flightgear/src/FDM/YASim/FGFDM.cpp

#include <stdio.h>
#include <stdlib.h>

#include <Main/fg_props.hxx>

#include "Jet.hpp"
#include "Gear.hpp"
#include "Atmosphere.hpp"
#include "PropEngine.hpp"
#include "Propeller.hpp"
#include "PistonEngine.hpp"

#include "FGFDM.hpp"
namespace yasim {

// Some conversion factors
static const float KTS2MPS = 0.514444444444;
static const float FT2M = 0.3048;
static const float DEG2RAD = 0.0174532925199;
static const float RPM2RAD = 0.10471975512;
static const float LBS2N = 4.44822;
static const float LBS2KG = 0.45359237;
static const float CM2GALS = 264.172037284;
static const float HP2W = 745.700;
static const float INHG2PA = 3386.389;

// Stubs, so that this can be compiled without the FlightGear
// binary.  What's the best way to handle this?

//     float fgGetFloat(char* name, float def) { return 0; }
//     void fgSetFloat(char* name, float val) {}

FGFDM::FGFDM()
{
    _nextEngine = 0;
}

FGFDM::~FGFDM()
{
    for(int i=0; i<_axes.size(); i++) {
	AxisRec* a = (AxisRec*)_axes.get(i);
	delete[] a->name;
	delete a;
    }
    for(int i=0; i<_pistons.size(); i++) {
	EngRec* er = (EngRec*)_pistons.get(i);
	delete[] er->prefix;
	delete (PropEngine*)er->eng;
	delete er;
    }
    for(int i=0; i<_jets.size(); i++) {
	EngRec* er = (EngRec*)_pistons.get(i);
	delete[] er->prefix;
	delete (Jet*)er->eng;
	delete er;
    }
    for(int i=0; i<_weights.size(); i++) {
	WeightRec* wr = (WeightRec*)_weights.get(i);
	delete[] wr->prop;
	delete wr;
    }
    
}

void FGFDM::iterate(float dt)
{
    getExternalInput(dt);
    _airplane.iterate(dt);
    setOutputProperties();
}

Airplane* FGFDM::getAirplane()
{
    return &_airplane;
}

void FGFDM::init()
{
    // We don't want to use these ties (we set the values ourselves,
    // and this works only for the first piston engine anyway).
    fgUntie("/engines/engine[0]/rpm");
    fgUntie("/engines/engine[0]/egt-degf");
    fgUntie("/engines/engine[0]/cht-degf");
    fgUntie("/engines/engine[0]/oil-temperature-degf");
    fgUntie("/engines/engine[0]/mp-osi");
    fgUntie("/engines/engine[0]/fuel-flow-gph");
    fgUntie("/engines/engine[0]/running");
    fgUntie("/engines/engine[0]/cranking");
    fgUntie("/consumables/fuel/tank[0]/level-gal_us");
    fgUntie("/consumables/fuel/tank[1]/level-gal_us");

    // Set these to sane values.  We don't support engine start yet.
    fgSetBool("/engines/engine[0]/running", true);
    fgSetBool("/engines/engine[0]/cranking", false);

    // Allows the user to start with something other than full fuel
    _airplane.setFuelFraction(fgGetFloat("/yasim/fuel-fraction", 1));

    // This has a nasty habit of being false at startup.  That's not
    // good.
    fgSetBool("/controls/gear-down", true);
}

// Not the worlds safest parser.  But it's short & sweet.
void FGFDM::startElement(const char* name, const XMLAttributes &atts)
{
    XMLAttributes* a = (XMLAttributes*)&atts;
    float v[3];
    char buf[64];

    if(eq(name, "airplane")) {
	_airplane.setWeight(attrf(a, "mass") * LBS2KG);
    } else if(eq(name, "approach")) {
	float spd = attrf(a, "speed") * KTS2MPS;
	float alt = attrf(a, "alt", 0) * FT2M;
	float aoa = attrf(a, "aoa", 0) * DEG2RAD;
	_airplane.setApproach(spd, alt, aoa);
	_cruiseCurr = false;
    } else if(eq(name, "cruise")) {
	float spd = attrf(a, "speed") * KTS2MPS;
	float alt = attrf(a, "alt") * FT2M;
	_airplane.setCruise(spd, alt);
	_cruiseCurr = true;
    } else if(eq(name, "cockpit")) {
	v[0] = attrf(a, "x");
	v[1] = attrf(a, "y");
	v[2] = attrf(a, "z");
	_airplane.setPilotPos(v);
    } else if(eq(name, "wing")) {
	_airplane.setWing(parseWing(a, name));
    } else if(eq(name, "hstab")) {
	_airplane.setTail(parseWing(a, name));
    } else if(eq(name, "vstab")) {
	_airplane.addVStab(parseWing(a, name));
    } else if(eq(name, "propeller")) {
	parsePropeller(a);
    } else if(eq(name, "jet")) {
	Jet* j = new Jet();
	_currObj = j;
	v[0] = attrf(a, "x");
	v[1] = attrf(a, "y");
	v[2] = attrf(a, "z");
	float mass = attrf(a, "mass") * LBS2KG;
	j->setDryThrust(attrf(a, "thrust") * LBS2N);
	j->setReheatThrust(attrf(a, "afterburner", 0) * LBS2N);
	j->setPosition(v);
	_airplane.addThruster(j, mass, v);
	sprintf(buf, "/engines/engine[%d]", _nextEngine++);
	EngRec* er = new EngRec();
	er->eng = j;
	er->prefix = dup(buf);
	_jets.add(er);
    } else if(eq(name, "gear")) {
	Gear* g = new Gear();
	_currObj = g;
	v[0] = attrf(a, "x");
	v[1] = attrf(a, "y");
	v[2] = attrf(a, "z");
	g->setPosition(v);
	v[0] = 0;
	v[1] = 0;
	v[2] = attrf(a, "compression", 1);
	g->setCompression(v);
	g->setStaticFriction(attrf(a, "sfric", 0.8));
	g->setDynamicFriction(attrf(a, "dfric", 0.7));
        float transitionTime = attrf(a, "retract-time", 0);
	_airplane.addGear(g, transitionTime);
    } else if(eq(name, "fuselage")) {
	float b[3];
	v[0] = attrf(a, "ax");
	v[1] = attrf(a, "ay");
	v[2] = attrf(a, "az");
	b[0] = attrf(a, "bx");
	b[1] = attrf(a, "by");
	b[2] = attrf(a, "bz");
	_airplane.addFuselage(v, b, attrf(a, "width"));
    } else if(eq(name, "tank")) {
	v[0] = attrf(a, "x");
	v[1] = attrf(a, "y");
	v[2] = attrf(a, "z");
	float density = 6.0; // gasoline, in lbs/gal
	if(a->hasAttribute("jet")) density = 6.72; 
	density *= LBS2KG/CM2GALS;
	_airplane.addTank(v, attrf(a, "capacity") * LBS2KG, density);
    } else if(eq(name, "ballast")) {
	v[0] = attrf(a, "x");
	v[1] = attrf(a, "y");
	v[2] = attrf(a, "z");
	_airplane.addBallast(v, attrf(a, "mass") * LBS2KG);
    } else if(eq(name, "weight")) {
	parseWeight(a);
    } else if(eq(name, "stall")) {
	Wing* w = (Wing*)_currObj;
	w->setStall(attrf(a, "aoa") * DEG2RAD);
	w->setStallWidth(attrf(a, "width", 2) * DEG2RAD);
	w->setStallPeak(attrf(a, "peak", 1.5));
    } else if(eq(name, "flap0")) {
	((Wing*)_currObj)->setFlap0(attrf(a, "start"), attrf(a, "end"),
				    attrf(a, "lift"), attrf(a, "drag"));
    } else if(eq(name, "flap1")) {
	((Wing*)_currObj)->setFlap1(attrf(a, "start"), attrf(a, "end"),
				    attrf(a, "lift"), attrf(a, "drag"));
    } else if(eq(name, "slat")) {
	((Wing*)_currObj)->setSlat(attrf(a, "start"), attrf(a, "end"),
				   attrf(a, "aoa"), attrf(a, "drag"));
    } else if(eq(name, "spoiler")) {
	((Wing*)_currObj)->setSpoiler(attrf(a, "start"), attrf(a, "end"),
				      attrf(a, "lift"), attrf(a, "drag"));
    } else if(eq(name, "actionpt")) {
 	v[0] = attrf(a, "x");
	v[1] = attrf(a, "y");
	v[2] = attrf(a, "z");
	((Thruster*)_currObj)->setPosition(v);
    } else if(eq(name, "dir")) {
 	v[0] = attrf(a, "x");
	v[1] = attrf(a, "y");
	v[2] = attrf(a, "z");
	((Thruster*)_currObj)->setDirection(v);
    } else if(eq(name, "control")) {
	const char* axis = a->getValue("axis");
	if(a->hasAttribute("output")) {
	    // assert: output type must match _currObj type!
	    const char* output = a->getValue("output");
	    int opt = 0;
	    opt |= a->hasAttribute("split") ? ControlMap::OPT_SPLIT : 0;
	    opt |= a->hasAttribute("invert") ? ControlMap::OPT_INVERT : 0;
	    opt |= a->hasAttribute("square") ? ControlMap::OPT_SQUARE : 0;
	    _airplane.getControlMap()->addMapping(parseAxis(axis),
						  parseOutput(output),
						  _currObj,
						  opt);
	} else {
	    // assert: must be under a "cruise" or "approach" tag
	    float value = attrf(a, "value", 0);
	    if(_cruiseCurr)
		_airplane.addCruiseControl(parseAxis(axis), value);
	    else
		_airplane.addApproachControl(parseAxis(axis), value);
	}
    } else {
	*(int*)0=0; // unexpected tag, boom
    }
}

void FGFDM::getExternalInput(float dt)
{
    // The control axes
    ControlMap* cm = _airplane.getControlMap();
    cm->reset();
    for(int i=0; i<_axes.size(); i++) {
	AxisRec* a = (AxisRec*)_axes.get(i);
	float val = fgGetFloat(a->name, 0);
	cm->setInput(a->handle, val);
    }
    cm->applyControls();

    // Weights
    for(int i=0; i<_weights.size(); i++) {
	WeightRec* wr = (WeightRec*)_weights.get(i);
	_airplane.setWeight(wr->handle, fgGetFloat(wr->prop));
    }

    // Gear state
    _airplane.setGearState(fgGetBool("/controls/gear-down"), dt);
}

void FGFDM::setOutputProperties()
{
    char buf[256];
    for(int i=0; i<_airplane.numTanks(); i++) {
	sprintf(buf, "/consumables/fuel/tank[%d]/level-gal_us", i);
	fgSetFloat(buf,
		   CM2GALS*_airplane.getFuel(i)/_airplane.getFuelDensity(i));
    }

    for(int i=0; i<_pistons.size(); i++) {
	EngRec* er = (EngRec*)_pistons.get(i);
	PropEngine* p = (PropEngine*)er->eng;

	sprintf(buf, "%s/rpm", er->prefix);
	fgSetFloat(buf, p->getOmega() * (30/3.15149265358979));

	sprintf(buf, "%s/fuel-flow-gph", er->prefix);
	fgSetFloat(buf, p->getFuelFlow() * (3600*2.2/5)); // FIXME, wrong
    }

    for(int i=0; i<_jets.size(); i++) {
	EngRec* er = (EngRec*)_jets.get(i);
	Jet* j = (Jet*)er->eng;
	
	sprintf(buf, "%s/fuel-flow-gph", er->prefix);
	fgSetFloat(buf, j->getFuelFlow() * (3600*2.2/6)); // FIXME, wrong
    }
}

Wing* FGFDM::parseWing(XMLAttributes* a, const char* type)
{
    Wing* w = new Wing();

    float defDihed = 0;
    if(eq(type, "vstab"))
	defDihed = 90;
    else
	w->setMirror(true);

    float pos[3];
    pos[0] = attrf(a, "x");
    pos[1] = attrf(a, "y");
    pos[2] = attrf(a, "z");
    w->setBase(pos);

    w->setLength(attrf(a, "length"));
    w->setChord(attrf(a, "chord"));
    w->setSweep(attrf(a, "sweep", 0) * DEG2RAD);
    w->setTaper(attrf(a, "taper", 1));
    w->setDihedral(attrf(a, "dihedral", defDihed) * DEG2RAD);
    w->setCamber(attrf(a, "camber", 0));
    w->setIncidence(attrf(a, "incidence", 0) * DEG2RAD);

    float effect = attrf(a, "effectiveness", 1);
    w->setDragScale(w->getDragScale()*effect);

    _currObj = w;
    return w;
}

void FGFDM::parsePropeller(XMLAttributes* a)
{
    float cg[3];
    cg[0] = attrf(a, "x");
    cg[1] = attrf(a, "y");
    cg[2] = attrf(a, "z");
    float mass = attrf(a, "mass") * LBS2KG;
    float moment = attrf(a, "moment");
    float radius = attrf(a, "radius");
    float speed = attrf(a, "cruise-speed") * KTS2MPS;
    float omega = attrf(a, "cruise-rpm") * RPM2RAD;
    float power = attrf(a, "cruise-power") * HP2W;
    float rho = Atmosphere::getStdDensity(attrf(a, "cruise-alt") * FT2M);

    // Hack, fix this pronto:
    float engP = attrf(a, "eng-power") * HP2W;
    float engS = attrf(a, "eng-rpm") * RPM2RAD;

    Propeller* prop = new Propeller(radius, speed, omega, rho, power);
    PistonEngine* eng = new PistonEngine(engP, engS);
    PropEngine* thruster = new PropEngine(prop, eng, moment);
    _airplane.addThruster(thruster, mass, cg);

    if(a->hasAttribute("turbo-mul")) {
        float mul = attrf(a, "turbo-mul");
        float mp = attrf(a, "wastegate-mp", 1e6) * INHG2PA;
        eng->setTurboParams(mul, mp);
    }

    if(a->hasAttribute("takeoff-power")) {
	float power0 = attrf(a, "takeoff-power") * HP2W;
	float omega0 = attrf(a, "takeoff-rpm") * RPM2RAD;
	prop->setTakeoff(omega0, power0);
    }

    if(a->hasAttribute("max-rpm")) {
	float max = attrf(a, "max-rpm") * RPM2RAD;
	float min = attrf(a, "min-rpm") * RPM2RAD;
	thruster->setVariableProp(min, max);
    }

    char buf[64];
    sprintf(buf, "/engines/engine[%d]", _nextEngine++);
    EngRec* er = new EngRec();
    er->eng = thruster;
    er->prefix = dup(buf);
    _pistons.add(er);

    _currObj = thruster;
}

// Turns a string axis name into an integer for use by the
// ControlMap.  Creates a new axis if this one hasn't been defined
// yet.
int FGFDM::parseAxis(const char* name)
{
    for(int i=0; i<_axes.size(); i++) {
	AxisRec* a = (AxisRec*)_axes.get(i);
	if(eq(a->name, name))
	    return a->handle;
    }

    // Not there, make a new one.
    AxisRec* a = new AxisRec();
    a->name = dup(name);
    a->handle = _airplane.getControlMap()->newInput();
    _axes.add(a);
    return a->handle;
}

int FGFDM::parseOutput(const char* name)
{
    if(eq(name, "THROTTLE"))  return ControlMap::THROTTLE;
    if(eq(name, "MIXTURE"))   return ControlMap::MIXTURE;
    if(eq(name, "ADVANCE"))   return ControlMap::ADVANCE;
    if(eq(name, "REHEAT"))    return ControlMap::REHEAT;
    if(eq(name, "PROP"))      return ControlMap::PROP;
    if(eq(name, "BRAKE"))     return ControlMap::BRAKE;
    if(eq(name, "STEER"))     return ControlMap::STEER;
    if(eq(name, "EXTEND"))    return ControlMap::EXTEND;
    if(eq(name, "INCIDENCE")) return ControlMap::INCIDENCE;
    if(eq(name, "FLAP0"))     return ControlMap::FLAP0;
    if(eq(name, "FLAP1"))     return ControlMap::FLAP1;
    if(eq(name, "SLAT"))      return ControlMap::SLAT;
    if(eq(name, "SPOILER"))   return ControlMap::SPOILER;
    // error here...
    return -1;
}

void FGFDM::parseWeight(XMLAttributes* a)
{
    WeightRec* wr = new WeightRec();

    float v[3];
    v[0] = attrf(a, "x");
    v[1] = attrf(a, "y");
    v[2] = attrf(a, "z");

    wr->prop = dup(a->getValue("mass-prop"));
    wr->size = attrf(a, "size", 0);
    wr->handle = _airplane.addWeight(v, wr->size);

    _weights.add(wr);
}

bool FGFDM::eq(const char* a, const char* b)
{
    // Figure it out for yourself. :)
    while(*a && *b && *a++ == *b++);
    return !(*a || *b);
}

char* FGFDM::dup(const char* s)
{
    int len=0;
    while(s[len++]);
    char* s2 = new char[len+1];
    char* p = s2;
    while((*p++ = *s++));
    s2[len] = 0;
    return s2;
}

int FGFDM::attri(XMLAttributes* atts, char* attr)
{
    if(!atts->hasAttribute(attr)) *(int*)0=0; // boom
    return attri(atts, attr, 0);
}

int FGFDM::attri(XMLAttributes* atts, char* attr, int def)
{
    const char* val = atts->getValue(attr);
    if(val == 0) return def;
    else         return atol(val);
}

float FGFDM::attrf(XMLAttributes* atts, char* attr)
{
    if(!atts->hasAttribute(attr)) *(int*)0=0; // boom
    return attrf(atts, attr, 0);
}

float FGFDM::attrf(XMLAttributes* atts, char* attr, float def)
{
    const char* val = atts->getValue(attr);
    if(val == 0) return def;
    else         return (float)atof(val);    
}

}; // namespace yasim