论文题目：超声波测距仪的设计(软件) 专 业：自动化
本 科 生： （签名）________ 指导教师： （签名）________
摘 要
超声波测距作为一种非接触性的光学测量方法，近年来得到了广泛应用。它具有测量方便,不对被测物体产生损坏等优点。超声波明显特征是方向性好，穿透性强。尤其是在光不透过的固体中，它碰到杂质或分界面就有显著的反射。因此，可以利用超声波实现对距离的测量。距离是通过测量发射的超声波与接受到被测物体反射的回波之间的时差来确定的。采用压电式超声波换能器。装置包括单片机系统、显示电路、超声波发射电路和超声波检测接收电路四部分。系统的软件部分则包括主程序、定时子程序、显示子程序和外部中断服务子程序。为了有利于程序结构化和容易计算出距离，主程序采用C语言编写。完成了超声波测距仪的软硬件设计，实现了测量结果的显示，经系统调试可看出，LED数码管显示清晰稳定，测量结果稳定可靠，测距仪最大误差不超过5cm。 关键词：超声波测距仪,单片机
Thesis: ultrasonic range finder (software) Specialty: Automation
Undergraduate: (Signed) __________ Instructor: (Signed) __________
ABSTRACT
Ultrasonic Ranging is a non-contact optical measurement method which has been widely
applied in recent years. It has the advantages of measuring convenience, not be the object produce damage. Obvious features of the ultrasound is directional, penetrating. Especially in light opaque solid, it met the impurities or the interface will have a significant reflection.. Therefore, we can use ultrasound to achieve the measurement of distance. The distance is got by measuring time difference that between emission ultrasonic and the echo of the measured object reflection received with piezoelectric ultrasonic transducer. The device includes a microcontroller system, display circuit, ultrasonic transmitter and ultrasonic detection receiver circuit. The software part of the system include the main program, timing subroutine display routines, and external interrupt service routine. The main program use C language for conducive to the program structure and easy to calculate the distance. I complete hardware and software design of the ultrasonic range finder, and achieve measured results display. According to system debugging, LED digital display clear and measuring results are stable and reliable and the range finder error is less than 5cm.
KEY WORDS: ultrasonic range finder SCM
前 言
随着科技的迅猛发展越来越多科技成果被广泛的运用到人们的日常生活当中，给我们的生活带来了诸多方便。这一设计就是本着这个宗旨出发，利用超声波的特性来为我们服务。
人们能听到声音是由于物体振动产生的，它的频率在20Hz-20kHz范围内，超过20kHZ称为超声波。由于超声波频率较高，沿直线传播，绕射小，穿透力强，指向性强，传输过程中衰减少，能量消耗缓慢，在介质中传播的距离较远，遇到杂质或分界面时会产生反射波，因而超声波经常用于距离的测量。超声波有两个特点，一个是能量大，一个是沿直线传播，它的应用就是按照这两个特点展开的。利用超声波检测往往比较迅速、方便、计算简单、易于做到实时控制,并且在测量精度方面能达到工业实用的要求,因此在移动机器人,汽车安全,海洋测量等上得到了广泛的应用。本设计采用超声波传感器工作于发射和接收,利用声波在空气中的传播速度和发射脉冲到接收反射脉冲的时间间隔计算出障碍物到超声波测距器之间的距离，并实时显示出来。
论文概述了超声波检测的发展及基本原理，对于系统的程序设计进行了讨论，并且在介绍超声波测距系统功能的基础上，提出了软件系统的总体构成及其子程序设计。
目 录
1 绪 论 .................................................................................................................................... 1 1.1课题设计的研究现状 ........................................................................................................ 1 1.2课题设计的任务和要求 .................................................................................................... 2 1.2.1课题设计的任务 .......................................................................................................... 2 1.2.2课题设计的要求 .......................................................................................................... 2 1.3选题的意义 ........................................................................................................................ 3 1.4 研究内容及论文构成 ........................................................................................................ 3 2 超声波测距原理 .................................................................................................................... 5 2.1超声波简介 ........................................................................................................................ 5 2.1.1超声波的声学特性 ...................................................................................................... 5 2.1.2超声波的发生原理 ...................................................................................................... 6 2.2超声波传感器的原理与特性 ............................................................................................ 7 2.2.1原理 .............................................................................................................................. 7 2.2.2特性 .............................................................................................................................. 9 2.3 超声波测距仪的测距原理 ................................................................................................ 9 2.3.1单片机最小系统 ........................................................................................................ 11 2.3.2超声波发射电路 ........................................................................................................ 12 2.3.3超声波接收电路 ........................................................................................................ 13 2.3.4超声波测距仪显示电路 ............................................................................................ 15 2.4本章小结 .......................................................................................................................... 15 3 超声波测距系统软件设计 .................................................................................................... 17 3.1 超声波设计概述 .............................................................................................................. 17 3.2主程序流程图 .................................................................................................................. 18
3.3 定时/计数器T0/T1定时程序流程图 ............................................................................. 20 3.3.1方式控制寄存器--TMOD ......................................................................................... 20 3.3.2控制寄存器--TCON .................................................................................................. 21 3.3.3定时器T0流程图 ..................................................................................................... 21 3.3.4定时器T1中断服务程序流程图 ............................................................................. 22 3.4外部中断服务程序流程图 .............................................................................................. 23 3.5显示程序流程图 .............................................................................................................. 23 3.6计算程序流程图 .............................................................................................................. 24 4 电路调试及误差分析 .......................................................................................................... 26 4.1系统软件的调试 .............................................................................................................. 26 4.2系统的软硬件串联调试 .................................................................................................. 28 4.3系统的误差分析 .............................................................................................................. 30 4.3.1声速引起的误差 ........................................................................................................ 31 4.3.2单片机时间分辨率的影响 ........................................................................................ 31 4.3.3随机误差 .................................................................................................................... 32 4.4提高测距精度的方法 ...................................................................................................... 32 4.5本章小结 .......................................................................................................................... 33 结 论 ........................................................................................................................................ 34 致 谢 ........................................................................................................................................ 35 参考文献: .................................................................................................................................. 36 附录： ........................................................................................................................................ 37