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 "input_output/FGXMLElement.h"
48 static const char *IdSrc = "$Id: FGPropeller.cpp,v 1.41 2011/11/17 21:07:30 jentron Exp $";
49 static const char *IdHdr = ID_PROPELLER;
51 /*%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
53 %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%*/
55 // This class currently makes certain assumptions when calculating torque and
56 // p-factor. That is, that the axis of rotation is the X axis of the aircraft -
57 // not just the X-axis of the engine/propeller. This may or may not work for a
60 FGPropeller::FGPropeller(FGFDMExec* exec, Element* prop_element, int num)
61 : FGThruster(exec, prop_element, num)
64 Element *table_element, *local_element;
66 FGPropertyManager* PropertyManager = exec->GetPropertyManager();
68 MaxPitch = MinPitch = P_Factor = Pitch = Advance = MinRPM = MaxRPM = 0.0;
69 Sense = 1; // default clockwise rotation
75 CtFactor = CpFactor = 1.0;
77 cThrust = cPower = CtMach = CpMach = 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");
98 if (prop_element->FindElement("constspeed"))
99 ConstantSpeed = (int)prop_element->FindElementValueAsNumber("constspeed");
100 if (prop_element->FindElement("reversepitch"))
101 ReversePitch = prop_element->FindElementValueAsNumber("reversepitch");
102 while((table_element = prop_element->FindNextElement("table")) != 0) {
103 name = table_element->GetAttributeValue("name");
105 if (name == "C_THRUST") {
106 cThrust = new FGTable(PropertyManager, table_element);
107 } else if (name == "C_POWER") {
108 cPower = new FGTable(PropertyManager, table_element);
109 } else if (name == "CT_MACH") {
110 CtMach = new FGTable(PropertyManager, table_element);
111 } else if (name == "CP_MACH") {
112 CpMach = new FGTable(PropertyManager, table_element);
114 cerr << "Unknown table type: " << name << " in propeller definition." << endl;
116 } catch (std::string str) {
117 throw("Error loading propeller table:" + name + ". " + str);
120 if( (cPower == 0) || (cThrust == 0)){
121 cerr << "Propeller configuration must contain C_THRUST and C_POWER tables!" << endl;
124 local_element = prop_element->GetParent()->FindElement("sense");
126 double Sense = local_element->GetDataAsNumber();
127 SetSense(Sense >= 0.0 ? 1.0 : -1.0);
129 local_element = prop_element->GetParent()->FindElement("p_factor");
131 P_Factor = local_element->GetDataAsNumber();
134 cerr << "P-Factor value in propeller configuration file must be greater than zero" << endl;
136 if (prop_element->FindElement("ct_factor"))
137 SetCtFactor( prop_element->FindElementValueAsNumber("ct_factor") );
138 if (prop_element->FindElement("cp_factor"))
139 SetCpFactor( prop_element->FindElementValueAsNumber("cp_factor") );
143 vTorque.InitMatrix();
144 D4 = Diameter*Diameter*Diameter*Diameter;
148 string property_name, base_property_name;
149 base_property_name = CreateIndexedPropertyName("propulsion/engine", EngineNum);
150 property_name = base_property_name + "/engine-rpm";
151 PropertyManager->Tie( property_name.c_str(), this, &FGPropeller::GetEngineRPM );
152 property_name = base_property_name + "/advance-ratio";
153 PropertyManager->Tie( property_name.c_str(), &J );
154 property_name = base_property_name + "/blade-angle";
155 PropertyManager->Tie( property_name.c_str(), &Pitch );
156 property_name = base_property_name + "/thrust-coefficient";
157 PropertyManager->Tie( property_name.c_str(), this, &FGPropeller::GetThrustCoefficient );
158 property_name = base_property_name + "/propeller-rpm";
159 PropertyManager->Tie( property_name.c_str(), this, &FGPropeller::GetRPM );
160 property_name = base_property_name + "/helical-tip-Mach";
161 PropertyManager->Tie( property_name.c_str(), this, &FGPropeller::GetHelicalTipMach );
162 property_name = base_property_name + "/constant-speed-mode";
163 PropertyManager->Tie( property_name.c_str(), this, &FGPropeller::GetConstantSpeed,
164 &FGPropeller::SetConstantSpeed );
165 property_name = base_property_name + "/prop-induced-velocity_fps";
166 PropertyManager->Tie( property_name.c_str(), this, &FGPropeller::GetInducedVelocity,
167 &FGPropeller::SetInducedVelocity );
172 //%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
174 FGPropeller::~FGPropeller()
184 //%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
186 // We must be getting the aerodynamic velocity here, NOT the inertial velocity.
187 // We need the velocity with respect to the wind.
189 // Remembering that Torque * omega = Power, we can derive the torque on the
190 // propeller and its acceleration to give a new RPM. The current RPM will be
191 // used to calculate thrust.
193 // Because RPM could be zero, we need to be creative about what RPM is stated as.
195 double FGPropeller::Calculate(double EnginePower)
197 FGColumnVector3 localAeroVel = Transform().Transposed() * in.AeroUVW;
198 double omega, PowerAvailable;
200 double Vel = localAeroVel(eU);
201 double rho = in.Density;
202 double RPS = RPM/60.0;
204 // Calculate helical tip Mach
205 double Area = 0.25*Diameter*Diameter*M_PI;
206 double Vtip = RPS * Diameter * M_PI;
207 HelicalTipMach = sqrt(Vtip*Vtip + Vel*Vel) / in.Soundspeed;
209 PowerAvailable = EnginePower - GetPowerRequired();
211 if (RPS > 0.0) J = Vel / (Diameter * RPS); // Calculate J normally
212 else J = Vel / Diameter;
214 if (MaxPitch == MinPitch) { // Fixed pitch prop
215 ThrustCoeff = cThrust->GetValue(J);
216 } else { // Variable pitch prop
217 ThrustCoeff = cThrust->GetValue(J, Pitch);
220 // Apply optional scaling factor to Ct (default value = 1)
221 ThrustCoeff *= CtFactor;
223 // Apply optional Mach effects from CT_MACH table
224 if (CtMach) ThrustCoeff *= CtMach->GetValue(HelicalTipMach);
226 Thrust = ThrustCoeff*RPS*RPS*D4*rho;
228 // Induced velocity in the propeller disk area. This formula is obtained
229 // from momentum theory - see B. W. McCormick, "Aerodynamics, Aeronautics,
230 // and Flight Mechanics" 1st edition, eqn. 6.15 (propeller analysis chapter).
231 // Vinduced = 0.5 * (-Vel + sqrt(Vel*Vel + 2.0*Thrust/(rho*Area)))
232 // Since Thrust and Vel can both be negative we need to adjust this formula
233 // To handle sign (direction) separately from magnitude.
234 double Vel2sum = Vel*abs(Vel) + 2.0*Thrust/(rho*Area);
237 Vinduced = 0.5 * (-Vel + sqrt(Vel2sum));
239 Vinduced = 0.5 * (-Vel - sqrt(-Vel2sum));
241 // P-factor is simulated by a shift of the acting location of the thrust.
242 // The shift is a multiple of the angle between the propeller shaft axis
243 // and the relative wind that goes through the propeller disk.
244 if (P_Factor > 0.0001) {
245 double tangentialVel = localAeroVel.Magnitude(eV, eW);
247 if (tangentialVel > 0.0001) {
248 double angle = atan2(tangentialVel, localAeroVel(eU));
249 double factor = Sense * P_Factor * angle / tangentialVel;
250 SetActingLocationY( GetLocationY() + factor * localAeroVel(eW));
251 SetActingLocationZ( GetLocationZ() + factor * localAeroVel(eV));
255 omega = RPS*2.0*M_PI;
259 // The Ixx value and rotation speed given below are for rotation about the
260 // natural axis of the engine. The transform takes place in the base class
261 // FGForce::GetBodyForces() function.
263 vH(eX) = Ixx*omega*Sense;
267 if (omega > 0.0) ExcessTorque = PowerAvailable / omega;
268 else ExcessTorque = PowerAvailable / 1.0;
270 RPM = (RPS + ((ExcessTorque / Ixx) / (2.0 * M_PI)) * deltaT) * 60.0;
272 if (RPM < 0.0) RPM = 0.0; // Engine won't turn backwards
274 // Transform Torque and momentum first, as PQR is used in this
275 // equation and cannot be transformed itself.
276 vMn = in.PQR*(Transform()*vH) + Transform()*vTorque;
278 return Thrust; // return thrust in pounds
281 //%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
283 double FGPropeller::GetPowerRequired(void)
286 double rho = in.Density;
287 double Vel = in.AeroUVW(eU);
288 double RPS = RPM / 60.0;
290 if (RPS != 0.0) J = Vel / (Diameter * RPS);
291 else J = Vel / Diameter;
293 if (MaxPitch == MinPitch) { // Fixed pitch prop
294 cPReq = cPower->GetValue(J);
296 } else { // Variable pitch prop
298 if (ConstantSpeed != 0) { // Constant Speed Mode
300 // do normal calculation when propeller is neither feathered nor reversed
301 // Note: This method of feathering and reversing was added to support the
302 // turboprop model. It's left here for backward compatablity, but
303 // now feathering and reversing should be done in Manual Pitch Mode.
307 double rpmReq = MinRPM + (MaxRPM - MinRPM) * Advance;
308 double dRPM = rpmReq - RPM;
309 // The pitch of a variable propeller cannot be changed when the RPMs are
310 // too low - the oil pump does not work.
311 if (RPM > 200) Pitch -= dRPM * deltaT;
312 if (Pitch < MinPitch) Pitch = MinPitch;
313 else if (Pitch > MaxPitch) Pitch = MaxPitch;
315 } else { // Reversed propeller
317 // when reversed calculate propeller pitch depending on throttle lever position
318 // (beta range for taxing full reverse for braking)
319 double PitchReq = MinPitch - ( MinPitch - ReversePitch ) * Reverse_coef;
320 // The pitch of a variable propeller cannot be changed when the RPMs are
321 // too low - the oil pump does not work.
322 if (RPM > 200) Pitch += (PitchReq - Pitch) / 200;
324 Pitch += (MaxRPM - RPM) / 50;
325 if (Pitch < ReversePitch) Pitch = ReversePitch;
326 else if (Pitch > MaxPitch) Pitch = MaxPitch;
330 } else { // Feathered propeller
331 // ToDo: Make feathered and reverse settings done via FGKinemat
332 Pitch += (MaxPitch - Pitch) / 300; // just a guess (about 5 sec to fully feathered)
335 } else { // Manual Pitch Mode, pitch is controlled externally
339 cPReq = cPower->GetValue(J, Pitch);
342 // Apply optional scaling factor to Cp (default value = 1)
345 // Apply optional Mach effects from CP_MACH table
346 if (CpMach) cPReq *= CpMach->GetValue(HelicalTipMach);
349 PowerRequired = cPReq*RPS*RPS*RPS*D5*rho;
350 vTorque(eX) = -Sense*PowerRequired / (RPS*2.0*M_PI);
352 // For a stationary prop we have to estimate torque first.
353 double CL = (90.0 - Pitch) / 20.0;
354 if (CL > 1.5) CL = 1.5;
355 double BladeArea = Diameter * Diameter / 32.0 * numBlades;
356 vTorque(eX) = -Sense*BladeArea*Diameter*fabs(Vel)*Vel*rho*0.19*CL;
357 PowerRequired = Sense*(vTorque(eX))*0.2*M_PI;
360 return PowerRequired;
363 //%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
365 FGColumnVector3 FGPropeller::GetPFactor() const
367 double px=0.0, py, pz;
369 py = Thrust * Sense * (GetActingLocationY() - GetLocationY()) / 12.0;
370 pz = Thrust * Sense * (GetActingLocationZ() - GetLocationZ()) / 12.0;
372 return FGColumnVector3(px, py, pz);
375 //%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
377 string FGPropeller::GetThrusterLabels(int id, const string& delimeter)
379 std::ostringstream buf;
381 buf << Name << " Torque (engine " << id << ")" << delimeter
382 << Name << " PFactor Pitch (engine " << id << ")" << delimeter
383 << Name << " PFactor Yaw (engine " << id << ")" << delimeter
384 << Name << " Thrust (engine " << id << " in lbs)" << delimeter;
386 buf << Name << " Pitch (engine " << id << ")" << delimeter;
387 buf << Name << " RPM (engine " << id << ")";
392 //%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
394 string FGPropeller::GetThrusterValues(int id, const string& delimeter)
396 std::ostringstream buf;
398 FGColumnVector3 vPFactor = GetPFactor();
399 buf << vTorque(eX) << delimeter
400 << vPFactor(ePitch) << delimeter
401 << vPFactor(eYaw) << delimeter
402 << Thrust << delimeter;
404 buf << Pitch << delimeter;
410 //%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
411 // The bitmasked value choices are as follows:
412 // unset: In this case (the default) JSBSim would only print
413 // out the normally expected messages, essentially echoing
414 // the config files as they are read. If the environment
415 // variable is not set, debug_lvl is set to 1 internally
416 // 0: This requests JSBSim not to output any messages
418 // 1: This value explicity requests the normal JSBSim
420 // 2: This value asks for a message to be printed out when
421 // a class is instantiated
422 // 4: When this value is set, a message is displayed when a
423 // FGModel object executes its Run() method
424 // 8: When this value is set, various runtime state variables
425 // are printed out periodically
426 // 16: When set various parameters are sanity checked and
427 // a message is printed out when they go out of bounds
429 void FGPropeller::Debug(int from)
431 if (debug_lvl <= 0) return;
433 if (debug_lvl & 1) { // Standard console startup message output
434 if (from == 0) { // Constructor
435 cout << "\n Propeller Name: " << Name << endl;
436 cout << " IXX = " << Ixx << endl;
437 cout << " Diameter = " << Diameter << " ft." << endl;
438 cout << " Number of Blades = " << numBlades << endl;
439 cout << " Gear Ratio = " << GearRatio << endl;
440 cout << " Minimum Pitch = " << MinPitch << endl;
441 cout << " Maximum Pitch = " << MaxPitch << endl;
442 cout << " Minimum RPM = " << MinRPM << endl;
443 cout << " Maximum RPM = " << MaxRPM << endl;
444 // Tables are being printed elsewhere...
445 // cout << " Thrust Coefficient: " << endl;
447 // cout << " Power Coefficient: " << endl;
449 // cout << " Mach Thrust Coefficient: " << endl;
454 // cout << " NONE" << endl;
456 // cout << " Mach Power Coefficient: " << endl;
461 // cout << " NONE" << endl;
465 if (debug_lvl & 2 ) { // Instantiation/Destruction notification
466 if (from == 0) cout << "Instantiated: FGPropeller" << endl;
467 if (from == 1) cout << "Destroyed: FGPropeller" << endl;
469 if (debug_lvl & 4 ) { // Run() method entry print for FGModel-derived objects
471 if (debug_lvl & 8 ) { // Runtime state variables
473 if (debug_lvl & 16) { // Sanity checking
475 if (debug_lvl & 64) {
476 if (from == 0) { // Constructor
477 cout << IdSrc << endl;
478 cout << IdHdr << endl;