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 1.39 2011/10/15 13:00:57 bcoconni 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 double omega, PowerAvailable;
199 double Vel = in.AeroUVW(eU);
200 double rho = in.Density;
201 double RPS = RPM/60.0;
203 // Calculate helical tip Mach
204 double Area = 0.25*Diameter*Diameter*M_PI;
205 double Vtip = RPS * Diameter * M_PI;
206 HelicalTipMach = sqrt(Vtip*Vtip + Vel*Vel) / in.Soundspeed;
208 PowerAvailable = EnginePower - GetPowerRequired();
210 if (RPS > 0.0) J = Vel / (Diameter * RPS); // Calculate J normally
211 else J = Vel / Diameter;
213 if (MaxPitch == MinPitch) { // Fixed pitch prop
214 ThrustCoeff = cThrust->GetValue(J);
215 } else { // Variable pitch prop
216 ThrustCoeff = cThrust->GetValue(J, Pitch);
219 // Apply optional scaling factor to Ct (default value = 1)
220 ThrustCoeff *= CtFactor;
222 // Apply optional Mach effects from CT_MACH table
223 if (CtMach) ThrustCoeff *= CtMach->GetValue(HelicalTipMach);
225 if (P_Factor > 0.0001) {
226 SetActingLocationY( GetLocationY() + P_Factor*in.Alpha*Sense);
227 SetActingLocationZ( GetLocationZ() + P_Factor*in.Beta*Sense);
230 Thrust = ThrustCoeff*RPS*RPS*D4*rho;
232 // From B. W. McCormick, "Aerodynamics, Aeronautics, and Flight Mechanics"
233 // first edition, eqn. 6.15 (propeller analysis chapter).
234 Vinduced = 0.5 * (-Vel + sqrt(Vel*Vel + 2.0*Thrust/(rho*Area)));
236 omega = RPS*2.0*M_PI;
240 // The Ixx value and rotation speed given below are for rotation about the
241 // natural axis of the engine. The transform takes place in the base class
242 // FGForce::GetBodyForces() function.
244 vH(eX) = Ixx*omega*Sense;
248 if (omega > 0.0) ExcessTorque = PowerAvailable / omega;
249 else ExcessTorque = PowerAvailable / 1.0;
251 RPM = (RPS + ((ExcessTorque / Ixx) / (2.0 * M_PI)) * deltaT) * 60.0;
253 if (RPM < 0.0) RPM = 0.0; // Engine won't turn backwards
255 // Transform Torque and momentum first, as PQR is used in this
256 // equation and cannot be transformed itself.
257 vMn = in.PQR*(Transform()*vH) + Transform()*vTorque;
259 return Thrust; // return thrust in pounds
262 //%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
264 double FGPropeller::GetPowerRequired(void)
267 double rho = in.Density;
268 double Vel = in.AeroUVW(eU);
269 double RPS = RPM / 60.0;
271 if (RPS != 0.0) J = Vel / (Diameter * RPS);
272 else J = Vel / Diameter;
274 if (MaxPitch == MinPitch) { // Fixed pitch prop
275 cPReq = cPower->GetValue(J);
277 } else { // Variable pitch prop
279 if (ConstantSpeed != 0) { // Constant Speed Mode
281 // do normal calculation when propeller is neither feathered nor reversed
282 // Note: This method of feathering and reversing was added to support the
283 // turboprop model. It's left here for backward compatablity, but
284 // now feathering and reversing should be done in Manual Pitch Mode.
288 double rpmReq = MinRPM + (MaxRPM - MinRPM) * Advance;
289 double dRPM = rpmReq - RPM;
290 // The pitch of a variable propeller cannot be changed when the RPMs are
291 // too low - the oil pump does not work.
292 if (RPM > 200) Pitch -= dRPM * deltaT;
293 if (Pitch < MinPitch) Pitch = MinPitch;
294 else if (Pitch > MaxPitch) Pitch = MaxPitch;
296 } else { // Reversed propeller
298 // when reversed calculate propeller pitch depending on throttle lever position
299 // (beta range for taxing full reverse for braking)
300 double PitchReq = MinPitch - ( MinPitch - ReversePitch ) * Reverse_coef;
301 // The pitch of a variable propeller cannot be changed when the RPMs are
302 // too low - the oil pump does not work.
303 if (RPM > 200) Pitch += (PitchReq - Pitch) / 200;
305 Pitch += (MaxRPM - RPM) / 50;
306 if (Pitch < ReversePitch) Pitch = ReversePitch;
307 else if (Pitch > MaxPitch) Pitch = MaxPitch;
311 } else { // Feathered propeller
312 // ToDo: Make feathered and reverse settings done via FGKinemat
313 Pitch += (MaxPitch - Pitch) / 300; // just a guess (about 5 sec to fully feathered)
316 } else { // Manual Pitch Mode, pitch is controlled externally
320 cPReq = cPower->GetValue(J, Pitch);
323 // Apply optional scaling factor to Cp (default value = 1)
326 // Apply optional Mach effects from CP_MACH table
327 if (CpMach) cPReq *= CpMach->GetValue(HelicalTipMach);
330 PowerRequired = cPReq*RPS*RPS*RPS*D5*rho;
331 vTorque(eX) = -Sense*PowerRequired / (RPS*2.0*M_PI);
333 // For a stationary prop we have to estimate torque first.
334 double CL = (90.0 - Pitch) / 20.0;
335 if (CL > 1.5) CL = 1.5;
336 double BladeArea = Diameter * Diameter / 32.0 * numBlades;
337 vTorque(eX) = -Sense*BladeArea*Diameter*Vel*Vel*rho*0.19*CL;
338 PowerRequired = fabs(vTorque(eX))*0.2*M_PI;
341 return PowerRequired;
344 //%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
346 FGColumnVector3 FGPropeller::GetPFactor()
348 double px=0.0, py, pz;
350 py = Thrust * Sense * (GetActingLocationY() - GetLocationY()) / 12.0;
351 pz = Thrust * Sense * (GetActingLocationZ() - GetLocationZ()) / 12.0;
353 return FGColumnVector3(px, py, pz);
356 //%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
358 string FGPropeller::GetThrusterLabels(int id, string delimeter)
360 std::ostringstream buf;
362 buf << Name << " Torque (engine " << id << ")" << delimeter
363 << Name << " PFactor Pitch (engine " << id << ")" << delimeter
364 << Name << " PFactor Yaw (engine " << id << ")" << delimeter
365 << Name << " Thrust (engine " << id << " in lbs)" << delimeter;
367 buf << Name << " Pitch (engine " << id << ")" << delimeter;
368 buf << Name << " RPM (engine " << id << ")";
373 //%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
375 string FGPropeller::GetThrusterValues(int id, string delimeter)
377 std::ostringstream buf;
379 FGColumnVector3 vPFactor = GetPFactor();
380 buf << vTorque(eX) << delimeter
381 << vPFactor(ePitch) << delimeter
382 << vPFactor(eYaw) << delimeter
383 << Thrust << delimeter;
385 buf << Pitch << delimeter;
391 //%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
392 // The bitmasked value choices are as follows:
393 // unset: In this case (the default) JSBSim would only print
394 // out the normally expected messages, essentially echoing
395 // the config files as they are read. If the environment
396 // variable is not set, debug_lvl is set to 1 internally
397 // 0: This requests JSBSim not to output any messages
399 // 1: This value explicity requests the normal JSBSim
401 // 2: This value asks for a message to be printed out when
402 // a class is instantiated
403 // 4: When this value is set, a message is displayed when a
404 // FGModel object executes its Run() method
405 // 8: When this value is set, various runtime state variables
406 // are printed out periodically
407 // 16: When set various parameters are sanity checked and
408 // a message is printed out when they go out of bounds
410 void FGPropeller::Debug(int from)
412 if (debug_lvl <= 0) return;
414 if (debug_lvl & 1) { // Standard console startup message output
415 if (from == 0) { // Constructor
416 cout << "\n Propeller Name: " << Name << endl;
417 cout << " IXX = " << Ixx << endl;
418 cout << " Diameter = " << Diameter << " ft." << endl;
419 cout << " Number of Blades = " << numBlades << endl;
420 cout << " Gear Ratio = " << GearRatio << endl;
421 cout << " Minimum Pitch = " << MinPitch << endl;
422 cout << " Maximum Pitch = " << MaxPitch << endl;
423 cout << " Minimum RPM = " << MinRPM << endl;
424 cout << " Maximum RPM = " << MaxRPM << endl;
425 // Tables are being printed elsewhere...
426 // cout << " Thrust Coefficient: " << endl;
428 // cout << " Power Coefficient: " << endl;
430 // cout << " Mach Thrust Coefficient: " << endl;
435 // cout << " NONE" << endl;
437 // cout << " Mach Power Coefficient: " << endl;
442 // cout << " NONE" << endl;
446 if (debug_lvl & 2 ) { // Instantiation/Destruction notification
447 if (from == 0) cout << "Instantiated: FGPropeller" << endl;
448 if (from == 1) cout << "Destroyed: FGPropeller" << endl;
450 if (debug_lvl & 4 ) { // Run() method entry print for FGModel-derived objects
452 if (debug_lvl & 8 ) { // Runtime state variables
454 if (debug_lvl & 16) { // Sanity checking
456 if (debug_lvl & 64) {
457 if (from == 0) { // Constructor
458 cout << IdSrc << endl;
459 cout << IdHdr << endl;