Research Of An Absolute Magnetic Encoder Protype Based On Hall Effect

Magnetic encoder is a position sensor which measures the changes of position through magneto-sensitive component’s induction of magnetic field changes. Since the early 1980 s, magnetic encoder has gradually become the focus of the research field of encoder by right of its high precision, small volume, high environmental adaptability, high anti-interference ability and other advantages. With the continuous development of magneto-sensitive component technology, its cost is becoming lower and lower, and the performance of magnetic encoder also keeps improving. Therefore, in the long run, magnetic encoder has great market potentiality. We may also foresee that, in the near future, the magnetic encoder will replace the photoelectric encoder in many fields.Magnetic encoder’s property mainly depends on the properties of magneto-sensitive component and magnets, the arrangement of magnetic grid track, the ability of handling ciecuit, etc. As the high resolution magnetic grid with traditional arrangement form may enlarge the entire volume of magnetic encoder and restrict the application range, the low resolution magnetic grid needs to do the subdividing processing of the original signals collected. That increases the cumulative error and aggrandizes the processing load of the follow-up circuit at the same time, which causes the ruduction of accuracy. Therefore, to achieve integration and high accuracy, an absolute magnetic encode r prototype based on hall effect is studied in this paper. Its original accuracy is up to 5.448′ with 18 bit resolution. Its magnetic grid adopts the unique double track design. Such track arrangement form not only avoids the cumulative error ’s effect on encoder’s accuracy, but also solves the conflicts between high resolution and small vol ume. Besides, cosidering the requirements of encoder’s accuracy in the future application, this paper explores an error compensation method to increase the encoder output accuracy. The encoder accuracy improves a lot after the error compensation and provides a theoretical base for the future encoder applied extension.To the encoder, magnetic grid is the base of producing signals. The arrangement form of magnet pole track on magnetic grid directly decides the whole structure and performance of the encoder. This p aper firstly determins the arrangement form of magnetic grid and the signal collecting method of magneto-sensitive component according to the vernier decoding theory. And it designs a decoding circuit which takes the intergrated hall chip as centre to deco de the position information. Secondly, the quality of the magnetic field on magnetic grid directly decides the output functions of magnetic encoder signal part. Based on the classical magnetostatics theory, this paper constructs a model of multi-poles magnetic grid’s distribution of magnetic field. It calculates and deduces the magnetic field distribution rule of double track magnetic grid through theories, and use software—Matlab, Ansoft and Ansys to carry out the simulation analysis of the magnetic field and structure of magnetic grid. Follow that, it establishes the overall arrangement scheme of the signal part; eventually, the whole structure of encoder is confirmed. Besides, to increase the encoder’s output accuracy, this paper proposes an error compensation model based on genetic optimization algorithm. This method has much more advantages than the traditional fitting method, for it can increase the encoder’s accuracy to 2 to 3 times and has found a feasible direction for the improvement of encoder prop erties in the future.