New method for estimating the grounding reliability test of aircraft cable shield
We investigated a new method based on electromagnetic induction technique is proposed for reliability test of the grounding connection, and a test setup is built for experiment. As proven by the experimental results, the proposed method can provide a wide measurement rang and sufficiently high accur...
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| Cite this: | New method for estimating the grounding reliability test of aircraft cable shield / Hongxu Zhao, Geng Zhang, Yongyun Wang, Qian Wang // Functional Materials. — 2017. — Т. 24, № 1. — С. 184-189. — Бібліогр.: 10 назв. — англ. |
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Hongxu Zhao Geng Zhang Yongyun Wang Qian Wang 2018-06-16T15:04:23Z 2018-06-16T15:04:23Z 2017 New method for estimating the grounding reliability test of aircraft cable shield / Hongxu Zhao, Geng Zhang, Yongyun Wang, Qian Wang // Functional Materials. — 2017. — Т. 24, № 1. — С. 184-189. — Бібліогр.: 10 назв. — англ. 1027-5495 DOI: https://doi.org/10.15407/fm24.01.184 https://nasplib.isofts.kiev.ua/handle/123456789/136679 We investigated a new method based on electromagnetic induction technique is proposed for reliability test of the grounding connection, and a test setup is built for experiment. As proven by the experimental results, the proposed method can provide a wide measurement rang and sufficiently high accuracy, to measure the loop resistance and joint resistance. en НТК «Інститут монокристалів» НАН України Functional Materials Devices and instruments New method for estimating the grounding reliability test of aircraft cable shield Article published earlier |
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New method for estimating the grounding reliability test of aircraft cable shield Hongxu Zhao Geng Zhang Yongyun Wang Qian Wang Devices and instruments |
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new method for estimating the grounding reliability test of aircraft cable shield |
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Hongxu Zhao Geng Zhang Yongyun Wang Qian Wang |
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Hongxu Zhao Geng Zhang Yongyun Wang Qian Wang |
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We investigated a new method based on electromagnetic induction technique is proposed for reliability test of the grounding connection, and a test setup is built for experiment. As proven by the experimental results, the proposed method can provide a wide measurement rang and sufficiently high accuracy, to measure the loop resistance and joint resistance.
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New method for estimating the grounding reliability test of aircraft cable shield / Hongxu Zhao, Geng Zhang, Yongyun Wang, Qian Wang // Functional Materials. — 2017. — Т. 24, № 1. — С. 184-189. — Бібліогр.: 10 назв. — англ. |
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AT hongxuzhao newmethodforestimatingthegroundingreliabilitytestofaircraftcableshield AT gengzhang newmethodforestimatingthegroundingreliabilitytestofaircraftcableshield AT yongyunwang newmethodforestimatingthegroundingreliabilitytestofaircraftcableshield AT qianwang newmethodforestimatingthegroundingreliabilitytestofaircraftcableshield |
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2025-11-26T15:24:59Z |
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2025-11-26T15:24:59Z |
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184 Functional materials, 24, 1, 2017
ISSN 1027-5495. Functional Materials, 24, No.1 (2017), p. 184-189
doi:https://doi.org/10.15407/fm24.01.184 © 2017 — STC “Institute for Single Crystals”
New method for estimating the grounding
reliability test of aircraft cable shield
Hongxu Zhao1, Geng Zhang1, Yongyun Wang1, Qian Wang2
1Department of Electronic Information and Automation, Civil Aviation
University of China, Tianjin 300300, China
2Department of Flight Techniques, Civil Aviation University of China,
Tianjin 300300, China
Received November 30, 2016
We investigated a new method based on electromagnetic induction technique is proposed for
reliability test of the grounding connection, and a test setup is built for experiment. As proven
by the experimental results, the proposed method can provide a wide measurement rang and
sufficiently high accuracy, to measure the loop resistance and joint resistance.
Keywords: cable shield; grounding reliability; electromagnetic induction; loop resistance;
joint resistance; shielding effectiveness
Предложен новый метод для оценки надежности заземления бортовой аппаратуры лета-
тельных аппаратов, основанный на измерении электромагнитной индукции. По сравнению
с традиционным методом, данный метод не требует отсоединения кабельных жгутов. Созда-
на испытательная установка для проверки точности измерений такого метода. Результаты
измерений показали достоверность данного метода. Диапазон измерений [1m�, ���� m��,m�, ���� m��,, ���� m��,m��,�,
относительная ошибка меньше чем 5%.
Новий метод оцінки надійності заземлення авіаційних кабельних джгутів.
Хунгху Чжао, Ген Чжан, Юнгун Ван, Цянь Ван
Запропоновано новий метод для оцінки надійності заземлення бортової апаратури лі-
тальних апаратів, заснований на вимірюванні електромагнітної індукції. У порівнянні з
традиційним методом, даний метод не вимагає від’єднання кабельних джгутів. Створено-
випробувальну установку для перевірки точності вимірювань такого методу. Результати
вимірювань показали достовірність даного методу. Діапазон вимірювань [1m�, ���� m��,
відносна помилка менше ніж 5%.
I. Introduction
Fly by wire flight control system is widely
used on the modern airplanes to promote the
integration of all kinds of avionics systems. As
the main carrier of the information exchange,
the avionics data bus plays an important role
in ensuring the reliability and integrity of the
transmitted data. But unpredictable condi-
tions, such as lightning and HIRF challenges
the quality of the data transmission in the
way of electromagnetic interference [1, 2�.The
protection from such complex electromagnetic
interference is to ground both the ends of the
cable shield to the airframe, in such way the
cable shield, airframe and the connector in
between builds a conductive loop, which circu-
lates the electrical currents generated by the
lightning or HIRF to the ground without affect-
ing internal transmitting data. The reliability
of the grounding connection depends heavily on
the resistance of the shield it self, any defect
Functional materials, 24, 1, 2017 185
Hongxu Zhao et al. / New method for estimating the grounding ...
on the shield larges its resistance and further
affect the grounding reliability. In addition, the
reliability of the grounding connection maybe
suffered from the poor installation of the con-
nector as well, since the joint resistance of the
connector is also part of loop resistance [3-5�.
The traditional method to test cable shield
has an inevitable drawback that, the shielded
cable has to be disassembled from the airframe
first, and then the shield can be tested by any
accurate resistance-measuring instrument
as the way how regular resistor is tested. Al-
though such method provides very good accu-
racy in measuring the resistance of the shield
itself, but due to the fact that the cable need to
be re-installed after the test, wherein poor in-
stallation might happen, which could turn into
an unacceptable joint resistance. As explained
above, joint resistance is part of the shield loop
resistance, so with an improperjoint resistance
the shielding effectiveness
declines even if the shield itself is ideal [6,
7�. Based on the voltage-current vector method,
using electromagnetic induction technique, a
new method is proposed to test the loop resis-
tance of the shield, with this method the shield
can be tested “online”, which means it is not
necessary to disassemble the cable anymore.
2. Algorithm of test method
As shown in Fig.1, the cable shield, air-
frame and two connectors constitute the shield
loop. A drive coupler is used to drive particular
loop voltage on the shield, meanwhile another
sense coupler collects the information of the
loop current. At the end, the voltage-current
vector method is applied to calculate the loop
resistance. Assuming the airframe is in perfect
condition, it has negligible resistance, which
means the calculated loop resistance can be
considered approximatively as the sum of the
shield resistance and the joint resistance. With
this assumption, as long as the measured loop
resistance is lower than the constrain, both of
the shield and the connection are safe. If the
loop resistance exceeds the constrain, it indi-
cates a fault occurs either on the shield or the
connection, or even both of them. In order to
locate the fault, two probes are used to detect
the voltage across the connector, and voltage-
current vector method is applied again to solve
the joint resistance. Further based on the loop
resistance and joint resistance, the fault can be
found easily.
In order to induce particular loop voltage on
the shield loop, an AC voltage signal UD(t) is
put on the drive coupler. This signal can be de-
scribed by Eq. (1), where the amplitude A is 5V,
the frequency f is 2��Hz, and the initial phase
is � degree.
U t A ftD ( ) sin( )= +2π θ (1)
While the two couplers are clamped on the
shield, induced loop voltage UL(t) and loop cur-
rent IL(t) occurs on the shield loop, where the
subscript L stands for loop. Since the frequency
of the signals is only 2��Hz, so these two sig-
nals can be easily captured by an acquisition
module at 5�KHz.
After sampling, the continuous signals UL(t)
and IL(t) turn into two sets of discrete signals
UL(k) and IL(k), which are shown as following,
U k
U U U U n k n
L
L L L L
( )
( ), ( ), ( ), , ( ) ,
=
= { } £ £1 2 3 1
(2)
I k
I I I I n k n
L
L L L L
( )
( ), ( ), ( ), , ( ) ,
=
= { } £ £1 2 3 1
(3)
Afterwards, the Fast Fourier Transform is
performed on the two discrete signals separate-
ly, while the size N of the process window is set
to 5���. The solution of the FFT calculation for
each signal is set of complex numbers, and each
complex number corresponds to one frequency
component, which is shown as the following
equations,
U K U k
U K jU K K N
LF L
LFR LFX
( ) FFT( ( ))
( ) ( ),
= =
= + £ £1
(�)
I K I k
I K jI K K N
LF L
LFR LFX
( ) FFT( ( ))
( ) ( ),
= =
= + £ £1
(5)
The subscript F appears in above equations
stands for FFT, and R stands for real part of the
complex number where X stands for imaginary
part. According to Eq. (6), the index K of the
complex number that corresponds to 2��Hzcan
be calculated.
f
K
N
fK s=
-( )1 (6)
When fK is 2��Hz, N is 5��� and fS is 5�KHz,
the K equals to 21. So the loop impedance ZL of
the shield can be calculated by following equa-
tion,
Fig. 1. Test Environment
186 Functional materials, 24, 1, 2017
Hongxu Zhao et al. / New method for estimating the grounding ...
Z
U
I
U jU
I jI
LF
LF
LFR LFX
LFR LFX
L = =
+
+
( )
( )
( ) ( )
( ) ( )
21
21
21 21
21 21
(7)
The calculated loop impedance is also a com-
plex number, and the real part is the loop resis-
tance RL, as shown in the following equation,
R Z
U I U I
I
L
LFR LFR LFX LFX
LFR
L
2
= RE( ) =
=
+
+
( ) ( ) ( ) ( )
( )
21 21 21 21
21 IILFX ( )21 2
(8)
The procedure of the resistance calculation
is shown in Fig.2.
3. Architeture of test setup
The block diagram of the entire system is
shown in Fig.3. It mainly consists of four parts,
which are human machine interface, control
platform, auxiliary circuit and test tools. The
human machine interface provides the opera-
tor with a graphical user interface for monitor-
ing the system’s state and setting operating
parameters. The control platform comprises
one processing unit and two analog I/O mod-
ules. The processing unit is responsible for logi-
cal control, data processing and I/O modules
configuration. According to the functionality of
each I/O modules, they are named generation
module and acquisition module respectively.
Two types of test tools are employed, the
couplers are used for loop resistance measure-
ment, and the probes are used for joint resis-
tance measurement. Ideally, the output signal
of the test tools should be fed to the acquisition
module directly, but the range of the output sig-
nal is too wide and additionally the sampling
accuracy is necessarily to be high as well, so the
acquisition module is not capable to process the
signal directly. For this reason, an auxiliary
circuit is designed to process the signal before
the control platform starts to sample.
A.Control Platform
The block diagram of the control platform is
shown in Fig.�. It is built based on NI product
cRIO-9�75 integrated system, which combines
a real-time processor and a reconfigurable
FPGA within the same chassis. The real time
processor can provide precise timing and stabil-
ity, so it is used for logical control and data log-
ging. The FPGA communicates with real time
processor by PCI bus, but it connects to the I/O
modules directly rather than any kinds of bus,
and it is used to configure, drive and synchro-
nize all the connected I/O modules. One of the
used I/O module is a 2�-bit analog input mod-
ule with ±1�V simultaneous sampling range
and 5�kS/s sampling rate. The other one is a
1��kS/s analog output module, which has ±1�V
range and 16-bit resolution.
B.Test Tools
The two couplers are identical in structure
but different in functionalities. Both of them
have two coils and one magnetic core inside,
as shown in Fig.5. For each coupler, the two
coils have different number of turns for differ-
ent purposes, one of them is 1��� turns and the
other is 1� turns. During the measurement, the
two couplers are clamped on the shield loop, as
Fig. 2. Resistance calculation procedure
Fig. 3. Block diagram of test setup
Functional materials, 24, 1, 2017 187
Hongxu Zhao et al. / New method for estimating the grounding ...
a consequence the 1��� turns coil and the mag-
netic core of the drive coupler and the shield
loop forms a structure as transformer. Since
the shield loop only has one turn, so if the driv-
ing voltage UD is applied on the 1��� turns coil,
consequently there should be a 1��� times less
loop voltage UL induced on the shield loop.
Similarly, the 1��� turns coil and the mag-
netic core of the sense coupler and the shield
loop forms another transformer structure,
which turns ratio is 1:1���.Consequently, the
current ratio between output current IS and
loop current IL is inversely proportional to the
turns ratio. At the end, assuming both of the
coupler are fully closed and there is no flux
leakage, then the loop impedance ZL can be cal-
culated as the following equation,
Z
U
I
U
I
L
L
L
D
S
= =
´
´
1
1000
1000
1
(9)
When either of the couplers is not fully
closed, there will be flux leakage flow out of the
magnetic core, so that the voltage ratio and cur-
rent ratio will not be as same as the turns ratio
any more, which possibly cause a measurement
error at the end. In order to provide protection
from such problem, inside the coupler there is
another 1� turns coil as introduced above. Ide-
ally, the output voltage US of this extra coil
should be 1�� times less than the UD because of
the turns ration. Therefore, whenever the mea-
sured US deviates from the theoretical value, it
proves the coupler is not fully closed [8�.
The probes are used for joint impedance mea-
surement, but the two couplers are necessarily
to be clamped on the shield as well during the
measurement. One of the probe touches the ca-
ble connector while the other probe touches the
airframe, the difference from the two probes is
the joint voltage UJ, and the joint impedance is
calculated as Eq. (1�),
Z
U
I
U
I
J
J
L
J
S
= =
´
1000
1
(1�)
C. Auxiliary Circuit
As introduced in the beginning of the paper,
an auxiliary circuit is designed to pre-process
the output signals IS and UJ of the test tools.
More specifically, the auxiliary circuit com-
prises three sub-circuits, which are trans-im-
pedance amplifier circuit, instrument amplifier
circuit and differential amplifier circuit.
The trans-impedance amplifier circuit is
used to convert the output current IS to volt-
age signal UT, since the acquisition module is
not capable to process current signal, as shown
in the Fig.6. If the gain AT of the amplifier is
set too high, while measuring low resistance
shielding loop, the value of UT may exceed the
sampling range of the acquisition module. If
the gain AT is set too low, while measuring high
resistance shielding loop, the UT may be inac-
curate because of the sampling resolution of
acquisition module [9�. Considering both con-
strains, the gain AT is set to 1��� at the end.
The joint voltage UJ is a differential signal,
it is processed by an instrument amplifier circuit
firstly, instead of going to the acquisition module
directly. Within the instrument amplifier circuit,
the differential signal is converted to single ended
signal. The gain AD is set to 1�� to satisfy the ac-
quisition capability of the hardware.
Fig. �. Block diagram of control platform
Fig. 5. Working principle of the test tools
Fig. 6. Block diagram of auxiliary circuit
188 Functional materials, 24, 1, 2017
Hongxu Zhao et al. / New method for estimating the grounding ...
Considering the fact that there is huge
amount of cables next to each other closely on
the airplane, sometimes it is not easy to reach
the testing point using the probes through all
the cables. Hence, it is possible to have a fake
contact of the probes and testing point, which
definitely leads to a failure measurement. In
order to avoid the occurrence of such case, a
modified differential amplifier circuit is de-
signed. A three-resistor ladder is put in front
of the differential amplifier, and all three resis-
tors have a big value in resistance. The most
important resistor R2 is in parallel with the
joint. Ideally, the resistance of the joint is much
lower than R2, so depends on the contact of the
probes and testing points, the voltage across R2
could be very different [1��. In such way, bad
contact from the probes can be warned before
the measurement runs.
4. Exeperiment and result
As shown in Fig.7, four standard loop resis-
tors and five joint resistors have been used for
verification experiment, and all the resistor has
been calibrated right before the experiment.
Each resistor has been measured for 1�
times, and test results for loop resistance and
joint resistance are listed in Table 1 and Ta-
ble 2, respectively.
In table I and table II, the subscript L indi-
cates loop resistor and J indicates joint resis-
tor. Comparing to the nominal value of each
resistor, it can be concluded that the test setup
is able to measure the loop resistance and joint
resistance very accurately. In order to further
evaluate the accuracy of this test setup, the rel-
ative error for each measurement is calculated
as Eq. (11),
Table 1. Measurement result of the loop resistance
Nominal/m� Test1/m� Test2/m� Test3/m� Test�/m� Test5/m�
RL1 2.��7 2.�35 2.�3� 2.�33 2.�33 2.�32
RL2 8.5�1 8.�96 8.5�7 8.5�5 8.5�6 8.5�2
RL3 1�.1�� 13.916 13.921 13.892 13.897 13.918
RL� 3659 366� 367� 366� 366� 366�
Table 2. Measurement result of the joint resistance
Nominal/m� Test1/m� Test2/m� Test3/m� Test�/m� Test5/m�
RJ1 �.5�� �.5�9 �.5�6 �.5�6 �.5�6 �.5�8
RJ2 �.997 5.�61 5.�56 5.�5�5 5.�52 5.�57
RJ3 25.�1� 25.�6� 25.292 25.27� 25.285 25.28�
RJ� 5�.��� 5�.��5 5�.�1� 5�.�33 5�.�3� 5�.�3�
RJ5 36�3 362� 367� 368� 3615 362�
Fig. 7. Standard loop resistors and joint resis-
tors
δ=
-R R
R
M N
N
(11)
In Eq.11, the δ stands for relative error, RM
stands for the mean value of the 5 test results
for each resistor, RN stands for the nominal
value for each resistor. The relative errors are
listed in Table 3.
Table 3. Relative error of loop resistance and
joint resistance
Loop δ/% Joint δ/%
RL1 �.7�% RJ1 1.3�%
RL2 �.�5% RJ2 1.18%
RL3 1.�3% RJ3 �.86%
RL� �.�7% RJ� �.85%
RJ5 1.17%
Functional materials, 24, 1, 2017 189
Hongxu Zhao et al. / New method for estimating the grounding ...
Theoretically, this test setup is designed to
have a [1m�, ����m��measurement range,
and within full scale the relative error should
be smaller than 5%. According to the measure-
ment results, showing in table 1 to table 3, both
of the design objectives have been achieved.
Conclusion
A new methodology is proposed to evaluate
the reliability of the grounding connection by
testing both the loop resistance and joint resis-
tance. Compare to the traditional method, the
cable is no longer needed to be dissembled any
more. A test setup is built to verify the valid-
ity, accuracy and test scope of such method. As
shown by the experimental results, the mea-
surement range is [1m�, ���� m��, and within
full scale the relative error is smaller than 5%.
Acknowledgments
This work was supported by Seed Founda-
tion of Tianjin University(15ZCZDGX��35)
; The Fundamental Research Funds for The
Central Universities (3122�15D�13); The Fun-
damental Research Funds for The Central Uni-
versities (3122�15F��2).
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