- In advance, based on the experiences of the author, who was an engineer of an automotive manufacturer, and prior discussions with the manufacturer’s engineers, the type and measuring method of the heart rate detection system are summarized.
- We used google scholar to search for papers on the types and measurement methods we had identified and selected relatively new papers as the target of our investigation. In some cases, however, the papers were not disclosed due to patents or were not published as a paper because the heartbeat monitoring system is more about development than research. In such cases, the survey was conducted on the Web, and relatively new content was selected for the survey.
2. Trends in Research and Development
- Algorithms for high accuracy and steady measurement of heartbeat;
- In-vehicle heartbeat measuring systems focused on driving.
2.1. Research Trends in Algorithm Development
2.2. Research Trends in Heartbeat-Measuring Systems Applied to Drivers in Vehicles
2.2.1. Measurement by Wearable-Type Devices
2.2.2. Measurement by Nonwearable-Type Devices
- Correction of the offset shift of I-Q Lissajous due to changes in the positional relationship with the surrounding metal objects.
- Synchronous detection for detecting pulsation-period signals buried in external disturbances. A model pulse wave signal was generated by applying the feedback of the estimated pulse wave number. The difference between this signal and the pulsation signal after the adaptive filter processing was recorded. The adaptive filter coefficients were updated so that the mean-square deviation was minimized.
- Removal of periodic artifacts, such as respiratory harmonics. The respiratory component was extracted from the Doppler angular velocity signal, and the harmonics were estimated. The signal was passed through an adaptive filter, the difference from the Doppler angular velocity signal was recorded, and the coefficients of the adaptive filter were updated to minimize the mean-square deviation.
- For the time being, in-vehicle devices or in-vehicle cameras are used for the detection of a heartbeat, and in-vehicle cameras are used for the detection of the driver’s facial expression.
- Smartwatches and the camera of the smartphone are used for detection of heartbeat, and the camera of the smartphone is also used for detection of driver’s facial expression after some issues such as recharging and connectivity are solved perfectly.
- However, as for the professional driver, in-vehicle devices or in-vehicle cameras are used for the detection of a heartbeat, and in-vehicle cameras are used for the detection of the driver’s facial expression because they are obliged from the viewpoint of labor management.
3. Proposal for the Autonomous Driving Era
Institutional Review Board Statement
Informed Consent Statement
Conflicts of Interest
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|Measures the electrical|
pulses generated by the
body during each
|Electrodes||Difficult to position|
correctly, affected by
loose when the body is
|A method for measuring|
changes in arterial
pressure that vary with
|Affected by body|
|Cardiogram||Measure the sound|
generated by the pulsation
of the heart
|Affected by hand|
and finger movement
|Near-infrared light is|
applied to the skin surface
and the reflected light is
received by a photodiode
or other device
|Smartwatch||Affected by body|
of fingers, skins, etc.
|Type of System||Measuring Methods|
heartbeat measuring system
|Ring-type||Jung et al. ||2007||Flashing an|
|Oura ||2016||R2 = 0.996 for|
resting HR and
R2 = 0.980 for
|Necklace-type||Fujitsu ||2015||Wear the ear|
clip sensor on
the ear to
|Shirt-type||Kasai et al. ||2015||Measure pulse|
waves by the
et al. 
while driving is
between 5 and
|Murata et al.|
it is over 90%)
the seat cover
and the seatbelt
irradiated to the
driver’s body and
of the reflected
accuracy due to
of person’s skin
is less than 3 bpm
|Okada et al.|
|2018||Change in the|
value of the
using the skin
separation on the
RGB pixel values
of facial images
|NA (only the|
accuracy of facial
|Kwon et al.|
change took by a
|Sun et al. ||2018||Facial color|
change took by
and IQR of rMSSD
is 4.10, 2.76 and 3.74,
|Huang ||2016||Facial color|
change took by
|The mean of|
absolute errors of
HRV metrics is 3.53 ms
to be guaranteed,
easy to wear,
many people have them
if forget to wear,
there are some
such as recharging and
the robustness of
to be guaranteed,
easy to wear
|Shirt-type||Discomfort to wear|
|Steering-type||Not restrict the|
can measure at
any time in spite
of driver’s willing
|Need to be installed|
at the time of
purchase or after
purchase the vehicle,
|Camera-type||Accuracy in the cabin|
has not been fully
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