UVW 3 phases Brushless DC motor control
Dependencies: QEI mbed-rtos mbed
Fork of DCmotor by
Diff: fast_math.cpp
- Revision:
- 12:a4b17bb682eb
- Child:
- 13:791e20f1af43
diff -r 9747752435d1 -r a4b17bb682eb fast_math.cpp --- /dev/null Thu Jan 01 00:00:00 1970 +0000 +++ b/fast_math.cpp Fri Dec 21 22:06:56 2012 +0000 @@ -0,0 +1,51 @@ +#include "mbed.h" +#include "fast_math.h" + +unsigned short sin60[DEG60+1]; // sin table from 0 to 60 deg. (max precision error is 0.003%) + +long _sin(unsigned short th){ // return( 65535*sin(th) ), th=rad*DEG60/(PI/3)=rad*(512*3)/PI (0<=rad<2*PI) +// init_sin60(); +// if( th>2.*PI ){ th -= 2*PI*(float)((int)(th/(2.*PI)));} +// th_int = (unsigned short)(th/(PI/3.)*(float)DEG60+0.5); // rad to deg +// sin = (float)_sin(th)/65535.; + unsigned short f_minus; + long x; + + if( th>=DEG60*3){ f_minus = 1; th -= DEG60*3;} // if th>=180deg, th = th - 180deg; + else{ f_minus = 0;} // else , f_minus = on. + + if( th<DEG60 ){ // th<60deg? + x = sin60[th]; // sin(th) + }else if( th<DEG60*2 ){ // 60<=th<120deg? + x = sin60[DEG60*2-th] + sin60[th-DEG60]; // sin(th)=sin(th+60)+sin(th-60)=sin(180-(th+60))+sin(th-60) because sin(th+60)=s/2+c*root(3)/2, sin(th-60)=s/2-c*root(3)/2. + }else{// if( th<180 ) // 120<=th<180deg? + x = sin60[DEG60*3-th]; // sin(60-(th-120))=sin(180-th) + } + if( f_minus==1 ){ x = -x;} + return(x); +} + +long _cos(unsigned short th){ // return( 65535*sin(th) ), th=rad*DEG60/(PI/3)=rad*(512*3)/PI (0<=rad<2*PI) + th += DEG60*3/2; + if( th>=DEG60*6 ){ th -= DEG60*6;} + return( _sin(th) ); +} + +void init_fast_math(){ // sin0-sin60deg; 0deg=0, 60deg=512 + int i; + + for( i=0;i<=DEG60;i++ ){ // set sin table from 0 to 60 deg.. +// sin60[i] = (unsigned short)(sin((float)i/512.*PI/3.)); + sin60[i] = (unsigned short)(65535.*sinf((float)i/(float)DEG60*PI/3.)); + } +} + +#if 0 +//float norm(float x[0], float x[1]){ // 2ノルムを計算 +// return(sqrt(x[0]*x[0]+x[1]*x[1])); +//} +float sqrt2(float x){ // √xのx=1まわりのテイラー展開 √x = 1 + 1/2*(x-1) -1/4*(x-1)^2 + ... +// return((1+x)*0.5); // 一次近似 + return(x+(1-x*x)*0.25); // 二次近似 +} +#endif \ No newline at end of file