1997-05-29 00:09:51 +00:00
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/***************************************************************************
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TITLE: ls_Accel
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----------------------------------------------------------------------------
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FUNCTION: Sums forces and moments and calculates accelerations
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----------------------------------------------------------------------------
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MODULE STATUS: developmental
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----------------------------------------------------------------------------
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GENEALOGY: Written 920731 by Bruce Jackson. Based upon equations
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given in reference [1] and a Matrix-X/System Build block
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diagram model of equations of motion coded by David Raney
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at NASA-Langley in June of 1992.
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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:
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----------------------------------------------------------------------------
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MODIFICATION HISTORY:
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DATE PURPOSE
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931007 Moved calculations of auxiliary accelerations here from ls_aux.c BY
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and corrected minus sign in front of A_Y_Pilot
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contribution from Q_body*P_body*D_X_pilot term.
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940111 Changed DATA to SCALAR; updated header files
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$Header$
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$Log$
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1998-01-19 18:40:15 +00:00
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Revision 1.2 1998/01/19 18:40:24 curt
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Tons of little changes to clean up the code and to remove fatal errors
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when building with the c++ compiler.
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1997-05-29 00:09:51 +00:00
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Revision 1.1 1997/05/29 00:09:53 curt
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Initial Flight Gear revision.
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* Revision 1.5 1994/01/11 18:42:16 bjax
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* Oops! Changed data types from DATA to SCALAR for precision control.
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*
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* Revision 1.4 1994/01/11 18:36:58 bjax
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* Removed ls_eom.h include directive; replaced with ls_types, ls_constants,
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* and ls_generic.h includes.
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*
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* Revision 1.3 1993/10/07 18:45:24 bjax
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* Added local defn of d[xyz]_pilot_from_cg to support previous mod. EBJ
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*
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* Revision 1.2 1993/10/07 18:41:31 bjax
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* Moved calculations of auxiliary accelerations here from ls_aux, and
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* corrected sign on Q_body*P_body*d_x_pilot term of A_Y_pilot calc. EBJ
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*
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* Revision 1.1 1992/12/30 13:17:02 bjax
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* Initial revision
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*
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----------------------------------------------------------------------------
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REFERENCES:
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[ 1] McFarland, Richard E.: "A Standard Kinematic Model
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for Flight Simulation at NASA-Ames", NASA CR-2497,
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January 1975
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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: Aero, engine, gear forces & moments
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----------------------------------------------------------------------------
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OUTPUTS: State derivatives
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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_constants.h"
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1998-01-19 18:40:15 +00:00
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#include "ls_accel.h"
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1997-05-29 00:09:51 +00:00
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#include <math.h>
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1998-01-19 18:40:15 +00:00
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void ls_accel( void ) {
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1997-05-29 00:09:51 +00:00
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SCALAR inv_Mass, inv_Radius;
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SCALAR ixz2, c0, c1, c2, c3, c4, c5, c6, c7, c8, c9, c10;
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SCALAR dx_pilot_from_cg, dy_pilot_from_cg, dz_pilot_from_cg;
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/* Sum forces and moments at reference point */
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F_X = F_X_aero + F_X_engine + F_X_gear;
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F_Y = F_Y_aero + F_Y_engine + F_Y_gear;
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F_Z = F_Z_aero + F_Z_engine + F_Z_gear;
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M_l_rp = M_l_aero + M_l_engine + M_l_gear;
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M_m_rp = M_m_aero + M_m_engine + M_m_gear;
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M_n_rp = M_n_aero + M_n_engine + M_n_gear;
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/* Transfer moments to center of gravity */
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M_l_cg = M_l_rp + F_Y*Dz_cg - F_Z*Dy_cg;
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M_m_cg = M_m_rp + F_Z*Dx_cg - F_X*Dz_cg;
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M_n_cg = M_n_rp + F_X*Dy_cg - F_Y*Dx_cg;
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/* Transform from body to local frame */
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F_north = T_local_to_body_11*F_X + T_local_to_body_21*F_Y
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+ T_local_to_body_31*F_Z;
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F_east = T_local_to_body_12*F_X + T_local_to_body_22*F_Y
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+ T_local_to_body_32*F_Z;
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F_down = T_local_to_body_13*F_X + T_local_to_body_23*F_Y
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+ T_local_to_body_33*F_Z;
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/* Calculate linear accelerations */
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inv_Mass = 1/Mass;
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inv_Radius = 1/Radius_to_vehicle;
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V_dot_north = inv_Mass*F_north +
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inv_Radius*(V_north*V_down - V_east*V_east*tan(Lat_geocentric));
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V_dot_east = inv_Mass*F_east +
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inv_Radius*(V_east*V_down + V_north*V_east*tan(Lat_geocentric));
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V_dot_down = inv_Mass*(F_down) + Gravity -
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inv_Radius*(V_north*V_north + V_east*V_east);
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/* Invert the symmetric inertia matrix */
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ixz2 = I_xz*I_xz;
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c0 = 1/(I_xx*I_zz - ixz2);
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c1 = c0*((I_yy-I_zz)*I_zz - ixz2);
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c2 = c0*I_xz*(I_xx - I_yy + I_zz);
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c3 = c0*I_zz;
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c4 = c0*I_xz;
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c7 = 1/I_yy;
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c5 = c7*(I_zz - I_xx);
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c6 = c7*I_xz;
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c8 = c0*((I_xx - I_yy)*I_xx + ixz2);
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c9 = c0*I_xz*(I_yy - I_zz - I_xx);
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c10 = c0*I_xx;
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/* Calculate the rotational body axis accelerations */
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P_dot_body = (c1*R_body + c2*P_body)*Q_body + c3*M_l_cg + c4*M_n_cg;
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Q_dot_body = c5*R_body*P_body + c6*(R_body*R_body - P_body*P_body) + c7*M_m_cg;
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R_dot_body = (c8*P_body + c9*R_body)*Q_body + c4*M_l_cg + c10*M_n_cg;
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/* Calculate body axis accelerations (move to ls_accel?) */
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inv_Mass = 1/Mass;
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A_X_cg = F_X * inv_Mass;
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A_Y_cg = F_Y * inv_Mass;
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A_Z_cg = F_Z * inv_Mass;
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dx_pilot_from_cg = Dx_pilot - Dx_cg;
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dy_pilot_from_cg = Dy_pilot - Dy_cg;
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dz_pilot_from_cg = Dz_pilot - Dz_cg;
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A_X_pilot = A_X_cg + (-R_body*R_body - Q_body*Q_body)*dx_pilot_from_cg
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+ ( P_body*Q_body - R_dot_body )*dy_pilot_from_cg
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+ ( P_body*R_body + Q_dot_body )*dz_pilot_from_cg;
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A_Y_pilot = A_Y_cg + ( P_body*Q_body + R_dot_body )*dx_pilot_from_cg
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+ (-P_body*P_body - R_body*R_body)*dy_pilot_from_cg
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+ ( Q_body*R_body - P_dot_body )*dz_pilot_from_cg;
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A_Z_pilot = A_Z_cg + ( P_body*R_body - Q_dot_body )*dx_pilot_from_cg
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+ ( Q_body*R_body + P_dot_body )*dy_pilot_from_cg
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+ (-Q_body*Q_body - P_body*P_body)*dz_pilot_from_cg;
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N_X_cg = INVG*A_X_cg;
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N_Y_cg = INVG*A_Y_cg;
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N_Z_cg = INVG*A_Z_cg;
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N_X_pilot = INVG*A_X_pilot;
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N_Y_pilot = INVG*A_Y_pilot;
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N_Z_pilot = INVG*A_Z_pilot;
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U_dot_body = T_local_to_body_11*V_dot_north + T_local_to_body_12*V_dot_east
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+ T_local_to_body_13*V_dot_down - Q_total*W_body + R_total*V_body;
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V_dot_body = T_local_to_body_21*V_dot_north + T_local_to_body_22*V_dot_east
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+ T_local_to_body_23*V_dot_down - R_total*U_body + P_total*W_body;
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W_dot_body = T_local_to_body_31*V_dot_north + T_local_to_body_32*V_dot_east
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+ T_local_to_body_33*V_dot_down - P_total*V_body + Q_total*U_body;
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/* End of ls_accel */
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}
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/**************************************************************************/
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