ADAPTIVE CRUISE CONTROL SYSTEM -An overviewBy Nikhil R

CONTENTS:-

INTRODUCTIONPRINCIPLE OF ACC PHYSICAL OVERVIEWDEFINITIONS/TERMINOLOGIESCOMPONENTS OF ACC SYSTEMCONTROL SYSTEM INTERFACEPHYSICAL LAYOUT OF AN ACC

SYSTEMADVANTAGES DISADVANTAGESAPPLICATIONSCONCLUSION

INTRODUCTION:-

What is Adaptive Cruise Control? Adaptive Cruise Control (ACC) is an automotive feature that allows a vehicle's cruise control system to adapt the vehicle's speed to the traffic environment. A radar system attached to the front of the vehicle is used to detect whether slower moving vehicles are in the ACC vehicle's path.

Introduced in 1970’s in USA. This system is now available in luxury cars like Mercedes S-class, Jaguar XJ, Volvo trucks etc…

PRINCIPLE:-

How does it work?If a slower moving vehicle is detected, the ACC system will slow the vehicle down and control the clearance, or time gap, between the ACC vehicle and the forward vehicle. If the system detects that the forward vehicle is no longer in the ACC vehicle's path, the ACC system will accelerate the vehicle back to its set cruise control speed. This operation allows the ACC vehicle to autonomously slow down and speed up with traffic without intervention from the driver. The method by which the ACC vehicle's speed is controlled is via engine throttle control and limited brake operation.

PHYSICAL OVERVIEW:-

DEFINITIONS:- Adaptive Cruise Control (ACC) – An

enhancement to a conventional cruise control system which allows the ACC vehicle to follow a forward vehicle at an appropriate distance.

ACC vehicle – the subject vehicle equipped with the ACC system.

Active brake control – a function which causes application of the brakes without driver application of the brake pedal.

Clearance – distance from the forward vehicle's trailing surface to the ACC vehicle's leading surface.

Forward vehicle – any one of the vehicles in front of and moving in the same direction and traveling on the same roadway as the ACC vehicle.

Set speed – the desired cruise control travel speed set by the driver and is the maximum desired speed of the vehicle while under ACC control.

Target vehicle – one of the forward vehicles in the path of the ACC vehicle that is closest to the ACC vehicle.

Time gap – the time interval between the ACC vehicle and the target vehicle. The 'time gap' is related to the 'clearance' and vehicle speed by:

time gap = clearance / ACC vehicle speed

Different STATES (MODES) in ACC System-

ACC off mode ACC standby mode ACC active mode. This consists of the following 2 modes-

ACC speed control mode ACC time gap control mode

COMPONENTS OF AN ACC SYSTEM:- 1) ACC Module – The primary function of the ACC module is to process the radar information and determine if a forward vehicle is present.2) Engine Control Module – The primary function of the Engine Control Module is to receive information from the ACC module and Instrument Cluster and control the vehicle's speed based on this information.3) Brake Control Module – The primary function of the Brake Control Module is to determine vehicle speed via each wheel and to decelerate the vehicle by applying the brakes when requested by the ACC Module.4) Instrument Cluster – The primary function of the Instrument Cluster is to process the Cruise Switches and send their information to the ACC and Engine Control Modules.

5) CAN – The Controller Area Network (CAN) is an automotive standard network that utilizes a 2 wire bus to transmit and receive data. Each node on the network has the capability to transmit 0 to 8 bytes of data in a message frame.

6) Cruise Switches – The Cruise Switches are mounted on the steering wheel and have several buttons which allow the driver to command operation of the ACC system. The switches include:On : place system in the 'ACC standby' stateOff : cancel ACC operation and place system in the 'ACC off' stateSet + : activate ACC and establish set speed or accelerateSet - : decelerateRes : resume to set speedCoast: To decelerate or cancel the ACC system

Cruise control switch

Mounted on steering wheel

7) Brake Switches (BS) – There are two brake switches, Brake Switch 1 (BS1) and Brake Switch 2 (BS2). When either brake switch is activated, Cruise Control operation is deactivated and the system enters 'ACC standby' state.

8) Brake Lights – When the Brake Control Module applies the brakes in response to an ACC request, it will illuminate the brake lights to warn vehicles behind the ACC vehicle that it is decelerating.

9) Sensors/Radars – Currently 4 types of radars are available. They are-

LIDAR (Light Detection and Ranging) RADAR ( Radio Detection and Ranging) VISION SENSORS ULTRASONIC SENSOR

LIDAR- The first ACC system introduced by Toyota used this method. By measuring the beat frequency difference between a Frequency Modulated Continuous light Wave (FMCW) and its reflection.

RADAR- RADAR is an electromagnetic system for the detection and location of reflecting objects like air crafts, ships, space crafts or vehicles. It is operated by radiating energy into space and detecting the echo signal reflected from an object (target). Most of the current ACC systems are based on 77GHz RADAR sensors. The RADAR systems have the great advantage that the relative velocity can be measured directly, and the performance is not affected by heavy rain and fog.

JEEP GRAND CHEROKEE ADAPTIVE CRUISE CONTROLSENSOR PLACED BELOW THE

GRILL

FUSION SENSOR- The new sensor system introduced by Fujitsu Ten Ltd. and Hondathrough their PATH program includes millimeter wave radar linked to a 640x480 pixel stereo camera with a 40 degree viewing angle. These two parts work together to track the car from the non-moving objects. While RADAR target is the car’s rear bumper, the stereo camera is constantly captures all objects in its field of view.

CONTROL SYSTEM INTERFACES:-

PHYSICAL LAYOUT OF ACC SYSTEM:-

ADVANTAGES:-

1. The driver is relieved from the task of careful acceleration, deceleration and braking in congested traffics.

2. A highly responsive traffic system that adjusts itself to avoid accidents can be developed.

3. Since the braking and acceleration are done in a systematic way, the fuel efficiency of the vehicle is increased.

DISADVANTAGES:-1.A cheap version is not yet realized.

2.A high market penetration is required if a society of intelligent vehicles is to be formed.

3.Encourages the driver to become careless. It can lead to severe accidents if the system is malfunctioning.

4.The ACC systems yet evolved enable vehicles to co-operate with each other vehicles and hence do not respond directly to traffic signals.

APPLICATIONS:- Mitsubishi was the first automaker to offer a laser-based

ACC system in 1995 on the Japanese Mitsubishi Daimante.

In August 1997, Toyota began to offer a "radar cruise control" system on the Celsior.

Mercedes Benz introduced “DISTRONIC” in late 1998 on the S-Class. For 2006, they refined the system to completely halt the car if necessary . No called “DISTRONIC PLUS” available in E-class and S-class luxury sedans.

Jaguar began offering this system in 1999.

BMW’s Active Cruise Control system launched in 2000 in 7-series.

Volkswagen and Audi introduced their own systems in 2002.

CONCLUSION:-The accidents caused by automobiles are injuring lakhs of people everyyear. The safety measures starting from air bags and seat belts have nowreached to ACC, SACC and CACC systems. The researchers of IntelligentVehicles Initiative in USA and the Ertico program of Europe are working ontechnologies that may ultimately lead to vehicles that are wrapped in a cocoonof sensors with a 360 –degree view of their surroundings. It will probably takedecades, but car accidents may eventually become as rare as plane accidents arenow, even though the road laws will have to be changed, up to an extent sincethe non-human part of the vehicle controlling will become predominant.

Thank you