--- /dev/null
+/**********************************************************************
+
+ FILENAME: uiuc_gear.cpp
+
+----------------------------------------------------------------------
+
+ DESCRIPTION: determine the gear forces and moments
+
+----------------------------------------------------------------------
+
+ STATUS: alpha version
+
+----------------------------------------------------------------------
+
+ REFERENCES: based on c172_gear by Tony Peden and others
+
+----------------------------------------------------------------------
+
+ HISTORY: 03/09/2001 initial release
+
+----------------------------------------------------------------------
+
+ AUTHOR(S): David Megginson <david@megginson.com
+
+----------------------------------------------------------------------
+
+ VARIABLES: [TODO]
+
+----------------------------------------------------------------------
+
+ INPUTS: [TODO]
+
+----------------------------------------------------------------------
+
+ OUTPUTS: [TODO]
+
+----------------------------------------------------------------------
+
+ CALLED BY: uiuc_wrapper.cpp
+
+----------------------------------------------------------------------
+
+ CALLS TO: none
+
+----------------------------------------------------------------------
+
+ COPYRIGHT: (c) 2001 by David Megginson
+
+ This program is free software; you can redistribute it and/or
+ modify it under the terms of the GNU General Public License
+ as published by the Free Software Foundation.
+
+ This program is distributed in the hope that it will be useful,
+ but WITHOUT ANY WARRANTY; without even the implied warranty of
+ MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
+ GNU General Public License for more details.
+
+ You should have received a copy of the GNU General Public License
+ along with this program; if not, write to the Free Software
+ Foundation, Inc., 59 Temple Place - Suite 330, Boston, MA 02111-1307,
+ USA or view http://www.gnu.org/copyleft/gpl.html.
+
+**********************************************************************/
+
+#include <simgear/compiler.h>
+
+#include "uiuc_gear.h"
+
+SG_USING_STD(cerr);
+
+
+#define HEIGHT_AGL_WHEEL d_wheel_rwy_local_v[2]
+
+
+static void sub3( DATA v1[], DATA v2[], DATA result[] )
+{
+ result[0] = v1[0] - v2[0];
+ result[1] = v1[1] - v2[1];
+ result[2] = v1[2] - v2[2];
+}
+
+static void add3( DATA v1[], DATA v2[], DATA result[] )
+{
+ result[0] = v1[0] + v2[0];
+ result[1] = v1[1] + v2[1];
+ result[2] = v1[2] + v2[2];
+}
+
+static void cross3( DATA v1[], DATA v2[], DATA result[] )
+{
+ result[0] = v1[1]*v2[2] - v1[2]*v2[1];
+ result[1] = v1[2]*v2[0] - v1[0]*v2[2];
+ result[2] = v1[0]*v2[1] - v1[1]*v2[0];
+}
+
+static void multtrans3x3by3( DATA m[][3], DATA v[], DATA result[] )
+{
+ result[0] = m[0][0]*v[0] + m[1][0]*v[1] + m[2][0]*v[2];
+ result[1] = m[0][1]*v[0] + m[1][1]*v[1] + m[2][1]*v[2];
+ result[2] = m[0][2]*v[0] + m[1][2]*v[1] + m[2][2]*v[2];
+}
+
+static void mult3x3by3( DATA m[][3], DATA v[], DATA result[] )
+{
+ result[0] = m[0][0]*v[0] + m[0][1]*v[1] + m[0][2]*v[2];
+ result[1] = m[1][0]*v[0] + m[1][1]*v[1] + m[1][2]*v[2];
+ result[2] = m[2][0]*v[0] + m[2][1]*v[1] + m[2][2]*v[2];
+}
+
+static void clear3( DATA v[] )
+{
+ v[0] = 0.; v[1] = 0.; v[2] = 0.;
+}
+
+void uiuc_gear()
+{
+
+ /*
+ * Aircraft specific initializations and data goes here
+ */
+
+ static DATA percent_brake[MAX_GEAR] = /* percent applied braking */
+ { 0., 0., 0., 0.,
+ 0., 0., 0., 0.,
+ 0., 0., 0., 0.,
+ 0., 0., 0., 0. }; /* 0 = none, 1 = full */
+ static DATA caster_angle_rad[MAX_GEAR] = /* steerable tires - in */
+ { 0., 0., 0., 0.,
+ 0., 0., 0., 0.,
+ 0., 0., 0., 0.,
+ 0., 0., 0., 0. }; /* radians, +CW */
+ /*
+ * End of aircraft specific code
+ */
+
+ /*
+ * Constants & coefficients for tyres on tarmac - ref [1]
+ */
+
+ /* skid function looks like:
+ *
+ * mu ^
+ * |
+ * max_mu | +
+ * | /|
+ * sliding_mu | / +------
+ * | /
+ * | /
+ * +--+------------------------>
+ * | | | sideward V
+ * 0 bkout skid
+ * V V
+ */
+
+
+ static int it_rolls[MAX_GEAR] =
+ { 1, 1, 1, 0,
+ 0, 0, 0, 0,
+ 0, 0, 0, 0,
+ 0, 0, 0, 0 };
+ static DATA sliding_mu[MAX_GEAR] =
+ { 0.5, 0.5, 0.5, 0.3,
+ 0.3, 0.3, 0.3, 0.3,
+ 0.3, 0.3, 0.3, 0.3,
+ 0.3, 0.3, 0.3, 0.3 };
+ static DATA max_brake_mu[MAX_GEAR] =
+ { 0.0, 0.6, 0.6, 0.0,
+ 0.0, 0.0, 0.0, 0.0,
+ 0.0, 0.0, 0.0, 0.0,
+ 0.0, 0.0, 0.0, 0.0 };
+ static DATA max_mu = 0.8;
+ static DATA bkout_v = 0.1;
+ static DATA skid_v = 1.0;
+ /*
+ * Local data variables
+ */
+
+ DATA d_wheel_cg_body_v[3]; /* wheel offset from cg, X-Y-Z */
+ DATA d_wheel_cg_local_v[3]; /* wheel offset from cg, N-E-D */
+ DATA d_wheel_rwy_local_v[3]; /* wheel offset from rwy, N-E-U */
+ DATA v_wheel_cg_local_v[3]; /*wheel velocity rel to cg N-E-D*/
+ DATA v_wheel_body_v[3]; /* wheel velocity, X-Y-Z */
+ DATA v_wheel_local_v[3]; /* wheel velocity, N-E-D */
+ DATA f_wheel_local_v[3]; /* wheel reaction force, N-E-D */
+ DATA altitude_local_v[3]; /*altitude vector in local (N-E-D) i.e. (0,0,h)*/
+ DATA altitude_body_v[3]; /*altitude vector in body (X,Y,Z)*/
+ DATA temp3a[3], temp3b[3], tempF[3], tempM[3];
+ DATA reaction_normal_force; /* wheel normal (to rwy) force */
+ DATA cos_wheel_hdg_angle, sin_wheel_hdg_angle; /* temp storage */
+ DATA v_wheel_forward, v_wheel_sideward, abs_v_wheel_sideward;
+ DATA forward_mu, sideward_mu; /* friction coefficients */
+ DATA beta_mu; /* breakout friction slope */
+ DATA forward_wheel_force, sideward_wheel_force;
+
+ int i; /* per wheel loop counter */
+
+ /*
+ * Execution starts here
+ */
+
+ beta_mu = max_mu/(skid_v-bkout_v);
+ clear3( F_gear_v ); /* Initialize sum of forces... */
+ clear3( M_gear_v ); /* ...and moments */
+
+ /*
+ * Put aircraft specific executable code here
+ */
+
+ percent_brake[1] = Brake_pct[0];
+ percent_brake[2] = Brake_pct[1];
+
+ caster_angle_rad[0] =
+ (0.01 + 0.04 * (1 - V_calibrated_kts / 130)) * Rudder_pedal;
+
+
+ for (i=0;i<MAX_GEAR;i++) /* Loop for each wheel */
+ {
+ // Execute only if the gear has been defined
+ if (!gear_model[i])
+ continue;
+
+ /* printf("%s:\n",gear_strings[i]); */
+
+
+
+ /*========================================*/
+ /* Calculate wheel position w.r.t. runway */
+ /*========================================*/
+
+
+ /* printf("\thgcg: %g, theta: %g,phi: %g\n",D_cg_above_rwy,Theta*RAD_TO_DEG,Phi*RAD_TO_DEG); */
+
+
+ /* First calculate wheel location w.r.t. cg in body (X-Y-Z) axes... */
+
+ sub3( D_gear_v[i], D_cg_rp_body_v, d_wheel_cg_body_v );
+
+ /* then converting to local (North-East-Down) axes... */
+
+ multtrans3x3by3( T_local_to_body_m, d_wheel_cg_body_v, d_wheel_cg_local_v );
+
+
+ /* Runway axes correction - third element is Altitude, not (-)Z... */
+
+ d_wheel_cg_local_v[2] = -d_wheel_cg_local_v[2]; /* since altitude = -Z */
+
+ /* Add wheel offset to cg location in local axes */
+
+ add3( d_wheel_cg_local_v, D_cg_rwy_local_v, d_wheel_rwy_local_v );
+
+ /* remove Runway axes correction so right hand rule applies */
+
+ d_wheel_cg_local_v[2] = -d_wheel_cg_local_v[2]; /* now Z positive down */
+
+ /*============================*/
+ /* Calculate wheel velocities */
+ /*============================*/
+
+ /* contribution due to angular rates */
+
+ cross3( Omega_body_v, d_wheel_cg_body_v, temp3a );
+
+ /* transform into local axes */
+
+ multtrans3x3by3( T_local_to_body_m, temp3a,v_wheel_cg_local_v );
+
+ /* plus contribution due to cg velocities */
+
+ add3( v_wheel_cg_local_v, V_local_rel_ground_v, v_wheel_local_v );
+
+ clear3(f_wheel_local_v);
+ reaction_normal_force=0;
+ if( HEIGHT_AGL_WHEEL < 0. )
+ /*the wheel is underground -- which implies ground contact
+ so calculate reaction forces */
+ {
+ /*===========================================*/
+ /* Calculate forces & moments for this wheel */
+ /*===========================================*/
+
+ /* Add any anticipation, or frame lead/prediction, here... */
+
+ /* no lead used at present */
+
+ /* Calculate sideward and forward velocities of the wheel
+ in the runway plane */
+
+ cos_wheel_hdg_angle = cos(caster_angle_rad[i] + Psi);
+ sin_wheel_hdg_angle = sin(caster_angle_rad[i] + Psi);
+
+ v_wheel_forward = v_wheel_local_v[0]*cos_wheel_hdg_angle
+ + v_wheel_local_v[1]*sin_wheel_hdg_angle;
+ v_wheel_sideward = v_wheel_local_v[1]*cos_wheel_hdg_angle
+ - v_wheel_local_v[0]*sin_wheel_hdg_angle;
+
+
+ /* Calculate normal load force (simple spring constant) */
+
+ reaction_normal_force = 0.;
+
+ reaction_normal_force = kgear[i]*d_wheel_rwy_local_v[2]
+ - v_wheel_local_v[2]*cgear[i];
+ /* printf("\treaction_normal_force: %g\n",reaction_normal_force); */
+
+ if (reaction_normal_force > 0.) reaction_normal_force = 0.;
+ /* to prevent damping component from swamping spring component */
+
+
+ /* Calculate friction coefficients */
+
+ if(it_rolls[i])
+ {
+ forward_mu = (max_brake_mu[i] - muGear[i])*percent_brake[i] + muGear[i];
+ abs_v_wheel_sideward = sqrt(v_wheel_sideward*v_wheel_sideward);
+ sideward_mu = sliding_mu[i];
+ if (abs_v_wheel_sideward < skid_v)
+ sideward_mu = (abs_v_wheel_sideward - bkout_v)*beta_mu;
+ if (abs_v_wheel_sideward < bkout_v) sideward_mu = 0.;
+ }
+ else
+ {
+ forward_mu=sliding_mu[i];
+ sideward_mu=sliding_mu[i];
+ }
+
+ /* Calculate foreward and sideward reaction forces */
+
+ forward_wheel_force = forward_mu*reaction_normal_force;
+ sideward_wheel_force = sideward_mu*reaction_normal_force;
+ if(v_wheel_forward < 0.) forward_wheel_force = -forward_wheel_force;
+ if(v_wheel_sideward < 0.) sideward_wheel_force = -sideward_wheel_force;
+/* printf("\tFfwdgear: %g Fsidegear: %g\n",forward_wheel_force,sideward_wheel_force);
+ */
+ /* Rotate into local (N-E-D) axes */
+
+ f_wheel_local_v[0] = forward_wheel_force*cos_wheel_hdg_angle
+ - sideward_wheel_force*sin_wheel_hdg_angle;
+ f_wheel_local_v[1] = forward_wheel_force*sin_wheel_hdg_angle
+ + sideward_wheel_force*cos_wheel_hdg_angle;
+ f_wheel_local_v[2] = reaction_normal_force;
+
+ /* Convert reaction force from local (N-E-D) axes to body (X-Y-Z) */
+ mult3x3by3( T_local_to_body_m, f_wheel_local_v, tempF );
+
+ /* Calculate moments from force and offsets in body axes */
+
+ cross3( d_wheel_cg_body_v, tempF, tempM );
+
+ /* Sum forces and moments across all wheels */
+
+ add3( tempF, F_gear_v, F_gear_v );
+ add3( tempM, M_gear_v, M_gear_v );
+
+
+ }
+
+
+
+ /* printf("\tN: %g,dZrwy: %g dZdotrwy: %g\n",reaction_normal_force,HEIGHT_AGL_WHEEL,v_wheel_cg_local_v[2]); */
+
+ /*printf("\tFxgear: %g Fygear: %g, Fzgear: %g\n",F_X_gear,F_Y_gear,F_Z_gear);
+ printf("\tMgear: %g, Lgear: %g, Ngear: %g\n\n",M_m_gear,M_l_gear,M_n_gear); */
+
+
+ }
+}
+
+// end uiuc_engine.cpp
--- /dev/null
+/**********************************************************************
+
+ FILENAME: uiuc_map_gear.cpp
+
+----------------------------------------------------------------------
+
+ DESCRIPTION: initializes the gear map
+
+----------------------------------------------------------------------
+
+ STATUS: alpha version
+
+----------------------------------------------------------------------
+
+ REFERENCES:
+
+----------------------------------------------------------------------
+
+ HISTORY: 04/08/2000 initial release
+
+----------------------------------------------------------------------
+
+ AUTHOR(S): Bipin Sehgal <bsehgal@uiuc.edu>
+ Jeff Scott <jscott@mail.com>
+
+----------------------------------------------------------------------
+
+ VARIABLES:
+
+----------------------------------------------------------------------
+
+ INPUTS: none
+
+----------------------------------------------------------------------
+
+ OUTPUTS: none
+
+----------------------------------------------------------------------
+
+ CALLED BY: uiuc_initializemaps.cpp
+
+----------------------------------------------------------------------
+
+ CALLS TO: none
+
+----------------------------------------------------------------------
+
+ COPYRIGHT: (C) 2000 by Michael Selig
+
+ This program is free software; you can redistribute it and/or
+ modify it under the terms of the GNU General Public License
+ as published by the Free Software Foundation.
+
+ This program is distributed in the hope that it will be useful,
+ but WITHOUT ANY WARRANTY; without even the implied warranty of
+ MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
+ GNU General Public License for more details.
+
+ You should have received a copy of the GNU General Public License
+ along with this program; if not, write to the Free Software
+ Foundation, Inc., 59 Temple Place - Suite 330, Boston, MA 02111-1307,
+ USA or view http://www.gnu.org/copyleft/gpl.html.
+
+**********************************************************************/
+
+#include "uiuc_map_gear.h"
+
+
+void uiuc_map_gear()
+{
+ gear_map["Dx_gear"] = Dx_gear_flag ;
+ gear_map["Dy_gear"] = Dy_gear_flag ;
+ gear_map["Dz_gear"] = Dz_gear_flag ;
+ gear_map["cgear"] = cgear_flag ;
+ gear_map["kgear"] = kgear_flag ;
+ gear_map["muGear"] = muGear_flag ;
+ gear_map["strutLength"] = strutLength_flag ;
+}
+
+// end uiuc_map_gear.cpp
projects / flightgear.git / commitdiff