A BDU automated testing system and method

Abstract

The present application belongs to the technical field of new energy automobile parts testing, and particularly relates to a BDU automatic testing system and method; the present application acquires the background noise signals at the two ends of the BDU to be tested, obtains the optimal injection frequency after frequency spectrum analysis, and obtains the optimal detection frequency in this way to overcome the interference of the environmental background noise on the measurement results in the traditional scheme, so as to more accurately calculate and obtain the original resistance value of the BDU contact; and the forward and reverse current path switching is realized by controlling the relay switching matrix, the average value of the forward and reverse resistances is calculated, and the potential error is reduced; the thermal drift compensation and data correction are carried out based on the segmented time domain thermal model, the heating resistance is corrected, and the influence caused by the temperature rise is eliminated.

Description

Technical Field

[0001] This invention belongs to the field of testing technology for new energy vehicle components, and in particular relates to an automated BDU testing system and method. Background Technology

[0002] The Battery Disconnect Unit (BDU) is a crucial component in the battery system of new energy vehicles, responsible for battery safety protection and energy distribution. The main components of a BDU include a main positive relay, main negative relay, pre-charge relay, and current sensors. The reliability of the BDU directly determines the electrical safety of the entire vehicle, therefore, rigorous testing of the BDU is essential.

[0003] However, in existing BDU testing, on the one hand, traditional test benches cannot simulate the dynamic engagement / disengagement characteristics under high-voltage loads when performing static continuity and insulation withstand voltage tests, resulting in low test coverage. Furthermore, relays in BDUs often generate arcs when disconnected under load, causing contact erosion. Existing testing methods cannot quantify the arc energy, making it difficult to predict the remaining service life of the BDU. Moreover, in high-current testing environments, electromagnetic interference is severe, leading to large fluctuations in contact resistance measurements and a high rate of misjudgment. High current also causes the relay contacts to heat up due to Joule heating, resulting in physical resistance drift and easily causing false "fault" misjudgments. On the other hand, most existing AC internal resistance tests use a fixed frequency, such as 1kHz. However, in the complex electromagnetic environment of a factory, if 1kHz happens to coincide with the inverter switching frequency or mechanical vibration frequency, the measurement results will be severely distorted.

[0004] Therefore, it is crucial to address the issues identified in the BDU test to improve overall vehicle safety. Summary of the Invention

[0005] Based on the above background, this invention proposes an automated testing system and method for BDU, which aims to obtain the optimal test frequency through spectrum scanning and signal-to-noise ratio optimization, and to perform thermal drift correction by establishing a thermal-electric coupling model of relay contacts.

[0006] This invention proposes an automated BDU testing system, characterized by comprising: a main control unit, a signal generator module, a signal acquisition module, a relay switching matrix, and a measurement carrier. The signal generator module, signal acquisition module, relay switching matrix, and measurement carrier are all electrically connected to the main control unit. The main control unit controls the coordinated operation of the signal generator module, signal acquisition module, relay switching matrix, and measurement carrier to achieve automated BDU testing. The automated BDU testing method includes the following steps: Step S1: The main control unit controls the signal acquisition module to acquire the background noise signals at both ends of the BDU under test. And controlled by the main control unit Perform spectral analysis to obtain the optimal injection frequency ; Step S2, the main control unit controls the signal generator module to inject at the optimal frequency. A sinusoidal excitation current is generated and applied to the test circuit consisting of the measuring carrier and the BDU under test. At the same time, the control signal acquisition module acquires the response voltage across the BDU under test and calculates the measured resistance value based on the response voltage. Step S3: The main control unit controls the relay switching matrix to switch between forward and reverse current paths and collects forward and reverse resistance values. Eliminate contact potential interference and complete preliminary consistency determination; Step S4: The main control unit estimates the contact temperature rise in segments according to the test timing sequence, and performs thermal drift compensation and data correction based on the segmented time-domain thermal model. Corrected to forward standard resistance at standard temperature and reverse standard resistor ; Step S5, the main control unit uses the forward standard resistor and reverse standard resistor Calculate the deviation rate and compare it with a preset threshold to obtain the BDU contact performance.

[0007] Compared with the prior art, the present invention has the following advantages: 1. The present invention first collects the background noise signals at both ends of the BDU under test, performs spectrum analysis to obtain the optimal injection frequency, and obtains the optimal detection frequency in this way to overcome the interference of environmental background noise on the measurement results in the traditional scheme, thereby calculating the original resistance value of the BDU contact more accurately.

[0008] 2. This invention achieves forward and reverse current path switching by controlling the relay switching matrix, and reduces the error caused by potential error by calculating the average value of the forward and reverse resistance; the traditional detection method uses a single current direction, which often leads to potential error due to the small temperature difference of the contacts.

[0009] 3. This invention uses a piecewise time-domain thermal model to perform thermal drift compensation and data correction, corrects the resistance of the generated heat, and eliminates the effects of temperature rise. Attached Figure Description

[0010] To more clearly illustrate the technical solutions in the embodiments of the present invention, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0011] Figure 1 This is a flowchart of an automated BDU testing method proposed in this invention; Figure 2 This is a schematic diagram of the working principle of the relay switching matrix used in this invention; Figure 3 This is a framework diagram of an automated BDU testing system proposed in this invention; Figure 4 This presents some experimental results of an automated BDU testing method proposed in this invention. Detailed Implementation

[0012] In the following description, specific details such as particular system architectures and techniques are set forth for illustrative purposes and not for limitation, in order to provide a thorough understanding of the embodiments of the invention. However, those skilled in the art will understand that the invention can be implemented in other embodiments without these specific details. In other instances, detailed descriptions of well-known systems, apparatuses, circuits, and methods are omitted so as not to obscure the description of the invention with unnecessary detail.

[0013] like Figure 1 As shown, this invention proposes an automated testing method for BDUs, the method comprising the following steps: Step S1: The main control unit controls the signal acquisition module to acquire the background noise signals at both ends of the BDU under test, and the main control unit then processes the signals. Perform spectral analysis to obtain the optimal injection frequency ; Step S2, the main control unit controls the signal generator module to inject at the optimal frequency. A sinusoidal excitation current is generated, and the control signal acquisition module acquires the response voltage across the BDU under test. The measured resistance value is then calculated from the response voltage. Step S3: The main control unit controls the relay switching matrix to switch between forward and reverse current paths, and acquires forward and reverse test data and calculates forward and reverse resistance values ​​through the signal acquisition module. Eliminate contact potential interference and complete preliminary consistency determination; Step S4: The main control unit estimates the contact temperature rise in segments according to the test timing sequence, and performs thermal drift compensation and data correction based on the segmented time-domain thermal model. Corrected to forward standard resistance at standard temperature and reverse standard resistor ; Step S5, the main control unit uses the forward standard resistor and reverse standard resistor Calculate the forward and reverse standard resistance deviation rate, compare the forward and reverse standard resistance deviation rate with a preset threshold, and obtain the BDU contact performance.

[0014] Specifically, in step S1, after the system enters the test mode, the main control unit sends an environmental spectrum scan command, and the signal acquisition module acquires the background noise signals at both ends of the BDU under test at a preset frequency. And controlled by the main control unit Perform a Fast Fourier Transform to calculate the power spectral density of the background noise signal. For the power spectral density in the effective frequency range The optimal injection frequency is selected by screening and choosing the frequency point corresponding to the minimum power spectral density. The optimal injection frequency parameter is then fed back to the main control unit, which generates a sinusoidal excitation current based on this optimal injection frequency parameter.

[0015] In one specific implementation, the signal generator operates within a preset effective frequency range. Internal power spectral density The optimal injection frequency is selected by screening and choosing the frequency point corresponding to the minimum power spectral density. ,Right now .

[0016] Specifically, step S2 includes the following sub-steps: Step S21, the main control unit will select the optimal injection frequency. The signal is sent to the signal generator module, where the DDS chip generates the frequency. A sinusoidal excitation current is applied to the circuit; Step S22: The signal acquisition module acquires the response voltage across the BDU under test. This voltage includes the useful signal of the contact resistance and ambient noise; Step S23, the signal generator module uses a multiplier to convert the response voltage... Multiplying the signal by the two orthogonal reference signals respectively yields the mixed signal, specifically: , , Step S24: After the AC component is filtered out by the low-pass filter, the DC component is obtained from the mixed signal. The measured resistance value of the contact is calculated based on the DC component and the effective value of the sinusoidal excitation current.

[0017] Specifically, in step S3, the main control unit controls the relay switching matrix to switch the forward and reverse current paths, and collects and calculates the forward and reverse resistance values ​​to eliminate the interference of contact potential, obtain a preliminary consistency judgment of BDU contact performance, and provide basic data for subsequent thermal drift compensation.

[0018] When the main control unit sends a forward current loading command, relays K1 and K2 in the relay switching matrix close, while K3 and K4 open, and the test current is activated. The current flows out from the positive terminal of the power supply, through K1 into the positive terminal of the BDU, passes through the main relay contact, flows out from the negative terminal of the BDU, and returns to the negative terminal of the power supply through K2. Figure 2 As shown; the signal acquisition module acquires data according to the measurement method in step S2 and assists the main control unit in calculating the forward measurement resistance. .

[0019] To prevent a short circuit caused by direct connection between the positive and negative terminals of the power supply, the main control unit sends a disconnect command to control all K1~K in the relay switching matrix to disconnect. The system enters a dead time of a preset duration, waiting for the arc to completely dissipate and the residual energy to be exhausted before entering the next stage.

[0020] Next, the main control unit sends a reverse current loading command, closing relays K3 and K4 in the relay switching matrix and opening relays K1 and K2, testing the current. The current flows out from the positive terminal of the power supply, through K3 into the negative terminal of the BDU, passes through the main relay contact, and then flows out from the positive terminal of the BDU, returning to the negative terminal of the power supply via K4. Similarly, the signal acquisition module collects data and assists the main control unit in calculating the negative measured resistance. .

[0021] The main control unit measures the resistance in the positive direction and the resistance in the negative direction. Calculate the average value of the actual resistance of the contact point And calculate the forward and reverse resistance deviation rate δ, the specific calculation formula is as follows: , .

[0022] The forward and reverse resistance deviation rate δ is compared with a preset threshold. A comparison is performed to determine the initial consistency of contact performance. The comparison logic is as follows: If... (A preset threshold, such as 5%), determines that the contact performance of the contact point is qualified; if and Determine if the contact point has positive contact surface oxidation or unidirectional wear; if Furthermore, it was determined that there was reverse contact surface ablation at the contact point.

[0023] Specifically, in step S4, the piecewise time-domain thermal model is constructed through the following process; Step S41, construct the time-varying heat balance equation: ， In the formula, For the contact temperature rise rate, For the current Joule heat input, Heat dissipation output, Contact heat capacity; In step S42, the main control unit performs time-segmented testing according to the sequence of "forward loading - dead time - reverse loading" in step S3, namely, the forward test period, the dead time period, and the reverse test period. The real-time temperature rise of the contacts is calculated segment by segment using the differential method. During the forward test period, the test current is... The main control unit calculates the forward temperature rise of the contacts during this period based on the time-varying heat balance equation. During the dead-time period, the test current is 0, the Joule heat input is 0, and the main control unit only retains the heat dissipation portion. The natural cooling temperature rise of the contacts during this period is calculated to obtain the real-time temperature rise after cooling. During the reverse test period, the test current is... Based on the temperature rise after cooling, the main control unit continues to calculate the reverse temperature rise of the contacts during that period. ; Step S43, the main control unit determines the resistance temperature coefficient based on... Utilizing positive temperature rise Reverse temperature rise ,Will Corrected to forward standard resistance at standard temperature and reverse standard resistor The corrected formula is: , .

[0024] Specifically, in step S5, the corrected forward standard resistor is used. and reverse standard resistor Performing consistency checks specifically includes: Step S51, the main control unit uses the forward standard resistor... and reverse standard resistor Recalculate to obtain the average value of the actual contact resistance And calculate the forward and reverse standard resistance deviation rate. The specific calculation formula is as follows: , .

[0025] The deviation rate of the standard resistance in both directions With preset threshold are compared to complete the consistency verification of contact performance, and the comparison logic is as follows: if , it is determined that the contact performance of the contact is qualified; if and , it is determined that the contact has forward contact surface oxidation or unidirectional wear; if and , it is determined that the contact has reverse contact surface ablation.

[0026] As shown in Figure 3 , the present invention further proposes a BDU automated test system, which includes five modules: a main control unit, a signal generator module, a signal acquisition module, a relay switching matrix, and a measurement carrier; the above BDU automated test method is completed through the above modules.

[0027] In a specific embodiment, after the system is started, the ADC in the signal acquisition module collects the background noise signal at both ends of the BDU under test at a sampling rate of 50kHz and performs FFT analysis. The results are shown in Figure 4 . It can be seen from the figure that there is 100mV power frequency interference at 50Hz and its harmonics, and 50mV inverter switching noise at 1kHz, while at 830Hz, the noise amplitude is the lowest, only 2mV, so the system automatically sets the injection frequency to 830Hz.

[0028] In a specific embodiment, during the forward test period, K1 and K2 are closed, and the forward measurement resistance is ; during the dead-time arc suppression period, all relays are opened to maintain , during which the current drops to 0, and the residual energy of the inductive load is dissipated through the absorption circuit to ensure arc-free switching; during the reverse test period, K3 and K4 are closed, and the measured reverse raw resistance is ; then average resistance value: .

[0029] deviation rate: , the set threshold , since 20.7%>5% and , the system determines that the BDU relay has "severe ablation on the reverse contact surface".

[0030] It should be understood that the sequence numbers of the steps in the above embodiments do not imply the order of execution, and the execution order of each process shall be determined by its function and inherent logic, and shall not constitute any limitation to the implementation process of the embodiments of the present invention.

[0031] In the above embodiments, the descriptions of each embodiment have different focuses. For parts that are not described in detail or recorded in a certain embodiment, please refer to the relevant descriptions of other embodiments.

Claims

1. An automated testing system for BDUs, characterized in that, include: The system comprises a main control unit, a signal generator module, a signal acquisition module, a relay switching matrix, and a measurement carrier. The signal generator module, signal acquisition module, relay switching matrix, and measurement carrier are all electrically connected to the main control unit. The main control unit controls the coordinated operation of the signal generator module, signal acquisition module, relay switching matrix, and measurement carrier to achieve automated BDU testing. The automated BDU testing method includes the following steps: Step S1: The main control unit controls the signal acquisition module to acquire the background noise signals at both ends of the BDU under test. and to Perform spectral analysis to obtain the optimal injection frequency ; Step S2, the main control unit controls the signal generator module to inject at the optimal frequency. A sinusoidal excitation current is generated and applied to the test circuit. The control signal acquisition module synchronously acquires the response voltage across the BDU under test, and the measured resistance value is calculated from the response voltage. Step S3: The main control unit controls the relay switching matrix to switch between forward and reverse current paths, and acquires data and calculates the forward and reverse resistance values ​​through the signal acquisition module. Eliminate contact potential interference and complete preliminary consistency determination; Step S4: The main control unit estimates the contact temperature rise in segments according to the test timing sequence, and performs thermal drift compensation and data correction based on the segmented time-domain thermal model. Corrected to forward standard resistance at standard temperature and reverse standard resistor ; Step S5, the main control unit uses the forward standard resistor and reverse standard resistor Calculate the forward and reverse standard resistance deviation rate, compare the forward and reverse standard resistance deviation rate with a preset threshold, and obtain the BDU contact performance.

2. The BDU automated testing system according to claim 1, characterized in that, In step S1, after the system enters the test mode, the main control unit sends an environmental spectrum scan command, and the signal acquisition module scans the spectrum at a preset frequency. Collect background noise signals at both ends of the BDU under test. And controlled by the main control unit Perform a Fast Fourier Transform to calculate the power spectral density of the background noise signal. For the power spectral density in the effective frequency range The optimal injection frequency is selected by screening and choosing the frequency point corresponding to the minimum power spectral density. And feed it back to the main control unit.

3. The BDU automated testing system according to claim 1, characterized in that, Step S2 includes the following sub-steps: Step S21, the main control unit will select the optimal injection frequency. The signal is sent to the signal generator module, where its internal DDS chip generates a frequency of [frequency value missing]. The sinusoidal excitation signal is amplified and then applied to the test circuit; Step S22: The signal acquisition module acquires the response voltage across the BDU under test. ; Step S23, the main control unit uses a digital multiplier to convert the response voltage... With two orthogonal reference signals , Multiplying them separately yields the mixed signal, specifically: ， ， Step S24: After the AC component is filtered out by the low-pass filter, the DC component is obtained from the mixed signal. The measured resistance value of the contact is calculated based on the DC component and the effective value of the sinusoidal excitation current.

4. The BDU automated testing system according to claim 1, characterized in that, In step S3, the forward resistance value The following method is used to obtain the current: After the main control unit sends a positive current loading command, K1 and K2 in the relay switching matrix are closed, and K3 and K4 are open, and the test current is obtained. It flows out from the positive terminal of the power supply, enters the positive terminal of the BDU through K1, passes through the main relay contact, flows out from the negative terminal of the BDU, and returns to the negative terminal of the power supply through K2; The signal acquisition module acquires data according to the measurement method in step S2, and the main control unit calculates the forward resistance value. .

5. The BDU automated testing system according to claim 1, characterized in that, In step S3, the reverse resistance value The following method is used to obtain the current: When the main control unit sends a reverse current loading command, K3 and K4 in the relay switching matrix are closed, and K1 and K2 are open, and the test current is obtained. The reverse resistance flows out from the positive terminal of the power supply, enters the negative terminal of the BDU via K3, passes through the main relay contact, exits from the positive terminal of the BDU, and returns to the negative terminal of the power supply via K4; the signal acquisition module acquires data according to the measurement method in step S2, and the main control unit calculates the reverse resistance value. .

6. The BDU automated testing system according to claim 1, characterized in that, In step S4, the piecewise time-domain thermal model is constructed through the following process: Step S41, construct the time-varying heat balance equation: ； In the formula, For the contact temperature rise rate, For the current Joule heat input, Heat dissipation output, Contact heat capacity; In step S42, the main control unit performs time-segmented testing according to the "forward loading - dead time - reverse loading" sequence in step S3, namely the forward test period, the dead time period, and the reverse test period. The real-time temperature rise of the contacts is calculated segment by segment using the differential method. During the forward test period, the test current is... The main control unit calculates the forward temperature rise of the contacts during this period based on the time-varying heat balance equation. ; During the dead time period, the test current is 0, the Joule heat input is 0, the main control unit only retains the heat dissipation part, calculates the natural cooling temperature rise of the contacts during this period, and obtains the real-time temperature rise after cooling. During the reverse test period, the test current is Based on the temperature rise after cooling, the main control unit continues to calculate the reverse temperature rise of the contacts during that period. ; Step S43, the main control unit determines the resistance temperature coefficient based on... Utilizing positive temperature rise Reverse temperature rise ,Will Corrected to forward standard resistance at standard temperature and reverse standard resistor The corrected formula is: ， 。 7. The BDU automated testing system according to claim 1, characterized in that, In step S5, the corrected forward standard resistor is used. and reverse standard resistor Performing consistency checks specifically includes: Step S51, the main control unit uses the forward standard resistor and reverse standard resistor Recalculate to obtain the average value of the actual contact resistance And calculate the forward and reverse standard resistance deviation rate. The specific calculation formula is as follows: ， ， Compare the forward and reverse standard resistance deviation rates with a preset threshold to complete the consistency check of contact performance, and the comparison logic is: if , it is determined that the contact performance of the contact is qualified; if and , it is determined that the contact has oxidation of the forward contact surface or unidirectional wear; if and , it is determined that the contact has ablation of the reverse contact surface.

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