Research Of Subdivision And Compensation Of Sine-cosine Encoder Signal

With the development of the numerical control technology, as one of the mostimportant feedback components of the numerical control system, the sine-cosine encoder ismore and more important to the high speed and high precision CNC system. At present, thetechnology of extracting high performance position and velocity information fromsinusoidal encoder is mastered in the hand of foreign companies. To break the monopoly,the subdivision and the compensation of sine-cosine encoder signal are researched in depthand a kind of high performance subdivision method is proposed in the thesis.At first, the four-field and the single-field scanning principle are introduced; theinfluencing factors of the offset error, gain error and the phase error of the sine-cosine signalare analyzing; the model is built on the Matlab software, the influence of this error forsubdivision precision is researched and the technological index of the sine-cosine signal isconcluded; comparing the advantage and the disadvantage of the popular compensationmethod, a novel dynamic correcting of offset error, gain error and phase error based onpipeline architecture of FPGA (Field－Programmable Gate Array) is proposed in this thesis.Either subdivision method that multiplying the frequency of input signal by four orshifting the phase by the link of resistances, the precision is limited and cannot meet therequirements. There for, the arc tangent subdivision scheme is implemented based onCORDIC (Coordinate Rotation Digital Computer) algorithm. However, this method issensitive to noise and cannot meet the requirements. For this, a novel subdivision schemebased on tracking-loop is proposed in thesis. This method built a PI controller to suppressthe noise and can meet the requirements.At last, the sine-cosine encoder signal processing hardware platform is designed forverifying the proposed algorithm. In the thesis, the author measured the original signal that output from sinusoidal encoder, analyzed the error, compared the signal that before and aftercompensation, verified the dynamic compensation scheme that based on the FPGA pipelinearchitecture, compared the data precision that get from CORDIC algorithm andtracking-loop algorithm, verified the advantage of tracking-loop. The experimental resultsindicate that the proposed subdivision and compensation method can reach to1024multiplyfrequency and meet the requirements of the high performance motion control.