JP2021022387A - Computer simulation method - Google Patents

Abstract

To reproduce environment in which a plurality of portions of a wire harness network spread around a vehicle are simultaneously disturbed.SOLUTION: A vehicle has, for example, an electrical component connected by a wire harness and being verified to satisfy immunity characteristics in a standardized test method by a simulation method using a transmission line model that modeled the wire harness. The simulation method includes the steps of: modeling the wire harness as the transmission line model; setting a plurality of noise injection points to the transmission line model; and simultaneously injecting a noise signal into each of the noise injection points.SELECTED DRAWING: Figure 20

Description

The invention disclosed herein relates to a computer simulation method for evaluating immunity characteristics.

Conventionally, when designing a structure (vehicle, railroad, ship, aircraft, etc.) having a transmission line such as a conductive wire harness, or when designing various electrical components mounted on the structure, its immunity characteristics or emissions. In addition to actual measurement benchmarks, EMC [electro-magnetic compatibility] computer simulation is widely and generally used as a means for evaluating characteristics.

As an example of the prior art related to the above, in addition to Patent Document 1 by the applicant of the present application, Patent Document 2 and Non-Patent Document 1 can be mentioned.

JP-A-2015-75390 Japanese Unexamined Patent Publication No. 2013-242649

Hiroya Tanaka et al., "Simulation model of BCI (Bulk Current Injection) test system", technical research report. EMCJ, Environmental Electromagnetic Engineering, Institute of Electronics, Information and Communication Engineers, August 31, 2012, Vol. 112, No. 201, p. 47-50

However, in the conventional EMC computer simulation, the wire harness structure of the actual measurement benchmark with severe restrictions is modeled as it is. For example, if the total length of the wire harness is 1700 to 2000 mm and the injection points of EMC noise are set to 3 points (150 mm, 450 mm, 750 mm from the DUT) in the actual measurement benchmark, the wire of the EMC computer simulation The harness structure was also subject to the same restrictions as the actual measurement benchmark. Therefore, it is not possible to sufficiently cover the phenomena that may actually occur, and it is difficult to correctly evaluate the actual immunity characteristics or emission characteristics.

Further, in the conventional EMC computer simulation, the wire harness model is represented by a single characteristic impedance. Therefore, there was a considerable discrepancy between the measured value and the simulated value.

Further, in the conventional actual measurement benchmark and EMC computer simulation, the noise injection point for injecting the noise current is set to one place, and the noise current is injected independently from a specific point of the wire harness set in a simulated manner. .. However, for example, when a vehicle is exposed to a lightning strike, the entire wire harness network stretched around the vehicle is simultaneously disturbed. Therefore, the conventional actual measurement benchmark and EMC computer simulation with one noise injection point are merely a means for confirming partial characteristics, and are used to evaluate the immunity characteristics of the vehicle and the electrical components mounted on the vehicle. Although it was a necessary test, it was not a necessary and sufficient test.

In view of the above problems found by the inventor of the present application, the present specification proposes a computer simulation method capable of correctly evaluating immunity characteristics or emission characteristics. Further, in the present specification, a method for generating a transmission line model capable of reducing the discrepancy between the measured value and the simulated value is proposed. Further, in the present specification, a computer simulation method capable of reproducing an environment in which a plurality of transmission line networks are simultaneously disturbed is proposed.

In the computer simulation method disclosed in the present specification, the parameters of the transmission line model that models the transmission line to which the device under test is connected are set to variable values, and the immunity characteristics of the device under test are swept while sweeping the parameters. Alternatively, it is configured to evaluate the emission characteristics.

Further, the transmission line model generation method for computer simulation disclosed in the present specification classifies the transmission line to be modeled into at least two types, an end line and an intermediate line, according to the laying state thereof. The configuration includes a step and a step of individually modeling the end line and the intermediate line to generate an end line model and an intermediate line model.

Further, the computer simulation method disclosed in the present specification evaluates the immunity characteristics of the device under test by using a transmission line model that models the transmission line connected to the device under test. The configuration includes a step of setting a plurality of noise injection points into the transmission line and a step of simultaneously injecting a noise signal into each noise injection point.

The other features, elements, steps, advantages, and properties of the present invention will be further clarified by the following detailed description of the embodiments and the accompanying drawings relating thereto.

According to the computer simulation method disclosed in the present specification, it is possible to correctly evaluate the actual immunity characteristic or emission characteristic. Further, according to the transmission line model generation method disclosed in the present specification, it is possible to generate a transmission line model capable of reducing the discrepancy between the measured value and the simulation value. Further, according to the computer simulation method disclosed in the present specification, it is possible to reproduce an environment in which a plurality of transmission line networks are simultaneously disturbed.

Schematic diagram of the wire harness network stretched around the vehicle Block diagram showing an example of electrical component BCI test Block diagram showing an example of vehicle BCI test Block diagram showing an example of electrical component emission test Block diagram showing an example of a simulation model The figure which shows the comparative example of the malfunction voltage frequency characteristic and the reaching voltage frequency characteristic. Cross-sectional view schematically showing an example of laying a wire harness Frequency-gain diagram showing the laying position dependence of transmission characteristics Sectional view schematically showing a single line model Sectional view schematically showing the end line model Sectional view schematically showing an intermediate line model Measured waveform diagram of characteristic impedance (CPAVS0.75f) Measured waveform diagram of characteristic impedance (IV8mm ² LFV) A table showing the parameter values of the transmission line model Schematic diagram showing a description example of a transmission line model Frequency-characteristic impedance diagram showing an example of reproduction by simulation Schematic diagram showing an example of changing the description of the transmission line model (when adding noise injection points) Schematic diagram showing an example of changing the description of the transmission line model (when changing the noise injection position) Schematic diagram showing an example of changing the description of the transmission line model (when changing the wire laying state) Flow chart showing the old and new EMC evaluation methods in comparison Schematic diagram showing the parameter sweep range Schematic diagram showing the first example of multiple simultaneous injection models Schematic diagram showing a second example of multiple simultaneous injection models Schematic diagram showing how a vertical magnetic field is applied to a wire loop Schematic diagram showing a state in which a magnetic field in an oblique direction is applied to a wire loop.

<Wire harness net>
FIG. 1 is a schematic diagram (= vehicle skeleton diagram) of a wire harness network stretched around a vehicle. Vehicle X in recent years is equipped with a large number of electrical components (various lamps, various pumps, various fans, electronic suspensions, wipers, door locks, power windows, electric door mirrors, etc.), and these electrical components and battery X1 and A wire harness X3 for transmitting electric power and a signal is stretched in all directions between the ECU [electronic control unit] X2. In this way, the vehicle X equipped with a large number of electrical components is subject to various immunity tests and emission tests in order to enhance its safety and reliability.

In addition to vehicles, railroads, ships, aircraft, and the like can be mentioned as structures having a wire harness network.

<Electrical component BCI test (ISO11452-4)>
FIG. 2 is a block diagram showing a configuration example of the electrical component BCI test. The electrical component BCI test is a component test method (ISO11452-4) standardized by the International Organization for Standardization (ISO) for evaluating electrical interference caused by narrow-band electromagnetic radiant energy for in-vehicle electronic devices. It is one of the immunity tests that comply with.

More specifically in accordance with this figure, the electrical component BCI test is a noise source unit 20 and a detection unit 30 as an actual measurement benchmark for evaluating the immunity characteristics of the circuit unit 100 to be measured (or its simulated unit). , Controller 40, and injection probe 80.

The circuit unit 100 to be measured corresponds to an actual product (actual machine) on which the device under test 10 (hereinafter referred to as DUT [device under test] 10) is mounted. In addition to the DUT 10, the battery 50 and the power supply The filter unit 60 and the wire harness 70 are included. Further, the measurement target circuit unit 100 may include a pseudo load of the DUT 10.

The DUT 10 includes an LSI [large-scale integrated circuit] 11 and a printed wiring board (PCB [printed circuit board]) on which the LSI [large-scale integrated circuit] 11 is mounted. Of course, it is also possible to use the LSI 11 alone as the DUT 10. The DUT 10 does not necessarily have to be an actual device, and in general, a simulated device for testing is often used.

In particular, when performing mutual comparison of multiple LSIs (for example, mutual comparison between a new model LSI and an old model LSI, or mutual comparison between an in-house LSI and a compatible LSI of another company), components other than the LSI to be evaluated (for example, It is desirable to use a simulated device for testing in which the size and wiring pattern of the PCB, or the types and characteristics of discrete components mounted on the PCB are standardized.

The noise source unit 20 is a main body that injects a high-frequency noise signal (interference wave power) into the terminals of the DUT 10 (the power supply terminal VCS is illustrated in FIG. 2), and is a signal generator 21, an RF amplifier 22, and a bidirectional coupler. 23, a traveling wave side power sensor 24, a reflected wave side power sensor 25, a power meter 26, and a 50Ω transmission line 28 are included.

The signal generator (SG [signal generator]) 21 generates a sinusoidal high-frequency noise signal. The signal generator 21 may also modulate the high frequency noise signal as needed. The oscillation frequency, amplitude, and modulation of the high-frequency noise signal can all be controlled by the controller 40. When the disturbing wave is a pulse, a pulse generator (PG [pulse generator]) may be used, and when the disturbing wave is an impulse, an impulse generator (IG [impulse generator]) may be used.

The RF [radio frequency] amplifier 22 amplifies the high frequency noise signal generated by the signal generator 21 with a predetermined gain.

The bi-directional coupler (BDC) 23 separates the high-frequency noise signal amplified by the RF amplifier 22 into a traveling wave component toward the DUT 10 and a reflected wave component returning from the DUT 10.

The traveling wave side power sensor 24 measures the power of the traveling wave component separated by the bidirectional coupler 23. On the other hand, the reflected wave side power sensor 25 measures the power of the reflected wave component separated by the bidirectional coupler 23. It is desirable that each transmission line to the traveling wave side power sensor 24 and the reflected wave side power sensor 25 be in a pseudo cutoff state (for example, power passing characteristic: -20 dB or less).

The power meter 26 transmits the traveling wave power measured by the traveling wave side power sensor 24 and the reflected wave power measured by the reflected wave side power sensor 25 to the controller 40. The controller 40 calculates the power actually injected into the DUT 10 by performing the difference calculation between the traveling wave power and the reflected wave power, and records the calculation result. In this way, the power injected into the DUT 10 is measured by the power meter 26 at a position far away from the DUT 10. Therefore, in order to measure the injection power into the DUT 10 with high accuracy, it is desirable to grasp the cable characteristics at the time of high frequency noise signal transmission with high accuracy.

The detection unit 30 monitors the output waveform of the DUT 10 and sends the monitoring result to the controller 40. An oscilloscope or the like can be preferably used as the detection unit 30. Transmission from the DUT 10 to the detection unit 30 using a differential probe with high input impedance (1MΩ) and wide band (3GHz) so that the presence of the detection unit 30 does not affect the electrical component BCI test. It is desirable to put the line in a pseudo cutoff state.

The controller 40 is the main body that controls the electrical component BCI test in an integrated manner. When carrying out the electrical component BCI test, for example, the controller 40 signals so that the amplitude (injection power) of the high-frequency noise signal is gradually increased while the oscillation frequency of the high-frequency noise signal injected into the DUT 10 is fixed. Controls the generator 21. Further, in parallel with the above-mentioned amplitude control, the controller 40 determines the malfunction of the LSI 11 according to the monitoring result of the detection unit 30 (clock signal pulse omission, frequency disturbance, output voltage out-of-specification, communication error, etc.). Judgment as to whether or not it has occurred). Then, the controller 40 acquires the calculation result (injection power into the DUT 10) of the measured value of the power meter 26 at the time when the malfunction of the LSI 11 occurs, and stores this in association with the oscillation frequency currently being set. After that, the controller 40 repeats the above measurement while sweeping the oscillation frequency of the high-frequency noise signal to obtain the malfunction power frequency characteristic in which the oscillation frequency of the high-frequency noise signal and the injection power at the time of the malfunction occur. As the controller 40, a personal computer or the like capable of sequentially performing the above measurements can be preferably used.

The battery 50 is a DC power source that supplies power to the DUT 10. For example, when an in-vehicle LSI is to be evaluated, an in-vehicle battery may be used as the battery 50. However, the DC power supply to the DUT 10 is not limited to a battery, and an AC / DC converter or the like that generates a desired DC power from commercial AC power can also be used.

The power supply filter 60 is a circuit unit for setting the transmission line from the noise source unit 20 to the battery 50 in a pseudo cutoff state, and is a power supply impedance stabilization network 61 and 62 (hereinafter, LISN [line impedance stabilization network] 61 and 62). Includes). Both LISN 61 and 62 stabilize the apparent impedance of the battery 50. The LISN61 is inserted into the power supply line connecting the positive electrode terminal (+) of the battery 50 and the power supply terminal (VCC) of the DUT10, and the LISN62 is the negative electrode terminal (-) of the battery 50 and the GND terminal of the DUT10. It is inserted in the GND line connecting to (VEE).

The wire harness 70 is a conductive member having a length of about 1.5 to 2.0 m that electrically connects the DUT 10 and the power supply filter unit 60. The wire harness 70 may be a single wire, or may be a bundle of a plurality of wires. An injection probe (injection transformer) 80 is attached to the wire harness 70 at a predetermined position, and a bulk current is injected through the 50Ω transmission line 28 of the noise source unit 20.

In the electrical component BCI test, the total length of the wire harness 70 is defined as 1700 mm-2000 mm. Further, the mounting position of the injection probe 80 (= distance between the DUT 10 and the injection probe 80) is also limited to only three positions of 150 mm, 450 mm, and 750 mm.

<Vehicle BCI test (ISO11451-4)>
FIG. 3 is a block diagram showing an example of a vehicle BCI test. The vehicle BCI test is a BCI test conducted in a state where the above-mentioned DUT 10, wire harness 70, and the like are mounted on the vehicle X, and conforms to ISO11451-4.

<Emission test for electrical components (CISPR25)>
FIG. 4 is a block diagram showing an example of an electrical component emission test. The electrical component emission test in this figure is an actual measurement benchmark for evaluating the emission characteristics of electrical components. Value and measurement method ”. The electrical component emission test is divided into two types: radioactive emission measurement and conductive emission measurement. In the radioactive emission measurement, the intensity of noise radiated from the wire harness 70 is measured by the antenna 90. On the other hand, in the conductivity emission measurement, the intensity of noise transmitted through the wire harness 70 is measured by using the terminal 91 of the power supply filter 60 (not used in the immunity test). As described above, the electrical component emission test is different from the previous electrical component BCI test (FIG. 2) and vehicle BCI test (FIG. 3) in its configuration and purpose in that it measures the noise intensity. However, even in the electrical component emission test, the total length of the wire harness 70 is limited, and in that respect, there is no difference from the electrical component BCI test (FIG. 2).

<Simulation model>
FIG. 5 is a block diagram showing an example of a simulation model. The simulation model A of this configuration example is a model of the entire actual measurement benchmark (electrical component BCI test in FIG. 2), and includes a battery / LISN model A1, a DUT model A2, a BCI injection probe model A3, and a wire harness. It consists of a combination of model A4 and.

The battery / LISN model A1 is a model of the battery 50 and the power supply filter 60. When not only the battery 50 and the power filter 60 but also the control system is connected, the control system model may be added in parallel with the battery / LISN model A1.

The DUT model A2 is a model of the DUT 10. The DUT model A2 includes an LSI model that models the LSI 11, a PCB model that models the PCB, and an immunity behavior model that expresses these immunity behaviors.

The BCI injection probe model A3 is a model of the injection probe 80.

The wire harness model A4 is a model of the wire harness 70. In the wire harness model A4, as parameters for expressing the transmission characteristics, it corresponds to the parameter L according to the total length of the wire harness 70 and the distance between the DUT 10 and the injection probe 80 (= may be read as the noise injection position). The parameter Lx is included (details will be described later).

When modeling the wire harness structure of the electrical component BCI test as it is, regarding the above parameters L and Lx, the total length limit of the wire harness 70 (1700 to 2000 mm) and the position limit of the injection probe 80 (DUT 10 to 150 mm, The value will be limited so as to reflect the positions of 450 mm and 750 mm).

<Evaluation method of immunity characteristics>
FIG. 6 is a diagram showing a comparative example of the malfunction voltage frequency characteristic (solid line) and the ultimate voltage frequency characteristic (broken line).

The malfunction voltage frequency characteristic represents the magnitude of the high-frequency noise signal at the limit at which the LSI 11 malfunctions as a terminal voltage V_LSI that appears between predetermined points of the LSI 11. The malfunction voltage frequency characteristic is derived from the malfunction power frequency characteristic obtained by the DPI [direct power injection] test (= the magnitude of the high frequency noise signal at the limit where the DUT 10 causes a malfunction is expressed by the power injected into the DUT 10). Can be sought. On the other hand, the ultimate voltage frequency characteristic is a frequency characteristic of the ultimate voltage V_arr that appears between a predetermined point of the LSI 11 in the electrical component BCI test (or a computer simulation simulating the same).

The immunity characteristic of the LSI 11 can be evaluated by comparing the malfunction voltage frequency characteristic with the ultimate voltage frequency characteristic. For example, in FIG. 6, it can be determined that the LSI 11 may malfunction at an oscillation frequency in which the broken line exceeds the solid line. Further, by performing the same comparison as above for each terminal of the LSI 11, it is possible to identify the terminal that may cause a malfunction, so that the circuit design can be quickly improved.

In this figure, the evaluation method of immunity characteristics has been described by giving a comparative example between the malfunctioning voltage frequency characteristics and the reaching voltage frequency characteristics. For example, the malfunctioning current frequency characteristics (= high frequency noise at the limit where the LSI 11 causes a malfunction). Comparison of signal magnitude expressed by terminal current I_LSI flowing in a predetermined part of LSI 11) and reaching current frequency characteristics (= frequency characteristics of reaching current I_arr flowing after reaching a predetermined part of LSI 11 in the electrical component BCI test) It is also possible to evaluate the immunity characteristics of the LSI 11 by performing the above.

<Wire harness model>
Next, we propose a review of the wire harness simulation model used in the electrical component BCI test (Fig. 2) and electrical component emission test (Fig. 4). In particular, this proposal relates to modeling common mode impedance in wire harnesses. More specifically, in the following, it is possible to standardize the wire laying method when bundling a plurality of wires to form a wire harness, and to perform high-speed processing corresponding to the actual wire harness structure. We propose a transmission line model.

FIG. 7 is a cross-sectional view schematically showing an example of laying a wire harness. In the example of this figure, the wire harness wh is a bundle of five wires w1 to w5. The wires w1 to w5 are characterized in that they are laid horizontally so that their respective coating films are in contact with each other. All the wires w1 to w5 are laid at a predetermined distance (for example, 50 mm) from the ground plane (for example, a copper plate on a table). Such a laying state is referred to as "parallel laying" in the present specification. When the number of wires laid increases, the number of adjacent wires shall be increased in the horizontal direction.

In the example of this figure, the hatched wires w1 and w5 correspond to the end lines, and the white wires w2 to w4 correspond to the intermediate lines. The end line refers to a plurality of wires laid in parallel in a state in which no other wire is adjacent to at least one side thereof. On the other hand, the intermediate line refers to a state in which other wires are adjacent to each other on both sides thereof. The number of parallel wires laid may be any number.

Further, the transmission characteristic of the wire harness is determined by the presence of a GND (ground plane or the like) facing the wire harness. Regarding the relative positions of the wire harness and GND, the closest position is adjacent and the farthest position is infinity. In the following, the difference in transmission characteristics between the end line and the intermediate line (= the laying position dependence of the transmission characteristics) will be described in detail.

FIG. 8 is a frequency-gain diagram showing that the transmission characteristics of the wires w1 to w5 have laying position dependence. The actual measurement results in this figure show that the first ends of the five wires w1 to w5 laid in parallel are short-circuited with each other, and the second end of each is a 250Ω terminating structure, while the measurement target. It was obtained in an actual measurement environment in which the terminating resistor of only the wire was replaced with a 200Ω resistor in series. Further, as a matter of course, as the wires w1 to w5, those having substantially the same impedance in terms of DC are used.

For example, when comparing the transmission characteristics of wire w1 (solid line) and the transmission characteristics of wire w2 (small broken line), there is a difference in each transmission characteristic in the frequency band of 40 MHz to 100 MHz, and in particular, 6 dB at 61 MHz. You can see the difference (about 4 times) (see the thick arrow in the figure). This difference indicates that when the wire harness wh receives interference noise, the interference energy does not propagate uniformly to the wires w1 and w2.

On the other hand, no significant difference in the above frequency band is observed between the transmission characteristic of the wire w1 (solid line) and the transmission characteristic of the wire w5 (dashed-dotted line). Further, no significant difference in the above frequency band is observed between the transmission characteristics of the wire w2 (small dashed line), the transmission characteristics of the wire w3 (large dashed line), and the transmission characteristics of the wire w4 (dashed line). ..

From the above-mentioned actual measurement results, the inventor of the present application pays attention to the fact that the characteristic impedance of the wires w1 to w5 laid in parallel shows a tendency according to each laying state (adjacent state), and at least ends the wires w1 to w5. It has been found that it can be classified into two types, a department line group (w1 and w5) and an intermediate line group (w2 to w4).

For the sake of simplification, the conventional wire harness model is uniformly expressed as having a single characteristic impedance, ignoring the interaction between adjacent wires. Therefore, in the conventional wire harness model, the same current and voltage are generated for all the wires w1 to w5 having the same termination conditions, so that it is not possible to express the difference according to each laying state. Further, since there is no reflection in the lumped constant, it is not possible to express a standing wave depending on the total length of the wire harness wh.

On the other hand, by classifying the wire harness wh into at least two types, the end line group (w1 and w5) and the intermediate line group (w2 to w4), the conventional wire harness model having a single characteristic impedance and the lumped constant can be used. It is possible to reproduce transmission characteristics that could not be expressed.

<Model classification>
9A to 9C are cross-sectional views schematically showing a wire harness, and the hatched wires in each figure are a single wire model (FIG. 9A), an end line model (FIG. 9B), and Each is modeled as an intermediate line model (FIG. 9C). The bottom of each figure corresponds to the ground plane.

The single wire model (FIG. 9A) is a model of a wire (that is, a single wire) having no other wires on both sides thereof. As described above, the single line model (FIG. 9A) does not correspond to the case where a plurality of wires are laid in parallel, but here, the end line model (FIG. 9B) and the intermediate line model are used as the basic units of the transmission line model. This will be described together with (FIG. 9C). The single-line model (FIG. 9A) can also be understood as a special example of the end-line model (FIG. 9B).

The white arrows in each figure indicate typical electric lines of force. As can be seen by comparing and referring to each figure, since the electric field distribution of each differs depending on the laying state of the wire, three types of characteristic impedances (single line model, end line model, and intermediate line model) are mixed. In each figure, two types of wire types (CPAVS 0.75f and IV8 mm ² LFV) are taken as an example, and two types of characteristic impedance Z0 are shown for each model.

In the case of the single wire model (FIG. 9A), Z0 = 300Ω in CPAVS0.75f and Z0 = 207Ω in IV8mm ² LFV. In the case of the end line model (FIG. 9B), Z0 = 520Ω in CPAVS 0.75f and Z0 = 364Ω in IV8mm ² LFV. In the case of the intermediate line model (FIG. 9C), Z0 = 2600Ω in CPAVS 0.75f and Z0 = 2400Ω in IV8mm ² LFV.

As described above, it can be seen that the numerical value of the characteristic impedance Z0 differs by about an order of magnitude between the single line model (FIG. 9A) and the end line model (FIG. 9B) and the intermediate line model (FIG. 9C).

FIG. 10 is an actually measured waveform diagram acquired when deriving the characteristic impedance of CPAVS 0.75f. Regarding the laying state of the wire harnesses wh11 to wh15 used for the actual measurement of the characteristic impedance, as shown in the legend, wh11 (solid line) is a single line, wh12 (small broken line) is two parallel laying lines, and wh13 (large broken line). ) Is 5 parallel laying lines, wh14 (dashed line) is 2 parallel laying lines (however, the distance between wires is 100 mm), and wh15 (dashed line) is 3 lines laid in parallel (however, the distance between wires is 50 mm).

As a characteristic impedance measurement method, TDR [time domain reflectometry] is used, the measuring instrument is Agilent 8510C (with built-in Fourier [inverse fast fourier transform]), the measurement band is 45 MHz to 18.045 GHz, the number of measurement points is 401, and the measurement range. Was set to -1ns to 15ns. In addition, when measuring the characteristic impedance, both ends of each wire were short-circuited, and the characteristic impedance was acquired as the common mode impedance of the straight portion of the wire harness.

The actual measurement result of the wire harness wh11 (solid line) was Z0 = 300Ω. The wire harness wh11 can be understood as a single wire itself. Therefore, the characteristic impedance of the single wire model may be set to "300Ω" (see FIG. 9A).

The actual measurement result of the wire harness wh12 (small broken line) was Z0 = 260Ω. The wire harness wh12 can be understood as having two end wires laid in parallel. Therefore, the characteristic impedance of the end line model may be set to "520Ω (= 260Ω × 2)" (see FIG. 9B).

The actual measurement result of the wire harness wh13 (large broken line) was Z0 = 200Ω. The wire harness wh13 can be understood as having two end lines and three intermediate lines laid in parallel. Therefore, when the characteristic impedance of the intermediate line model is R, the following equation (1) holds.

1/200 = 2/520 + 3 / R ... (1)

By solving this equation (1), the characteristic impedance of the intermediate line model can be obtained as "2600Ω" (see FIG. 9C).

The actual measurement result of the wire harness wh14 (dashed line) was Z0 = 150Ω, and the actual measurement result of the wire harness wh15 (dashed line) was Z0 = 120Ω. From the comparison between these actual measurement results and the actual measurement results (Z0 = 300Ω) of the wire harness wh11 (solid line), it can be seen that when the distance between the wires is 100 mm or more, each wire laid in parallel exhibits the same transmission characteristics as a single wire. confirmed.

In addition, a delay time of 4.72 ns / 770 mm was confirmed in all actual measurements of the wire harnesses wh11 to wh15. From this, the unit delay time per unit length (1 m) can be calculated as "6.13 ns / m".

FIG. 11 is an actually measured waveform diagram acquired when deriving the characteristic impedance of IV8 mm ² LFV. Regarding the laying state of the wire harnesses wh21 to wh24 used for the actual measurement of the characteristic impedance, as shown in the legend, wh21 (solid line) is a single line, wh22 (small broken line) is two parallel laying lines, and wh23 (large broken line). ) Is 5 parallel laying lines, and wh24 (dashed line) is 2 parallel laying lines (however, the distance between wires is 100 mm). The characteristic impedance measurement method, measuring instrument, measurement band, number of measurement points, and measurement range are the same as those in FIG. 10 above.

The actual measurement result of the wire harness wh21 (solid line) was Z0 = 207Ω. The wire harness wh21 can be understood as a single wire itself. Therefore, the characteristic impedance of the single wire model may be set to "207Ω" (see FIG. 9A).

The actual measurement result of the wire harness wh22 (small broken line) was Z0 = 182Ω. The wire harness wh22 can be understood as having two end wires laid in parallel. Therefore, the characteristic impedance of the end line model may be set to "364Ω (= 182Ω × 2)" (see FIG. 9B).

The actual measurement result of the wire harness wh23 (large broken line) was Z0 = 149Ω. The wire harness wh23 can be understood as having two end lines and three intermediate lines laid in parallel. Therefore, when the characteristic impedance of the intermediate line model is R, the following equation (2) holds.

1/149 = 2/364 + 3 / R ... (2)

By solving this equation (2), the characteristic impedance of the intermediate line model can be obtained as "2400Ω" (see FIG. 9C).

The actual measurement result of the wire harness wh24 (dashed line) was Z0 = 145Ω. From the comparison between this actual measurement result and the actual measurement result (Z0 = 207Ω) of the wire harness wh21 (solid line), it was confirmed that even if the distance between the wires is 100 mm or more, there is interference between the wires laid in parallel. It was.

In addition, a delay time of 5.36 ns / 880 mm was confirmed in the actual measurements of the wire harnesses wh21 to wh24. From this, the unit delay time per unit length (1 m) can be calculated as "6.09 ns / m".

<Transmission line model>
Based on the above measurement results, we propose a wire transmission line model (for example, SPICE model). FIG. 12 is a table showing the parameter values of the transmission line model, and shows the wire type (CPAVS0.75f / IV8mm ² LFV), model classification (single line model / end line model / intermediate line model), characteristic impedance, and unit. The delay time is shown.

As the wire type (= type of transmission line), CPAVS0.75f was exemplified as the low-voltage transmission line (signal line), and IV8 mm ² LFV was exemplified as the high-voltage transmission line (power supply line). Wires may be modeled.

In the single wire model of CPAVS 0.75f, the characteristic impedance is set to Z0 = 300 [Ω], and the unit delay time is set to TD = 6.13 [ns / m]. In the end line model of CPAVS 0.75f, the characteristic impedance is set to Z0 = 520 [Ω], and the unit delay time is set to TD = 6.13 [ns / m]. In the intermediate line model of CPAVS 0.75f, the characteristic impedance is set to Z0 = 2600 [Ω], and the unit delay time is set to TD = 6.13 [ns / m].

On the other hand, in the IV8 mm ² LFV single wire model, the characteristic impedance is set to Z0 = 207 [Ω], and the unit delay time is set to TD = 6.09 [ns / m]. In the IV8 mm ² LFV end line model, the characteristic impedance is set to Z0 = 364 [Ω] and the unit delay time is set to TD = 6.09 [ns / m]. In the IV8 mm ² LFV midline model, the characteristic impedance is set to Z0 = 2400 [Ω] and the unit delay time is set to TD = 6.09 [ns / m].

In this way, the characteristic impedance of each model is set to a different value according to the model classification of the wire (single line model, end line model, intermediate line model). In particular, focusing on the end line model and the intermediate line model, the characteristic impedance of the end line model is set to a value about an order of magnitude lower than the characteristic impedance of the intermediate line model. On the other hand, the unit delay time of each model is set to the same value regardless of the model classification of the wire. Further, the above-mentioned characteristic impedance and unit delay time are set individually for each wire type.

FIG. 13 is a schematic diagram showing a description example of the transmission line model. In the example of this figure, the wire harness wh is obtained by laying five wires w1 to w5 in parallel, and the total length thereof is L [m]. Regarding the wire type, it is assumed that the wires w1 and w2 are CPAVS0.75f and the wires w3 to w5 are IV8 mm ² LFV.

On the other hand, when paying attention to the laid state of the wires w1 to w5, the wires w1 and w5 are classified as end lines, and the wires w2 to w4 are classified as intermediate lines. Therefore, the wire harness wh can be appropriately expressed by combining the end line model and the intermediate line model.

Regarding the description format of the transmission line model, the wire number (name), the first port connection destination of the inner conductor c1, the first port connection destination of the outer conductor c2, the second port connection destination of the inner conductor c1, and the outer conductor c2. It is assumed that each parameter is described in the order of the second port connection destination, the characteristic impedance Z0, and the delay time TD (= unit delay time × total length).

For example, when the description "w1 ND1 GPLANE ND2 GPLANE Z0 = 300 TD = 6 × L" in the first line of the upper row in the blowout is read, "the wire w1 has the first port connection destination of the internal conductor c1 connected to the node ND1. The first port connection destination of the outer conductor c2 is the ground plane, the second port connection destination of the inner conductor c1 is the node ND2, the second port connection destination of the outer conductor c2 is the ground plane, and the characteristic impedance Z0. Is 300 [Ω], and the delay time TD is 6 × L [ns]. ”

A conventional transmission line model in which the wires w1 to w5 are represented by a single characteristic impedance (Z0 = 300 [Ω]) is described in the upper part of the balloon. On the other hand, in the lower part of the blowout, a new transmission line model in which the wires w1 to w5 are represented by different characteristic impedances according to the laying state is described.

More specifically, the wire w1 is modeled as an end line model of CPAVS0.75f (Z0 = 520 [Ω], TD = 6.13 × L [ns]). The wire w2 is modeled as an intermediate line model of CPAVS 0.75f (Z0 = 2600 [Ω], TD = 6.13 × L [ns]). Both wires w3 and w4 are modeled as an IV8 mm ² LFV midline model (Z0 = 2400 [Ω], TD = 6.09 × L [ns]). The wire w5 is modeled as an IV8 mm ² LFV end line model (Z0 = 364 [Ω], TD = 6.09 × L [ns]).

As described above, the new transmission line model proposed in this section is a step of classifying the wires to be modeled into two types (or three types including a single line) according to the laying state. , A step of individually modeling two types of end line and intermediate line (or three types including single line) to generate two types of end line model and intermediate line model (or three types including single line model). It is generated via ,.

Unlike the conventional transmission line model, such a transmission line model can faithfully reproduce the difference in transmission characteristics (see FIG. 8) according to the laying state of the wire, so that the actual measurement value and the simulation value can be reproduced. It is possible to reduce the deviation from.

Further, the transmission line model proposed in this section includes the characteristic impedance Z0 and the delay time TD as parameters expressing the transmission characteristics, and in this respect, it is no different from the conventional transmission line model (Fig.). Refer to the comparison between the upper row and the lower row in the 13 blowouts). Therefore, there is no significant effect on the preparation time and execution time of the EMC computer simulation.

The method of expressing the transmission line model is roughly divided into a case where loss is taken into consideration (= with loss) and a case where loss is ignored (= no loss). In the former case, there are various ways to express loss. The total length of the wire harness used in the above-mentioned electrical component BCI test (Fig. 2) and electrical component emission test (Fig. 4) is about 2 m, and the total length is about 10 m even when mounting on a vehicle is taken into consideration. is there. In view of this, it can be said that it is desirable to appropriately use the transmission line model with loss and the transmission line model without loss as necessary. The characteristic impedance and unit delay time described above are numerical examples without loss.

FIG. 14 is a frequency-characteristic impedance diagram showing an example of reproduction confirmation by transmission line simulation. The solid line in this figure shows the simulation value (when the loss is taken into consideration), and the broken line shows the measured value. From this figure, it can be seen that the behavior of the solid line and the behavior of the broken line match accurately. For example, in a transmission line model that takes into account the power that is converted to heat and the power that is lost by radiation, it is possible to calculate the amount of radiation.

<Application to vehicle body test>
In the previous BCI test for electrical components (Fig. 2), one of a wide variety of wire harness structures (there are as many types as there are vehicles) is fixed and one structure is fixed to ensure its practical implementation. The noise injection points were limited to three discrete points.

However, the total length of the wire harness laid in the actual vehicle varies from 100 mm to 5000 mm, and the number of wires varies from 1 to 60. Therefore, it is undeniable that in the electrical component BCI test, there are a huge number of unpredictable phenomena and many oversights.

On the other hand, in this section, the parameters of the transmission line model that models the wire harness (for example, characteristic impedance, delay time, and number of laying lines) are set to variable values, and these parameters are swept within a predetermined range. We propose a computer simulation method for evaluating the immunity or emission characteristics of a DUT.

First, in the following, we will explain how the description content of the transmission line model changes, citing some specific examples of parameter changes.

FIG. 15 is a schematic diagram showing how the description content of the transmission line model should be changed when the number of noise injection points is increased from one to two.

As shown in the upper part of this figure, at one place of the wire W (total length: L) laid between the signal node SIG1 and the signal node SIG2 (the point where the wire W is divided into two in the example of this figure). When the noise injection point INJ1 is attached, the part laid between the signal node SIG1 and the noise injection point INJ1 is understood as the dividing wire W1 (length: L / 2), and the noise injection point INJ1 and By understanding the portion laid between the signal node SIG2 and the split wire W2 (length: L / 2), for example, the transmission line model can be described as follows.

W1 SIG1 GPLANE INJ1 GPLANE Z0 = 300 TD = 6
W2 INJ1 GPLANE SIG2 GPLANE Z0 = 300 TD = 6

On the other hand, as shown in the lower part of this figure, when noise injection points INJ1 and INJ2 are attached to two places of the wire W (the point that divides the wire W into three equal parts in the example of this figure), the signal node. The part laid between the SIG1 and the noise injection point INJ1 is understood as the split wire W3 (length: L / 3), and the part laid between the noise injection point INJ1 and the noise injection point INJ2 is the split wire. By understanding it as W4 (length: L / 3) and understanding the portion laid between the noise injection point INJ2 and the signal node SIG2 as the dividing wire W5 (length: L / 3), for example, The transmission line model can be described as follows.

W3 SIG1 GPLANE INJ1 GPLANE Z0 = 300 TD = 4
W4 INJ1 GPLANE INJ2 GPLANE Z0 = 300 TD = 4
W5 INJ2 GPLANE SIG2 GPLANE Z0 = 300 TD = 4

As described above, when the number of noise injection points is increased, the number of wire divisions increases, and the number of lines described in the transmission line model may be appropriately increased accordingly. Further, when the noise injection point is added, the length of the dividing wire changes, so that the delay time TD of the transmission line model may be appropriately rewritten accordingly.

FIG. 16 is a schematic diagram showing how the description content of the transmission line model should be changed when the noise injection position is changed.

In the upper part of this figure, as in the upper part of FIG. 15, the noise injection point INJ1 is attached at a point that bisects the wire W (total length: L) laid between the signal node SIG1 and the signal node SIG2. .. Therefore, the transmission line model can be described as follows.

W1 SIG1 GPLANE INJ1 GPLANE Z0 = 300 TD = 6
W2 INJ1 GPLANE SIG2 GPLANE Z0 = 300 TD = 6

On the other hand, in the lower part of this figure, the noise injection point INJ1 is not a point that divides the wire W into two equal parts, but one of the points that divides the wire W into three equal parts (in the example of this figure, the length of the divided wire W1 is L). It becomes / 3, and it is attached to the point where the length of the dividing wire W2 becomes 2L / 3). Therefore, the transmission line model can be described as follows.

W1 SIG1 GPLANE INJ1 GPLANE Z0 = 300 TD = 4
W2 INJ1 GPLANE SIG2 GPLANE Z0 = 300 TD = 8

As described above, when the noise injection position is changed, the length of the dividing wire changes. Therefore, the delay time TD of the transmission line model may be appropriately rewritten accordingly. Further, although not shown again, it goes without saying that the change in the total length of the wire can be dealt with by rewriting the delay time TD.

FIG. 17 is a schematic diagram showing how the description content of the transmission line model should be changed when the wire laying state is changed.

In the upper part of this figure, as in FIG. 13, five wires w1 to w5 (total length: L) are laid in parallel between the node ND1 and the node ND2. Regarding the wire type, the wires w1 and w2 are CPAVS0.75f, and the wires w3 to w5 are IV8 mm ² LFV. Further, the wires w1 and w5 are classified as end lines, and the wires w2 to w4 are classified as intermediate lines. Therefore, the transmission line model can be described as follows.

w1 ND1 GPLANE ND2 GPLANE Z0 = 520 TD = 6.13xL
w2 ND1 GPLANE ND2 GPLANE Z0 = 2600 TD = 6.13xL
w3 ND1 GPLANE ND2 GPLANE Z0 = 2400 TD = 6.09xL
w4 ND1 GPLANE ND2 GPLANE Z0 = 2400 TD = 6.09xL
w5 ND1 GPLANE ND2 GPLANE Z0 = 364 TD = 6.09xL

On the other hand, in the lower part of this figure, the wire w3 is changed from IV8 mm ² LFV to CPAVS 0.75f. Further, the wire w5 is changed from an end line to an intermediate line. Further, a wire w6 (CPAVS0.75f) is separately added as a new end line. At this time, the description content of the transmission line model may be changed as follows.

w1 ND1 GPLANE ND2 GPLANE Z0 = 520 TD = 6.13xL
w2 ND1 GPLANE ND2 GPLANE Z0 = 2600 TD = 6.13xL
w3 ND1 GPLANE ND2 GPLANE Z0 = 2600 TD = 6.13xL
w4 ND1 GPLANE ND2 GPLANE Z0 = 2400 TD = 6.09xL
w5 ND1 GPLANE ND2 GPLANE Z0 = 2400 TD = 6.09xL
w6 ND1 GPLANE ND2 GPLANE Z0 = 520 TD = 6.13xL

The changed parts of the above description contents will be described. First, regarding the wire w3, the characteristic impedance Z0 of the wire w3 is changed from "2400" to "2600" and the delay time TD of the wire w3 is increased due to the change of the wire type (IV8 mm ² LFV → CPAVS0.75f). It has been changed from "6.09 x L" to "6.13 x L". Further, regarding the wire w5, the characteristic impedance Z0 of the wire w5 is changed from "364" to "2400" due to the change of the model classification (end line → intermediate line). Further, with the addition of the wire w6, one line of description of the wire w6 is added. The description content of the wire w6 is the same as the description content of the wire w1.

In this way, by appropriately changing the parameters of the transmission line model (for example, characteristic impedance, delay time, and number of laying lines), it is possible to easily represent the actual measurement environment structure of various electrical components, and further, the vehicle. It is possible to reproduce the wire harness structure laid in. Therefore, it becomes possible to sufficiently cover the phenomena that may actually occur by computer simulation without being bound by the restrictions of the actual measurement benchmark.

FIG. 18 is a flowchart showing the old and new EMC evaluation methods in comparison with each other. The left frame of this figure shows the work flow of a general EMC evaluation method. On the other hand, the right frame of this figure shows the work flow of the new EMC evaluation method proposed in this section.

As shown in the left frame of this figure, in the general EMC evaluation method, first, in step S11, the wire harness structure for each vehicle is described. This wire harness structure is obtained by analyzing the wire harness network actually stretched around the vehicle at a three-dimensional level and describing the structure contents in detail based on the analysis result.

Next, in step S12, an electromagnetic field simulation is carried out using the above wire harness structure, and in subsequent step S13, a fixed transmission line circuit model is generated for each vehicle. However, as a matter of course, there is a restriction that only one transmission line circuit model can be generated for each electromagnetic field simulation in step S12.

After that, in step S14, EMC evaluation (= evaluation of immunity characteristic or emission characteristic) of the electrical component is performed by computer simulation using the above transmission line circuit model. However, as described above, the above transmission line circuit model can be generated only once for each electromagnetic field simulation. Therefore, if you want to perform EMC evaluation of electrical components using multiple types of transmission line circuit models, perform the electromagnetic field simulation in step S12 while changing the conditions for each type of transmission line circuit model (= number of fixed shapes). Need to repeat.

However, it takes at least several tens of hours to carry out one electromagnetic field simulation, and when the simulation accuracy is improved, the required time may reach several hundred hours. Therefore, for example, in order to cover all the condition changes (addition of noise injection points, change of noise injection position, change of wire total length, change of wire laying state) illustrated in FIGS. 15 to 17 above. It takes hundreds to thousands of hours to generate various types of transmission line circuit models, so it is not a realistic method.

As described above, the EMC evaluation flow in the left frame of this figure is premised on the identification of the vehicle in the first place, so its versatility is by no means high. Therefore, it is not suitable for EMC evaluation of electrical components mounted on unspecified vehicles and computer simulation assuming changes in the wire harness structure that occur during actual running of the vehicle.

On the other hand, as shown in the right frame of this figure, in the new EMC evaluation method proposed in this section, first, the characteristic impedance of the wire harness is measured in step S21. This characteristic impedance measurement may be performed for each wire type (for example, CPAVS 0.75f and IV8mm ² LFV). Since the specific contents of this step have already been described with reference to FIGS. 10 and 11, duplicate explanations will be omitted. The characteristic impedance of the wire harness may be acquired by a unit length electromagnetic field simulation.

Next, in step S22, model classification (end line, intermediate line, and single line) is performed on the plurality of wires forming the wire harness. Similar to the above-mentioned characteristic impedance measurement, this model classification may be performed for each wire type. Since the specific contents of this step have already been described in FIGS. 9A to 9C and FIG. 12, duplicate explanations will be omitted.

After that, in step S23, a variable transmission line circuit model is generated by appropriately combining a plurality of subdivided transmission line models and various elements (DUT model, LISN model, battery model, etc.) connected thereto. Will be done. That is, the transmission line circuit model generated in this step includes parameters related to the noise injection position and the wire laying state (and the wire harness structure itself), and by making these values variable values. , A wide variety of test conditions can be reproduced.

Based on this, in the following step S24, EMC evaluation of electrical components is performed while appropriately sweeping various parameters (for example, characteristic impedance, delay time, and number of laying lines) by computer simulation using the above transmission line circuit model. Is done. That is, in this step, a wide variety of test conditions (= wire harness structure) can be reproduced by changing various parameters without repeating the electromagnetic field simulation (see step S12) that requires a long time. .. Therefore, it is possible to perform screening under the worst conditions extremely efficiently in a short time.

As described above, the old and new EMC evaluation methods differ greatly in whether or not the work of changing the test conditions is rate-determined by the electromagnetic field simulation. In other words, with the new EMC evaluation method proposed in this section, test conditions can be continuously set independently of the electromagnetic field simulation by parameterizing a wide variety of vehicle structures without forcibly consolidating them into one. Can be changed. Therefore, since the degree of freedom in setting the test conditions can be increased, it is possible to evaluate the immunity characteristics or the emission characteristics of the electrical components more correctly than in the past.

<Parameter sweep range>
FIG. 19 is a schematic diagram showing a sweep range of various parameters (characteristic impedance, wire total length, noise injection position, and number of wires) in step S24.

The characteristic impedance Z0 is swept so as to reproduce the laying state change or type change of the wire. As for the fluctuation of the wire laying state, in addition to the above-mentioned model classification (end line model, intermediate line model, and single line model), the wire misalignment (running vibration, aging, temperature change, or , Changes in the relative distance between the wire and the ground plane due to changes in humidity, etc.), changes in the vehicle type (body structure), changes in the body material, and other state changes that can affect the characteristic impedance of the wire can be included.

The sweep range of the characteristic impedance Z0 may be set to (300-α) Ω ≦ Z0 ≦ (300 + β) Ω so as to include a value (for example, 300Ω) subject to the same restrictions as the actual measurement benchmark. Further, the sweep range of the wire total length L and the noise injection position Lx may be set so as to include the values subject to the same restrictions as the actual measurement benchmark. For example, the sweep range of the wire total length L may be set to 100 mm ≦ L ≦ 5000 mm in consideration of the wire laying length considered in the actual machine while including 1500 mm to 1700 mm. Further, for example, the sweep range of the noise injection position Lx may be set to 0 mm ≦ Lx ≦ L mm so as to include 150 mm, 450 mm, and 750 mm.

If the characteristic impedance Z0, the total wire length L, and the sweep range of the noise injection position Lx are set as described above, the simulation result can be verified (= collation between the simulation result and the measured result) using the conventional measured benchmark. It becomes possible to do.

When sweeping the wire total length L and the noise injection position Lx, the delay time TD is swept so as to reproduce this.

Further, the sweep range of the number of wires N may be set to 1 ≦ N ≦ 60 in consideration of the actual wire harness.

In the above, an example of setting the sweep range of various parameters based on the actual measurement benchmark is given, but the setting method is not limited to this, and for example, the structure description of the transmission line circuit in the actual machine (FIG. 18). The sweep range of various parameters may be set so as to include the value obtained in step S11) of.

With such a setting, it is possible to perform a computer simulation that faithfully reflects various conditions that may occur in an actual vehicle. Therefore, for example, in the conventional EMC evaluation method (left frame in FIG. 18), an event that was overlooked no matter how long it took (for example, an unintended immunity characteristic or emission characteristic caused by a displacement of the wire due to running vibration). It is possible to evaluate even this (variation in) without overlooking it.

<Multiple simultaneous injection models>
As mentioned in the background technology section, when the actual vehicle is disturbed by EMC from the outside (for example, when the vehicle is exposed to a lightning strike), the wire harness network stretched around the vehicle (see FIG. 1). ) The whole is disturbed at the same time. At this time, interference of different strength occurs for each wire harness, or interference occurs in a group of wire harnesses connected in series. Therefore, in order to reproduce the actual EMC interference, it is necessary to simultaneously apply interference to a plurality of affected wire harnesses.

However, in order to set multiple noise injection points in the conventional EMC test, it is necessary to prepare as many EMC test facilities (such as class A amplifiers of several kW class) for each unit as the number of noise injection points. However, it was unrealistic considering the cost.

Therefore, in the conventional actual measurement benchmark (for example, the electrical component BCI test in FIG. 2 or the vehicle BCI test in FIG. 3), a noise signal is injected into one place of the wire harness connected to the DUT, and the other parts. Was ignored at the same time. As described above, in the conventional actual measurement benchmark, the DUT is independently tested, which is one of the reasons why the EMC interference that occurs in an actual vehicle cannot be reproduced.

Further, as described above, in the conventional computer simulation, it is necessary to analyze the wire harness network of the vehicle at the three-dimensional level and perform the electromagnetic field simulation (see the left side of FIG. 18). This electromagnetic field simulation is an extremely high-load arithmetic processing, and even if the noise injection point is narrowed down to one place, the processing time is several tens of hours to several hundreds of hours. Therefore, it is unrealistic to reproduce multiple simultaneous injections of noise signals using a conventional computer simulation from the viewpoint of processing time (processing capacity).

The following is based on the new computer simulation method described so far (= a method for evaluating the immunity characteristics of the device under test using a transmission line model that models the transmission line connected to the device under test). We propose the construction of a simulation model that can reproduce an environment in which multiple transmission line networks are being disturbed at the same time at low cost and in a reasonable processing time.

FIG. 20 is a schematic diagram showing a first example of a plurality of simultaneous injection models. The structure to be modeled is schematically depicted in the upper part of this figure. On the other hand, the conventional one-point injection model is depicted in the middle part of this figure, and the first example of the multiple simultaneous injection models proposed this time is depicted in the lower part of this figure.

The structure in the upper part of this figure includes three devices under test DUT1 to DUT3 and two independent wires W10 and W20. The wire W10 is a transmission line connecting the device under test DUT1 and the device under test DUT2, and is laid between the two devices without bending. On the other hand, the wire W20 is a transmission line connecting the device under test DUT2 and the device under test DUT3, and is laid between the two devices without bending. In the upper part of this figure, the devices under test DUT1 to DUT3 are provided in a straight line, but the layout of the devices is not limited to this. It can also be understood as injecting a noise current into the ground plane (= body) of the wire W10 or W20 or both. It is also possible to understand by replacing each of the wires W10 and W20 with a wire harness (= bundle of a plurality of wires).

When the structure is disturbed by EMC from the outside (for example, when the vehicle is exposed to a lightning strike), both the wires W10 and W20 are disturbed at the same time. In the upper part of this figure, one point of the wire W10 (the distance from the device under test DUT1 is L11 and the distance from the device under test DUT2 is L12) and one point of the wire W20 (the distance from the device under test DUT2) are At L21, the distance from the device under test DUT3 is L22), both of which are simultaneously disturbed.

In modeling the above structure, in the conventional one-point injection model (middle part of this figure), the noise injection point INJ10 is provided only on the wire W10, and the state in which the wire W20 is simultaneously disturbed is ignored. (See dashed line).

On the other hand, in the multiple simultaneous injection model proposed this time (lower part of this figure), noise injection points INJ10 and INJ20 are set for each of the wires W10 and W20, and noise signals are simultaneously injected into each of them.

Regarding the setting of the noise injection point INJ10, the portion of the wire W10 (total length: L11 + L12) laid between the device under test DUT1 and the noise injection point INJ10 is set as the split wire W11 (length: L11) and noise. The portion laid between the injection point INJ10 and the device under test DUT2 may be understood as the split wire W12 (length: L12).

Similarly, regarding the setting of the noise injection point INJ20, the portion of the wire W20 (total length: L21 + L22) laid between the device under test DUT2 and the noise injection point INJ20 is divided into the wire W21 (length: L21). Then, the portion laid between the noise injection point INJ20 and the device under test DUT3 may be understood as the split wire W22 (length: L22).

Further, regarding the transmission line models in which the divided wires W11 and W12 and the divided wires W21 and W22 are modeled, respectively, as described above, the characteristic impedance Z0 and the delay time are used as parameters expressing the transmission characteristics. It may include TD.

The characteristic impedance Z0 may be set according to the laying state or type of the divided wires W11 and W12 and the divided wires W21 and W22, respectively. For example, the transmission line model may be classified into at least two types, an end line model and an intermediate line model, according to the laying state of the wires W10 and W20, and the characteristic impedance Z0 of each may be set to a different value. ..

The delay time TD is set according to the total length or type of the wire W10, or the positions of the noise injection points INJ10 and INJ20 (= the lengths of the split wires W11 and W12, and the lengths of the split wires W21 and W22). do it.

Further, among the devices DUT1 to DUT3 to be tested, in particular, the device DUT2 to be tested to which both the wires W10 and W20 are connected includes a first port to which the wire W10 is connected and a second port to which the wire W20 is connected. It is advisable to describe the S-parameters for two ports as an equivalent circuit.

As described above, in the multiple simultaneous injection model proposed this time, the transmission line network to be evaluated is tentatively determined by describing the wires W10 and W20 as a transmission line model and connecting the respective coupling portions with an equivalent circuit. Has been done. Further, noise injection points INJ10 and INJ20 are set in the wires W10 and W20, respectively, and noise signals are simultaneously injected into the noise injection points INJ10 and INJ20 when the computer simulation is executed.

By using such a method, an environment in which multiple transmission line networks are simultaneously disturbed can be reproduced inexpensively and in a reasonable processing time without requiring expensive EMC test equipment or high-load electromagnetic field simulation. be able to. Therefore, for example, it is possible to correctly evaluate the EMC interference that occurs in an actual vehicle and optimize the laying structure of the wire harness network.

In addition, due to the structure of the vehicle, there are restrictions on the laying length and laying route of the wire harness, so one of the conditions is that a group of wire harnesses stretched around the vehicle are simultaneously disturbed. Wire harnesses (= wire harnesses that should be modeled) can be extracted. Therefore, it is possible to carry out a computer simulation without applying an excessive calculation load.

For the noise signals injected into the noise injection points INJ10 and INJ20, respectively, the parameters (current amount (= intensity), frequency, waveform, etc.) are set to variable values, and the parameters are adjusted or swept while being subject to noise signals. The immunity characteristics of the test devices DUT1 and DUT2 may be evaluated. By adopting such an evaluation method, it is possible to pseudo-set the magnetic fields applied to the wires W10 and W20 from various angles.

For example, by making the waveform of the noise signal an impulse instead of a sine wave and appropriately changing the current amount of the noise signal injected into the noise injection points INJ10 and INJ20, from various angles with respect to the vehicle exposed to lightning. It is possible to correctly verify the influence of the applied magnetic field. In the following, we propose a method for evaluating the effects of natural phenomena such as lightning, citing the second example of multiple simultaneous injection models.

FIG. 21 is a schematic view showing a second example of a plurality of simultaneous injection models. The structure to be modeled is schematically depicted in the upper part of this figure, and the second example of the multiple simultaneous injection model proposed this time is depicted in the lower part of this figure.

The structure in the upper part of this figure includes two devices under test, DUT1 and DUT2, and two independent wires W30 and W40. The wire W30 is a transmission line connecting the device under test DUT1 and the device under test DUT2, and is laid so as to bend 90 ° at the node n1 between the two devices. On the other hand, the wire W40 is also a transmission line connecting the device under test DUT1 and the device under test DUT2, and is laid so as to bend 90 ° at the node n2 between the two devices.

As described above, in the upper part of this figure, as the simplest structure for evaluating the influence of a natural phenomenon such as lightning, a rectangular loop structure formed by wires W30 and W40 (hereinafter referred to as a wire loop). Is depicted.

In the upper part of this figure, the wires W30 and W40 are each bent by 90 °, but the angle is not limited to this. It can also be understood as injecting a noise current into the ground plane (= body) of the wire W30 or W40 or both. It is also possible to understand by replacing each of the wires W10 and W20 with a wire harness (= bundle of a plurality of wires).

When the structure is disturbed by EMC from the outside (for example, when the vehicle is exposed to a lightning strike), both the wires W30 and W40 are disturbed at the same time. Since the wire W30 is bent at the node n1 and the laying direction is different between the portion corresponding to the upper side and the portion corresponding to the right side of the wire loop, there is a difference in how to receive EMC interference. The same applies to the wire W40 as described above, and there is a difference in the way EMC interference is received between the portion corresponding to the lower side and the portion corresponding to the left side of the wire loop.

In view of this, in the upper part of this figure, two points on the wire W30 (one point where the distance from the device under test DUT1 is L31 and the distance from the node n1 is L32 on the upper side of the wire loop, and the node on the right side of the wire loop. One point where the distance from n1 is L33 and the distance from the device under test DUT2 is L34) and two points on the wire W40 (the distance from the device under test DUT2 at the bottom of the wire loop is L41 and the distance from the node n2). At one point where is L42 and at the left side of the wire loop, the distance from the node n2 is L43 and the distance from the device under test DUT3 is L44), the state of being disturbed at the same time is described.

When modeling the above structure, in the multiple simultaneous injection models (lower part of this figure) proposed this time, two noise injection points INJ31 and INJ32, and noise injection points INJ41 and INJ42 are set for each of the wires W30 and W40. A noise signal is injected into each of them at the same time.

Regarding the setting of the noise injection points INJ31 and INJ32, the portion of the wire W30 (total length: L31 + L32 + L33 + L34) laid between the device under test DUT1 and the noise injection point INJ31 is set as the split wire W31 (length: L31). The portion laid from the noise injection point INJ31 to the noise injection point INJ32 via the node n1 is defined as a split wire W32 (length: L32 + L33), and the portion laid between the noise injection point INJ32 and the device under test DUT2. Can be understood as a split wire W33 (length: L34).

Further, as in the above, regarding the setting of the noise injection points INJ41 and INJ42, the portion of the wire W40 (total length: L41 + L42 + L43 + L44) laid between the device under test DUT2 and the noise injection point INJ41 is divided into the split wire W41 ( The length is L41), and the portion laid from the noise injection point INJ41 to the noise injection point INJ42 via the node n2 is set as the dividing wire W42 (length: L42 + L43), and between the noise injection point INJ42 and the device under test DUT1. The portion laid in the above may be understood as a split wire W43 (length: L44).

In this way, if multiple noise injection points are set for one wire, the length of the split wire and the parameters of the noise signal can be changed without changing the description content of the transmission line model itself. It is possible to express a bent state (bending position, bending direction, etc.). Therefore, since the transmission line network in various laid states can be freely modeled, for example, even when the strength of the interfering wave depends on the structure of the vehicle, it is possible to appropriately deal with it.

FIG. 22 is a schematic view showing a state in which a magnetic field B in the vertical direction is applied to the opening of the wire loop shown in FIG. 21 (= a state in which the effective cross-sectional area of the wire loop is maximum). A schematic view (XY plan view) of the wire loop of FIG. 21 as viewed from the Z-axis direction is drawn on the left side of this figure. Further, on the right side of this figure, a schematic view (YZ plan view) of the wire loop of FIG. 21 as viewed from the X-axis direction is drawn.

On the other hand, FIG. 23 shows a state in which a magnetic field B in an oblique direction is applied to the opening of the wire loop in FIG. 21 (= the wire loop is tilted in the Z-axis direction and the effective cross-sectional area is smaller than that in FIG. 22. ) Is a schematic diagram. A schematic view (XY plan view) of the wire loop of FIG. 21 as viewed from the Z-axis direction is drawn on the left side of this figure. Further, on the right side of this figure, a schematic view (YZ plan view) of the wire loop of FIG. 21 as viewed from the X-axis direction is drawn.

Regarding the difference between FIGS. 22 and 23, it may be understood that the wire loop is rotated while the magnetic field B in a certain direction is applied, and conversely, it is fixed. It may be understood that the application direction of the magnetic field B is rotated with respect to the wire loop.

As can be seen by comparing both figures, the intensity of the noise signal injected into the upper and lower sides of the wire loop (= equivalent to the number of magnetic field lines penetrating the wire provided with the noise injection points INJ31 and INJ41) is the magnetic field B. It is constant regardless of the application direction. On the other hand, the intensity of the noise signal injected into the left and right sides of the wire loop (= equivalent to the number of magnetic lines of force penetrating the wire provided with the noise injection points INJ32 and INJ42) becomes smaller as the effective cross-sectional area of the wire loop decreases. Become.

In view of the above, for example, if the noise intensities of the noise injection points INJ31 and INJ41 are maintained and the noise intensities of the noise injection points INJ32 and INJ42 are lowered, the situation where the wire loop is tilted in the Z-axis direction can be reproduced. it can. Similarly, by appropriately adjusting the noise intensity at each noise injection point, it is possible to arbitrarily reproduce the situation in which the magnetic field B is applied to the wire loop from any direction.

In addition, the noise intensity at each noise injection point also indicates that the induced currents generated on the upper and lower sides of the wire loop, or the induced currents generated on the left and right sides of the wire loop, strengthen or weaken each other. Can be freely expressed by appropriately adjusting.

In this way, by adopting the second example (Fig. 21) of the multiple simultaneous injection model and appropriately adjusting the position, path, intensity, frequency, and waveform of the interference received by the wire harness, it does not actually occur. Even for natural phenomena (lightning strikes, etc.) for which the interference conditions cannot be determined, the effect of this on the structure (vehicles, etc.) can be evaluated correctly. Therefore, by reflecting the evaluation result in the pre-design, it is possible to contribute to the improvement of reliability.

<Other variants>
In addition to the above-described embodiment, various technical features disclosed in the present specification can be modified in various ways without departing from the spirit of the technical creation. That is, it should be considered that the above-described embodiment is exemplary in all respects and is not restrictive, and the technical scope of the present invention is shown not by the description of the above-mentioned embodiment but by the scope of claims. It should be understood that it includes all changes that fall within the meaning and scope of the claims.

The invention disclosed herein can be used, for example, in EMC computer simulation for evaluating the immunity or emission characteristics of a structure having a conductive wire harness (vehicle, railroad, ship, aircraft, etc.). Is possible.

10 Device under test (DUT)
11 LSI
20 Noise source 21 Signal generator 22 RF amplifier 23 Bidirectional coupler 24 Traveling wave side power sensor 25 Reflected wave side power sensor 26 Power meter 28 50Ω Transmission line 30 Detection part (oscillator, etc.)
40 controller (personal computer, etc.)
50 Battery 60 Power Filter 61, 62 Power Impedance Stabilization Network (LISN)
70 Wire harness 80 Injection probe 90 Antenna 91 Terminal 100 Measurement target circuit unit A Simulation model A1 Battery / LISN model A2 DUT model A3 BCI injection probe model A4 Wire harness model (transmission line model)
B magnetic field wh, wh11 to wh15, wh21 to wh24 wire harness w1 to w6, W, W10, W20, W30, W40 wire W1 to W5, W11, W12, W21, W22, W31 to W33, W41 to W43 split wire DUT1, DUT2, DUT3 Device under test SIG1, SIG2 Signal node INJ1, INJ2, INJ10, INJ20, INJ31, INJ32, INJ41, INJ42 Noise injection point c1 Internal conductor c2 External conductor X Vehicle X1 Battery X2 ECU
X3 wire harness

Claims (10)

A vehicle that has electrical components connected by a wire harness and has been verified to satisfy the immunity characteristics of a standardized test method by a simulation method using a transmission line model that models the wire harness.
The simulation method is
A step of modeling the wire harness as the transmission line model,
The step of setting a plurality of noise injection points into the transmission line model and
The step of injecting a noise signal to each noise injection point at the same time,
Has a vehicle. The vehicle according to claim 1, wherein at least one noise injection point is set for each of the plurality of wire harnesses. The vehicle according to claim 1 or 2, wherein a plurality of the noise injection points are set in one wire harness. The vehicle according to any one of claims 1 to 3, wherein the electrical component to which a plurality of wire harnesses are connected is described as an equivalent circuit including a plurality of ports. The vehicle according to any one of claims 1 to 4, wherein a loop structure is formed by the wire harness. The vehicle according to any one of claims 1 to 5, wherein the parameter of the noise signal is set to a variable value, and the immunity characteristic of the electrical component is evaluated while sweeping the parameter. The vehicle according to any one of claims 1 to 6, wherein the transmission line model includes a characteristic impedance and a delay time as parameters representing the transmission characteristics. The vehicle according to claim 7, wherein the delay time is set according to the total length or type of the wire harness or the position of the noise injection point. The vehicle according to claim 7 or 8, wherein the characteristic impedance is set according to the laying state or type of the wire harness. The transmission line model is classified into at least two types, an end line model and an intermediate line model, according to the laying state of the wire harness, and the characteristic impedances of the respective transmission line models are set to different values. The vehicle according to any one of claims 9.

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