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