219 lines
6.5 KiB
C
219 lines
6.5 KiB
C
|
/***************************************************************************
|
||
|
|
|
||
|
|
TITLE: Navion_aero
|
||
|
|
|
||
|
|
----------------------------------------------------------------------------
|
||
|
|
|
||
|
|
FUNCTION: Linear aerodynamics model
|
||
|
|
|
||
|
|
----------------------------------------------------------------------------
|
||
|
|
|
||
|
|
MODULE STATUS: developmental
|
||
|
|
|
||
|
|
----------------------------------------------------------------------------
|
||
|
|
|
||
|
|
GENEALOGY: Based upon class notes from AA271, Stanford University,
|
||
|
|
Spring 1988. Dr. Robert Cannon, instructor.
|
||
|
|
|
||
|
|
----------------------------------------------------------------------------
|
||
|
|
|
||
|
|
DESIGNED BY: Bruce Jackson
|
||
|
|
|
||
|
|
CODED BY: Bruce Jackson
|
||
|
|
|
||
|
|
MAINTAINED BY: Bruce Jackson
|
||
|
|
|
||
|
|
----------------------------------------------------------------------------
|
||
|
|
|
||
|
|
MODIFICATION HISTORY:
|
||
|
|
|
||
|
|
DATE PURPOSE BY
|
||
|
|
921229 Changed Alpha, Beta into radians; added Alpha bias.
|
||
|
|
EBJ
|
||
|
|
930105 Modified to support linear airframe simulation by
|
||
|
|
adding shared memory initialization routine. EBJ
|
||
|
|
931013 Added scaling by airspeed, to allow for low-airspeed
|
||
|
|
ground operations. EBJ
|
||
|
|
940216 Scaled long, lat stick and rudder to more appropriate values
|
||
|
|
of elevator and aileron. EBJ
|
||
|
|
|
||
|
|
----------------------------------------------------------------------------
|
||
|
|
|
||
|
|
REFERENCES:
|
||
|
|
|
||
|
|
The Navion "aero" routine is a simple representation of the North
|
||
|
|
American Navion airplane, a 1950-s vintage single-engine, low-wing
|
||
|
|
mono-lane built by NAA (who built the famous P-51 Mustang) supposedly
|
||
|
|
as a plane for returning WW-II fighter jocks to carry the family
|
||
|
|
around the country in. Unfortunately underpowered, it can still be
|
||
|
|
found in small airports across the United States. From behind, it sort
|
||
|
|
of looks like a Volkswagen driving a Piper by virtue of its nicely
|
||
|
|
rounded cabin roof and small rear window.
|
||
|
|
|
||
|
|
The aero routine is only valid around 100 knots; it is referred to as
|
||
|
|
a "linear model" of the navion; the data having been extracted by
|
||
|
|
someone unknown from a more complete model, or more likely, from
|
||
|
|
in-flight measurements and manuever time histories. It probably came
|
||
|
|
from someone at Princeton U; they owned a couple modified Navions that
|
||
|
|
had a variable-stability system installed, and were highly
|
||
|
|
instrumented (and well calibrated, I assume).
|
||
|
|
|
||
|
|
In any event, a linearized model, such as this one, contains various
|
||
|
|
"stability derivatives", or estimates of how aerodynamic forces and
|
||
|
|
moments vary with changes in angle of attack, angular body rates, and
|
||
|
|
control surface deflections. For example, L_beta is an estimate of how
|
||
|
|
much roll moment varies per degree of sideslip increase. A decoding
|
||
|
|
ring is given below:
|
||
|
|
|
||
|
|
X Aerodynamic force, lbs, in X-axis (+ forward)
|
||
|
|
Y Aerodynamic force, lbs, in Y-axis (+ right)
|
||
|
|
Z Aerodynamic force, lbs, in Z-axis (+ down)
|
||
|
|
L Aero. moment about X-axis (+ roll right), ft-lbs
|
||
|
|
M Aero. moment about Y-axis (+ pitch up), ft-lbs
|
||
|
|
N Aero. moment about Z-axis (+ nose right), ft-lbs
|
||
|
|
|
||
|
|
0 Subscript implying initial, or nominal, value
|
||
|
|
u X-axis component of airspeed (ft/sec) (+ forward)
|
||
|
|
v Y-axis component of airspeed (ft/sec) (+ right)
|
||
|
|
w Z-axis component of airspeed (ft/sec) (+ down)
|
||
|
|
p X-axis ang. rate (rad/sec) (+ roll right), rad/sec
|
||
|
|
q Y-axis ang. rate (rad/sec) (+ pitch up), rad/sec
|
||
|
|
r Z-axis ang. rate (rad/sec) (+ yaw right), rad/sec
|
||
|
|
beta Angle of sideslip, degrees (+ wind in RIGHT ear)
|
||
|
|
da Aileron deflection, degrees (+ left ail. TE down)
|
||
|
|
de Elevator deflection, degrees (+ trailing edge down)
|
||
|
|
dr Rudder deflection, degrees (+ trailing edge LEFT)
|
||
|
|
|
||
|
|
----------------------------------------------------------------------------
|
||
|
|
|
||
|
|
CALLED BY:
|
||
|
|
|
||
|
|
----------------------------------------------------------------------------
|
||
|
|
|
||
|
|
CALLS TO:
|
||
|
|
|
||
|
|
----------------------------------------------------------------------------
|
||
|
|
|
||
|
|
INPUTS:
|
||
|
|
|
||
|
|
----------------------------------------------------------------------------
|
||
|
|
|
||
|
|
OUTPUTS:
|
||
|
|
|
||
|
|
--------------------------------------------------------------------------*/
|
||
|
|
|
||
|
|
#include "ls_types.h"
|
||
|
|
#include "ls_generic.h"
|
||
|
|
#include "ls_cockpit.h"
|
||
|
|
|
||
|
|
/* define trimmed w_body to correspond with alpha_trim = 5 */
|
||
|
|
#define TRIMMED_W 15.34
|
||
|
|
|
||
|
|
extern COCKPIT cockpit_;
|
||
|
|
|
||
|
|
|
||
|
|
void aero()
|
||
|
|
{
|
||
|
|
static int init = 0;
|
||
|
|
|
||
|
|
SCALAR u, w;
|
||
|
|
static SCALAR elevator, aileron, rudder;
|
||
|
|
static SCALAR long_scale = 0.3;
|
||
|
|
static SCALAR lat_scale = 0.1;
|
||
|
|
static SCALAR yaw_scale = -0.1;
|
||
|
|
static SCALAR scale = 1.0;
|
||
|
|
|
||
|
|
static SCALAR trim_inc = 0.0002;
|
||
|
|
static SCALAR long_trim;
|
||
|
|
|
||
|
|
static DATA U_0;
|
||
|
|
static DATA X_0;
|
||
|
|
static DATA M_0;
|
||
|
|
static DATA Z_0;
|
||
|
|
static DATA X_u;
|
||
|
|
static DATA X_w;
|
||
|
|
static DATA X_de;
|
||
|
|
static DATA Y_v;
|
||
|
|
static DATA Z_u;
|
||
|
|
static DATA Z_w;
|
||
|
|
static DATA Z_de;
|
||
|
|
static DATA L_beta;
|
||
|
|
static DATA L_p;
|
||
|
|
static DATA L_r;
|
||
|
|
static DATA L_da;
|
||
|
|
static DATA L_dr;
|
||
|
|
static DATA M_w;
|
||
|
|
static DATA M_q;
|
||
|
|
static DATA M_de;
|
||
|
|
static DATA N_beta;
|
||
|
|
static DATA N_p;
|
||
|
|
static DATA N_r;
|
||
|
|
static DATA N_da;
|
||
|
|
static DATA N_dr;
|
||
|
|
|
||
|
|
if (!init)
|
||
|
|
{
|
||
|
|
init = -1;
|
||
|
|
|
||
|
|
/* Initialize aero coefficients */
|
||
|
|
|
||
|
|
U_0 = 176;
|
||
|
|
X_0 = -573.75;
|
||
|
|
M_0 = 0;
|
||
|
|
Z_0 = -2750;
|
||
|
|
X_u = -0.0451; /* original value */
|
||
|
|
/* X_u = 0.0000; */ /* for MUCH better performance - EBJ */
|
||
|
|
X_w = 0.03607;
|
||
|
|
X_de = 0;
|
||
|
|
Y_v = -0.2543;
|
||
|
|
Z_u = -0.3697; /* original value */
|
||
|
|
/* Z_u = -0.03697; */ /* for better performance - EBJ */
|
||
|
|
Z_w = -2.0244;
|
||
|
|
Z_de = -28.17;
|
||
|
|
L_beta = -15.982;
|
||
|
|
L_p = -8.402;
|
||
|
|
L_r = 2.193;
|
||
|
|
L_da = 28.984;
|
||
|
|
L_dr = 2.548;
|
||
|
|
M_w = -0.05;
|
||
|
|
M_q = -2.0767;
|
||
|
|
M_de = -11.1892;
|
||
|
|
N_beta = 4.495;
|
||
|
|
N_p = -0.3498;
|
||
|
|
N_r = -0.7605;
|
||
|
|
N_da = -0.2218;
|
||
|
|
N_dr = -4.597;
|
||
|
|
|
||
|
|
|
||
|
|
/* initialize trim 'actuator' */
|
||
|
|
long_trim = 1.969572E-03;
|
||
|
|
}
|
||
|
|
|
||
|
|
u = V_rel_wind - U_0;
|
||
|
|
w = W_body - TRIMMED_W;
|
||
|
|
|
||
|
|
elevator = long_scale * Long_control;
|
||
|
|
aileron = lat_scale * Lat_control;
|
||
|
|
rudder = yaw_scale * Rudder_pedal;
|
||
|
|
|
||
|
|
if(Aft_trim) long_trim = long_trim - trim_inc;
|
||
|
|
if(Fwd_trim) long_trim = long_trim + trim_inc;
|
||
|
|
|
||
|
|
scale = V_rel_wind*V_rel_wind/(U_0*U_0);
|
||
|
|
if (scale > 1.0) scale = 1.0; /* ebj */
|
||
|
|
|
||
|
|
|
||
|
|
F_X_aero = scale*(X_0 + Mass*(X_u*u + X_w*w + X_de*elevator));
|
||
|
|
F_Y_aero = scale*(Mass*Y_v*V_body);
|
||
|
|
F_Z_aero = scale*(Z_0 + Mass*(Z_u*u + Z_w*w + Z_de*elevator));
|
||
|
|
|
||
|
|
M_l_aero = scale*(I_xx*(L_beta*Beta + L_p*P_body + L_r*R_body
|
||
|
|
+ L_da*aileron + L_dr*rudder));
|
||
|
|
M_m_aero = scale*(M_0 + I_yy*(M_w*w + M_q*Q_body + M_de*(elevator + long_trim)));
|
||
|
|
M_n_aero = scale*(I_zz*(N_beta*Beta + N_p*P_body + N_r*R_body
|
||
|
|
+ N_da*aileron + N_dr*rudder));
|
||
|
|
|
||
|
|
}
|
||
|
|
|
||
|
|
|