Research On Grating Displacement Sensing System Based On Digital Subdivision Technology

With the development of the advanced manufacturing industry,ultra-precision positioning technology has become one of the key technologies in the frontier science field.Nano-scale measurement accuracy has become the basic requirement of ultra-precision measurement.Nowadays,mature measurement technologies such as He-Ne laser interferometry can not be widely used because of its high cost and harsh environment.With the continuous maturity of grating measurement technology,the new related technologies is constantly emerging.Grating displacement sensor based on digital subdivision technology has gained more and more attention and application in the field of ultra-precision measurement because of its high resolution,large measurement range and reliable measurement.In this paper,the theory of grating displacement sensor system based on Moire fringe theory is analyzed in detail.Using the theory of diffraction optics,we prove that the intensity of Moire fringes is sinusoidal in ideal state.Then the intensity signal of Moire fringes is pretreated and simplified to two orthogonal sinusoidal signals with equal amplitude.Finally,according to the requirement of the signals,we have designed and manufactured a signal conditioning circuit.According to the related principle of Moire fringe subdivision,this paper specifically analyses the algorithm constitution and interval subdivision of Moire fringe tangent subdivision.After that,the interference factors affecting the quality of Moire fringe signal and their influence on subdivision accuracy are emphatically studied,the maximum deviation of subdivision under the influence of complex interference factors is also obtained.Finally,we complete the displacement correlation algorithm and motion direction identification by software method.In order to verify the accuracy of grating sensing system in the whole range,we built a driving platform by using macro-micro two-stage driving method;the macro-stage is driven by stepper motor and ball screw,the micro-stage is driven by piezoelectric ceramic and flexible hinge to compensate the positioning error of macro-stage.The output high-precision displacement is measured by grating sensor system,and then the displacement value is obtained by hardware circuit and computer processing.The experimental results show when the system moves forward and backward,the measurement performance is basically the same.And the system possess good repeatability and good linearity.