/*%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
Module: FGPropeller.cpp
Author: Jon S. Berndt
Date started: 08/24/00
Purpose: Encapsulates the propeller object
------------- Copyright (C) 2000 Jon S. Berndt (jsb@hal-pc.org) -------------
This program is free software; you can redistribute it and/or modify it under
the terms of the GNU General Public License as published by the Free Software
Foundation; either version 2 of the License, or (at your option) any later
version.
This program is distributed in the hope that it will be useful, but WITHOUT
ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or FITNESS
FOR A PARTICULAR PURPOSE. See the GNU General Public License for more
details.
You should have received a copy of the GNU General Public License along with
this program; if not, write to the Free Software Foundation, Inc., 59 Temple
Place - Suite 330, Boston, MA 02111-1307, USA.
Further information about the GNU General Public License can also be found on
the world wide web at http://www.gnu.org.
FUNCTIONAL DESCRIPTION
--------------------------------------------------------------------------------
HISTORY
--------------------------------------------------------------------------------
08/24/00 JSB Created
%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
INCLUDES
%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%*/
#include "FGPropeller.h"
#include "FGFCS.h"
static const char *IdSrc = "$Id$";
static const char *IdHdr = ID_PROPELLER;
/*%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
CLASS IMPLEMENTATION
%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%*/
// This class currently makes certain assumptions when calculating torque and
// p-factor. That is, that the axis of rotation is the X axis of the aircraft -
// not just the X-axis of the engine/propeller. This may or may not work for a
// helicopter.
FGPropeller::FGPropeller(FGFDMExec* exec, FGConfigFile* Prop_cfg) : FGThruster(exec)
{
string token;
int rows, cols;
MaxPitch = MinPitch = P_Factor = Sense = Pitch = 0.0;
Name = Prop_cfg->GetValue("NAME");
Prop_cfg->GetNextConfigLine();
while (Prop_cfg->GetValue() != string("/FG_PROPELLER")) {
*Prop_cfg >> token;
if (token == "IXX") {
*Prop_cfg >> Ixx;
} else if (token == "DIAMETER") {
*Prop_cfg >> Diameter;
Diameter /= 12.0;
} else if (token == "NUMBLADES") {
*Prop_cfg >> numBlades;
} else if (token == "MINPITCH") {
*Prop_cfg >> MinPitch;
} else if (token == "MAXPITCH") {
*Prop_cfg >> MaxPitch;
} else if (token == "MINRPM") {
*Prop_cfg >> MinRPM;
} else if (token == "MAXRPM") {
*Prop_cfg >> MaxRPM;
} else if (token == "C_THRUST") {
*Prop_cfg >> rows >> cols;
if (cols == 1) cThrust = new FGTable(rows);
else cThrust = new FGTable(rows, cols);
*cThrust << *Prop_cfg;
} else if (token == "C_POWER") {
*Prop_cfg >> rows >> cols;
if (cols == 1) cPower = new FGTable(rows);
else cPower = new FGTable(rows, cols);
*cPower << *Prop_cfg;
} else if (token == "EOF") {
cerr << " End of file reached" << endl;
break;
} else {
cerr << "Unhandled token in Propeller config file: " << token << endl;
}
}
Type = ttPropeller;
RPM = 0;
vTorque.InitMatrix();
Debug(0);
}
//%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
FGPropeller::~FGPropeller()
{
if (cThrust) delete cThrust;
if (cPower) delete cPower;
Debug(1);
}
//%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
//
// We must be getting the aerodynamic velocity here, NOT the inertial velocity.
// We need the velocity with respect to the wind.
//
// Note that PowerAvailable is the excess power available after the drag of the
// propeller has been subtracted. At equilibrium, PowerAvailable will be zero -
// indicating that the propeller will not accelerate or decelerate.
// Remembering that Torque * omega = Power, we can derive the torque on the
// propeller and its acceleration to give a new RPM. The current RPM will be
// used to calculate thrust.
//
// Because RPM could be zero, we need to be creative about what RPM is stated as.
double FGPropeller::Calculate(double PowerAvailable)
{
double J, C_Thrust, omega;
double Vel = fdmex->GetTranslation()->GetvAeroUVW(eU);
double rho = fdmex->GetAtmosphere()->GetDensity();
double RPS = RPM/60.0;
double alpha, beta;
if (RPM > 0.10) {
J = Vel / (Diameter * RPS);
} else {
J = 0.0;
}
if (MaxPitch == MinPitch) { // Fixed pitch prop
C_Thrust = cThrust->GetValue(J);
} else { // Variable pitch prop
C_Thrust = cThrust->GetValue(J, Pitch);
}
if (P_Factor > 0.0001) {
alpha = fdmex->GetTranslation()->Getalpha();
beta = fdmex->GetTranslation()->Getbeta();
SetActingLocationY( GetLocationY() + P_Factor*alpha*Sense);
SetActingLocationZ( GetLocationZ() + P_Factor*beta*Sense);
} else if (P_Factor < 0.000) {
cerr << "P-Factor value in config file must be greater than zero" << endl;
}
Thrust = C_Thrust*RPS*RPS*Diameter*Diameter*Diameter*Diameter*rho;
omega = RPS*2.0*M_PI;
// Check for windmilling.
double radius = Diameter * 0.375; // 75% of radius
double windmill_cutoff = tan(Pitch * 1.745329E-2) * omega * radius;
if (Vel > windmill_cutoff) {
cout << "Windmilling: " << Vel << " > " << windmill_cutoff << endl;
Thrust = -Thrust;
}
vFn(1) = Thrust;
// The Ixx value and rotation speed given below are for rotation about the
// natural axis of the engine. The transform takes place in the base class
// FGForce::GetBodyForces() function.
vH(eX) = Ixx*omega*Sense;
vH(eY) = 0.0;
vH(eZ) = 0.0;
if (omega <= 5) omega = 1.0;
ExcessTorque = PowerAvailable / omega;
RPM = (RPS + ((ExcessTorque / Ixx) / (2.0 * M_PI)) * deltaT) * 60.0;
vMn = fdmex->GetRotation()->GetPQR()*vH + vTorque*Sense;
return Thrust; // return thrust in pounds
}
//%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
double FGPropeller::GetPowerRequired(void)
{
if (RPM <= 0.10) return 0.0; // If the prop ain't turnin', the fuel ain't burnin'.
double cPReq, RPS = RPM / 60.0;
double J = fdmex->GetTranslation()->GetvAeroUVW(eU) / (Diameter * RPS);
double rho = fdmex->GetAtmosphere()->GetDensity();
if (MaxPitch == MinPitch) { // Fixed pitch prop
Pitch = MinPitch;
cPReq = cPower->GetValue(J);
} else { // Variable pitch prop
double advance = fdmex->GetFCS()->GetPropAdvance(ThrusterNumber);
if (MaxRPM != MinRPM) { // fixed-speed prop
double rpmReq = MinRPM + (MaxRPM - MinRPM) * advance;
double dRPM = rpmReq - RPM;
Pitch -= dRPM / 10;
if (Pitch < MinPitch) Pitch = MinPitch;
else if (Pitch > MaxPitch) Pitch = MaxPitch;
} else {
Pitch = MaxPitch - (MaxPitch - MinPitch) * advance;
}
cPReq = cPower->GetValue(J, Pitch);
}
PowerRequired = cPReq*RPS*RPS*RPS*Diameter*Diameter*Diameter*Diameter
*Diameter*rho;
vTorque(eX) = -Sense*PowerRequired / (RPS*2.0*M_PI);
return PowerRequired;
}
//%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
FGColumnVector3 FGPropeller::GetPFactor()
{
double px=0.0, py, pz;
py = Thrust * Sense * (GetActingLocationY() - GetLocationY()) / 12.0;
pz = Thrust * Sense * (GetActingLocationZ() - GetLocationZ()) / 12.0;
return FGColumnVector3(px, py, pz);
}
//%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
// The bitmasked value choices are as follows:
// unset: In this case (the default) JSBSim would only print
// out the normally expected messages, essentially echoing
// the config files as they are read. If the environment
// variable is not set, debug_lvl is set to 1 internally
// 0: This requests JSBSim not to output any messages
// whatsoever.
// 1: This value explicity requests the normal JSBSim
// startup messages
// 2: This value asks for a message to be printed out when
// a class is instantiated
// 4: When this value is set, a message is displayed when a
// FGModel object executes its Run() method
// 8: When this value is set, various runtime state variables
// are printed out periodically
// 16: When set various parameters are sanity checked and
// a message is printed out when they go out of bounds
void FGPropeller::Debug(int from)
{
if (debug_lvl <= 0) return;
if (debug_lvl & 1) { // Standard console startup message output
if (from == 0) { // Constructor
cout << "\n Propeller Name: " << Name << endl;
cout << " IXX = " << Ixx << endl;
cout << " Diameter = " << Diameter << " ft." << endl;
cout << " Number of Blades = " << numBlades << endl;
cout << " Minimum Pitch = " << MinPitch << endl;
cout << " Maximum Pitch = " << MaxPitch << endl;
cout << " Thrust Coefficient: " << endl;
cThrust->Print();
cout << " Power Coefficient: " << endl;
cPower->Print();
}
}
if (debug_lvl & 2 ) { // Instantiation/Destruction notification
if (from == 0) cout << "Instantiated: FGPropeller" << endl;
if (from == 1) cout << "Destroyed: FGPropeller" << endl;
}
if (debug_lvl & 4 ) { // Run() method entry print for FGModel-derived objects
}
if (debug_lvl & 8 ) { // Runtime state variables
}
if (debug_lvl & 16) { // Sanity checking
}
if (debug_lvl & 64) {
if (from == 0) { // Constructor
cout << IdSrc << endl;
cout << IdHdr << endl;
}
}
}