Research On A Combined Type Magnetic Encoder

Magnetic encoder is made up with permanent magnet and hall magneto-sensor, which is a kind of angular displacement sensor with numerous advantages, for example, simple structure, thermostability, vibration and pollution resistant, miniaturized, etc. Recently, the magnetic encoder has been widely used in such as industry control, machine manufacturing, fabrics, new energy, aerospace, shipping, radar communication and other fields. With the development of control and servo technique, not only the requirements to the feedback parameters of angular displacement sensor have improved, but also the requirements to its physical properties have improved. The directions for the angular displacement sensor are high precision, high resolution, high reliability, lower cost, miniaturization, serialization and intellectualization. This paper is just based on the directions for the angular displacement sensor to doing some academic and applied works.We brought up a new structured magnetic encoder which named the combined type magnetic encoder from the structure, operating principle, solution algorithm of the existing single-pole magnetic encoder. This paper used the JMAG software to make a finite element simulation analysis after the structure determined. And used the method of magnetic shield to guarantee the lowest degree of coupling brought by the single-pole magnetic field and multi-poles magnetic field. On the other hand, for the sake of response to the requirements of simple structure and serialization, we used the magnetic conducted principle for the soft magnet in single-pole magnetic encoder. This paper built up a algorithmic system suited to the combined type magnetic encoder after analyzing the existing basic algorithm of the magnetic encoder. And the core is a algorithm of interval judgment and correction which is suited to any pair of poles combined type magnetic encoder. Temperature drift offset correction arithmetic is adduced to adapting to the change of the temperature. At the same time, index smoothing forecasting method is put forward to meet the requirements of the high speed and high response. This paper also analyzed the origins of the hysteresis error, and adduced the mathematical model of hysteresis raised by Jiles-Atherton to make a numerical analysis for the hysteresis error. Finally, we conducted experiments to test the precision, resolution, hysteresis error, and we also had a contrast experiment between the 44 and 8 pairs of poles combined type magnetic encoder. Indicated by the experiments, the precision of the 44 pairs of poles one in unidirectional rotation is ±2.5′, ±6′ in progressive rotation, and the hysteresis errorIII less than ±6′, the precision of the 8 pairs of poles one in unidirectional rotation is ±7′, ±7′ in progressive rotation, and the hysteresis error less than ±0.8′.