Module: FGLGear.cpp
Author: Jon S. Berndt
Norman H. Princen
+ Bertrand Coconnier
Date started: 11/18/99
Purpose: Encapsulates the landing gear elements
Called by: FGAircraft
- ------------- Copyright (C) 1999 Jon S. Berndt (jsb@hal-pc.org) -------------
+ ------------- Copyright (C) 1999 Jon S. Berndt (jon@jsbsim.org) -------------
This program is free software; you can redistribute it and/or modify it under
the terms of the GNU Lesser General Public License as published by the Free Software
--------------------------------------------------------------------------------
11/18/99 JSB Created
01/30/01 NHP Extended gear model to properly simulate steering and braking
+07/08/09 BC Modified gear model to support large angles between aircraft and ground
/%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
INCLUDES
%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%*/
#include "FGLGear.h"
+#include "FGGroundReactions.h"
+#include "FGFCS.h"
+#include "FGAuxiliary.h"
+#include "FGAtmosphere.h"
+#include "FGMassBalance.h"
+#include "math/FGTable.h"
+#include <cstdlib>
+#include <cstring>
+
+using namespace std;
namespace JSBSim {
GLOBAL DATA
%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%*/
-static const char *IdSrc = "$Id$";
+static const char *IdSrc = "$Id: FGLGear.cpp,v 1.78 2010/10/07 03:45:40 jberndt Exp $";
static const char *IdHdr = ID_LGEAR;
+// Body To Structural (body frame is rotated 180 deg about Y and lengths are given in
+// ft instead of inches)
+const FGMatrix33 FGLGear::Tb2s(-1./inchtoft, 0., 0., 0., 1./inchtoft, 0., 0., 0., -1./inchtoft);
+
/*%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
CLASS IMPLEMENTATION
%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%*/
FGLGear::FGLGear(Element* el, FGFDMExec* fdmex, int number) :
+ FGForce(fdmex),
GearNumber(number),
- Exec(fdmex)
+ SteerAngle(0.0),
+ Castered(false),
+ StaticFriction(false)
{
Element *force_table=0;
Element *dampCoeff=0;
} else if (sContactType == "STRUCTURE") {
eContactType = ctSTRUCTURE;
} else {
- eContactType = ctUNKNOWN;
+ // Unknown contact point types will be treated as STRUCTURE.
+ eContactType = ctSTRUCTURE;
}
if (el->FindElement("spring_coeff"))
while (force_table) {
force_type = force_table->GetAttributeValue("type");
if (force_type == "CORNERING_COEFF") {
- ForceY_Table = new FGTable(Exec->GetPropertyManager(), force_table);
+ ForceY_Table = new FGTable(fdmex->GetPropertyManager(), force_table);
} else {
cerr << "Undefined force table for " << name << " contact point" << endl;
}
else sSteerType = "STEERABLE";
Element* element = el->FindElement("location");
- if (element) vXYZ = element->FindElementTripletConvertTo("IN");
+ if (element) vXYZn = element->FindElementTripletConvertTo("IN");
else {cerr << "No location given for contact " << name << endl; exit(-1);}
+ SetTransformType(FGForce::tCustom);
+
+ element = el->FindElement("orientation");
+ if (element && (eContactType == ctBOGEY)) {
+ vGearOrient = element->FindElementTripletConvertTo("RAD");
+
+ double cp,sp,cr,sr,cy,sy;
+
+ cp=cos(vGearOrient(ePitch)); sp=sin(vGearOrient(ePitch));
+ cr=cos(vGearOrient(eRoll)); sr=sin(vGearOrient(eRoll));
+ cy=cos(vGearOrient(eYaw)); sy=sin(vGearOrient(eYaw));
+
+ mTGear(1,1) = cp*cy;
+ mTGear(2,1) = cp*sy;
+ mTGear(3,1) = -sp;
+
+ mTGear(1,2) = sr*sp*cy - cr*sy;
+ mTGear(2,2) = sr*sp*sy + cr*cy;
+ mTGear(3,2) = sr*cp;
+
+ mTGear(1,3) = cr*sp*cy + sr*sy;
+ mTGear(2,3) = cr*sp*sy - sr*cy;
+ mTGear(3,3) = cr*cp;
+ }
+ else {
+ mTGear(1,1) = 1.;
+ mTGear(2,2) = 1.;
+ mTGear(3,3) = 1.;
+ }
if (sBrakeGroup == "LEFT" ) eBrakeGrp = bgLeft;
else if (sBrakeGroup == "RIGHT" ) eBrakeGrp = bgRight;
if (sSteerType == "STEERABLE") eSteerType = stSteer;
else if (sSteerType == "FIXED" ) eSteerType = stFixed;
- else if (sSteerType == "CASTERED" ) eSteerType = stCaster;
+ else if (sSteerType == "CASTERED" ) {eSteerType = stCaster; Castered = true;}
else if (sSteerType.empty() ) {eSteerType = stFixed;
sSteerType = "FIXED (defaulted)";}
else {
<< sSteerType << " is undefined." << endl;
}
- RFRV = 0.7; // Rolling force relaxation velocity, default value
- SFRV = 0.7; // Side force relaxation velocity, default value
-
- Element* relax_vel = el->FindElement("relaxation_velocity");
- if (relax_vel) {
- if (relax_vel->FindElement("rolling")) {
- RFRV = relax_vel->FindElementValueAsNumberConvertTo("rolling", "FT/SEC");
- }
- if (relax_vel->FindElement("side")) {
- SFRV = relax_vel->FindElementValueAsNumberConvertTo("side", "FT/SEC");
- }
- }
-
- State = Exec->GetState();
- LongForceLagFilterCoeff = 1/State->Getdt(); // default longitudinal force filter coefficient
- LatForceLagFilterCoeff = 1/State->Getdt(); // default lateral force filter coefficient
-
- Element* force_lag_filter_elem = el->FindElement("force_lag_filter");
- if (force_lag_filter_elem) {
- if (force_lag_filter_elem->FindElement("rolling")) {
- LongForceLagFilterCoeff = force_lag_filter_elem->FindElementValueAsNumber("rolling");
- }
- if (force_lag_filter_elem->FindElement("side")) {
- LatForceLagFilterCoeff = force_lag_filter_elem->FindElementValueAsNumber("side");
- }
- }
-
- WheelSlipLagFilterCoeff = 1/State->Getdt();
+ Auxiliary = fdmex->GetAuxiliary();
+ Propagate = fdmex->GetPropagate();
+ FCS = fdmex->GetFCS();
+ MassBalance = fdmex->GetMassBalance();
+ GroundReactions = fdmex->GetGroundReactions();
- Element *wheel_slip_angle_lag_elem = el->FindElement("wheel_slip_filter");
- if (wheel_slip_angle_lag_elem) {
- WheelSlipLagFilterCoeff = wheel_slip_angle_lag_elem->GetDataAsNumber();
- }
-
GearUp = false;
GearDown = true;
GearPos = 1.0;
// Add some AI here to determine if gear is located properly according to its
// brake group type ??
- State = Exec->GetState();
- Aircraft = Exec->GetAircraft();
- Propagate = Exec->GetPropagate();
- Auxiliary = Exec->GetAuxiliary();
- FCS = Exec->GetFCS();
- MassBalance = Exec->GetMassBalance();
-
WOW = lastWOW = false;
ReportEnable = true;
FirstContact = false;
TakeoffReported = LandingReported = false;
LandingDistanceTraveled = TakeoffDistanceTraveled = TakeoffDistanceTraveled50ft = 0.0;
MaximumStrutForce = MaximumStrutTravel = 0.0;
- SideForce = RollingForce = 0.0;
SinkRate = GroundSpeed = 0.0;
- vWhlBodyVec = MassBalance->StructuralToBody(vXYZ);
-
+ vWhlBodyVec = MassBalance->StructuralToBody(vXYZn);
vLocalGear = Propagate->GetTb2l() * vWhlBodyVec;
+ vWhlVelVec.InitMatrix();
compressLength = 0.0;
compressSpeed = 0.0;
WheelSlip = 0.0;
TirePressureNorm = 1.0;
- SideWhlVel = 0.0;
- RollingWhlVel = 0.0;
+ // Set Pacejka terms
- SinWheel = 0.0;
- CosWheel = 0.0;
+ Stiffness = 0.06;
+ Shape = 2.8;
+ Peak = staticFCoeff;
+ Curvature = 1.03;
- prevSlipIn = 0.0;
- prevSlipOut = 0.0;
+ // Initialize Lagrange multipliers
+ memset(LMultiplier, 0, sizeof(LMultiplier));
Debug(0);
}
//%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
-FGLGear::FGLGear(const FGLGear& lgear)
-{
- GearNumber = lgear.GearNumber;
- State = lgear.State;
- Aircraft = lgear.Aircraft;
- Propagate = lgear.Propagate;
- Auxiliary = lgear.Auxiliary;
- Exec = lgear.Exec;
- FCS = lgear.FCS;
- MassBalance = lgear.MassBalance;
-
- vXYZ = lgear.vXYZ;
- vMoment = lgear.vMoment;
- vWhlBodyVec = lgear.vWhlBodyVec;
- vLocalGear = lgear.vLocalGear;
-
- WOW = lgear.WOW;
- lastWOW = lgear.lastWOW;
- ReportEnable = lgear.ReportEnable;
- FirstContact = lgear.FirstContact;
- StartedGroundRun = lgear.StartedGroundRun;
- LandingDistanceTraveled = lgear.LandingDistanceTraveled;
- TakeoffDistanceTraveled = lgear.TakeoffDistanceTraveled;
- TakeoffDistanceTraveled50ft = lgear.TakeoffDistanceTraveled50ft;
- MaximumStrutForce = lgear.MaximumStrutForce;
- MaximumStrutTravel = lgear.MaximumStrutTravel;
- SideForce = lgear.SideForce;
- RollingForce = lgear.RollingForce;
-
- kSpring = lgear.kSpring;
- bDamp = lgear.bDamp;
- bDampRebound = lgear.bDampRebound;
- compressLength = lgear.compressLength;
- compressSpeed = lgear.compressSpeed;
- staticFCoeff = lgear.staticFCoeff;
- dynamicFCoeff = lgear.dynamicFCoeff;
- rollingFCoeff = lgear.rollingFCoeff;
- brakePct = lgear.brakePct;
- maxCompLen = lgear.maxCompLen;
- SinkRate = lgear.SinkRate;
- GroundSpeed = lgear.GroundSpeed;
- LandingReported = lgear.LandingReported;
- TakeoffReported = lgear.TakeoffReported;
- name = lgear.name;
- sSteerType = lgear.sSteerType;
- sRetractable = lgear.sRetractable;
- sContactType = lgear.sContactType;
- eContactType = lgear.eContactType;
- sBrakeGroup = lgear.sBrakeGroup;
- eSteerType = lgear.eSteerType;
- eBrakeGrp = lgear.eBrakeGrp;
- maxSteerAngle = lgear.maxSteerAngle;
- isRetractable = lgear.isRetractable;
- GearUp = lgear.GearUp;
- GearDown = lgear.GearDown;
- GearPos = lgear.GearPos;
- useFCSGearPos = lgear.useFCSGearPos;
- WheelSlip = lgear.WheelSlip;
- TirePressureNorm = lgear.TirePressureNorm;
- Servicable = lgear.Servicable;
- ForceY_Table = lgear.ForceY_Table;
- CosWheel = lgear.CosWheel;
- SinWheel = lgear.SinWheel;
- prevOut = lgear.prevOut;
- prevIn = lgear.prevIn;
- prevSlipIn = lgear.prevSlipIn;
- prevSlipOut = lgear.prevSlipOut;
- RFRV = lgear.RFRV;
- SFRV = lgear.SFRV;
- LongForceLagFilterCoeff = lgear.LongForceLagFilterCoeff;
- LatForceLagFilterCoeff = lgear.LatForceLagFilterCoeff;
- WheelSlipLagFilterCoeff = lgear.WheelSlipLagFilterCoeff;
-}
-
-//%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
-
FGLGear::~FGLGear()
{
+ delete ForceY_Table;
Debug(1);
}
//%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
-FGColumnVector3& FGLGear::Force(void)
+FGColumnVector3& FGLGear::GetBodyForces(void)
{
- double t = Exec->GetState()->Getsim_time();
- dT = State->Getdt()*Exec->GetGroundReactions()->GetRate();
+ double t = fdmex->GetSimTime();
+ dT = fdmex->GetDeltaT()*GroundReactions->GetRate();
- vForce.InitMatrix();
- vMoment.InitMatrix();
+ vFn.InitMatrix();
if (isRetractable) ComputeRetractionState();
if (GearDown) {
+ FGColumnVector3 angularVel;
- vWhlBodyVec = MassBalance->StructuralToBody(vXYZ); // Get wheel in body frame
+ vWhlBodyVec = MassBalance->StructuralToBody(vXYZn); // Get wheel in body frame
vLocalGear = Propagate->GetTb2l() * vWhlBodyVec; // Get local frame wheel location
gearLoc = Propagate->GetLocation().LocalToLocation(vLocalGear);
- compressLength = -Exec->GetGroundCallback()->GetAGLevel(t, gearLoc, contact, normal, cvel);
-
- // The compression length is measured in the Z-axis, only, at this time.
+ // Compute the height of the theoretical location of the wheel (if strut is
+ // not compressed) with respect to the ground level
+ double height = fdmex->GetGroundCallback()->GetAGLevel(t, gearLoc, contact, normal, cvel, angularVel);
+ vGroundNormal = Propagate->GetTec2b() * normal;
+
+ // The height returned above is the AGL and is expressed in the Z direction
+ // of the ECEF coordinate frame. We now need to transform this height in
+ // actual compression of the strut (BOGEY) of in the normal direction to the
+ // ground (STRUCTURE)
+ double normalZ = (Propagate->GetTec2l()*normal)(eZ);
+ double LGearProj = -(mTGear.Transposed() * vGroundNormal)(eZ);
+
+ switch (eContactType) {
+ case ctBOGEY:
+ compressLength = LGearProj > 0.0 ? height * normalZ / LGearProj : 0.0;
+ break;
+ case ctSTRUCTURE:
+ compressLength = height * normalZ / DotProduct(normal, normal);
+ break;
+ }
if (compressLength > 0.00) {
WOW = true;
- // [The next equation should really use the vector to the contact patch of
- // the tire including the strut compression and not the original vWhlBodyVec.]
+ // The following equations use the vector to the tire contact patch
+ // including the strut compression.
+ FGColumnVector3 vWhlDisplVec;
+
+ switch(eContactType) {
+ case ctBOGEY:
+ vWhlDisplVec = mTGear * FGColumnVector3(0., 0., -compressLength);
+ break;
+ case ctSTRUCTURE:
+ vWhlDisplVec = compressLength * vGroundNormal;
+ break;
+ }
+
+ FGColumnVector3 vWhlContactVec = vWhlBodyVec + vWhlDisplVec;
+ vActingXYZn = vXYZn + Tb2s * vWhlDisplVec;
+ FGColumnVector3 vBodyWhlVel = Propagate->GetPQR() * vWhlContactVec;
+ vBodyWhlVel += Propagate->GetUVW() - Propagate->GetTec2b() * cvel;
- vWhlVelVec = Propagate->GetTb2l() * (Propagate->GetPQR() * vWhlBodyVec);
- vWhlVelVec += Propagate->GetVel() - cvel;
- compressSpeed = vWhlVelVec(eZ);
+ vWhlVelVec = mTGear.Transposed() * vBodyWhlVel;
InitializeReporting();
- ComputeBrakeForceCoefficient();
ComputeSteeringAngle();
- ComputeSlipAngle();
- ComputeSideForceCoefficient();
- ComputeVerticalStrutForce();
-
- // Compute the forces in the wheel ground plane.
-
- double sign = RollingWhlVel>0?1.0:(RollingWhlVel<0?-1.0:0.0);
- RollingForce = ((1.0 - TirePressureNorm) * 30 + vLocalForce(eZ) * BrakeFCoeff) * sign;
- SideForce = vLocalForce(eZ) * FCoeff;
-
- // Transform these forces back to the local reference frame.
-
- vLocalForce(eX) = RollingForce*CosWheel - SideForce*SinWheel;
- vLocalForce(eY) = SideForce*CosWheel + RollingForce*SinWheel;
-
- // Transform the forces back to the body frame and compute the moment.
-
- vForce = Propagate->GetTl2b() * vLocalForce;
+ ComputeGroundCoordSys();
- // Lag and attenuate the XY-plane forces dependent on velocity
+ vLocalWhlVel = Transform().Transposed() * vBodyWhlVel;
- double ca, cb, denom;
- FGColumnVector3 Output;
+ compressSpeed = -vLocalWhlVel(eX);
+ if (eContactType == ctBOGEY)
+ compressSpeed /= LGearProj;
- // This code implements a lag filter, C/(s + C) where
- // "C" is the filter coefficient. When "C" is chosen at the
- // frame rate (in Hz), the jittering is significantly reduced. This is because
- // the jitter is present *at* the execution rate.
- // If a coefficient is set to something equal to or less than zero, the filter
- // is bypassed.
+ ComputeVerticalStrutForce();
- if (LongForceLagFilterCoeff > 0) {
- denom = 2.00 + dT*LongForceLagFilterCoeff;
- ca = dT*LongForceLagFilterCoeff / denom;
- cb = (2.00 - dT*LongForceLagFilterCoeff) / denom;
- Output(eX) = vForce(eX) * ca + prevIn(eX) * ca + prevOut(eX) * cb;
- vForce(eX) = Output(eX);
- }
- if (LatForceLagFilterCoeff > 0) {
- denom = 2.00 + dT*LatForceLagFilterCoeff;
- ca = dT*LatForceLagFilterCoeff / denom;
- cb = (2.00 - dT*LatForceLagFilterCoeff) / denom;
- Output(eY) = vForce(eY) * ca + prevIn(eY) * ca + prevOut(eY) * cb;
- vForce(eY) = Output(eY);
+ // Compute the friction coefficients in the wheel ground plane.
+ if (eContactType == ctBOGEY) {
+ ComputeSlipAngle();
+ ComputeBrakeForceCoefficient();
+ ComputeSideForceCoefficient();
}
- prevIn = vForce;
- prevOut = Output;
-
- if ((fabs(RollingWhlVel) <= RFRV) && RFRV > 0) vForce(eX) *= fabs(RollingWhlVel)/RFRV;
- if ((fabs(SideWhlVel) <= SFRV) && SFRV > 0) vForce(eY) *= fabs(SideWhlVel)/SFRV;
-
- // End section for attentuating gear jitter
-
- vMoment = vWhlBodyVec * vForce;
+ // Prepare the Jacobians and the Lagrange multipliers for later friction
+ // forces calculations.
+ ComputeJacobian(vWhlContactVec);
} else { // Gear is NOT compressed
WOW = false;
compressLength = 0.0;
+ compressSpeed = 0.0;
+ WheelSlip = 0.0;
+ StrutForce = 0.0;
+
+ // Let wheel spin down slowly
+ vWhlVelVec(eX) -= 13.0*dT;
+ if (vWhlVelVec(eX) < 0.0) vWhlVelVec(eX) = 0.0;
// Return to neutral position between 1.0 and 0.8 gear pos.
SteerAngle *= max(GetGearUnitPos()-0.8, 0.0)/0.2;
lastWOW = WOW;
- return vForce;
+ return FGForce::GetBodyForces();
+}
+
+//%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
+// Build a local "ground" coordinate system defined by
+// eX : normal to the ground
+// eY : projection of the rolling direction on the ground
+// eZ : projection of the sliping direction on the ground
+
+void FGLGear::ComputeGroundCoordSys(void)
+{
+ // Euler angles are built up to create a local frame to describe the forces
+ // applied to the gear by the ground. Here pitch, yaw and roll do not have
+ // any physical meaning. It is just a convenient notation.
+ // First, "pitch" and "yaw" are determined in order to align eX with the
+ // ground normal.
+ if (vGroundNormal(eZ) < -1.0)
+ vOrient(ePitch) = 0.5*M_PI;
+ else if (1.0 < vGroundNormal(eZ))
+ vOrient(ePitch) = -0.5*M_PI;
+ else
+ vOrient(ePitch) = asin(-vGroundNormal(eZ));
+
+ if (fabs(vOrient(ePitch)) == 0.5*M_PI)
+ vOrient(eYaw) = 0.;
+ else
+ vOrient(eYaw) = atan2(vGroundNormal(eY), vGroundNormal(eX));
+
+ vOrient(eRoll) = 0.;
+ UpdateCustomTransformMatrix();
+
+ if (eContactType == ctBOGEY) {
+ // In the case of a bogey, the third angle "roll" is used to align the axis eY and eZ
+ // to the rolling and sliping direction respectively.
+ FGColumnVector3 updatedRollingAxis = Transform().Transposed() * mTGear
+ * FGColumnVector3(-sin(SteerAngle), cos(SteerAngle), 0.);
+
+ vOrient(eRoll) = atan2(updatedRollingAxis(eY), -updatedRollingAxis(eZ));
+ UpdateCustomTransformMatrix();
+ }
}
//%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
GearUp = true;
WOW = false;
GearDown = false;
+ vWhlVelVec.InitMatrix();
} else if (gearPos > 0.99) {
GearDown = true;
GearUp = false;
}
//%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
+// Calculate tire slip angle.
void FGLGear::ComputeSlipAngle(void)
{
- // Transform the wheel velocities from the local axis system to the wheel axis system.
- RollingWhlVel = vWhlVelVec(eX)*CosWheel + vWhlVelVec(eY)*SinWheel;
- SideWhlVel = vWhlVelVec(eY)*CosWheel - vWhlVelVec(eX)*SinWheel;
-
- // Calculate tire slip angle.
- WheelSlip = atan2(SideWhlVel, fabs(RollingWhlVel))*radtodeg;
-
- // Filter the wheel slip angle
-
- double SlipOutput, ca, cb, denom;
-
- if (WheelSlipLagFilterCoeff > 0) {
- denom = 2.00 + dT*WheelSlipLagFilterCoeff;
- ca = dT*WheelSlipLagFilterCoeff / denom;
- cb = (2.00 - dT*WheelSlipLagFilterCoeff) / denom;
-
- SlipOutput = ca * (WheelSlip + prevSlipIn) + cb * prevSlipOut;
-
- prevSlipIn = WheelSlip;
- WheelSlip = prevSlipOut = SlipOutput;
- }
+// Check that the speed is non-null otherwise use the current angle
+ if (vLocalWhlVel.Magnitude(eY,eZ) > 1E-3)
+ WheelSlip = -atan2(vLocalWhlVel(eZ), fabs(vLocalWhlVel(eY)))*radtodeg;
}
//%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
void FGLGear::ComputeSteeringAngle(void)
{
- double casterLocalFrameAngleRad = 0.0;
- double casterAngle = 0.0;
-
switch (eSteerType) {
case stSteer:
SteerAngle = degtorad * FCS->GetSteerPosDeg(GearNumber);
SteerAngle = 0.0;
break;
case stCaster:
- // This is not correct for castering gear. Should make steer angle parallel
- // to the actual velocity vector of the wheel, given aircraft velocity vector
- // and omega.
- SteerAngle = 0.0;
- casterLocalFrameAngleRad = acos(vWhlVelVec(eX)/vWhlVelVec.Magnitude());
- casterAngle = casterLocalFrameAngleRad - Propagate->GetEuler(ePsi);
+ if (!Castered)
+ SteerAngle = degtorad * FCS->GetSteerPosDeg(GearNumber);
+ else {
+ // Check that the speed is non-null otherwise use the current angle
+ if (vWhlVelVec.Magnitude(eX,eY) > 0.1)
+ SteerAngle = atan2(vWhlVelVec(eY), fabs(vWhlVelVec(eX)));
+ }
break;
default:
cerr << "Improper steering type membership detected for this gear." << endl;
break;
}
-
- SinWheel = sin(Propagate->GetEuler(ePsi) + SteerAngle);
- CosWheel = cos(Propagate->GetEuler(ePsi) + SteerAngle);
}
//%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
void FGLGear::ReportTakeoffOrLanding(void)
{
- double deltaT = State->Getdt()*Exec->GetGroundReactions()->GetRate();
-
if (FirstContact)
- LandingDistanceTraveled += Auxiliary->GetVground()*deltaT;
+ LandingDistanceTraveled += Auxiliary->GetVground()*dT;
if (StartedGroundRun) {
- TakeoffDistanceTraveled50ft += Auxiliary->GetVground()*deltaT;
- if (WOW) TakeoffDistanceTraveled += Auxiliary->GetVground()*deltaT;
+ TakeoffDistanceTraveled50ft += Auxiliary->GetVground()*dT;
+ if (WOW) TakeoffDistanceTraveled += Auxiliary->GetVground()*dT;
}
if ( ReportEnable
&& Auxiliary->GetVground() <= 0.05
&& !LandingReported
- && Exec->GetGroundReactions()->GetWOW())
+ && GroundReactions->GetWOW())
{
if (debug_lvl > 0) Report(erLand);
}
if ( ReportEnable
&& !TakeoffReported
&& (Propagate->GetDistanceAGL() - vLocalGear(eZ)) > 50.0
- && !Exec->GetGroundReactions()->GetWOW())
+ && !GroundReactions->GetWOW())
{
if (debug_lvl > 0) Report(erTakeoff);
}
void FGLGear::CrashDetect(void)
{
if ( (compressLength > 500.0 ||
- vForce.Magnitude() > 100000000.0 ||
- vMoment.Magnitude() > 5000000000.0 ||
- SinkRate > 1.4666*30 ) && !State->IntegrationSuspended())
+ vFn.Magnitude() > 100000000.0 ||
+ GetMoments().Magnitude() > 5000000000.0 ||
+ SinkRate > 1.4666*30 ) && !fdmex->IntegrationSuspended())
{
PutMessage("Crash Detected: Simulation FREEZE.");
- State->SuspendIntegration();
+ fdmex->SuspendIntegration();
}
}
}
//%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
-// Compute the sideforce coefficients using similar assumptions to LaRCSim for now.
-// Allow a maximum of 10 degrees tire slip angle before wheel slides. At that point,
-// transition from static to dynamic friction. There are more complicated formulations
-// of this that avoid the discrete jump (similar to Pacejka). Will fix this later.
+// Compute the sideforce coefficients using Pacejka's Magic Formula.
+//
+// y(x) = D sin {C arctan [Bx - E(Bx - arctan Bx)]}
+//
+// Where: B = Stiffness Factor (0.06, here)
+// C = Shape Factor (2.8, here)
+// D = Peak Factor (0.8, here)
+// E = Curvature Factor (1.03, here)
void FGLGear::ComputeSideForceCoefficient(void)
{
if (ForceY_Table) {
-
FCoeff = ForceY_Table->GetValue(WheelSlip);
-
} else {
-
- if (fabs(WheelSlip) <= 10.0) {
- FCoeff = staticFCoeff*WheelSlip/10.0;
- } else if (fabs(WheelSlip) <= 40.0) {
- FCoeff = (dynamicFCoeff*(fabs(WheelSlip) - 10.0)/10.0
- + staticFCoeff*(40.0 - fabs(WheelSlip))/10.0)*(WheelSlip>=0?1.0:-1.0);
- } else {
- FCoeff = dynamicFCoeff*(WheelSlip>=0?1.0:-1.0);
- }
+ double StiffSlip = Stiffness*WheelSlip;
+ FCoeff = Peak * sin(Shape*atan(StiffSlip - Curvature*(StiffSlip - atan(StiffSlip))));
}
}
dampForce = compressSpeed * compressSpeed * bDampRebound;
}
- vLocalForce(eZ) = min(springForce + dampForce, (double)0.0);
+
+ StrutForce = min(springForce + dampForce, (double)0.0);
+
+ // The reaction force of the wheel is always normal to the ground
+ switch (eContactType) {
+ case ctBOGEY:
+ // Project back the strut force in the local coordinate frame of the ground
+ vFn(eX) = StrutForce / (mTGear.Transposed()*vGroundNormal)(eZ);
+ break;
+ case ctSTRUCTURE:
+ vFn(eX) = -StrutForce;
+ break;
+ }
// Remember these values for reporting
- MaximumStrutForce = max(MaximumStrutForce, fabs(vLocalForce(eZ)));
+ MaximumStrutForce = max(MaximumStrutForce, fabs(StrutForce));
MaximumStrutTravel = max(MaximumStrutTravel, fabs(compressLength));
}
return GearPos;
}
+//%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
+// Compute the jacobian entries for the friction forces resolution later
+// in FGPropagate
+
+void FGLGear::ComputeJacobian(const FGColumnVector3& vWhlContactVec)
+{
+ // When the point of contact is moving, dynamic friction is used
+ // This type of friction is limited to ctSTRUCTURE elements because their
+ // friction coefficient is the same in every directions
+ if ((eContactType == ctSTRUCTURE) && (vLocalWhlVel.Magnitude(eY,eZ) > 1E-3)) {
+ FGColumnVector3 velocityDirection = vLocalWhlVel;
+
+ StaticFriction = false;
+
+ velocityDirection(eX) = 0.;
+ velocityDirection.Normalize();
+
+ LMultiplier[ftDynamic].ForceJacobian = Transform()*velocityDirection;
+ LMultiplier[ftDynamic].MomentJacobian = vWhlContactVec * LMultiplier[ftDynamic].ForceJacobian;
+ LMultiplier[ftDynamic].Max = 0.;
+ LMultiplier[ftDynamic].Min = -fabs(dynamicFCoeff * vFn(eX));
+ LMultiplier[ftDynamic].value = Constrain(LMultiplier[ftDynamic].Min, LMultiplier[ftDynamic].value, LMultiplier[ftDynamic].Max);
+ }
+ else {
+ // Static friction is used for ctSTRUCTURE when the contact point is not moving.
+ // It is always used for ctBOGEY elements because the friction coefficients
+ // of a tyre depend on the direction of the movement (roll & side directions).
+ // This cannot be handled properly by the so-called "dynamic friction".
+ StaticFriction = true;
+
+ LMultiplier[ftRoll].ForceJacobian = Transform()*FGColumnVector3(0.,1.,0.);
+ LMultiplier[ftSide].ForceJacobian = Transform()*FGColumnVector3(0.,0.,1.);
+ LMultiplier[ftRoll].MomentJacobian = vWhlContactVec * LMultiplier[ftRoll].ForceJacobian;
+ LMultiplier[ftSide].MomentJacobian = vWhlContactVec * LMultiplier[ftSide].ForceJacobian;
+
+ switch(eContactType) {
+ case ctBOGEY:
+ LMultiplier[ftRoll].Max = fabs(BrakeFCoeff * vFn(eX));
+ LMultiplier[ftSide].Max = fabs(FCoeff * vFn(eX));
+ break;
+ case ctSTRUCTURE:
+ LMultiplier[ftRoll].Max = fabs(staticFCoeff * vFn(eX));
+ LMultiplier[ftSide].Max = fabs(staticFCoeff * vFn(eX));
+ break;
+ }
+
+ LMultiplier[ftRoll].Min = -LMultiplier[ftRoll].Max;
+ LMultiplier[ftSide].Min = -LMultiplier[ftSide].Max;
+ LMultiplier[ftRoll].value = Constrain(LMultiplier[ftRoll].Min, LMultiplier[ftRoll].value, LMultiplier[ftRoll].Max);
+ LMultiplier[ftSide].value = Constrain(LMultiplier[ftSide].Min, LMultiplier[ftSide].value, LMultiplier[ftSide].Max);
+ }
+}
+
+//%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
+// This function is used by the MultiplierIterator class to enumerate the
+// Lagrange multipliers of a landing gear. This allows to encapsulate the storage
+// of the multipliers in FGLGear without exposing it. From an outside point of
+// view, each FGLGear instance has a number of Lagrange multipliers which can be
+// accessed through this routine without knowing the exact constraint which they
+// model.
+
+FGPropagate::LagrangeMultiplier* FGLGear::GetMultiplierEntry(int entry)
+{
+ switch(entry) {
+ case 0:
+ if (StaticFriction)
+ return &LMultiplier[ftRoll];
+ else
+ return &LMultiplier[ftDynamic];
+ case 1:
+ if (StaticFriction)
+ return &LMultiplier[ftSide];
+ default:
+ return NULL;
+ }
+}
+
+//%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
+// This routine is called after the Lagrange multiplier has been computed. The
+// friction forces of the landing gear are then updated accordingly.
+FGColumnVector3& FGLGear::UpdateForces(void)
+{
+ if (StaticFriction) {
+ vFn(eY) = LMultiplier[ftRoll].value;
+ vFn(eZ) = LMultiplier[ftSide].value;
+ }
+ else
+ vFn += LMultiplier[ftDynamic].value * (Transform ().Transposed() * LMultiplier[ftDynamic].ForceJacobian);
+
+ // Return the updated force in the body frame
+ return FGForce::GetBodyForces();
+}
+
//%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
void FGLGear::bind(void)
{
- char property_name[80];
+ string property_name;
+ string base_property_name;
+ base_property_name = CreateIndexedPropertyName("gear/unit", GearNumber);
if (eContactType == ctBOGEY) {
- snprintf(property_name, 80, "gear/unit[%d]/slip-angle-deg", GearNumber);
- Exec->GetPropertyManager()->Tie( property_name, &WheelSlip );
- snprintf(property_name, 80, "gear/unit[%d]/WOW", GearNumber);
- Exec->GetPropertyManager()->Tie( property_name, &WOW );
- snprintf(property_name, 80, "gear/unit[%d]/wheel-speed-fps", GearNumber);
- Exec->GetPropertyManager()->Tie( property_name, &RollingWhlVel );
- snprintf(property_name, 80, "gear/unit[%d]/z-position", GearNumber);
- Exec->GetPropertyManager()->Tie( property_name, (FGLGear*)this,
- &FGLGear::GetZPosition, &FGLGear::SetZPosition);
- snprintf(property_name, 80, "gear/unit[%d]/compression-ft", GearNumber);
- Exec->GetPropertyManager()->Tie( property_name, &compressLength );
+ property_name = base_property_name + "/slip-angle-deg";
+ fdmex->GetPropertyManager()->Tie( property_name.c_str(), &WheelSlip );
+ property_name = base_property_name + "/WOW";
+ fdmex->GetPropertyManager()->Tie( property_name.c_str(), &WOW );
+ property_name = base_property_name + "/wheel-speed-fps";
+ fdmex->GetPropertyManager()->Tie( property_name.c_str(), (FGLGear*)this,
+ &FGLGear::GetWheelRollVel);
+ property_name = base_property_name + "/z-position";
+ fdmex->GetPropertyManager()->Tie( property_name.c_str(), (FGForce*)this,
+ &FGForce::GetLocationZ, &FGForce::SetLocationZ);
+ property_name = base_property_name + "/compression-ft";
+ fdmex->GetPropertyManager()->Tie( property_name.c_str(), &compressLength );
+ property_name = base_property_name + "/side_friction_coeff";
+ fdmex->GetPropertyManager()->Tie( property_name.c_str(), &FCoeff );
+
+ property_name = base_property_name + "/static_friction_coeff";
+ fdmex->GetPropertyManager()->Tie( property_name.c_str(), &staticFCoeff );
+
+ if (eSteerType == stCaster) {
+ property_name = base_property_name + "/steering-angle-deg";
+ fdmex->GetPropertyManager()->Tie( property_name.c_str(), this, &FGLGear::GetSteerAngleDeg );
+ property_name = base_property_name + "/castered";
+ fdmex->GetPropertyManager()->Tie( property_name.c_str(), &Castered);
+ }
}
if( isRetractable ) {
- snprintf(property_name, 80, "gear/unit[%d]/pos-norm", GearNumber);
- Exec->GetPropertyManager()->Tie( property_name, &GearPos );
+ property_name = base_property_name + "/pos-norm";
+ fdmex->GetPropertyManager()->Tie( property_name.c_str(), &GearPos );
}
-
}
//%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
switch(repType) {
case erLand:
- cout << endl << "Touchdown report for " << name << endl;
+ cout << endl << "Touchdown report for " << name << " (WOW at time: "
+ << fdmex->GetSimTime() << " seconds)" << endl;
cout << " Sink rate at contact: " << SinkRate << " fps, "
<< SinkRate*0.3048 << " mps" << endl;
cout << " Contact ground speed: " << GroundSpeed*.5925 << " knots, "
LandingReported = true;
break;
case erTakeoff:
- cout << endl << "Takeoff report for " << name << endl;
+ cout << endl << "Takeoff report for " << name << " (Liftoff at time: "
+ << fdmex->GetSimTime() << " seconds)" << endl;
cout << " Distance traveled: " << TakeoffDistanceTraveled
<< " ft, " << TakeoffDistanceTraveled*0.3048 << " meters" << endl;
cout << " Distance traveled (over 50'): " << TakeoffDistanceTraveled50ft
<< " ft, " << TakeoffDistanceTraveled50ft*0.3048 << " meters" << endl;
+ cout << " [Altitude (ASL): " << Propagate->GetAltitudeASL() << " ft. / "
+ << Propagate->GetAltitudeASLmeters() << " m | Temperature: "
+ << fdmex->GetAtmosphere()->GetTemperature() - 459.67 << " F / "
+ << RankineToCelsius(fdmex->GetAtmosphere()->GetTemperature()) << " C]" << endl;
+ cout << " [Velocity (KCAS): " << Auxiliary->GetVcalibratedKTS() << "]" << endl;
TakeoffReported = true;
break;
+ case erNone:
+ break;
}
}
if (debug_lvl & 1) { // Standard console startup message output
if (from == 0) { // Constructor - loading and initialization
cout << " " << sContactType << " " << name << endl;
- cout << " Location: " << vXYZ << endl;
+ cout << " Location: " << vXYZn << endl;
cout << " Spring Constant: " << kSpring << endl;
if (eDampType == dtLinear)
cout << " Grouping: " << sBrakeGroup << endl;
cout << " Max Steer Angle: " << maxSteerAngle << endl;
cout << " Retractable: " << isRetractable << endl;
- cout << " Relaxation Velocities:" << endl;
- cout << " Rolling: " << RFRV << endl;
- cout << " Side: " << SFRV << endl;
}
}
}
projects / flightgear.git / blobdiff