Research On Method Of Identifying Rotational Direction In Non-contact Rotation Parameter Measurement With Self-scale-division

Spatial filter velocimetry method has been used in the linear velocity measurements of aircraft or automobile, since it’s simple, stable, non-contact, strong environmental adaptability and easy to be used. However, it is rarely used to identify the rotational direction by spatial filter velocimetry method and the non-contact or distance measurement of rotational parameters is specially needed in the fan or shaft in other types of large rotating machinery monitoring or rotational speed measuring. In this paper a mathematical model of measuring the linear velocity based on the principles of spatial filter velocimetry has been set up, the relationships between linear speed of movement and center frequencies of output signals were analyzed through random distribution of the campaign images’ spatial frequency spectrum and spatial filtering algorithms. In addition, the equations of linear speed measuring were obtained based on the relationships between speed and velocity, the relationships between velocity and the array components of photoelectric detector. Furthermore, the relationships between equations of linear speed measuring and location area of rotation center were also analyzed.In rotational speed measurement, especially in precisional measurement of mechanical shaft, the identification of rotational direction is the same necessary and important with the identification of rotational speed values. It also needs to identify rotational direction in remote angular-velocity measurement using double differential spatial filter(DDSF), but there exit problems such as the signals are randomness, signals frequency have no rotation direction information.Therefore, this paper has presented an approach to identifying the rotational center and sense of rotation body in the remote angular-velocity measurement with DDSF based on spatial filtering velocimetry and differential subtraction correlation. A coefficient k is calculated by using the central frequencies and their changes of two output signals from the DDSF, and is then combined with the relative position of the differential spatial filter(DSF) with larger central frequency, to locate the position zones of the rotational center. A measurement method for rotational direction is obtained by subtracting and differentiating the output signals of two adjacent photovoltaic cells in one DSF, and then integrating the differential subtraction signal. The sign of the temporal delay at the minimum value of the DSC indicates the displacement direction of the rotational image on the photovoltaic cells.In order to verify the validity of the proposed method, the simulations and experiments are achieved in accordance with a planar circle rotating objects and have confirmed that the proposed methods can be employed to exactly identify the rotational center and sense in the DDSF-based remote measurement of angular velocity. A rotation sensing device using indexing non-contact rotating weight sensor is designed and it does not need to install any benchmarks for measuring the target, It is non-contact contactless and remote sensing. What’s more, the working process of this device is not influenced by speed fluctuations, image magnification changing and random phase fluctuations. Additionally its implementation is easy and convenient, is less sensitive to random phase, which have effectively solved the matter` problems existing in the remote angular-velocity measurement based on DDSF.