11-02-2013, 12:17 PM
FULL REPORT ON ADAPTIVE CRUISE CONTROL
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INTRODUCTION
Every minute, on an average, at least one person dies in a crash. All told, the hospital bills, damaged property, and other costs will add up to 1-3 percent of the world's gross domestic product. And, of course, the losses that matters most are not even captured by these statistics, because there's no way to put a money value on them. The main factor for accidents is human error and other factors which Influences are traffic density, vehicle speeds and weather conditions. There are various driver assistance systems which help the driver in accident free driving. This report discuss about adaptive cruise control which contains following features:
This Adaptive Cruise Control system is adapted in India in some of the cars like Mercedes Benz, Infiniti etc.
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. 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.
Features of ACC
• By automatically accelerating or decelerating the host vehicle to maintain a set headway distance to a preceding vehicle, the ACC system can help to coordinate driving behavior with the flow of traffic and also reduce driver fatigue and stress.
• It is a highly practical system with ample braking capability because it can control both the throttle and the brakes when decelerating the host vehicle.
• Moreover, the braking control function provides smooth deceleration comparable to that ordinarily obtained when the driver decelerates a vehicle.
• The range of conditions under which the system can be used has been expanded by adopting millimeter-wave radar, which is capable of recognizing forward traffic regardless of rain or other inclement weather conditions.
• Ability to track a car in the lane ahead using forward-looking radar. If the distance to a vehicle in front is below a pre-set value, the ACC system is designed to slow the car down, using brakes if required, to track the speed of the vehicle in front, then returning the car to its pre-set speed once the lane ahead is clear.
• Intelligent lane prediction using steering angle and yaw rate sensors predict curves in the road, and to ensure that any vehicle ahead being tracked is in the same lane as the car itself.
1.4 Physical layout and constituents of an ACC system
As shown in figure 2.2, the ACC system consists of a series of interconnecting components and systems. The method of communication between the different modules is via a serial communication network known as the Controller Area Network (CAN).
ACC Module
The primary function of the ACC module is to process the radar information and determine if a forward vehicle is present. When the ACC system is in 'time gap control', it sends information to the Engine Control and Brake Control modules to control the clearance between the ACC Vehicle and the Target Vehicle.
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. The Engine Control Module controls vehicle speed by controlling the engine's throttle valve.
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. The braking system is hydraulic with electronic enhancement, such as an ABS brake system, and is not full authority brake by wire.
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. The Instrument Cluster also displays text messages and telltales as shown in figure 2.4 for the driver so that the driver has information regarding the state of the ACC system.
CONCLUSION
Active cruise control and its radar unit could also bring the auto industry closer to the electronic cocoon. In theory, the cocoon is a blanket of technology and sensors that protects the car and its occupants. These features, using radar, could include such things as automatic braking to avoid a collision to warning a driver who is about to pass that another vehicle is in the blind spot.
One of the potential advantages of ACC is the foundation that it provides for next generation advancements. In time you will have a sensor field around the car, which will be used by the vehicle's intelligence. It's the beginning of the microwave era in automotive electronics.