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#include <math.h>
#include <stdio.h>
#include <Vlib.h>
#undef printf
/*
* ---------------- z = 0 in body coordinates
* ^
* | r{m,n}.z (constant)
* v
* o gear attachment point
* ^
* | c{m,n}.z strut extension (0 - c{m,n}Max)
* v
* ^
* | G{m,n} strut + tire length (constant)
* v
* ---------------- ground
*
*/
struct balance_data {
double weight; /* weight for this test */
VPoint rm; /* rest main gear ground contact point (input),
rest main gear attachment point (output) */
VPoint rn; /* rest nose gear ground contact point (input),
rest nose gear attachment point (output) */
double cm, cn; /* rest extension values of each strut */
double cmMax, cnMax; /* maximum extension values of each strut */
double Gm, Gn; /* strut + tire lengths */
double Km, Kn; /* string constants (output) */
double Gpz; /* the old "grounding point" Z value */
};
void
balance (s)
struct balance_data *s;
{
double theta, cosTheta, sinTheta;
double Fmz, Fnz;
/*
* Determine the rest pitch angle of the aircraft body
*/
theta = - atan2 (s->rn.z - s->rm.z, s->rn.x - s->rm.x);
cosTheta = cos(theta);
sinTheta = sin(theta);
printf ("Theta = %f degrees (positive down)\n", theta * 180.0 / M_PI);
/*
* Determine correct rm/rn values
*/
s->rn.z = s->rn.z - s->Gn - s->cn;
s->rm.z = s->rm.z - s->Gm - s->cm;
/*
* Determine spring constants
*/
Fmz = (s->weight * s->rn.x) / (s->rn.x - s->rm.x);
Fnz = s->weight - Fmz;
s->Km = Fmz / (s->cmMax - s->cm);
s->Kn = Fnz / (s->cnMax - s->cn);
/*
* Determine the initial grounding point
*/
s->Gpz = s->rm.x * sinTheta + (s->rm.z + s->Gm + s->cm) * cosTheta;
}
main()
{
struct balance_data s;
/*
* Wheel contact locations for the aircraft fully loaded at rest.
*/
VSetPoint (s.rn, 4.1165, 0.0, 2.029);
VSetPoint (s.rm, -0.3489, 4.0118, 2.0299);
/*
* Gross weight
*/
s.weight = 1450 + 300;
/*
* Maximum oleo extension lengths
*/
s.cnMax = 0.5;
s.cmMax = 0.5;
/*
* The length of the wheel and lower landing gear strut
*/
s.Gm = 1.0;
s.Gn = 1.0;
/*
* Rest oleo extension; must be less than cnMax or cmMax; usually about
* half the max value.
*/
s.cm = 0.20;
s.cn = 0.25;
printf ("Input:\n");
printf ("nose contact = %lf %lf %lf\n", s.rn.x, s.rn.y, s.rn.z);
printf ("main's contact = %lf %lf %lf\n", s.rm.x, s.rm.y, s.rm.z);
printf ("Weight = %lf\n", s.weight);
balance(&s);
printf ("\nOutput:\n");
printf ("rm = %lf, %lf, %lf\n", s.rm.x, s.rm.y, s.rm.z);
printf ("rn = %lf, %lf, %lf\n", s.rn.x, s.rn.y, s.rn.z);
printf ("Km = %lf\n", s.Km);
printf ("Kn = %lf\n", s.Kn);
printf ("Grounding point (z) = %lf\n", s.Gpz);
printf ("\n\"inventory\" form:\n\n");
printf ("\tRm\t\t{%lg, %lg, %lg}\n", s.rm.x, s.rm.y, s.rm.z);
printf ("\tRn\t\t{%lg, %lg, %lg}\n", s.rn.x, s.rn.y, s.rn.z);
printf ("\tKm\t\t%lg\n", s.Km);
printf ("\tKn\t\t%lg\n", s.Kn);
printf ("\tGm\t\t%lg\n", s.Gm);
printf ("\tGn\t\t%lg\n", s.Gn);
printf ("\tCmMax\t\t%lg\n", s.cmMax);
printf ("\tCnMax\t\t%lg\n", s.cnMax);
printf ("\tGroundingPoint\t{0.0, 0.0, %lg}\n", s.Gpz);
exit (0);
}
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