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