基于FPGA的高精度磁编码器设计

Design of High Accuracy Magnetic Encoder Based on FPGA

磁编码器主要用于伺服电机系统的转角和转速测量,针对目前产品精度和分辨率相对较低的现状,提出一种基于FPGA实现的标定查表法细分方案。首先将三路磁头相差120°放置,使磁编码器输出3路相差120°的差分正弦信号,并通过FPGA进行卦限判断,选取线性度最好的一路信号进行信号处理,从而有效地避免了正弦信号的死区。同时利用FPGA对卦限信息和磁编码器输出信号的A/D转换信息进行处理,作为EEPROM的地址信息进行硬件查表,实现对磁编码器信号的倍频处理,从而提高了磁编码器的分辨率和测量精度,可实现每个周期4 096份的倍频。

The magnetic encoder is widely used in the domain of measuring the rotate angle and speed of servomotor system. In order to improve its low resolution and accuracy, a design based on FPGA to realize the looking-up table method was proposed. Three sine signals whose differentiate phase were 120° were output by putting their magnetic heads in an offset of 120°. FPGA was used to judge the octant, and the signal with best linearity was acquired, so the dead region of sine signal was avoid efficiently. As the address of EEPROM, which was used for looking-up table, the information of octant and signals of magnetic encoder which were convened by A/D converter were dealt by FPGA. And the frequency multiplication for magnetic encoder was completed. So the resolution and accuracy of magnetic encoder were improved, 4096 multiple frequencies can be achieved in per cycle.