基于AT89C51单片机的超声波倒车雷达系统的设计

电气自动化论文编号:ZD679    论文字数:19658,页数:43

 目  录
摘  要 I
ABSTRACT II
1 绪论 1
1.1 设计的现状 1
1.2 设计的意义 2
1.3 目前国内倒车雷达的发展现状 2
2 总体设计方案 3
2.1 超声波测距 4
2.1.1 超声波测距原理 4
2.1.2、测量与控制方法 5
2.1.3、理论计算 5
2.1.4 影响精度的因素分析 6
2.1.5 提高精度的方案及系统设计 7
2.1.6 测量盲区 8
2.2 超声波传感器 9
2.2.1超声波传感器原理及结构 9
2.2.2超声波传感器的特性 11
2.2.3 超声波传感器的应用 13
3 硬件设计 14
3.1 超声波发射电路 14
3.2 超声波检测接收电路 15
3.2.1 集成电路CX20106A 15
3.2.2 超声波接收电路 17
3.3 超声波显示及控制部分电路 18
3.3.1 AT89C51单片机的原理及工作特点 18
3.3.2单片机实现测距原理 19
3.3.3 压电陶瓷超声波传感器 (TCF40-18TR1) 19
3.3.4 稳压电源电路 20
3.3.5 显示电路原理 21
3.3.6 温度测量电路 23
3.3.7 键盘控制电路 23
4软件设计 23
4.1 软件设计的要求 25
4.2 超声波测距的算法设计 25
4.3 主程序 26
4.4超声波发送及接收中断程序 28
4.5 显示子程序和蜂鸣报警子程序 30
5 系统的软硬件调试 30
结束语 31
致  谢 32
参考文献 33
附录1 超声波倒车雷达系统的设计 34
附录2 程序清单 35

摘  要
 
 近年来，我国的汽车数量正逐年增加。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。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。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。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。目前，国内外一般的超声波测距仪，其理想的测量距离为1m～5 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AT89C51单片机的超声波测距器。该设计由超声波发射模块、信号接收模块、单片机处理模块、数码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。超声波接收电路使用SONY公司的CX20106A红外检测专用芯片，该芯片常用于38kHz的检波电路，文中通过对芯片内部电路的仔细分析，设计出能够成功对40kHz超声波检波的硬件电路，距器使用数码管显示目标物的距离。
关键词：超声波  测距  AT89C51  倒车

ABSTRACT

 In recent years, China's number of cars is increasing every year. Highways, streets, parking, garage and other crowded places narrow reverse, the driver should not only forward but also looking back, a little rear-end careless accidents can occur.So after the increase of motor vehicles as the ability to detect obstacles on the development of the rear of the car reversing radar has become the research hotspot in recent years. the ultrasonic transmitter 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 Ranging 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 Ranging 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 1~ 5 m, based on AT89C51 ultrasonic range-finder. 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 the careful analysis of the internal circuit design can successfully 40kHz ultrasonic detection of hardware circuitry and adjustable gain, The use of digital rangefinder display the distance between objects.

KEY WORDS AT89C51  Silent  Wave;Measure  Distance Reversing