Research On High-precision Multi-poles Magnetic Encoder

As technology advances, more and more angular displacement sensors be used. Lithography is rapid developing and the prices is lower, which accelerated optical encoder applications in industrial control systems. Optical encoder received a faver because of its high resolution and accuracy, compared to optical encoder, magnetic encoder have low resolution and accuracy, in many occasions, it can not meet the requirements of current high-precision control system, but the magnetic encoder works with its non-contact, oil-resistant, less susceptible to condensation of environmental impact and good vibration resistance, it still be widely used in the harsh environment. To enhance the resolution and accuracy of magnetic encoder, the subject abandoned the signal processing method of traditional magnetic encoder, and designed a four-pairs magnetic encoder which have high-precision.The subject analyze angle error of a new type of single-pair magnetic encoder caused by installation variation, and put forward principle of calibration to design encoder which can used to avoid angle error caused by manufacture and installation variation. Specific to magnetic encoder based on subdividing the signal, the subject analyze the nonlinear signal which set a limit to improve the resolution, and propose method that processing multi-phase signal in subregion occurred by halls,which can reduce the demand for microprocessor used to processing signal, and it can overcome the limitations caused by nonlinear signal to improve the resolution. In order to solve the problem caused by noise signal to the accuracy of the encoder, the subject propose method of two-magnet-steel structure to design multi-pair magnetic encoder.In order to determine the design method of coding-magnet-steel, the subject analyze the pole distribution sequence of the coding-magnet-steel, and in-depth study pseudorandom sequence which used frequently in coding theory, Specific to the number of coding cycles are 2ⁿ -1,2ⁿ, and between 2^n-1 and 2ⁿ -1, the subject propose method that respectively using m sequence, M sequence, and interceptive sequence of m sequence, and detailedly describe how to creat these sequence. The subject also design coding-magnet-steel of four-pairs magentic encorder.The subject design four-pairs magentic encorder prototype, put forward three types of signal generation, do simulation of three program with finite element software ANSYS, compare the signal quality when there are interference or accumulation of magnetic dust, and determine the optimal solution in the end. The subject design signal processing circuit of the encoder with the core of 32-bit microprocessorμPD70F3452, use the digital low-pass filter to remove noise by software, and design calculation program of absolute angular displacement. The subject produce four-pairs magentic encorder prototype, design program to produce angle data table using the least square method, calibrate the encoder. 15-bit optical encoder made by Changchun Yuheng is used for resolution and accuracy test, it can detect the absolute angle an its resolution can achieve to±1.3′and precision can achieve to±3′. In order to be industrialized, the subject study the cause of error which pave the way for correcting the angle by software.