Study on a novel absolute magnetic encoder

Compared with an optical encoder, structure of magnetic rotary encoder is very simple and not affected in dust and mist condition, can be used in badly condition. But its resolution and accuracy are low and difficult to be improved by conventional methods. In order to improve the resolution of magnetic encoder, a novel encoder structure and signal processing method base on calibration are present. A radial magnetizing ring alnico is adhered to rotor of motor, while six Hall ICs are placed around the alnico evenly to sense magnetic field produced by the alnico. Magnetic encoder is calibrated using a higher resolution incremental optical encoder off-line: angle output from optical encoder and voltage from Hall ICs were sampled at the same time and transmitted to PC, relation between them can be get and stored in the ROM of MCU for look up table. Angle can be get according to voltages of Hall ICs. Magnetic encoder is designed and its accuracy can achieve to 13-bits. Its structure is very simple and cost is very low compare with an optical encoder. It can be used in most occasions.