【作者】 宋宇龙；

【导师】 孟庆浩；

【作者基本信息】 天津大学 ， 控制工程， 2012， 硕士

【摘要】 在复杂的障碍物环境中,串扰现象是影响超声测距准确性的主要原因之一。另外,随着测量范围的扩大,势必要求超声发射序列长度的加大,从而导致测距分辨能力的降低。因此,加大测量范围与提高测距精度两者之间是相互矛盾的。针对以上问题,本文的研究思路是构造基于正弦信号的扩频编码序列激励超声换能器工作,同时接收端采用相关处理实现测距。根据这一思路,本文做了如下工作。在基于脉冲形式编码调制的超声测距系统的基础上做了进一步的改进,搭建了基于正弦信号编码调制方式的超声测距硬件系统。该系统性能稳定,功耗适中。为构造基于正弦信号的超声编码扩频序列提供了良好的平台。对搭建完成的正弦编码超声扩频测距系统中各主要环节的幅频特性进行分析和验证,根据实测数据拟合出了信号在系统中传输的幅频特性。以硬件平台作为基础,构造了基于正弦信号激励的超声编码扩频序列。采用m序列、Gold码以及混沌序列等随机特性较好序列结合扩频调制方式作为超声测距系统的激励序列,取得较好相关效果,验证了正弦编码扩频方法在抑制串扰课题上的可行性。并在对激励信号编码扩频的基础上实现了离线相关测距方法,在发射序列较长情况下保持较高测距精度,有效缓解了测量范围与测距精度的矛盾。更多还原

【Abstract】 In a complex environment with obstacles, crosstalk is one of the main reasons that affect the accuracy of an ultrasonic ranging system. Besides, with an increase in the measuring range, the length of ultrasonic emission sequence is normally required to increase, and thus it inevitably leads to the reduction of ultrasonic ranging resolution capacity. Therefore, increasing the measuring range and improving the ranging accuracy are contradicted to each other. To solve this problem, the idea of exciting the ultrasonic transducer with sine coded spread spectrum sequences is proposed in this thesis, and the correlation processing technique at the receiving end is adopted to measure the distance. The main research work of this thesis is summarized as follows.The hardware of an ultrasonic spread spectrum ranging system excited with sine signals is built on the basis of the previous pulse coded ultrasonic ranging system. The established hardware system has stable performance and moderate power, and it provides a good platform for constructing sine coded spread spectrum sequences.The amplitude-frequency characteristic of each major part in the ranging system is analyzed and validated first, and then the amplitude-frequency characteristic of the whole ultrasonic ranging system is fitted using the measured distance data.Sine coded spread spectrum sequences have been constructed. To achieve good correlation results, pseudorandom sequences including m-sequence, Gold code and chaotic sequence combined with spread spectrum modulation are used to excite ultrasonic transducers. The feasibility of the sine coded spread spectrum method for crosstalk inhibition has been verified. Offline correlation method is used to calculate the measured distance. Experiments show that a high ranging accuracy can be obtained when the duration of the ultrasonic exciting sequence is long. It effectively alleviates the contradictions between the measuring range and ranging accuracy.更多还原