Bryan Guzman A

8/3/2019 Bryan Guzman A

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Collision Mitigation break system

(CMS)

What is CMS?

How it worksSystem Configuration

Warning Devices

Collision Avoidance ManeuversConclusions


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References:

Honda Motor: Science & Education. Trends in

Japan 2003

Autoweb.com.au: Honda Develops New CollisionAvoidance Safety System. 2003

Francois Granet, Rosella Picado, Lauren Smith:

Longitudinal Avoidance. 2003


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What is CMS?

CMS is the world's first Collision MitigationBrake System (CMS). The technology predictsrear-end collisions and assists brake operation toreduce the impact.

CMS anticipates a collision based on drivingconditions, distance to the vehicle ahead andrelative speeds. It then uses visual and audiowarnings to prompt the driver to take preventativeaction and also initiates braking if the driver failsto respond to the warnings.


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How it Works?

First, the radar measures the distance between the car andother vehicles up to 100 meters ahead and any differencesin speed, and an onboard computer judges the risk of a

collision based on this information and on data about thecourse of the car.

Then if the system judges that there is a risk of a crash,such as when the car gets too close to the vehicle in front,it alerts the driver by sounding an alarm and lighting up a

BRAKE warning on the dashboard. This is the firstwarning stage, aimed at alerting the driver to the dangerand encouraging the driver to slow down.


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The system works in conjunction with the "E-Pretensioner"

seatbelt retraction system. If the car continues to get closer

to the other vehicle and the computer decides that it will be

hard to avoid a collision, it tightens the seatbelt more

firmly and applies the brakes forcibly and hard.

The CMS has three staged modes:

An audible warning,

An audible warning, light braking and light seat-belt

retraction.An audible warning, strong braking and strong seat-belt

retraction.


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CMS configuration:

Millimeter-wave radar: Detects vehicles within a rangeof about 100 meters ahead, in a 16-degree arc.

Sensors: The system determines driving conditions using arange of sensors that detect factors such as yaw rate,steering angle, wheel speed, and brake pressure.

CMS Electronic Control Unit (ECU): Based on distance

to the vehicle ahead and relative speed obtained from radarinformation, the ECU calculates the likelihood of acollision, and warns the driver, and in some cases activatesthe braking function.


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E-Pretensioner ECU: Sends instructions to the motorized

E-Pretensioner to retract the seatbelt, based on braking

instruction signals from the CMS ECU and electronically

controlled brake assist signals.

E-Pretensioner: Retracts the seatbelt using an internal

motor, based on instructions from the E-Pretensioner ECU.

Used in combination with conventional pretensioners.

Meter unit: Receives signals from the CMS ECU, and

warns the driver of potential danger using a buzzer and a

visual warning.


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Figure: Autoweb.com.au, CAS 2003


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CMS Warning Devices

Visual head-up displays: warnings are displayed on the

windshield in the driver's field of view.

Audio/Voice signals: auditory signals appear to be less

intrusive on driving tasks.


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CMS Collision Avoidance

Maneuvers:Headway distance control: the system warns the driver

whenever his/her car is following the leading car too

closely

Hazard warning: the system warns the driver of an object

within its projected path, so that the driver has sufficient

time to avoid a crash.

Automatic vehicle control: the system controls the

vehicle's brakes and steering wheel


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Precise breaks Actuator Systems

depend a lot on sensors:

Sensors fulfill the tasks of headway control andobstacle detection, which are the basis of Collision

Avoidance Systems (CAS) Sensing.


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SensorSensing

Ran eResolution

Directional

it

Response

TimeCost Size

Ultrasonics 10 m. (max) 10 mm. 30 deg. (min)speed ofsound $15

30 mm.diameter

PassiveInfrared 10 m. (max) poor 90 deg. 1sec. under $10

20 mm.square

Laser radar

(lidar)

100 m. (max),

0.5 m. (min) 1mm. (min) 1deg.

fast (10

msec.) over $50

50 mm. x 100

mm.

FMCW Radar 150 m. 10 mm.2 deg. or

wider fast (1msec) over $200250 mm. x 150

mm.

ImpulseRadar 50 m. (max) 10 mm. 25 deg. Fast (1msec) over $100

250 mm. x 100mm.

Capacitive 2 m. (max) 10 mm.

90 deg. Or

wider fast (1msec) $1 smallVisionSystems 100 m. poor good 100 msec. Over $200

40 mm. x 100mm.

Table 2

Sensor Devices' Measures of Performance

Source: Stobart and Upton, 1995


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Indicators:

Sensing range: the maximum range over which the

technique can be used

Resolution: the relative change in distance that can bemeasured

Directionality: the width of the beam over which the sensor

is sensitive

Response time: how quickly the sensor can respond to achange in distance


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Conclusion

Automatic braking systems can detect an obstacle and

bring the car to a complete halt just before impact. The

technology has reached the level where the systems can

even detect the speed of a vehicle in front, compare it withthe speed of the user's car, and stop the car to avoid an

accident. Honda and Toyota are applying and testing these

Automatic braking systems nowadays and will continue

improving this type of technology.

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