1 /*%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
3 Module: FGAerodynamics.cpp
6 Purpose: Encapsulates the aerodynamic forces
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 --------------------------------------------------------------------------------
33 04/22/01 JSB Moved code into here from FGAircraft
35 %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
37 %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%*/
39 #include <FGFDMExec.h>
40 #include "FGAerodynamics.h"
41 #include "FGPropagate.h"
42 #include "FGAircraft.h"
43 #include "FGAuxiliary.h"
44 #include "FGMassBalance.h"
45 #include <input_output/FGPropertyManager.h>
49 static const char *IdSrc = "$Id$";
50 static const char *IdHdr = ID_AERODYNAMICS;
52 /*%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
54 %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%*/
57 FGAerodynamics::FGAerodynamics(FGFDMExec* FDMExec) : FGModel(FDMExec)
59 Name = "FGAerodynamics";
69 AxisIdx["NORMAL"] = 2;
77 Coeff = new CoeffArray[6];
79 impending_stall = stall_hyst = 0.0;
80 alphaclmin = alphaclmax = 0.0;
81 alphahystmin = alphahystmax = 0.0;
84 bi2vel = ci2vel = 0.0;
86 vDeltaRP.InitMatrix();
93 //%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
95 FGAerodynamics::~FGAerodynamics()
100 for (j=0; j<Coeff[i].size(); j++)
105 for (i=0; i<variables.size(); i++)
113 //%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
115 bool FGAerodynamics::InitModel(void)
117 if (!FGModel::InitModel()) return false;
119 impending_stall = stall_hyst = 0.0;
120 alphaclmin = alphaclmax = 0.0;
121 alphahystmin = alphahystmax = 0.0;
124 bi2vel = ci2vel = 0.0;
126 vDeltaRP.InitMatrix();
130 //%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
132 bool FGAerodynamics::Run(void)
134 unsigned int axis_ctr, ctr, i;
135 double alpha, twovel;
137 if (FGModel::Run()) return true;
138 if (FDMExec->Holding()) return false; // if paused don't execute
140 // calculate some oft-used quantities for speed
142 twovel = 2*Auxiliary->GetVt();
144 bi2vel = Aircraft->GetWingSpan() / twovel;
145 ci2vel = Aircraft->Getcbar() / twovel;
147 alphaw = Auxiliary->Getalpha() + Aircraft->GetWingIncidence();
148 alpha = Auxiliary->Getalpha();
149 qbar_area = Aircraft->GetWingArea() * Auxiliary->Getqbar();
151 if (alphaclmax != 0) {
152 if (alpha > 0.85*alphaclmax) {
153 impending_stall = 10*(alpha/alphaclmax - 0.85);
159 if (alphahystmax != 0.0 && alphahystmin != 0.0) {
160 if (alpha > alphahystmax) {
162 } else if (alpha < alphahystmin) {
168 vFnative.InitMatrix();
170 // Tell the variable functions to cache their values, so while the aerodynamic
171 // functions are being calculated for each axis, these functions do not get
172 // calculated each time, but instead use the values that have already
173 // been calculated for this frame.
175 for (i=0; i<variables.size(); i++) variables[i]->cacheValue(true);
177 for (axis_ctr = 0; axis_ctr < 3; axis_ctr++) {
178 for (ctr=0; ctr < Coeff[axis_ctr].size(); ctr++) {
179 vFnative(axis_ctr+1) += Coeff[axis_ctr][ctr]->GetValue();
183 // Note that we still need to convert to wind axes here, because it is
184 // used in the L/D calculation, and we still may want to look at Lift
188 case atBodyXYZ: // Forces already in body axes; no manipulation needed
189 vFw = GetTb2w()*vFnative;
192 case atLiftDrag: // Copy forces into wind axes
194 vFw(eDrag)*=-1; vFw(eLift)*=-1;
195 vForces = GetTw2b()*vFw;
197 case atAxialNormal: // Convert native forces into Axial|Normal|Side system
198 vFw = GetTb2w()*vFnative;
199 vFnative(eX)*=-1; vFnative(eZ)*=-1;
203 cerr << endl << " A proper axis type has NOT been selected. Check "
204 << "your aerodynamics definition." << endl;
208 // Calculate aerodynamic reference point shift, if any
209 if (AeroRPShift) vDeltaRP(eX) = AeroRPShift->GetValue()*Aircraft->Getcbar()*12.0;
211 // Calculate lift coefficient squared
212 if ( Auxiliary->Getqbar() > 0) {
213 clsq = vFw(eLift) / (Aircraft->GetWingArea()*Auxiliary->Getqbar());
217 // Calculate lift Lift over Drag
218 if ( fabs(vFw(eDrag)) > 0.0) lod = fabs( vFw(eLift) / vFw(eDrag) );
220 vDXYZcg = MassBalance->StructuralToBody(Aircraft->GetXYZrp() + vDeltaRP);
222 vMoments = vDXYZcg*vForces; // M = r X F
224 for (axis_ctr = 0; axis_ctr < 3; axis_ctr++) {
225 for (ctr = 0; ctr < Coeff[axis_ctr+3].size(); ctr++) {
226 vMoments(axis_ctr+1) += Coeff[axis_ctr+3][ctr]->GetValue();
233 //%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
235 // From Stevens and Lewis, "Aircraft Control and Simulation", 3rd Ed., the
236 // transformation from body to wind axes is defined (where "a" is alpha and "B"
239 // cos(a)*cos(B) sin(B) sin(a)*cos(B)
240 // -cos(a)*sin(B) cos(B) -sin(a)*sin(B)
243 // The transform from wind to body axes is then,
245 // cos(a)*cos(B) -cos(a)*sin(B) -sin(a)
247 // sin(a)*cos(B) -sin(a)*sin(B) cos(a)
249 FGMatrix33& FGAerodynamics::GetTw2b(void)
251 double ca, cb, sa, sb;
253 double alpha = Auxiliary->Getalpha();
254 double beta = Auxiliary->Getbeta();
274 //%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
276 FGMatrix33& FGAerodynamics::GetTb2w(void)
279 double ca, cb, sa, sb;
281 alpha = Auxiliary->Getalpha();
282 beta = Auxiliary->Getbeta();
302 //%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
304 bool FGAerodynamics::Load(Element *element)
306 string parameter, axis, scratch;
307 string scratch_unit="";
308 string fname="", file="";
309 Element *temp_element, *axis_element, *function_element;
311 string separator = "/";
313 fname = element->GetAttributeValue("file");
314 if (!fname.empty()) {
315 file = FDMExec->GetFullAircraftPath() + separator + fname;
316 document = LoadXMLDocument(file);
321 DetermineAxisSystem(); // Detemine if Lift/Side/Drag, etc. is used.
325 if (temp_element = document->FindElement("alphalimits")) {
326 scratch_unit = temp_element->GetAttributeValue("unit");
327 if (scratch_unit.empty()) scratch_unit = "RAD";
328 alphaclmin = temp_element->FindElementValueAsNumberConvertFromTo("min", scratch_unit, "RAD");
329 alphaclmax = temp_element->FindElementValueAsNumberConvertFromTo("max", scratch_unit, "RAD");
332 if (temp_element = document->FindElement("hysteresis_limits")) {
333 scratch_unit = temp_element->GetAttributeValue("unit");
334 if (scratch_unit.empty()) scratch_unit = "RAD";
335 alphahystmin = temp_element->FindElementValueAsNumberConvertFromTo("min", scratch_unit, "RAD");
336 alphahystmax = temp_element->FindElementValueAsNumberConvertFromTo("max", scratch_unit, "RAD");
339 if (temp_element = document->FindElement("aero_ref_pt_shift_x")) {
340 function_element = temp_element->FindElement("function");
341 AeroRPShift = new FGFunction(PropertyManager, function_element);
344 function_element = document->FindElement("function");
345 while (function_element) {
346 variables.push_back( new FGFunction(PropertyManager, function_element) );
347 function_element = document->FindNextElement("function");
350 axis_element = document->FindElement("axis");
351 while (axis_element) {
353 axis = axis_element->GetAttributeValue("name");
354 function_element = axis_element->FindElement("function");
355 while (function_element) {
356 ca.push_back( new FGFunction(PropertyManager, function_element) );
357 function_element = axis_element->FindNextElement("function");
359 Coeff[AxisIdx[axis]] = ca;
360 axis_element = document->FindNextElement("axis");
366 //%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
368 // This private class function checks to verify consistency in the choice of
369 // aerodynamic axes used in the config file. One set of LIFT|DRAG|SIDE, or
370 // X|Y|Z, or AXIAL|NORMAL|SIDE must be chosen; mixed system axes are not allowed.
371 // Note that if the "SIDE" axis specifier is entered first in a config file,
372 // a warning message will be given IF the AXIAL|NORMAL specifiers are also given.
373 // This is OK, and the warning is due to the SIDE specifier used for both
374 // the Lift/Drag and Axial/Normal axis systems.
376 void FGAerodynamics::DetermineAxisSystem()
378 Element* axis_element = document->FindElement("axis");
380 while (axis_element) {
381 axis = axis_element->GetAttributeValue("name");
382 if (axis == "LIFT" || axis == "DRAG" || axis == "SIDE") {
383 if (axisType == atNone) axisType = atLiftDrag;
384 else if (axisType != atLiftDrag) {
385 cerr << endl << " Mixed aerodynamic axis systems have been used in the"
386 << " aircraft config file." << endl;
388 } else if (axis == "AXIAL" || axis == "NORMAL") {
389 if (axisType == atNone) axisType = atAxialNormal;
390 else if (axisType != atAxialNormal) {
391 cerr << endl << " Mixed aerodynamic axis systems have been used in the"
392 << " aircraft config file." << endl;
394 } else if (axis == "X" || axis == "Y" || axis == "Z") {
395 if (axisType == atNone) axisType = atBodyXYZ;
396 else if (axisType != atBodyXYZ) {
397 cerr << endl << " Mixed aerodynamic axis systems have been used in the"
398 << " aircraft config file." << endl;
400 } else if (axis != "ROLL" && axis != "PITCH" && axis != "YAW") { // error
401 cerr << endl << " An unknown axis type, " << axis << " has been specified"
402 << " in the aircraft configuration file." << endl;
405 axis_element = document->FindNextElement("axis");
407 if (axisType == atNone) {
408 axisType = atLiftDrag;
409 cerr << endl << " The aerodynamic axis system has been set by default"
410 << " to the Lift/Side/Drag system." << endl;
414 //%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
416 string FGAerodynamics::GetCoefficientStrings(string delimeter)
418 string CoeffStrings = "";
419 bool firstime = true;
420 unsigned int axis, sd;
422 for (sd = 0; sd < variables.size(); sd++) {
426 CoeffStrings += delimeter;
428 CoeffStrings += variables[sd]->GetName();
431 for (axis = 0; axis < 6; axis++) {
432 for (sd = 0; sd < Coeff[axis].size(); sd++) {
436 CoeffStrings += delimeter;
438 CoeffStrings += Coeff[axis][sd]->GetName();
444 //%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
446 string FGAerodynamics::GetCoefficientValues(string delimeter)
448 string SDValues = "";
449 bool firstime = true;
452 for (sd = 0; sd < variables.size(); sd++) {
456 SDValues += delimeter;
458 SDValues += variables[sd]->GetValueAsString();
461 for (unsigned int axis = 0; axis < 6; axis++) {
462 for (unsigned int sd = 0; sd < Coeff[axis].size(); sd++) {
466 SDValues += delimeter;
468 SDValues += Coeff[axis][sd]->GetValueAsString();
475 //%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
477 void FGAerodynamics::bind(void)
479 typedef double (FGAerodynamics::*PMF)(int) const;
481 PropertyManager->Tie("forces/fbx-aero-lbs", this,1,
482 (PMF)&FGAerodynamics::GetForces);
483 PropertyManager->Tie("forces/fby-aero-lbs", this,2,
484 (PMF)&FGAerodynamics::GetForces);
485 PropertyManager->Tie("forces/fbz-aero-lbs", this,3,
486 (PMF)&FGAerodynamics::GetForces);
487 PropertyManager->Tie("moments/l-aero-lbsft", this,1,
488 (PMF)&FGAerodynamics::GetMoments);
489 PropertyManager->Tie("moments/m-aero-lbsft", this,2,
490 (PMF)&FGAerodynamics::GetMoments);
491 PropertyManager->Tie("moments/n-aero-lbsft", this,3,
492 (PMF)&FGAerodynamics::GetMoments);
493 PropertyManager->Tie("forces/fwx-aero-lbs", this,1,
494 (PMF)&FGAerodynamics::GetvFw);
495 PropertyManager->Tie("forces/fwy-aero-lbs", this,2,
496 (PMF)&FGAerodynamics::GetvFw);
497 PropertyManager->Tie("forces/fwz-aero-lbs", this,3,
498 (PMF)&FGAerodynamics::GetvFw);
499 PropertyManager->Tie("forces/lod-norm", this,
500 &FGAerodynamics::GetLoD);
501 PropertyManager->Tie("aero/cl-squared", this,
502 &FGAerodynamics::GetClSquared);
503 PropertyManager->Tie("aero/qbar-area", &qbar_area);
504 PropertyManager->Tie("aero/alpha-max-rad", this,
505 &FGAerodynamics::GetAlphaCLMax,
506 &FGAerodynamics::SetAlphaCLMax,
508 PropertyManager->Tie("aero/alpha-min-rad", this,
509 &FGAerodynamics::GetAlphaCLMin,
510 &FGAerodynamics::SetAlphaCLMin,
512 PropertyManager->Tie("aero/bi2vel", this,
513 &FGAerodynamics::GetBI2Vel);
514 PropertyManager->Tie("aero/ci2vel", this,
515 &FGAerodynamics::GetCI2Vel);
516 PropertyManager->Tie("aero/alpha-wing-rad", this,
517 &FGAerodynamics::GetAlphaW);
518 PropertyManager->Tie("systems/stall-warn-norm", this,
519 &FGAerodynamics::GetStallWarn);
520 PropertyManager->Tie("aero/stall-hyst-norm", this,
521 &FGAerodynamics::GetHysteresisParm);
524 //%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
525 // The bitmasked value choices are as follows:
526 // unset: In this case (the default) JSBSim would only print
527 // out the normally expected messages, essentially echoing
528 // the config files as they are read. If the environment
529 // variable is not set, debug_lvl is set to 1 internally
530 // 0: This requests JSBSim not to output any messages
532 // 1: This value explicity requests the normal JSBSim
534 // 2: This value asks for a message to be printed out when
535 // a class is instantiated
536 // 4: When this value is set, a message is displayed when a
537 // FGModel object executes its Run() method
538 // 8: When this value is set, various runtime state variables
539 // are printed out periodically
540 // 16: When set various parameters are sanity checked and
541 // a message is printed out when they go out of bounds
543 void FGAerodynamics::Debug(int from)
545 if (debug_lvl <= 0) return;
547 if (debug_lvl & 1) { // Standard console startup message output
548 if (from == 2) { // Loader
551 cout << endl << " Aerodynamics (Lift|Side|Drag axes):" << endl << endl;
553 case (atAxialNormal):
554 cout << endl << " Aerodynamics (Axial|Side|Normal axes):" << endl << endl;
557 cout << endl << " Aerodynamics (X|Y|Z axes):" << endl << endl;
562 if (debug_lvl & 2 ) { // Instantiation/Destruction notification
563 if (from == 0) cout << "Instantiated: FGAerodynamics" << endl;
564 if (from == 1) cout << "Destroyed: FGAerodynamics" << endl;
566 if (debug_lvl & 4 ) { // Run() method entry print for FGModel-derived objects
568 if (debug_lvl & 8 ) { // Runtime state variables
570 if (debug_lvl & 16) { // Sanity checking
572 if (debug_lvl & 64) {
573 if (from == 0) { // Constructor
574 cout << IdSrc << endl;
575 cout << IdHdr << endl;
580 } // namespace JSBSim