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