1 /***************************************************************************
5 ----------------------------------------------------------------------------
7 FUNCTION: Atmospheric and auxilary relationships for LaRCSim EOM
9 ----------------------------------------------------------------------------
11 MODULE STATUS: developmental
13 ----------------------------------------------------------------------------
15 GENEALOGY: Created 9208026 as part of C-castle simulation project.
17 ----------------------------------------------------------------------------
19 DESIGNED BY: B. Jackson
23 MAINTAINED BY: B. Jackson
25 ----------------------------------------------------------------------------
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.
36 931220 Added calculations for static and total temperatures & pressures,
37 as well as dynamic and impact pressures and calibrated airspeed.
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
42 950207 Changed use of "abs" to "fabs" in calculation of signU. EBJ
44 950228 Fixed bug in calculation of beta_dot. EBJ
46 CURRENT RCS HEADER INFO:
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.
54 Revision 1.1 1997/05/29 00:09:54 curt
55 Initial Flight Gear revision.
57 * Revision 1.12 1995/02/28 17:57:16 bjax
58 * Corrected calculation of beta_dot. EBJ
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
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.
68 * Revision 1.9 1994/01/11 18:44:33 bjax
69 * Changed header files to use ls_types, ls_constants, and ls_generic.
71 * Revision 1.8 1993/12/21 14:36:33 bjax
72 * Added calcs of pressures, temps and calibrated airspeeds.
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
78 * Revision 1.6 1993/10/07 18:45:56 bjax
79 * A little cleanup; no significant changes. EBJ
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
85 * Revision 1.4 1993/07/16 18:28:58 bjax
86 * Changed call from atmos_62 to ls_atmos. EBJ
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.
91 * Revision 1.1 92/12/30 13:17:39 bjax
96 ----------------------------------------------------------------------------
98 REFERENCES: [ 1] Shapiro, Ascher H.: "The Dynamics and Thermodynamics
99 of Compressible Fluid Flow", Volume I, The Ronald
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106 ----------------------------------------------------------------------------
110 ----------------------------------------------------------------------------
114 ----------------------------------------------------------------------------
118 --------------------------------------------------------------------------*/
119 #include "ls_types.h"
120 #include "ls_constants.h"
121 #include "ls_generic.h"
125 #include "atmos_62.h"
126 #include "ls_geodesy.h"
127 #include "ls_gravity.h"
132 void ls_aux( void ) {
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;
141 /* update geodetic position */
143 ls_geoc_to_geod( Lat_geocentric, Radius_to_vehicle,
144 &Latitude, &Altitude, &Sea_level_radius );
145 Longitude = Lon_geocentric - Earth_position_angle;
147 /* Calculate body axis velocities */
149 /* Form relative velocity vector */
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;
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;
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;
170 V_rel_wind = sqrt(U_body*U_body + V_body*V_body + W_body*W_body);
173 /* Calculate alpha and beta rates */
175 v_XZ_plane_2 = (U_body*U_body + W_body*W_body);
180 signU = U_body/fabs(U_body);
182 if( (v_XZ_plane_2 == 0) || (V_rel_wind == 0) )
189 Alpha_dot = (U_body*W_dot_body - W_body*U_dot_body)/
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));
196 /* Calculate flight path and other flight condition values */
201 Alpha = atan2( W_body, U_body );
203 Cos_alpha = cos(Alpha);
204 Sin_alpha = sin(Alpha);
209 Beta = asin( V_body/ V_rel_wind );
211 Cos_beta = cos(Beta);
212 Sin_beta = sin(Beta);
214 V_true_kts = V_rel_wind * V_TO_KNOTS;
216 V_ground_speed = sqrt(V_north_rel_ground*V_north_rel_ground
217 + V_east_rel_ground*V_east_rel_ground );
219 V_rel_ground = sqrt(V_ground_speed*V_ground_speed
220 + V_down_rel_ground*V_down_rel_ground );
222 v_tangential = sqrt(V_north*V_north + V_east*V_east);
224 V_inertial = sqrt(v_tangential*v_tangential + V_down*V_down);
226 if( (V_ground_speed == 0) && (V_down == 0) )
229 Gamma_vert_rad = atan2( -V_down, V_ground_speed );
231 if( (V_north_rel_ground == 0) && (V_east_rel_ground == 0) )
234 Gamma_horiz_rad = atan2( V_east_rel_ground, V_north_rel_ground );
236 if (Gamma_horiz_rad < 0)
237 Gamma_horiz_rad = Gamma_horiz_rad + 2*PI;
239 /* Calculate local gravity */
241 ls_gravity( Radius_to_vehicle, Lat_geocentric, &Gravity );
243 /* call function for (smoothed) density ratio, sonic velocity, and
246 ls_atmos(Altitude, &Sigma, &V_sound,
247 &Static_temperature, &Static_pressure);
249 Density = Sigma*SEA_LEVEL_DENSITY;
251 Mach_number = V_rel_wind / V_sound;
253 V_equiv = V_rel_wind*sqrt(Sigma);
255 V_equiv_kts = V_equiv*V_TO_KNOTS;
257 /* calculate temperature and pressure ratios (from [1]) */
259 mach2 = Mach_number*Mach_number;
260 temp_ratio = 1.0 + 0.2*mach2;
261 pres_ratio = pow( temp_ratio, 3.5 );
263 Total_temperature = temp_ratio*Static_temperature;
264 Total_pressure = pres_ratio*Static_pressure;
266 /* calculate impact and dynamic pressures */
268 Impact_pressure = Total_pressure - Static_pressure;
270 Dynamic_pressure = 0.5*Density*V_rel_wind*V_rel_wind;
272 /* calculate calibrated airspeed indication */
274 V_calibrated = sqrt( 2.0*Dynamic_pressure / SEA_LEVEL_DENSITY );
275 V_calibrated_kts = V_calibrated*V_TO_KNOTS;
277 Centrifugal_relief = 1 - v_tangential/(Radius_to_vehicle*Gravity);
279 /* Determine location in runway coordinates */
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);
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;
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;
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;
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;
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;
319 /* Calculate Euler rates */
323 Sin_theta = sin(Theta);
324 Cos_theta = cos(Theta);
331 Psi_dot = (Q_total*Sin_phi + R_total*Cos_phi)/Cos_theta;
333 Theta_dot = Q_total*Cos_phi - R_total*Sin_phi;
334 Phi_dot = P_total + Psi_dot*Sin_theta;
339 /*************************************************************************/