摘要
自20世纪60年代以来,汽车技术已经步入了电子技术时代。品种繁多的传感器、电子控制单元、微处理器、存储器、I/O接口、执行机构、显示器和设计软件等已广泛应用于汽车设计制造领域,实现了极为复杂的多元控制功能,从而极大地推进了汽车技术性能的提升。在汽车使用安全方面,应用最为广泛的是汽车防抱死制动系统(ABS)。它是汽车上的一种主动安全装置,用于汽车制动时防止车轮抱死拖滑,以及提高汽车制动过程中的方向稳定性、转向控制能力和缩短制动距离,充分发挥汽车的制动效能。以电子防抱死制动控制技术为代表的一大批新兴技术的应用,使汽车无论在使用和驾驶的安全性上,还是在日常的技术维护上,都得到了很大的改进。随着人们物质生活水平的不断提高,追求更加安全、更加舒适的驾乘已经成为一种趋势。因此,进一步发展汽车电子技术,尤其是应用一些新兴的传感器技术,以达到汽车性能的最优化,最大程度地发挥汽车驾、乘、载的功能。在整个道路交通事故中，汽车追尾事故约占70%以上，有些大的群死群伤恶性交通事故，开始都是由于追尾剐蹭引起的。所以，人们越来越认识到防止追尾事故的重要性。道路交通事故是现代社会的一大公害，与之相关的先进安全技术研究日益受到重视。基于智能交通系统的汽车防撞系统是先进安全技术的一项重要内容，国内外相继开展了相关的研究。本文探讨和研究了一种智能化的汽车防撞系统，在正常行驶时，该系统不报警，当自车与前车之间的距离小于所设定的安全距离并有可能发生碰撞时，该系统将发出报警信息并自动采取措施，以避免碰撞事故的发生。本文参考了相关参考数据，按照汽车在制动过程中的运动状态建立了比较实用、简单的安全距离模型。文中探讨了超声波测距测速的电路设计和软件设计。高速公路汽车防撞系统的研究符合国内外汽车智能化的发展趋势，该系统的应用可以保证高速运行车辆的安全性，提高公路运输效率，具有广泛的应用前景和经济前景。
关键字：汽车技术 ；汽车防撞系统 ；声光报警 ；超声波测距 ；智能化
Abstract
Since the1960s,car technology has entered into electronic technology age. A wide variety of sensors, the electronic control unit, micro processor, memory and I/O interface, actuators, display and design software have been widely used in car design manufacturing field. It Realized the extremely complex multivariate control function, thus greatly promoted the performance of the car technology promotion. In the security of car using, at present, the most widely used system is Anti-lock Braking System (ABS). It is a active safety device of a car, used in automobile braking prevent wheel lock drag slippery, and it improves the car braking process of the direction stability, steering control ability and shortens the braking distance, gives full play to the automobile braking performance.Because of the application of ABS, a representative of a large number of new technology,it greatly improves not only the safety of using and driving a car but also the daily maintenance. As the improve of people’s material living level, the pursuit of more secure, more comfortable ride has become a trend. Therefore, further development of automobile electronic technology, especially the application of some new sensor technology, in order to achieve the performance of optimization, maximize a car’s functions,.In the whole traffic accidents, rear-end accidents are above70%, some big death and injury of a group people in traffic accidents, is due to pileup at the beginning. So, people has given more and more attention to the importance of preventing the pileup.Traffic accidents is a big problem in recent society,therefore, research and development of a kind of high performance car tracing cauda bull warning system become urgent.This paper explores and studies of an intelligent vehicle collision avoidance systems, in normal driving, the system does not alarm when the distance from the vehicle in front is less than the safe distance between the set and the collision may occur when the The system will automatically send alarm information and take measures to avoid a collision. This reference to the relevant reference data, in accordance with the vehicle motion during braking to establish a more practical, simple safety distance model. The article discusses the velocity of ultrasonic distance measurement circuit design and software design. Freeway car collision avoidance system in line with the development trend of domestic and foreign automobile intelligent, application of the system can guarantee the security of high-speed operation of the vehicle,
improving the efficiency of road transport, has broad application prospects and economic outlook.
Key Words: Automobile Technology; Automobile Collision Avoidance Systems; Sound and Light alarms; Ultrasonic Ranging; Intelligence
目录
第一章 绪论 ...................................................................................................................... 1
1.1设计目的和意义 .................................................................................................. 1 1.2设计内容 .............................................................................................................. 1 第二章 系统设计 .............................................................................................................. 2
2.1行车安全距离的概念 .......................................................................................... 2 2.2系统设计的总思想 .............................................................................................. 2 2.3 设计方框图 ......................................................................................................... 4 第三章 STC89C52单片机硬件电路设计 ....................................................................... 6
3.1 单片机最小系统 ................................................................................................. 6
3.1.1 最小系统原理图 ...................................................................................... 6 3.1.2晶振电路 ................................................................................................... 7 3.1.3 复位电路 .................................................................................................. 8 3.2 超声波测速测距电路设计 ................................................................................. 9
3.2.1 几种测距的介绍 ...................................................................................... 9 3.2.2 超声波发射电路 .................................................................................... 11 3.2.3超声波接收 ............................................................................................. 13 3.3 声光报警电路设计 ........................................................................................... 15
3.3.1 报警电路 ................................................................................................ 15 3.3.2 光提示电路 ............................................................................................ 16 3.4 1602LCD显示电路设计 ................................................................................... 16
3.4.1 字符型液晶显示器的显示原理 ............................................................ 16 3.4.2 液晶1602LCD简介 .............................................................................. 16 3.4.3 1602LCD工作原理 ................................................................................ 18 3.5 DAC0808控制电路设计 .................................................................................. 19
3.5.1控制电路的工作原理 ............................................................................. 19 3.5.2 芯片DAC0808工作原理 ..................................................................... 20 3.6 稳压电源电路设计 ........................................................................................... 22
3.6.1 稳压电源的技术指标 ............................................................................ 22
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3.6.2 器件的选择 ............................................................................................ 24 3.6.3 稳压电源工作原理 ................................................................................ 26 3.7 STC89C52的简介 ............................................................................................. 27
3.7.1 STC89C52单片机的特点 ...................................................................... 27 3.7.2 STC89C52 单片机的结构 ..................................................................... 27 3.7.3 STC89C52的管脚功能说明 .................................................................. 29
第四章 STC89C52单片机的软件部分 ......................................................................... 32
4.1 总体流程图 ....................................................................................................... 32 4.2超声波控制及计算车距部分 ............................................................................ 33 4.3 控制车速度部分 ............................................................................................... 33 第五章 结论 .................................................................................................................... 35
5.1 总结 ................................................................................................................... 35 5.2建议 .................................................................................................................... 35 致谢 .......................................................................................................................... 36 参考文献 .......................................................................................................................... 37 附录 .................................................................................................................................. 38
1．程序清单 ............................................................................................................ 38 2．总体电路 ............................................................................................................ 46
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