1 /*%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
3 Module: FGPropeller.cpp
6 Purpose: Encapsulates the propeller object
8 ------------- Copyright (C) 2000 Jon S. Berndt (jon@jsbsim.org) -------------
10 This program is free software; you can redistribute it and/or modify it under
11 the terms of the GNU Lesser 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 Lesser General Public License for more
20 You should have received a copy of the GNU Lesser 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 Lesser 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 %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%*/
41 #include "FGPropeller.h"
42 #include "models/FGPropagate.h"
43 #include "models/FGAtmosphere.h"
44 #include "models/FGAuxiliary.h"
45 #include "input_output/FGXMLElement.h"
51 static const char *IdSrc = "$Id$";
52 static const char *IdHdr = ID_PROPELLER;
54 /*%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
56 %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%*/
58 // This class currently makes certain assumptions when calculating torque and
59 // p-factor. That is, that the axis of rotation is the X axis of the aircraft -
60 // not just the X-axis of the engine/propeller. This may or may not work for a
63 FGPropeller::FGPropeller(FGFDMExec* exec, Element* prop_element, int num)
64 : FGThruster(exec, prop_element, num)
67 Element *table_element, *local_element;
69 FGPropertyManager* PropertyManager = exec->GetPropertyManager();
71 MaxPitch = MinPitch = P_Factor = Pitch = Advance = MinRPM = MaxRPM = 0.0;
72 Sense = 1; // default clockwise rotation
78 CtFactor = CpFactor = 1.0;
80 if (prop_element->FindElement("ixx"))
81 Ixx = prop_element->FindElementValueAsNumberConvertTo("ixx", "SLUG*FT2");
82 if (prop_element->FindElement("diameter"))
83 Diameter = prop_element->FindElementValueAsNumberConvertTo("diameter", "FT");
84 if (prop_element->FindElement("numblades"))
85 numBlades = (int)prop_element->FindElementValueAsNumber("numblades");
86 if (prop_element->FindElement("gearratio"))
87 GearRatio = prop_element->FindElementValueAsNumber("gearratio");
88 if (prop_element->FindElement("minpitch"))
89 MinPitch = prop_element->FindElementValueAsNumber("minpitch");
90 if (prop_element->FindElement("maxpitch"))
91 MaxPitch = prop_element->FindElementValueAsNumber("maxpitch");
92 if (prop_element->FindElement("minrpm"))
93 MinRPM = prop_element->FindElementValueAsNumber("minrpm");
94 if (prop_element->FindElement("maxrpm"))
95 MaxRPM = prop_element->FindElementValueAsNumber("maxrpm");
96 if (prop_element->FindElement("reversepitch"))
97 ReversePitch = prop_element->FindElementValueAsNumber("reversepitch");
98 for (int i=0; i<2; i++) {
99 table_element = prop_element->FindNextElement("table");
100 name = table_element->GetAttributeValue("name");
101 if (name == "C_THRUST") {
102 cThrust = new FGTable(PropertyManager, table_element);
103 } else if (name == "C_POWER") {
104 cPower = new FGTable(PropertyManager, table_element);
106 cerr << "Unknown table type: " << name << " in propeller definition." << endl;
110 local_element = prop_element->GetParent()->FindElement("sense");
112 double Sense = local_element->GetDataAsNumber();
113 SetSense(fabs(Sense)/Sense);
115 local_element = prop_element->GetParent()->FindElement("p_factor");
117 P_Factor = local_element->GetDataAsNumber();
120 cerr << "P-Factor value in config file must be greater than zero" << endl;
122 if (prop_element->FindElement("ct_factor"))
123 SetCtFactor( prop_element->FindElementValueAsNumber("ct_factor") );
124 if (prop_element->FindElement("cp_factor"))
125 SetCpFactor( prop_element->FindElementValueAsNumber("cp_factor") );
129 vTorque.InitMatrix();
130 D4 = Diameter*Diameter*Diameter*Diameter;
133 string property_name, base_property_name;
134 base_property_name = CreateIndexedPropertyName("propulsion/engine", EngineNum);
135 property_name = base_property_name + "/advance-ratio";
136 PropertyManager->Tie( property_name.c_str(), &J );
137 property_name = base_property_name + "/blade-angle";
138 PropertyManager->Tie( property_name.c_str(), &Pitch );
139 property_name = base_property_name + "/thrust-coefficient";
140 PropertyManager->Tie( property_name.c_str(), this, &FGPropeller::GetThrustCoefficient );
141 property_name = base_property_name + "/propeller-rpm";
142 PropertyManager->Tie( property_name.c_str(), this, &FGPropeller::GetRPM );
147 //%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
149 FGPropeller::~FGPropeller()
157 //%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
159 // We must be getting the aerodynamic velocity here, NOT the inertial velocity.
160 // We need the velocity with respect to the wind.
162 // Note that PowerAvailable is the excess power available after the drag of the
163 // propeller has been subtracted. At equilibrium, PowerAvailable will be zero -
164 // indicating that the propeller will not accelerate or decelerate.
165 // Remembering that Torque * omega = Power, we can derive the torque on the
166 // propeller and its acceleration to give a new RPM. The current RPM will be
167 // used to calculate thrust.
169 // Because RPM could be zero, we need to be creative about what RPM is stated as.
171 double FGPropeller::Calculate(double PowerAvailable)
173 double omega, alpha, beta;
175 double Vel = fdmex->GetAuxiliary()->GetAeroUVW(eU);
176 double rho = fdmex->GetAtmosphere()->GetDensity();
177 double RPS = RPM/60.0;
179 if (RPS > 0.00) J = Vel / (Diameter * RPS); // Calculate J normally
180 else J = 1000.0; // Set J to a high number
182 if (MaxPitch == MinPitch) ThrustCoeff = cThrust->GetValue(J);
183 else ThrustCoeff = cThrust->GetValue(J, Pitch);
184 ThrustCoeff *= CtFactor;
186 if (P_Factor > 0.0001) {
187 alpha = fdmex->GetAuxiliary()->Getalpha();
188 beta = fdmex->GetAuxiliary()->Getbeta();
189 SetActingLocationY( GetLocationY() + P_Factor*alpha*Sense);
190 SetActingLocationZ( GetLocationZ() + P_Factor*beta*Sense);
193 Thrust = ThrustCoeff*RPS*RPS*D4*rho;
194 omega = RPS*2.0*M_PI;
198 // The Ixx value and rotation speed given below are for rotation about the
199 // natural axis of the engine. The transform takes place in the base class
200 // FGForce::GetBodyForces() function.
202 vH(eX) = Ixx*omega*Sense;
206 if (omega > 0.0) ExcessTorque = GearRatio * PowerAvailable / omega;
207 else ExcessTorque = GearRatio * PowerAvailable / 1.0;
209 RPM = (RPS + ((ExcessTorque / Ixx) / (2.0 * M_PI)) * deltaT) * 60.0;
211 if (RPM < 1.0) RPM = 0; // Engine friction stops rotation arbitrarily at 1 RPM.
213 // Transform Torque and momentum first, as PQR is used in this
214 // equation and cannot be transformed itself.
215 vMn = fdmex->GetPropagate()->GetPQR()*(Transform()*vH) + Transform()*vTorque;
217 return Thrust; // return thrust in pounds
220 //%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
222 double FGPropeller::GetPowerRequired(void)
225 double rho = fdmex->GetAtmosphere()->GetDensity();
226 double RPS = RPM / 60.0;
228 if (RPS != 0) J = fdmex->GetAuxiliary()->GetAeroUVW(eU) / (Diameter * RPS);
229 else J = 1000.0; // Set J to a high number
231 if (MaxPitch == MinPitch) { // Fixed pitch prop
233 cPReq = cPower->GetValue(J);
234 } else { // Variable pitch prop
236 if (MaxRPM != MinRPM) { // fixed-speed prop
238 // do normal calculation when propeller is neither feathered nor reversed
242 double rpmReq = MinRPM + (MaxRPM - MinRPM) * Advance;
243 double dRPM = rpmReq - RPM;
244 // The pitch of a variable propeller cannot be changed when the RPMs are
245 // too low - the oil pump does not work.
246 if (RPM > 200) Pitch -= dRPM * deltaT;
247 if (Pitch < MinPitch) Pitch = MinPitch;
248 else if (Pitch > MaxPitch) Pitch = MaxPitch;
250 } else { // Reversed propeller
252 // when reversed calculate propeller pitch depending on throttle lever position
253 // (beta range for taxing full reverse for braking)
254 double PitchReq = MinPitch - ( MinPitch - ReversePitch ) * Reverse_coef;
255 // The pitch of a variable propeller cannot be changed when the RPMs are
256 // too low - the oil pump does not work.
257 if (RPM > 200) Pitch += (PitchReq - Pitch) / 200;
259 Pitch += (MaxRPM - RPM) / 50;
260 if (Pitch < ReversePitch) Pitch = ReversePitch;
261 else if (Pitch > MaxPitch) Pitch = MaxPitch;
265 } else { // Feathered propeller
266 // ToDo: Make feathered and reverse settings done via FGKinemat
267 Pitch += (MaxPitch - Pitch) / 300; // just a guess (about 5 sec to fully feathered)
270 } else { // Variable Speed Prop
271 Pitch = MinPitch + (MaxPitch - MinPitch) * Advance;
273 cPReq = cPower->GetValue(J, Pitch);
278 PowerRequired = cPReq*RPS*RPS*RPS*D5*rho;
279 vTorque(eX) = -Sense*PowerRequired / (RPS*2.0*M_PI);
285 return PowerRequired;
288 //%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
290 FGColumnVector3 FGPropeller::GetPFactor()
292 double px=0.0, py, pz;
294 py = Thrust * Sense * (GetActingLocationY() - GetLocationY()) / 12.0;
295 pz = Thrust * Sense * (GetActingLocationZ() - GetLocationZ()) / 12.0;
297 return FGColumnVector3(px, py, pz);
300 //%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
302 string FGPropeller::GetThrusterLabels(int id, string delimeter)
304 std::ostringstream buf;
306 buf << Name << " Torque (engine " << id << ")" << delimeter
307 << Name << " PFactor Pitch (engine " << id << ")" << delimeter
308 << Name << " PFactor Yaw (engine " << id << ")" << delimeter
309 << Name << " Thrust (engine " << id << " in lbs)" << delimeter;
311 buf << Name << " Pitch (engine " << id << ")" << delimeter;
312 buf << Name << " RPM (engine " << id << ")";
317 //%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
319 string FGPropeller::GetThrusterValues(int id, string delimeter)
321 std::ostringstream buf;
323 FGColumnVector3 vPFactor = GetPFactor();
324 buf << vTorque(eX) << delimeter
325 << vPFactor(ePitch) << delimeter
326 << vPFactor(eYaw) << delimeter
327 << Thrust << delimeter;
329 buf << Pitch << delimeter;
335 //%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
336 // The bitmasked value choices are as follows:
337 // unset: In this case (the default) JSBSim would only print
338 // out the normally expected messages, essentially echoing
339 // the config files as they are read. If the environment
340 // variable is not set, debug_lvl is set to 1 internally
341 // 0: This requests JSBSim not to output any messages
343 // 1: This value explicity requests the normal JSBSim
345 // 2: This value asks for a message to be printed out when
346 // a class is instantiated
347 // 4: When this value is set, a message is displayed when a
348 // FGModel object executes its Run() method
349 // 8: When this value is set, various runtime state variables
350 // are printed out periodically
351 // 16: When set various parameters are sanity checked and
352 // a message is printed out when they go out of bounds
354 void FGPropeller::Debug(int from)
356 if (debug_lvl <= 0) return;
358 if (debug_lvl & 1) { // Standard console startup message output
359 if (from == 0) { // Constructor
360 cout << "\n Propeller Name: " << Name << endl;
361 cout << " IXX = " << Ixx << endl;
362 cout << " Diameter = " << Diameter << " ft." << endl;
363 cout << " Number of Blades = " << numBlades << endl;
364 cout << " Gear Ratio = " << GearRatio << endl;
365 cout << " Minimum Pitch = " << MinPitch << endl;
366 cout << " Maximum Pitch = " << MaxPitch << endl;
367 cout << " Minimum RPM = " << MinRPM << endl;
368 cout << " Maximum RPM = " << MaxRPM << endl;
369 // cout << " Thrust Coefficient: " << endl;
371 // cout << " Power Coefficient: " << endl;
375 if (debug_lvl & 2 ) { // Instantiation/Destruction notification
376 if (from == 0) cout << "Instantiated: FGPropeller" << endl;
377 if (from == 1) cout << "Destroyed: FGPropeller" << endl;
379 if (debug_lvl & 4 ) { // Run() method entry print for FGModel-derived objects
381 if (debug_lvl & 8 ) { // Runtime state variables
383 if (debug_lvl & 16) { // Sanity checking
385 if (debug_lvl & 64) {
386 if (from == 0) { // Constructor
387 cout << IdSrc << endl;
388 cout << IdHdr << endl;