#include "Math.hpp"
#include "Propeller.hpp"
-#include "PistonEngine.hpp"
+#include "Engine.hpp"
#include "PropEngine.hpp"
namespace yasim {
-PropEngine::PropEngine(Propeller* prop, PistonEngine* eng, float moment)
+PropEngine::PropEngine(Propeller* prop, Engine* eng, float moment)
{
// Start off at 500rpm, because the start code doesn't exist yet
_omega = 52.3f;
_dir[0] = 1; _dir[1] = 0; _dir[2] = 0;
_variable = false;
+ _gearRatio = 1;
_prop = prop;
_eng = eng;
_moment = moment;
_fuel = true;
+ _contra = false;
}
PropEngine::~PropEngine()
_prop->setPropPitch(proppitch);
}
+void PropEngine::setPropFeather(int state)
+{
+ // toggle prop feathering on/off
+ _prop->setPropFeather(state);
+}
+
void PropEngine::setVariableProp(float min, float max)
{
_variable = true;
return _omega;
}
+void PropEngine::setOmega (float omega)
+{
+ _omega = omega;
+}
+
void PropEngine::getThrust(float* out)
{
int i;
_eng->setThrottle(_throttle);
_eng->setMixture(_mixture);
+ _eng->setStarter(false);
_eng->setMagnetos(3);
+
+ bool running_state = _eng->isRunning();
_eng->setRunning(true);
if(_variable) {
bool goingUp = false;
float step = 10;
- while(true) {
- float ptau, dummy;
- _prop->calc(_rho, speed, _omega, &dummy, &ptau);
+
+ // If we cannot manage this in 100 iterations, give up.
+ for (int n = 0; n < 100; n++) {
+ float ptau, thrust;
+ _prop->calc(_rho, speed, _omega * _gearRatio, &thrust, &ptau);
_eng->calc(_pressure, _temp, _omega);
+ _eng->stabilize();
+
+ // Do it again -- the turbo sets the target MP in the first
+ // run, stabilize sets the current to the target, then we need
+ // to run again to get the correct output torque. Clumsy, but
+ // it works without side effects (other than solver
+ // performance). In the future, the Engine objects should
+ // store state to allow them to do the work themselves.
+ _eng->calc(_pressure, _temp, _omega);
+
+ // Compute torque as seen by the engine's end of the gearbox.
+ // The propeller will be moving more slowly (for gear ratios
+ // less than one), so it's torque will be higher than the
+ // engine's, so multiply by _gearRatio to get the engine-side
+ // value.
+ ptau *= _gearRatio;
float etau = _eng->getTorque();
float tdiff = etau - ptau;
+
+ Math::mul3(thrust, _dir, _thrust);
- if(Math::abs(tdiff/_moment) < 0.1)
+ if(Math::abs(tdiff/(_moment * _gearRatio)) < 0.1)
break;
if(tdiff > 0) {
}
// ...and back off
- _eng->setRunning(false);
+ _eng->setRunning(running_state);
}
void PropEngine::init()
_eng->setMixture(_mixture);
_eng->setFuelState(_fuel);
- _prop->calc(_rho, speed, _omega, &thrust, &propTorque);
+ _prop->calc(_rho, speed, _omega * _gearRatio, &thrust, &propTorque);
+ if(_omega == 0.0)
+ _omega = 0.001; // hack to get around reports of NaNs somewhere...
+ propTorque *= _gearRatio;
_eng->calc(_pressure, _temp, _omega);
+ _eng->integrate(dt);
engTorque = _eng->getTorque();
_fuelFlow = _eng->getFuelFlow();
// Turn the thrust into a vector and save it
Math::mul3(thrust, _dir, _thrust);
+ // We do our "RPM" computations on the engine's side of the
+ // world, so modify the moment value accordingly.
+ float momt = _moment * _gearRatio;
+
// Euler-integrate the RPM. This doesn't need the full-on
// Runge-Kutta stuff.
- float rotacc = (engTorque-propTorque)/Math::abs(_moment);
+ float rotacc = (engTorque-propTorque)/Math::abs(momt);
_omega += dt * rotacc;
+ if (_omega < 0)
+ _omega = 0 - _omega; // don't allow negative RPM
+ // FIXME: introduce proper windmilling
- // Store the total angular momentum into _gyro
- Math::mul3(_omega*_moment, _dir, _gyro);
+ // Store the total angular momentum into _gyro, unless the
+ // propeller is a counter-rotating pair (which has zero net
+ // angular momentum, even though it *does* have an MoI for
+ // acceleration purposes).
+ Math::mul3(_contra ? 0 : _omega*momt, _dir, _gyro);
// Accumulate the engine torque, it acts on the body as a whole.
// (Note: engine torque, not propeller torque. They can be
// different, but the difference goes to accelerating the
// rotation. It is the engine torque that is felt at the shaft
- // and works on the body.)
+ // and works on the body.) (Note 2: contra-rotating propellers do
+ // not exert net torque on the aircraft).
float tau = _moment < 0 ? engTorque : -engTorque;
- Math::mul3(tau, _dir, _torque);
+ Math::mul3(_contra ? 0 : tau, _dir, _torque);
// Iterate the propeller governor, if we have one. Since engine
// torque is basically constant with RPM, we want to make the
// _current_ RPM. Seek to that. This is sort of a continuous
// Newton-Raphson, basically.
if(_variable) {
- float targetOmega = _minOmega + _advance*(_maxOmega-_minOmega);
+ float targetPropSpd = _minOmega + _advance*(_maxOmega-_minOmega);
+ float targetOmega = targetPropSpd / _gearRatio; // -> "engine omega"
float ratio2 = (_omega*_omega)/(targetOmega*targetOmega);
float targetTorque = engTorque * ratio2;
// Convert to an acceleration here, so that big propellers
// don't seek faster than small ones.
- float diff = Math::abs((propTorque - targetTorque) / _moment);
+ float diff = Math::abs((propTorque - targetTorque) / momt);
if(diff < 10) mod = 1 + (mod-1)*(0.1f*diff);
_prop->modPitch(mod);