Load test method for power take-off power generation system of special vehicle

Abstract

The invention belongs to the technical field of electrical system testing, and provides a special vehicle power take-off power generation system load testing method which comprises the following steps: S1, connecting a programmable resistance load box and a high-speed data acquisition system with the output end of a power take-off power generation system; s2, the resistive load box is controlled to load the power take-off power generation system in the starting process according to a preset S-shaped function multi-stage loading strategy, wherein the strategy at least comprises a no-load stage, an S-shaped function-based gradient loading stage and a full-load steady-state stage; and S3, in the loading process, a high-speed data acquisition system is utilized to synchronously acquire an instantaneous value sequence of output voltage and current of the power take-off power generation system. According to the technical scheme, deep detection and intelligent evaluation of the performance of the whole starting, loading and stabilizing process of the power take-off power generation system can be achieved.

Description

Technical Field

[0001] This invention belongs to the field of electrical system testing technology, specifically relating to a load testing method for a power take-off (PTO) system of a special vehicle. Background Technology

[0002] The power take-off (PTO) system of special vehicles is a crucial component ensuring the normal operation of various electronic devices, weapon systems, and auxiliary devices within the vehicle. It provides power to onboard communication, command, detection, and weapon systems when the vehicle is parked or at low speeds, and its performance and reliability directly affect the vehicle's combat effectiveness. As the core unit of power take-off, the performance of the PTO system during its startup phase directly impacts the stability and reliability of the entire vehicle's electrical system.

[0003] Currently, the system is commonly tested using a high-power resistive load cell. However, existing testing methods have significant shortcomings: 1. Crude testing methods: Existing methods are mostly simple "no-load to full-load" switching tests or static constant load tests, which can only obtain basic parameters such as voltage and current under steady state. They cannot effectively simulate the dynamic load characteristics of actual electrical equipment, let alone capture the performance of the system during the critical transient phase of startup.

[0004] 2. Superficial data analysis: Test results are usually only used to determine "whether there is output" or "whether the output voltage is within the range". They lack the extraction and analysis of in-depth performance parameters such as waveform quality, dynamic response characteristics, and load-bearing starting capability, and cannot diagnose potential faults such as slow response of the excitation system, deterioration of voltage regulator performance, and slight power deficiency at the engine power take-off end.

[0005] 3. Reliance on human experience: The conclusions are highly dependent on the operator's experience, and judgments are made by observing pointer swings or simple data records. There is a lack of objective and quantitative evaluation basis, which makes it easy to miss or misjudge.

[0006] 4. Lack of predictive maintenance capability: Existing methods cannot predict the degradation trend of system performance through the analysis of transient characteristics, and cannot provide data support for predictive maintenance.

[0007] Therefore, there is an urgent need to develop a load testing process that can deeply mine information from the startup process of a power take-off system and perform quantitative analysis and intelligent diagnosis. Summary of the Invention

[0008] (a) Technical problems to be solved The technical problem this invention aims to solve is that existing testing methods cannot effectively evaluate the dynamic performance of power take-off (PTO) systems.

[0009] (II) Technical Solution To address the aforementioned technical problems, this invention provides a load testing method for a power take-off (PTO) system of a special vehicle, comprising the following steps: S1: Connect the programmable resistor load cell and high-speed data acquisition system to the output terminal of the power take-off system; S2: Control the resistive load box to load the power take-off system during the startup process according to the preset "S-shaped function" multi-stage loading strategy. The strategy includes at least an unloaded stage, a gradual loading stage based on the S-shaped function, and a full-load steady-state stage. S3: During the loading process, the instantaneous value sequence of the output voltage and current of the power take-off system is synchronously acquired using a high-speed data acquisition system; S4: Based on the instantaneous value sequence, calculate the characteristic parameters used to evaluate the dynamic performance of the power take-off system, the characteristic parameters including at least voltage fluctuation rate VDR and voltage recovery time VRT; S5: Compare the calculated characteristic parameters with the preset performance thresholds, and evaluate and diagnose the performance status of the power take-off system based on the comparison results.

[0010] Furthermore, the sigmoid function is: P(t)= Pn / (1+e^(-k*(t-t_c))), Where P(t) is the load power at time t, Pn is the rated load power, k is the slope factor controlling the loading rate, and t_c is the time center point of the loading process.

[0011] Furthermore, the formula for calculating the voltage fluctuation rate VDR is as follows: VDR=[(U0-U_min) / U0]*100% Wherein, U0 is the no-load steady-state voltage, and U_min is the minimum effective value of the voltage during the gradual loading stage.

[0012] Furthermore, the voltage recovery time VRT is defined as the time elapsed from the start of loading until the effective voltage value first enters and remains within the range of ±1% of the full-load steady-state voltage.

[0013] Furthermore, in step S4, the calculated characteristic parameters also include the frequency adjustment rate ΔF and the total harmonic distortion rate THD.

[0014] Furthermore, the formula for calculating the frequency adjustment rate ΔF is as follows: ΔF = [(F0 - F1) / F0] * 100% Where F0 is the no-load steady-state frequency and F1 is the full-load steady-state frequency.

[0015] Furthermore, the total harmonic distortion (THD) is calculated by performing a Fast Fourier Transform (FFT) on the voltage waveform during the steady-state phase of the full load.

[0016] Furthermore, the performance threshold mentioned in step S5 is determined by statistical analysis of test data from a large number of normal power take-off and generation systems. The fault diagnosis is as follows: if VDR and VRT exceed the threshold, it is diagnosed as a voltage regulation system fault; if ΔF exceeds the threshold, it is diagnosed as a fault in the prime mover power take-off or speed governor; if THD exceeds the threshold, it is diagnosed as a fault in the generator armature or excitation winding.

[0017] (III) Beneficial Effects Compared with existing technologies, the present invention has the following advantages: it can not only complete traditional steady-state tests, but more importantly, by designing a multi-stage gradual loading process and combining it with dynamic parameter acquisition and feature analysis algorithms, it can achieve in-depth detection and intelligent evaluation of the performance of the power take-off system throughout the entire process of startup, loading, and stabilization. Detailed Implementation

[0018] To make the objectives, contents, and advantages of the present invention clearer, the specific embodiments of the present invention will be described in further detail below with reference to examples.

[0019] This invention provides a load detection method for a power take-off (PTO) system in a special vehicle. The core of this method lies in controlling a resistive load box to load the PTO system during startup according to a preset multi-stage loading strategy based on an "S-curve." Simultaneously, electrical parameters are collected at high speed, and key performance indicators are extracted using a series of feature algorithms. Finally, comprehensive performance evaluation and fault diagnosis are performed based on these indicators. The method specifically includes the following steps: 1. Test preparation and system connection • Inspect the appearance and performance of test equipment such as resistor load boxes, data acquisition devices, and connecting harnesses to ensure they are working properly; • Connect the resistor load box to the output terminal of the special vehicle's power take-off system using a dedicated wiring harness, ensuring a secure connection and good insulation; • Connect the data acquisition equipment to the signal output terminals of the sensors and resistive load boxes of the power generation system to ensure smooth data acquisition channels.

[0020] 2. Design and execute a multi-stage dynamic loading test process. Start the vehicle engine to rated speed to initiate the power take-off (PTO) system. Then, control the resistor load bank via the host computer to execute the following loading procedure: • Initial no-load phase (T0-T1): The load is kept at no load for a duration of Δt1, which is used to record the system no-load steady-state voltage U0 and frequency F0.

[0021] • S-curve gradual loading stage (T1-T2): Control the power module of the load box so that its load power P increases from 0% to 100% rated load (Pn) according to the S-curve function shown in equation (1).

[0022] P(t)= Pn / (1+e^(-k*(t-t_c))) (Formula 1) Where k is the curve slope factor, controlling the loading rate; t_c is the time center point of the loading process. This design simulates the smooth process of gradual load connection in real-world applications, avoiding the huge impact of step loading on the power generation system and facilitating the complete capture of the system's dynamic adjustment process.

[0023] • Full-load steady-state phase (T2-T3): Maintain 100% rated load for a duration of Δt2, used to record the steady-state voltage U1, frequency F1, and output current I1 of the system under full load.

[0024] 3. High-speed synchronous data acquisition • Throughout the entire testing process (step 2), the instantaneous value sequence of the following parameters is synchronously recorded using a high-speed data acquisition system: -Instantaneous voltage values ​​(Ua, Ub, Uc) -Instantaneous current values ​​(Ia, Ib, Ic) 4. Dynamic Feature Parameter Extraction and Calculation The following algorithm is applied to the collected high-speed data to extract key performance characteristic parameters: • Voltage fluctuation rate (VDR): During the gradual loading phase (T1-T2), find the lowest point U_min of the effective voltage value (calculated per cycle).

[0025] VDR=[(U0-U_min) / U0]*100%(Formula 2) VDR directly reflects the system's ability to maintain voltage under sudden load.

[0026] • Voltage recovery time (VRT): Defined as the time elapsed from the moment the load begins to be applied (T1) until the effective voltage value first enters and remains within the steady-state range of U1±1%.

[0027] VRT reflects the dynamic response speed of a voltage regulation system.

[0028] • Frequency regulation rate (ΔF): ΔF=[(F0-F1) / F0]*100% (Equation 3) This parameter reflects the speed regulation performance of the prime mover (power take-off end).

[0029] • Total Harmonic Distortion (THD) Calculation: Perform a Fast Fourier Transform (FFT) on the voltage waveform during the steady-state phase (T2-T3) under full load, and calculate its THD using the following formula: THD= [sqrt(∑(U_h^2) / U_1)]*100%(Formula 4) Where U_h is the effective value of the h-th harmonic voltage (h=2,3,4,...), and U_1 is the effective value of the fundamental voltage.

[0030] THD reflects the output waveform quality of a power generation system.

[0031] 5. Performance evaluation and fault diagnosis • Organize the collected functional parameters under different load levels and remove abnormal data; • Compare the characteristic parameters (VDR, VRT, ΔF, THD) calculated in step 4 with preset performance thresholds. The performance thresholds are derived statistically from test data of a large number of normal prototypes.

[0032] If all parameters are better than the threshold, the system is judged to have "excellent performance".

[0033] If a single parameter exceeds the threshold, preliminary fault orientation can be performed: Excessive VDR and excessively long VRT may indicate an AVR (Automatic Voltage Regulator) response failure or a problem with the excitation system.

[0034] ΔF too large: may indicate insufficient power at the engine's power take-off end or a speed governor malfunction.

[0035] Excessive THD may indicate a fault in the generator windings or rectifier.

[0036] 6. Test completed • After all load level tests are completed, shut down the power take-off system, data acquisition equipment, and resistor load box; • Disconnect the connecting wire harness, organize the testing equipment, and complete the test report. Example 1

[0037] This example uses the power take-off (PTO) system of a certain type of electronic warfare vehicle as the test object. Its rated power is 30kW and rated voltage is 220V. The load test is carried out using the process method of this invention. The specific steps are as follows: 1. Test preparation • Inspect the resistive load box, data acquisition equipment (including voltage sensors, current sensors, speed sensors and data loggers) and dedicated connection harnesses to confirm that each device is undamaged and functions normally. • Use a dedicated connecting harness to connect the input terminal of the resistor load box to the output terminal of the power take-off system. After connection, wrap the interface with insulating tape to ensure good insulation and a secure connection. • Connect the voltage sensor in parallel to the output of the power take-off system, connect the current sensor in series in the circuit, and install the speed sensor on the engine output shaft of the power take-off system. Connect the signal output terminals of each sensor to the data logger, turn on the data logger, and check that the signals of each acquisition channel are normal.

[0038] 2. Load parameter settings • Determine the load levels to be tested as no load, 25% of rated load (7.5kW), 50% of rated load (15kW), 75% of rated load (22.5kW), and 100% of rated load (30kW). • Loading settings: Set the S-curve loading parameters, k=0.5, so that the load smoothly increases from 0 to 30kW in 5 seconds and is held for 10 seconds.

[0039] 3. Start the power take-off system and collect data. • First, perform no-load testing, start the power take-off system, and simultaneously start the data acquisition equipment. The data logger collects parameters such as output voltage, output current, start-up time, power factor, and engine speed in real time at a sampling frequency of 50Hz. • When the output voltage of the power take-off system stabilizes within the range of 220V±5% for 30 seconds, the system is considered to have started up completely. Data acquisition is stopped, and all acquired data under no-load conditions is recorded. The start-up time is 5 seconds, and the output voltage fluctuation range is 218-222V.

[0040] 4. Multi-load level detection • After completing the no-load test, shut down the power take-off system and wait for it to stop completely. Then, adjust the resistor load box to 6.45Ω, which corresponds to 25% of the rated load. • Restart the power take-off system and data acquisition equipment to collect the startup parameters under this load level. After startup is complete, stop the acquisition and record the data. The startup time is 6.5s and the output current is stable at 28-30A. • Following the same method described above, complete the tests at 50%, 75%, and 100% rated load levels, and record the start-up time, output voltage, output current, and other parameters corresponding to each load level.

[0041] 5. Data Processing and Analysis • The collected data for each load level were processed, and outliers caused by instantaneous interference (such as a sudden voltage change to 0 at a certain moment) were removed. The no-load voltage U0 was measured to be 222V, the full-load voltage U1 was measured to be 220V, and the minimum voltage U_min was calculated to be 218V. According to equation (2): VDR = [(222 - 218) / 222]*100%≈1.8%. According to waveform analysis, VRT was measured to be 1.2s; the voltage regulation rate [(222 - 220) / 222]*100%≈0.9% (steady-state index) was calculated; FFT analysis showed that THD < 2%.

[0042] • Analysis shows that as the load level increases, the start-up time of the power take-off system gradually increases, the output current gradually increases, and the output voltage fluctuation range slightly expands, but all are within the allowable range (215-225V). Comparing the results with the thresholds (VDR threshold <15%, VRT threshold <1.5s, THD threshold <5%), all parameters in this example are within the excellent range. The engine speed gradually increases from idle speed to rated speed (1500r / min) during the start-up phase, which meets the start-up performance requirements of this type of special vehicle power take-off system.

[0043] 6. Testing completed • After all load level tests are completed, shut down the power take-off system, data acquisition equipment, and resistor load box in sequence.

[0044] • Disconnect the connecting harness, clean and maintain the test equipment, and generate a test report based on the test data. The report includes the startup parameters and performance evaluation conclusions for each load level.

[0045] The testing process in this embodiment verifies the feasibility and effectiveness of the process method of the present invention, which can accurately and efficiently complete the testing of relevant functional parameters of the power take-off system of special vehicles during startup.

[0046] The beneficial effects of this embodiment are as follows: 1. Improved detection accuracy: This invention uses a resistive load box as the testing equipment. Through S-shaped gradual loading and high-speed acquisition, the load level can be precisely adjusted, making the test load closer to the actual working conditions. For the first time, it realizes the refined measurement of the dynamic process of power take-off system startup, and obtains much richer information than steady-state testing, effectively improving the accuracy of functional parameter detection during power take-off system startup.

[0047] 2. Quantitative Evaluation: We invented a feature parameter extraction algorithm based on VDR, VRT, etc. Through standardized process steps, we clarified each link from test preparation to data processing. The operation process is clear, reducing the difficulty of operation. We quantified the dynamic performance of the system into specific indicators, realizing a leap from "qualitative judgment" to "quantitative analysis".

[0048] 3. Intelligent Diagnosis: By establishing a mapping relationship between characteristic parameters and system status, preliminary automatic diagnosis of potential faults is achieved without relying on complex on-site vehicle testing environments, reducing the investment in site, equipment and manpower costs, lowering testing costs, and reducing reliance on personnel experience, thereby improving the accuracy and efficiency of testing.

[0049] 4. Predictive maintenance: By periodically detecting and recording the drift trends of performance indicators such as VDR and VRT, the health status of the system can be predicted, providing a data foundation for implementing predictive maintenance.

[0050] 5. Technological Innovation: The “S-curve loading” process itself is an innovation. It avoids damage to the equipment caused by impact loads and provides the best test conditions for analyzing dynamic response.

[0051] The above description is only a preferred embodiment of the present invention. It should be noted that for those skilled in the art, several improvements and modifications can be made without departing from the technical principles of the present invention, and these improvements and modifications should also be considered within the scope of protection of the present invention.

Claims

1. A method of load testing a special vehicle power take-off electrical generation system, the method comprising: The method comprises the following steps: S1: connecting a programmable resistance load box and a high-speed data acquisition system to the output end of the power-taken generating system; S2: controlling the resistance load box to load the power-taken generating system in the starting process according to a preset "S-shaped function" multi-stage loading strategy, which at least comprises an idle load stage, a gradual loading stage based on an S-shaped function, and a full load steady stage; S3: synchronously collecting instantaneous value sequences of output voltage and current of the power-taken generating system by using the high-speed data acquisition system during the loading process; S4: calculating characteristic parameters for evaluating dynamic performance of the power-taken generating system based on the instantaneous value sequences, which at least comprise a voltage fluctuation rate VDR and a voltage recovery time VRT; S5: comparing the calculated characteristic parameters with preset performance threshold values, and evaluating and diagnosing the performance state of the power-taken generating system according to the comparison result.

2. The method of claim 1, wherein, The S-shaped function is: P(t)= Pn / (1+e^(-k*(t-t_c))), wherein P(t) is the load power at time t, Pn is the rated load power, k is a slope factor for controlling the loading rate, and t_c is a time center point of the loading process.

3. The method of claim 2, wherein, The calculation formula of the voltage fluctuation rate VDR is: VDR=[(U0-U_min) / U0]*100% wherein U0 is the idle load steady voltage, and U_min is the minimum value of the effective value of the voltage in the gradual loading stage.

4. The method of claim 3, wherein, The voltage recovery time VRT is defined as the time from the starting time of the loading to the time when the effective value of the voltage first enters and continuously stays in the range of the full load steady voltage ±1%.

5. The method of claim 4, wherein, In step S4, the calculated characteristic parameters further comprise a frequency adjustment rate ΔF and a total harmonic distortion rate THD.

6. The method of claim 5, wherein, The calculation formula of the frequency adjustment rate ΔF is: ΔF=[(F0-F1) / F0]*100% wherein F0 is the idle load steady frequency, and F1 is the full load steady frequency.

7. The load testing method for a special vehicle power take-off generation system as described in claim 6, characterized in that, The total harmonic distortion rate THD is calculated by performing fast Fourier transform (FFT) on the voltage waveform in the full load steady stage.

8. The method of claim 7, wherein the load test is performed on the special vehicle PTO system. The performance threshold values in step S5 are determined by statistical analysis on a large amount of test data of normal power-taken generating systems, and the fault diagnosis is as follows: if VDR and VRT exceed the threshold values, it is diagnosed as a voltage regulation system fault; if ΔF exceeds the threshold value, it is diagnosed as a fault of the power-taken end of the prime mover or the speed regulator; and if THD exceeds the threshold value, it is diagnosed as a fault of the generator armature or the field winding.