11/15/10 T.Kreitler treated flow solver bug, flow and torque calculations
simplified, tiploss influence removed from flapping angles
01/10/11 T.Kreitler changed to single rotor model
+03/06/11 T.Kreitler added brake, clutch, and experimental free-wheeling-unit,
+ reasonable estimate for inflowlag
%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
INCLUDES
namespace JSBSim {
-static const char *IdSrc = "$Id: FGRotor.cpp,v 1.11 2011/01/17 22:09:59 jberndt Exp $";
+static const char *IdSrc = "$Id: FGRotor.cpp,v 1.12 2011/03/10 01:35:25 dpculp Exp $";
static const char *IdHdr = ID_ROTOR;
/*%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
// control
ControlMap(eMainCtrl),
- CollectiveCtrl(0.0), LateralCtrl(0.0), LongitudinalCtrl(0.0)
+ CollectiveCtrl(0.0), LateralCtrl(0.0), LongitudinalCtrl(0.0),
+ BrakeCtrlNorm(0.0), MaxBrakePower(0.0),
+
+ // free-wheeling-unit (FWU)
+ FreeWheelPresent(0), FreeWheelThresh(0.0), FreeWheelTransmission(0.0)
{
FGColumnVector3 location(0.0, 0.0, 0.0), orientation(0.0, 0.0, 0.0);
// calculation would cause jumps too. 1Hz seems sufficient.
damp_hagl = Filter(1.0,dt);
+ // avoid too abrupt changes in power transmission
+ FreeWheelLag = Filter(200.0,dt);
+
// enable import-export
BindModel();
//%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
// 1. read configuration and try to fill holes, ymmv
-// 2. calculate derived parameters and transforms
+// 2. calculate derived parameters
void FGRotor::Configure(Element* rotor_element)
{
estimate = sqr(BladeChord) * sqr(Radius - HingeOffset) * 0.57;
BladeFlappingMoment = ConfigValueConv(rotor_element, "flappingmoment", estimate, "SLUG*FT2");
- BladeFlappingMoment = Constrain(0.001, BladeFlappingMoment, 1e9);
+ BladeFlappingMoment = Constrain(1.0e-6, BladeFlappingMoment, 1e9);
// guess mass from moment of a thin stick, and multiply by the blades cg distance
estimate = ( 3.0 * BladeFlappingMoment / sqr(Radius) ) * (0.45 * Radius) ;
BladeMassMoment = ConfigValue(rotor_element, "massmoment", estimate); // unit is slug-ft
BladeMassMoment = Constrain(0.001, BladeMassMoment, 1e9);
- TipLossB = ConfigValue(rotor_element, "tiplossfactor", 1.0, silent);
-
estimate = 1.1 * BladeFlappingMoment * BladeNum;
PolarMoment = ConfigValueConv(rotor_element, "polarmoment", estimate, "SLUG*FT2");
- PolarMoment = Constrain(0.001, PolarMoment, 1e9);
+ PolarMoment = Constrain(1e-6, PolarMoment, 1e9);
- InflowLag = ConfigValue(rotor_element, "inflowlag", 0.2, yell); // fixme, depends on size
- InflowLag = Constrain(1e-6, InflowLag, 2.0);
+ // "inflowlag" is treated further down.
+ TipLossB = ConfigValue(rotor_element, "tiplossfactor", 1.0, silent);
+
+ estimate = 0.01 * PolarMoment ; // guesses for huey, bo105 20-30hp
+ MaxBrakePower = ConfigValueConv(rotor_element, "maxbrakepower", estimate, "HP");
+ MaxBrakePower *= hptoftlbssec;
// ground effect
if (rotor_element->FindElement("cgroundeffect")) {
GroundEffectExp = ConfigValue(rotor_element, "groundeffectexp", 0.0);
GroundEffectShift = ConfigValueConv(rotor_element, "groundeffectshift", 0.0, "FT");
+ // handle optional free-wheeling-unit (FWU)
+ FreeWheelPresent = 0;
+ FreeWheelTransmission = 1.0;
+ if (rotor_element->FindElement("freewheelthresh")) {
+ FreeWheelThresh = rotor_element->FindElementValueAsNumber("freewheelthresh");
+ if (FreeWheelThresh > 1.0) {
+ FreeWheelPresent = 1;
+ FreeWheelTransmission = 0.0;
+ }
+ }
+
// precalc often used powers
R[0]=1.0; R[1]=Radius; R[2]=R[1]*R[1]; R[3]=R[2]*R[1]; R[4]=R[3]*R[1];
B[0]=1.0; B[1]=TipLossB; B[2]=B[1]*B[1]; B[3]=B[2]*B[1]; B[4]=B[3]*B[1];
LockNumberByRho = LiftCurveSlope * BladeChord * R[4] / BladeFlappingMoment;
Solidity = BladeNum * BladeChord / (M_PI * Radius);
+ // estimate inflow lag, see /GE49/ eqn(1)
+ double omega_tmp = (NominalRPM/60.0)*2.0*M_PI;
+ estimate = 16.0/(LockNumberByRho*rho * omega_tmp ); // 16/(gamma*Omega)
+ // printf("# Est. InflowLag: %f\n", estimate);
+ InflowLag = ConfigValue(rotor_element, "inflowlag", estimate, yell);
+ InflowLag = Constrain(1.0e-6, InflowLag, 2.0);
+
return;
} // Configure
av_w_fus(eP)= av_s_fus(eP)*cos(beta_orient) + av_s_fus(eQ)*sin(beta_orient);
av_w_fus(eQ)= - av_s_fus(eP)*sin(beta_orient) + av_s_fus(eQ)*cos(beta_orient);
av_w_fus(eR)= av_s_fus(eR);
-
+
return av_w_fus;
}
double ct_over_sigma = 0.0;
double c0, ct_l, ct_t0, ct_t1;
- double mu2;
+ double mu2;
mu = Uw/(Omega*Radius); // /SH79/ eqn(24)
mu2 = sqr(mu);
ct_t0 = (1.0/3.0*B[3] + 1.0/2.0 * TipLossB*mu2 - 4.0/(9.0*M_PI) * mu*mu2 ) * theta_0;
ct_t1 = (1.0/4.0*B[4] + 1.0/4.0 * B[2]*mu2) * BladeTwist;
- ct_l = (1.0/2.0*B[2] + 1.0/4.0 * mu2) * lambda; // first time
+ ct_l = (1.0/2.0*B[2] + 1.0/4.0 * mu2) * lambda; // first time
c0 = (LiftCurveSlope/2.0)*(ct_l + ct_t0 + ct_t1) * Solidity;
c0 = c0 / ( 2.0 * sqrt( sqr(mu) + sqr(lambda) ) + 1e-15);
void FGRotor::calc_drag_and_side_forces(double theta_0)
{
- double cy_over_sigma ;
+ double cy_over_sigma;
double t075 = theta_0 + 0.75 * BladeTwist;
H_drag = Thrust * a_dw;
// Simplified version of /SH79/ eqn(36). Uses an estimate for blade drag
// (a new config parameter to come...).
-// From "Bramwell's Helicopter Dynamics" second edition, eqn(3.43) and (3.44)
+// From "Bramwell's Helicopter Dynamics", second edition, eqn(3.43) and (3.44)
void FGRotor::calc_torque(double theta_0)
{
FGColumnVector3 vHub_ca, avFus_ca;
double h_agl_ft, filtered_hagl = 0.0;
- double ge_factor = 1.0;
+ double ge_factor = 1.0;
// fetch needed values from environment
Vt = fdmex->GetAuxiliary()->GetVt(); // total vehicle velocity including wind
//%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
-double FGRotor::GetPowerRequired(void)
-{
- CalcStatePart1();
- PowerRequired = Torque * Omega;
- return PowerRequired;
+// Simulation of a free-wheeling-unit (FWU). Might need improvements.
+
+void FGRotor::calc_freewheel_state(double p_source, double p_load) {
+
+ // engine is off/detached, release.
+ if (p_source<1e-3) {
+ FreeWheelTransmission = 0.0;
+ return;
+ }
+
+ // engine is driving the rotor, engage.
+ if (p_source >= p_load) {
+ FreeWheelTransmission = 1.0;
+ return;
+ }
+
+ // releases if engine is detached, but stays calm if
+ // the load changes due to rotor dynamics.
+ if (p_source > 0.0 && p_load/(p_source+0.1) > FreeWheelThresh ) {
+ FreeWheelTransmission = 0.0;
+ return;
+ }
+
+ return;
}
//%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
-double FGRotor::Calculate(double PowerAvailable)
+double FGRotor::Calculate(double EnginePower)
{
- CalcStatePart2(PowerAvailable);
+ double FWmult = 1.0;
+ double DeltaPower;
+
+ CalcStatePart1();
+
+ PowerRequired = Torque * Omega + BrakeCtrlNorm * MaxBrakePower;
+
+ if (FreeWheelPresent) {
+ calc_freewheel_state(EnginePower * ClutchCtrlNorm, PowerRequired);
+ FWmult = FreeWheelLag.execute(FreeWheelTransmission);
+ }
+
+ DeltaPower = EnginePower * ClutchCtrlNorm * FWmult - PowerRequired;
+
+ CalcStatePart2(DeltaPower);
+
return Thrust;
}
property_name = base_property_name + "/phi-downwash-rad";
PropertyManager->Tie( property_name.c_str(), this, &FGRotor::GetPhiDW );
-
+
switch (ControlMap) {
case eTailCtrl:
property_name = base_property_name + "/antitorque-ctrl-rad";
PropertyManager->Tie( property_name.c_str(), this, &FGRotor::GetLongitudinalCtrl, &FGRotor::SetLongitudinalCtrl);
}
+ property_name = base_property_name + "/brake-ctrl-norm";
+ PropertyManager->Tie( property_name.c_str(), this, &FGRotor::GetBrakeCtrl, &FGRotor::SetBrakeCtrl);
+ property_name = base_property_name + "/free-wheel-transmission";
+ PropertyManager->Tie( property_name.c_str(), this, &FGRotor::GetFreeWheelTransmission);
+
if (ExternalRPM) {
if (RPMdefinition == -1) {
property_name = base_property_name + "/x-rpm-dict";
cout << " Tip Loss = " << TipLossB << endl;
cout << " Lock Number = " << LockNumberByRho * 0.002356 << " (SL)" << endl;
cout << " Solidity = " << Solidity << endl;
+ cout << " Max Brake Power = " << MaxBrakePower/hptoftlbssec << " HP" << endl;
switch (ControlMap) {
case eTailCtrl: ControlMapName = "Tail Rotor"; break;
}
cout << " Control Mapping = " << ControlMapName << endl;
+ if (FreeWheelPresent) {
+ cout << " Free Wheel Threshold = " << FreeWheelThresh << endl;
+ } else {
+ cout << " No FWU present" << endl;
+ }
+
}
}
if (debug_lvl & 2 ) { // Instantiation/Destruction notification
projects / flightgear.git / blobdiff