/*
* Transforms a spherical vector from 'spb' to 'spe' into an inverse Euler
* transformation. Returns true if the transformation was successful.
*/
static bool
spherevector_to_euler_inv(SEuler *se, const SPoint *spb, const SPoint *spe)
{
if (spoint_eq(spb, spe))
{
return false;
}
else
{
Vector3D vbeg, vend, vtmp;
SPoint spt[2];
SEuler set;
spoint_vector3d(&vbeg, spb);
spoint_vector3d(&vend, spe);
vector3d_cross(&vtmp, &vbeg, &vend);
vector3d_spoint(&spt[0], &vtmp);
set.phi = -spt[0].lng - PIH;
set.theta = spt[0].lat - PIH;
set.psi = 0.0;
seuler_set_zxz(&set);
euler_spoint_trans(&spt[1], spb, &set);
set.psi = -spt[1].lng;
memcpy((void *) se, (void *) &set, sizeof(SEuler));
}
return true;
}
/* bring dcm matrix in order - adjust values to make
* orthonormal (or at least closer to orthonormal) */
static void dcm_orthonormalize(float dcm[3][3]){
//err = X . Y , X = X - err/2 * Y , Y = Y - err/2 * X (DCMDraft2 Eqn.19)
float err = vector3d_dot((float*)(dcm[0]),(float*)(dcm[1]));
float delta[2][3];
vector3d_scale(-err/2,(float*)(dcm[1]),(float*)(delta[0]));
vector3d_scale(-err/2,(float*)(dcm[0]),(float*)(delta[1]));
vector3d_add((float*)(dcm[0]),(float*)(delta[0]),(float*)(dcm[0]));
vector3d_add((float*)(dcm[1]),(float*)(delta[1]),(float*)(dcm[1]));
//Z = X x Y (DCMDraft2 Eqn. 20) ,
vector3d_cross((float*)(dcm[0]),(float*)(dcm[1]),(float*)(dcm[2]));
//re-nomralization
vector3d_normalize((float*)(dcm[0]));
vector3d_normalize((float*)(dcm[1]));
vector3d_normalize((float*)(dcm[2]));
}
//rotate DCM matrix by a small rotation given by angular rotation vector w
//see http://gentlenav.googlecode.com/files/DCMDraft2.pdf
static void dcm_rotate(float dcm[3][3], float w[3]){
//float W[3][3];
//creates equivalent skew symetric matrix plus identity matrix
//vector3d_skew_plus_identity((float*)w,(float*)W);
//float dcmTmp[3][3];
//matrix_multiply(3,3,3,(float*)W,(float*)dcm,(float*)dcmTmp);
uint32_t i;
float dR[3];
//update matrix using formula R(t+1)= R(t) + dR(t) = R(t) + w x R(t)
for(i=0;i<3;i++){
vector3d_cross(w, dcm[i], dR);
vector3d_add(dcm[i], dR, dcm[i]);
}
//make matrix orthonormal again
dcm_orthonormalize(dcm);
}
void MMA8451::update_stillness(const float *result){
float cross[3];
float filtered[3];
float modulus_cross;
float modulus_delta;
uint32_t i = 0;
/* update array of filters */
for (i=0; i<3; i++)
filtered[i] = abeta[i].update(result[i], *still_flen);
/* calculate differences between vectors */
vector3d_cross(result, filtered, cross);
modulus_cross = vector3d_modulus(cross);
modulus_delta = vector3d_modulus(result) - vector3d_modulus(filtered);
if ((fabsf(modulus_delta) > *still_thr) || (fabsf(modulus_cross) > *still_thr))
immobile = false;
}
float8 spoint_dist ( const SPoint * p1, const SPoint * p2 )
{
float8 dl = p1->lng - p2->lng;
float8 f = ( ( sin( p1->lat )*sin( p2->lat ) + cos( p1->lat )*cos( p2->lat )*cos( dl ) ) );
if( FPeq( f, 1.0 ) ){
/* for small distances */
Vector3D v1, v2, v3;
spoint_vector3d(&v1, p1);
spoint_vector3d(&v2, p2);
vector3d_cross( &v3, &v1, &v2 );
f = vector3d_length(&v3);
} else {
f = acos(f);
}
if ( FPzero(f) ){
return 0.0;
} else {
return f;
}
}
/* accelerations in g (scale does not matter because values will be normolized),
* angular rates in rad/s (scale is MATTER),
* magnetic flux in uT (scale does not matter because values will be normolized),
* time in s */
void dcmUpdate(float *acc, float *gyro, float *mag, float imu_interval){
uint32_t i = 0;
float Kacc[3]; //K(b) vector according to accelerometer in body's coordinates
float Imag[3]; //I(b) vector accordng to magnetometer in body's coordinates
float w[3]; //gyro rates (angular velocity of a global vector in local coordinates)
float wA[3]; //correction vector to bring dcmEst's K vector closer to Acc
float wM[3]; //correction vector to bring dcmEst's I vector closer
//interval since last call
//imu_interval_ms = itg3200_period;
//---------------
// I,J,K unity vectors of global coordinate system I-North,J-West,K-zenith
// i,j,k unity vectors of body's coordiante system i-"nose", j-"left wing", k-"top"
//---------------
// [I.i , I.j, I.k]
// DCM = [J.i , J.j, J.k]
// [K.i , K.j, K.k]
//---------------
//Acelerometer
//---------------
/* Accelerometer measures gravity vector G in body coordinate system
Gravity vector is the reverse of K unity vector of global system
expressed in local coordinates K vector coincides with the z
coordinate of body's i,j,k vectors expressed in global
coordinates (K.i , K.j, K.k)
Acc can estimate global K vector(zenith) measured in body's coordinate
systems (the reverse of gravitation vector) */
// Kacc[0] = -xacc;
// Kacc[1] = -yacc;
// Kacc[2] = -zacc;
/* Поскольку на вход функции мы подаем значения измеренных ускорений по осям,
а не вектор гравитации, то ничего инвертировать не надо.
Вектор кажущегося ускорения совпадает с зенитным вектором К. */
for (i = 0; i<3; i++)
Kacc[i] = acc[i];
nue2nwu(Kacc);
vector3d_normalize(Kacc);
// calculate correction vector to bring dcmEst's K vector closer to Acc
// vector (K vector according to accelerometer)
// wA = Kgyro x Kacc , rotation needed to bring Kacc to Kgyro
vector3d_cross(dcmEst[2], Kacc, wA);
//---------------
//Magnetomer
//---------------
// calculate correction vector to bring dcmEst's I vector closer
// to Mag vector (I vector according to magnetometer)
// in the absense of magnetometer let's assume North vector (I) is
// always in XZ plane of the device (y coordinate is 0)
// Imag[0] = sqrtf(1 - dcmEst[0][2] * dcmEst[0][2]);
// Imag[1] = 0;
// Imag[2] = dcmEst[0][2];
for (i = 0; i<3; i++)
Imag[i] = mag[i];
nue2nwu(Imag);
/* Проработать комплексирование с нижним рядом DCM вместо вектора
* гравитации. Какие-то непонятные результаты получаются, или я их
* готовить не умею. */
float tmpM[3];
vector3d_normalize(Imag);
//vector3d_cross(Kacc, Imag, tmpM);
vector3d_cross(dcmEst[2], Imag, tmpM);
vector3d_normalize(tmpM);
//vector3d_cross(tmpM, Kacc, Imag);
vector3d_cross(tmpM, dcmEst[2], Imag);
vector3d_normalize(Imag);
// wM = Igyro x Imag, roation needed to bring Imag to Igyro
vector3d_cross(dcmEst[0], Imag, wM);
//---------------
//dcmEst
//---------------
//gyro rate direction is usually specified (in datasheets) as the device's(body's) rotation
//about a fixed earth's (global) frame, if we look from the perspective of device then
//the global vectors (I,K,J) rotation direction will be the inverse
//rotation rate about accelerometer's X axis (GY output)
//rotation rate about accelerometer's Y axis (GX output)
//rotation rate about accelerometer's Z axis (GZ output)
for (i = 0; i<3; i++)
w[i] = -gyro[i];
nue2nwu(w);
/* correction factors for accelerometer and mognetometer weights */
float magcor, acccor;
if (1 == GlobalFlags.gyro_cal){
acccor = 10;
magcor = 10;
}
else{
acccor = 1;
magcor = 1;
}
float aw = *accweight * acccor;
float mw = *magweight * magcor;
for(i=0; i<3; i++){
w[i] *= imu_interval; //scale by elapsed time to get angle in radians
//compute weighted average with the accelerometer correction vector
w[i] = (w[i] + aw * wA[i] + mw * wM[i]) /
(1.0f + aw + mw);
}
dcm_rotate(dcmEst, w);
imu_step++;
}
