// calc_filt_alpha - recalculate the input filter alphavoid AC_PID::calc_filt_alpha(){ // calculate alpha float rc = 1/(2*PI*_filt_hz); _filt_alpha = _dt / (_dt + rc);}注:PI就是π,dt是一个时间间隔。_filt_hz是滤波器频率,但不知道是什么含义。求指教!