19-03-2014, 01:12 PM
Automated Emergency Brake Systems: Technical requirements, costs and benefits
Emergency Brake Systems.pdf (Size: 1.38 MB / Downloads: 156)
Executive summary
Vehicle technology has increased rapidly in recent years, particularly in relation to braking systems
and sensing systems. The widespread introduction of anti-lock braking systems (ABS) has provided
the building blocks for a wide variety of braking control systems. Additional hardware that allows
brake pressure to be increased above pedal demand as well as to be reduced, combined with additional
software control algorithms and sensors allow traction control (TC), electronic brake force
distribution (EBD), brake assist (BA) and electronic stability control (ESC) functions to be added.
In parallel to the development of braking technologies, sensors have been developed that are capable
of detecting physical obstacles, other vehicles or pedestrians around the vehicle. Many luxury, mid-
size and small cars in Europe, and in Japan even very small cars (Daihatsu Move), are now fitted with
an adaptive cruise control (ACC) system that is capable of measuring and maintaining a driver-preset
headway to the vehicle ahead by automatic modulation of the engine control, and if required,
automatically applying brakes up to a maximum deceleration of 0.3g (as per ISO standard). If no
vehicle is ahead, the vehicle maintains the desired “set-speed”. ACC can be ordered as an option for
new vehicles. At least three heavy truck manufacturers offer this feature on their vehicles.
Theoretically, a vehicle equipped with modern braking technology and adaptive cruise control is
equipped with the basic building blocks for a simple (braking only – no steering) collision avoidance
system that would be capable of detecting when a collision is likely to occur and applying emergency
braking to avoid it. More advanced and/or multiple sensors are likely to be required as well as
considerable further development before full collision avoidance systems (other than low speed
systems) are available in production. However, collision mitigation systems are already on the market,
providing limited automated braking capability and some systems are available that can automatically
avoid collisions in low speed traffic.
Introduction
Vehicle technology has increased rapidly in recent years, particularly in relation to braking systems
and sensing systems. The widespread introduction of anti-lock braking systems (ABS) has provided
the building blocks for a wide variety of braking control systems. Additional hardware that allows
brake pressure to be increased above pedal demand as well as to be reduced, combined with additional
software control algorithms and sensors allow traction control (TC), electronic brake force
distribution (EBD), brake assist (BAS) and electronic stability control (ESC) functions to be added.
In parallel to the development of braking technologies, sensors have been developed that are capable
of detecting physical obstacles, other vehicles or pedestrians around the vehicle. Many luxury, mid-
size and small cars in Europe, and in Japan even very small cars (Daihatsu Move), are now fitted with
an adaptive cruise control (ACC) system that is capable of measuring and maintaining a driver-preset
headway to the vehicle ahead by automatic modulation of the engine control, and if required,
automatically applying brakes up to a maximum deceleration of 0.3g (as per ISO standard). If no
vehicle is ahead, the vehicle maintains the desired “set-speed”. ACC can be ordered as an option for
new vehicles. At least three heavy truck manufacturers offer this feature on their vehicles.
Theoretically, a vehicle equipped with modern braking technology and adaptive cruise control is
equipped with all of the necessary hardware to allow a simple (braking only – no steering) collision
avoidance system that would be capable of detecting when a collision is likely to occur and applying
emergency braking to avoid it. Collision mitigation systems are already on the market, providing
limited braking capability.
Research methods
The scope of this project allowed for no test or simulation of the actual performance of current
generation automatic emergency braking systems (AEBS). The project has aimed to assess systems
based on:
• Review of scientific literature;
• Gathering information from industry;
• Analysis of accident data;
• Simulation of potential implications of reduced accident severity on congestion costs;
• Cost benefit analysis.
An extensive review of literature was carried out. This included marketing and promotional
information from manufacturers on AEBS and other active safety systems that they sold or were
developing as well as scientific papers on the technical behaviour and development of such systems
and technical standards, regulations and guidelines and research papers on the effectiveness of
systems.
The project has been carried out in an open manner with industry involvement at several stages.
Representatives of the automotive industry and other interested stakeholders were invited to the three
main project meetings at inception, mid-point and final. In addition to input provided at these
meetings, attendees were asked to complete two separate surveys. The first requested detailed
information about the technical characteristics and performance of AEBS systems that were either in
production or under development. The respondents included vehicle manufacturers and tier one
suppliers and was widely distributed via the relevant trade bodies (e.g. ACEA, JAMA, CLEPA). The
second survey was sent to the same respondents in a similar manner and asked for comments on a
proposal for generic characteristics of systems to be tested against accident data to estimate benefits
and to request information concerning the cost of the systems for use in the cost benefit analysis.
Collision avoidance
There are no full collision avoidance systems that function at high speed fitted to production vehicles
at present however such systems are under development and prototype systems are undergoing
evaluation. Some new vehicles are equipped with systems that will fully avoid collisions but these
only function in low speed circumstances.
Matsumoto et al (2001) describe the accident avoidance technologies on the Nissan Advanced Safety
Vehicle (ASV) 2. Automatic braking decelerates the vehicle to a stop or reduces the collision speed as
much as possible in the event the driver is slow to brake or does not brake sufficiently in relation to an
obstacle ahead. Active brake control for emergency manoeuvring optimises the braking force at each
wheel and comprehensively controls vehicle behaviour.
In a situation where there is an increased risk of a collision with an object in front of the host vehicle,
such as a stopped vehicle, on account of human error due to the driver’s inattention or misjudgement,
the driver is alerted to the potential danger by audible and visual warnings. Should the driver fail to
manoeuvre around the obstacle automatic braking is applied to reduce the impact speed. If the driver
brakes to decelerate in this case, the driver’s operation is given first priority. However the system
continues to control the brakes if the driver’s action does not decelerate the vehicle sufficiently to
achieve maximum possible collision avoidance.