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1、华北科技学院毕业设计汽车防撞系统控制电路设计设计总说明 随着现代社会程度的高度发展,交通安全问题已成为各国亟待解决的重大课题。汽车的诞生，给人类生活带来了种种方便，同时车祸也给人类带来了很多阴影。交通事故已经成为现代社会的第一公害。根据戴姆勒一克莱斯勒公司的研究，如果驾驶员有 0.5 秒的额外警告时间，大约60%的后端碰撞事故是可以避免的，而提前 1 秒的警告则会避免 90%的后端碰撞事故。因而车辆防撞系统 (Collision Avoidance System，简称 CAS)有着重要的研究意义和应用空间。为了充分利用汽车为人类带来的种种方便，同时尽可能多的避免车祸带来的惨剧，研究和推广汽车防
2、撞装置日益显得重要和迫切。针对这种情况，设计一种响应快，可靠性高且较为经济的汽车防撞报警系统势在必行。因此本文设计了一种以超声波测距和 AT89C51 单片机为核心的汽车防撞报警系统，以期提高汽车运行的安全性，减少交通事故。 本系统将单片机的实时控制及数据处理功能与超声波测距技术、传感器技术相结合，较好的实现了汽车在运行过程中的障碍防撞，并可通过数码管显示距离，将障碍物距离和汽车在不同车速段的安全距离相比较，可发出声光警报。依据超声波测距原理，以 AT89C51 单片机为核心，设计了汽车防撞报警系统。 该系统将单片机的实时控制及数据处理功能与超声波测距技术、传感器技术相结合，以超声波发射和接受
3、电路、声光报警电路、测速电路等硬件电路为载体，通过编写的处理软件来实现测量距离。利用一片AT89C51单片机对超声波信号循环不断地进行采集。这个设计的汽车防撞系统能够连续测距，数据经过单片机的处理后，用4位数码管显示所测量得到的距离显示测量距离，当距离小于警戒阀值时，可发出声光报警信号。该系统可用于提高汽车在行进过程中与倒车时的安全性，构建汽车行进的安全空间。论文利用单片机AT89C51作为控制器,基于超声波测距原理和霍尔传感器CS3020测速的原理,设计了一个汽车防撞控制报警电路,并编写了对应的测速、测距，预警警告等程序。论文主要包括一下几个部分: （1）调研了国内外汽车防撞系统的现状以及发
4、展情况,提出了汽车防撞系统电路的总体设计方案。(2) 研究了单片机AT89C51的电路结构、引脚功能和工作原理,设计了基于单片机I(3) AT89C51的汽车测速、超声波的接收与发射、LED显示与声光报警的控制电路。 （3）利用渡越时间法进行超声波测距的基本原理，分析了影响超声波测距精度的几个重要因素，提出了采用 40kHz 的超声波作为测距载体和对系统测量误差影响较大的环境温度进行补偿的方案，提高了系统的测量精度和量程，设计制作了超声波测距的发射和接收两个模块。其中超声波发射电路主要由超声波换能器和反相器 74LS04 构成，单片机 P1.0 端口输出 40 kHz 间断方波。超声波接收电路
5、采用 SONY 公司的 CX20106A 为核心，对接收探头收到的信号进行放大、滤波。（4）显示电路采用简单实用的4位共阳LED数码管，用于显示车与障碍物的距离，由单片机P0.0P0.6接LED的ag七个笔段，P2.4P2.7接四位三极管的公共端，通过软件以动态扫描方式显示。（5）利用霍尔传感器CS3020测车速。霍尔车速传感器是一种基于霍尔效应的磁电传感器，具有对磁场敏感度高、输出信号稳定、频率响应高、抗电磁干扰能力强、结构简单、使用方便等特点。（6）声光报警电路由 NE555 电路、发光二极管、扬声器组成。汽车与障碍物之间的距离小于其车速段的安全距离时，AT89C51 单片机的P2.2 管
6、脚输出低电平， 经反相器到达 NE555 的 4 管脚时为高电平，NE555 开始振荡，发光二极管经三极管驱动点亮，同时，电容耦合滤除直流分量使扬声器发出报警声音。（7）对系统的软件设计进行介绍。在软件设计中采用不同模块不同编程进行设计的，设计分别对系统的主程序模块、中断子程序模块、超声波测距模块、声光报警模块。测速模块和数码管的显示模块的各个程序进行了设计。（8)利用Altium Designer进行原理图绘画和PCB板制作。 关键词：汽车防撞；超声波测距；AT89C51；测速；声光报警IIIInstructionWith the rapid development of modern so
7、ciety, the problems of traffic safety has become a major issue to be solved in the world. The birth of the car, brings convenience to human life, at the same time the accident also brought to mankind a lot of shadow. The traffic accident has become the first pollution in modern society. Based on the
8、 Daimler Chrysler, if the driver is 0.5 seconds of extra warning time, rear end collision accident about 60% can be avoided, and 1 seconds early warning will avoid rear-end collision accident 90%. Thus the vehicle collision avoidance system (referred to as CAS) has important research significance an
9、d application space. In order to make full use of a variety of convenient vehicle for mankind, at the same time as much as possible to avoid the accident caused the tragedy, anti-collision device research and promotion of car is becoming more and more important and urgent. In view of this situation,
10、 design a fast response, high reliability and a more economical vehicle collision warning system to be imperative. Therefore, this paper designed the collision warning system to an ultrasonic ranging and AT89C51 microcontroller as the core of the car, in order to improve the security of the automobi
11、le, reduce traffic accidents. The system computer real-time control and data processing functions and ultrasonic ranging technology, sensor technology, better implementation of the obstacles in the operation process of the automobile collision, and can display the distance through the digital tube,
12、the obstacle distance and vehicle at a safe distance from the different speed are compared, can send out audible and visual alarm. According to the principle of ultrasonic distance measurement, based on AT89C51 microcontroller as the core, design the anti-collision alarm system of automobile. The si
13、ngle chip real-time control and data processing and ultrasonic ranging technology, sensor technology combined with ultrasonic transmitting and receiving circuit, measuring circuit, an acousto-optic alarm circuit, hardware circuit as the carrier, through processing software to achieve the measurement
14、 distance. Circulating continuously to collect ultrasonic signal by using a AT89C51 single chip microcomputer. The design of the automobile anti-collision system capable of continuous measurement, data through the MCU after processing, the measured distance display measuring distance with 4 digital
15、tube display, IIIwhen the distance is less than the warning threshold, can send out audible and visual alarm signal. The system can be used to improve the car in the process of running and the safety of the car when the safety car, construction of space travel.The paper uses AT89C51 MCU as a control
16、ler, the principle of ultrasonic ranging principle and Holzer velocity measurement based on CS3020 sensor, the design of a vehicle anti-collision control alarm circuit, and compiled the corresponding velocity, distance, warning warning program. The author of this paper mainly relates to the data including:(1) Investigation of the current situation of domestic and foreign automobile collision avoidance system and the developme
