Research On Magnetic Encoder Based On GMR Sensor

Magnetic encoder is a detecting unit based on new type magnetic sensingelement. Compare with the photoelectric encoder, magnetic encoder has manyadvantages such as high rotating speed, high reliability, great anti-shakeperformance, great capacity of resisting disturbance, dust-proof, oil-proof, simplestructure, easy-installation, convenient debugging, easy to miniaturization and lowcost ,etc. Therefore, magnetic encoder has great market potential and will replacethe photoelectric encoder in many fields.The performance of magnetic encoder mainly depends on the performance ofmagnetic sensor, magnetizing technology of magnetic grid and the speed andaccuracy rating of processing circuit. Encoder using high resolution-magnetic gridhas many disadvantages such as complex craft, high developing cost and bigvolume; Encoder using single magnetic pole-magnetic grid must to use high-powerelectronic division, so it will generate great angle-error, low down the encoderaccuracy, meanwhile, the magnetic sensor used in this encoder is easily disturbedand has bad thermo-stability. Considering the above problems, this paper willresearch a new type magnetic encoder using high performance GMR sensor, lowresolution-magnetic grid (64 magnetic poles) and electronic division. It well solvedthe problems such as volume, resolution and errors.Quality and distribution of magnetic field decide the quality of analogwaveform produced by signal produce circuit, which has great influence on theencoder accuracy and signal processing. If the signal processing part can calculatethe locating message accurately and quickly or not when the encoder rotates quicklyalso decide the performance of encoder. Thus this paper have analyzed the encodefocus on the field division on magnetic grid and the realization ofdivision-algorithm.Considering the magnetic distribution, based on the static-constant magneticfield theory, this paper have developed a multiple magnetic pole-magnetic gridmodel under the ideal situation, and also have done the model simulation usingMatlab and get the magnetic distribution theoretically; do further simulation usingAnsoft and get the three-dimension magnetic field distribution radically. This twotheory research will guide the design of signal processing circuit and the detectingcircuit.Considering the realization of division-algorithm,this paper have calculatedabout the encoder locating message based on MCU F28027, and output the signal bythe incremental mode.Finally,this paper research and make out a Micro high-speed incremental ma-gnetic encoder based on the theory analysis and simulation, we found the encoderwell achieved certain performance target by testing the frequency respond, also theencoder has the advantage of small size, high-speed and high reliability.