Bhavin Chamadiya, Stephan Heuer
*Research & Development, Daimler AG, Hanns-klemm str. 45, Boeblingen, Germany
FZI Forschungszentrum Informatik, Karlsruhe, Germany
Manfred Wagner*, Ulrich G. Hofmann
Institute for Signal Processing, University of Lübeck, Lübeck, Germany
Keywords: Non-contact electrocardiography (CCECG), Textile electrode, Realistic driving situation, In-car vital
parameter monitoring.
Abstract: Growing mobility demand in the western world intensifies the concern for automotive safety and health
monitoring in daily life. This study shows one solution to integrate textile based, capacitively coupled
electrocardiography into a car considering a real automotive environment. Electrodes based on conductive
textile were integrated into a car seat. Contact ECG and non-contact CCECG measurements were done in
different situations like driving high speed on highways, on surface streets, with various clothes and others.
The influences of various car functionalities on the measurement were detected. Feasibility to measure
Electrocardiography is discussed to evaluate continuous non-contact monitoring for safety, healthcare and
comfort as well.
Automotive safety is a crucial topic, with human
mobility difficult to imagine without individualised
automobiles. Even though a growing number of
passive car safety solutions have been implemented
over the past decades and led to a decrease in
fatalities the human driver is still the primary cause
for accidents.
A number of biomedical and monitoring systems
have been incorporated in automobiles for
healthcare (D’Angelo et al., 2010) as well as safety
(Lee et al., 2007) improvement. However,
physiological monitoring is still a nascent tool for
real automotive healthcare and safety, mainly due to
difficult handling of monitoring equipment outside a
As such, non-contact measurements of driver’s
vital parameters by unobtrusive monitoring might
improve general traffic safety immensely.
Consequently the focus of this study was to
integrate capacitive electrodes for
electrocardiography in a real automotive
environment. Vital sign recordings have been
performed while driving in several real world
2.1 Capacitively Coupled
Electrocardiography (CCECG)
The seemingly only customer acceptable method to
acquire ECG signals from the driver of a car would
be a non-contact one, since it avoids the bodily
contact and limitations of a regular monitoring
device. We chose, due to their simpler
implementation, a capacitive coupling (CC) to the
drivers bio-potentials, thus avoiding any type of
galvanic connection between the driver and the
measurement system (Harland et al., 2002).
Unlike conventional ECG systems that use low
impedance electrical contacts to acquire electrical
signals from the body‘s surface, CCECG systems
require a capacitive (very high impedance) contact.
Hence body and electrode form a plate capacitor to
carry a signal from the body to a very high input
Chamadiya B., Heuer S., Wagner M. and Hofmann U..
DOI: 10.5220/0003194504220425
In Proceedings of the International Conference on Biomedical Electronics and Devices (BIODEVICES-2011), pages 422-425
ISBN: 978-989-8425-37-9
2011 SCITEPRESS (Science and Technology Publications, Lda.)
impedance preamplifier (Lim et al., 2006). Signals
from two preamplifiers are fed to a differential
amplifier and thus remove most of the common
mode signal. To further improve common mode
rejection, a driven seat circuit is used (Kim et al.,
2005). Additionally the signal is algorithmically
processed in real time in order to remove other
unwanted signals from it. A sketch of the potential
integration of sensors is depicted in figure 1,
including steering wheel integrated biosignal
measurement (Heuer et al., 2010).
Figure 1: Textile CCECG integration concept in INSITEX
Figure 2: Structure of the textile electrode (top),
Implemented electrode with preamplifier module
2.2 Textile Electrode
Intense testing of rigid PCB electrodes led to the
conclusion, that a flexible and soft electrode
structure is essential for a useful CCECG. Thus our
electrode is made up of three layers of conductive
textile for electrode (sensor area), guard and ground
respectively as depicted in figure 2 (top). The
conductive layers are isolated against each other
with insulating PU films. The textile is washable and
breathable Eblocker from Novonic (E-Blocker from
Novonic, 2010).
The three conductive layers of the assembly are
attached to the preamplifier module by their
respective connection through three conductive snap
2.3 System Integration
To make the integration suitable for both a seat in
lab and car, electrodes are fastened into a seat cover
of the Mercedes Benz C-class (W204 series).
Figure 3: The electrodes and incised seat cover with
Velcro (top left), the electrodes when fastened into the seat
cover (top right), the seat cover applied on the car seat.
To hold the electrodes tight to the seat cover,
Velcro ribbons are attached around their rims and
the seat cover incision as shown in figure 3. Hence it
maintains a stable, robust and yet removable
configuration. Signals from the electrodes are taken
through the visible blue ribbon cables to commercial
9 pin D-sub connectors (figure 3).
2.4 Measurement Setup
The seat cover is applied to a C class car seat both in
lab and in a real car as well; figure 3 shows the
arrangement inside the car.
The outputs of the electrodes are fed to a signal
processing box. Both inputs to the box are filtered
with high pass filter (0.8 Hz) to remove baseline
drift and DC offset. The differential of the signal is
further filtered with a band pass and 50Hz notch
filter before any amplification.
The pre-processed analog signal is digitised with
a data acquisition card (NI U-9162) for further
processing and final display in LabVIEW 2009.
The driven seat textile electrode is spread
beneath the cushion cover of the car seat to reduce
common mode noise.
The CCECG measurement system has successfully
gathered data for various real driving situations.
Measurements in conditions like driving on
highways, surface street driving, enabling car
functions while driving, by putting on different
clothes on the subject etc. have been performed.
Non-contact ECG recordings under different road
conditions are displayed in figure 4.
Figure 4: The CCECG result on highway (top), city street
in good condition (middle), uneven street in city (bottom).
During all the measurements, the driving subject
wore a t-shirt (100% cotton) with 0.68 mm thickness
and a pant (wool and polyester) with 0.29 mm
thickness. The subject was 56 years old with height
and weight, 182cm and 92kg respectively and was
driving at speed of 100-120 km/h in normal
condition on highway and in the city street 40-60
Due to the massive amount of electrical
appliances in contemporary cars, it was crucial to
test the influence of those functionalities on the
measurement during real driving. Figure 5 shows the
low influence of telephone usage (top), automatic
seat adjustment by DC motors (middle), and
electrical seat heating (bottom).
Complete of many more functionalities will be
presented elsewhere.
Figure 5: CCECG results from different driving activities:
hands-free telephoning (top), adjusting the driver's seat
(middle), with seat heating level 1 & 2 enabled (bottom).
Figure 6 shows a clear and strong effect of the
drivers clothing on the signal quality, since this will
strongly influence the capacitive coupling and thus
the monitoring result. The clothes consisted of a
winter jacket made up of 85% polyester and 15%
polyamide with 0.35 mm thickness, a rain jacket
made up of 100% nylon lined with 0.44 mm PU and
a sportcoat made up of 55% linen and 45% viscose
with 0.85 mm thickness.
Figure 6: Signal to noise ration of the CCECG signal with
various clothes and respective CCECG Signals.
BIODEVICES 2011 - International Conference on Biomedical Electronics and Devices
A practical approach to integrate a textile CCECG
system has been implemented in our experiments.
Measurements during common driving situations
could be demonstrated. It can be observed that only
driving on bad and bumpy roads (hence strong car
and body movement) did interfere with the
monitoring by causing rapid base line drifting.
Some of the seat functions also have influences
from mild to intense on the signal as depicted in
figure 6. Interference from automatic seat
adjustment while driving was minor as the function
is enabled by DC motors driven with 50Hz pulses
(Chamadiya et al., 2008) and the body maintained a
stable contact with the electrodes in the seat. Low
frequency base line drift and 50Hz hum noise from
the DC motors were filtered by the monitoring
system. Seat heating with level 1 and 2 showed
major effects on the monitoring results as they had a
PWM signal of 24 Hz (Chamadiya et al., 2008).
However, we speculate that interfacing our
monitoring setup with the car‘s own controls and
sensors could alleviate the severity of these
Clothes in general did have an impact in the
signal-to-noise ratio, but did not prohibit heart rate
monitoring and require further investigation.
Summing up, this work demonstrates promising
non-contact monitoring results with a textile
CCECG system in real world driving situations. The
system shows a strong potential to be incorporated
in a car for long term ECG measurement for safety
and healthcare.
We would like to thank the BMBF (German
Ministry for Education and Research) for funding
the work of INISTEX project.
D’Angelo, L., Parlow, J., Spiessl, W., Hoch, S., Lüth, T.,
2010. A system for unobstrusive In-Car Vital
Parameter Acquisition and processing. 4
International Conference on Pervasive Computing
Technologies for Healthcare. Garching, Germany 22-
25 march 2010.
Lee, H., Kim, J., Kim, Y., Baek, H., Ryu, M., Park, K.,
2007. The relationship between HRV parameter and
stressful driving situation in the real road. 6
International Special Topic Conference on ITAB.
Tokyo, Japan 2007.
Harland, C. J., Clark, T. D., Prance, R. J., 2002. Electric
potential probes-new directions in the remote sensing
of the human body. Measurement Science Technology
13, 2002, pp.163-169.
Lim, Y., Kim, K. and Park, K.,. (2006) ECG measurement
on a chair without conductive contact. IEEE
Transactions on Biomedical Engineering, Volume 53
(No.5/May), pp.956-959.
Chamadiya, B., Heuer, S., Hofmann, U., Wagner, M.,
2008. Toward a capacitively coupled
Electrocardiography system for car seat integration.
European conference of the international
Federation for Medical and Biological Engineering.
Antwerp, Belgium 23-27 November 2008. Springer-
Verlag Berlin Heidelberg 2008.
Heuer, S., Chamadiya, B., Gharbi, A., Kunze, C., Wagner,
M., 2010. Unobtrusive in-vehicle biosignal
instrumentation for advance driver assistance and
active safety. IEEE EMBS Conference on Biomedical
Engineering and Science. Kuala Lumpur, Malaysia 30
November-2 December 2010.
Kim, K., Lim, Y., Park, K., 2005. Common mode noise
cancellation for electrically non-contact ECG
measurement system on a chair. In TEMPLATE’06,
Annual Conference on Engineering in Medicine
and Biology. Shanghai, China 1-4 September 2005.
E-Blocker, 2010. E-Blocker product information. [online]
Available at: <http://www.novonic.de/
ml> [Accessed 22 August 2010].