Research On Principle And Parameter Design Rule Of Differential Grating Displacement Sensor And Its Experiment

This paper is the basic component part of the project, "Study on Differential Grating Displacement Sensor", which is supported by National Science Foundation of China.Usually, displacement sensor forms grating distributing in space equably when a certain variable periodically changes in the course of movement, and we can gain displacement value by counting the grating number. For instance, the displacement value of optical grating is obtained from the change of Moire Fringe, that of the magnetism grating from the magnetic field change between north magnetic pole and south magnetic pole, that of the gear grating from the magnetic flux change of measuring end aroused by the relative motion between tooth top and tooth root of gear, and that of the capacitive grating from the periodic change of capacitance of condenser aroused by the area change between electrode panels. The common defect of grating sensors lies in the difficulty to further increase the number of grating lines. In order to meet the resolution demand in engineering practice, the original signal must be subdivided with electronics method, which can bring some new problems. Therefore, it still deserves attention for researchers how to increase the number of original grating lines. Are there any other methods to solve the above-mentioned problem when it is difficult to increase the number of mechanical reticle?There has been an idea we can use for reference that makes use of the difference of pole number to realize certain magnification. For example, "the differential frequency measurement system" makes use of the difference of grating line number to realize the magnification of signal phase comparison period, harmonious wave gear does tooth number difference between outer gear and inner gear to realize the magnification of transmission ratio, Vernier Caliper does reticle number difference to enhance its resolution. In this paper, a new method is presented for the first time, which can make use of pole number difference to realize the magnification of grating line number, that it is to say, it can make use of lesser grating number of reticle to realize more equivalent grating line number. Using the method, a new kind of sensor is proposed named as differential grating displacement sensor. The paper discusses the sensor from theoretic reasoning to experimental validation in detail, which mainly includes the following contents:1. Principle of differential grating displacement sensor.2. Parameter design rule and signal-producing mechanism of differential grating displacement sensor.3. Structure design and material selection of differential grating displacement sensor.4. Experiment process and experiment result analysis of differential grating displacement sensor.The above-mentioned researches have verified the correctness of differential grating displacement sensor idea, formed the rudiment of differential grating displacement sensor, and established the solid foundation for the further study on the sensor.