Research On Raster Signal Subdivision Based On

Angle or position sensors based on the grating signal technology are widely used in the field of precision measurement. Limited by the current manufacturing process and other factors, high precision measurement is difficult to implement if the grating signal is not be processed and directly used to measure. According to characteristics of the grating signal, therefore, researches on the corresponding subdivision technology, such as four subdivisions and direction distinguishing, subdivision with a phase shift resistor chain, phase-lock frequency multiplier subdivision, carrier modulation subdivision, amplitude sampling subdivision and so on, become a hot topic. In this thesis, the method of magnitude sampling subdivision is used to implement the high magnification subdivision.First, a digital oscilloscope is used to collect several groups of the output signals of the grating reading head in operation. Then, MATLAB is used to analyze two channels of the original output signals so as to obtain their characteristics after the signals are filtered and their DC components are removed. According to the signal waveforms after processing, a subdivision algorithm is constructed. And the feasibility of the algorithm to achieve 1024 subdivisions and the feasibility of algorithm of implementation with hardware are verified. In addition, through math deduction, error analysis for factors such as the signal DC level, magnitude range, non-orthogonal phase is done, and some drawings which show influences of these factors on the construction function are obtained with MATLAB software. Thus, a specific scheme of high magnification subdivision for grating signal based on FPGA is proposed.Next, an FPGA-based hardware circuit for the grating signal subdivision is designed, and a detailed analysis for analog and digital logic modules of this hardware circuit is presented. The subdivision circuit employs a parallel processing structure in which the coarse and the fine division circuits work together to improve response rate and subdivision precision. The coarse division circuit is used to divide the signal into 8 segments in each sine period, and the fine division circuit is used to make each segment to be 128 subdivisions, resulting 1024 subdivisions for a grating signal. Several circuit boards are developed, some tests are done. The experimental results show that the FPGA-based subdivision circuit presented in this thesis can really implement 1024 high magnification subdivisions for measured grating signals.