src/FDM/LaRCsim/ls_aux.c

   1 /***************************************************************************
   2
   3     TITLE:              ls_aux
   4
   5 ----------------------------------------------------------------------------
   6
   7     FUNCTION:   Atmospheric and auxilary relationships for LaRCSim EOM
   8
   9 ----------------------------------------------------------------------------
  10
  11     MODULE STATUS:      developmental
  12
  13 ----------------------------------------------------------------------------
  14
  15     GENEALOGY:  Created 9208026 as part of C-castle simulation project.
  16
  17 ----------------------------------------------------------------------------
  18
  19     DESIGNED BY:        B. Jackson
  20
  21     CODED BY:           B. Jackson
  22
  23     MAINTAINED BY:      B. Jackson
  24
  25 ----------------------------------------------------------------------------
  26
  27     MODIFICATION HISTORY:
  28
  29     DATE    PURPOSE
  30
  31     931006  Moved calculations of auxiliary accelerations from here
  32             to ls_accel.c and corrected minus sign in front of A_Y_Pilot
  33             contribution from Q_body*P_body*D_X_pilot term.         EBJ
  34     931014  Changed calculation of Alpha from atan to atan2 so sign is correct.
  35                                                                     EBJ
  36     931220  Added calculations for static and total temperatures & pressures,
  37             as well as dynamic and impact pressures and calibrated airspeed.
  38                                                                     EBJ
  39     940111  Changed #included header files from old "ls_eom.h" to newer
  40             "ls_types.h", "ls_constants.h" and "ls_generic.h".      EBJ
  41
  42     950207  Changed use of "abs" to "fabs" in calculation of signU. EBJ
  43
  44     950228  Fixed bug in calculation of beta_dot.                   EBJ
  45
  46     CURRENT RCS HEADER INFO:
  47
  48 $Header$
  49 $Log$
  50 Revision 1.1  1999/04/05 21:32:45  curt
  51 Initial revision
  52
  53 Revision 1.4  1998/08/24 20:09:26  curt
  54 Code optimization tweaks from Norman Vine.
  55
  56 Revision 1.3  1998/08/06 12:46:38  curt
  57 Header change.
  58
  59 Revision 1.2  1998/01/19 18:40:24  curt
  60 Tons of little changes to clean up the code and to remove fatal errors
  61 when building with the c++ compiler.
  62
  63 Revision 1.1  1997/05/29 00:09:54  curt
  64 Initial Flight Gear revision.
  65
  66  * Revision 1.12  1995/02/28  17:57:16  bjax
  67  * Corrected calculation of beta_dot. EBJ
  68  *
  69  * Revision 1.11  1995/02/07  21:09:47  bjax
  70  * Corrected calculation of "signU"; was using divide by
  71  * abs(), which returns an integer; now using fabs(), which
  72  * returns a double.  EBJ
  73  *
  74  * Revision 1.10  1994/05/10  20:09:42  bjax
  75  * Fixed a major problem with dx_pilot_from_cg, etc. not being calculated locally.
  76  *
  77  * Revision 1.9  1994/01/11  18:44:33  bjax
  78  * Changed header files to use ls_types, ls_constants, and ls_generic.
  79  *
  80  * Revision 1.8  1993/12/21  14:36:33  bjax
  81  * Added calcs of pressures, temps and calibrated airspeeds.
  82  *
  83  * Revision 1.7  1993/10/14  11:25:38  bjax
  84  * Changed calculation of Alpha to use 'atan2' instead of 'atan' so alphas
  85  * larger than +/- 90 degrees are calculated correctly.                 EBJ
  86  *
  87  * Revision 1.6  1993/10/07  18:45:56  bjax
  88  * A little cleanup; no significant changes. EBJ
  89  *
  90  * Revision 1.5  1993/10/07  18:42:22  bjax
  91  * Moved calculations of auxiliary accelerations here from ls_aux, and
  92  * corrected sign on Q_body*P_body*d_x_pilot term of A_Y_pilot calc.  EBJ
  93  *
  94  * Revision 1.4  1993/07/16  18:28:58  bjax
  95  * Changed call from atmos_62 to ls_atmos. EBJ
  96  *
  97  * Revision 1.3  1993/06/02  15:02:42  bjax
  98  * Changed call to geodesy calcs from ls_geodesy to ls_geoc_to_geod.
  99  *
 100  * Revision 1.1  92/12/30  13:17:39  bjax
 101  * Initial revision
 102  *
 103
 104
 105 ----------------------------------------------------------------------------
 106
 107     REFERENCES: [ 1] Shapiro, Ascher H.: "The Dynamics and Thermodynamics
 108                         of Compressible Fluid Flow", Volume I, The Ronald
 109                         Press, 1953.
 110
 111 ----------------------------------------------------------------------------
 112
 113                 CALLED BY:
 114
 115 ----------------------------------------------------------------------------
 116
 117                 CALLS TO:
 118
 119 ----------------------------------------------------------------------------
 120
 121                 INPUTS:
 122
 123 ----------------------------------------------------------------------------
 124
 125                 OUTPUTS:
 126
 127 --------------------------------------------------------------------------*/
 128 #include "ls_types.h"
 129 #include "ls_constants.h"
 130 #include "ls_generic.h"
 131
 132 #include "ls_aux.h"
 133
 134 #include "atmos_62.h"
 135 #include "ls_geodesy.h"
 136 #include "ls_gravity.h"
 137
 138 #include <math.h>
 139
 140
 141 void ls_aux( void ) {
 142
 143         SCALAR  dx_pilot_from_cg, dy_pilot_from_cg, dz_pilot_from_cg;
 144         /* SCALAR inv_Mass; */
 145         SCALAR  v_XZ_plane_2, signU, v_tangential;
 146         /* SCALAR inv_radius_ratio; */
 147         SCALAR  cos_rwy_hdg, sin_rwy_hdg;
 148         SCALAR  mach2, temp_ratio, pres_ratio;
 149         SCALAR  tmp;
 150
 151     /* update geodetic position */
 152
 153         ls_geoc_to_geod( Lat_geocentric, Radius_to_vehicle,
 154                                 &Latitude, &Altitude, &Sea_level_radius );
 155         Longitude = Lon_geocentric - Earth_position_angle;
 156
 157     /* Calculate body axis velocities */
 158
 159         /* Form relative velocity vector */
 160
 161         V_north_rel_ground = V_north;
 162         V_east_rel_ground  = V_east
 163           - OMEGA_EARTH*Sea_level_radius*cos( Lat_geocentric );
 164         V_down_rel_ground  = V_down;
 165
 166         V_north_rel_airmass = V_north_rel_ground - V_north_airmass;
 167         V_east_rel_airmass  = V_east_rel_ground  - V_east_airmass;
 168         V_down_rel_airmass  = V_down_rel_ground  - V_down_airmass;
 169
 170         U_body = T_local_to_body_11*V_north_rel_airmass
 171           + T_local_to_body_12*V_east_rel_airmass
 172             + T_local_to_body_13*V_down_rel_airmass + U_gust;
 173         V_body = T_local_to_body_21*V_north_rel_airmass
 174           + T_local_to_body_22*V_east_rel_airmass
 175             + T_local_to_body_23*V_down_rel_airmass + V_gust;
 176         W_body = T_local_to_body_31*V_north_rel_airmass
 177           + T_local_to_body_32*V_east_rel_airmass
 178             + T_local_to_body_33*V_down_rel_airmass + W_gust;
 179
 180         V_rel_wind = sqrt(U_body*U_body + V_body*V_body + W_body*W_body);
 181
 182
 183     /* Calculate alpha and beta rates   */
 184
 185         v_XZ_plane_2 = (U_body*U_body + W_body*W_body);
 186
 187         if (U_body == 0)
 188                 signU = 1;
 189         else
 190                 signU = U_body/fabs(U_body);
 191
 192         if( (v_XZ_plane_2 == 0) || (V_rel_wind == 0) )
 193         {
 194                 Alpha_dot = 0;
 195                 Beta_dot = 0;
 196         }
 197         else
 198         {
 199                 Alpha_dot = (U_body*W_dot_body - W_body*U_dot_body)/
 200                   v_XZ_plane_2;
 201                 Beta_dot = (signU*v_XZ_plane_2*V_dot_body
 202                   - V_body*(U_body*U_dot_body + W_body*W_dot_body))
 203                     /(V_rel_wind*V_rel_wind*sqrt(v_XZ_plane_2));
 204         }
 205
 206     /* Calculate flight path and other flight condition values */
 207
 208         if (U_body == 0)
 209                 Alpha = 0;
 210         else
 211                 Alpha = atan2( W_body, U_body );
 212
 213         Cos_alpha = cos(Alpha);
 214         Sin_alpha = sin(Alpha);
 215
 216         if (V_rel_wind == 0)
 217                 Beta = 0;
 218         else
 219                 Beta = asin( V_body/ V_rel_wind );
 220
 221         Cos_beta = cos(Beta);
 222         Sin_beta = sin(Beta);
 223
 224         V_true_kts = V_rel_wind * V_TO_KNOTS;
 225
 226         V_ground_speed = sqrt(V_north_rel_ground*V_north_rel_ground
 227                               + V_east_rel_ground*V_east_rel_ground );
 228
 229         V_rel_ground = sqrt(V_ground_speed*V_ground_speed
 230                             + V_down_rel_ground*V_down_rel_ground );
 231
 232         v_tangential = sqrt(V_north*V_north + V_east*V_east);
 233
 234         V_inertial = sqrt(v_tangential*v_tangential + V_down*V_down);
 235
 236         if( (V_ground_speed == 0) && (V_down == 0) )
 237           Gamma_vert_rad = 0;
 238         else
 239           Gamma_vert_rad = atan2( -V_down, V_ground_speed );
 240
 241         if( (V_north_rel_ground == 0) && (V_east_rel_ground == 0) )
 242           Gamma_horiz_rad = 0;
 243         else
 244           Gamma_horiz_rad = atan2( V_east_rel_ground, V_north_rel_ground );
 245
 246         if (Gamma_horiz_rad < 0)
 247           Gamma_horiz_rad = Gamma_horiz_rad + 2*PI;
 248
 249     /* Calculate local gravity  */
 250
 251         ls_gravity( Radius_to_vehicle, Lat_geocentric, &Gravity );
 252
 253     /* call function for (smoothed) density ratio, sonic velocity, and
 254            ambient pressure */
 255
 256         ls_atmos(Altitude, &Sigma, &V_sound,
 257                  &Static_temperature, &Static_pressure);
 258
 259         Density = Sigma*SEA_LEVEL_DENSITY;
 260
 261         Mach_number = V_rel_wind / V_sound;
 262
 263         V_equiv = V_rel_wind*sqrt(Sigma);
 264
 265         V_equiv_kts = V_equiv*V_TO_KNOTS;
 266
 267     /* calculate temperature and pressure ratios (from [1]) */
 268
 269         mach2 = Mach_number*Mach_number;
 270         temp_ratio = 1.0 + 0.2*mach2;
 271         tmp = 3.5;
 272         pres_ratio = pow( temp_ratio, tmp );
 273
 274         Total_temperature = temp_ratio*Static_temperature;
 275         Total_pressure    = pres_ratio*Static_pressure;
 276
 277     /* calculate impact and dynamic pressures */
 278
 279         Impact_pressure = Total_pressure - Static_pressure;
 280
 281         Dynamic_pressure = 0.5*Density*V_rel_wind*V_rel_wind;
 282
 283     /* calculate calibrated airspeed indication */
 284
 285         V_calibrated = sqrt( 2.0*Dynamic_pressure / SEA_LEVEL_DENSITY );
 286         V_calibrated_kts = V_calibrated*V_TO_KNOTS;
 287
 288         Centrifugal_relief = 1 - v_tangential/(Radius_to_vehicle*Gravity);
 289
 290 /* Determine location in runway coordinates */
 291
 292         Radius_to_rwy = Sea_level_radius + Runway_altitude;
 293         cos_rwy_hdg = cos(Runway_heading*DEG_TO_RAD);
 294         sin_rwy_hdg = sin(Runway_heading*DEG_TO_RAD);
 295
 296         D_cg_north_of_rwy = Radius_to_rwy*(Latitude - Runway_latitude);
 297         D_cg_east_of_rwy = Radius_to_rwy*cos(Runway_latitude)
 298                 *(Longitude - Runway_longitude);
 299         D_cg_above_rwy  = Radius_to_vehicle - Radius_to_rwy;
 300
 301         X_cg_rwy = D_cg_north_of_rwy*cos_rwy_hdg
 302           + D_cg_east_of_rwy*sin_rwy_hdg;
 303         Y_cg_rwy =-D_cg_north_of_rwy*sin_rwy_hdg
 304           + D_cg_east_of_rwy*cos_rwy_hdg;
 305         H_cg_rwy = D_cg_above_rwy;
 306
 307         dx_pilot_from_cg = Dx_pilot - Dx_cg;
 308         dy_pilot_from_cg = Dy_pilot - Dy_cg;
 309         dz_pilot_from_cg = Dz_pilot - Dz_cg;
 310
 311         D_pilot_north_of_rwy = D_cg_north_of_rwy
 312           + T_local_to_body_11*dx_pilot_from_cg
 313             + T_local_to_body_21*dy_pilot_from_cg
 314               + T_local_to_body_31*dz_pilot_from_cg;
 315         D_pilot_east_of_rwy  = D_cg_east_of_rwy
 316           + T_local_to_body_12*dx_pilot_from_cg
 317             + T_local_to_body_22*dy_pilot_from_cg
 318               + T_local_to_body_32*dz_pilot_from_cg;
 319         D_pilot_above_rwy    = D_cg_above_rwy
 320           - T_local_to_body_13*dx_pilot_from_cg
 321             - T_local_to_body_23*dy_pilot_from_cg
 322               - T_local_to_body_33*dz_pilot_from_cg;
 323
 324         X_pilot_rwy =  D_pilot_north_of_rwy*cos_rwy_hdg
 325           + D_pilot_east_of_rwy*sin_rwy_hdg;
 326         Y_pilot_rwy = -D_pilot_north_of_rwy*sin_rwy_hdg
 327           + D_pilot_east_of_rwy*cos_rwy_hdg;
 328         H_pilot_rwy =  D_pilot_above_rwy;
 329
 330 /* Calculate Euler rates */
 331
 332         Sin_phi = sin(Phi);
 333         Cos_phi = cos(Phi);
 334         Sin_theta = sin(Theta);
 335         Cos_theta = cos(Theta);
 336         Sin_psi = sin(Psi);
 337         Cos_psi = cos(Psi);
 338
 339         if( Cos_theta == 0 )
 340           Psi_dot = 0;
 341         else
 342           Psi_dot = (Q_total*Sin_phi + R_total*Cos_phi)/Cos_theta;
 343
 344         Theta_dot = Q_total*Cos_phi - R_total*Sin_phi;
 345         Phi_dot = P_total + Psi_dot*Sin_theta;
 346
 347 /* end of ls_aux */
 348
 349 }
 350 /*************************************************************************/