1 /*%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
3 Module: FGPropeller.cpp
6 Purpose: Encapsulates the propeller object
8 ------------- Copyright (C) 2000 Jon S. Berndt (jsb@hal-pc.org) -------------
10 This program is free software; you can redistribute it and/or modify it under
11 the terms of the GNU General Public License as published by the Free Software
12 Foundation; either version 2 of the License, or (at your option) any later
15 This program is distributed in the hope that it will be useful, but WITHOUT
16 ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or FITNESS
17 FOR A PARTICULAR PURPOSE. See the GNU General Public License for more
20 You should have received a copy of the GNU General Public License along with
21 this program; if not, write to the Free Software Foundation, Inc., 59 Temple
22 Place - Suite 330, Boston, MA 02111-1307, USA.
24 Further information about the GNU General Public License can also be found on
25 the world wide web at http://www.gnu.org.
27 FUNCTIONAL DESCRIPTION
28 --------------------------------------------------------------------------------
31 --------------------------------------------------------------------------------
34 %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
36 %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%*/
38 #include "FGPropeller.h"
41 static const char *IdSrc = "$Id$";
42 static const char *IdHdr = ID_PROPELLER;
44 /*%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
46 %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%*/
48 // This class currently makes certain assumptions when calculating torque and
49 // p-factor. That is, that the axis of rotation is the X axis of the aircraft -
50 // not just the X-axis of the engine/propeller. This may or may not work for a
53 FGPropeller::FGPropeller(FGFDMExec* exec, FGConfigFile* Prop_cfg) : FGThruster(exec)
58 MaxPitch = MinPitch = P_Factor = Sense = Pitch = 0.0;
60 Name = Prop_cfg->GetValue("NAME");
61 Prop_cfg->GetNextConfigLine();
62 while (Prop_cfg->GetValue() != string("/FG_PROPELLER")) {
66 } else if (token == "DIAMETER") {
67 *Prop_cfg >> Diameter;
69 } else if (token == "NUMBLADES") {
70 *Prop_cfg >> numBlades;
71 } else if (token == "MINPITCH") {
72 *Prop_cfg >> MinPitch;
73 } else if (token == "MAXPITCH") {
74 *Prop_cfg >> MaxPitch;
75 } else if (token == "MINRPM") {
77 } else if (token == "MAXRPM") {
79 } else if (token == "C_THRUST") {
80 *Prop_cfg >> rows >> cols;
81 if (cols == 1) cThrust = new FGTable(rows);
82 else cThrust = new FGTable(rows, cols);
83 *cThrust << *Prop_cfg;
84 } else if (token == "C_POWER") {
85 *Prop_cfg >> rows >> cols;
86 if (cols == 1) cPower = new FGTable(rows);
87 else cPower = new FGTable(rows, cols);
89 } else if (token == "EOF") {
90 cerr << " End of file reached" << endl;
93 cerr << "Unhandled token in Propeller config file: " << token << endl;
104 //%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
106 FGPropeller::~FGPropeller()
108 if (cThrust) delete cThrust;
109 if (cPower) delete cPower;
113 //%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
115 // We must be getting the aerodynamic velocity here, NOT the inertial velocity.
116 // We need the velocity with respect to the wind.
118 // Note that PowerAvailable is the excess power available after the drag of the
119 // propeller has been subtracted. At equilibrium, PowerAvailable will be zero -
120 // indicating that the propeller will not accelerate or decelerate.
121 // Remembering that Torque * omega = Power, we can derive the torque on the
122 // propeller and its acceleration to give a new RPM. The current RPM will be
123 // used to calculate thrust.
125 // Because RPM could be zero, we need to be creative about what RPM is stated as.
127 double FGPropeller::Calculate(double PowerAvailable)
129 double J, C_Thrust, omega;
130 double Vel = fdmex->GetTranslation()->GetvAeroUVW(eU);
131 double rho = fdmex->GetAtmosphere()->GetDensity();
132 double RPS = RPM/60.0;
136 J = Vel / (Diameter * RPS);
141 if (MaxPitch == MinPitch) { // Fixed pitch prop
142 C_Thrust = cThrust->GetValue(J);
143 } else { // Variable pitch prop
144 C_Thrust = cThrust->GetValue(J, Pitch);
147 if (P_Factor > 0.0001) {
148 alpha = fdmex->GetTranslation()->Getalpha();
149 beta = fdmex->GetTranslation()->Getbeta();
150 SetActingLocationY( GetLocationY() + P_Factor*alpha*Sense);
151 SetActingLocationZ( GetLocationZ() + P_Factor*beta*Sense);
152 } else if (P_Factor < 0.000) {
153 cerr << "P-Factor value in config file must be greater than zero" << endl;
156 Thrust = C_Thrust*RPS*RPS*Diameter*Diameter*Diameter*Diameter*rho;
157 omega = RPS*2.0*M_PI;
159 // Check for windmilling.
160 double radius = Diameter * 0.375; // 75% of radius
161 double windmill_cutoff = tan(Pitch * 1.745329E-2) * omega * radius;
162 if (Vel > windmill_cutoff) {
163 cout << "Windmilling: " << Vel << " > " << windmill_cutoff << endl;
169 // The Ixx value and rotation speed given below are for rotation about the
170 // natural axis of the engine. The transform takes place in the base class
171 // FGForce::GetBodyForces() function.
173 vH(eX) = Ixx*omega*Sense;
177 if (omega <= 5) omega = 1.0;
179 ExcessTorque = PowerAvailable / omega;
180 RPM = (RPS + ((ExcessTorque / Ixx) / (2.0 * M_PI)) * deltaT) * 60.0;
182 vMn = fdmex->GetRotation()->GetPQR()*vH + vTorque*Sense;
184 return Thrust; // return thrust in pounds
187 //%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
189 double FGPropeller::GetPowerRequired(void)
191 if (RPM <= 0.10) return 0.0; // If the prop ain't turnin', the fuel ain't burnin'.
193 double cPReq, RPS = RPM / 60.0;
195 double J = fdmex->GetTranslation()->GetvAeroUVW(eU) / (Diameter * RPS);
196 double rho = fdmex->GetAtmosphere()->GetDensity();
198 if (MaxPitch == MinPitch) { // Fixed pitch prop
200 cPReq = cPower->GetValue(J);
201 } else { // Variable pitch prop
202 double advance = fdmex->GetFCS()->GetPropAdvance(ThrusterNumber);
204 if (MaxRPM != MinRPM) { // fixed-speed prop
205 double rpmReq = MinRPM + (MaxRPM - MinRPM) * advance;
206 double dRPM = rpmReq - RPM;
210 if (Pitch < MinPitch) Pitch = MinPitch;
211 else if (Pitch > MaxPitch) Pitch = MaxPitch;
214 Pitch = MaxPitch - (MaxPitch - MinPitch) * advance;
216 cPReq = cPower->GetValue(J, Pitch);
219 PowerRequired = cPReq*RPS*RPS*RPS*Diameter*Diameter*Diameter*Diameter
221 vTorque(eX) = -Sense*PowerRequired / (RPS*2.0*M_PI);
223 return PowerRequired;
226 //%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
228 FGColumnVector3 FGPropeller::GetPFactor()
230 double px=0.0, py, pz;
232 py = Thrust * Sense * (GetActingLocationY() - GetLocationY()) / 12.0;
233 pz = Thrust * Sense * (GetActingLocationZ() - GetLocationZ()) / 12.0;
235 return FGColumnVector3(px, py, pz);
238 //%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
239 // The bitmasked value choices are as follows:
240 // unset: In this case (the default) JSBSim would only print
241 // out the normally expected messages, essentially echoing
242 // the config files as they are read. If the environment
243 // variable is not set, debug_lvl is set to 1 internally
244 // 0: This requests JSBSim not to output any messages
246 // 1: This value explicity requests the normal JSBSim
248 // 2: This value asks for a message to be printed out when
249 // a class is instantiated
250 // 4: When this value is set, a message is displayed when a
251 // FGModel object executes its Run() method
252 // 8: When this value is set, various runtime state variables
253 // are printed out periodically
254 // 16: When set various parameters are sanity checked and
255 // a message is printed out when they go out of bounds
257 void FGPropeller::Debug(int from)
259 if (debug_lvl <= 0) return;
261 if (debug_lvl & 1) { // Standard console startup message output
262 if (from == 0) { // Constructor
263 cout << "\n Propeller Name: " << Name << endl;
264 cout << " IXX = " << Ixx << endl;
265 cout << " Diameter = " << Diameter << " ft." << endl;
266 cout << " Number of Blades = " << numBlades << endl;
267 cout << " Minimum Pitch = " << MinPitch << endl;
268 cout << " Maximum Pitch = " << MaxPitch << endl;
269 cout << " Thrust Coefficient: " << endl;
271 cout << " Power Coefficient: " << endl;
275 if (debug_lvl & 2 ) { // Instantiation/Destruction notification
276 if (from == 0) cout << "Instantiated: FGPropeller" << endl;
277 if (from == 1) cout << "Destroyed: FGPropeller" << endl;
279 if (debug_lvl & 4 ) { // Run() method entry print for FGModel-derived objects
281 if (debug_lvl & 8 ) { // Runtime state variables
283 if (debug_lvl & 16) { // Sanity checking
285 if (debug_lvl & 64) {
286 if (from == 0) { // Constructor
287 cout << IdSrc << endl;
288 cout << IdHdr << endl;