Research On The Application Of Automobile Cruise Technology In Highway Limit Speed System

At present, Chinese economy is raising fast, which accompanied with a booming rate of cars. More and more cars are making the existing road system overcrowded, especially when the traffic condition is complicated. Furthermore, the places such as roundabout, curves of roads, the area of school and etc., where are highly populated and the road condition is unforeseeable. If over speed causing accidents in such mentioned areas, the outcome is frightened. Common speed control includes:warning signs and speed supervision that operated by police or officials, the mentioned methods are all passive speed limitation. Due to the disadvantage of passive speed limitation, the active highway limit speed system is born. The system is able to control the speed of the vehicle automatically that drives on the edge of the maximum limited speed in different speed zones with a good reputation for reliability. Meanwhile, according to the certain road condition, the speed limit is able to be cancelled or rested. By doing so, the flexibility is increased without losing reliability of the entire system. The highway limit speed system is an intelligent traffic control system, which includes which composed by two subsystems that is the speed recognizing system and the vehicle speed control system. Above all, the critical part of the entire system is to control the vehicle steadily while it is cruising on the road. The thesis explains the vehicle speed control system that is based on the entire highway limit speed system.The existing speed control system using simple boundary control strategy, which means when the vehicle reaches to its maximum speed level, the system takes over the control; while the speed is far below the limited speed level, the system stops response. This method is indeed not complex at all, however due to the driver pushes the accelerator pedal unevenly, the actual effect is not ideal. During the traditional speed control period, the speed is reduced shortly, but because the accelerator pedal is still locked in the same position by the driver, the vehicle reenters the acceleration once again, the entire process may lead the speed changes in such a short period of time, finally causes the vehicle speed is not stable and smooth.In order to solve the problem, the thesis offers a speed control system that based on cruise technology. The system adopts continuous control strategy to control the speed, during the speed control period, by overtaking the throttle temporally, to avoid human errors that caused by the driver; and by controlling the electric throttle continuously, instead of controlling the accelerator pedal, to make the vehicle in cruising status, to maintain the vehicle under the maximum allowed speed, to achieve the speed control smoothly.In order to maintain the vehicle’s fastest speed in the restrict area, the speed control strategy was researched, and two controllers were designed:the fuzzy PID controller and the BP neural network adaptive controller. An ordinary manual car was taken as a reference sample, furthermore, electric throttle, engine, transmission system and movement parts were combined as a vehicle portrait dynamics simulation model. By establishing the simulation model under the MATLAB/SIMULINK circumstance, and furthermore analyzing the system, finally comparing the results from two different controllers.The experiment result testifies that while the speed of a vehicle reaches the maximum limited speed in a certain road section, both2types of controllers are able to regulate the speed of a vehicle within the maximum allowed speed; however, considering the complexity, applicability and controlling effects, all factors indicate that fuzzy PID algorithm controller is far more superior to self-adapted PID algorithm controller that based on BP neural network. Due to the entire speed control process is taken automatically and continuously, without human’s intervention the vehicle has no more unstable re-acceleration or re-deceleration that caused by human control, therefore a smooth and stable speed limit control is achieved.Based on the simulation and using the80C196KC chip as the fundamental part, the design of software and hardware of vehicle speed control system were offered. To hardware, the thesis analyzes and explains the design principle in detail, a circuit diagram is attached. In the circuit diagram part, not only explains the external memory of singlechip, but also explains the signal processing circuit, communication circuit, voltage-stabilizing circuit, and drive circuit. To software, the design concepts are illustrated according to the features of80C196KC chip, which include main program, signal acquire program, fuzzy PID control program and the flow chart of PID control.