A fault simulation test method and system for simulating an ambient temperature by using a resistance box

Abstract

The application discloses a kind of failure simulation test methods and systems for simulating ambient temperature with resistance box, belong to the technical field of automobile thermal management test, including deployment test bench;Obtain target test operating mode;Respectively adjust each adjustable resistance box resistance to target resistance, so that each road resistance value collected by thermal management controller is respectively equivalent to the output value of corresponding temperature sensor under target test operating mode;Control message is obtained from thermal management controller by CAN acquisition equipment;The actual state of control message is compared with the preset control state corresponding to target test operating mode, and the failure simulation test result is output according to the comparison result.The present application replaces outdoor, indoor, evaporation, refrigerant and water temperature sensor with adjustable resistance box and constructs complete closed-loop test bench, solves the technical problem that existing temperature sensor simulation technology is only used as an independent device, and does not form a closed-loop verification test bench with thermal management system execution components.

Description

Technical Field

[0001] This application belongs to the field of automotive thermal management testing technology, and specifically relates to a fault simulation testing method and system that uses a resistance box to simulate ambient temperature. Background Technology

[0002] With the shortening iteration cycle of new energy vehicles, the need for verification of automotive air conditioning thermal management control function strategies is becoming increasingly urgent.

[0003] Existing temperature sensor simulation technologies are mostly used as standalone devices, failing to form a closed-loop test bench with the thermal management system's execution components. This makes it impossible to verify coordinated control strategies such as compressor start-up and shutdown, and fan speed regulation. Furthermore, existing solutions can only simulate normal temperature conditions and cannot cover fault states such as sensor open circuits, short circuits, and resistance drift, resulting in a lack of verification methods for fault diagnosis strategies. In addition, traditional verification relies on real-vehicle road tests or environmental chamber tests, which suffer from drawbacks such as long cycles, high costs, and seasonal limitations. Summary of the Invention

[0004] To address the aforementioned issues, this application provides a fault simulation test method and system that uses a resistance box to simulate ambient temperature, thus resolving the technical problem that existing temperature sensor simulation technology is only used as an independent device and does not form a closed-loop verification bench with the thermal management system execution components.

[0005] In a first aspect, embodiments of this application provide a fault simulation test method using a resistance box to simulate ambient temperature, comprising the following steps: A test bench is deployed, which is equipped with a thermal management controller, a CAN acquisition device, and a five-channel adjustable resistor box. The five-channel adjustable resistor box replaces the outdoor temperature sensor, indoor temperature sensor, evaporation temperature sensor, refrigerant temperature sensor, and water temperature sensor, respectively. Obtain the target test conditions, which include the target resistance values ​​corresponding to each temperature sensor; Adjust the resistance values ​​of each adjustable resistor box to the target resistance value so that the resistance values ​​collected by the thermal management controller are equivalent to the output values ​​of the corresponding temperature sensors under the target test conditions. Control messages are acquired from the thermal management controller via a CAN acquisition device; The actual state of the control message is compared with the preset control state corresponding to the target test condition, and the fault simulation test result is output based on the comparison result.

[0006] In one embodiment, before obtaining the target test condition, the method further includes: Establish a resistance-temperature characteristic table for each temperature sensor, which records the nominal resistance of each temperature sensor at different temperatures. The target resistance value of each temperature sensor under the target test conditions is determined based on the resistance-temperature characteristic table.

[0007] In one embodiment, before adjusting the resistance values ​​of each adjustable resistor box to the target resistance value, the method further includes: Establish a multi-sensor collaborative operating condition mapping table. The multi-sensor collaborative operating condition mapping table records the target resistance value combination of the five-channel adjustable resistor box and the corresponding preset control state for each test case. The target test conditions are determined based on the multi-sensor collaborative working condition mapping table, and the target resistance values ​​of the five-channel adjustable resistor boxes are extracted.

[0008] In one embodiment, before acquiring control messages from the thermal management controller via the CAN acquisition device, the method further includes: Connect the five-channel adjustable resistor box to the original temperature sensor sampling circuit of the thermal management controller to determine the sensor sampling interface; A fault simulation switch group is added to the sensor sampling interface. The fault simulation switch group includes a circuit breaker, a short circuit switch and a drift adjustment resistor. Switch the state of the fault simulation switch group to perform open circuit simulation, short circuit simulation, or drift simulation to obtain the fault simulation temperature signal.

[0009] In one embodiment, a fault simulation switch group is added at the sensor sampling interface, including: A circuit breaker is connected in series between the output of the five-channel adjustable resistor box and the input of the sensor sampling interface. A short-circuit switch is connected in parallel across the five-way adjustable resistor box; A drift adjustment resistor is connected in series or parallel between the five-channel adjustable resistor box and the sensor sampling interface.

[0010] In one embodiment, the fault simulation switch group state is switched to perform open-circuit simulation, short-circuit simulation, or drift simulation to obtain a fault simulation temperature signal, including: Disconnect the circuit breaker to cut off the loop between the five-way adjustable resistor box and the sensor sampling interface. The thermal management controller detects the open circuit state and obtains the open circuit fault temperature signal. Read the open circuit fault code and limp control message output by the thermal management controller, compare the open circuit fault code with the open circuit fault identification strategy, and compare the limp control message with the protection shutdown strategy to obtain the open circuit strategy verification result. The open circuit fault temperature signal and the open circuit strategy verification results are incorporated into the fault simulation temperature signal.

[0011] In one embodiment, switching the state of the fault simulation switch group to perform open-circuit simulation, short-circuit simulation, or drift simulation to obtain a fault simulation temperature signal further includes: When the short-circuit switch is closed, the five-way adjustable resistor box is short-circuited. The thermal management controller detects the short-circuit state and obtains the short-circuit fault temperature signal. Read the short-circuit fault code and power limiting message output by the thermal management controller, compare the short-circuit fault code with the short-circuit fault identification strategy, and compare the power limiting message with the power limiting strategy to obtain the short-circuit strategy verification result. The short-circuit fault temperature signal and the short-circuit strategy verification results are incorporated into the fault simulation temperature signal.

[0012] In one embodiment, switching the state of the fault simulation switch group to perform open-circuit simulation, short-circuit simulation, or drift simulation to obtain a fault simulation temperature signal further includes: When the circuit breaker is closed and the short circuit breaker is open, the drift regulating resistor is connected in series or parallel to the main circuit. When the actual resistance value of the circuit deviates from the nominal value of the resistance temperature characteristic table, the thermal management controller detects the resistance drift state and obtains the drift fault temperature signal. Read the rationality verification message output by the thermal management controller, compare the rationality verification message with the drift fault identification strategy, compare the fault tolerance processing message with the fault tolerance processing strategy, and obtain the drift strategy verification result. The drift fault temperature signal and the drift strategy verification results are incorporated into the fault simulation temperature signal.

[0013] In one embodiment, comparing the actual state of the control message with the preset control state corresponding to the target test condition includes: The compressor request signal, fan duty cycle signal, water pump speed signal, and high-pressure heater power signal are parsed from the control message and used as a set of actual state parameters. Based on the target test conditions, extract the corresponding preset control states as the set of reference state parameters; The actual state parameter set is compared with the baseline state parameter set item by item to determine whether each actual state parameter meets the preset control state, and the comparison result is obtained.

[0014] In one embodiment, after outputting the fault simulation test results, the method further includes: The control message after the five adjustable resistor boxes are synchronously adjusted is compared with the control strategy specification corresponding to the target test condition. Verify the collaborative control logic of the compressor, cooling fan, water pump and high-pressure heater in a scenario of synchronous adjustment of five adjustable resistor boxes; The results of the collaborative control logic verification are included in the results of the fault simulation test.

[0015] Secondly, embodiments of this application provide a fault simulation test system that uses a resistance box to simulate ambient temperature, comprising: The test bench deployment module is used to deploy the test bench, which is equipped with a thermal management controller, a CAN acquisition device, and a five-channel adjustable resistor box. The five-channel adjustable resistor box replaces the outdoor temperature sensor, indoor temperature sensor, evaporation temperature sensor, refrigerant temperature sensor, and water temperature sensor, respectively. The operating condition acquisition module is used to acquire the target test operating condition, which includes the target resistance value corresponding to each temperature sensor. The resistance adjustment module is used to adjust the resistance of each adjustable resistor box to the target resistance value, so that the resistance values ​​collected by the thermal management controller are equivalent to the output values ​​of the corresponding temperature sensors under the target test conditions. The message acquisition module is used to acquire control messages from the thermal management controller via a CAN acquisition device; The strategy verification module is used to compare the actual state of the control message with the preset control state corresponding to the target test condition, and output the fault simulation test result based on the comparison result.

[0016] Compared with the prior art, this application has the following advantages: 1. This invention replaces the outdoor, indoor, evaporator, refrigerant, and water temperature sensors with an adjustable resistance box and constructs a complete closed-loop test bench. This solves the technical problem that existing temperature sensor simulation technology is only used as an independent device and does not form a closed-loop verification bench with the thermal management system execution components. It enables rapid verification of thermal management function strategies without the need for actual vehicles, environmental chambers, or expensive professional equipment. 2. This invention solves the technical problem that existing resistor box simulation schemes can only simulate normal temperature conditions and cannot cover sensor fault states by adding a fault simulation switch group containing a circuit breaker, a short circuit switch and a drift adjustment resistor between the resistor box and the sensor sampling interface. This invention fully verifies the fault diagnosis strategy and limp control strategy of the thermal management controller under the three fault modes of open circuit, short circuit and drift. 3. By establishing a multi-sensor collaborative operating condition mapping table and synchronously adjusting the resistance values ​​of the five-way resistor box, this invention solves the technical problem that existing technologies often focus on simulating single sensor signals and are difficult to verify multi-parameter coupled control scenarios. It achieves comprehensive verification of the collaborative control logic of compressors, cooling fans, radiators and high-pressure heaters under complex environmental boundary conditions.

[0017] Other features and advantages of this application will be set forth in the description which follows, and will be apparent in part from the description, or may be learned by practicing the application. The objectives and other advantages of this application may be realized and obtained by means of the structures pointed out in the description, claims and drawings. Attached Figure Description

[0018] To more clearly illustrate the technical solutions in the embodiments of this application or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are some embodiments of this application. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0019] Figure 1 A schematic diagram of the original thermal management function test bench architecture provided by the present invention is shown; Figure 2 A schematic diagram of the novel thermal management test bench solution provided by the present invention is shown; Figure 3 A flowchart of the sensor fault simulation test provided by the present invention is shown; Figure 4 A schematic diagram of the process provided by the present invention is shown. Detailed Implementation

[0020] To make the objectives, technical solutions, and advantages of the embodiments of this application clearer, the technical solutions of the embodiments of this application will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of this application, not all embodiments. Based on the embodiments of this application, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of this application.

[0021] In related technologies, the verification of automotive air conditioning thermal management control strategies relies on real-vehicle road tests or environmental chamber tests, which suffers from drawbacks such as long cycles, high costs, and seasonal limitations. Some solutions use adjustable resistors to simulate temperature sensors, but these are only used as independent devices and do not form a closed-loop test bench with the thermal management system's execution components, making it impossible to verify multi-component collaborative control strategies. Furthermore, existing solutions cannot simulate fault states such as sensor open circuits, short circuits, and resistance drift, resulting in a lack of verification methods for fault diagnosis strategies, limp-home modes, and redundancy switching logic in the thermal management controller, leading to insufficient test coverage.

[0022] To address this, this application provides a fault simulation test method for simulating ambient temperature using a resistance box. By constructing a complete thermal management function test bench, replacing the real temperature sensor with an adjustable resistance box, and adding a fault simulation switch group to simulate open circuit, short circuit, and resistance drift, the thermal management control strategy under normal and fault conditions can be verified without a real vehicle or environmental chamber, significantly reducing verification costs and shortening the verification cycle.

[0023] In this specific embodiment, HVAC represents air conditioning unit, TDU represents thermal management controller, EXV represents electronic expansion valve, WPTC represents high-pressure heater, and CAN represents controller area network.

[0024] Please see Figure 1 , Figure 1 This is a schematic diagram of the original thermal management function test bench architecture. The original bench includes a regulated power supply, HVAC unit, thermal management controller (TDU), compressor, air conditioning piping, electronic expansion valve (EXV), condenser, cooling fan, radiator, connecting hoses, high-pressure heater (WPTC), five-way valve, heater pump, motor pump, battery pump, outdoor temperature sensor, indoor temperature sensor, evaporator temperature sensor, refrigerant temperature sensor, water temperature sensor, wiring harness, host computer, and CAN data acquisition equipment. These components are connected to the power supply, host computer, and CAN testing equipment via dedicated wiring harnesses to simulate the real vehicle system and test functional strategies on the bench.

[0025] Please see Figure 2 , Figure 2 This is a schematic diagram of the new thermal management test bench solution. The connection layout of the components—including the regulated power supply, HVAC unit, TDU (Thermal Management Unit), compressor, air conditioning piping, electronic expansion valve (EXV), condenser, cooling fan, radiator, connecting hoses, high-pressure heater (WPTC), five-way valve, heater pump, motor pump, battery pump, CAN test equipment, and host computer—remains unchanged. All five temperature sensors in the original test bench circuit—outdoor temperature sensor, indoor temperature sensor, evaporator temperature sensor, refrigerant temperature sensor, and water temperature sensor—are replaced with adjustable resistance boxes with a resistance range of 0 to 99999Ω to simulate these sensors. Each resistance box is connected to the original sensor sampling interface via a wiring harness, with the wiring harness pin definitions identical to the original sensor wiring harness, ensuring input impedance matching of the TDU sampling circuit. Each resistance box can be set with different resistance values ​​according to requirements, corresponding to different temperatures based on the resistance-temperature characteristics table of each sensor, for testing specific environmental conditions.

[0026] Please see Figure 4 , Figure 4 This is a general flowchart of a fault simulation test method for a resistance box simulating ambient temperature, provided in an embodiment of this application. The method includes steps S110 to S170.

[0027] like Figure 4 As shown, the method includes the following steps S110 to S170.

[0028] S110, deploy test bench hardware.

[0029] Specifically, an air conditioning thermal management function test bench was constructed. The bench includes a regulated power supply, an HVAC unit, a thermal management controller (TDU), a compressor, air conditioning piping, an electronic expansion valve (EXV), a condenser, a cooling fan, a radiator, connecting hoses, a high-pressure heater (WPTC), a five-way valve, a warm air pump, a motor-driven pump, a battery-powered pump, wiring harnesses, a host computer, and a CAN data acquisition device. Each component was connected according to the thermal management electrical schematic, the power was turned on, and the test bench was debugged until the function was successfully implemented. The relevant messages issued by the TDU were then observed on the host computer.

[0030] S120, replace the temperature sensor with an adjustable resistor box.

[0031] Specifically, the outdoor temperature sensor, indoor temperature sensor, evaporator temperature sensor, refrigerant temperature sensor, and water temperature sensor will be replaced with an adjustable resistor box. The adjustable resistor box has a resistance range of 0 to 99999Ω. The resistor box is connected to the original sensor sampling interface via a wiring harness, and the wiring harness pin definitions are completely consistent with the original sensor wiring harness.

[0032] S130. Establish a resistance temperature characteristic table.

[0033] Specifically, a resistance-temperature characteristic table is established for each temperature sensor. This table records the nominal resistance of each sensor at different temperatures. The nominal resistance is obtained from the sensor's factory calibration data. The input parameter for the resistance-temperature characteristic table is temperature T (in °C), and the output parameter is the nominal resistance. The unit is Ω.

[0034] The process of constructing the resistance temperature characteristic table includes the following sub-steps: S1301. Collect raw calibration data. Obtain the factory calibration certificates for the outdoor temperature sensor, indoor temperature sensor, evaporator temperature sensor, refrigerant temperature sensor, and water temperature sensor, or extract the calibration parameters from the vehicle's BOM system. The calibration data should cover the full operating range of the sensor, with no fewer than 10 temperature sampling points, including extreme temperature points. Taking the outdoor temperature sensor as an example, its calibration temperature points typically include -40℃, -30℃, -20℃, -10℃, 0℃, 10℃, 20℃, 30℃, 40℃, and 50℃. S1302. Establish a discrete data table. Organize the factory calibration data into a discrete data table, with table fields including temperature sequence number and temperature value. and nominal resistance The table below shows an example of discrete calibration data for an outdoor temperature sensor:

[0035] S1303, Piecewise Linear Interpolation. For temperature points not directly given in the discrete calibration data, piecewise linear interpolation is used to calculate the nominal resistance. Assume two adjacent calibration points are known... , and , If the temperature T to be determined is within this range, the nominal resistance is calculated using the following formula: ; In the formula, The nominal resistance at the temperature to be determined is expressed in Ω. The nominal resistance at the known low temperature point is expressed in Ω. The nominal resistance at a known high temperature point is expressed in Ω. The temperature value of the known low point is given in °C. The temperature value of the known high-temperature point is given in °C. The desired temperature value is given in °C. Through the piecewise linear interpolation described above, the discrete calibration data is expanded into a continuously searchable table of resistance-temperature characteristics. The temperature resolution is set to 1 °C, meaning that each 1 °C interval corresponds to a nominal resistance value, facilitating quick lookup and setting during testing.

[0036] S131. Establish a multi-sensor collaborative operating condition mapping table.

[0037] Specifically, a multi-sensor collaborative operating condition mapping table is established. The mapping table uses the test case number as an index, with each row recording a set of target resistance values ​​for five adjustable resistor boxes and their corresponding preset control states. The target resistance values ​​are obtained by looking up the resistance-temperature characteristic table, and the preset control states are determined according to the thermal management control strategy specifications.

[0038] The process of constructing the multi-sensor collaborative operating condition mapping table is as follows: S1311. Determine the test case set. Based on the thermal management control strategy specification, extract all test scenarios involving temperature boundary conditions to form a test case set. Each test case should include a test case number, test case name, description of the target test condition, and expected control behavior. S1312. Decompose the target test conditions. Decompose the target test conditions of each test case into the target temperature values ​​of five temperature sensors, namely, outdoor temperature target value T1, indoor temperature target value T2, evaporation temperature target value T3, refrigerant temperature target value T4, and water temperature target value T5; S1313. Query the target resistance value. Based on the resistance-temperature characteristic table established in S130, query the nominal resistance value corresponding to each target temperature value through piecewise linear interpolation. This value is used as the target resistance value for the five-channel adjustable resistance box, denoted as R1. set R2 set R3 set R4 set and R5 set ; S1314. Define preset control states. Based on the expected control behavior of each test case in the thermal management control strategy specification, define preset control states. Preset control states include compressor request signal states, fan duty cycle target values, water pump speed target values, high-pressure heater power target values, and expected fault code states; preset control states are stored in the form of a set of baseline state parameters. S1315. Create a mapping table. Integrate the above information into a mapping table. The following table shows some examples of mapping tables:

[0039] S1316. Mapping Table Storage and Retrieval. The mapping table is stored as a spreadsheet file readable by the host computer or embedded in the test software database. During testing, the operator enters the test case number, and the system automatically extracts the corresponding five target resistance values ​​and preset control states, displaying them on the operation interface to guide the test execution.

[0040] S140, Normal operating condition simulation test.

[0041] Specifically, based on the test cases and the resistance-temperature characteristic table, adjust the resistance values ​​of each resistance box to achieve the expected operating temperature. During the adjustment process, the resistance setting error must meet the accuracy requirements.

[0042] The detailed execution steps for the normal operating condition simulation test are as follows: S1401. Load test cases. Enter the target test case number in the host computer test software and extract the target resistance value R1 of the five-channel adjustable resistor box from the multi-sensor collaborative operating condition mapping table. set Up to R5 set and preset control states; S1402. Adjust the resistance values ​​of the resistance boxes. The operator adjusts the knobs of the five adjustable resistance boxes in sequence until the readings of each resistance box are close to the target resistance values. The adjustment sequence follows the coupling priority of each temperature signal in the thermal management control strategy. Usually, the outdoor temperature is set first, then the indoor temperature, followed by the evaporator temperature and refrigerant temperature, and finally the water temperature, to avoid transient false triggering of the control strategy. S1403, Resistance Error Verification. A high-precision digital multimeter is used to measure the actual output resistance R of each resistance box in real time. set Calculate the resistance setting error The resistance setting error is calculated using the following formula: ; In the formula, Set an error for the resistance value; The actual resistance value set for the adjustable resistance box, in Ω; The resistance value is the nominal resistance value indicated in the resistance-temperature characteristic table, and the unit is Ω.

[0043] The error threshold is set to one percent, that is... This threshold is determined based on the adjustment accuracy of the adjustable resistor box and the analog-to-digital conversion resolution of the TDU sampling circuit. A resistance error of one percent corresponds to a temperature error of no more than 0.5℃, meeting the accuracy requirements for verifying the thermal management control strategy.

[0044] S1404. Steady-state determination. After adjusting the resistance values ​​of all five resistor boxes to meet the error threshold requirements, maintain stable resistance values ​​and observe the TDU control messages collected by the host computer. When the fluctuation range of key parameters such as compressor request signal and fan duty cycle is less than 2% within 5 consecutive sampling cycles, the system is determined to have reached steady state. S1405. Record the normal analog temperature signal. Under steady-state conditions, record the actual resistance value and corresponding equivalent temperature of the five-channel adjustable resistor box as the normal analog temperature signal for subsequent verification steps.

[0045] S150, Configure fault simulation switch group.

[0046] Specifically, a fault simulation switch group is added between the adjustable resistor box and the sensor sampling interface. The fault simulation switch group includes a circuit breaker, a short-circuit switch, and a drift adjustment resistor.

[0047] The detailed configuration process for the fault simulation switch group is as follows: S1501. Switchgear Structure Design. The fault simulation switchgear is integrated onto an insulated operating panel, measuring 200mm × 150mm. The panel is mounted on the benchtop operating surface for easy access. Five fault simulation switchgear groups are installed on the panel, each corresponding to one temperature sensor simulation channel, numbered G1 to G5 respectively. Each fault simulation switchgear group includes one circuit breaker K1, one short-circuit switch K2, and one drift adjustment resistor R. shift Circuit breaker K1 is a single-pole single-throw rocker switch with a rated current of 2A and a rated voltage of 30V, connected in series between the output of the adjustable resistor box and the input of the sensor sampling interface; short-circuit switch K2 is a single-pole single-throw rocker switch with a rated current of 2A, connected in parallel across the adjustable resistor box; drift adjustment resistor R... shift Metal film resistors with an accuracy of 1% are selected, and the resistance value is selected according to the fault simulation requirements, usually 10% to 30% of the nominal resistance value. The series or parallel connection method is selected through single-pole double-throw switch K3. S1502, Series connection method. When K3 is switched to the series position, the drift adjustment resistor R... shift With adjustable resistance box R box Series connection, total series resistance R drift =R box +R shift At this time, the actual resistance of the circuit is greater than the nominal resistance, simulating a positive resistance drift fault; S1503, Parallel connection mode. When K3 is switched to the parallel position, the drift adjustment resistor R... shift With adjustable resistance box R box Parallel connection, equivalent resistance R in parallel eq Calculate using the following formula: ; In the formula, R eq R is the equivalent resistance in parallel, in Ω. box Set the resistance value of the adjustable resistance box, in Ω; R shift The value of the drift adjustment resistor is in Ω. At this time, the actual resistance of the circuit is less than the nominal resistance, simulating a negative drift fault. S1504, Electrical Connection Verification. After configuration, use a multimeter to measure the loop resistance in each switch state: when K1 is open, the loop resistance should be infinite; when K2 is closed, the loop resistance should be less than 0.5Ω; when K3 is in the series position and R... shift =1000Ω, R box When the resistance is 2409Ω, the circuit resistance should be 3409Ω; K3 is placed in parallel and R shift =10000Ω, R box When the resistance is 10000Ω, the loop resistance should be 5000Ω. If the measurement results meet expectations, the fault simulation switch group is configured correctly.

[0048] Please see Figure 3 , Figure 3 This is a flowchart for sensor fault simulation testing. Figure 3 The execution logic and state switching relationships of three fault modes—open circuit simulation, short circuit simulation, and drift simulation—are illustrated.

[0049] S160, Perform a fault simulation test.

[0050] Fault simulation testing includes three modes: open circuit simulation, short circuit simulation, and drift simulation.

[0051] S161, Circuit Breaker Simulation.

[0052] Specifically, the circuit breaker is disconnected, cutting off the loop between the adjustable resistor box and the sensor sampling interface. The TDU detects an open circuit, with an equivalent resistance of infinite, thus obtaining the open circuit fault temperature signal. The open circuit fault code and limp-off control message output by the TDU are read. The open circuit fault code is compared with the open circuit fault identification strategy, and the limp-off control message is compared with the protection shutdown strategy to verify the TDU's fault identification and protection actions when the sensor is open-circuited.

[0053] The detailed execution steps for circuit breaker simulation are as follows: S1611. Set normal operating conditions. First, adjust the five-channel adjustable resistor box to the normal resistance value corresponding to the target test condition according to S140, and confirm that the system is in a steady state and the TDU outputs a normal control message; S1612. Inject open circuit fault. Select the channel to be simulated for the open circuit fault, such as the evaporation temperature channel, and disconnect the circuit breaker K1 corresponding to the channel. At this time, the evaporation temperature sampling circuit is open and the equivalent resistance is infinite. The sampling voltage of the TDU's ADC3 channel is pulled up to the reference voltage or pulled down to zero potential, depending on the bias design of the TDU sampling circuit. S1613. Fault Response Acquisition. The fault diagnosis messages sent by the TDU are continuously acquired via the CAN acquisition device. After the open-circuit fault is injected, the TDU is expected to report an open-circuit fault code for the evaporator temperature sensor within 500ms. The fault code format conforms to the 0x3101 fault code definition in the UDS diagnostic protocol. Simultaneously, the limp-out control message is acquired. The compressor request signal ACRequestCommand is expected to change from 0X1 to 0X0 within 100ms, i.e., the compressor is prohibited from starting and enters the safety protection state. S1614. Comparison and Verification. Compare the collected circuit breaker fault codes with the preset circuit breaker fault identification strategy to confirm whether the fault code type, fault level, and fault occurrence timestamp conform to the strategy specifications. Compare the limp-off control message with the protection shutdown strategy to confirm whether the compressor shutdown delay, fan delay shutdown logic, and water pump operation maintenance logic conform to the strategy specifications. If all comparison items conform, the circuit breaker strategy verification result is passed; if there is a deviation, record the deviation item and the measured value as part of the fault simulation temperature signal. S1615. Recovery and Iteration. Close K1 to restore the normal connection of the evaporation temperature channel. Observe whether the TDU clears the fault code and restores normal control within the predetermined time. Perform open-circuit simulation tests on the remaining four temperature sensor channels in sequence using the same method.

[0054] S162, Short-circuit simulation.

[0055] Specifically, closing the short-circuit switch shorts the adjustable resistor box. The TDU detects a short circuit, with an equivalent resistance of 0Ω, and obtains the short-circuit fault temperature signal. The short-circuit fault code and power limiting message output by the TDU are read. The short-circuit fault code is compared with the short-circuit fault identification strategy, and the power limiting message is compared with the power limiting strategy to verify the TDU's fault identification and power limiting actions when the sensor is short-circuited.

[0056] The detailed steps for performing a short-circuit simulation are as follows: S1621. Set normal operating conditions. Following S140, adjust the five-channel adjustable resistor box to the normal resistance value corresponding to the target test condition, and confirm that the system is in a steady state. S1622. Inject short-circuit fault. Select the channel to be simulated for the short-circuit fault, such as the water temperature channel, and close the short-circuit switch K2 corresponding to the channel. At this time, the water temperature sampling circuit is short-circuited, the equivalent resistance is 0Ω, and the sampling voltage of the TDU's ADC5 channel is close to zero potential. S1623. Collect fault response. Continuously collect fault diagnosis messages sent by the TDU via the CAN acquisition device. It is expected that the TDU will report a water temperature sensor short circuit fault code within 500ms, with the fault code format conforming to the 0x3205 fault code definition in the UDS diagnostic protocol. Simultaneously, collect power limiting messages. It is expected that the WPTC power request signal should be limited to 0% from its current value within 200ms, i.e., preventing the high-pressure heater from starting to prevent overheating risk. S1624. Comparison and Verification. Compare the collected short-circuit fault codes with the preset short-circuit fault identification strategy to confirm the fault code type and fault level. Compare the power limiting message with the power limiting strategy to confirm whether the WPTC disable logic, fan forced start logic, and compressor maintenance logic comply with the strategy specifications. If all comparison items are compliant, the short-circuit strategy verification result is passed; if there are deviations, record the deviation items and measured values. S1625. Recovery and Iteration. Disconnect K2, restore the normal connection of the water temperature channel, and observe the TDU fault clearing and recovery logic. Perform short-circuit simulation tests on the remaining channels in sequence using the same method.

[0057] S163, Drift Simulation.

[0058] Specifically, with the circuit breaker closed and the short-circuit switch open, the drift regulating resistor is connected in series or in parallel to the main circuit, causing the actual resistance value of the circuit to deviate from the nominal value of the resistance temperature characteristic table. The TDU detects the resistance drift state and obtains the drift fault temperature signal.

[0059] The detailed steps for performing the drift simulation are as follows: S1631. Set normal operating conditions. Following S140, adjust the five-channel adjustable resistor box to the normal resistance value corresponding to the target test condition, and confirm that the system is in a steady state. S1632. Select Drift Mode. Choose either series drift or parallel drift mode according to the test requirements. Series drift mode is used to simulate the resistance increase fault caused by sensor aging, while parallel drift mode is used to simulate the resistance decrease fault caused by sensor moisture or poor contact. S1633, Calculate the resistance after drift. If a series drift mode is used, connect the drift adjustment resistor R_shift to the adjustable resistor box. Series connection, total resistance of series connection Calculate using the following formula: ; In the formula, This is the total series drift resistance, in Ω; Set the resistance value for the adjustable resistance box, in Ω; This is the resistance value of the drift adjustment resistor, in Ω.

[0060] If parallel drift mode is used, the drift adjustment resistor will be... With adjustable resistance box Parallel connection, equivalent resistance of parallel connection Calculate using the following formula: ; In the formula, This is the equivalent resistance in parallel, in Ω. Set the resistance value for the adjustable resistance box, in Ω; This is the resistance value of the drift adjustment resistor, in Ω.

[0061] Actual resistance of the circuit for or The drift amount is calculated using the following formula: ; In the formula, This represents the resistance drift. This represents the actual circuit resistance after series or parallel connection, in Ω. The resistance value is the nominal resistance value indicated in the resistance-temperature characteristic table, and the unit is Ω.

[0062] The drift threshold is set between 10% and 30%, and this threshold is determined based on the statistical distribution of sensor aging and poor contact faults. Deviations below 10% are usually absorbed by the controller's fault tolerance, while deviations above 30% exceed the normal aging range and constitute a significant fault.

[0063] During testing, The selection should make It falls within the 10% to 30% range.

[0064] S1635, Injection drift fault. Taking the outdoor temperature channel as an example, under normal operating conditions... =2409Ω corresponds to 30℃. If simulating positive drift, select... =1000Ω, after series connection =3409Ω, corresponding to an equivalent temperature of approximately 18℃. =41.5%, which is a significant fault. Switch K3 to the serial position to inject a drift fault. S1636. Collect fault response. It is expected that the TDU will report an outdoor temperature sensor rationality verification fault code within 2 seconds. The fault code format conforms to the 0x3301 fault code definition in the UDS diagnostic protocol. At the same time, collect the fault tolerance processing message to confirm whether the TDU has started redundant temperature source switching or restricted the air conditioning function. S1637. Comparison and Verification. Compare the rationality verification message with the drift fault identification strategy, and compare the fault tolerance processing message with the fault tolerance processing strategy to confirm whether the drift judgment threshold, delay time, and fault tolerance actions comply with the strategy specifications. Record the drift strategy verification results; S1638, Recovery and Iteration. Return K3 to its normal position and remove... Once the channel connection is restored, tests are performed on the remaining channels and drift mode in sequence.

[0065] S170, CAN message acquisition and policy verification.

[0066] Specifically, the CAN acquisition device reads relevant messages sent by the TDU on the host computer. The compressor request signal, fan duty cycle signal, water pump speed signal, and high-pressure heater power signal are parsed from the control messages. The parsed results are compared with the values ​​defined in the strategy specification to determine whether the control parameters conform to the strategy specification, thus obtaining the strategy verification result. Based on the strategy verification result, the fault simulation test result is output.

[0067] The detailed steps for CAN message acquisition and policy verification are as follows: S1701. Configure CAN communication parameters. In the host computer's CAN analysis software, configure the communication parameters of the CAN acquisition device: set the baud rate to 500Kbps, the sampling point to 75%, the synchronization jump width to 1 time quantum, and enable the 120Ω terminating resistor. Configure message filtering rules to only receive message identifiers sent by the TDU, including control status messages in the range of 0x100 to 0x1FF and fault diagnosis messages in the range of 0x300 to 0x3FF, reducing bus data volume and improving parsing efficiency. S1702. Load the DBC parsing file. Import the DBC database file that matches the TDU. This file defines the signal name, start bit, length, scale factor, offset, and physical unit of each control message. The key signals are defined as follows: Compressor Request Command signal ACRequestCommand: start bit 0, length 1, scale factor 1, offset 0, unit none, 0X0 indicates off, 0X1 indicates on; Fan Duty signal FanDuty: start bit 8, length 8, scale factor 0.5, offset 0, unit %, range 0% to 100%; Pump Speed ​​signal PumpSpeed: start bit 16, length 16, scale factor 1, offset 0, unit rpm, range 0rpm to 6000rpm; WPTC Power signal WPTCPower: start bit 32, length 8, scale factor 0.5, offset 0, unit %, range 0% to 100%. S1703. Acquire raw response messages. Based on the acquisition configuration parameters, the CAN acquisition device acquires the control request signal sent by the TDU at a period of 10ms to obtain the raw response message. The raw response message is stored in hexadecimal format and converted into physical quantities in real time for display on the host computer interface; S1704. Parse actual status parameters. From the original response message, parse the compressor request signal, fan duty cycle signal, water pump speed signal, and high-pressure heater power signal according to the DBC definition to form a set of actual status parameters. At the same time, parse the list of existing fault codes from the fault diagnosis message to form a set of actual fault states. S1705. Extract baseline state parameters. Based on the target test conditions, extract the corresponding preset control states from the multi-sensor collaborative operating condition mapping table as the baseline state parameter set. The baseline state parameter set includes the expected compressor request state, expected fan duty cycle, expected water pump speed, expected WPTC power, and expected fault code state; S1706. Item-by-item comparison and judgment. Compare the actual state parameter set with the baseline state parameter set item by item to determine whether each actual state parameter conforms to the preset control state. The comparison tolerance is set as follows: switch signals must be completely consistent; duty cycle signals deviation does not exceed 2%; speed signals deviation does not exceed 50 rpm; fault code signals must be completely consistent. If all parameters are within the tolerance range, the strategy verification result is passed; if there are parameters exceeding the tolerance, the strategy verification result is failed, and the abnormal parameter name, measured value, and baseline value are recorded. S1707. Output Fault Simulation Test Results. Integrate the strategy verification results, open-circuit strategy verification results, short-circuit strategy verification results, drift strategy verification results, and collaborative control logic verification results to generate a fault simulation test report. The report includes the test case number, test time, set resistance value of each resistor box, actual resistance value, equivalent temperature, measured control message values, comparison results, and final judgment conclusion. The report is exported in spreadsheet or PDF format for archiving and future reference.

[0068] The technical solution of this application will be described in detail below with reference to specific embodiments.

[0069] Example 1: Verification of evaporation temperature protection strategy.

[0070] The verification objective is to set the evaporator temperature protection threshold for the electric compressor to be 0°C to 2°C. When the evaporator temperature drops to 0°C, the compressor should switch off; when the evaporator temperature rises to 2°C, the compressor should resume operation. The 0°C threshold is set based on the risk of evaporator frosting. Below this temperature, frost may form on the evaporator surface, leading to decreased heat exchange efficiency and liquid slugging damage to the compressor. The 2°C threshold is set based on the frost melting time. A return to this temperature indicates that the frost has fully melted, and the system can safely resume operation.

[0071] The testing steps are as follows: Set the outdoor temperature resistance box to 2409Ω, corresponding to 30℃; the indoor temperature resistance box to 10000Ω, corresponding to 25℃; the refrigerant temperature resistance box to 41518Ω, corresponding to -5℃; the water temperature resistance box to 1653Ω, corresponding to 30℃; and the evaporator temperature resistance box to 6999Ω, corresponding to 5℃. After setting, turn on the air conditioner by clicking the large screen air conditioner switch or by sending a switch signal from the host computer. The air conditioning system will operate normally. Read the compressor request signal on the host computer via the CAN acquisition device to confirm ACRequestCommand=0X1, indicating that the compressor is operating normally.

[0072] Then adjust the resistance of the evaporation temperature resistance box to 9000Ω, corresponding to 0℃, and observe whether ACRequestCommand becomes 0X0; if it becomes 0X0, the software strategy is correct; then adjust the resistance of the evaporation temperature resistance box to 8132Ω, corresponding to 2℃, and confirm that ACRequestCommand is restored to 0X1; if it is not restored, the strategy does not conform to the specification.

[0073] Example 2: Verification of the heating power strategy of the high-pressure heater WPTC.

[0074] The verification objective is to adjust the WPTC auxiliary heating power in stages based on the difference between the target water temperature and the actual water temperature when the engine coolant temperature is ≤65℃. The target water temperature is determined based on the outdoor temperature and the set temperature.

[0075] The testing steps are as follows: Turn on the air conditioner on the large screen or host computer and set the temperature to 22℃. Adjust the outdoor temperature resistor box to 12571Ω, corresponding to -5℃; the indoor temperature resistor box to 10000Ω, corresponding to 25℃; the refrigerant temperature resistor box to 15773Ω, corresponding to 15℃; and the evaporator temperature resistor box to 3444Ω, corresponding to 20℃.

[0076] Set different resistance values ​​for the water temperature resistance box: A resistance of 1374Ω corresponds to 35℃. If the difference between the target water temperature and the actual water temperature is greater than 41℃, the WPTC should be turned on at 100%, and the duty cycle of the WPTC feedback monitoring message should be 100%. A resistance of 964Ω corresponds to 45℃. With a temperature difference between 31℃ and 39℃, the WPTC should be turned on at 83%, and the monitoring duty cycle should be 83%. A resistance of 736Ω corresponds to 53℃. With a temperature difference between 26℃ and 29℃, the WPTC should be turned on at 67%, and the monitoring duty cycle should be 67%. A resistance of 625Ω corresponds to 58℃. When the temperature difference is between 21℃ and 24℃, the WPTC should be turned on at 50%, and the monitoring duty cycle should be 50%. A resistance of 502Ω corresponds to 65℃, with a temperature difference between 11℃ and 19℃. The WPTC should be turned on at 33%, and the monitoring duty cycle should be 33%. A resistance of 406Ω corresponds to 72℃. When the temperature difference is between 0℃ and 9℃, the WPTC should be turned on at 17%, and the monitoring duty cycle should be 17%. A resistance of 303Ω corresponds to 80℃, with a temperature difference of -2℃. WPTC should be turned off, and the monitoring duty cycle should be 0%.

[0077] Example 3: Sensor Fault Simulation Verification.

[0078] Based on normal operating conditions, perform the following fault simulation: Circuit break simulation: Disconnect the circuit breaker corresponding to the evaporating temperature resistance box. The TDU should report an evaporating temperature sensor circuit break fault, and ACRequestCommand should be changed to 0X0. The compressor should be prohibited from starting and enter the safety protection state.

[0079] Short circuit simulation: When the short circuit switch corresponding to the water temperature resistance box is closed, the TDU should identify the short circuit fault of the water temperature sensor, limit the maximum power of the WPTC or disable the WPTC to prevent overheating risk.

[0080] Drift simulation: A 1000Ω drift adjustment resistor is connected in series in the outdoor temperature resistance box circuit to make the actual resistance value larger than the corresponding value of 2409Ω at 30℃, and the equivalent temperature lower, to verify the TDU's rationality verification strategy for sensors.

[0081] This application's embodiments utilize a resistance box to replace actual temperature sensors and construct a complete closed-loop test bench, achieving thermal management function strategy verification without the need for a real vehicle, environmental chamber, or expensive specialized equipment. By using a fault simulation switch group, the test range is extended to three fault modes: open circuit, short circuit, and drift, ensuring thorough verification of the fault diagnosis strategy. A multi-sensor collaborative operating condition mapping table enables synchronous adjustment of five temperature signals, ensuring comprehensive verification of the control strategy under complex environmental boundary conditions.

[0082] Based on the same inventive concept, embodiments of this application also provide a fault simulation test system that uses a resistance box to simulate ambient temperature, comprising: The test bench deployment module is used to deploy the test bench, which is equipped with a thermal management controller, a CAN acquisition device, and a five-channel adjustable resistor box. The five-channel adjustable resistor box replaces the outdoor temperature sensor, indoor temperature sensor, evaporation temperature sensor, refrigerant temperature sensor, and water temperature sensor, respectively. The operating condition acquisition module is used to acquire the target test operating condition, which includes the target resistance value corresponding to each temperature sensor. The resistance adjustment module is used to adjust the resistance of each adjustable resistor box to the target resistance value, so that the resistance values ​​collected by the thermal management controller are equivalent to the output values ​​of the corresponding temperature sensors under the target test conditions. The message acquisition module is used to acquire control messages from the thermal management controller via a CAN acquisition device; The strategy verification module is used to compare the actual state of the control message with the preset control state corresponding to the target test condition, and output the fault simulation test result based on the comparison result.

[0083] Although this application has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some of the technical features; and these modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the spirit and scope of the technical solutions of the embodiments of this application.

Claims

1. A fault simulation test method using a resistance box to simulate ambient temperature, characterized in that, Includes the following steps: A test bench is deployed, which is equipped with a thermal management controller, a CAN acquisition device, and a five-channel adjustable resistor box. The five-channel adjustable resistor box replaces the outdoor temperature sensor, indoor temperature sensor, evaporation temperature sensor, refrigerant temperature sensor, and water temperature sensor, respectively. Obtain the target test conditions, which include the target resistance values ​​corresponding to each temperature sensor; Adjust the resistance values ​​of each adjustable resistor box to the target resistance value so that the resistance values ​​collected by the thermal management controller are equivalent to the output values ​​of the corresponding temperature sensors under the target test conditions. Control messages are acquired from the thermal management controller via a CAN acquisition device; The actual state of the control message is compared with the preset control state corresponding to the target test condition, and the fault simulation test result is output based on the comparison result.

2. The fault simulation test method using a resistance box to simulate ambient temperature according to claim 1, characterized in that, Before obtaining the target test conditions, the following is also included: Establish a resistance-temperature characteristic table for each temperature sensor, which records the nominal resistance of each temperature sensor at different temperatures. The target resistance value of each temperature sensor under the target test conditions is determined based on the resistance-temperature characteristic table.

3. The fault simulation test method using a resistance box to simulate ambient temperature according to claim 1, characterized in that, Before adjusting the resistance values ​​of each adjustable resistor box to the target resistance value, the following steps are also included: Establish a multi-sensor collaborative operating condition mapping table. The multi-sensor collaborative operating condition mapping table records the target resistance value combination of the five-channel adjustable resistor box and the corresponding preset control state for each test case. The target test conditions are determined based on the multi-sensor collaborative working condition mapping table, and the target resistance values ​​of the five-channel adjustable resistor boxes are extracted.

4. The fault simulation test method using a resistance box to simulate ambient temperature according to claim 1, characterized in that, Before acquiring control messages from the thermal management controller via the CAN acquisition device, the following is also included: Connect the five-channel adjustable resistor box to the original temperature sensor sampling circuit of the thermal management controller to determine the sensor sampling interface; A fault simulation switch group is added to the sensor sampling interface. The fault simulation switch group includes a circuit breaker, a short circuit switch and a drift adjustment resistor. Switch the state of the fault simulation switch group to perform open circuit simulation, short circuit simulation, or drift simulation to obtain the fault simulation temperature signal.

5. The fault simulation test method using a resistance box to simulate ambient temperature according to claim 4, characterized in that, A fault simulation switch group is added to the sensor sampling interface, including: A circuit breaker is connected in series between the output of the five-channel adjustable resistor box and the input of the sensor sampling interface. A short-circuit switch is connected in parallel across the five-way adjustable resistor box; A drift adjustment resistor is connected in series or parallel between the five-channel adjustable resistor box and the sensor sampling interface.

6. The fault simulation test method using a resistance box to simulate ambient temperature according to claim 4, characterized in that, Switch the state of the fault simulation switch group to perform open-circuit simulation, short-circuit simulation, or drift simulation to obtain the fault simulation temperature signal, including: Disconnect the circuit breaker to cut off the loop between the five-way adjustable resistor box and the sensor sampling interface. The thermal management controller detects the open circuit state and obtains the open circuit fault temperature signal. Read the open circuit fault code and limp control message output by the thermal management controller, compare the open circuit fault code with the open circuit fault identification strategy, and compare the limp control message with the protection shutdown strategy to obtain the open circuit strategy verification result. The open circuit fault temperature signal and the open circuit strategy verification results are incorporated into the fault simulation temperature signal.

7. The fault simulation test method using a resistance box to simulate ambient temperature according to claim 1, characterized in that, Switching the state of the fault simulation switch group to perform open-circuit simulation, short-circuit simulation, or drift simulation to obtain the fault simulation temperature signal, also includes: When the short-circuit switch is closed, the five-way adjustable resistor box is short-circuited. The thermal management controller detects the short-circuit state and obtains the short-circuit fault temperature signal. Read the short-circuit fault code and power limiting message output by the thermal management controller, compare the short-circuit fault code with the short-circuit fault identification strategy, and compare the power limiting message with the power limiting strategy to obtain the short-circuit strategy verification result. The short-circuit fault temperature signal and the short-circuit strategy verification results are incorporated into the fault simulation temperature signal.

8. The fault simulation test method using a resistance box to simulate ambient temperature according to claim 1, characterized in that, Switching the state of the fault simulation switch group to perform open-circuit simulation, short-circuit simulation, or drift simulation to obtain the fault simulation temperature signal, also includes: When the circuit breaker is closed and the short circuit breaker is open, the drift regulating resistor is connected in series or parallel to the main circuit. When the actual resistance value of the circuit deviates from the nominal value of the resistance temperature characteristic table, the thermal management controller detects the resistance drift state and obtains the drift fault temperature signal. Read the rationality verification message output by the thermal management controller, compare the rationality verification message with the drift fault identification strategy, compare the fault tolerance processing message with the fault tolerance processing strategy, and obtain the drift strategy verification result. The drift fault temperature signal and the drift strategy verification results are incorporated into the fault simulation temperature signal.

9. The fault simulation test method using a resistance box to simulate ambient temperature according to claim 1, characterized in that, The actual state of the control message is compared with the preset control state corresponding to the target test condition, including: The compressor request signal, fan duty cycle signal, water pump speed signal, and high-pressure heater power signal are parsed from the control message and used as a set of actual state parameters. Based on the target test conditions, extract the corresponding preset control states as the set of reference state parameters; The actual state parameter set is compared with the baseline state parameter set item by item to determine whether each actual state parameter meets the preset control state, and the comparison result is obtained.

10. The fault simulation test method using a resistance box to simulate ambient temperature according to claim 1, characterized in that, After outputting the fault simulation test results, the following is also included: The control message after the five adjustable resistor boxes are synchronously adjusted is compared with the control strategy specification corresponding to the target test condition. Verify the collaborative control logic of the compressor, cooling fan, water pump and high-pressure heater in a scenario of synchronous adjustment of five adjustable resistor boxes; The results of the collaborative control logic verification are included in the results of the fault simulation test.

11. A fault simulation test system that uses a resistance box to simulate ambient temperature, characterized in that, include: The test bench deployment module is used to deploy the test bench, which is equipped with a thermal management controller, a CAN acquisition device, and a five-channel adjustable resistor box. The five-channel adjustable resistor box replaces the outdoor temperature sensor, indoor temperature sensor, evaporation temperature sensor, refrigerant temperature sensor, and water temperature sensor, respectively. The operating condition acquisition module is used to acquire the target test operating condition, which includes the target resistance value corresponding to each temperature sensor. The resistance adjustment module is used to adjust the resistance of each adjustable resistor box to the target resistance value, so that the resistance values ​​collected by the thermal management controller are equivalent to the output values ​​of the corresponding temperature sensors under the target test conditions. The message acquisition module is used to acquire control messages from the thermal management controller via a CAN acquisition device; The strategy verification module is used to compare the actual state of the control message with the preset control state corresponding to the target test condition, and output the fault simulation test result based on the comparison result.

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