--- /dev/null
+/***************************************************************************
+
+ TITLE: uiuc_aero
+
+----------------------------------------------------------------------------
+
+ FUNCTION: aerodynamics, engine and gear model
+
+----------------------------------------------------------------------------
+
+ MODULE STATUS: developmental
+
+----------------------------------------------------------------------------
+
+ GENEALOGY: Equations based on Part 1 of Roskam's S&C text
+
+----------------------------------------------------------------------------
+
+ DESIGNED BY: Bipin Sehgal
+
+ CODED BY: Bipin Sehgal
+
+ MAINTAINED BY: Bipin Sehgal
+
+----------------------------------------------------------------------------
+
+ MODIFICATION HISTORY:
+
+ DATE PURPOSE BY
+ 3/17/00 Initial test release
+
+
+----------------------------------------------------------------------------
+
+ CALLED BY:
+
+----------------------------------------------------------------------------
+
+ CALLS TO:
+
+----------------------------------------------------------------------------
+
+ INPUTS:
+
+----------------------------------------------------------------------------
+
+ OUTPUTS:
+
+--------------------------------------------------------------------------*/
+
+
+#include <math.h>
+#include "ls_types.h"
+#include "ls_generic.h"
+#include "ls_constants.h"
+#include "ls_cockpit.h"
+#include <FDM/UIUCModel/uiuc_wrapper.h>
+
+
+void aero( SCALAR dt, int Initialize )
+{
+ static int init = 0;
+
+ if (init==0)
+ {
+ init = -1;
+ uiuc_init_aeromodel();
+ }
+
+ uiuc_force_moment(dt);
+}
+
+
+void engine( SCALAR dt, int Initialize )
+{
+ uiuc_engine_routine();
+}
+
+/* ***********************************************************************
+ * Gear model. Exact copy of C172_gear.c. Additional gear models will be
+ * added later and the choice of the gear model could be specified at
+ * runtime.
+ * ***********************************************************************/
+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];
+}
+
+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];
+}
+
+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];
+}
+
+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];
+}
+
+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];
+}
+
+clear3( DATA v[] )
+{
+ v[0] = 0.; v[1] = 0.; v[2] = 0.;
+}
+
+gear()
+{
+char rcsid[] = "$Id$";
+
+ /*
+ * Aircraft specific initializations and data goes here
+ */
+
+#define NUM_WHEELS 3
+
+ static int num_wheels = NUM_WHEELS; /* number of wheels */
+ static DATA d_wheel_rp_body_v[NUM_WHEELS][3] = /* X, Y, Z locations */
+ {
+ { 10., 0., 4. }, /* in feet */
+ { -1., 3., 4. },
+ { -1., -3., 4. }
+ };
+ static DATA spring_constant[NUM_WHEELS] = /* springiness, lbs/ft */
+ { 1500., 5000., 5000. };
+ static DATA spring_damping[NUM_WHEELS] = /* damping, lbs/ft/sec */
+ { 100., 150., 150. };
+ static DATA percent_brake[NUM_WHEELS] = /* percent applied braking */
+ { 0., 0., 0. }; /* 0 = none, 1 = full */
+ static DATA caster_angle_rad[NUM_WHEELS] = /* steerable tires - in */
+ { 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 DATA sliding_mu = 0.5;
+ static DATA rolling_mu = 0.01;
+ static DATA max_brake_mu = 0.6;
+ 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_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 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] = 0.; /* replace with cockpit brake handle connection code */
+ percent_brake[2] = percent_brake[1];
+
+ caster_angle_rad[0] = 0.03*Rudder_pedal;
+
+ for (i=0;i<num_wheels;i++) /* Loop for each wheel */
+ {
+ /*========================================*/
+ /* Calculate wheel position w.r.t. runway */
+ /*========================================*/
+
+ /* First calculate wheel location w.r.t. cg in body (X-Y-Z) axes... */
+
+ sub3( d_wheel_rp_body_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, temp3b );
+
+ /* plus contribution due to cg velocities */
+
+ add3( temp3b, V_local_rel_ground_v, v_wheel_local_v );
+
+
+ /*===========================================*/
+ /* 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.;
+ if( d_wheel_rwy_local_v[2] < 0. )
+ {
+ reaction_normal_force = spring_constant[i]*d_wheel_rwy_local_v[2]
+ - v_wheel_local_v[2]*spring_damping[i];
+ if (reaction_normal_force > 0.) reaction_normal_force = 0.;
+ /* to prevent damping component from swamping spring component */
+ }
+
+ /* Calculate friction coefficients */
+
+ forward_mu = (max_brake_mu - rolling_mu)*percent_brake[i] + rolling_mu;
+ abs_v_wheel_sideward = sqrt(v_wheel_sideward*v_wheel_sideward);
+ sideward_mu = sliding_mu;
+ 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.;
+
+ /* 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;
+
+ /* 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 );
+
+ }
+}
projects / flightgear.git / commitdiff