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flightgear/LaRCsim/ls_aux.c

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Initial Flight Gear revision.
1997-05-29 00:09:51 +00:00
/***************************************************************************
TITLE: ls_aux
----------------------------------------------------------------------------
FUNCTION: Atmospheric and auxilary relationships for LaRCSim EOM
----------------------------------------------------------------------------
MODULE STATUS: developmental
----------------------------------------------------------------------------
GENEALOGY: Created 9208026 as part of C-castle simulation project.
----------------------------------------------------------------------------
DESIGNED BY: B. Jackson
CODED BY: B. Jackson
MAINTAINED BY: B. Jackson
----------------------------------------------------------------------------
MODIFICATION HISTORY:
DATE PURPOSE
931006 Moved calculations of auxiliary accelerations from here
to ls_accel.c and corrected minus sign in front of A_Y_Pilot
contribution from Q_body*P_body*D_X_pilot term. EBJ
931014 Changed calculation of Alpha from atan to atan2 so sign is correct.
EBJ
931220 Added calculations for static and total temperatures & pressures,
as well as dynamic and impact pressures and calibrated airspeed.
EBJ
940111 Changed #included header files from old "ls_eom.h" to newer
"ls_types.h", "ls_constants.h" and "ls_generic.h". EBJ
950207 Changed use of "abs" to "fabs" in calculation of signU. EBJ
950228 Fixed bug in calculation of beta_dot. EBJ
CURRENT RCS HEADER INFO:
$Header$
$Log$
Revision 1.1 1997/05/29 00:09:54 curt
Initial Flight Gear revision.
* Revision 1.12 1995/02/28 17:57:16 bjax
* Corrected calculation of beta_dot. EBJ
*
* Revision 1.11 1995/02/07 21:09:47 bjax
* Corrected calculation of "signU"; was using divide by
* abs(), which returns an integer; now using fabs(), which
* returns a double. EBJ
*
* Revision 1.10 1994/05/10 20:09:42 bjax
* Fixed a major problem with dx_pilot_from_cg, etc. not being calculated locally.
*
* Revision 1.9 1994/01/11 18:44:33 bjax
* Changed header files to use ls_types, ls_constants, and ls_generic.
*
* Revision 1.8 1993/12/21 14:36:33 bjax
* Added calcs of pressures, temps and calibrated airspeeds.
*
* Revision 1.7 1993/10/14 11:25:38 bjax
* Changed calculation of Alpha to use 'atan2' instead of 'atan' so alphas
* larger than +/- 90 degrees are calculated correctly. EBJ
*
* Revision 1.6 1993/10/07 18:45:56 bjax
* A little cleanup; no significant changes. EBJ
*
* Revision 1.5 1993/10/07 18:42:22 bjax
* Moved calculations of auxiliary accelerations here from ls_aux, and
* corrected sign on Q_body*P_body*d_x_pilot term of A_Y_pilot calc. EBJ
*
* Revision 1.4 1993/07/16 18:28:58 bjax
* Changed call from atmos_62 to ls_atmos. EBJ
*
* Revision 1.3 1993/06/02 15:02:42 bjax
* Changed call to geodesy calcs from ls_geodesy to ls_geoc_to_geod.
*
* Revision 1.1 92/12/30 13:17:39 bjax
* Initial revision
*
----------------------------------------------------------------------------
REFERENCES: [ 1] Shapiro, Ascher H.: "The Dynamics and Thermodynamics
of Compressible Fluid Flow", Volume I, The Ronald
Press, 1953.
----------------------------------------------------------------------------
CALLED BY:
----------------------------------------------------------------------------
CALLS TO:
----------------------------------------------------------------------------
INPUTS:
----------------------------------------------------------------------------
OUTPUTS:
--------------------------------------------------------------------------*/
#include "ls_types.h"
#include "ls_constants.h"
#include "ls_generic.h"
#include <math.h>
void ls_aux()
{
SCALAR dx_pilot_from_cg, dy_pilot_from_cg, dz_pilot_from_cg;
SCALAR inv_Mass;
SCALAR v_XZ_plane_2, signU, v_tangential;
SCALAR inv_radius_ratio;
SCALAR cos_rwy_hdg, sin_rwy_hdg;
SCALAR mach2, temp_ratio, pres_ratio;
/* update geodetic position */
ls_geoc_to_geod( Lat_geocentric, Radius_to_vehicle,
&Latitude, &Altitude, &Sea_level_radius );
Longitude = Lon_geocentric - Earth_position_angle;
/* Calculate body axis velocities */
/* Form relative velocity vector */
V_north_rel_ground = V_north;
V_east_rel_ground = V_east
- OMEGA_EARTH*Sea_level_radius*cos( Lat_geocentric );
V_down_rel_ground = V_down;
V_north_rel_airmass = V_north_rel_ground - V_north_airmass;
V_east_rel_airmass = V_east_rel_ground - V_east_airmass;
V_down_rel_airmass = V_down_rel_ground - V_down_airmass;
U_body = T_local_to_body_11*V_north_rel_airmass
+ T_local_to_body_12*V_east_rel_airmass
+ T_local_to_body_13*V_down_rel_airmass + U_gust;
V_body = T_local_to_body_21*V_north_rel_airmass
+ T_local_to_body_22*V_east_rel_airmass
+ T_local_to_body_23*V_down_rel_airmass + V_gust;
W_body = T_local_to_body_31*V_north_rel_airmass
+ T_local_to_body_32*V_east_rel_airmass
+ T_local_to_body_33*V_down_rel_airmass + W_gust;
V_rel_wind = sqrt(U_body*U_body + V_body*V_body + W_body*W_body);
/* Calculate alpha and beta rates */
v_XZ_plane_2 = (U_body*U_body + W_body*W_body);
if (U_body == 0)
signU = 1;
else
signU = U_body/fabs(U_body);
if( (v_XZ_plane_2 == 0) || (V_rel_wind == 0) )
{
Alpha_dot = 0;
Beta_dot = 0;
}
else
{
Alpha_dot = (U_body*W_dot_body - W_body*U_dot_body)/
v_XZ_plane_2;
Beta_dot = (signU*v_XZ_plane_2*V_dot_body
- V_body*(U_body*U_dot_body + W_body*W_dot_body))
/(V_rel_wind*V_rel_wind*sqrt(v_XZ_plane_2));
}
/* Calculate flight path and other flight condition values */
if (U_body == 0)
Alpha = 0;
else
Alpha = atan2( W_body, U_body );
Cos_alpha = cos(Alpha);
Sin_alpha = sin(Alpha);
if (V_rel_wind == 0)
Beta = 0;
else
Beta = asin( V_body/ V_rel_wind );
Cos_beta = cos(Beta);
Sin_beta = sin(Beta);
V_true_kts = V_rel_wind * V_TO_KNOTS;
V_ground_speed = sqrt(V_north_rel_ground*V_north_rel_ground
+ V_east_rel_ground*V_east_rel_ground );
V_rel_ground = sqrt(V_ground_speed*V_ground_speed
+ V_down_rel_ground*V_down_rel_ground );
v_tangential = sqrt(V_north*V_north + V_east*V_east);
V_inertial = sqrt(v_tangential*v_tangential + V_down*V_down);
if( (V_ground_speed == 0) && (V_down == 0) )
Gamma_vert_rad = 0;
else
Gamma_vert_rad = atan2( -V_down, V_ground_speed );
if( (V_north_rel_ground == 0) && (V_east_rel_ground == 0) )
Gamma_horiz_rad = 0;
else
Gamma_horiz_rad = atan2( V_east_rel_ground, V_north_rel_ground );
if (Gamma_horiz_rad < 0)
Gamma_horiz_rad = Gamma_horiz_rad + 2*PI;
/* Calculate local gravity */
ls_gravity( Radius_to_vehicle, Lat_geocentric, &Gravity );
/* call function for (smoothed) density ratio, sonic velocity, and
ambient pressure */
ls_atmos(Altitude, &Sigma, &V_sound,
&Static_temperature, &Static_pressure);
Density = Sigma*SEA_LEVEL_DENSITY;
Mach_number = V_rel_wind / V_sound;
V_equiv = V_rel_wind*sqrt(Sigma);
V_equiv_kts = V_equiv*V_TO_KNOTS;
/* calculate temperature and pressure ratios (from [1]) */
mach2 = Mach_number*Mach_number;
temp_ratio = 1.0 + 0.2*mach2;
pres_ratio = pow( temp_ratio, 3.5 );
Total_temperature = temp_ratio*Static_temperature;
Total_pressure = pres_ratio*Static_pressure;
/* calculate impact and dynamic pressures */
Impact_pressure = Total_pressure - Static_pressure;
Dynamic_pressure = 0.5*Density*V_rel_wind*V_rel_wind;
/* calculate calibrated airspeed indication */
V_calibrated = sqrt( 2.0*Dynamic_pressure / SEA_LEVEL_DENSITY );
V_calibrated_kts = V_calibrated*V_TO_KNOTS;
Centrifugal_relief = 1 - v_tangential/(Radius_to_vehicle*Gravity);
/* Determine location in runway coordinates */
Radius_to_rwy = Sea_level_radius + Runway_altitude;
cos_rwy_hdg = cos(Runway_heading*DEG_TO_RAD);
sin_rwy_hdg = sin(Runway_heading*DEG_TO_RAD);
D_cg_north_of_rwy = Radius_to_rwy*(Latitude - Runway_latitude);
D_cg_east_of_rwy = Radius_to_rwy*cos(Runway_latitude)
*(Longitude - Runway_longitude);
D_cg_above_rwy = Radius_to_vehicle - Radius_to_rwy;
X_cg_rwy = D_cg_north_of_rwy*cos_rwy_hdg
+ D_cg_east_of_rwy*sin_rwy_hdg;
Y_cg_rwy =-D_cg_north_of_rwy*sin_rwy_hdg
+ D_cg_east_of_rwy*cos_rwy_hdg;
H_cg_rwy = D_cg_above_rwy;
dx_pilot_from_cg = Dx_pilot - Dx_cg;
dy_pilot_from_cg = Dy_pilot - Dy_cg;
dz_pilot_from_cg = Dz_pilot - Dz_cg;
D_pilot_north_of_rwy = D_cg_north_of_rwy
+ T_local_to_body_11*dx_pilot_from_cg
+ T_local_to_body_21*dy_pilot_from_cg
+ T_local_to_body_31*dz_pilot_from_cg;
D_pilot_east_of_rwy = D_cg_east_of_rwy
+ T_local_to_body_12*dx_pilot_from_cg
+ T_local_to_body_22*dy_pilot_from_cg
+ T_local_to_body_32*dz_pilot_from_cg;
D_pilot_above_rwy = D_cg_above_rwy
- T_local_to_body_13*dx_pilot_from_cg
- T_local_to_body_23*dy_pilot_from_cg
- T_local_to_body_33*dz_pilot_from_cg;
X_pilot_rwy = D_pilot_north_of_rwy*cos_rwy_hdg
+ D_pilot_east_of_rwy*sin_rwy_hdg;
Y_pilot_rwy = -D_pilot_north_of_rwy*sin_rwy_hdg
+ D_pilot_east_of_rwy*cos_rwy_hdg;
H_pilot_rwy = D_pilot_above_rwy;
/* Calculate Euler rates */
Sin_phi = sin(Phi);
Cos_phi = cos(Phi);
Sin_theta = sin(Theta);
Cos_theta = cos(Theta);
Sin_psi = sin(Psi);
Cos_psi = cos(Psi);
if( Cos_theta == 0 )
Psi_dot = 0;
else
Psi_dot = (Q_total*Sin_phi + R_total*Cos_phi)/Cos_theta;
Theta_dot = Q_total*Cos_phi - R_total*Sin_phi;
Phi_dot = P_total + Psi_dot*Sin_theta;
/* end of ls_aux */
}
/*************************************************************************/
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