1 /*%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
7 Purpose: Encapsulates the landing gear elements
10 ------------- Copyright (C) 1999 Jon S. Berndt (jsb@hal-pc.org) -------------
12 This program is free software; you can redistribute it and/or modify it under
13 the terms of the GNU Lesser General Public License as published by the Free Software
14 Foundation; either version 2 of the License, or (at your option) any later
17 This program is distributed in the hope that it will be useful, but WITHOUT
18 ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or FITNESS
19 FOR A PARTICULAR PURPOSE. See the GNU Lesser General Public License for more
22 You should have received a copy of the GNU Lesser General Public License along with
23 this program; if not, write to the Free Software Foundation, Inc., 59 Temple
24 Place - Suite 330, Boston, MA 02111-1307, USA.
26 Further information about the GNU Lesser General Public License can also be found on
27 the world wide web at http://www.gnu.org.
29 FUNCTIONAL DESCRIPTION
30 --------------------------------------------------------------------------------
33 --------------------------------------------------------------------------------
35 01/30/01 NHP Extended gear model to properly simulate steering and braking
37 /%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
39 %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%*/
45 /*%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
47 %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%*/
49 /*%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
51 %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%*/
53 static const char *IdSrc = "$Id$";
54 static const char *IdHdr = ID_LGEAR;
56 /*%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
58 %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%*/
60 FGLGear::FGLGear(Element* el, FGFDMExec* fdmex, int number) :
64 Element *force_table=0;
66 Element *dampCoeffRebound=0;
69 kSpring = bDamp = bDampRebound = dynamicFCoeff = staticFCoeff = rollingFCoeff = maxSteerAngle = 0;
70 sSteerType = sBrakeGroup = sSteerType = "";
73 eDampTypeRebound = dtLinear;
75 name = el->GetAttributeValue("name");
76 sContactType = el->GetAttributeValue("type");
77 if (sContactType == "BOGEY") {
78 eContactType = ctBOGEY;
79 } else if (sContactType == "STRUCTURE") {
80 eContactType = ctSTRUCTURE;
82 eContactType = ctUNKNOWN;
85 if (el->FindElement("spring_coeff"))
86 kSpring = el->FindElementValueAsNumberConvertTo("spring_coeff", "LBS/FT");
87 if (el->FindElement("damping_coeff")) {
88 dampCoeff = el->FindElement("damping_coeff");
89 if (dampCoeff->GetAttributeValue("type") == "SQUARE") {
91 bDamp = el->FindElementValueAsNumberConvertTo("damping_coeff", "LBS/FT2/SEC2");
93 bDamp = el->FindElementValueAsNumberConvertTo("damping_coeff", "LBS/FT/SEC");
97 if (el->FindElement("damping_coeff_rebound")) {
98 dampCoeffRebound = el->FindElement("damping_coeff_rebound");
99 if (dampCoeffRebound->GetAttributeValue("type") == "SQUARE") {
100 eDampTypeRebound = dtSquare;
101 bDampRebound = el->FindElementValueAsNumberConvertTo("damping_coeff_rebound", "LBS/FT2/SEC2");
103 bDampRebound = el->FindElementValueAsNumberConvertTo("damping_coeff_rebound", "LBS/FT/SEC");
106 bDampRebound = bDamp;
107 eDampTypeRebound = eDampType;
110 if (el->FindElement("dynamic_friction"))
111 dynamicFCoeff = el->FindElementValueAsNumber("dynamic_friction");
112 if (el->FindElement("static_friction"))
113 staticFCoeff = el->FindElementValueAsNumber("static_friction");
114 if (el->FindElement("rolling_friction"))
115 rollingFCoeff = el->FindElementValueAsNumber("rolling_friction");
116 if (el->FindElement("max_steer"))
117 maxSteerAngle = el->FindElementValueAsNumberConvertTo("max_steer", "DEG");
118 if (el->FindElement("retractable"))
119 isRetractable = ((unsigned int)el->FindElementValueAsNumber("retractable"))>0.0?true:false;
122 force_table = el->FindElement("table");
123 while (force_table) {
124 force_type = force_table->GetAttributeValue("type");
125 if (force_type == "CORNERING_COEFF") {
126 ForceY_Table = new FGTable(Exec->GetPropertyManager(), force_table);
128 cerr << "Undefined force table for " << name << " contact point" << endl;
130 force_table = el->FindNextElement("table");
133 sBrakeGroup = el->FindElementValue("brake_group");
135 if (maxSteerAngle == 360) sSteerType = "CASTERED";
136 else if (maxSteerAngle == 0.0) sSteerType = "FIXED";
137 else sSteerType = "STEERABLE";
139 Element* element = el->FindElement("location");
140 if (element) vXYZ = element->FindElementTripletConvertTo("IN");
141 else {cerr << "No location given for contact " << name << endl; exit(-1);}
143 if (sBrakeGroup == "LEFT" ) eBrakeGrp = bgLeft;
144 else if (sBrakeGroup == "RIGHT" ) eBrakeGrp = bgRight;
145 else if (sBrakeGroup == "CENTER") eBrakeGrp = bgCenter;
146 else if (sBrakeGroup == "NOSE" ) eBrakeGrp = bgNose;
147 else if (sBrakeGroup == "TAIL" ) eBrakeGrp = bgTail;
148 else if (sBrakeGroup == "NONE" ) eBrakeGrp = bgNone;
149 else if (sBrakeGroup.empty() ) {eBrakeGrp = bgNone;
150 sBrakeGroup = "NONE (defaulted)";}
152 cerr << "Improper braking group specification in config file: "
153 << sBrakeGroup << " is undefined." << endl;
156 if (sSteerType == "STEERABLE") eSteerType = stSteer;
157 else if (sSteerType == "FIXED" ) eSteerType = stFixed;
158 else if (sSteerType == "CASTERED" ) eSteerType = stCaster;
159 else if (sSteerType.empty() ) {eSteerType = stFixed;
160 sSteerType = "FIXED (defaulted)";}
162 cerr << "Improper steering type specification in config file: "
163 << sSteerType << " is undefined." << endl;
166 RFRV = 0.7; // Rolling force relaxation velocity, default value
167 SFRV = 0.7; // Side force relaxation velocity, default value
169 Element* relax_vel = el->FindElement("relaxation_velocity");
171 if (relax_vel->FindElement("rolling")) {
172 RFRV = relax_vel->FindElementValueAsNumberConvertTo("rolling", "FT/SEC");
174 if (relax_vel->FindElement("side")) {
175 SFRV = relax_vel->FindElementValueAsNumberConvertTo("side", "FT/SEC");
179 State = Exec->GetState();
180 LongForceLagFilterCoeff = 1/State->Getdt(); // default longitudinal force filter coefficient
181 LatForceLagFilterCoeff = 1/State->Getdt(); // default lateral force filter coefficient
183 Element* force_lag_filter_elem = el->FindElement("force_lag_filter");
184 if (force_lag_filter_elem) {
185 if (force_lag_filter_elem->FindElement("rolling")) {
186 LongForceLagFilterCoeff = force_lag_filter_elem->FindElementValueAsNumber("rolling");
188 if (force_lag_filter_elem->FindElement("side")) {
189 LatForceLagFilterCoeff = force_lag_filter_elem->FindElementValueAsNumber("side");
193 WheelSlipLagFilterCoeff = 1/State->Getdt();
195 Element *wheel_slip_angle_lag_elem = el->FindElement("wheel_slip_filter");
196 if (wheel_slip_angle_lag_elem) {
197 WheelSlipLagFilterCoeff = wheel_slip_angle_lag_elem->GetDataAsNumber();
203 useFCSGearPos = false;
206 // Add some AI here to determine if gear is located properly according to its
207 // brake group type ??
209 State = Exec->GetState();
210 Aircraft = Exec->GetAircraft();
211 Propagate = Exec->GetPropagate();
212 Auxiliary = Exec->GetAuxiliary();
213 FCS = Exec->GetFCS();
214 MassBalance = Exec->GetMassBalance();
216 WOW = lastWOW = false;
218 FirstContact = false;
219 StartedGroundRun = false;
220 TakeoffReported = LandingReported = false;
221 LandingDistanceTraveled = TakeoffDistanceTraveled = TakeoffDistanceTraveled50ft = 0.0;
222 MaximumStrutForce = MaximumStrutTravel = 0.0;
223 SideForce = RollingForce = 0.0;
224 SinkRate = GroundSpeed = 0.0;
226 vWhlBodyVec = MassBalance->StructuralToBody(vXYZ);
228 vLocalGear = Propagate->GetTb2l() * vWhlBodyVec;
230 compressLength = 0.0;
236 TirePressureNorm = 1.0;
250 //%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
252 FGLGear::FGLGear(const FGLGear& lgear)
254 GearNumber = lgear.GearNumber;
256 Aircraft = lgear.Aircraft;
257 Propagate = lgear.Propagate;
258 Auxiliary = lgear.Auxiliary;
261 MassBalance = lgear.MassBalance;
264 vMoment = lgear.vMoment;
265 vWhlBodyVec = lgear.vWhlBodyVec;
266 vLocalGear = lgear.vLocalGear;
269 lastWOW = lgear.lastWOW;
270 ReportEnable = lgear.ReportEnable;
271 FirstContact = lgear.FirstContact;
272 StartedGroundRun = lgear.StartedGroundRun;
273 LandingDistanceTraveled = lgear.LandingDistanceTraveled;
274 TakeoffDistanceTraveled = lgear.TakeoffDistanceTraveled;
275 TakeoffDistanceTraveled50ft = lgear.TakeoffDistanceTraveled50ft;
276 MaximumStrutForce = lgear.MaximumStrutForce;
277 MaximumStrutTravel = lgear.MaximumStrutTravel;
278 SideForce = lgear.SideForce;
279 RollingForce = lgear.RollingForce;
281 kSpring = lgear.kSpring;
283 bDampRebound = lgear.bDampRebound;
284 compressLength = lgear.compressLength;
285 compressSpeed = lgear.compressSpeed;
286 staticFCoeff = lgear.staticFCoeff;
287 dynamicFCoeff = lgear.dynamicFCoeff;
288 rollingFCoeff = lgear.rollingFCoeff;
289 brakePct = lgear.brakePct;
290 maxCompLen = lgear.maxCompLen;
291 SinkRate = lgear.SinkRate;
292 GroundSpeed = lgear.GroundSpeed;
293 LandingReported = lgear.LandingReported;
294 TakeoffReported = lgear.TakeoffReported;
296 sSteerType = lgear.sSteerType;
297 sRetractable = lgear.sRetractable;
298 sContactType = lgear.sContactType;
299 eContactType = lgear.eContactType;
300 sBrakeGroup = lgear.sBrakeGroup;
301 eSteerType = lgear.eSteerType;
302 eBrakeGrp = lgear.eBrakeGrp;
303 maxSteerAngle = lgear.maxSteerAngle;
304 isRetractable = lgear.isRetractable;
305 GearUp = lgear.GearUp;
306 GearDown = lgear.GearDown;
307 GearPos = lgear.GearPos;
308 useFCSGearPos = lgear.useFCSGearPos;
309 WheelSlip = lgear.WheelSlip;
310 TirePressureNorm = lgear.TirePressureNorm;
311 Servicable = lgear.Servicable;
312 ForceY_Table = lgear.ForceY_Table;
313 CosWheel = lgear.CosWheel;
314 SinWheel = lgear.SinWheel;
315 prevOut = lgear.prevOut;
316 prevIn = lgear.prevIn;
317 prevSlipIn = lgear.prevSlipIn;
318 prevSlipOut = lgear.prevSlipOut;
321 LongForceLagFilterCoeff = lgear.LongForceLagFilterCoeff;
322 LatForceLagFilterCoeff = lgear.LatForceLagFilterCoeff;
323 WheelSlipLagFilterCoeff = lgear.WheelSlipLagFilterCoeff;
326 //%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
333 //%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
335 FGColumnVector3& FGLGear::Force(void)
337 double t = Exec->GetState()->Getsim_time();
338 dT = State->Getdt()*Exec->GetGroundReactions()->GetRate();
341 vMoment.InitMatrix();
343 if (isRetractable) ComputeRetractionState();
347 vWhlBodyVec = MassBalance->StructuralToBody(vXYZ); // Get wheel in body frame
348 vLocalGear = Propagate->GetTb2l() * vWhlBodyVec; // Get local frame wheel location
350 gearLoc = Propagate->GetLocation().LocalToLocation(vLocalGear);
351 compressLength = -Exec->GetGroundCallback()->GetAGLevel(t, gearLoc, contact, normal, cvel);
353 // The compression length is measured in the Z-axis, only, at this time.
355 if (compressLength > 0.00) {
359 // [The next equation should really use the vector to the contact patch of
360 // the tire including the strut compression and not the original vWhlBodyVec.]
362 vWhlVelVec = Propagate->GetTb2l() * (Propagate->GetPQR() * vWhlBodyVec);
363 vWhlVelVec += Propagate->GetVel() - cvel;
364 compressSpeed = vWhlVelVec(eZ);
366 InitializeReporting();
367 ComputeBrakeForceCoefficient();
368 ComputeSteeringAngle();
370 ComputeSideForceCoefficient();
371 ComputeVerticalStrutForce();
373 // Compute the forces in the wheel ground plane.
375 double sign = RollingWhlVel>0?1.0:(RollingWhlVel<0?-1.0:0.0);
376 RollingForce = ((1.0 - TirePressureNorm) * 30 + vLocalForce(eZ) * BrakeFCoeff) * sign;
377 SideForce = vLocalForce(eZ) * FCoeff;
379 // Transform these forces back to the local reference frame.
381 vLocalForce(eX) = RollingForce*CosWheel - SideForce*SinWheel;
382 vLocalForce(eY) = SideForce*CosWheel + RollingForce*SinWheel;
384 // Transform the forces back to the body frame and compute the moment.
386 vForce = Propagate->GetTl2b() * vLocalForce;
388 // Lag and attenuate the XY-plane forces dependent on velocity
390 double ca, cb, denom;
391 FGColumnVector3 Output;
393 // This code implements a lag filter, C/(s + C) where
394 // "C" is the filter coefficient. When "C" is chosen at the
395 // frame rate (in Hz), the jittering is significantly reduced. This is because
396 // the jitter is present *at* the execution rate.
397 // If a coefficient is set to something equal to or less than zero, the filter
400 if (LongForceLagFilterCoeff > 0) {
401 denom = 2.00 + dT*LongForceLagFilterCoeff;
402 ca = dT*LongForceLagFilterCoeff / denom;
403 cb = (2.00 - dT*LongForceLagFilterCoeff) / denom;
404 Output(eX) = vForce(eX) * ca + prevIn(eX) * ca + prevOut(eX) * cb;
405 vForce(eX) = Output(eX);
407 if (LatForceLagFilterCoeff > 0) {
408 denom = 2.00 + dT*LatForceLagFilterCoeff;
409 ca = dT*LatForceLagFilterCoeff / denom;
410 cb = (2.00 - dT*LatForceLagFilterCoeff) / denom;
411 Output(eY) = vForce(eY) * ca + prevIn(eY) * ca + prevOut(eY) * cb;
412 vForce(eY) = Output(eY);
418 if ((fabs(RollingWhlVel) <= RFRV) && RFRV > 0) vForce(eX) *= fabs(RollingWhlVel)/RFRV;
419 if ((fabs(SideWhlVel) <= SFRV) && SFRV > 0) vForce(eY) *= fabs(SideWhlVel)/SFRV;
421 // End section for attentuating gear jitter
423 vMoment = vWhlBodyVec * vForce;
425 } else { // Gear is NOT compressed
428 compressLength = 0.0;
430 // Return to neutral position between 1.0 and 0.8 gear pos.
431 SteerAngle *= max(GetGearUnitPos()-0.8, 0.0)/0.2;
437 ReportTakeoffOrLanding();
439 // Require both WOW and LastWOW to be true before checking crash conditions
440 // to allow the WOW flag to be used in terminating a scripted run.
441 if (WOW && lastWOW) CrashDetect();
448 //%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
450 void FGLGear::ComputeRetractionState(void)
452 double gearPos = GetGearUnitPos();
453 if (gearPos < 0.01) {
457 } else if (gearPos > 0.99) {
466 //%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
468 void FGLGear::ComputeSlipAngle(void)
470 // Transform the wheel velocities from the local axis system to the wheel axis system.
471 RollingWhlVel = vWhlVelVec(eX)*CosWheel + vWhlVelVec(eY)*SinWheel;
472 SideWhlVel = vWhlVelVec(eY)*CosWheel - vWhlVelVec(eX)*SinWheel;
474 // Calculate tire slip angle.
475 WheelSlip = atan2(SideWhlVel, fabs(RollingWhlVel))*radtodeg;
477 // Filter the wheel slip angle
479 double SlipOutput, ca, cb, denom;
481 if (WheelSlipLagFilterCoeff > 0) {
482 denom = 2.00 + dT*WheelSlipLagFilterCoeff;
483 ca = dT*WheelSlipLagFilterCoeff / denom;
484 cb = (2.00 - dT*WheelSlipLagFilterCoeff) / denom;
486 SlipOutput = ca * (WheelSlip + prevSlipIn) + cb * prevSlipOut;
488 prevSlipIn = WheelSlip;
489 WheelSlip = prevSlipOut = SlipOutput;
493 //%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
494 // Compute the steering angle in any case.
495 // This will also make sure that animations will look right.
497 void FGLGear::ComputeSteeringAngle(void)
499 double casterLocalFrameAngleRad = 0.0;
500 double casterAngle = 0.0;
502 switch (eSteerType) {
504 SteerAngle = degtorad * FCS->GetSteerPosDeg(GearNumber);
510 // This is not correct for castering gear. Should make steer angle parallel
511 // to the actual velocity vector of the wheel, given aircraft velocity vector
514 casterLocalFrameAngleRad = acos(vWhlVelVec(eX)/vWhlVelVec.Magnitude());
515 casterAngle = casterLocalFrameAngleRad - Propagate->GetEuler(ePsi);
518 cerr << "Improper steering type membership detected for this gear." << endl;
522 SinWheel = sin(Propagate->GetEuler(ePsi) + SteerAngle);
523 CosWheel = cos(Propagate->GetEuler(ePsi) + SteerAngle);
526 //%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
527 // Reset reporting functionality after takeoff
529 void FGLGear::ResetReporting(void)
531 if (Propagate->GetDistanceAGL() > 200.0) {
532 FirstContact = false;
533 StartedGroundRun = false;
534 LandingReported = false;
535 TakeoffReported = true;
536 LandingDistanceTraveled = 0.0;
537 MaximumStrutForce = MaximumStrutTravel = 0.0;
541 //%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
543 void FGLGear::InitializeReporting(void)
545 // If this is the first time the wheel has made contact, remember some values
546 // for later printout.
550 SinkRate = compressSpeed;
551 GroundSpeed = Propagate->GetVel().Magnitude();
552 TakeoffReported = false;
555 // If the takeoff run is starting, initialize.
557 if ((Propagate->GetVel().Magnitude() > 0.1) &&
558 (FCS->GetBrake(bgLeft) == 0) &&
559 (FCS->GetBrake(bgRight) == 0) &&
560 (FCS->GetThrottlePos(0) > 0.90) && !StartedGroundRun)
562 TakeoffDistanceTraveled = 0;
563 TakeoffDistanceTraveled50ft = 0;
564 StartedGroundRun = true;
568 //%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
569 // Takeoff and landing reporting functionality
571 void FGLGear::ReportTakeoffOrLanding(void)
573 double deltaT = State->Getdt()*Exec->GetGroundReactions()->GetRate();
576 LandingDistanceTraveled += Auxiliary->GetVground()*deltaT;
578 if (StartedGroundRun) {
579 TakeoffDistanceTraveled50ft += Auxiliary->GetVground()*deltaT;
580 if (WOW) TakeoffDistanceTraveled += Auxiliary->GetVground()*deltaT;
584 && Auxiliary->GetVground() <= 0.05
586 && Exec->GetGroundReactions()->GetWOW())
588 if (debug_lvl > 0) Report(erLand);
593 && (Propagate->GetDistanceAGL() - vLocalGear(eZ)) > 50.0
594 && !Exec->GetGroundReactions()->GetWOW())
596 if (debug_lvl > 0) Report(erTakeoff);
599 if (lastWOW != WOW) PutMessage("GEAR_CONTACT: " + name, WOW);
602 //%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
603 // Crash detection logic (really out-of-bounds detection)
605 void FGLGear::CrashDetect(void)
607 if ( (compressLength > 500.0 ||
608 vForce.Magnitude() > 100000000.0 ||
609 vMoment.Magnitude() > 5000000000.0 ||
610 SinkRate > 1.4666*30 ) && !State->IntegrationSuspended())
612 PutMessage("Crash Detected: Simulation FREEZE.");
613 State->SuspendIntegration();
617 //%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
618 // The following needs work regarding friction coefficients and braking and
619 // steering The BrakeFCoeff formula assumes that an anti-skid system is used.
620 // It also assumes that we won't be turning and braking at the same time.
621 // Will fix this later.
622 // [JSB] The braking force coefficients include normal rolling coefficient +
623 // a percentage of the static friction coefficient based on braking applied.
625 void FGLGear::ComputeBrakeForceCoefficient(void)
629 BrakeFCoeff = ( rollingFCoeff*(1.0 - FCS->GetBrake(bgLeft)) +
630 staticFCoeff*FCS->GetBrake(bgLeft) );
633 BrakeFCoeff = ( rollingFCoeff*(1.0 - FCS->GetBrake(bgRight)) +
634 staticFCoeff*FCS->GetBrake(bgRight) );
637 BrakeFCoeff = ( rollingFCoeff*(1.0 - FCS->GetBrake(bgCenter)) +
638 staticFCoeff*FCS->GetBrake(bgCenter) );
641 BrakeFCoeff = ( rollingFCoeff*(1.0 - FCS->GetBrake(bgCenter)) +
642 staticFCoeff*FCS->GetBrake(bgCenter) );
645 BrakeFCoeff = ( rollingFCoeff*(1.0 - FCS->GetBrake(bgCenter)) +
646 staticFCoeff*FCS->GetBrake(bgCenter) );
649 BrakeFCoeff = rollingFCoeff;
652 cerr << "Improper brake group membership detected for this gear." << endl;
657 //%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
658 // Compute the sideforce coefficients using similar assumptions to LaRCSim for now.
659 // Allow a maximum of 10 degrees tire slip angle before wheel slides. At that point,
660 // transition from static to dynamic friction. There are more complicated formulations
661 // of this that avoid the discrete jump (similar to Pacejka). Will fix this later.
663 void FGLGear::ComputeSideForceCoefficient(void)
667 FCoeff = ForceY_Table->GetValue(WheelSlip);
671 if (fabs(WheelSlip) <= 10.0) {
672 FCoeff = staticFCoeff*WheelSlip/10.0;
673 } else if (fabs(WheelSlip) <= 40.0) {
674 FCoeff = (dynamicFCoeff*(fabs(WheelSlip) - 10.0)/10.0
675 + staticFCoeff*(40.0 - fabs(WheelSlip))/10.0)*(WheelSlip>=0?1.0:-1.0);
677 FCoeff = dynamicFCoeff*(WheelSlip>=0?1.0:-1.0);
682 //%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
683 // Compute the vertical force on the wheel using square-law damping (per comment
684 // in paper AIAA-2000-4303 - see header prologue comments). We might consider
685 // allowing for both square and linear damping force calculation. Also need to
686 // possibly give a "rebound damping factor" that differs from the compression
689 void FGLGear::ComputeVerticalStrutForce(void)
691 double springForce = 0;
692 double dampForce = 0;
694 springForce = -compressLength * kSpring;
696 if (compressSpeed >= 0.0) {
698 if (eDampType == dtLinear) dampForce = -compressSpeed * bDamp;
699 else dampForce = -compressSpeed * compressSpeed * bDamp;
703 if (eDampTypeRebound == dtLinear)
704 dampForce = -compressSpeed * bDampRebound;
706 dampForce = compressSpeed * compressSpeed * bDampRebound;
709 vLocalForce(eZ) = min(springForce + dampForce, (double)0.0);
711 // Remember these values for reporting
712 MaximumStrutForce = max(MaximumStrutForce, fabs(vLocalForce(eZ)));
713 MaximumStrutTravel = max(MaximumStrutTravel, fabs(compressLength));
716 //%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
718 double FGLGear::GetGearUnitPos(void)
720 // hack to provide backward compatibility to gear/gear-pos-norm property
721 if( useFCSGearPos || FCS->GetGearPos() != 1.0 ) {
722 useFCSGearPos = true;
723 return FCS->GetGearPos();
728 //%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
730 void FGLGear::bind(void)
732 char property_name[80];
733 if (eContactType == ctBOGEY) {
734 snprintf(property_name, 80, "gear/unit[%d]/slip-angle-deg", GearNumber);
735 Exec->GetPropertyManager()->Tie( property_name, &WheelSlip );
736 snprintf(property_name, 80, "gear/unit[%d]/WOW", GearNumber);
737 Exec->GetPropertyManager()->Tie( property_name, &WOW );
738 snprintf(property_name, 80, "gear/unit[%d]/wheel-speed-fps", GearNumber);
739 Exec->GetPropertyManager()->Tie( property_name, &RollingWhlVel );
740 snprintf(property_name, 80, "gear/unit[%d]/z-position", GearNumber);
741 Exec->GetPropertyManager()->Tie( property_name, (FGLGear*)this,
742 &FGLGear::GetZPosition, &FGLGear::SetZPosition);
743 snprintf(property_name, 80, "gear/unit[%d]/compression-ft", GearNumber);
744 Exec->GetPropertyManager()->Tie( property_name, &compressLength );
747 if( isRetractable ) {
748 snprintf(property_name, 80, "gear/unit[%d]/pos-norm", GearNumber);
749 Exec->GetPropertyManager()->Tie( property_name, &GearPos );
754 //%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
756 void FGLGear::Report(ReportType repType)
758 if (fabs(TakeoffDistanceTraveled) < 0.001) return; // Don't print superfluous reports
762 cout << endl << "Touchdown report for " << name << endl;
763 cout << " Sink rate at contact: " << SinkRate << " fps, "
764 << SinkRate*0.3048 << " mps" << endl;
765 cout << " Contact ground speed: " << GroundSpeed*.5925 << " knots, "
766 << GroundSpeed*0.3048 << " mps" << endl;
767 cout << " Maximum contact force: " << MaximumStrutForce << " lbs, "
768 << MaximumStrutForce*4.448 << " Newtons" << endl;
769 cout << " Maximum strut travel: " << MaximumStrutTravel*12.0 << " inches, "
770 << MaximumStrutTravel*30.48 << " cm" << endl;
771 cout << " Distance traveled: " << LandingDistanceTraveled << " ft, "
772 << LandingDistanceTraveled*0.3048 << " meters" << endl;
773 LandingReported = true;
776 cout << endl << "Takeoff report for " << name << endl;
777 cout << " Distance traveled: " << TakeoffDistanceTraveled
778 << " ft, " << TakeoffDistanceTraveled*0.3048 << " meters" << endl;
779 cout << " Distance traveled (over 50'): " << TakeoffDistanceTraveled50ft
780 << " ft, " << TakeoffDistanceTraveled50ft*0.3048 << " meters" << endl;
781 TakeoffReported = true;
786 //%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
787 // The bitmasked value choices are as follows:
788 // unset: In this case (the default) JSBSim would only print
789 // out the normally expected messages, essentially echoing
790 // the config files as they are read. If the environment
791 // variable is not set, debug_lvl is set to 1 internally
792 // 0: This requests JSBSim not to output any messages
794 // 1: This value explicity requests the normal JSBSim
796 // 2: This value asks for a message to be printed out when
797 // a class is instantiated
798 // 4: When this value is set, a message is displayed when a
799 // FGModel object executes its Run() method
800 // 8: When this value is set, various runtime state variables
801 // are printed out periodically
802 // 16: When set various parameters are sanity checked and
803 // a message is printed out when they go out of bounds
805 void FGLGear::Debug(int from)
807 if (debug_lvl <= 0) return;
809 if (debug_lvl & 1) { // Standard console startup message output
810 if (from == 0) { // Constructor - loading and initialization
811 cout << " " << sContactType << " " << name << endl;
812 cout << " Location: " << vXYZ << endl;
813 cout << " Spring Constant: " << kSpring << endl;
815 if (eDampType == dtLinear)
816 cout << " Damping Constant: " << bDamp << " (linear)" << endl;
818 cout << " Damping Constant: " << bDamp << " (square law)" << endl;
820 if (eDampTypeRebound == dtLinear)
821 cout << " Rebound Damping Constant: " << bDampRebound << " (linear)" << endl;
823 cout << " Rebound Damping Constant: " << bDampRebound << " (square law)" << endl;
825 cout << " Dynamic Friction: " << dynamicFCoeff << endl;
826 cout << " Static Friction: " << staticFCoeff << endl;
827 if (eContactType == ctBOGEY) {
828 cout << " Rolling Friction: " << rollingFCoeff << endl;
829 cout << " Steering Type: " << sSteerType << endl;
830 cout << " Grouping: " << sBrakeGroup << endl;
831 cout << " Max Steer Angle: " << maxSteerAngle << endl;
832 cout << " Retractable: " << isRetractable << endl;
833 cout << " Relaxation Velocities:" << endl;
834 cout << " Rolling: " << RFRV << endl;
835 cout << " Side: " << SFRV << endl;
839 if (debug_lvl & 2 ) { // Instantiation/Destruction notification
840 if (from == 0) cout << "Instantiated: FGLGear" << endl;
841 if (from == 1) cout << "Destroyed: FGLGear" << endl;
843 if (debug_lvl & 4 ) { // Run() method entry print for FGModel-derived objects
845 if (debug_lvl & 8 ) { // Runtime state variables
847 if (debug_lvl & 16) { // Sanity checking
849 if (debug_lvl & 64) {
850 if (from == 0) { // Constructor
851 cout << IdSrc << endl;
852 cout << IdHdr << endl;
857 } // namespace JSBSim