文档介绍：随着社会经济的发展和交通运输业的不断兴旺，汽车的数量在不断的增加。交通 拥挤状况也日益严重，撞车事件也经常发生，造成了很多不可避免的人声伤亡和经济 损失，面对这种情况，设计一种响应快、可靠性高并且比较经济的汽车防撞预警系统 显得非常的重要。超声波测距法是一种最常见的距离测量方法。本文介绍的就是利用 超声波测距法设计一种倒车防撞报警系统。
首先，论文在分析超声波的物理特性、超声波传感器的特性、超声波测距原理等 基础上，结合本课题，给出了几种测量方案的比较，对影响本系统测量精度的因素和 干扰进行了详尽的分析，制定了相应的解决措施;其次，在硬件选择方面，选择性价 比高的AT89C52单片机、LM324放大器、采用低压差线性电压稳压器、较高内阻的压 力传感器;在软件方面，采用了功能模块化，为以后的升级或者扩展做准备。同时采 用间歇式的工作模式，非采样期间只有显示器、稳压器等处于活动状态;在保证性能 要求的情况下有效的提高了器件寿命。为了降低整个系统的成本，在满足性能要求的 前提下，选择低成本元器件，简化系统设计;采用多点校准技术和线性插值方法，降 低了对传感器的线性的要求，扩大了可选传感器的范围，提高了产品的通用性和可扩 展性，提高了产品的竞争力，从发射探头到接收探头的那一段“敏感时间”，采用了 “延时接收”的方法，进行了测试试验。研究表明，系统运行稳定， — 5. 50m 的测量范围内误差小于lcm,实现了预期要求。
关键词：倒车防撞；超声波测距；超声波；AT89C52
ABSTRACT
With the social and economic development and transportation continues to boom, the automobile quantity climbs in the first mate. Traffic congestion condition also day by day serous, the collision event occurred repeatedly, has caused the inevitable person casualties and the economic loss, in view of this kind of situation, designed one kind to respond quickly, the reliability was high also a more economical automobile guards against hits the early warning system imperative, the ultrasonic wave range finding was the most common one distance range finder method, this article introduces is guards against using the ultrasonic wave range finding design one kind of reversing collision avoidance system.
First,a particular introduction of the physical characteristic of the ultrasonic and characteristics of ultrasonic sensors in this paper. Combining with the characteristics of the subject, several schemes of measurement are put forward and fully analyzed in term of error, advantage and disadvantage .The factors and interferences which will make an effect in measurement accuracy are analyzed at large and the solution is put forward. Second, In the hardware aspect, the AT89C52 MCU with low capability/price ratio, LM324 amplifier, LED monitor, and pressure sensor with higher resistance are used to build the system, and a low