采用椭圆算法和Canny算子的超声TOF估计方法  

Ultrasonic TOF estimation method using ellipse algorithm and Canny operator edge detection

作　　者：李鹏[1,2] 蔡玉雷 陈金立[1,2] 

机构地区：[1]南京信息工程大学电子与信息工程学院,南京210044 [2]江苏省气象探测与信息处理重点实验室,南京210044

出　　处：《仪器仪表学报》2014年第10期2385-2391,共7页Chinese Journal of Scientific Instrument

基　　金：国家自然科学基金(41075115);江苏省高校自然科学研究计划(10KJB510012);江苏高校优势学科Ⅱ期建设工程资助项目

摘　　要：椭圆算法被用于测量超声回波信号的渡越时间(TOF),以便估计目标的距离。然而,椭圆算法是将估计出的椭圆长轴位置对应的时间点作为TOF值,估计的目标距离值与实际距离值仍有一定误差。为了进一步提高椭圆算法的TOF估计精确度,将Canny边缘检测引入到椭圆算法中,结合回波脉冲包络的特征形成一种新的超声TOF估计方法。首先利用边缘检测算子提取出近似椭圆形的回波脉冲包络的边界,然后根据边界上点对应的信号幅度用差分方法搜索除起始点以外的梯度最大值位置对应的时间确定为TOF值。实验结果表明:改进后的椭圆算法测量绝对误差可以控制在1.5 mm以内,较传统方法相比至少提高0.5 mm。而相对误差达到0.2%,较传统方法提高了30%。改进后的椭圆算法的应用使得测量的准确性和可靠性均得到了明显提升。The ellipse algorithm is employed to measure the time of flight （TOF） in ultrasonic echo signal so as to estimate the range of tar- get. However, there still exists an obvious estimation error, because in the method the estimated time corresponding to the vertical axis of the ellipse is directly treated as the TOF in echo signal. To improve the estimation accuracy of TOF for the ellipse algorithm, we propose a novel ultrasonic TOF measurement method combining the ellipse algorithm and the canny edge detection. First, the edge detection operator is applied to detect the boundary of the elliptic echo pulse envelope. Then, the gradients of ellipse edge variation in the second quadrant of coordinate system are calculated with the difference method, and the TOF can be determined according to the maximum gradient position. The experiment results show that the absolute measurement error can be limited in 1.5 mm with the modified ellipse center algorithm. Com- pared with traditional method, the absolute error reduces at least 0.5 ram; the relative error is 0. 2% , which is approximately 30% reduc- tion. The application of the modified ellipse method makes the measurement accuracy and reliability improved obviously.

关 键 词：超声距离测量 椭圆算法 Canny算子边缘检测 渡越时间估计 

分 类 号：TH816.2[机械工程—仪器科学与技术] TN911.7[机械工程—精密仪器及机械]