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ADAPTIVE CRUISE CONTROL

SYSTEM

VISHWANATH HIREGOUDAR

DEPARTMENT OF MECHANICAL ENGINEERINGDAYANANDA SAGAR COLLEGE OF ENGINEERING, BANGALORE,

KARNATAKAvgh2020@gmail.com

ABSTRACT

ACC is an extension of conventional

cruise control system. An ACC systemis a driver convenience system which

automatically adjusts the vehicle

speed and distance to that of a targetvehicle. ACC uses a long range

RADAR/LIDAR sensor to detect a

target vehicle up to 200 meters infront and automatically adjusts the

ACC vehicle speed and gapaccordingly. ACC automatically

decelerates or accelerates the vehicle

according to the desired speed and

distance settings established by thedriver. The RADAR/LIDAR sensors

are located under or behind the front

bumper or behind the grille.

1.INTRODUCTIONA typical conventional cruise controlsystem is basically a speed control

system of a vehicle. It controls the

vehicle speed by adjusting throttleposition to maintain a speed set by the

driver. A control unit compares the

actual vehicle speed and the desiredset speed. If there is a difference

between these two values, a signal issent to a throttle position actuator to

adjust the throttle position to bring the

vehicle to the set speed. Depending on

the vehicle make and model, throttleposition is achieved using vacuum

powered or electronically controlled

actuators.

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2.ACC VEHICLE RELATIONSHIP

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3.ACC SYSTEM STATES ACC off state- direct access to

the ACC active state is

disabled.

ACC standby state- system isready for activation by the

driver.

ACC active state- the ACCsystem is in active control of

the vehicles speed.

ACC speed control state- its anACC active state in which no

forward vehicles are presentsuch that the ACC system is

controlling vehicle speed to the

set speed as is typical with

conventional cruise controlsystems.

ACC time gap control state- itsan ACC active state in whichtime gap or headway between

the ACC vehicle and the targetvehicle is being controlled.

ACC States and Transitions

4.FEATURES OF ACC Maintains a safe, comfortable

distance between vehicles

without driver interventions.

Maintains a consistentperformance in poor visibilityconditions.

Maintains a continuousperformance during road turnsand elevation changes.

Alerts drivers by way ofautomatic braking.

5.OPERATIONALOVERVIEW

The driver interface for the ACC

system is very similar to aconventional cruise control system.

The driver operates the system via aset of switches on the steering wheel.

The switches are the same as for a

conventional cruise control systemexcept for the addition of two

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switches to control the time gap

between the ACC vehicle and thetarget vehicle. In addition there are a

series of text messages that can be

displayed on the instrument cluster toinform the driver of the state of the

ACC system and to provide anynecessary warnings. The driver

engages the ACC system by firstpressing the ON switch which places

the system into the 'ACC standby'

state. The driver then presses the Setswitch to enter the 'ACC active' state

at which point the ACC system

attempts to control the vehicle to thedriver's set speed dependent upon thetraffic environment.

When there is no other vehiclein front, the vehicle keeps

moving at the pre set speed.

Once the target vehicle isdetected in front by the distancesensor, the ACC equipped

vehicle slows down and

maintains a safe distancebetween itself and the target

vehicle.

Now the ACC equipped vehiclekeep moving at the set distancebetween the vehicles.

Once the target vehicle movesout of the radar range, the ACCequipped vehicle accelerates to

the set speed.

6.LASER/RADARCOMPARISON

Both laser and radar basedACC sensors operate by

projecting a beam forward todetect a vehicle ahead.

Radar based units transmit amillimeter wave radar signaland receive the reflected signalfrom the vehicle ahead.

Laser based units transmit laserbeam pulses that are reflected

back by the vehicle ahead.

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Bad weather may limit theeffectiveness of a laser baseddistance sensor.

The information received by thedistance sensor is used to measure thegap between the ACC vehicle and the

vehicle ahead and determine the speed

of the forward vehicle.

6.1LASER BASED SYSTEM

6.2 RADAR BASED SYSTEM

Physical layout

7.PHYSICAL LAYOUTAs shown in Figure, the ACC systemconsists of a series of interconnectingcomponents and systems. The method

of communication between thedifferent modules is via a serial

communication network known as theController Area Network (CAN).

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ACC ModuleThe primary functionof the ACC module is to process the

radar information and determine if a

forward vehicle is present. When theACC system is in 'time gap control', it

sends information to the EngineControl and Brake Control modules to

control the clearance between theACC Vehicle and the Target Vehicle.

Engine Control Module Theprimary function of the Engine

Control Module is to receive

information from the ACC moduleand Instrument Cluster and control thevehicle's speed based on this

information. The Engine Control

Module controls vehicle speed bycontrolling the engine's throttle.

Brake Control ModuleThe primaryfunction of the Brake Control Module

is to determine vehicle speed via each

wheel and to decelerate the vehicle byapplying the brakes when requested

by the ACC Module. The brakingsystem is hydraulic with electronic

enhancement, such as an ABS brake

system, and is not full authority brake

by wire.

I nstrument Cluster The primary

function of the Instrument Cluster isto process the Cruise Switches and

send their information to the ACC and

Engine Control Modules. TheInstrument Cluster also displays text

messages and telltales for the driverso that the driver has information

regarding the state of the ACC

system.

CANThe Controller Area Network

(CAN) is an automotive standardnetwork that utilizes a 2 wire bus to

transmit and receive data. Each nodeon the network has the capability to

transmit 0 to 8 bytes of data in amessage frame. A message frame

consists of a message header,

followed by 0 to 8 data bytes, andthen a checksum. The message header

is a unique identifier that determines

the message priority. Any node on thenetwork can transmit data if the bus isfree. If multiple nodes attempt to

transmit at the same time, an

arbitration scheme is used todetermine which node will control the

bus. The message with the highest

priority, as defined in its header, willwin the arbitration and its message

will be transmitted. The losing

message will retry to send its messageas soon as it detects a bus free state.

Cruise Switches The Cruise

Switches are mounted on the steering

wheel and have several buttons whichallow the driver to command

operation of the ACC system. The

switches include:

'On': place system in the 'ACCstandby' state

'Off'': cancel ACC operationand place system in the 'ACCoff' state

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'Set +': activate ACC andestablish set speed or accelerate

'Coast': decelerate 'Resume': resume to set speed 'Time Gap +': increase gap 'Time gap': decrease gap

* These switchesdepend on manufacturer and

technology use.

Br ake SwitchesThere are two brakeswitches, Brake Switch 1 (BS1) and

Brake Switch 2 (BS2). When either of

the brake switch is activated, CruiseControl operation is deactivated andthe system enters 'ACC standby' state.

Brake Lights When the BrakeControl Module applies the brakes in

response to an ACC request, it willilluminate the brake lights to warn

vehicles behind the ACC vehicle thatit is decelerating.

8.SYSTEM INHIBITIONCertain conditions may prevent the

ACC from engaging.

An activated ABS.

Detected instability, activatingthe traction/stability controlsystem.

Brakes overheated signal fromthe ABS control module.

Sensor obstruction from paint,stickers, a vehicle front

protector, excessive mud, snow,

etc.

Vehicle speed too high or toolow.

Rear of forward vehicleextremely dirty or has no

reflectors.

To ensure that the ACC systemfunctions properly, the distance sensor

should be kept clean. Wipe with a soft

cloth, being careful to avoid damage

to the sensor.

9.FUSION SENSORFusion sensors are the latest type of

sensors used in ACC system

introduced by Fujitsu Ten Limitedand Honda.

Fusion sensor is a combination ofsensors and processors. The Fusion

sensor consists of the following

components-

Millimeter-wave radar Stereo camera Image processor Fusion processor

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A prototype of car

with Fusion sensor arr angement

Block diagram of

sensing and contr oll ing process

10. NEXTGENERATIONS OFACC

Stop and GO Cruise Control(SACC)

Co-operative Adaptive CruiseControl (CACC)

10.1 Stop and GO CruiseControl (SACC)

Ordinary ACC systems maintain asafe distance between cars at speeds

above 40km/hr, whereas SACC will

work primarily at lower speeds inheavy traffic. If the car in front stops,it will bring the vehicle to a complete

stop. Then it will not re-engage thethrottle, thats up to the driver but as

soon as the throttle is engaged, it willaccelerate and decelerate along with

the leading car over any range of

speeds between zero and the cruising

speed set by the driver.

10.2 Co-operative AdaptiveCruise Control (CACC)

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ACC can only respond to a difference

between its own speed and the speedof the car ahead, while CACC will

respond to two or more cars to

communicate and work together toavoid a collision. Ultimately,

experiments say, the technology maylet cars to follow each other at

intervals as short as half a second. At100km/hr, that would amount to a

distance between cars of less than 14

meters (roughly two cars length)

11. ADVANTAGES Its usefulness for long drives

across sparsely polluted roads.

This usually results in betterfuel efficiency.

Some drivers use it to avoidunconsciously violating speed

limits.

Reduction in accident rate forvehicles fitted with collisionavoidance type systems.

Reduction in driver fatigue. Interconnection to more

advanced future systems.

12. LIMITATIONS One of the biggest challenges

in designing ACC systemstoday are the costs associated

with the robust system. Thoughcurrent costs are substantial,

they are slowly decreasing.

Encourages the driver tobecome careless. It can lead tosevere accidents if the system is

malfunctioning.

13. CONCLUSIONThe accidents caused by automobilesare injuring lakhs of people every

year. The safety measures startingfrom Air bags, seat belts and ABS

have now reached to ACC, SACC and

CACC systems. The researchers of

Intelligent Vehicles Initiate in USAand the Ertico program of Europe are

working on technologies that mayultimately lead to vehicles that are

wrapped in a cocoon of sensors with a360 degree view of their

surroundings. It will probably takedecades, but car accidents may

eventually become as rare as plane

accidents are now. Even the road lawswill have to be changed to someextent since the non-human part of the

vehicle controlling will becomepredominant.

REFERENCES

www.sunnyday.mit.edu/safety-club/workshop5/Adaptive_Cruise_Control_Sys_

www.eetimes.com www.webcache.googleusercont

ent.com

www.howstuffworks.com