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
75 if (prop_element->FindElement("ixx"))
76 Ixx = prop_element->FindElementValueAsNumberConvertTo("ixx", "SLUG*FT2");
77 if (prop_element->FindElement("diameter"))
78 Diameter = prop_element->FindElementValueAsNumberConvertTo("diameter", "FT");
79 if (prop_element->FindElement("numblades"))
80 numBlades = (int)prop_element->FindElementValueAsNumber("numblades");
81 if (prop_element->FindElement("gearratio"))
82 GearRatio = prop_element->FindElementValueAsNumber("gearratio");
83 if (prop_element->FindElement("minpitch"))
84 MinPitch = prop_element->FindElementValueAsNumber("minpitch");
85 if (prop_element->FindElement("maxpitch"))
86 MaxPitch = prop_element->FindElementValueAsNumber("maxpitch");
87 if (prop_element->FindElement("minrpm"))
88 MinRPM = prop_element->FindElementValueAsNumber("minrpm");
89 if (prop_element->FindElement("maxrpm"))
90 MaxRPM = prop_element->FindElementValueAsNumber("maxrpm");
91 if (prop_element->FindElement("reversepitch"))
92 ReversePitch = prop_element->FindElementValueAsNumber("reversepitch");
93 for (int i=0; i<2; i++) {
94 table_element = prop_element->FindNextElement("table");
95 name = table_element->GetAttributeValue("name");
96 if (name == "C_THRUST") {
97 cThrust = new FGTable(PropertyManager, table_element);
98 } else if (name == "C_POWER") {
99 cPower = new FGTable(PropertyManager, table_element);
101 cerr << "Unknown table type: " << name << " in propeller definition." << endl;
105 local_element = prop_element->GetParent()->FindElement("sense");
107 double Sense = local_element->GetDataAsNumber();
108 SetSense(fabs(Sense)/Sense);
110 local_element = prop_element->GetParent()->FindElement("p_factor");
112 P_Factor = local_element->GetDataAsNumber();
115 cerr << "P-Factor value in config file must be greater than zero" << endl;
120 vTorque.InitMatrix();
121 D4 = Diameter*Diameter*Diameter*Diameter;
124 char property_name[80];
125 snprintf(property_name, 80, "propulsion/engine[%d]/advance-ratio", EngineNum);
126 PropertyManager->Tie( property_name, &J );
127 snprintf(property_name, 80, "propulsion/engine[%d]/blade-angle", EngineNum);
128 PropertyManager->Tie( property_name, &Pitch );
129 snprintf(property_name, 80, "propulsion/engine[%d]/thrust-coefficient", EngineNum);
130 PropertyManager->Tie( property_name, this, &FGPropeller::GetThrustCoefficient );
135 //%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
137 FGPropeller::~FGPropeller()
142 char property_name[80];
143 snprintf(property_name, 80, "propulsion/engine[%d]/advance-ratio", EngineNum);
144 PropertyManager->Untie( property_name );
145 snprintf(property_name, 80, "propulsion/engine[%d]/blade-angle", EngineNum);
146 PropertyManager->Untie( property_name );
147 snprintf(property_name, 80, "propulsion/engine[%d]/thrust-coefficient", EngineNum);
148 PropertyManager->Untie( property_name );
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);
181 if (P_Factor > 0.0001) {
182 alpha = fdmex->GetAuxiliary()->Getalpha();
183 beta = fdmex->GetAuxiliary()->Getbeta();
184 SetActingLocationY( GetLocationY() + P_Factor*alpha*Sense);
185 SetActingLocationZ( GetLocationZ() + P_Factor*beta*Sense);
188 Thrust = ThrustCoeff*RPS*RPS*D4*rho;
189 omega = RPS*2.0*M_PI;
193 // The Ixx value and rotation speed given below are for rotation about the
194 // natural axis of the engine. The transform takes place in the base class
195 // FGForce::GetBodyForces() function.
197 vH(eX) = Ixx*omega*Sense;
201 if (omega > 0.0) ExcessTorque = GearRatio * PowerAvailable / omega;
202 else ExcessTorque = GearRatio * PowerAvailable / 1.0;
204 RPM = (RPS + ((ExcessTorque / Ixx) / (2.0 * M_PI)) * deltaT) * 60.0;
206 if (RPM < 1.0) RPM = 0; // Engine friction stops rotation arbitrarily at 1 RPM.
208 vMn = fdmex->GetPropagate()->GetPQR()*vH + vTorque;
210 return Thrust; // return thrust in pounds
213 //%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
215 double FGPropeller::GetPowerRequired(void)
218 double rho = fdmex->GetAtmosphere()->GetDensity();
219 double RPS = RPM / 60.0;
221 if (RPS != 0) J = fdmex->GetAuxiliary()->GetAeroUVW(eU) / (Diameter * RPS);
222 else J = 1000.0; // Set J to a high number
224 if (MaxPitch == MinPitch) { // Fixed pitch prop
226 cPReq = cPower->GetValue(J);
227 } else { // Variable pitch prop
229 if (MaxRPM != MinRPM) { // fixed-speed prop
231 // do normal calculation when propeller is neither feathered nor reversed
235 double rpmReq = MinRPM + (MaxRPM - MinRPM) * Advance;
236 double dRPM = rpmReq - RPM;
237 // The pitch of a variable propeller cannot be changed when the RPMs are
238 // too low - the oil pump does not work.
239 if (RPM > 200) Pitch -= dRPM / 10;
241 if (Pitch < MinPitch) Pitch = MinPitch;
242 else if (Pitch > MaxPitch) Pitch = MaxPitch;
244 } else { // Reversed propeller
246 // when reversed calculate propeller pitch depending on throttle lever position
247 // (beta range for taxing full reverse for braking)
248 double PitchReq = MinPitch - ( MinPitch - ReversePitch ) * Reverse_coef;
249 // The pitch of a variable propeller cannot be changed when the RPMs are
250 // too low - the oil pump does not work.
251 if (RPM > 200) Pitch += (PitchReq - Pitch) / 200;
253 Pitch += (MaxRPM - RPM) / 50;
254 if (Pitch < ReversePitch) Pitch = ReversePitch;
255 else if (Pitch > MaxPitch) Pitch = MaxPitch;
259 } else { // Feathered propeller
260 // ToDo: Make feathered and reverse settings done via FGKinemat
261 Pitch += (MaxPitch - Pitch) / 300; // just a guess (about 5 sec to fully feathered)
264 } else { // Variable Speed Prop
265 Pitch = MinPitch + (MaxPitch - MinPitch) * Advance;
267 cPReq = cPower->GetValue(J, Pitch);
271 PowerRequired = cPReq*RPS*RPS*RPS*D5*rho;
272 vTorque(eX) = -Sense*PowerRequired / (RPS*2.0*M_PI);
278 return PowerRequired;
281 //%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
283 FGColumnVector3 FGPropeller::GetPFactor()
285 double px=0.0, py, pz;
287 py = Thrust * Sense * (GetActingLocationY() - GetLocationY()) / 12.0;
288 pz = Thrust * Sense * (GetActingLocationZ() - GetLocationZ()) / 12.0;
290 return FGColumnVector3(px, py, pz);
293 //%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
295 string FGPropeller::GetThrusterLabels(int id, string delimeter)
297 std::ostringstream buf;
299 buf << Name << " Torque (engine " << id << ")" << delimeter
300 << Name << " PFactor Pitch (engine " << id << ")" << delimeter
301 << Name << " PFactor Yaw (engine " << id << ")" << delimeter
302 << Name << " Thrust (engine " << id << " in lbs)" << delimeter;
304 buf << Name << " Pitch (engine " << id << ")" << delimeter;
305 buf << Name << " RPM (engine " << id << ")";
310 //%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
312 string FGPropeller::GetThrusterValues(int id, string delimeter)
314 std::ostringstream buf;
316 FGColumnVector3 vPFactor = GetPFactor();
317 buf << vTorque(eX) << delimeter
318 << vPFactor(ePitch) << delimeter
319 << vPFactor(eYaw) << delimeter
320 << Thrust << delimeter;
322 buf << Pitch << delimeter;
328 //%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
329 // The bitmasked value choices are as follows:
330 // unset: In this case (the default) JSBSim would only print
331 // out the normally expected messages, essentially echoing
332 // the config files as they are read. If the environment
333 // variable is not set, debug_lvl is set to 1 internally
334 // 0: This requests JSBSim not to output any messages
336 // 1: This value explicity requests the normal JSBSim
338 // 2: This value asks for a message to be printed out when
339 // a class is instantiated
340 // 4: When this value is set, a message is displayed when a
341 // FGModel object executes its Run() method
342 // 8: When this value is set, various runtime state variables
343 // are printed out periodically
344 // 16: When set various parameters are sanity checked and
345 // a message is printed out when they go out of bounds
347 void FGPropeller::Debug(int from)
349 if (debug_lvl <= 0) return;
351 if (debug_lvl & 1) { // Standard console startup message output
352 if (from == 0) { // Constructor
353 cout << "\n Propeller Name: " << Name << endl;
354 cout << " IXX = " << Ixx << endl;
355 cout << " Diameter = " << Diameter << " ft." << endl;
356 cout << " Number of Blades = " << numBlades << endl;
357 cout << " Gear Ratio = " << GearRatio << endl;
358 cout << " Minimum Pitch = " << MinPitch << endl;
359 cout << " Maximum Pitch = " << MaxPitch << endl;
360 cout << " Minimum RPM = " << MinRPM << endl;
361 cout << " Maximum RPM = " << MaxRPM << endl;
362 // cout << " Thrust Coefficient: " << endl;
364 // cout << " Power Coefficient: " << endl;
368 if (debug_lvl & 2 ) { // Instantiation/Destruction notification
369 if (from == 0) cout << "Instantiated: FGPropeller" << endl;
370 if (from == 1) cout << "Destroyed: FGPropeller" << endl;
372 if (debug_lvl & 4 ) { // Run() method entry print for FGModel-derived objects
374 if (debug_lvl & 8 ) { // Runtime state variables
376 if (debug_lvl & 16) { // Sanity checking
378 if (debug_lvl & 64) {
379 if (from == 0) { // Constructor
380 cout << IdSrc << endl;
381 cout << IdHdr << endl;