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