空间滤波转速遥测中的旋转中心辨识

进行空间滤波转速遥测时,需要确定目标旋转中心所在的位置后才能判定转速的方向并计算转速的大小。本文根据光学空间滤波测速原理,提出了一种基于双差分空间滤波传感器的旋转中心判定法。用多个光电池构成含有两个差分空间滤波器的双差分空间滤波传感器,该传感器输出中心频率为f1和f2的两路准正弦信号;移动双差分空间滤波传感器,用移动前后的两组中心频率值计算出系数j;根据j的符号和f1与f2的相对大小即可判定旋转中心的位置区域。结果表明,j0代表旋转中心的成像点O′在双差分空间滤波传感器的中间,j0且f1f2表示O′在双差分空间滤波器的下同侧,j0且f1f2表示O′在双差分空间滤波器的上同侧。该方法在转速相对平稳时能简单准确、远距离地辨识固体物旋转中心和气固液多相流涡旋中心的位置区域。

Identification of rotational center in remote angular-velocity measurement with spatial filtering

To determine the direction of a rotational speed and to calculate the value of the rotational speed in remote angular-velocity measurement with the spatial filtering technique, it is necessary to exactly identify the location zone of measured-object rotation center. Therefore, a method of determining the rotation center based on Double Differential Spatial Filtering Sensor (DDSFS) was proposed according to the principle of spatial filtering velocimetry. The DDSFS constructed by multiple photovoltaic cells consists of two Differential Spatial Filters (DSFs), which outputed two quasi-sinusoidal signals with the central frequencies of f₁ and f₂. By moving the DDSFS, a coefficient j could be calculated by using two groups of central frequencies before and after moving the DDSFS. Then, the location zone of the rotational center could be distinguished depending on the sign of the coefficient j and the relative relation between f₁ and f₂. The achieved results show that j<0 represents the location zone of the imaged rotation center O' to be between DSF₁ and DSF₂, and that j>0 with f₁>f₂ indicates the location zone of the imaged rotation center O' to be below the DDSFS, and that j>0 with f₁2 indicates O' to be above the DDSFS. The proposed method can be employed to determine the rotational center of solid body, and the location of whirling center in multiphase fluid with solid, liquid or gaseous substances when the rotation speed is relative stable.