【正文】 對于設計超聲波測量系統(tǒng)來說具有一定的參考價值。作者還分析了造成料位測量誤差的幾點原因，并給出了幾種方法來減少測量誤差。 浙江師范大學的李鳴華、余水寶利用單片機開發(fā)了一種超聲波料位測量系統(tǒng)。文中分析了聲波的傳輸特性和影響聲速的因素，給出了超聲波測距的框圖。實驗結果表明，該系統(tǒng)在 15m 的測距精度可達到 lcm。該系統(tǒng)的測距原理是利用超聲波傳感器發(fā)射和接收調幅連續(xù)超聲波，基于接收信號于發(fā)射信號之間的相位差和兩傳感器之間的正比關系，用相位差法測量傳感器之間的動態(tài)距離。目前，在超聲無損檢測中，脈沖回波系 統(tǒng)仍是使用最為廣泛的一種。在各種系統(tǒng)中，這是最成功的一種，因為它有最廣泛的通用性，其檢測結果也最容易解釋。德國 人 Begemann 在他的論著《 ULTRASONIC》中 ，詳細的論述了有關超聲波的大量早期資料，該論著一直被認為是該領域的經典之作。相隔 2 年， 1931 年Mulhauser 獲準一項關于超聲檢測方法的德國專利，不過他并未做更多的工作。他提出的這種方法可以用來檢測水中是否存在潛艇并進行水下通信。在第一次世界大戰(zhàn)中，對超聲波的研究逐 漸受到重視。 關鍵詞 ： 超聲波 測距 AT89C51 倒車 雷達 II Design and Research of Parking Sensors Based on Ultrasonic Ranging Technology Abstract The ultrasonic wave automobile backdraft detector is one kind auxiliary unit that can display the condition of the obstacle behind the vehicle in real time .It applies extremely widely in the real life. In this paper, according to the transmission reflection theory of wave in the air, Using supersonic transducer as interface unit and applying monolithic machine techniques to design a series of bus ultrasonic ranging system. The paper is based on the ultrasonic distance reversing collision avoidance system design, mainly using ultrasound features and advantages, ultrasound ranging system and the integration with the integration AT89C51 monolithic integrated circuit, AT89C51 monolithic integrated circuit based on the design of a reverse collision avoidance warning systems. The system used software and hardware integrated approach of modular and multiuse characteristics. The paper outlines the development and the basic principles of ultrasound tests on the principles and characteristics of ultrasound sensors. Some of the main parameters for the system were discussed, and introducing ultrasonic ranging system functions basic, the overall position of the system. Through multiple launch reception circuit design parison, the best designed program drawn, and various system design modules principles introduced. On the position of the system circuit chip introduced and elaborated the principles of their work. Papers introduced system software architecture, through programming to achieve system function. Keywords： Ultrasonic， Ranging， AT89C51， Parking sensors III 目錄 第一章 緒 論 ................................................................................................................................. 5 課題的背景和意義 ................................................................................................................... 5 超聲波測距儀的國內外現(xiàn)狀 ..................................................................................................... 6 本課題的研究內容和目標 ........................................................................................................ 8 第二章 課題設計原理與思路 ....................................................................................................... 10 超聲波測距原理 ..................................................................................................................... 10 影響精度的因素分析 .............................................................................................................. 11 發(fā)射接收時間對測量精度的影響分析 .............................................................................. 11 當地聲速對測量精度的影響分析 ..................................................................................... 12 測量盲區(qū) ................................................................................................................................ 13 系統(tǒng)整體設計方案和論證 ...................................................................................................... 13 系統(tǒng)整 體方案的設計 ....................................................................................................... 13 系統(tǒng)整體方案的論證 ....................................................................................................... 14 第三章 系統(tǒng)硬件設計 .................................................................................................................... 15 51 系列單片機的功能 ............................................................................................................. 15 超聲波發(fā)射電路 ..................................................................................................................... 15 超聲波傳感器原理及結構 ................................................................................................ 16 超聲波傳感器的特性 ....................................................................................................... 17 超聲波檢測接收電路 .............................................................................................................. 20 集成電路 CX20206A ........................................................................................................ 21 超聲波接收電路設計 ....................................................................................................... 22 穩(wěn)壓電源電路 ......................................................................................................................... 23 預警電路 ................................................................................................................................ 24 鍵盤控制電路 ......................................................................................................................... 25 超聲波測距顯示電路 .............................................................................................................. 25 第四章 系統(tǒng)軟件的設計 ............................................................................................................... 27 超聲波測距的算法設計 .......................................................................................................... 27 IV 主程序設計及其流程圖 .......................................................................................................... 29 超聲波發(fā)送及接收中斷程序 ................................................................................................... 31