within a limited space while ensuring the reliability and environmental adaptability of the device. Furthermore, the lack of intelligent monitoring capabilities in traditional protection devices needs to be addressed, enhancing the system's self-protection and comprehensive functions. Solving these technical problems directly impacts the safe operation and continued airworthiness of the aircraft's electrical systems. Summary of the Invention

[0006] This invention proposes a short-circuit overload protection device and method for small general aviation aircraft circuits, which solves the problem of accurate protection and intelligent coordinated control of small general aviation aircraft circuit systems under multiple fault conditions in the prior art.

[0007] To solve the above-mentioned technical problems, the technical solution adopted by the present invention is as follows: A small general-purpose aircraft circuit short-circuit and overload protection device includes a fuse box, which integrates a fuse, a fuse holder, a relay, and a connector. The fuse is mounted via the fuse holder and is used for circuit short-circuit protection. The relay is used to monitor current overload and control circuit on / off. The connector is configured with two inputs and one output, supporting 28.5VDC DC voltage, an input current of less than 25A, and an output current of 2A.

[0008] Furthermore, the fuses are 34 type 520 2A fuses, and the fuse holders are 34 type F0321 520 holders; the relays are type JKM-S2 / 116; the fuse box is fixed to the aircraft frame 1, and there is no need to modify the original structure of the aircraft.

[0009] A method for protecting the circuits of a small general-purpose aircraft based on the above-mentioned device includes the following steps: Dynamic parameter acquisition steps: The instantaneous values ​​and rate of change of current in each branch are acquired in real time through the connectors inside the fuse box; Intelligent judgment steps: Identify the fault type by analyzing the current-time characteristic curve; Graded protection steps: The three-level protection mechanism is activated according to the severity of the fault.

[0010] Furthermore, the intelligent judgment step also includes an adaptive learning mechanism: analyzing historical operating data through machine learning algorithms to establish a device load characteristic model; automatically correcting the protection threshold based on ambient temperature; and dynamically adjusting the protection characteristic curve based on the degree of device aging.

[0011] Furthermore, the hierarchical protection steps specifically include the following collaborative control strategies: Establish a "judgment-then-action" logic coordination mechanism between fuses and relays. When an overcurrent signal is detected, the fault level is first determined by the comparator circuit. If it is a momentary overcurrent (≥30A), the fuse will act within 5ms. If it is a continuous overload (25-30A), the relay will act after 50ms. Set up a protection action priority matrix and dynamically adjust the action sequence according to the fault type and equipment importance. For critical equipment branches, adopt the fuse priority action strategy and for non-critical branches, adopt the relay priority judgment strategy. The design incorporates an intelligent decision-making algorithm for fault isolation and power restoration. By monitoring the voltage recovery characteristics after fault clearance, it automatically determines whether to perform a reclosing operation, thus avoiding repeated power supply to permanently faulty lines.

[0012] Furthermore, the system self-test and diagnostic steps specifically include: The power-on self-test program automatically performs a full-circuit impedance test before the aircraft is powered on. It detects the connectivity of each branch by injecting a 1mA test current, and scans each of the 34 fuse paths one by one, recording the reference resistance value of each path. The online monitoring system collects fuse temperature rise data in real time, predicts fuse aging status through temperature-current relationship model, and automatically issues an early warning signal when the fuse base temperature rises abnormally (exceeding 50°C of ambient temperature). The fault recording device records the electrical parameter waveforms from 200ms before the protection action to 500ms after the action at a sampling rate of 10kHz, and stores complete data of the most recent 10 faults, including the current phase and amplitude change trajectory of each branch and the relay action sequence.

[0013] Furthermore, the early warning and maintenance steps are implemented in the following ways: Predicting remaining life based on the cumulative thermal effect model of fuses, and establishing I 2 The t-accumulation algorithm calculates the heat accumulation value of each fuse in real time and issues a replacement warning when it reaches 80% of the rated value. The maintenance recommendation system automatically generates optimization solutions based on historical fault statistics. For frequently activated branches, it recommends upgrading the fuse capacity or checking the load equipment, and also provides a priority list of spare parts for replacement. The remote diagnostic interface supports the RS-422 avionics bus protocol and can output a complete device operating status frame, including real-time current of each branch, fuse status words, relay operation count statistics, and fault code description table.

[0014] Furthermore, the reliability enhancement measures specifically include: A dual-redundant acquisition scheme is adopted, with key signals being sampled synchronously through independent ADC channels. A difference comparison threshold (±2%) is set, and the system automatically switches to the backup channel when the data deviation between the two channels exceeds the limit. The watchdog monitoring mechanism employs a three-level protection system: the software watchdog refreshes every 100ms, the hardware watchdog is set with a 1.5s timeout threshold, and the power monitoring chip monitors the power supply quality in real time (fluctuation range ±5%). The power failure self-recovery function saves the system state through non-volatile memory. When power is lost, the current parameters are automatically stored, and after power is restored, the status verification and recovery algorithm achieves seamless resume, ensuring the continuity of protection actions.

[0015] Furthermore, the airworthiness compliance guarantee is achieved through the following methods: Each flight cycle automatically generates a protection system operation report that meets FAA format requirements, including statistics on the number of protection actions, response time analysis (requirement <100ms), fault type distribution, and device availability calculation (target value ≥99.9%). The verification test uses the step load mutation method to simulate various fault scenarios and verify the accuracy of the protection action. The requirements are that the short-circuit protection response error is <5% and the overload protection delay error is <10%. The airworthiness compliance documentation system includes all test items required by CCAR-23, especially the protection performance verification data under high-altitude low-pressure environment (simulating an altitude of 8,000 meters).

[0016] Furthermore, the system optimization functions include: An adaptive parameter optimization algorithm based on operational data automatically adjusts protection curve parameters by analyzing historical fault characteristics and uses the least squares method to fit the optimal protection characteristic equation. The remote upgrade system supports differential incremental updates, verifies firmware integrity through digital signatures, and maintains basic protection functions uninterrupted during the upgrade process. The data statistics and analysis engine can generate multi-dimensional operation reports, including branch load rate statistics, protection action success rate analysis, and device reliability trend prediction, and supports output in multiple formats such as PDF / Excel.

[0017] The positive effects of this invention are: The integrated structure of the device significantly improves space utilization efficiency, making installation and maintenance more convenient and efficient. The intelligent protection mechanism accurately identifies various fault characteristics, ensuring the precision and timeliness of protection actions. The system's adaptive capability allows it to dynamically optimize protection parameters based on actual operating conditions, maintaining optimal working performance.

[0018] This invention also demonstrates excellent compatibility and scalability, adapting to the installation requirements of different aircraft models. Through modular design and standardized interfaces, it significantly reduces maintenance costs throughout the entire lifecycle. Multiple reliability safeguards ensure stable system operation under various conditions, providing solid technical support for flight safety.

[0019] Innovative self-protection and improvement functions enable the system to continuously optimize, while a comprehensive verification system ensures the airworthiness compliance of the device. Attached Figure Description

[0020] Figure 1 This is a schematic diagram of the fuse box principle in this invention; Detailed Implementation

[0021] The technical solutions of the present invention will be clearly and completely described below with reference to the embodiments of the present invention. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative effort are within the scope of protection of the present invention.

[0022] Example 1 Combination Figure 1As shown, a small general aviation aircraft circuit short-circuit and overload protection device includes a fuse box, which integrates a fuse, a fuse holder, a relay, and a connector. The fuse is mounted through the fuse holder and is used for circuit short-circuit protection. The relay is used to monitor current overload and control circuit on / off. The connector is configured with 2 inputs and 1 output, supports 28.5VDC DC voltage, input current less than 25A, and output current of 2A.

[0023] The fuse box is made of aerospace-grade aluminum alloy (model 7075-T6), a material known for its high strength-to-weight ratio, with a tensile strength of 524 MPa and a yield strength of 455 MPa. The box dimensions have been precisely calculated, with a volume design of 200 mm (length) × 150 mm (width) × 80 mm (height) based on the installation space requirements of 34 fuses and their associated components. The box surface undergoes a hard anodizing treatment with a film thickness of 20-25 μm and a surface resistivity greater than 10⁻⁶. 12 Ω·cm, ensuring good insulation performance even in humid salt spray environments.

[0024] The internal design of the enclosure features a modular, layered structure: the upper mounting plate is 2mm thick and has 34 φ10mm mounting holes with a hole spacing accuracy of ±0.1mm; the middle layer has shock-absorbing brackets for the relay mounting positions, using silicone rubber shock absorbers with a natural frequency of 25Hz, effectively isolating aircraft vibrations; the lower connector interface board is 1.5mm thick and uses a recessed mounting method to ensure airtightness. The heat dissipation fins on both sides of the enclosure are 15mm high and spaced 8mm apart, calculated to maintain a temperature rise of no more than 40K under maximum power consumption conditions.

[0025] The input / output connectors are JY2748 series 28-pin aviation connectors, with gold-plated contacts (plating thickness 0.76μm) and contact resistance less than 2mΩ. IN1 input terminal definitions: pins 1-17 correspond to fuse inputs 1-17; IN2 input terminals 18-34 correspond to fuse inputs 18-34; the OUT output terminals use a parallel output configuration. The fuse holder is the F0321 model with an indicator function, featuring a built-in microswitch that automatically triggers the indicator light circuit when the fuse blows.

[0026] The relay selected is a JKM-S2 / 116 type magnetic latching relay, with a coil resistance of 650Ω±10%, a pull-in voltage of 18VDC, a release voltage of 4VDC, and a mechanical life of 10. 6 The contact material is silver tin oxide, with a contact pressure greater than 300g and a contact resistance less than 50mΩ.

[0027] Under normal operating conditions, the current path is: input connector → fuse → normally closed relay contact → output connector. The selection of the fuse's 2A rated current is based on detailed thermal calculations: first, the maximum operating current of each electrical device is measured (peak value 1.3A), a safety factor of 1.2 is considered, and then an ambient temperature correction factor is added (derating factor of 0.8 at a maximum temperature of 85℃), ultimately determining 2A as the optimal value.

[0028] The relay overload protection is based on the thermal memory principle: the internal bimetallic strip accumulates heat during overcurrent, and its deformation rate is proportional to the square of the current. When the continuous overload reaches 125% of the rated current, the operating time is set to be adjustable from 20 to 60 seconds to ensure a time difference matching with the fast-breaking characteristic of the fuse.

[0029] The integrated design of the fuse box consolidates disparate protective components into a unified module, significantly improving the device's compactness and reliability. This integrated structure not only optimizes internal space layout but also simplifies installation, allowing the protection device to better adapt to the space constraints of small general aviation aircraft. The coordinated arrangement of fuses and relays ensures the stability of electrical connections, while the standardized design of connectors improves system maintainability.

[0030] The fuses consist of 34 type 520 2A fuses, and the fuse holders consist of 34 type F0321 520 fuse holders; the relays are type JKM-S2 / 116; the fuse boxes are fixed to the aircraft frame 1 without altering the original aircraft structure.

[0031] The installation location is chosen in the reinforcing rib area of ​​frame 1 of the aircraft, where the structural rigidity is greatest and the vibration acceleration is less than 5g. The installation interface adopts a special vibration damping design: the anti-vibration pad is made of fluorosilicone rubber, 3mm thick, with a Shore hardness of 50±5 and a compression set of less than 15%. Four M5 stainless steel screws (strength grade A2-70) are tightened in a symmetrical cross-shaped sequence, with the torque controlled at 4.5N·m±0.5N·m.

[0032] The conductor selection is based on detailed calculations: the main circuit uses AF250-2.5 type polytetrafluoroethylene conductors with a cross-sectional area of ​​2.5mm². 2 The allowable long-term operating temperature is 200℃. Cable spacing is 150mm, and the bending radius is greater than 6 times the outer diameter of the conductor. All terminals use HS series crimp terminals with a crimping pressure of 3-5kN and a pull-out force greater than 200N.

[0033] The Type 520 fuse is a fast-acting model, and its fusing characteristics have been verified by actual testing: the operating time is less than 2 seconds at 200% overcurrent and less than 0.1 seconds at 500% overcurrent. The fuse holder contact pressure is designed to be 5N±1N, with an insertion force of less than 20N and a pull-out force of greater than 2N, ensuring vibration resistance. The relay selection is based on failure mode analysis: its dual-contact structure adopts a redundant design, so that if one set of contacts fails, the other set can still operate normally, achieving a reliability index MTBF of 10. 5 Hour.

[0034] Through precise component selection and installation positioning, seamless compatibility with the aircraft's existing structure was achieved. The rational configuration of 34 fuses ensured the independence of protection for each branch circuit, while the selection of relays guaranteed the accuracy of overload protection. The optimized design of the installation structure avoided modifications to the aircraft's existing wiring, significantly reducing the difficulty and cost of retrofitting and facilitating subsequent maintenance and upgrades.

[0035] Example 2 This embodiment proposes a method for protecting the circuits of a small general-purpose aircraft based on the device described in Embodiment 1, including the following steps: Dynamic parameter acquisition steps: The instantaneous values ​​and rate of change of current in each branch are acquired in real time through the connectors inside the fuse box; Intelligent judgment steps: Identify the fault type by analyzing the current-time characteristic curve; Graded protection steps: The three-level protection mechanism is activated according to the severity of the fault.

[0036] For dynamic parameter acquisition, the ADS8568 ADC chip was selected, with an integral nonlinearity error of ±2 LSB and a differential nonlinearity error of ±0.5 LSB. The sampling clock was provided by a temperature-compensated crystal oscillator with a frequency stability of ±10 ppm. The analog front-end design included: a ±5V clamping circuit (response time 10 ns), an RC filter (R=100Ω, C=100nF), and an OPA2188 operational amplifier with a gain-bandwidth product of 10 MHz.

[0037] The sliding window filtering algorithm is implemented using a circular buffer, with a window length corresponding to a 20ms time width. The algorithm includes outlier removal functionality, automatically marking a fault when three consecutive sampled values ​​exceed the 3σ range.

[0038] In the intelligent judgment algorithm, the first layer of judgment uses a digital comparator with a threshold set to 2.5A (adjustable by software) and a comparison period of 100μs. The second layer calculates dI / dt using the five-point differential method: di / dt=[i(n)-i(n-4)] / (4T), where T is the sampling period of 1ms. A confirmation mechanism is added for short-circuit judgment; the action is triggered only if di / dt≥100A / s is satisfied at 5 consecutive sampling points.

[0039] Third layer I 2 The calculation of t uses the trapezoidal integration method: I 2 t=Σ[(i n 2 +i n₊1 2 [(2)×Δt], the integral time constant is set according to the actual thermal characteristic curve of the fuse, and there are two characteristics to choose from: fast and slow.

[0040] By establishing a multi-level monitoring and protection mechanism, intelligent identification and graded handling of circuit faults are achieved. Dynamic parameter acquisition ensures real-time performance, intelligent judgment algorithms improve the accuracy of fault identification, and graded protection strategies guarantee the rationality of actions. This systematic approach effectively avoids protection blind spots and significantly improves the safety and reliability of aircraft electrical systems.

[0041] The intelligent judgment process also includes an adaptive learning mechanism: analyzing historical operating data through machine learning algorithms to establish a model of equipment load characteristics; automatically correcting protection thresholds based on ambient temperature; and dynamically adjusting protection characteristic curves based on the degree of equipment aging.

[0042] The aforementioned adaptive learning mechanism is implemented through an embedded machine learning algorithm. The system deploys a lightweight neural network model in the MCU. This model adopts a three-layer perceptron structure. The input layer contains 34 neurons corresponding to the current characteristics of each branch, the hidden layer has 16 neurons using the ReLU activation function, and the output layer provides the load characteristic identification results. Model training adopts an online learning method, updating the weight parameters every flight hour, and historical data is continuously retained for the most recent 1000 hours of operation.

[0043] The load characteristic model is established by extracting the time-domain characteristics of the current in each branch, including 12 characteristic parameters such as mean, variance, peak factor, and waveform factor. The model establishment process first collects 72 hours of continuous data under normal operating conditions, and then establishes a baseline feature space after dimensionality reduction through principal component analysis. During real-time operation, Mahalanobis distance is used to calculate the deviation between the current feature space and the baseline space; when the deviation exceeds a threshold, a model update is triggered.

[0044] The system continuously monitors the current waveforms of each branch to automatically learn the power consumption patterns of different devices. When a new load characteristic pattern is detected, the model will autonomously adjust the protection parameter settings. For example, for periodically changing loads, the system will identify the period of change and adjust the sensitivity of the protection algorithm accordingly to avoid false trips caused by normal load fluctuations. This adaptive capability enables the protection system to automatically maintain optimal protection performance as equipment ages, seasons change, and other factors occur.

[0045] By introducing an adaptive learning mechanism, the protection system gains the ability to continuously optimize. The application of machine learning algorithms enables the system to autonomously adapt to changes in load characteristics, and the dynamic adjustment of model parameters ensures the accuracy of protection parameters. This intelligent learning capability allows the protection system to automatically maintain optimal performance as the operating environment changes.

[0046] The graded protection process specifically includes the following collaborative control strategies: Establish a "judgment-then-action" logic coordination mechanism between fuses and relays. When an overcurrent signal is detected, the fault level is first determined by the comparator circuit. If it is a momentary overcurrent (≥30A), the fuse will act within 5ms. If it is a continuous overload (25-30A), the relay will act after 50ms. Set up a protection action priority matrix and dynamically adjust the action sequence according to the fault type and equipment importance. For critical equipment branches, adopt the fuse priority action strategy and for non-critical branches, adopt the relay priority judgment strategy. The design incorporates an intelligent decision-making algorithm for fault isolation and power restoration. By monitoring the voltage recovery characteristics after fault clearance, it automatically determines whether to perform a reclosing operation, thus avoiding repeated power supply to permanently faulty lines.

[0047] The collaborative control strategy implementation scheme: The "judgment-then-action" logic is implemented through a combination of hardware comparators and software judgment. At the hardware level, a high-speed comparator chip (such as the LM139) is used, with multiple sets of voltage comparison thresholds corresponding to different fault levels. At the software level, a fault classification algorithm is run, distinguishing fault types by analyzing current change rate and duration characteristics. The judgment result is transmitted to the actuator via a digital isolator.

[0048] Protection action priority matrix design: The priority matrix is ​​stored in EEPROM in the form of a lookup table, containing action strategies corresponding to 256 operating conditions. Matrix inputs include eight parameters such as fault type code, branch importance level, and system operating status. Outputs are action delay time and actuator selection signal. The matrix content can be modified through the maintenance interface based on actual operating experience.

[0049] When the system detects an abnormal current, it first determines the nature and severity of the fault through multi-parameter fusion. For critical equipment branches, the system adopts a conservative strategy, initiating protection even with minor overloads; for non-critical branches, brief overloads are allowed to differentiate from systemic faults. This differentiated protection strategy ensures priority protection for important equipment while improving the system's power supply reliability. Reclosing decisions after fault clearance are based on voltage recovery characteristics and insulation resistance measurements, ensuring that automatic power restoration is only permitted for truly eliminated faults.

[0050] Through innovative design of a collaborative control strategy, optimized coordination among protective components is achieved. The "judgment first, action later" logic ensures the accuracy of protection actions, the priority matrix setting improves the protection level of critical equipment, and the fault isolation mechanism minimizes the scope of power outages. This intelligent collaborative control significantly enhances the overall protection performance of the system.

[0051] The system self-test and diagnostic steps specifically include: The power-on self-test program automatically performs a full-circuit impedance test before the aircraft is powered on. It detects the connectivity of each branch by injecting a 1mA test current, and scans each of the 34 fuse paths one by one, recording the reference resistance value of each path. The online monitoring system collects fuse temperature rise data in real time, predicts fuse aging status through temperature-current relationship model, and automatically issues an early warning signal when the fuse base temperature rises abnormally (exceeding 50°C of ambient temperature). The fault recording device records the electrical parameter waveforms from 200ms before the protection action to 500ms after the action at a sampling rate of 10kHz, and stores complete data of the most recent 10 faults, including the current phase and amplitude change trajectory of each branch and the relay action sequence.

[0052] Specifically, the power-on self-test (POST) procedure first initializes all peripheral devices, then executes the following sequentially: power quality test (ripple, stability), memory verification (CRC32 checksum), and analog channel benchmark test (zero drift, gain error). Insulation testing uses a ramp voltage method, gradually increasing from 0V to 500VDC while monitoring the leakage current curve. Loop impedance testing employs a four-wire measurement method using a 1kHz AC signal to eliminate the influence of lead resistance.

[0053] The online monitoring system employs 34 digital temperature sensors distributed across the fuse holder, collecting data every 10 seconds and transmitting it to the main controller via a CAN bus. The system establishes a fuse temperature rise model, considering multiple factors such as ambient temperature, load current, and heat dissipation conditions to achieve real-time prediction of the thermal state. When an abnormal temperature rise is detected, the system automatically calculates the remaining safe operating time and issues an early warning.

[0054] The self-test system ensures the device is in good condition through a comprehensive power-on self-test, while online monitoring provides real-time operational status assessment. The fault recording function meticulously records changes in electrical parameters before and after protection actions, providing comprehensive data support for fault analysis. This integrated "prevention-monitoring-recording" design gives the system excellent maintainability and fault traceability.

[0055] A comprehensive status monitoring system has been established through robust self-diagnostic capabilities. Power-on self-tests ensure the initial reliability of the device, online monitoring provides real-time status assessment, and fault recording provides complete data support for subsequent analysis. This preventative maintenance mechanism significantly improves the system's maintainability and operational reliability.

[0056] Early warning and maintenance procedures are implemented in the following ways: Predicting remaining life based on the cumulative thermal effect model of fuses, and establishing I 2 The t-accumulation algorithm calculates the heat accumulation value of each fuse in real time and issues a replacement warning when it reaches 80% of the rated value. The maintenance recommendation system automatically generates optimization solutions based on historical fault statistics. For frequently activated branches, it recommends upgrading the fuse capacity or checking the load equipment, and also provides a priority list of spare parts for replacement. The remote diagnostic interface supports the RS-422 avionics bus protocol and can output a complete device operating status frame, including real-time current of each branch, fuse status words, relay operation count statistics, and fault code description table.

[0057] The life prediction algorithm based on cumulative damage theory calculates the thermal accumulation effect of each fuse in real time. The algorithm considers three main factors: current magnitude, duration, and ambient temperature, establishing a multidimensional damage accumulation model. Model parameters are obtained through accelerated life testing, including life characteristic data at 34 different current levels. Prediction results are displayed as a percentage, triggering an early warning when the remaining life is below 20%.

[0058] The maintenance decision-making system uses association rule mining technology to discover fault patterns based on fault statistical analysis and equipment operation data. The system establishes a fault knowledge base, including historical fault records, handling methods, and effectiveness evaluations. When a specific fault pattern is detected, the system automatically matches similar cases and provides handling suggestions. The maintenance plan considers multiple constraints such as equipment importance, fault risk, and maintenance resources, and generates a scientifically sound maintenance plan through optimization algorithms.

[0059] This system intelligently analyzes operational data to shift from post-failure maintenance to predictive maintenance. The lifespan prediction model accurately estimates the remaining lifespan of equipment, enabling planned maintenance activities. The maintenance recommendation system provides professional decision support, helping maintenance personnel quickly locate problems and take effective measures. The remote diagnostic interface allows ground maintenance personnel to monitor the equipment status in real time, significantly improving maintenance efficiency.

[0060] Advanced predictive maintenance strategies have enabled an intelligent transformation of equipment management. Lifespan prediction models provide a scientific basis for maintenance planning, maintenance recommendation systems optimize resource allocation, and remote diagnostic interfaces improve maintenance efficiency. This comprehensive maintenance support system significantly reduces total lifecycle maintenance costs.

[0061] The specific reliability enhancement measures include: A dual-redundant acquisition scheme is adopted, with key signals being sampled synchronously through independent ADC channels. A difference comparison threshold (±2%) is set, and the system automatically switches to the backup channel when the data deviation between the two channels exceeds the limit. The watchdog monitoring mechanism employs a three-level protection system: the software watchdog refreshes every 100ms, the hardware watchdog is set with a 1.5s timeout threshold, and the power monitoring chip monitors the power supply quality in real time (fluctuation range ±5%). The power failure self-recovery function saves the system state through non-volatile memory. When power is lost, the current parameters are automatically stored, and after power is restored, the status verification and recovery algorithm achieves seamless resume, ensuring the continuity of protection actions.

[0062] Key signal acquisition employs two completely independent systems, including redundancy across the entire signal chain such as sensors, signal conditioning, and ADC conversion. The dual-path systems utilize different design principles; for example, one path uses a Hall current sensor, while the other employs a shunt to avoid common-cause failures. Data consistency verification employs a combination of algorithms, including difference comparison, trend analysis, and correlation testing, ensuring a false positive rate of less than 10⁻⁻⁶. 6 .

[0063] Watchdog monitoring system: A three-tiered watchdog system monitors the system status at different levels. The hardware watchdog uses a dedicated chip to monitor power quality and clock stability; the software watchdog monitors the program execution flow through task scheduling; and the application-layer watchdog focuses on monitoring the timeliness of the protection algorithm's execution. A linkage mechanism is established between the watchdog levels, allowing for timely escalation and handling when one level fails.

[0064] Redundant design ensures that the failure of a single component will not lead to the loss of system functionality, and differentiated design concepts avoid common-mode failures. A watchdog system provides comprehensive status monitoring, promptly detecting and handling anomalies. Power-off self-recovery functionality ensures that the system can quickly resume normal operation after an unexpected power outage, and all critical data is intact. These measures collectively form the foundation of the system's high reliability.

[0065] Multiple reliability safeguards have been implemented to establish a high-reliability foundation for the system. Redundancy design ensures that a single point of failure does not affect system functionality, watchdog monitoring provides comprehensive status protection, and power-off self-recovery guarantees system continuity. These measures together constitute the system's reliability assurance framework.

[0066] Airworthiness compliance is guaranteed through the following methods: Each flight cycle automatically generates a protection system operation report that meets FAA format requirements, including statistics on the number of protection actions, response time analysis (requirement <100ms), fault type distribution, and device availability calculation (target value ≥99.9%). The verification test uses the step load mutation method to simulate various fault scenarios and verify the accuracy of the protection action. The requirements are that the short-circuit protection response error is <5% and the overload protection delay error is <10%. The airworthiness compliance documentation system includes all test items required by CCAR-23, especially the protection performance verification data under high-altitude low-pressure environment (simulating an altitude of 8,000 meters).

[0067] Airworthiness compliance verification system: The verification system is built on a complete documentation foundation, including four levels: requirements specifications, design documents, test cases, and verification reports. Each protection function has a corresponding verification plan, clearly defining verification methods, pass standards, and testing environment requirements. Verification activities cover three scenarios: normal operating conditions, boundary conditions, and fault conditions, ensuring the system operates reliably under all circumstances.

[0068] Testing and Verification Methodology: A three-level verification strategy is employed: Model-in-the-Loop (MIL), Software-in-the-Loop (SIL), and Hardware-in-the-Loop (HIL). The MIL phase verifies the correctness of the algorithm logic, the SIL phase verifies the accuracy of the code implementation, and the HIL phase verifies the actual performance of the system. Test case design is based on equivalence class partitioning and boundary value analysis principles to ensure test coverage greater than 95%.

[0069] A systematic verification methodology ensures that the protection device fully complies with airworthiness regulations. Operational reports for each flight cycle provide objective evidence of the device's performance, while verification reports demonstrate its performance under various operating conditions. This comprehensive compliance verification system not only meets current airworthiness requirements but also allows for upgrades to accommodate future regulatory changes.

[0070] A comprehensive quality assurance system was established through a systematic verification methodology. Conformity verification ensured the airworthiness and compliance of the device, testing verification guaranteed performance reliability, and the documentation system provided support for continuous compliance. This standardized verification process laid a solid foundation for the long-term safe operation of the product.

[0071] System optimization features include: An adaptive parameter optimization algorithm based on operational data automatically adjusts protection curve parameters by analyzing historical fault characteristics and uses the least squares method to fit the optimal protection characteristic equation. The remote upgrade system supports differential incremental updates, verifies firmware integrity through digital signatures, and maintains basic protection functions uninterrupted during the upgrade process. The data statistics and analysis engine can generate multi-dimensional operation reports, including branch load rate statistics, protection action success rate analysis, and device reliability trend prediction, and supports output in multiple formats such as PDF / Excel.

[0072] System optimization functionality implementation: The parameter optimization algorithm employs a model-based optimization strategy. First, a mathematical model of the system is established, including multiple sub-models such as electrical, thermal, and mechanical characteristics. The optimization objective comprehensively considers multiple indicators such as protection speed, accuracy, and reliability, and a Pareto optimal solution is sought through a multi-objective optimization algorithm. The optimization process adopts a gradual strategy, adjusting only a few parameters at a time to ensure system stability.

[0073] Remote upgrade security mechanism: The upgrade system employs a two-way authentication mechanism, establishing a secure communication link between ground equipment and airborne devices. The upgrade package includes security elements such as version information, digital signature, and checksum. The upgrade process consists of three phases: download, verification, and activation, each with a corresponding rollback mechanism. During the upgrade, the system enters a secure mode to ensure that basic protection functions are unaffected.

[0074] System optimization features enable protection devices to continuously improve performance based on actual operating conditions. A remote upgrade mechanism provides a convenient way to expand functionality and fix problems, while ensuring the safety and reliability of the upgrade process. Data statistical analysis functions provide decision support for system optimization, forming a complete closed loop of continuous improvement. This design gives the system excellent scalability and adaptability.

[0075] Intelligent optimization features enable the system to continuously evolve. Parameter optimization algorithms ensure continuous performance improvement, remote upgrade mechanisms provide a convenient way to expand functionality, and data analysis functions support optimization decisions.

[0076] The above-described embodiments are detailed and specific, illustrating preferred embodiments of the present invention. They are only used to illustrate the technical ideas and features of the present invention, with the aim of enabling those skilled in the art to understand the content of the present invention and implement it accordingly. However, they are not limited to the present invention, and the patent scope of the present invention cannot be limited by this embodiment alone. That is, any equivalent changes or modifications made to the spirit disclosed in the present invention, without departing from the structure of the present invention, such as local improvements within the system and modifications or transformations between subsystems, are still within the patent scope of the present invention.

Claims

1. A short-circuit and overload protection device for a small general-purpose aircraft circuit, characterized in that, The device includes a fuse box, which integrates a fuse, a fuse holder, a relay, and a connector. The fuse is mounted via the fuse holder and is used for short-circuit protection. The relay is used to monitor current overload and control circuit connection and disconnection. The connector is configured with 2 inputs and 1 output, supports 28.5VDC voltage, input current less than 25A, and output current of 2A.

2. The short-circuit and overload protection device for a small general-purpose aircraft according to claim 1, characterized in that, The fuses are 34 type 520 2A fuses, and the fuse holders are 34 type F0321 520 holders; the relays are type JKM-S2 / 116; the fuse box is fixed on the aircraft frame 1.

3. A method for protecting the circuits of a small general-purpose aircraft based on the device described in claim 2, characterized in that, Includes the following steps: Dynamic parameter acquisition steps: The instantaneous values ​​and rate of change of current in each branch are acquired in real time through the connectors inside the fuse box; Intelligent judgment steps: Identify the fault type by analyzing the current-time characteristic curve; Graded protection steps: The three-level protection mechanism is activated according to the severity of the fault.

4. The circuit protection method for small general-purpose aircraft according to claim 3, characterized in that, The intelligent judgment step also includes an adaptive learning mechanism: analyzing historical operating data through machine learning algorithms to establish a device load characteristic model; automatically correcting the protection threshold based on ambient temperature; and dynamically adjusting the protection characteristic curve based on the degree of device aging.

5. The circuit protection method for small general-purpose aircraft according to claim 3, characterized in that, The hierarchical protection steps specifically include the following collaborative control strategies: Establish a logic coordination mechanism between fuses and relays that determines the fault level before it is activated. When an overcurrent signal is detected, the comparator circuit first determines the fault level. If it is a momentary overcurrent, the fuse will activate within 5ms. If it is a continuous overload, the relay will activate after 50ms. Set up a protection action priority matrix and dynamically adjust the action sequence according to the fault type and equipment importance. For critical equipment branches, adopt the fuse priority action strategy and for non-critical branches, adopt the relay priority judgment strategy. The design incorporates an intelligent decision-making algorithm for fault isolation and power restoration. By monitoring the voltage recovery characteristics after fault clearance, it automatically determines whether to perform a reclosing operation, thus avoiding repeated power supply to permanently faulty lines.

6. The circuit protection method for small general-purpose aircraft according to claim 3, characterized in that, It also includes system self-test and diagnostic steps, which specifically include: The power-on self-test program automatically performs a full-circuit impedance test before the aircraft is powered on. It detects the connectivity of each branch by injecting a 1mA test current, and scans each of the 34 fuse paths one by one, recording the reference resistance value of each path. The online monitoring system collects fuse temperature rise data in real time, predicts fuse aging status through temperature-current relationship model, and automatically issues an early warning signal when abnormal temperature rise of fuse base is detected. The fault recording device records the electrical parameter waveforms from 200ms before the protection action to 500ms after the action at a sampling rate of 10kHz, and stores complete data of the most recent 10 faults, including the current phase and amplitude change trajectory of each branch and the relay action sequence.

7. The circuit protection method for small general-purpose aircraft according to claim 3, characterized in that, It also includes early warning and maintenance steps, which are implemented in the following ways: Predicting remaining life based on the cumulative thermal effect model of fuses, and establishing I 2 The t-accumulation algorithm calculates the heat accumulation value of each fuse in real time and issues a replacement warning when it reaches 80% of the rated value. The maintenance recommendation system automatically generates optimization solutions based on historical fault statistics. For frequently activated branches, it recommends upgrading the fuse capacity or checking the load equipment, and also provides a priority list of spare parts for replacement. The remote diagnostic interface supports the RS-422 avionics bus protocol and can output a complete device operating status frame, including real-time current of each branch, fuse status words, relay operation count statistics, and fault code description table.

8. The circuit protection method for small general-purpose aircraft according to claim 3, characterized in that, It also includes reliability enhancement measures, which specifically include: A dual-redundant acquisition scheme is adopted, in which key signals are synchronously sampled through independent ADC channels. A difference comparison threshold is set, and the system automatically switches to the backup channel when the data deviation between the two channels exceeds the limit. The watchdog monitoring mechanism employs three levels of protection: the software watchdog refreshes every 100ms, the hardware watchdog is set with a 1.5s timeout threshold, and the power monitoring chip monitors power quality in real time. The power failure self-recovery function saves the system state through non-volatile memory. When power is lost, the current parameters are automatically stored, and after power is restored, the status verification and recovery algorithm achieves seamless resume, ensuring the continuity of protection actions.

9. The circuit protection method for small general-purpose aircraft according to claim 3, characterized in that, The airworthiness compliance guarantee is achieved through the following methods: Each flight cycle automatically generates a protection system operation report that meets FAA format requirements, including statistics on the number of protection actions, response time analysis, fault type distribution, and device availability calculation; The verification test uses the step load mutation method to simulate various fault scenarios and verify the accuracy of the protection action. The requirements are that the short-circuit protection response error is <5% and the overload protection delay error is <10%. The airworthiness compliance documentation system includes all test items required by CCAR-23, especially the protection performance verification data for high-altitude, low-pressure environments.

10. The circuit protection method for small general-purpose aircraft according to claim 3, characterized in that, The system optimization functions include: An adaptive parameter optimization algorithm based on operational data automatically adjusts protection curve parameters by analyzing historical fault characteristics and uses the least squares method to fit the optimal protection characteristic equation. The remote upgrade system supports differential incremental updates, verifies firmware integrity through digital signatures, and maintains basic protection functions uninterrupted during the upgrade process. The data statistics and analysis engine can generate multi-dimensional operation reports, including branch load rate statistics, protection action success rate analysis, and device reliability trend prediction, and supports output in multiple formats.

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