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1、山东科技大学毕业设计说明书前言摘要：近年来，随着汽车产业的迅速发展和人们生活水平的不断提高，我国的汽车数量正逐年增加。同时汽车驾驶人员中非职业汽车驾驶人员的比例也逐年增加。在公路、街道、停车场、车库等拥挤、狭窄的地方倒车时，驾驶员既要前瞻，又要后顾，稍微不小心就会发生追尾事故。据相关调查统计，15的汽车碰撞事故是因倒车时汽车的后视能力不良造成的。因此。增加汽车的后视能力，研制汽车后部探测障碍物的倒车雷达便成为近些年来的研究热点。安全避免障碍物的前提是快速、准确地测量障碍物与汽车之间的距离。为此，设计了以单片机为核心，利用超声波实现无接触测距的倒车雷达系统。 超声波一般指频率在20 kHz以上的
2、机械波，具有穿透性强，衰减小，反射能力强等特点。工作时，超声波发射器不断发射出一系列连续脉冲，给测量逻辑电路提供一个短脉冲。最后由信号处理装置对接收的信号依据时间差进行处理，自动计算出车与障碍物之间的距离。超声波测距原理简单，成本低，制作方便，但其传输速度受天气影响较大，不能精确测距；另外，超声波能量与距离的平方成正比衰减，因此，距离越远，灵敏度越低，从而使超声波测距方式只适用于较短距离。目前，国内外一般的超声波测距仪，其理想的测量距离为45 m，因此大都用于汽车倒车雷达等近距离测距中本文根据声波在空气中传播反射原理，以超声波换能器为接口部件，介绍了基于AT89C52单片机的超声波测距器。该设
3、计由超声波发射模块、信号接收模块、单片机处理模块、LCD显示以及声光告警显示模块等部分组成，文中详细介绍了测距器的硬件组成、检测原理、方法以及软件结构。超声波发射模块中采用555定时器构成的时基电路，接收电路使用两级运算放大器，再将信号进行比较，设计出能够成功对40kHz超声波检波的硬件电路，并且增益可调，与传统超声波检波电路相比，电路变得精简，调试变得相对容易。测距器使用LCD显示目标物的距离。关键词：超声波、测距、AT89C52、倒车Abstract：In recent years, with the rapid development of automobile industry and
4、 the continuous improvement of peoples living standard, Chinas number of cars is increasing every year. Driving in Central Africa at the same time professional staff of the proportion of car drivers is also increasing year by year. Highways, streets, parking, garage and other crowded places narrow r
5、everse, the driver should not only forward but also looking back, a little rear-end careless accidents can occur. According to related statistics, 15% of motor vehicle collisions when the vehicle is reversing, as the capacity of the latter caused by bad.So after the increase of motor vehicles as the
6、 ability to detect obstacles on the development of the rear of the car reversing radar has become the research hotspot in recent years. Security to avoid obstacles on the premise that the rapid and accurate measurement of obstructions and the distance between motor vehicles. To this end, the design
7、of a single-chip microcomputer as the core, the use of ultrasonic ranging to achieve non-contact reversing radar system. Generally refers to ultrasonic frequencies above 20 kHz mechanical waves, with penetrating, and attenuation of small, reflecting the ability and so on. Work, the ultrasonic transm
8、itter continuously emits a series of consecutive pulses to the measurement of logic circuits to provide a short pulse. Finally, signal processing devices based on the received signal for processing the time difference, automatic calculation of turnout and the distance between obstacles. Ultrasonic R
9、anging simple, low cost, easy production, but the transmission speed by a larger weather can not be precise range; In addition, the ultrasonic energy and the attenuation is directly proportional to the square of the distance, the farther the distance, the lower sensitivity and thus Ultrasonic Rangin
10、g way so that only apply to a shorter distance. At present, ultrasonic range finder at home and abroad in general, the ideal distance of the measurement 4 5 m, thus reversing radar are used in cars, such as close range in this paper, according to the spread of sound waves in air reflection to ultras
11、onic transducer interface components, based on MCU AT89C52 ultrasonic range-finder. Designed by the ultrasonic transmitter module, receiver module, single-chip processing module, a digital display and alarm sound and light display module, such as parts, the text in detail the range of hardware devic
12、es, detection theory, methods and software architecture. The use of ultrasonic transmitter module consisting of 555 time-base timer circuit, receiving circuit using the SONY company dedicated CX20106A infrared detecting chip, the chip used in the detector circuit 38kHz, the text of the chip through
13、the careful analysis of the internal circuit design can successfully 40kHz ultrasonic detection of hardware circuitry and adjustable gain, and compared to conventional ultrasonic detection circuit, the circuit has become streamlined and easier to debug. The use of digital rangefinder display the dis
14、tance between objects. Key words:AT89C52; Silent Wave;Measure Distance; Reversing目录前言1绪论81.1选题背景81.2设计目的81.3 设计的意义91.4目前国内外的研究现状101.5超声波的特性及作用原理111.6 发展历史12第二章 方案论证162.1超声波的定义162.2超声波的物理特性162.2.1超声波的衰减182.3发射脉冲波形212.4超声波测距原理222.5测量与控制方法232.6理论计算232.7 影响精度的因素分析252.8 提高精度的方案及系统设计272.8.1温度校正的方法提高测距精度27
15、2.8.2标杆校正的方法提高测距精度282.9 系统的工作原理29第三章 系统局部硬件电路设计313.1 AT89C52单片机313.1.1时钟电路323.1.2复位电路333.2超声波发射电路333.2.1多谐振荡器333.2.2超声波传感器353.3超声波接收电路373.3.1放大电路及其参数的设计373.3.2电压比较电路及其参数的设计383.4 LCD液晶显示部分结构403.4.1 LCD的参数和性能及引脚介绍403.4.2 AT89C52和LCD显示器模块的接口413.4.2.1AT89C52和LCD显示器模块的硬件接口413.5语音报警模块433.5.1放音芯片的选择443.5.2 API8108A和AT89C52的硬件接口443.6电源模块46第四章 系统软件设计484.1超声波接收发射软件设计484.1.1 超声波测距仪的算法设计484.1.2串扰问题514.3 LCD液晶显示部分软件设计524.3.1读/写时序524.3.1.1OCMJ4X8C型LCD显示模块的读时序534.3.1.2OCMJ4X8C型LCD显示器模块的写时序54第五章 主要参考文献55第六章 致谢辞56绪论1.1选题背景随着科技发展的不断进步，自动测量的技术不断更新，非接触式测量技术也有了长足的发展。在很多工控场合，测量的物体是不能够直接接触到的，或者是测量物体不宜直接接触,
