component clarkeinv "Inverse Clarke transform";
description """The inverse Clarke transform can be used to translate
a vector quantity from Cartesian coordinate system to a three phase
system (three components 120 degrees apart).""";
see_also """\\fBclarke2\\fR and \\fBclarke3\\fR for the forward transform.""";
pin in float x;
pin in float y "cartesian components of input";
pin in float h "homopolar component of input (usually zero)";
pin out float a;
pin out float b;
pin out float c "three phase output vector";
function _;
license "GPL";
;;

/* for the details, google "clarke transform", or see section 3 of
   http://focus.ti.com/lit/an/bpra048/bpra048.pdf and/or appendix B of
   http://www.esat.kuleuven.be/electa/publications/fulltexts/pub_1610.pdf
*/

#define K1 (0.500000000000000)  /* 1/2       */
#define K2 (0.866025403784439)  /* sqrt(3)/2 */
#define K3 (0.707106781186547)  /* 1/sqrt(2) */

FUNCTION(_) {
    a =  x +  K3*h;
    b = -K1*x + K2*y + K3*h;
    c = -K1*x - K2*y + K3*h;
}