void acc_update( void )
{
volatile avr32_adc_t *adc = &AVR32_ADC;
// start + get from adc
acc_get_value(adc, &acc.m) ;
// ak = acceleration = m - k
xyz_diff( acc.m , acc.k, &acc.ak ) ;
acc.ak2 = xyz_sumsq( acc.ak ) ;
if ( is_acc_slow() ) {
// update g for next move
acc.g.x = acc.m.x ;
acc.g.y = acc.m.y ;
acc.g.z = acc.m.z ;
}
else {
xyz_diff( acc.m , acc.g, &acc.ag ) ;
xyz_round0( acc.ag , 16, &acc.ag ) ;
xyz_add( acc.s , acc.ag, &acc.s ) ;
//xyz_round0( acc.s , 256, &acc.s ) ;
//print_dbg("m = "); print_xyz( acc.m ) ;
//print_dbg("k = "); print_xyz( acc.k ) ;
//print_dbg("g = "); print_xyz( acc.g ) ;
//print_dbg("ag = "); print_xyz( acc.ag ) ;
//print_dbg("s = "); print_xyz( acc.s ) ;
//print_dbg("\r\n");
////acc.s2 = xyz_sumsq( acc.s ) ;
//print_dbg("s2 = 0x"); print_dbg_hex(acc.s2); print_dbg("\r\n");
}
}
// return norm(a - b)
double
xyz_distance( const xyz_t * const a, const xyz_t * const b )
{
xyz_t diff;
xyz_diff( &diff, a, b);
return xyz_norm( &diff );
}
int project_o_tron(aero_table_output_t * out,
aero_model_t * model,
quat_t ref_to_body, int w, int h, int *pix_buf_panel)
{
int n = model->n_panels;
// *** Input parameters
xyz_t UU e_v_ref = { 1, 0, 0 }; // velocity unit vector in ref frame
// todo: check that is normalized
double res = 0.001 / MEGARES; // Resolution
double sig_n = 0.8; // normal momentum exchange coeff
double sig_t = 0.8; // tangential momentum exchange coeff
// *** Let's choose a new "freestream" frame so that the velocity vector is just +X
quat_t body_to_fs;
xyz_t e_v_fs = { 1, 0, 0 };
// Don't need to rotate at all, the frames are already aligned
// Now form the quaternion rotating the body frame to the freestream frame
quat_inv(&body_to_fs, &ref_to_body);
// *** Rotate "everything" into the new frame
//
// Rotate the center of mass
xyz_t cg_fs;
rot_vec_by_quat_a2b(&cg_fs, &body_to_fs, &model->cg);
// Rotate the panels' coordinates
panel_t panels_fs[model->n_panels];
for (int i = 0; i < n; i++) {
rot_vec_by_quat_a2b(&panels_fs[i].origin, &body_to_fs,
&model->panels[i].origin);
rot_vec_by_quat_a2b(&panels_fs[i].side_a, &body_to_fs,
&model->panels[i].side_a);
rot_vec_by_quat_a2b(&panels_fs[i].side_b, &body_to_fs,
&model->panels[i].side_b);
}
// Find the centroids
xyz_t centroid_fs[n];
for (int i = 0; i < n; i++) {
centroid_fs[i] = panels_fs[i].origin;
// This handy function does (a <= a*A + b*B + c*C)
xyz_sum_scale(¢roid_fs[i], 1, &panels_fs[i].side_a, 0.5,
&panels_fs[i].side_b, 0.5);
}
// Sort by the X coordinate of the centroids
struct indirect_element sort_list[n];
for (int i = 0; i < n; i++) {
sort_list[i].index = i;
sort_list[i].val = centroid_fs[i].x;
}
qsort(sort_list, n, sizeof(sort_list[0]), compare_indirect_elements);
double *pix_buf_x = malloc(w * h * sizeof(double));
// Holds the fs frame X coordinate
// of the panel element at each pixel
if (!pix_buf_x) {
fprintf(stderr, "Unable to allocate %zu bytes for pix_buf_x\n",
w * h * sizeof(double));
return 1;
}
// Iterate over the panels, rearmost centroid first
for (int i = 0; i < n; i++) { // if(sort_list[i].index==0){
panel_t *p = &panels_fs[sort_list[i].index];
//printf("Panel %d:::\n",sort_list[i].index);
double res_a = res / xyz_norm(&p->side_a) / sqrt(2);
double res_b = res / xyz_norm(&p->side_b) / sqrt(2);
// Iterate over side a
for (double a = 0; a <= 1; a += res_a) {
// Iterate over side b
for (double b = 0; b <= 1; b += res_b) {
xyz_t panel_cell = p->origin;
xyz_sum_scale(&panel_cell, 1, &p->side_a, a,
&p->side_b, b);
int pix_y =
(int)round(panel_cell.y / res + w / 2);
int pix_z =
(int)round(panel_cell.z / res + h / 2);
pix_buf_panel[pix_z + pix_y * w] =
sort_list[i].index + 1;
pix_buf_x[pix_z + pix_y * w] = panel_cell.x;
// printf("\t%+7.4f\t%+7.4f\t%d\t%d\n",panel_cell.y,panel_cell.z,pix_y,pix_z);
}
}
}
// Find the unit normal vector in fs frame, and e_v.e_n for all panels
xyz_t e_n_fs[n];
double e_v_dot_e_n[n];
for (int p = 0; p < n; p++) {
xyz_cross(&e_n_fs[p], &panels_fs[p].side_a,
&panels_fs[p].side_b);
xyz_normalize_self(&e_n_fs[p]);
e_v_dot_e_n[p] = xyz_dot(&e_n_fs[p], &e_v_fs);
// if (e_v_dot_e_n[p] < 0)
// printf("e_v dot e_n negative for panel %d\n",p);
}
// double A = 0;
int n_pix[n];
memset(n_pix, 0, sizeof(n_pix));
xyz_t panel_sum_pos[n];
memset(panel_sum_pos, 0, sizeof(panel_sum_pos));
//printf("sizeof(n_pix)=%zu\n",sizeof(n_pix));
xyz_t F_fs = {0, 0, 0};
xyz_t T_fs = {0, 0, 0};
// Now iterate over the pixels
for (int pix_y = 0; pix_y < w; pix_y++)
for (int pix_z = 0; pix_z < h; pix_z++) {
int p = pix_buf_panel[pix_z + pix_y * w];
if (p) {
// There is a panel at this pixel.
p--; // Actual panel index number is one less
if (e_v_dot_e_n[p] < 0) {
// Skip panels facing the wrong way
continue;
}
n_pix[p]++;
// Find the coordinates in the fs frame
xyz_t fs_p;
fs_p.x = pix_buf_x[pix_z * w + pix_y];
fs_p.y = (pix_y - w / 2) * res;
fs_p.z = (pix_z - h / 2) * res;
// Where is it wrt the center of mass?
xyz_t r_from_cg_fs;
xyz_diff(&r_from_cg_fs, &fs_p, &cg_fs);
// Let's compute the forces on this element
// ref: NASA SP-8058 eq 2-2 (page 5).
// Dynamic pressure (1/2 rho v^2) factored out, hence leading 2 *
xyz_t dF = { 0, 0, 0 };
xyz_sum_scale(&dF, 0,
&e_n_fs[p],
2 * -1 * res * res * (2 - sig_n -
sig_t) *
xyz_dot(&e_v_fs, &e_n_fs[p]),
&e_v_fs, 2 * -1 * res * res * sig_t);
// Torque contribution from this element
xyz_t dT;
xyz_cross(&dT, &r_from_cg_fs, &dF);
xyz_sum(&F_fs, &F_fs, &dF);
xyz_sum(&T_fs, &T_fs, &dT);
}
}
rot_vec_by_quat_b2a(&out->force, &body_to_fs, &F_fs);
rot_vec_by_quat_b2a(&out->torque, &body_to_fs, &T_fs);
printf("F = %f %f %f (norm=%f)\n",out->force.x, out->force.y, out->force.z, xyz_norm(&out->force));
printf("T = %f %f %f (norm=%f)\n",out->torque.x, out->torque.y, out->torque.z, xyz_norm(&out->torque));
// printf("%d pixels dropped due to e_v dot e_n negative\n",n_pix);
free(pix_buf_x);
return 0;
}
