src/FDM/JSBSim/FGLGear.cpp

   1 /*%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
   2
   3  Module:       FGLGear.cpp
   4  Author:       Jon S. Berndt
   5  Date started: 11/18/99
   6  Purpose:      Encapsulates the landing gear elements
   7  Called by:    FGAircraft
   8
   9  ------------- Copyright (C) 1999  Jon S. Berndt (jsb@hal-pc.org) -------------
  10
  11  This program is free software; you can redistribute it and/or modify it under
  12  the terms of the GNU General Public License as published by the Free Software
  13  Foundation; either version 2 of the License, or (at your option) any later
  14  version.
  15
  16  This program is distributed in the hope that it will be useful, but WITHOUT
  17  ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or FITNESS
  18  FOR A PARTICULAR PURPOSE.  See the GNU General Public License for more
  19  details.
  20
  21  You should have received a copy of the GNU General Public License along with
  22  this program; if not, write to the Free Software Foundation, Inc., 59 Temple
  23  Place - Suite 330, Boston, MA  02111-1307, USA.
  24
  25  Further information about the GNU General Public License can also be found on
  26  the world wide web at http://www.gnu.org.
  27
  28 FUNCTIONAL DESCRIPTION
  29 --------------------------------------------------------------------------------
  30
  31 HISTORY
  32 --------------------------------------------------------------------------------
  33 11/18/99   JSB   Created
  34
  35 %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
  36 INCLUDES
  37 %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%*/
  38
  39 #include "FGLGear.h"
  40 #include <algorithm>
  41
  42 /*%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
  43 DEFINITIONS
  44 %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%*/
  45
  46 /*%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
  47 GLOBAL DATA
  48 %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%*/
  49
  50 static const char *IdSrc = "$Header$";
  51 static const char *IdHdr = ID_LGEAR;
  52
  53 /*%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
  54 CLASS IMPLEMENTATION
  55 %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%*/
  56
  57 FGLGear::FGLGear(FGConfigFile* AC_cfg, FGFDMExec* fdmex) : vXYZ(3),
  58                                                            vMoment(3),
  59                                                            vWhlBodyVec(3),
  60                                                            Exec(fdmex)
  61 {
  62   string tmp;
  63   *AC_cfg >> tmp >> name >> vXYZ(1) >> vXYZ(2) >> vXYZ(3)
  64             >> kSpring >> bDamp>> dynamicFCoeff >> staticFCoeff
  65                   >> SteerType >> BrakeGroup >> maxSteerAngle;
  66
  67   cout << "    Name: " << name << endl;
  68   cout << "      Location: " << vXYZ << endl;
  69   cout << "      Spring Constant:  " << kSpring << endl;
  70   cout << "      Damping Constant: " << bDamp << endl;
  71   cout << "      Dynamic Friction: " << dynamicFCoeff << endl;
  72   cout << "      Static Friction:  " << staticFCoeff << endl;
  73   cout << "      Grouping:         " << BrakeGroup << endl;
  74   cout << "      Steering Type:    " << SteerType << endl;
  75   cout << "      Max Steer Angle:  " << maxSteerAngle << endl;
  76
  77   if      (BrakeGroup == "LEFT"  ) eBrakeGrp = bgLeft;
  78   else if (BrakeGroup == "RIGHT" ) eBrakeGrp = bgRight;
  79   else if (BrakeGroup == "CENTER") eBrakeGrp = bgCenter;
  80   else if (BrakeGroup == "NOSE"  ) eBrakeGrp = bgNose;
  81   else if (BrakeGroup == "TAIL"  ) eBrakeGrp = bgTail;
  82   else if (BrakeGroup == "NONE"  ) eBrakeGrp = bgNone;
  83   else {
  84     cerr << "Improper braking group specification in config file: "
  85          << BrakeGroup << " is undefined." << endl;
  86   }
  87
  88 // add some AI here to determine if gear is located properly according to its
  89 // brake group type
  90
  91   State       = Exec->GetState();
  92   Aircraft    = Exec->GetAircraft();
  93   Position    = Exec->GetPosition();
  94   Rotation    = Exec->GetRotation();
  95
  96   WOW = false;
  97   ReportEnable=true;
  98   FirstContact = false;
  99   Reported = false;
 100   DistanceTraveled = 0.0;
 101   MaximumStrutForce = MaximumStrutTravel = 0.0;
 102
 103   vWhlBodyVec     = (vXYZ - Aircraft->GetXYZcg()) / 12.0;
 104   vWhlBodyVec(eX) = -vWhlBodyVec(eX);
 105   vWhlBodyVec(eZ) = -vWhlBodyVec(eZ);
 106
 107   vLocalGear = State->GetTb2l() * vWhlBodyVec;
 108 }
 109
 110 //%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
 111
 112 FGLGear::FGLGear(const FGLGear& lgear)
 113 {
 114   State    = lgear.State;
 115   Aircraft = lgear.Aircraft;
 116   Position = lgear.Position;
 117   Rotation = lgear.Rotation;
 118   Exec     = lgear.Exec;
 119
 120   vXYZ = lgear.vXYZ;
 121   vMoment = lgear.vMoment;
 122   vWhlBodyVec = lgear.vWhlBodyVec;
 123   vLocalGear = lgear.vLocalGear;
 124
 125   WOW                = lgear.WOW;
 126   ReportEnable       = lgear.ReportEnable;
 127   FirstContact       = lgear.FirstContact;
 128   DistanceTraveled   = lgear.DistanceTraveled;
 129   MaximumStrutForce  = lgear.MaximumStrutForce;
 130   MaximumStrutTravel = lgear.MaximumStrutTravel;
 131
 132   kSpring         = lgear.kSpring;
 133   bDamp           = lgear.bDamp;
 134   compressLength  = lgear.compressLength;
 135   compressSpeed   = lgear.compressSpeed;
 136   staticFCoeff    = lgear.staticFCoeff;
 137   dynamicFCoeff   = lgear.dynamicFCoeff;
 138   brakePct        = lgear.brakePct;
 139   maxCompLen      = lgear.maxCompLen;
 140   SinkRate        = lgear.SinkRate;
 141   GroundSpeed     = lgear.GroundSpeed;
 142   Reported        = lgear.Reported;
 143   name            = lgear.name;
 144   SteerType       = lgear.SteerType;
 145   BrakeGroup      = lgear.BrakeGroup;
 146   eBrakeGrp       = lgear.eBrakeGrp;
 147   maxSteerAngle   = lgear.maxSteerAngle;
 148 }
 149
 150 //%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
 151
 152 FGLGear::~FGLGear(void) {}
 153
 154 //%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
 155
 156 FGColumnVector FGLGear::Force(void)
 157 {
 158   FGColumnVector vForce(3);
 159   FGColumnVector vLocalForce(3);
 160   //FGColumnVector vLocalGear(3);     // Vector: CG to this wheel (Local)
 161   FGColumnVector vWhlVelVec(3);     // Velocity of this wheel (Local)
 162
 163   vWhlBodyVec     = (vXYZ - Aircraft->GetXYZcg()) / 12.0;
 164   vWhlBodyVec(eX) = -vWhlBodyVec(eX);
 165   vWhlBodyVec(eZ) = -vWhlBodyVec(eZ);
 166
 167   vLocalGear = State->GetTb2l() * vWhlBodyVec;
 168
 169   compressLength = vLocalGear(eZ) - Position->GetDistanceAGL();
 170
 171   if (compressLength > 0.00) {
 172
 173     WOW = true;
 174     vWhlVelVec      =  State->GetTb2l() * (Rotation->GetPQR() * vWhlBodyVec);
 175     vWhlVelVec     +=  Position->GetVel();
 176
 177     compressSpeed   =  vWhlVelVec(eZ);
 178
 179     if (!FirstContact) {
 180       FirstContact  = true;
 181       SinkRate      =  compressSpeed;
 182       GroundSpeed   =  Position->GetVel().Magnitude();
 183     }
 184
 185     // The following code normalizes the wheel velocity vector, reverses it, and zeroes out
 186     // the z component of the velocity. The question is, should the Z axis velocity be zeroed
 187     // out first before the normalization takes place or not? Subsequent to that, the Wheel
 188     // Velocity vector now points as a unit vector backwards and parallel to the wheel
 189     // velocity vector. It acts AT the wheel.
 190
 191     vWhlVelVec      = -1.0 * vWhlVelVec.Normalize();
 192     vWhlVelVec(eZ)  =  0.00;
 193
 194 // the following needs work regarding friction coefficients and braking and steering
 195
 196     switch (eBrakeGrp) {
 197     case bgLeft:
 198
 199       break;
 200     case bgRight:
 201       break;
 202     case bgCenter:
 203       break;
 204     case bgNose:
 205       break;
 206     case bgTail:
 207       break;
 208     case bgNone:
 209       break;
 210     default:
 211       cerr << "Improper brake group membership detected for this gear." << endl;
 212       break;
 213     }
 214 //
 215
 216     vLocalForce(eZ) =  min(-compressLength * kSpring - compressSpeed * bDamp, (float)0.0);
 217     vLocalForce(eX) =  fabs(vLocalForce(eZ) * staticFCoeff) * vWhlVelVec(eX);
 218     vLocalForce(eY) =  fabs(vLocalForce(eZ) * staticFCoeff) * vWhlVelVec(eY);
 219
 220     MaximumStrutForce = max(MaximumStrutForce, fabs(vLocalForce(eZ)));
 221     MaximumStrutTravel = max(MaximumStrutTravel, fabs(compressLength));
 222
 223     vForce  = State->GetTl2b() * vLocalForce ;
 224     vMoment = vWhlBodyVec * vForce;
 225
 226   } else {
 227
 228     WOW = false;
 229
 230     if (Position->GetDistanceAGL() > 200.0) {
 231       FirstContact = false;
 232       Reported = false;
 233       DistanceTraveled = 0.0;
 234       MaximumStrutForce = MaximumStrutTravel = 0.0;
 235     }
 236
 237     vForce.InitMatrix();
 238     vMoment.InitMatrix();
 239   }
 240
 241   if (FirstContact) {
 242     DistanceTraveled += Position->GetVel().Magnitude()*State->Getdt()*Aircraft->GetRate();
 243   }
 244
 245   if (ReportEnable && Position->GetVel().Magnitude() <= 0.05 && !Reported) {
 246     Report();
 247   }
 248   return vForce;
 249 }
 250
 251 //%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
 252
 253 void FGLGear::Report(void)
 254 {
 255   cout << endl << "Touchdown report for " << name << endl;
 256   cout << "  Sink rate at contact:  " << SinkRate                << " fps,    "
 257                               << SinkRate*0.3408          << " mps"     << endl;
 258   cout << "  Contact ground speed:  " << GroundSpeed*.5925       << " knots,  "
 259                               << GroundSpeed*0.3408       << " mps"     << endl;
 260   cout << "  Maximum contact force: " << MaximumStrutForce       << " lbs,    "
 261                               << MaximumStrutForce*4.448  << " Newtons" << endl;
 262   cout << "  Maximum strut travel:  " << MaximumStrutTravel*12.0 << " inches, "
 263                               << MaximumStrutTravel*30.48 << " cm"      << endl;
 264   cout << "  Distance traveled:     " << DistanceTraveled        << " ft,     "
 265                               << DistanceTraveled*0.3408  << " meters"  << endl;
 266   Reported = true;
 267 }
 268