Signal Processing - November 2016 - 23
Overview
often depends on the driver's intention (e.g., driver's intentional eye blinking does not indicate a driver's driving pattern), it
requires additional information to increase the accuracy in the
driver's status detection [5], [6].
Recently, physiological signals such as ECG and PPG
have been used in DSM systems, where the level of detection
accuracy is greater when compared to the DSM systems using
vision sensors or driving patterns, because the physiological
signals are highly correlated to the driver's physical status [7],
[8]. Table 1 shows the features of DSM systems developed by
major automobile manufacturers.
To reduce the occurrence of serious traffic accidents caused
by driver incapacitation due to fatigue and drowsiness, and
to protect drivers from fatal accidents, increasing attention
is being paid to DSM systems equipped with vision sensors,
steering angle sensors (SASs), and physiological sensors.
These types of DSM systems has been developed mostly by
major automobile manufacturers such as Ford, Toyota, BMW,
among others, since the early 2000s [5], and some important
technologies are already commercialized or considered for
smart vehicles. This article introduces the overall design of
DSM systems, as applied to smart vehicles, being developed
by the major automobile manufacturers. In particular, we
Signal processing algorithms for DSM
focus on DSM systems utilizing physiological signals such
systems using physiological signals
as ECG and PPG, rather than the conventional DSM systems
As mentioned in the section "Various Driver Status Moniusing vision sensors or SAS.
toring Technologies," the conventional DSM systems may
The section "Signal Processing Algorithms for DSM Sysnot be able to detect a driver's abnormal status correctly; for
tems Using Physiological Signals" introduces the signal
example, when a driver's eye blinking and reckless driving
processing techniques and noise reduction
are intentional. Therefore, there has been
algorithms that are tested and used by the
a strong demand for new DSM technoloDriver status monitoring
automobile manufacturers for the acquigies [22], and among the new technolosystems have emerged as
sition and enhancement of physiological
gies introduced, DSM systems using
an innovative technology
signals in noise to extract the parameters
driver's physiological signals have gained
to prevent traffic accidents increasing attention. In general, physirelated to the driver's status. Electromagfrom driver incapacitation. ological signals are classified into ECG
netic compatibility (EMC) issues that need
to be addressed for the application of DSM
and PPG, which are measured from the
technologies to actual smart vehicles are introduced briefly in
driver's heart rate and pulse, respectively. In recent realizathe section "EMC Issues in DSM Systems Using Physiological
tions of DSM systems using physiological signals, ECGs are
Signals." The purpose of this article is to present a guideline
more reliable in noisy in-vehicle environments. Therefore,
for the design of DSM systems for readers who would like
this section focuses on DSM systems that utilize ECG and
to develop the system for commercialization, by introducing
PPG for the primary and secondary observations, respectivethe performance of DSM systems as obtained through actual
ly. In addition, we will later introduce DSM algorithms used
vehicle tests.
in the DSM systems.
Various DSM technologies
In general, DSM systems utilize various sensors to measure
the steering angle, ECG, and PPG to monitor the driver's status
and analyze driver's physiological signals and movements in
the vehicle. The conventional DSM systems are equipped with
a camera [charge-coupled device (CCD), infrared (IR), stereo,
etc.] installed on the steering column and/or infrared-light
emitting diodes (IR-LEDs) mounted inside vehicles so that the
system can measure the driver's eye blink rate, head location,
and the driver's facial direction to detect the driver's status.
Because the detection and recognition performance of the conventional DSM systems largely depend on image and vision
processing algorithms, the conventional DSM systems require
computationally expensive vision processing algorithms [5],
[6], in general.
Some automobile manufacturers have developed DSM systems using driver's driving patterns so that the performance of
the system can be more reliable [4]. In these systems, once the
driver's driving patterns are obtained from a precise SAS, the
patterns are stored in the in-vehicle database (DB) and used to
estimate the driver's status by comparing vehicle's current movements with the DB. However, since a driver's driving pattern
Overall process of DSM systems using
physiological signals
A single cycle of the ECG consists of a P signal, a QRS complex, and a T signal (refer to [23, Fig. 1]). Among them, the
QRS complex has a relatively higher amplitude and signal-tonoise ratio (SNR) in comparison with the P and T signals, so
it is utilized to monitor driver's physical status. On the other
hand, a single cycle of the PPG is composed of systolic and
diastolic peaks [24]. Since the systolic peak has a relatively
higher amplitude than the diastolic peak, it is used to detect the
driver's physical status.
In the system configuration, DSM systems using physiological signals consist of a physiological signal measurement
block and a DSM algorithm. The physiological signal measurement block employs an analog signal processing technique
for ECG acquisition, which is classified into a contact-based
ECG acquisition technique that obtains ECG through the
driver's two hands on the steering wheel, and a noncontactbased ECG acquisition technique that acquires ECG through a
capacitive connection between the driver and the electrodes on
the driver's seat. The contact-based ECG acquisition technique
uses two electrodes installed on the steering wheel to have
IEEE SIgnal ProcESSIng MagazInE
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November 2016
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23
Table of Contents for the Digital Edition of Signal Processing - November 2016
Signal Processing - November 2016 - Cover1
Signal Processing - November 2016 - Cover2
Signal Processing - November 2016 - 1
Signal Processing - November 2016 - 2
Signal Processing - November 2016 - 3
Signal Processing - November 2016 - 4
Signal Processing - November 2016 - 5
Signal Processing - November 2016 - 6
Signal Processing - November 2016 - 7
Signal Processing - November 2016 - 8
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Signal Processing - November 2016 - Cover3
Signal Processing - November 2016 - Cover4
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