25-10-2016, 04:13 PM
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INTRODUCTION
Cruise control system one of the advanced system and has become a common feature in automobiles nowadays. Instead of driver frequently checking out the speedometer and adjusting pressure on the throttle pedal or the brake. Cruise control system takes over the control the speed of the car by maintaining the constant speed set by the driver. Therefore, this system can help in reducing driver’s fatigue in driving a long road trip.
In the process of the cruise control system: Firstly, the driver sets the desired speed of the car by turning on the cruise control mode at the desired speed, such that the car is travels at the set speed and hits the button. An alternate way to set the desired speed of the car is by tapping the set/acceleration button to increase the speed of the car or by tapping the coast button to decrease the speed of the car.
Secondly, the processing unit in the system receives the input signal, and progress the output signal to the actuator. Thirdly, the actuator adjusts the throttle position according to the command of controller. Finally, the changes in the throttle position leads to the change in the speed of the car travelling and obtains the desired speed. The actual speed of the car is continuously monitored by a sensor and fed
to the processor. The process of transmitting the current speed of the car continues to the processor to maintaining the desired speed, as long as the cruise control is engaged.
Following sections are classified as described in below. In section II modeling of vehicle dynamics is discussed. Conventional control system is explained in section III. Complete system described in section IV. Simulink model developed and results are discussed in section V and finally concluded in section VI.
VEHICLE MODELING DYNAMICS
2.1 Physical Model
Normally, the inertia of the wheels of the car is neglected. Assuming the friction of the car is obtained by the friction caused by the motion of the car. A physical model of the cruise control system is illustrated as shown in Fig. 2.1. The m indicated as the mass of a car.
CONVENTIONAL CONTROL SYSTEM
3.1 Adaptive Cruise Control
Adaptive Cruise Control (ACC) is an advancement of cruise control system. It’s an automotive feature allows the vehicle to adopt set vehicle's speed to the traffic environment. A sensor system is attached to the front of the vehicle which is used to detect former slow moving vehicles are in the ACC vehicle's path. If a foregoing slow moving vehicle detected by the sensor system in the ACC vehicle’s path, then the ACC system will automatically adopts the former vehicle speed and control the vehicle speed according to clearance, or time gap, between two vehicles. If the system detects that the ahead vehicle gets higher speed than ACC vehicle cruise speed or no longer in the ACC vehicle's path, then automatically ACC system will stimulate back the vehicle speed to its pre-set cruise control speed. This action of control system allows the ACC vehicle to self-governing slow down and speeds up with traffic without arbitration from the driver. Normally ACC vehicle speed is controlled with the following systems, that is, engine throttle control and limited brake operation
Stop and Go manoeuvres
Commercial systems capable of stopping the vehicle when a collision is imminent at speeds below15 km/h have been developed by car manufacturers, but their dependence on the human driver to restart the vehicle might cause traffic jams. Thus, autonomous intelligent driving in traffic jam conditions is one of the most challenging topics of large city traffic management. These kinds of system are known in the literature as stop-and-go systems . They deal with the vehicle in urban scenarios with frequent and sometimes hard braking and acceleration. The main idea of these control systems is to regulate the vehicle around the well-known 2-s headway rule, which attempts to maintain a distance proportional to the human reaction time (approximately 2 s) as in Fig. 3.2. Some approaches have tried to reproduce human behaviour with deterministic models in order to achieve smooth control actions.
CONCLUSION
Stop-and-go manoeuvres constitute one of the most important and as yet unsolved topics in the automotive sector. Yet this paper proposed ACC for stop and go manoeuvres of an intelligent Vehicle using hybrid PID controller. The Proposed method provides distance and speed tracking as well as providing the smooth variation of the vehicle acceleration.