摘 要
随着我国社会经济的不断发展，汽车行业也随之蓬勃发展，公路交通呈现出车流密集化和驾驶员非职业化的趋势，因此交通事故越来越多。本文设计的汽车防撞雷达，就是当汽车与障碍物的距离较近时即可向司机预先发出报警信号，可及时有效的防止交通事故的发生。
该汽车防撞雷达是以MCS-51系列单片机为核心器件，结合比较常规的超声波测距器件和霍尔车速传感器以及价格低廉的电子元件组成，包括硬件设计和软件设计两部分。硬件设计方面，通过超声波对车辆行驶过程中的各种情况进行监测，再用霍尔测速传感器对车速进行检测，同时为了提高测量精度，设置了温度检测电路；软件设计方面，定时/计数器T0通过对发射到接收超声波的时间进行计时，定时/计数器T1是完成一秒钟内脉冲数的计数，然后将所得数据送入控制单元，通过单片机对检测结果进行处理分析并做出相应的判断。当探测到存在潜在碰撞危险时，单片机及时驱动报警系统向驾驶员发出语音提示及报警信号以提醒驾驶员采取控制措施以避免交通事故的发生，从而实现了汽车防撞控制的目的。
本系统具有低误差、高精度和低成本的特点。该系统的应用可以保证运行车辆的安全性，提高公路运输效率，具有广泛的应用前景和经济前景。
关键词：单片机；超声波测距；报警系统；防撞雷达
Abstract
With the development of our social economy,the automobile industry is developing,too.The traffic tends to be traffic-intensive and driver-unprofessional, so traffic accidents increase dramatically.The automobile anti-collision radar is designed for sending alarm signal in advance when it is near to obstacle, it can prevent the occurrence of traffic accidents timely and effectively.
The automobile anti-collision radar takes the MCS-51 chip for centre control unit, integrate with conventional ultrasonic ranging device,hall sensor and cheaper electronic components. It includes hardware design and software design.In the design of hardware,the distance of automobile and obstacle is measured by ultrasonic,and the automobile velocity is measured by hall sensor, at the same time the temperature detection circuit is set in order to improve the measurement accuracy;in the design of software,timer/counter
T0
calculates
ultrasonic
time
from
launch
to
receive,timer/counter T1 counts pulse in a second, after that transmits measure data to control unit, then measure rusults are analyzed through single-chip microcomputer and gives corresponding judge.When potential risk of collision is detected,single-chip microcomputer will drive alarm system that send voice prompts and alarm signals for driver to remind the driver to take control measures in order to avoid the occurrence of traffic accidents. thus realize the purpose of anti-collision for automobile.
The system has characteristic such as low erroneous, high accuracy and low cost.The application of this system may guarantee safety of running automobile.It can raise transport efficiency,and has great application and economic trend.
Key Words：Single-chip microcomputer；Ultrasonic ranging；Alarm system；
Anti-collision radar
目 录
第1章 绪 论 .......................................................................................................... 1
1.1 课题研究的背景 ....................................................................................... 1 1.2 国内外汽车防撞雷达的研究现状 ........................................................... 1
1.2.1 汽车防撞雷达发展阶段 ................................................................ 1 1.2.2 汽车防撞雷达国外发展概况 ........................................................ 2 1.2.3 汽车防撞雷达国内发展概况 ........................................................ 2 1.3 汽车防撞雷达未来发展趋势 ................................................................... 3 1.4 汽车防撞雷达设计的内容及意义 ........................................................... 4 第2章 汽车防撞雷达总体方案论证 .................................................................... 5
2.1 汽车防撞雷达设计的技术指标 ............................................................... 5
2.1.1 汽车防撞雷达设计的必要性 ........................................................ 5 2.1.2 汽车防撞雷达设计的技术指标及要求 ........................................ 5 2.2 系统设计方案的论证 ............................................................................... 5
2.2.1 主控芯片的选择 ............................................................................ 6 2.2.2 测距器件的选择 ............................................................................ 6 2.2.3 测速器件的选择 ............................................................................ 6 2.2.4 系统的可行性 ................................................................................ 7 2.3 系统设计总体原理方框图 ....................................................................... 8 第3章 汽车防撞雷达硬件电路设计 .................................................................... 9
3.1 主控芯片 ................................................................................................... 9
3.1.1 AT89S51的主要技术参数 .............................................................. 9 3.1.2 AT89S51各引脚功能 .................................................................... 10 3.2 超声波信号发射电路 ............................................................................. 11
3.2.1 超声波产生的方案选择 .............................................................. 11 3.2.2 超声波的发射 .............................................................................. 12 3.3 超声波信号接收电路 ............................................................................. 13
3.3.1 超声波放大 .................................................................................. 13 3.3.2 超声波的接收 .............................................................................. 14 3.4 测温电路 ................................................................................................. 15
3.4.1 温度对波速的影响 ...................................................................... 15