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