Adoptive Adoptive cruise control system
1. Introduction Adaptive Cruise Control (ACC) technology improves the function of standard cruise control by automatically adjusting the vehicle speed and distance to the vehicle ahead. This is achieved using a long range radar sensor, a signal processor and longitudinal control of the vehicle. If the vehicle ahead slows down, or if another object is detected, the ACC adjusts vehicle speed and headway accordingly without any action on the part of the driver. Once the road is clear, the system will re-accelerate the vehicle back to the set speed. As with standard cruise control, the driver can override the system at any time. The current ACC systems are mainly comfort functions with a limited speed range. ACC with full speed range function will make the systems safer and eve n more convenient to use. If needed, the system will slow the vehicle down to a standstill, using its full braking power, instead of turning off at a certain speed as is presently the case. This system will also recognise when the car in front starts to move again and will announce this to the driver, usually by acoustic signal. Then the vehicle will accelerate automatically automatically to the pre -selected speed while maintaining the correct distance to the vehicle ahead and adjust to the tempo of the traffic. The system detects sudden decelerations in the spinning of each wheel, and reduces the pressure on that brake until it again detects acceleration. It can do this very quickly, before the tyre can actually significantly change speed. The result is that the tyre slows down at the same rate as the vehicle, with the brakes keeping the tyres very near the point at which they will start to lock up. This gives the system maximum braking power.
2. Types: 2.1 Laser Based systems : They are significantly lower in costs than the
RADAR based systems. However, laser based systems do not detect and track vehicles well in adverse weather conditions and the heavy dirty vehicles. Laserbased sensors must be exposed, the sensor (a fairly-large black box) is typically found in the lower grille offset to one one side of the vehicle vehicle . Lasers would be considerably considerably cheaper than radar, the the basic technology is that of 10$ laser pointer. Laser frequencies are also unregulated by governments governments and the ranges involved are just about right for the s tated purpose.
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Adoptive cruise control system
2.2 RADAR Based systems : They are higher cost than the laser Based system.
Radar based systems can work comparably well under the sun/dirt interference and reflector height requirements . Radar is RF, so the FCC an d other government agencies get involved. It also has greater range and you might get unexpected effects from refraction and reflection of multiple sources.
3.
A CC vehicle relationship.
Fig. ACC Vehicle relationship
ACC vehicle ± the subject vehicle equipped with the ACC system . 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 travelling on the same roadway as the ACC vehicle . 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.
4. A CC system states: 2
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Adoptive cruise control system
ACC off state ± direct access to the 'ACC active' state is disabled. ACC standby state ± system is ready for activation by the drive r. ACC active state ± the ACC system is in active control of the vehicle's speed. ACC speed control state ± a sub state of 'ACC active' state in which no forward Vehicles are present such that the ACC system is controlling vehicle speed to the 'set speed' as is typical with conventional cruise control systems. ACC time gap control state ± a sub state of 'ACC active' state in which time Gap, or headway, between the ACC vehicle and the target vehicle is being Controlled.
Fig. ACC states
Before the cruise control can be engaged the driver must enter the µACC standby¶. This can be done by the driver by pressing the ACC µon¶ Button. The driver can enter the µACC active¶ state by pressing the µset¶ or µresume¶ button provided on the steering. The following conditions must satisfied before the vehicle enter into a µACC active state¶: y y
5.
Brakes should not be applied. Vehicle speed>=25mph.
Operating Modes:
There are two modes in which the ACC can be operated. peed control mode. Follow control mode.
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Adoptive cruise control system
5.1
Speed control mode.
Operation during this mode is equivalent to that of conventional speed control. If no forward vehicle is present within the Time Gap or clearance of the system, the vehicle's speed is maintained at the target speed. The engine control system controls the engine output via throttle control to maintain the vehicle speed at the target speed .
5 .2
Follow control mode.
The ACC system enters follow mode or 'ACC time gap control' if the radar detects a forward vehicle at or within the clearance distance. During this mode of operation, the ACC system sends a target speed to the Engine Control Module and deceleration commands to the Brake Control module to maintain the set time gap between the vehicles .
Acceleration control : ACC system accelerates the vehicle by increasing the target speed sent to the engine control m odule. 5.2.1
Deceleration control: The ACC system decelerates the vehicle by lowering the target speed sent to the Engine Control Module and sending a brake deceleration command to the Brake Control Module. 5.2.2
5.2.3
Slowing moving or stopped vehicle: The clearance between the ACC
vehicle and the forward vehicle may be rapidly decreasing or the minimum vehicle speed of 25 [mph] may be r eached Under these situations the ACC System enters into 'ACC standby' and alerts the driver by displaying a "Driver Intervention Required" text message on the display and by turning on an audible chime. 6.
Cancelling Cruise Operation: Cruise Control operation may be cancelled by the operator or automatically via the ACC system. Either of the following conditions will deactivate ACC: Brake pedal is pressed 'Off' button is pressed Vehicle Speed < 25 mph An ACC system fault is detected. y y y y
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Adoptive cruise control system
7 . Conclusion:
Adoptive cruise control can provide the enhanced security using the RADAR based collision avoidance systems. Due, to these highway accidents can be minimized. It can provide the better fuel efficiency. So this technology needs to implement in the present generation cars, which can enhance the comfort in drive.
8.
References. y y y
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http://en.wikipedia.org/wiki/Cruise_control http://en.wikipedia.org/wiki/Adaptive_cruise_control http://www.boschengineering.com/en/whatweprovide/serviceareas/safetyandcomfort/driver assistancesystems/acc-adaptive-cruise-control.aspx. http://delphi.com/manufacturers/auto/safety/active/adaptive -cruisecontrol/ http://media.ford.com/images/10031/Adaptive_Cruise.pdf
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