0. A 'brute force' methold of removing tip/tilt from the WFS signal.

1. summary of pr_servo_remove_tt

   // make modifed signal[s] - take out tilt-from using signal data.

   data.tt.model[a] = data.signal[s] *  data.tt_inverse_model[a][s]
   signal[s] = data.tt_mat_model[s][a] * data.tt_model[a]
   signal[s] = data.signal[s] - signal[s].

   // output primary out
   data.delta_drive[a] = pr_sign * data.inverse[a][s] * signal[s]
   data.primary_out[a] = data.delta_drive[a] * pr_gain


2. source code:

/*------------------------------------------------------------------
**  pr_servo_remove_tt() -  performs the primary loop. but first tries
**    to remove the tt information from the sigal[s] data.
**------------------------------------------------------------------
*/
static int pr_servo_remove_tt( lp_shmem_t * lp )
{
   int a, s;
   double total, out;
   double signal[AO_NUM_SENSORS];

   lp->status.lp_indicator = 0x02;
   /******************************************************************
   ** remove tiptilt information from signal[s] data using modeled
   ** tt inverse and imats.
   ******************************************************************
   */

   /*---------------------------------------------------------------
   **   tt.model[a] = signal[s] *  tt_inverse_model[a][s]
   **   tt.model is model delta drive.
   */
   for( a=0; a<AO_NUM_TT_ACTUATORS; a++)
   {
      total = 0.0;
      for (s=0; s<AO_NUM_SENSORS; s++)
         total += lp->data.tt_inverse_model[a][s] * lp->data.signal[s];
      lp->data.tt_model[a] = total;
   }

   /*---------------------------------------------------------------
   **   signal[s] = tt_mat_model[s][a] * tt_model[a]
   **   signal contains _only_ the tt information.
   */
   for (s=0; s<AO_NUM_SENSORS; s++)
   {
      total = 0.0;
      for( a=0; a<AO_NUM_TT_ACTUATORS; a++)
         total += lp->data.tt_imat_model[s][a] * lp->data.tt_model[a];
      signal[s] = total;
   }

   /*---------------------------------------------------------------
   ** signal[s] = data.signal[s] - signal[s].
   ** signal[s] is data.signal[s] with all tiptilt information removed.
   */
   for (s=0; s<AO_NUM_SENSORS; s++)
   {
      signal[s]  = lp->data.signal[s] - signal[s];
   }

   /******************************************************************
   * perform primary loop using modified signal[s]
   ******************************************************************
   */

   /*--------------------------------------------------------
   **   delta_drive[a] = pr_sign * inverse[a][s] * signal[s]
   **    Note: using modified signal[s]
   */
   for (a=0; a<AO_NUM_P_ACTUATORS; a++)
   {
      total = 0.0;
      for (s=0; s<AO_NUM_SENSORS; s++)
         total += lp->data.inverse[a][s] * signal[s];
      lp->data.delta_drive[a] = lp->parm.pr_sign * total;
   }

   /*--------------------------------------------
   ** primary_out[a] = delta_drive[a] * pr_gain
   */
   if( lp->parm.primary_servo )
   {
      for( a=0; a<AO_NUM_P_ACTUATORS; a++ )
      {
         out = lp->data.primary_out[a] + (lp->data.delta_drive[a] * lp->parm.pr_gain);
         set_primary_out( lp, a, out );
      }
   }
   return 0;
}