Special Issue

Automobile Electronics

Development of an Automotive Active Safety System
Using a 24 GHz-band High Resolution Multi-Mode Radar
Yasushi Aoyagi*1, Keisuke Morii*1, Yoshiyuki Ishida*1, Takashi Kawate*1,
Toru Yoshikawa*1, Nobuyuki Shimizu*1, Yosuke Kubo*1, Antal Kovats*2

In recent years, Advanced Driver Assistance System (ADAS), which has sensor
devices mounted and avoids vehicle accidents by detecting objects in surroundings, started to be popular. Here, we introduce the examples of the development of integrated performances as an automotive system, using the high resolution multi-mode radar,which we have developed, that can be switched automatically for various applications in the 24
GHz band.

ABSTRACT1.

INTRODUCTION

For the requirements of the sensor that is applied to
ADAS, the functions of relative velocity detecting to foresee a crash risk in advance and of associated poor visibility such as with rain, fog and darkness, are required.
The functional comparison of each sensor is shown in
Table 1.
It is important to meet the regulations in using the radar(radio wave). The 24 GHz band had been provided by
the relevant laws in Japan, U.S., Europe and other countries of the world, is easier to use and has a higher adaptability to the market compared to the millimeter-wave
band (76 GHz band, 79 GHz band) for which relevantlaws have ongoing adjustments. Moreover, various applications of the radar can be considered, thus the multimode performances that can switch the state of its performance are also important.
Table 1

The functional comparison of the sensors.

Table 2

Types

Radar

Laser

Ultrasonic Camera

○

×

×

×

Withstand to weather(fog, rain)

○

×

△

×

Adequacy to nighttime (darkness)

○

○

○

△

○ : suitable, △ : available, × : not available

The trend in making preventive safety technologies
compulsory1), which is promoted mainly in Europe, is

The trend in making preventive safety systems
compulsory.

November,
2013
EuropeMaking installation of the AEB(Autonomous Emergency Braking) on
the new large type vehicles iscompulsory.

The AEB for passenger vehicles willIn the year become an evaluation item (for five2014
star ratings) by Euro NCAP (European
New Car Assessment Programme).
In the year The AEB will be applied to large
2015
continuous production vehicles.
November,
2014

Japan

Relative velocity
direct detecting*1 Automotive System & Device Laboratories,
Research & Development Division*2 Furukawa Electric Institute of Technology Ltd.

shown in Table 2. The expansions into the general vehicles and into pedestrian protection application further inthe future are also considered.

Making installation of a crash damage
reduction brake on new large type
trucks and buses is compulsory.

The addition of AEB to the evaluation
In the year standard will be planed to consider in
2014
JNCAP (Japan New Car Assessment
Program).
November,
2017

The AEB will be applied to large
continuous production vehicles.

These are the sensing mainly intended to forward long
distance. The importance of the all-around monitoring inshort distance are lively discussed in international conferences, such as IWPC, on which the manufactures of vehicles or sensors meet, and there is a possibility of applications for insurance rate discounts and for the evaluation
standard in the assessments mentioned above with thegoals of accident reduction.
Here, we introduce the applications for the all-aroundmonitoring and the examples of the development of inteFurukawa Review, No. 44

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Development of an Automotive Active Safety System Using a 24 GHz band High Resolution Multi-Mode Radargrated performances defined as the automotive system,
using the high resolution multi-mode radar at the 24 GHz
band which we have developed and which can be suitable to various applications.

2.

THE 24 GHz BAND HIGH RESOLUTION
MULTI-MODE RADAR

In this chapter, we will introduce the outline of the multimode radar (B0 sample) that is being considered.
Comparing to the narrowband radar of the conventional
method (Figure 1-a), it becomes possible to segregate
high density objects and to detect substantially theangles and the distances of each object with the signal
processing and the circuit technologies developed on thebasis of the Ultra Wide-Band (UWB) radar technology2)
which had been reached so far (Figure 1-b, c).

Table 3Specifications of the 24 GHz band high resolution
multi-mode radar.
Item

Value

Modulation method

Pulse

−

Frequency band

24.05 – 24.25

GHz

Minimum detection distance0m

Maximum detection distance72

m

Horizontal angle range

120

deg.

Minimum detection target

Pedestrian
100 × 100 × 30

Shape

Data ofthe vehicle
state

mm

Gear state

Reverse

Vehiclespeed

Low speed
R-CTA

Distance

Distance

Application

Speed
a. Conventional method

ForwardHigh speed
LCDAS

The radar detects
vehicle stateand change theoperational mode.
Speedb. Proposed method

Figure 2 Examples of the autonomous changes of theoperational modes.

3.

Reception
intensity

Distance

Unit

Relative velocity

c. Example of a multi-target separation

THE PREVENTIVE SAFETY SYSTEMUSING THE RADAR

The preventive safety system which consists of the radar
itself can alarm to a driver through the Human MachineInterface (HMI) when the crash with a detected object ispredicted. The name of the applications is specified
depending on what types of dangers are alarmed.
Figure 3 shows various perimeter monitoring applications and examples for the placement of each application
and beam3). One application is shown for each beam,
therefore the placements of the beams with the samefunctions are assumed to be on the right and the left or in
the front and the back.

Figure 1 The realization image of a high resolution.

Specifications of the 24 GHz band high resolution multimode radar are shown in Table 3. The Control Area
Network (CAN) is used as the interface, and the radar
selects autonomously operational modes while using thevehicle information data (vehicle speed, ON / OFF of
winker, gear) which can be obtained by connecting to the
CAN of the vehicle body. According to each operationalmode, the danger toward a driver is assessed andalarmed.
Figure 2 shows examples of the autonomous changesof the operational modes.

Lateral crash prediction
Parking
assistance
Measuring distance
between cars with
low-running speed
Front side crashprediction
Pedestrian
protection

Rear side blindspot detection
Rear side parking
assistance
Rear side crashprediction
Rear side pedestrian
protection

Lateral blind spot detection

Figure 3 Examples of the various perimeter monitoring
applications using the radar.

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Development of an Automotive Active Safety System Using a 24 GHz band High Resolution Multi-Mode Radar

3.1.

The Posterolateral Application(LCDAS: Lane Change Decision Aid System)4)
With respect to assisting safety in lane change, which
detects the existence of another vehicle diagonallybehind and alarm to the driver, LCDAS is getting gradually popular since 2005 mainly in the Euro-American markets to be installed on the luxury or top-of the line cars as
an optional equipment. There are three types for the
LCDAS.
a. L CDAS Type-I: The Blind Spot Detection, which
detects other cars entering the blind area aroundown car (adjacent lanes on the right/left and backarea within 3m or so)b. LCDAS Type-II: The Closing Vehicle Warning, which
detects other cars which rapidly approach on theadjacent lanes, in addition to the blind area.
c. LCDAS Type-III: The type which combines Type-I
and Type-II.
With respect to warning to drivers, there are systems
that only light a warning lamp and that make stronger
caution such as adding torque on a steering wheel when
the car is about to change the lane in the dangerous situation.
Also, Rear-Cross Traffic Alert (R-CTA)5) is the applicationthat detects the vehicles or the pedestrians that exist in
the blind area and prevent serious accidents such as
bodily injury when unloading backward from a parking
space, and often uses the same sensor the LCDAS does.
It makes alarms to the driver with sound and LED and
performs an automatic break control if the dangers, suchas crash, are expected.
The operation image of R-CTA is shown in Figure 4.

longer detecting distance than R-CTA.
In addition to this, the preventive safety technologies,
such as the application developed with respect to a monitoring in 360-degree view, are being actively developed.

Figure 5 Image of F-CTA performances.

4.

THE SYSTEMS MOUNTED
ON VEHICLES

4.1 The Recording System of Measuring Data
Since the preventive safety system can be consisting of
the radar itself, to confirm the validity of measurement on
the development process, it needs indicating and recording not only the detecting results of the target on a realtime basis but also the detecting results of the referential
sensors being synchronized. As the referential sensors,
we used LIght Detection And Ranging (LIDAR); (Laser
scanner, Detected data for distance and orientation) anda camera (confirming the scenes which are assessed).
The measuring data flow is shown in Figure 6. The
detecting results and assessed results are indicated on
the PC display on a real-time basis and the data isrecorded at the same time.

Speed

Gear

Steering

Brake
etc.

Figure 4 Image of R-CTA performances.

3.2.

The Anterolateral Application(Front-Cross Traffic Alert: F-CTA)
The operation image of F-CTA is shown in Figure 5.
F-CTA is the application that detects the vehicles andthe pedestrians in left and right forwards to avoid accidents having them bumped into each other at blind intersections and others. As same as R-CTA, F-CTA makes
alarms to the driver and performs an automatic breakcontrol if the dangers, such as crash, are expected.
However, since the speed of the intended vehicle is faster,with respect the time until it crashes, F-CTA requires a

Radar Performance Validation Based on Reference Data
Radar Data

Ref. Data

Multi-media
Data Analysis
TTC Consideration

Figure 6

The measuring data flow.

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Development of an Automotive Active Safety System Using a 24 GHz band High Resolution Multi-Mode RadarIn the application decision, it is possible to assess eachmode by stabilizing the operational mode, and also toassess the validity of the mode transition by obtaining thevehicle information data as shown in Figure2.
4.2 Mounting on the Vehicles
Figure 7 shows the schematic for mounting the radar andthe measuring systems on the vehicles.
To accommodate a driving test and others, the measuring system is mounted on the vehicle for evaluation. The
radars are mounted, in the bumpers, in the four cornersof the vehicle and collect the vehicle information data

Radar

from the CAN of the body. If the amount of data is large
at measurement, it may set up another gateway separately to avoid the radar data flowing into the vehicle body.
On the other hand, for the method of alarm, we selectthe method, where the packet, which shows the alarm
status that is sent from the radar, is displayed on the PC
display or is received by the specific Electronic Control
Unit (ECU), and that controls lighting a LED and honking
a buzzer which are mounted in the Human MachineInterface (HMI) installed on the dashboard.

Radar
CameraLIDAR

Body CAN-bus

Gateway

PC

Radar

Radar

Figure 7 Mounting the radar and the measuring systems on the vehicles.

4.3 Examples of the Alarm Performance
Examples of the performance of this vehicle mounting
system are shown for F-CTA.
(1) A ccording to the vehicle information data, theappropriate application is activated.

(2) Time To Cross line (TTC) is computed toward a vehicle coming closer, and an alarm packet is sent if theresult of the computing is assessed as smaller than
the specified TTC value.

(3) The upper-level system such as the PC or the HMIECU receives the alarm packet and warns to thedriver.
PiPiPiMoreover, it is possible to alarm as the radar lights
directly the LED for the condition (3) above.

5.

ON BOARD EVALUATION

5.1 Contents of the Evaluation
Based on the results from the previous chapters, using
the vehicle for evaluation with the radar mounted, we conFurukawa Review, No. 44

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Development of an Automotive Active Safety System Using a 24 GHz band High Resolution Multi-Mode Radar

firm that the alarm alerts when a pedestrian is approaching the vehicle.
In this evaluation, the performance of the F-CTA is confirmed for the alarm application toward the front of thevehicle. This alarm has alerted when TTC, which is thetime from when pedestrians or vehicles of coming closer
from the front are detected to when they cross the specified threshold line, becomes shorter than the specified
time. Small TTC value means that the time is short until
the pedestrian has a crash with the vehicle and that thedegree of the risk is high.
This alarm can be set the specified time for TTC on any
value according to the degree of the risk. In this evaluation, we set the alarm warning time as followings.
a. The degree of the risk: Low (Level 1) = 6 sec.
b. The degree of the risk: Middle (Level 2) = 4 sec.
c. The degree of the risk: High (Level 3) = 2 sec.
Considering the detected data from the LIDAR and theimage data from the camera as real values, the validity forthe results of the radar measurement is examined comparing the measured value by the radar with the real values.
5.2 The Evaluation Results
Figure 8–10 shows the continuous representations of the
movement locus of the pedestrian who is detected by theradar. The upper section of each of the figures shows thecamera footage and it can be seen that the pedestrian isapproaching on foot from the right side. The lower section of each of the figures shows a detected object by theradar and its alarm levels. The blue square shows theplace of the evaluated vehicle. The green circle shows
the detected information data by the radar on a real-timebasis. The pedestrian detected by the LIDAR measurement system is shown by the blue-violet dots in the figures. The radar is set to detect only moving objects andthe evaluated vehicle is stopped, therefore only thepedestrian is detected.

Figure 9 The detection of a pedestrian in the alarm level 2.

Figure 10 The detection of a pedestrian in the alarm level 3.

From the result of the evaluation, it can be confirmedthat the detection of a pedestrian by the radar and thetrue value are in the same position, by comparing them.
Figure 11 shows the detected position of a pedestrianand the alarm level. It can be confirmed that the pedestrian is approaching toward the vehicle as time advancesand can be detected almost without errors, comparing
with the detection by the LIDAR measurement system.
In addition, going back from the TTC=0 (sec.) where
the distance to the vehicle becomes zero, the alarm level
progresses from Level 1 to Level 3 at the points of 6, 4,
and 2sec. In this evaluation, it is confirmed that the alarmis warning at the specified alarm time.

Figure 8 The detection of a pedestrian in the alarm level 1.

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REFERENCES

Detected distance of a pedestrian by the radar
Detected distance of a pedestrian by the LIDAR

16

Alarm level

12

3

8

2

4

1

0

7

6

5

4

3

2

1

0

Alarm level computed by the radar

Distance from the cross line to a pedestrian (m)Development of an Automotive Active Safety System Using a 24 GHz band High Resolution Multi-Mode Radar

1) “Minutes of the Japan New Car Assessment Program Evaluation
and Investigative Meeting”, Ministry of Land, Infrastructure,
Transport and Tourism, http://www.mlit.go.jp/jidosha/carinf/ast/
ast_m_meet.htm
2) Kei Takahashi, “Development of 26 GHz-band UWB Radar for
Automobiles”, Furukawa Review No. 37 (2010)
3) ISO 17387, “Intelligent Transport Systems – Lane Change Decision
Aid Systems (LCDAS) – Performance Requirements and Test
Procedures”, (2008)
4) Society of Automotive Engineers of Japan, http://guide.jsae.or.jp/
topics/49678/
5) “Blind Spot Information System (BLIS) with Cross-Traffic Alert”(2012), http://corporate.ford.com/doc/BLIS.pdf

0Time to Cross line (TTC)
Figure 11 The detected position of a pedestrian and the alarmlevel.

6.

CONCLUSION

Here we introduce the applications which target the panoramic monitoring of surround of the vehicle and theexamples of the construction of the automotive system
which can correspond to each application using the 24
GHz band high resolution multi-mode radar which wehave developed. Moreover, it is confirmed that the alarmlevels according to the degree of the risk can be activatedand the accuracy of the calculated TTC has no large difference when comparing with the real value from using
the developed radar. Even if the vehicle is running, withconstructing the system that can make quantitative evaluations, it becomes possible to assess the timing of thealarm, the detecting and the un-detecting at the actual
running evaluations on general roads and highways.
We will improve the accuracy and expand the range ofthe application in the future.

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