/*************************************************************************** TITLE: gear ---------------------------------------------------------------------------- FUNCTION: Landing gear model for example simulation ---------------------------------------------------------------------------- MODULE STATUS: developmental ---------------------------------------------------------------------------- GENEALOGY: Renamed navion_gear.c originally created 931012 by E. B. Jackson ---------------------------------------------------------------------------- DESIGNED BY: E. B. Jackson CODED BY: E. B. Jackson MAINTAINED BY: E. B. Jackson ---------------------------------------------------------------------------- MODIFICATION HISTORY: DATE PURPOSE BY 931218 Added navion.h header to allow connection with aileron displacement for nosewheel steering. EBJ 940511 Connected nosewheel to rudder pedal; adjusted gain. CURRENT RCS HEADER: $Header$ $Log$ Revision 1.1 1999/06/17 18:07:34 curt Initial revision Revision 1.1 1999/06/15 20:05:27 curt Added c172 model from Tony Peden. Revision 1.1.1.1 1999/04/05 21:32:45 curt Start of 0.6.x branch. Revision 1.6 1998/10/17 01:34:16 curt C++ ifying ... Revision 1.5 1998/09/29 02:03:00 curt Added a brake + autopilot mods. Revision 1.4 1998/08/06 12:46:40 curt Header change. Revision 1.3 1998/02/03 23:20:18 curt Lots of little tweaks to fix various consistency problems discovered by Solaris' CC. Fixed a bug in fg_debug.c with how the fgPrintf() wrapper passed arguments along to the real printf(). Also incorporated HUD changes by Michele America. Revision 1.2 1998/01/19 18:40:29 curt Tons of little changes to clean up the code and to remove fatal errors when building with the c++ compiler. Revision 1.1 1997/05/29 00:10:02 curt Initial Flight Gear revision. ---------------------------------------------------------------------------- REFERENCES: ---------------------------------------------------------------------------- CALLED BY: ---------------------------------------------------------------------------- CALLS TO: ---------------------------------------------------------------------------- INPUTS: ---------------------------------------------------------------------------- OUTPUTS: --------------------------------------------------------------------------*/ #include #include "ls_types.h" #include "ls_constants.h" #include "ls_generic.h" #include "ls_cockpit.h" 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]; } 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]; } 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]; } 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]; } 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]; } void clear3( DATA v[] ) { v[0] = 0.; v[1] = 0.; v[2] = 0.; } void gear( SCALAR dt, int Initialize ) { 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 */ /* replace with cockpit brake handle connection code */ percent_brake[1] = Brake_pct; percent_brake[2] = percent_brake[1]; caster_angle_rad[0] = 0.03*Rudder_pedal; for (i=0;i 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 ); } }