-/*******************************************************************************
+/*%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
Module: FGLGear.cpp
Author: Jon S. Berndt
+ Norman H. Princen
Date started: 11/18/99
Purpose: Encapsulates the landing gear elements
Called by: FGAircraft
HISTORY
--------------------------------------------------------------------------------
11/18/99 JSB Created
+01/30/01 NHP Extended gear model to properly simulate steering and braking
-********************************************************************************
+%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
INCLUDES
-*******************************************************************************/
+%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%*/
#include "FGLGear.h"
#include <algorithm>
-/*******************************************************************************
-************************************ CODE **************************************
-*******************************************************************************/
+/*%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
+DEFINITIONS
+%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%*/
+/*%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
+GLOBAL DATA
+%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%*/
-FGLGear::FGLGear(FGConfigFile* AC_cfg, FGFDMExec* fdmex) : vXYZ(3),
- vMoment(3),
- Exec(fdmex)
-{
- string tmp;
- *AC_cfg >> tmp >> name >> vXYZ(1) >> vXYZ(2) >> vXYZ(3) >> kSpring >> bDamp
- >> statFCoeff >> brakeCoeff;
- State = Exec->GetState();
- Aircraft = Exec->GetAircraft();
- Position = Exec->GetPosition();
- Rotation = Exec->GetRotation();
-
- WOW = false;
-}
+static const char *IdSrc = "$Id$";
+static const char *IdHdr = ID_LGEAR;
-/******************************************************************************/
+/*%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
+CLASS IMPLEMENTATION
+%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%*/
-FGLGear::~FGLGear(void)
+FGLGear::FGLGear(FGConfigFile* AC_cfg, FGFDMExec* fdmex) : Exec(fdmex)
{
-}
-
-/******************************************************************************/
+ string tmp;
+
+ *AC_cfg >> tmp >> name >> vXYZ(1) >> vXYZ(2) >> vXYZ(3)
+ >> kSpring >> bDamp>> dynamicFCoeff >> staticFCoeff
+ >> rollingFCoeff >> sSteerType >> sBrakeGroup
+ >> maxSteerAngle >> sRetractable;
+
+ if (sBrakeGroup == "LEFT" ) eBrakeGrp = bgLeft;
+ else if (sBrakeGroup == "RIGHT" ) eBrakeGrp = bgRight;
+ else if (sBrakeGroup == "CENTER") eBrakeGrp = bgCenter;
+ else if (sBrakeGroup == "NOSE" ) eBrakeGrp = bgNose;
+ else if (sBrakeGroup == "TAIL" ) eBrakeGrp = bgTail;
+ else if (sBrakeGroup == "NONE" ) eBrakeGrp = bgNone;
+ else {
+ cerr << "Improper braking group specification in config file: "
+ << sBrakeGroup << " is undefined." << endl;
+ }
-FGColumnVector FGLGear::Force(void)
-{
- static FGColumnVector vForce(3);
- static FGColumnVector vLocalForce(3);
- static FGColumnVector vLocalGear(3); // Vector: CG to this wheel (Local)
- static FGColumnVector vWhlBodyVec(3); // Vector: CG to this wheel (Body)
- static FGColumnVector vWhlVelVec(3); // Velocity of this wheel (Local)
+ if (sSteerType == "STEERABLE") eSteerType = stSteer;
+ else if (sSteerType == "FIXED" ) eSteerType = stFixed;
+ else if (sSteerType == "CASTERED" ) eSteerType = stCaster;
+ else {
+ cerr << "Improper steering type specification in config file: "
+ << sSteerType << " is undefined." << endl;
+ }
+
+ if ( sRetractable == "RETRACT" ) {
+ isRetractable = true;
+ } else {
+ isRetractable = false;
+ }
+
+ GearUp = false;
+ GearDown = true;
+
+// Add some AI here to determine if gear is located properly according to its
+// brake group type ??
- vWhlBodyVec = (vXYZ - Aircraft->GetXYZcg()) / 12.0;
+ State = Exec->GetState();
+ Aircraft = Exec->GetAircraft();
+ Position = Exec->GetPosition();
+ Rotation = Exec->GetRotation();
+ FCS = Exec->GetFCS();
+ MassBalance = Exec->GetMassBalance();
+
+ WOW = lastWOW = false;
+ ReportEnable = true;
+ FirstContact = false;
+ Reported = false;
+ DistanceTraveled = 0.0;
+ MaximumStrutForce = MaximumStrutTravel = 0.0;
+ SinkRate = GroundSpeed = 0.0;
+
+ vWhlBodyVec = (vXYZ - MassBalance->GetXYZcg()) / 12.0;
vWhlBodyVec(eX) = -vWhlBodyVec(eX);
vWhlBodyVec(eZ) = -vWhlBodyVec(eZ);
vLocalGear = State->GetTb2l() * vWhlBodyVec;
- compressLength = vLocalGear(eZ) - Position->GetDistanceAGL();
+ compressLength = 0.0;
+ compressSpeed = 0.0;
+ brakePct = 0.0;
+ maxCompLen = 0.0;
- if (compressLength > 0.00) {
+ Debug(0);
+}
- WOW = true;
+//%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
- vWhlVelVec = State->GetTb2l() * (Rotation->GetPQR() * vWhlBodyVec);
- vWhlVelVec += Position->GetVel();
- compressSpeed = vWhlVelVec(eZ);
+FGLGear::FGLGear(const FGLGear& lgear)
+{
+ State = lgear.State;
+ Aircraft = lgear.Aircraft;
+ Position = lgear.Position;
+ Rotation = lgear.Rotation;
+ 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;
+ DistanceTraveled = lgear.DistanceTraveled;
+ MaximumStrutForce = lgear.MaximumStrutForce;
+ MaximumStrutTravel = lgear.MaximumStrutTravel;
+
+ kSpring = lgear.kSpring;
+ bDamp = lgear.bDamp;
+ 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;
+ Reported = lgear.Reported;
+ name = lgear.name;
+ sSteerType = lgear.sSteerType;
+ sRetractable = lgear.sRetractable;
+ eSteerType = lgear.eSteerType;
+ sBrakeGroup = lgear.sBrakeGroup;
+ eBrakeGrp = lgear.eBrakeGrp;
+ maxSteerAngle = lgear.maxSteerAngle;
+ isRetractable = lgear.isRetractable;
+ GearUp = lgear.GearUp;
+ GearDown = lgear.GearDown;
+}
- vWhlVelVec = -1.0 * vWhlVelVec.Normalize();
- vWhlVelVec(eZ) = 0.00;
+//%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
- vLocalForce(eZ) = min(-compressLength * kSpring - compressSpeed * bDamp, (float)0.0);
- vLocalForce(eX) = fabs(vLocalForce(eZ) * statFCoeff) * vWhlVelVec(eX);
- vLocalForce(eY) = fabs(vLocalForce(eZ) * statFCoeff) * vWhlVelVec(eY);
+FGLGear::~FGLGear()
+{
+ Debug(1);
+}
- vForce = State->GetTl2b() * vLocalForce ;
- vMoment = vWhlBodyVec * vForce;
+//%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
+FGColumnVector3& FGLGear::Force(void)
+{
+ double SteerGain = 0;
+ double SinWheel, CosWheel;
+
+ vForce.InitMatrix();
+ vMoment.InitMatrix();
+
+ if (isRetractable) {
+ if (FCS->GetGearPos() < 0.01) {
+ GearUp = true;
+ GearDown = false;
+ } else if (FCS->GetGearPos() > 0.99) {
+ GearDown = true;
+ GearUp = false;
+ } else {
+ GearUp = false;
+ GearDown = false;
+ }
} else {
+ GearUp = false;
+ GearDown = true;
+ }
+
+ if (GearDown) {
+
+ vWhlBodyVec = (vXYZ - MassBalance->GetXYZcg()) / 12.0;
+ vWhlBodyVec(eX) = -vWhlBodyVec(eX);
+ vWhlBodyVec(eZ) = -vWhlBodyVec(eZ);
+
+// vWhlBodyVec now stores the vector from the cg to this wheel
+
+ vLocalGear = State->GetTb2l() * vWhlBodyVec;
+
+// vLocalGear now stores the vector from the cg to the wheel in local coords.
+
+ compressLength = vLocalGear(eZ) - Position->GetDistanceAGL();
+
+// The compression length is currently measured in the Z-axis, only, at this time.
+// It should be measured along the strut axis. If the local-frame gear position
+// "hangs down" below the CG greater than the altitude, then the compressLength
+// will be positive - i.e. the gear will have made contact.
+
+ if (compressLength > 0.00) {
+
+ WOW = true;// Weight-On-Wheels is true
+
+// The next equation should really use the vector to the contact patch of the tire
+// including the strut compression and not vWhlBodyVec. Will fix this later.
+// As it stands, now, the following equation takes the aircraft body-frame
+// rotational rate and calculates the cross-product with the vector from the CG
+// to the wheel, thus producing the instantaneous velocity vector of the tire
+// in Body coords. The frame is also converted to local coordinates. When the
+// aircraft local-frame velocity is added to this quantity, the total velocity of
+// the wheel in local frame is then known. Subsequently, the compression speed
+// (used for calculating damping force) is found by taking the Z-component of the
+// wheel velocity.
+
+ vWhlVelVec = State->GetTb2l() * (Rotation->GetPQR() * vWhlBodyVec);
+
+ vWhlVelVec += Position->GetVel();
+
+ compressSpeed = vWhlVelVec(eZ);
+
+// If this is the first time the wheel has made contact, remember some values
+// for later printout.
+
+ if (!FirstContact) {
+ FirstContact = true;
+ SinkRate = compressSpeed;
+ GroundSpeed = Position->GetVel().Magnitude();
+ }
+
+// The following needs work regarding friction coefficients and braking and
+// steering The BrakeFCoeff formula assumes that an anti-skid system is used.
+// It also assumes that we won't be turning and braking at the same time.
+// Will fix this later.
+// [JSB] The braking force coefficients include normal rolling coefficient +
+// a percentage of the static friction coefficient based on braking applied.
+
+ switch (eBrakeGrp) {
+ case bgLeft:
+ SteerGain = -0.10;
+ BrakeFCoeff = rollingFCoeff*(1.0 - FCS->GetBrake(bgLeft)) +
+ staticFCoeff*FCS->GetBrake(bgLeft);
+ break;
+ case bgRight:
+ SteerGain = -0.10;
+ BrakeFCoeff = rollingFCoeff*(1.0 - FCS->GetBrake(bgRight)) +
+ staticFCoeff*FCS->GetBrake(bgRight);
+ break;
+ case bgCenter:
+ SteerGain = -0.10;
+ BrakeFCoeff = rollingFCoeff*(1.0 - FCS->GetBrake(bgCenter)) +
+ staticFCoeff*FCS->GetBrake(bgCenter);
+ break;
+ case bgNose:
+ SteerGain = -0.50;
+ BrakeFCoeff = rollingFCoeff;
+ break;
+ case bgTail:
+ SteerGain = -0.10;
+ BrakeFCoeff = rollingFCoeff;
+ break;
+ case bgNone:
+ SteerGain = -0.10;
+ BrakeFCoeff = rollingFCoeff;
+ break;
+ default:
+ cerr << "Improper brake group membership detected for this gear." << endl;
+ break;
+ }
+
+ switch (eSteerType) {
+ case stSteer:
+ SteerAngle = SteerGain*FCS->GetDrPos();
+ break;
+ case stFixed:
+ SteerAngle = 0.0;
+ break;
+ case stCaster:
+// Note to Jon: This is not correct for castering gear. I'll fix it later.
+ SteerAngle = 0.0;
+ break;
+ default:
+ cerr << "Improper steering type membership detected for this gear." << endl;
+ break;
+ }
+
+// Transform the wheel velocities from the local axis system to the wheel axis system.
+// For now, steering angle is assumed to happen in the Local Z axis,
+// not the strut axis as it should be. Will fix this later.
+
+ SinWheel = sin(Rotation->Getpsi() + SteerAngle);
+ CosWheel = cos(Rotation->Getpsi() + SteerAngle);
+ RollingWhlVel = vWhlVelVec(eX)*CosWheel + vWhlVelVec(eY)*SinWheel;
+ SideWhlVel = vWhlVelVec(eY)*CosWheel - vWhlVelVec(eX)*SinWheel;
+
+// Calculate tire slip angle.
+
+ if (RollingWhlVel == 0.0 && SideWhlVel == 0.0) {
+ WheelSlip = 0.0;
+ } else {
+ WheelSlip = radtodeg*atan2(SideWhlVel, RollingWhlVel);
+ }
+
+// 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. Will fix this later.
+
+ if (fabs(WheelSlip) <= 10.0) {
+ FCoeff = staticFCoeff*WheelSlip/10.0;
+ } else {
+ FCoeff = dynamicFCoeff*fabs(WheelSlip)/WheelSlip;
+ }
+
+// Compute the vertical force on the wheel using square-law damping (per comment
+// in paper AIAA-2000-4303 - see header prologue comments). We might consider
+// allowing for both square and linear damping force calculation. Also need to
+// possibly give a "rebound damping factor" that differs from the compression
+// case.
+
+ vLocalForce(eZ) = min(-compressLength * kSpring
+ - compressSpeed * bDamp, (double)0.0);
+
+ MaximumStrutForce = max(MaximumStrutForce, fabs(vLocalForce(eZ)));
+ MaximumStrutTravel = max(MaximumStrutTravel, fabs(compressLength));
+
+// Compute the forces in the wheel ground plane.
+
+ RollingForce = 0;
+ if (fabs(RollingWhlVel) > 1E-3) {
+ RollingForce = vLocalForce(eZ) * BrakeFCoeff * fabs(RollingWhlVel)/RollingWhlVel;
+ }
+ 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;
+
+// Note to Jon: At this point the forces will be too big when the airplane is
+// stopped or rolling to a stop. We need to make sure that the gear forces just
+// balance out the non-gear forces when the airplane is stopped. That way the
+// airplane won't start to accelerate until the non-gear/ forces are larger than
+// the gear forces. I think that the proper fix should go into FGAircraft::FMGear.
+// This routine would only compute the local strut forces and return them to
+// FMGear. All of the gear forces would get adjusted in FMGear using the total
+// non-gear forces. Then the gear moments would be calculated. If strange things
+// start happening to the airplane during testing as it rolls to a stop, then we
+// need to implement this change. I ran out of time to do it now but have the
+// equations.
+
+// Transform the forces back to the body frame and compute the moment.
+
+ vForce = State->GetTl2b() * vLocalForce;
+ vMoment = vWhlBodyVec * vForce;
+
+ } else {
+
+ WOW = false;
+
+ if (Position->GetDistanceAGL() > 200.0) {
+ FirstContact = false;
+ Reported = false;
+ DistanceTraveled = 0.0;
+ MaximumStrutForce = MaximumStrutTravel = 0.0;
+ }
+
+ compressLength = 0.0; // reset compressLength to zero for data output validity
+ }
+
+ if (FirstContact) {
+ DistanceTraveled += Position->GetVel().Magnitude()*State->Getdt()*Aircraft->GetRate();
+ }
+
+ if (ReportEnable && Position->GetVel().Magnitude() <= 0.05 && !Reported) {
+ if (debug_lvl > 0) Report();
+ }
+
+ if (lastWOW != WOW) {
+ PutMessage("GEAR_CONTACT", WOW);
+ }
+
+ lastWOW = WOW;
+
+// Crash detection logic (really out-of-bounds detection)
+
+ if (compressLength > 500.0 ||
+ vForce.Magnitude() > 100000000.0 ||
+ vMoment.Magnitude() > 5000000000.0 ||
+ SinkRate > 1.4666*30)
+ {
+ PutMessage("Crash Detected: Simulation FREEZE.");
+ Exec->Freeze();
+ }
+ }
+ return vForce;
+}
- WOW = false;
- vForce.InitMatrix();
- vMoment.InitMatrix();
- }
-
+//%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
- return vForce;
+void FGLGear::Report(void)
+{
+ cout << endl << "Touchdown report for " << name << endl;
+ cout << " Sink rate at contact: " << SinkRate << " fps, "
+ << SinkRate*0.3408 << " mps" << endl;
+ cout << " Contact ground speed: " << GroundSpeed*.5925 << " knots, "
+ << GroundSpeed*0.3408 << " mps" << endl;
+ cout << " Maximum contact force: " << MaximumStrutForce << " lbs, "
+ << MaximumStrutForce*4.448 << " Newtons" << endl;
+ cout << " Maximum strut travel: " << MaximumStrutTravel*12.0 << " inches, "
+ << MaximumStrutTravel*30.48 << " cm" << endl;
+ cout << " Distance traveled: " << DistanceTraveled << " ft, "
+ << DistanceTraveled*0.3408 << " meters" << endl;
+ Reported = true;
}
-/******************************************************************************/
+//%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
+// The bitmasked value choices are as follows:
+// unset: In this case (the default) JSBSim would only print
+// out the normally expected messages, essentially echoing
+// the config files as they are read. If the environment
+// variable is not set, debug_lvl is set to 1 internally
+// 0: This requests JSBSim not to output any messages
+// whatsoever.
+// 1: This value explicity requests the normal JSBSim
+// startup messages
+// 2: This value asks for a message to be printed out when
+// a class is instantiated
+// 4: When this value is set, a message is displayed when a
+// FGModel object executes its Run() method
+// 8: When this value is set, various runtime state variables
+// are printed out periodically
+// 16: When set various parameters are sanity checked and
+// a message is printed out when they go out of bounds
+
+void FGLGear::Debug(int from)
+{
+ if (debug_lvl <= 0) return;
+
+ if (debug_lvl & 1) { // Standard console startup message output
+ if (from == 0) { // Constructor
+ cout << " Name: " << name << endl;
+ cout << " Location: " << vXYZ << endl;
+ cout << " Spring Constant: " << kSpring << endl;
+ cout << " Damping Constant: " << bDamp << endl;
+ cout << " Dynamic Friction: " << dynamicFCoeff << endl;
+ cout << " Static Friction: " << staticFCoeff << endl;
+ cout << " Rolling Friction: " << rollingFCoeff << endl;
+ cout << " Steering Type: " << sSteerType << endl;
+ cout << " Grouping: " << sBrakeGroup << endl;
+ cout << " Max Steer Angle: " << maxSteerAngle << endl;
+ cout << " Retractable: " << sRetractable << endl;
+ }
+ }
+ if (debug_lvl & 2 ) { // Instantiation/Destruction notification
+ if (from == 0) cout << "Instantiated: FGLGear" << endl;
+ if (from == 1) cout << "Destroyed: FGLGear" << endl;
+ }
+ if (debug_lvl & 4 ) { // Run() method entry print for FGModel-derived objects
+ }
+ if (debug_lvl & 8 ) { // Runtime state variables
+ }
+ if (debug_lvl & 16) { // Sanity checking
+ }
+ if (debug_lvl & 64) {
+ if (from == 0) { // Constructor
+ cout << IdSrc << endl;
+ cout << IdHdr << endl;
+ }
+ }
+}
projects / flightgear.git / blobdiff