对基于最大长度序列原理(maximum length sequence,MLS)的二维绝对位置精密视觉检测系统的各种误差源进行了分析和实验。介绍了MLS理论及其序列生成方法,设计了二维视觉靶标,并搭建了可检测两个正交方向线位移的绝对位置非接触检测实验...对基于最大长度序列原理(maximum length sequence,MLS)的二维绝对位置精密视觉检测系统的各种误差源进行了分析和实验。介绍了MLS理论及其序列生成方法,设计了二维视觉靶标,并搭建了可检测两个正交方向线位移的绝对位置非接触检测实验系统。测得系统稳定性在两个正交方向上线位移均不大于0.3 mm RMS。针对应用环境和系统安装工艺需求,基于独立误差分析原理,全面分析探讨了镜头失焦、照明不均匀、靶标偏转以及镜头倾斜等可能造成检测误差的因素对测量精度的影响,开展了相应实验验证,从而提出了改进方法和具体的实施安装工艺技术要求。理论分析和实验表明,镜头失焦和靶标偏转或镜头倾斜不大于1°对测量精度的影响均小于1 mm RMS;而照明不均将影响MLS序列的识别,在改进算法后,其对测量精度的影响也小于1 mm RMS。最终各种因素可能导致的综合误差不大于1.5 mm RMS。该实验结果表明,误差源理论分析与实验相符,验证了该基于最大长度序列的二维绝对位置检测方法具有良好的环境适应性,且对安装工艺要求低、实施方便,可用于精密位移机构的非接触高精度二维绝对位置检测。展开更多
The use of in-seam waves for void detection in mines requires the capability of capturing high frequency signals over large distances. For instance, the Airy phase of Love waves which are used for void detection in co...The use of in-seam waves for void detection in mines requires the capability of capturing high frequency signals over large distances. For instance, the Airy phase of Love waves which are used for void detection in coal mines ranges from several hundred to over one thousand Hertz and the expected travel distance of these signals is at least 90 m （equivalent to a detection distance of 45 m） for the technique to be considered practical. In order to obtain high quality and broadband signals, sensors are conventionally grouted at the bottom of boreholes so that the attenuation due to the fractured surface is minimized and the coupling effect is improved. However, to be economically feasible, the expensive and high sensitive sensors must be retrievable so that they can be used repeatedly at the same or other locations. Because of these concerns, a retrievable sensor installation technique was developed. This paper provides a detailed review of the technique as well as a brief discussion of its applications. The technique is simple and reliable for both installation and retrieval operations and can be used for boreholes oriented in any directions. The technique has been demonstrated in over 200 sensor installation/retrieval operations under various borebole conditions, including bituminous coal, anthracite coal, shale, sandstone and trona. With this technique, we were able to detect the high frequency signals required for our projects. For instance, the signals used at a trona mine for void detection have a typical frequency of 5 kHz with the travel distance of 150-200 m. The results of these operations have shown that sensors installed in the prescribed manner exhibit predictable, consistent, and repeatable performance. The technique also provides an economical and reliable means for many other field seismic monitoring applications where high quality and broadband signals are essential, such as microseismic monitoring and geotomography studies.展开更多
文摘对基于最大长度序列原理(maximum length sequence,MLS)的二维绝对位置精密视觉检测系统的各种误差源进行了分析和实验。介绍了MLS理论及其序列生成方法,设计了二维视觉靶标,并搭建了可检测两个正交方向线位移的绝对位置非接触检测实验系统。测得系统稳定性在两个正交方向上线位移均不大于0.3 mm RMS。针对应用环境和系统安装工艺需求,基于独立误差分析原理,全面分析探讨了镜头失焦、照明不均匀、靶标偏转以及镜头倾斜等可能造成检测误差的因素对测量精度的影响,开展了相应实验验证,从而提出了改进方法和具体的实施安装工艺技术要求。理论分析和实验表明,镜头失焦和靶标偏转或镜头倾斜不大于1°对测量精度的影响均小于1 mm RMS;而照明不均将影响MLS序列的识别,在改进算法后,其对测量精度的影响也小于1 mm RMS。最终各种因素可能导致的综合误差不大于1.5 mm RMS。该实验结果表明,误差源理论分析与实验相符,验证了该基于最大长度序列的二维绝对位置检测方法具有良好的环境适应性,且对安装工艺要求低、实施方便,可用于精密位移机构的非接触高精度二维绝对位置检测。
基金Supported by the Mine Safety and Health Administration (MSHA) Project in US (B2532532)
文摘The use of in-seam waves for void detection in mines requires the capability of capturing high frequency signals over large distances. For instance, the Airy phase of Love waves which are used for void detection in coal mines ranges from several hundred to over one thousand Hertz and the expected travel distance of these signals is at least 90 m （equivalent to a detection distance of 45 m） for the technique to be considered practical. In order to obtain high quality and broadband signals, sensors are conventionally grouted at the bottom of boreholes so that the attenuation due to the fractured surface is minimized and the coupling effect is improved. However, to be economically feasible, the expensive and high sensitive sensors must be retrievable so that they can be used repeatedly at the same or other locations. Because of these concerns, a retrievable sensor installation technique was developed. This paper provides a detailed review of the technique as well as a brief discussion of its applications. The technique is simple and reliable for both installation and retrieval operations and can be used for boreholes oriented in any directions. The technique has been demonstrated in over 200 sensor installation/retrieval operations under various borebole conditions, including bituminous coal, anthracite coal, shale, sandstone and trona. With this technique, we were able to detect the high frequency signals required for our projects. For instance, the signals used at a trona mine for void detection have a typical frequency of 5 kHz with the travel distance of 150-200 m. The results of these operations have shown that sensors installed in the prescribed manner exhibit predictable, consistent, and repeatable performance. The technique also provides an economical and reliable means for many other field seismic monitoring applications where high quality and broadband signals are essential, such as microseismic monitoring and geotomography studies.
