一种反正切函数的高精度算法的FPGA实现

在旋转编码器设计中常利用两个传感器去获得转子在某一位置时的一对正交输出的电压信号,然后用到arctan函数计算转角.本文研究了一种基于CORDIC算法计算arctan函数的方法,除巧妙利用右移解决算法收敛性问题外,还利用时钟信号的上升沿和下跳沿分别处理移位运算和迭代运算,使得算法的执行效率提高了一倍.最后用Cyclone的EP1C20F400C8芯片仿真实现该算法.仿真结果表明,系统稳定性好,精度高,占用资源少,能满足旋转编码器快速解码的要求.

FPGA Implementation of High Accuracy Arctangent Function Calculate Circuit

In order to design magnetic encoder,we always obtain a pair of orthogonal voltage signals using two sensors when the rotor is in a certain condition firstly,then arctangent function should be required to compute the angles.This paper studies a method of calculating arctangent function based on CORDIC algorithm.It not only makes the arithmetic being convergent tactfully through right shift,but also doubles the processing speed through.Shifting will be triggered if clock’s positive edge coming,else iterations will be triggered.Finally,an EP1C20F400C8 chip belonging to Cyclone of Altera company is chosen to finish the implementation.The simulation results indicate that output errors are less and the stability is good.In addition,because only a few of hardware resources are occupied,so the system can realize decoding fastly.