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