1. Damage Mitigation Braking System
Informal document No. GRRF-S08-12
Special GRRF brainstorming session 9 December 2008 Agenda item 3
Transmitted by expert from Japan
Damage Mitigation Braking System
Advanced Emergency Brake Systems (AEBS)　
Japan prepared the presentation of progress in technical requirements about advanced emergency brake systems.
So, today I talk about activity of making the regulation of damage mitigation braking system in Japan.
Progress in Technical requirements

2. 1. History of Discussion and Production of
Damage Mitigation Braking System in Japan
2001 Design principles for ASV systems
2003 Technical guideline for Damage Mitigation Braking System
First release of DMBS in passenger cars
Revision of technical guideline for
Damage Mitigation Braking System
First release of DMBS in large trucks
2007 – Discussion on the technical regulation of Damage
Mitigation Braking System for Large Truck
This page shows the History of Discussion and Production of Damage Mitigation Braking System in Japan.
From 2001, We designed principles for ASV systems.
ASV is advanced safety vehicles which is included the driver assistance systems.
For example, Adaptive cruise control, Lane keeping assist system, Damage mitigation braking system.
About the Damage mitigation braking system, In 2003, we made the first technical guideline and in 2005 we revised the guideline.
The details of revision change the timing of automatic braking.
And now, we started to discuss the technical regulation.

3. 2. Study of Detailed Design Principles of ASV（Advanced Safety Vehicle）
(Formulated in the ASV-2 Project)
This page show the study of detailed design principles of ASV.
We think three sentences.
Driver assistance, ASV technologies should understand driver’s wills and support their safe driving based on the concept of driver responsibility.
Social acceptance, ASV technology equipped vehicle must operate with un equipped vehicles and pedestrians.
Therefore, we must consider how to obtain proper understanding of the public.
Driver acceptance, ASV technologies should be easy to use and be trusted by drivers.
This means that a human-machine interface design should be appropriately implemented.
The concept of driver assistance was formulated for driver load reduction and accident avoidance assistance technologies in order to facilitate the interpretation of Design Principles of ASV.
The concept of driver assistance was formulated for driver load reduction and accident avoidance assistance technologies in order to facilitate the interpretation of Design Principles of ASV 3

4. Approach to Brake Control
2. Study of Guidelines for the Commercialization of Damage Mitigation Braking System (1)
Approach to Brake Control
Brake control by ASV systems is effective in reducing/avoiding collisions
There is a concern that if braking is automatically applied in a dangerous situation, the driver may neglect to take evasive action he/she should essentially perform (driver overconfidence in the system).
If the damage mitigation braking system is designed to brake when it determines that a collision is physically unavoidable, it is assumed the driver will not put too much confidence in the system.*
System starts applying brakes if it determines a collision is unavoidable - Physical avoidance limit by braking - Physical avoidance limit by steering
Based on the Design Principles of ASV, system issues a warning to alert the driver to take evasive action before it applies brakes
This page shows approach to brake control.
First topic, Brake control by ASV systems is effective in reducing/avoiding collisions.
Second, There is a concern that if braking is automatically applied in a dangerous situation, the driver may neglect to take evasive action he/she should essentially perform.
Third, If the damage mitigation braking system is designed to brake when it determines that a collision is physically unavoidable, it is assumed the driver will not put too much confidence in the system.
So, we decided in the guideline.
System starts applying brakes if it determines a collision is unavoidable.
Physical avoidance limit by braking and steering.
The system issues a warning to alert the driver to take evasive action before it applies brakes.
*This has been verified by a study of drivers’ dependence on ASV systems 4

5. How Damage Mitigation Braking System Work
2. Study of Guidelines for the Commercialization of Damage Mitigation Braking System (2)
How Damage Mitigation Braking System Work
Just in the nick of time!
In response to a warning the driver applies brakes
ASV vehicle
Whew, just a small dent
The on-board system automatically applies brakes
Looking away
Beware of obstacle!
Careless
If the driver is too slow to apply brakes…
Brake control
Inattentive
Too late!
Driver fails to notice situation and brakes late
This page shows how to work the damage mitigation braking system.
A driver is driving. If the vehicle is equipped the damage mitigation braking system.
A driver notice the dangerous situation by warning.
And if driver don’t notice the dangerous situation by warning.
The damage mitigation braking system is actived.
As the result, the collision speed is reduced, and the damage is mitigated.
Non-ASV vehicle 5

6. 3. The state of the traffic accident in Japan (1)
Half of Japanese traffic accidents caused by large trucks are the rear-end collisions. (55%)
Rate of fatalities in rear-end collisions is much higher in large trucks.
This page show the state of the traffic accident in Japan.
These data show the traffic accident of large track.
Half of Japanese traffic accidents caused by large trucks are the rear-end collisions. (55%)
Rate of fatalities in rear-end collisions is much higher in large trucks.
These data show Damage Mitigation Braking System is effective in Japan .
Damage Mitigation Braking System is effective in Japan

7. 3. The state of the traffic accident in Japan (2)
On the highway, many accidents are against traveling vehicles
On the open road, many accident are against stationary vehicles
These data show the state of the forward vehicle in the rear-end collision.
On the highway, many accidents are against traveling vehicles.
On the open road, many accident are against stationary vehicles.
In Japan, Damage Mitigation Braking System should cover the forward vehicle which is travelling and stationary.
Damage Mitigation Braking System should cover the forward vehicle which is travelling and stationary

8. Absolute entrustment in the system (Too much faith in the system)
4. Timing of Brake Control
WARNING
Brake works automatically
Collision
If the vehicle stopped with Damage mitigation braking system
Absolute entrustment in the system
(Too much faith in the system)
Damage mitigation braking system will be automatically activated.
I can stop without crash!
Truck driver
Usually, Damage mitigation braking system activate warning and automatic braking.
Even if the automatic braking activate, the vehicle collide.
But, we think if the vehicle stopped with Damage mitigation braking system.
In this case, Truck driver think Damage mitigation braking system will be automatically activated.
I can stop without crash! So, next time the driver may neglect to avoid action and causes a collision.
Therefore, Japan think the timing of brake control is important for the view point of driver sovereignty. z
Collision
Timing of brake control is important for the view point of driver sovereignty

9. 4. Timing of Brake Control - Point of view -
First step:
Operational range based on physical avoidance limit
Brake control begins at the point the driver is unable to avoid a collision by either braking or steering (collision judgment line)
Second step:
Operational range based on driver’s usual maneuvers limit
So, we decided the operational range which is able to control automatic braking.
At first step, we decide the Operational range based on physical avoidance limit.
Brake control begins at the point the driver is unable to avoid a collision by either braking or steering.
We call the collision judgment line. And at second step, we decide Operational range based on driver’s usual maneuvers limit.
To enhance the damage-reducing effect, we examined how far the operational range can be expanded by bringing forward the timing at which brake or steering control begins.
We call Collision possibility judgment line.
To enhance the damage-reducing effect, we examined how far the operational range can be expanded by bringing forward the timing at which brake or steering control begins (Collision possibility judgment line)

10. 4. Timing of Brake Control - Collision judgment line -
Limit of avoidance by braking
Limit of avoidance by steering
Collision judgment line
Limit of avoidance by braking
Limit of avoidance by steering
Minimum TTC which is necessary that a vehicle avoids a collision by braking.
Minimum TTC which is necessary that a vehicle avoids a collision by steering.
TTC is calculated by minimum stopping distance with the braking test.
This graph show the collision judgment line. X axis is relative velocity. Y axle is time to collision.
TTC means the time reaching a collision.
Limit of avoidance by braking means minimum TTC which is necessary that a vehicle avoids a collision by braking.
TTC is calculated by minimum stopping distance with the braking test.
Limit of avoidance by steering means Minimum TTC which is necessary that a vehicle avoids a collision by steering..
TTC is calculated by minimum lateral displacement with the steering test.
Japan applies the timing.
In the case of Braking, Braking performance is different from vehicle to vehicle. Therefore, this line is changed by each vehicle.
In the case of Steering, TTC = 0.8 (s) fixed value is used for all large trucks.
TTC is calculated by minimum lateral displacement with the steering test.
Japan applies the timing with the following values
Braking: Braking performance is different from vehicle to vehicle. Therefore, this line is changed by each vehicle.
Steering: TTC = 0.8 (s) fixed value is used for all large trucks.

11. 4. Timing of Brake Control
- Collision possibility judgment line -
Operational range based on driver’s maneuvers limit
To enhance the damage-reducing effect, we examined how far the operational range can be expanded by bringing forward the timing at which brake or steering control begins
Distribution of timing at which drivers begin evasive maneuvers under normal driving conditions
Collision possibility judgment line
衝突可能性判断ライン
Time to collision (TTC)
Lower limit of usual avoidance by steering
Lower Limit of usual avoidance by braking
Collision judgment line
衝突判断ライン
Expanded range
Collision possibility judgment line is the Operational range based on driver’s maneuvers limit.
To enhance the damage-reducing effect, we examined how far the operational range can be expanded by bringing forward the timing at which brake or steering control begins.
Gray zone means driver’s maneuvers under normal driving conditions.
We make the expanded range.
That is able to control the automatic braking.
Limit of avoidance by steering
Operational range based on physical avoidance limit
Limit of avoidance by braking
Relative velocity

12. - Collision possibility judgment line -
Collision possibility judgment line is the lowest limit of drivers’ usual avoiding maneuver.
Japan applies the timing with the following values provided from an experiment result
Braking: TTC = ×Rv＋1.54
Steering: TTC = 1.6 (s)
Rv : Relative velocity
Avoidance timing by the steering in large trucks
Avoidance timing by the braking in large trucks
Lower limit of usual
avoidance by braking
Collision possibility judgment line
Lower limit of usual
avoidance by steering
Collision possibility judgment line is the lowest limit of drivers’ usual avoiding maneuver.
Japan applies the timing with the this formula and value(1.6s) provided from an experiment result.
This data show the driver’s maneuvers in the real world.
The blue plot show the drivers’ usual avoiding maneuver by braking.
The blue dot line show the Lower limit of usual avoidance by braking.
There is not the driver operating that is less than this line.
The green plot show the drivers’ usual avoiding maneuver by steering.
There is not the driver operating that is less than green line.
Therefore, we choose the small one of two lines.
The red line is Collision possibility judgment line
Confirmed by real world operation

13. 4. Timing of Brake Control
This graph show the timing of brake control in damage mitigation braking system.
Automatic brake can be controlled from less than Collision judgment line and Collision possibility judgment line.
And requirements in the regulation, From Collision judgment line, Braking shall be operated with average deceleration of 3.3 m/s2 or more.
From Collision possibility judgment line, Braking may be operated. Deceleration is not specified.
System is activated over 15[km/h].
Requirements in the regulation
From Collision judgment line :
Braking shall be operated with average deceleration of 3.3 m/s2 or more.
From Collision possibility judgment line :
Braking may be operated. Deceleration is not specified.

14. 5. Warning and Pre-warning
“Pre-warning" means a function that alerts the driver to a risk of collision in advance and prompts him/her to make an avoiding action.
"Warning" means a function that notices the driver in advance that the system detects an unavoidable collision and starts controlling the brake system.
Braking that causes a maximum deceleration of 0.98 m/s2 to 2.45 m/s2, and of continuation for less than 0.8 seconds can be used for warning purpose.
This page show the requirements of Warning and “Pre-warning. Pre-warning" means a function that alerts the driver to a risk of collision in advance and prompts him/her to make an avoiding action.
"Warning" means a function that notices the driver in advance that the system detects an unavoidable collision and starts controlling the brake system.
And, Braking that causes a maximum deceleration of 0.98 m/s2 to 2.45 m/s2, and of continuation for less than 0.8 seconds can be used for warning purpose.
The requirement of warning is over 0.8 seconds from collision judgment line.
The requirement of warning is over 0.8 seconds from braking between collision judgment line and collision possibility judgment line.
Time of 0.8 (s)（real-time） depends on the reaction time of driver
Time of 0.8 (s)（real-time） depends on the reaction time of driver

15. 6. Other principal requirements
Fail safe function
The system shall have a function to monitor the operating state of the system, and shall detect failures by means of this function.
If any failure has occurred in the system, the operation of the system shall stop safely and the system shall return to its original function as a brake system.
Malfunction tell-tale
If any failure occurs with the system, a visual alarm shall be given.
Warning of over limit of function
If the said system recognizes that the current situation does not allow its operation, such as when the system detects contamination on the frontal obstacle detector, driver in the driver seat shall be provided with a visual message indicating that the current situation does not allow the system to function.
Off switch
The vehicle may be equipped with a off switch. While the operation of the said system is disabled by the cancellation device, the driver in the driver seat shall be provided with a visual message indicating such situation.
This page show the other principal requirements.
Fail safe function, Malfunction tell-tale, Warning of over limit of function, Off switch

16. 7. Performance Test Measurements: ・Distance ・Velocity ・Deceleration
・Collision trigger
・Sound pressure and video to check pre-warning and warning
to calculate TTC
Target equivalent to passenger cars
(for Millimeter wave sensor)
This page show the performance test.
Some photograph is the test with stationary target.
In this case Target equivalent to passenger cars.
This target use for millimeter wave sensor.
But, Japan is now investigating the validity of the target.
This target isn’t the final conclusion.
And these is item of measurements.
Japan will continue to investigate the test method for both stationary and travelling target.
I prepared some video of test.
Japan is now investigating the validity of the target. This target isn’t the final conclusion.
Test velocity:20,40,80 [km/h]
Japan will continue to investigate the test method for both stationary and travelling target.
VTR

18. 7. Performance Test - Other items -
Test for operation to obstacle on outside track
Test for operation of alarm upon system failure
Requirements related to brake system for easing frontal obstacle impact in curved road *
* This standard indicates a direction to be adopted in the future for the development of brake system for easing frontal obstacle impact, as well as the technology to reduce collision speed by increasing average deceleration value. In the future, according to the technology circumstances of frontal obstacle detection and other technologies, the specific test methods need to be defined as necessary.
This page show the other items in performance test.
First line is test for operation to obstacle on outside track.
This test confirms that a system does not operate in the case of the outside obstacle of the traffic lane.
I prepared the VTR. After I’ll play.
Second line is the test of alarm upon system failure.
Third line is the test about curved road.
The Japanese regulation does not prescribe the requirement of the curve in consideration of the present technical level.
However, the requirement of the curve is necessary.
So, we writes a regulation as a future investigation item.
VTR

20. 7. Performance Test - Other items -
Test for operation to obstacle on outside track
Test for operation of alarm upon system failure
Requirements related to brake system for easing frontal obstacle impact in curved road *
* This standard indicates a direction to be adopted in the future for the development of brake system for easing frontal obstacle impact, as well as the technology to reduce collision speed by increasing average deceleration value. In the future, according to the technology circumstances of frontal obstacle detection and other technologies, the specific test methods need to be defined as necessary.
This page show the other items in performance test.
First line is test for operation to obstacle on outside track.
This test confirms that a system does not operate in the case of the outside obstacle of the traffic lane.
I prepared the VTR. After I’ll play.
Second line is the test of alarm upon system failure.
Third line is the test about curved road.
The Japanese regulation does not prescribe the requirement of the curve in consideration of the present technical level.
However, the requirement of the curve is necessary.
So, we writes a regulation as a future investigation item.
VTR

21. Thank you very much for your attention