The Research Of The High-resolution Magnetic Encoder Based On FPGA

The magnetic encoder is a sensor which converts axis mechanical corner into digital oranalog electrical signal with a method of magnetic and electricity. It can meet to analogphysical measurement such as angle, linear displacement and speed. The resolution is themost importest indicator of the magnetic encoders, so improving the resolution of themagnetic encoder has become the focus of research in recent years.The article researches the sine&cosine magnetic encoder which appears in recent years,using the integrated chip AM4096to achieve the original signal, combine hardware withsoftware, deal with the internal signal and output signal. The internal signal processing: obtaina pair of voltage signal about orthogonal rotor position through the rotation of the polarmagnetic filed, using the A/D converter to sample and convert the analog signal data.Calculate the deflection angle base on CORDIC algorithm pipeline architecture which designfor the arc tangent function module. Simulate the algorithm with Verilog HDL in the FPGAsoftware environment Quartus II9.0, output the signal with sine&cosine wave, realizing thesignal decoding. The output signal processing: the output of sine&cosine signal can besubdivided further, it can be achieved with relatively simple hardware circuit, setting areference voltage, the sine&cosine signal goes through the voltage comparator, the output ofcomparator is one when the input is greater than the reference voltage, on the contrary, theoutput is zero. The comparator will output a count pulse when go through a reference voltage,the comparator will output different counting pluses if choose different reference voltages, itcan achieve the purpose of signal subdivided. The experiment results show that the resolutionof the magnetic encoder is12bit （4096p／r） with the internal signal processing, the outputsignal can reach12multiplier with the output signal processing, the resolution can reach49152p／r, it meet to the requirements of design.