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 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 %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%*/
40 #include "FGPropeller.h"
41 #include <models/FGPropagate.h>
42 #include <models/FGAtmosphere.h>
43 #include <models/FGAuxiliary.h>
47 static const char *IdSrc = "$Id$";
48 static const char *IdHdr = ID_PROPELLER;
50 /*%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
52 %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%*/
54 // This class currently makes certain assumptions when calculating torque and
55 // p-factor. That is, that the axis of rotation is the X axis of the aircraft -
56 // not just the X-axis of the engine/propeller. This may or may not work for a
59 FGPropeller::FGPropeller(FGFDMExec* exec, Element* prop_element, int num)
60 : FGThruster(exec, prop_element, num)
63 Element *table_element, *local_element;
65 FGPropertyManager* PropertyManager = exec->GetPropertyManager();
67 MaxPitch = MinPitch = P_Factor = Pitch = Advance = MinRPM = MaxRPM = 0.0;
68 Sense = 1; // default clockwise rotation
74 CtFactor = CpFactor = 1.0;
76 if (prop_element->FindElement("ixx"))
77 Ixx = prop_element->FindElementValueAsNumberConvertTo("ixx", "SLUG*FT2");
78 if (prop_element->FindElement("diameter"))
79 Diameter = prop_element->FindElementValueAsNumberConvertTo("diameter", "FT");
80 if (prop_element->FindElement("numblades"))
81 numBlades = (int)prop_element->FindElementValueAsNumber("numblades");
82 if (prop_element->FindElement("gearratio"))
83 GearRatio = prop_element->FindElementValueAsNumber("gearratio");
84 if (prop_element->FindElement("minpitch"))
85 MinPitch = prop_element->FindElementValueAsNumber("minpitch");
86 if (prop_element->FindElement("maxpitch"))
87 MaxPitch = prop_element->FindElementValueAsNumber("maxpitch");
88 if (prop_element->FindElement("minrpm"))
89 MinRPM = prop_element->FindElementValueAsNumber("minrpm");
90 if (prop_element->FindElement("maxrpm"))
91 MaxRPM = prop_element->FindElementValueAsNumber("maxrpm");
92 if (prop_element->FindElement("reversepitch"))
93 ReversePitch = prop_element->FindElementValueAsNumber("reversepitch");
94 for (int i=0; i<2; i++) {
95 table_element = prop_element->FindNextElement("table");
96 name = table_element->GetAttributeValue("name");
97 if (name == "C_THRUST") {
98 cThrust = new FGTable(PropertyManager, table_element);
99 } else if (name == "C_POWER") {
100 cPower = new FGTable(PropertyManager, table_element);
102 cerr << "Unknown table type: " << name << " in propeller definition." << endl;
106 local_element = prop_element->GetParent()->FindElement("sense");
108 double Sense = local_element->GetDataAsNumber();
109 SetSense(fabs(Sense)/Sense);
111 local_element = prop_element->GetParent()->FindElement("p_factor");
113 P_Factor = local_element->GetDataAsNumber();
116 cerr << "P-Factor value in config file must be greater than zero" << endl;
118 if (prop_element->FindElement("ct_factor"))
119 SetCtFactor( prop_element->FindElementValueAsNumber("ct_factor") );
120 if (prop_element->FindElement("cp_factor"))
121 SetCpFactor( prop_element->FindElementValueAsNumber("cp_factor") );
125 vTorque.InitMatrix();
126 D4 = Diameter*Diameter*Diameter*Diameter;
129 string property_name, base_property_name;
130 base_property_name = CreateIndexedPropertyName("propulsion/engine", EngineNum);
131 property_name = base_property_name + "/advance-ratio";
132 PropertyManager->Tie( property_name.c_str(), &J );
133 property_name = base_property_name + "/blade-angle";
134 PropertyManager->Tie( property_name.c_str(), &Pitch );
135 property_name = base_property_name + "/thrust-coefficient";
136 PropertyManager->Tie( property_name.c_str(), this, &FGPropeller::GetThrustCoefficient );
137 property_name = base_property_name + "/propeller-rpm";
138 PropertyManager->Tie( property_name.c_str(), this, &FGPropeller::GetRPM );
143 //%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
145 FGPropeller::~FGPropeller()
153 //%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
155 // We must be getting the aerodynamic velocity here, NOT the inertial velocity.
156 // We need the velocity with respect to the wind.
158 // Note that PowerAvailable is the excess power available after the drag of the
159 // propeller has been subtracted. At equilibrium, PowerAvailable will be zero -
160 // indicating that the propeller will not accelerate or decelerate.
161 // Remembering that Torque * omega = Power, we can derive the torque on the
162 // propeller and its acceleration to give a new RPM. The current RPM will be
163 // used to calculate thrust.
165 // Because RPM could be zero, we need to be creative about what RPM is stated as.
167 double FGPropeller::Calculate(double PowerAvailable)
169 double omega, alpha, beta;
171 double Vel = fdmex->GetAuxiliary()->GetAeroUVW(eU);
172 double rho = fdmex->GetAtmosphere()->GetDensity();
173 double RPS = RPM/60.0;
175 if (RPS > 0.00) J = Vel / (Diameter * RPS); // Calculate J normally
176 else J = 1000.0; // Set J to a high number
178 if (MaxPitch == MinPitch) ThrustCoeff = cThrust->GetValue(J);
179 else ThrustCoeff = cThrust->GetValue(J, Pitch);
180 ThrustCoeff *= CtFactor;
182 if (P_Factor > 0.0001) {
183 alpha = fdmex->GetAuxiliary()->Getalpha();
184 beta = fdmex->GetAuxiliary()->Getbeta();
185 SetActingLocationY( GetLocationY() + P_Factor*alpha*Sense);
186 SetActingLocationZ( GetLocationZ() + P_Factor*beta*Sense);
189 Thrust = ThrustCoeff*RPS*RPS*D4*rho;
190 omega = RPS*2.0*M_PI;
194 // The Ixx value and rotation speed given below are for rotation about the
195 // natural axis of the engine. The transform takes place in the base class
196 // FGForce::GetBodyForces() function.
198 vH(eX) = Ixx*omega*Sense;
202 if (omega > 0.0) ExcessTorque = GearRatio * PowerAvailable / omega;
203 else ExcessTorque = GearRatio * PowerAvailable / 1.0;
205 RPM = (RPS + ((ExcessTorque / Ixx) / (2.0 * M_PI)) * deltaT) * 60.0;
207 if (RPM < 1.0) RPM = 0; // Engine friction stops rotation arbitrarily at 1 RPM.
209 // Transform Torque and momentum first, as PQR is used in this
210 // equation and cannot be transformed itself.
211 vMn = fdmex->GetPropagate()->GetPQR()*(Transform()*vH) + Transform()*vTorque;
213 return Thrust; // return thrust in pounds
216 //%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
218 double FGPropeller::GetPowerRequired(void)
221 double rho = fdmex->GetAtmosphere()->GetDensity();
222 double RPS = RPM / 60.0;
224 if (RPS != 0) J = fdmex->GetAuxiliary()->GetAeroUVW(eU) / (Diameter * RPS);
225 else J = 1000.0; // Set J to a high number
227 if (MaxPitch == MinPitch) { // Fixed pitch prop
229 cPReq = cPower->GetValue(J);
230 } else { // Variable pitch prop
232 if (MaxRPM != MinRPM) { // fixed-speed prop
234 // do normal calculation when propeller is neither feathered nor reversed
238 double rpmReq = MinRPM + (MaxRPM - MinRPM) * Advance;
239 double dRPM = rpmReq - RPM;
240 // The pitch of a variable propeller cannot be changed when the RPMs are
241 // too low - the oil pump does not work.
242 if (RPM > 200) Pitch -= dRPM * deltaT;
243 if (Pitch < MinPitch) Pitch = MinPitch;
244 else if (Pitch > MaxPitch) Pitch = MaxPitch;
246 } else { // Reversed propeller
248 // when reversed calculate propeller pitch depending on throttle lever position
249 // (beta range for taxing full reverse for braking)
250 double PitchReq = MinPitch - ( MinPitch - ReversePitch ) * Reverse_coef;
251 // The pitch of a variable propeller cannot be changed when the RPMs are
252 // too low - the oil pump does not work.
253 if (RPM > 200) Pitch += (PitchReq - Pitch) / 200;
255 Pitch += (MaxRPM - RPM) / 50;
256 if (Pitch < ReversePitch) Pitch = ReversePitch;
257 else if (Pitch > MaxPitch) Pitch = MaxPitch;
261 } else { // Feathered propeller
262 // ToDo: Make feathered and reverse settings done via FGKinemat
263 Pitch += (MaxPitch - Pitch) / 300; // just a guess (about 5 sec to fully feathered)
266 } else { // Variable Speed Prop
267 Pitch = MinPitch + (MaxPitch - MinPitch) * Advance;
269 cPReq = cPower->GetValue(J, Pitch);
274 PowerRequired = cPReq*RPS*RPS*RPS*D5*rho;
275 vTorque(eX) = -Sense*PowerRequired / (RPS*2.0*M_PI);
281 return PowerRequired;
284 //%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
286 FGColumnVector3 FGPropeller::GetPFactor()
288 double px=0.0, py, pz;
290 py = Thrust * Sense * (GetActingLocationY() - GetLocationY()) / 12.0;
291 pz = Thrust * Sense * (GetActingLocationZ() - GetLocationZ()) / 12.0;
293 return FGColumnVector3(px, py, pz);
296 //%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
298 string FGPropeller::GetThrusterLabels(int id, string delimeter)
300 std::ostringstream buf;
302 buf << Name << " Torque (engine " << id << ")" << delimeter
303 << Name << " PFactor Pitch (engine " << id << ")" << delimeter
304 << Name << " PFactor Yaw (engine " << id << ")" << delimeter
305 << Name << " Thrust (engine " << id << " in lbs)" << delimeter;
307 buf << Name << " Pitch (engine " << id << ")" << delimeter;
308 buf << Name << " RPM (engine " << id << ")";
313 //%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
315 string FGPropeller::GetThrusterValues(int id, string delimeter)
317 std::ostringstream buf;
319 FGColumnVector3 vPFactor = GetPFactor();
320 buf << vTorque(eX) << delimeter
321 << vPFactor(ePitch) << delimeter
322 << vPFactor(eYaw) << delimeter
323 << Thrust << delimeter;
325 buf << Pitch << delimeter;
331 //%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
332 // The bitmasked value choices are as follows:
333 // unset: In this case (the default) JSBSim would only print
334 // out the normally expected messages, essentially echoing
335 // the config files as they are read. If the environment
336 // variable is not set, debug_lvl is set to 1 internally
337 // 0: This requests JSBSim not to output any messages
339 // 1: This value explicity requests the normal JSBSim
341 // 2: This value asks for a message to be printed out when
342 // a class is instantiated
343 // 4: When this value is set, a message is displayed when a
344 // FGModel object executes its Run() method
345 // 8: When this value is set, various runtime state variables
346 // are printed out periodically
347 // 16: When set various parameters are sanity checked and
348 // a message is printed out when they go out of bounds
350 void FGPropeller::Debug(int from)
352 if (debug_lvl <= 0) return;
354 if (debug_lvl & 1) { // Standard console startup message output
355 if (from == 0) { // Constructor
356 cout << "\n Propeller Name: " << Name << endl;
357 cout << " IXX = " << Ixx << endl;
358 cout << " Diameter = " << Diameter << " ft." << endl;
359 cout << " Number of Blades = " << numBlades << endl;
360 cout << " Gear Ratio = " << GearRatio << endl;
361 cout << " Minimum Pitch = " << MinPitch << endl;
362 cout << " Maximum Pitch = " << MaxPitch << endl;
363 cout << " Minimum RPM = " << MinRPM << endl;
364 cout << " Maximum RPM = " << MaxRPM << endl;
365 // cout << " Thrust Coefficient: " << endl;
367 // cout << " Power Coefficient: " << endl;
371 if (debug_lvl & 2 ) { // Instantiation/Destruction notification
372 if (from == 0) cout << "Instantiated: FGPropeller" << endl;
373 if (from == 1) cout << "Destroyed: FGPropeller" << endl;
375 if (debug_lvl & 4 ) { // Run() method entry print for FGModel-derived objects
377 if (debug_lvl & 8 ) { // Runtime state variables
379 if (debug_lvl & 16) { // Sanity checking
381 if (debug_lvl & 64) {
382 if (from == 0) { // Constructor
383 cout << IdSrc << endl;
384 cout << IdHdr << endl;