src/FDM/YASim/Hitch.cpp

   1 #include "Math.hpp"
   2 #include "BodyEnvironment.hpp"
   3 #include "RigidBody.hpp"
   4 #include <string.h>
   5 #include <sstream>
   6
   7
   8
   9 #include "Hitch.hpp"
  10 namespace yasim {
  11 Hitch::Hitch(const char *name)
  12 {
  13     _node = fgGetNode("/sim/hitches", true)->getNode(name, true);
  14     int i;
  15     for(i=0; i<3; i++)
  16         _pos[i] = _force[i] = _winchPos[i] = _mp_lpos[i]=_towEndForce[i]=_mp_force[i]=0;
  17     for(i=0; i<2; i++)
  18         _global_ground[i] = 0;
  19     _global_ground[2] = 1;
  20     _global_ground[3] = -1e5;
  21     _forceMagnitude=0;
  22     _open=true;
  23     _oldOpen=_open;
  24     _towLength=60;
  25     _towElasticConstant=1e5;
  26     _towBrakeForce=100000;
  27     _towWeightPerM=1;
  28     _winchMaxSpeed=40;
  29     _winchRelSpeed=0;
  30     _winchInitialTowLength=1000;
  31     _winchPower=100000;
  32     _winchMaxForce=10000;
  33     _winchActualForce=0;
  34     _winchMaxTowLength=1000;
  35     _winchMinTowLength=0;
  36     _dist=0;
  37     _towEndIsConnectedToProperty=false;
  38     _towEndNode=0;
  39     _nodeIsMultiplayer=false;
  40     _nodeIsAiAircraft=false;
  41     _forceIsCalculatedByMaster=false;
  42     _nodeID=0;
  43     //_ai_MP_callsign=0;
  44     _height_above_ground=0;
  45     _winch_height_above_ground=0;
  46     _loPosFrac=0;
  47     _lowest_tow_height=0;
  48     _state=new State;
  49     _displayed_len_lower_dist_message=false;
  50     _last_wish=true;
  51     _isSlave=false;
  52     _mpAutoConnectPeriod=0;
  53     _timeToNextAutoConnectTry=0;
  54     _timeToNextReConnectTry=10;
  55     _speed_in_tow_direction=0;
  56     _mp_time_lag=1;
  57     _mp_last_reported_dist=0;
  58     _mp_last_reported_v=0;
  59     _mp_is_slave=false;
  60     _mp_open_last_state=false;
  61     _timeLagCorrectedDist=0;
  62
  63     _node->tie("tow/length",SGRawValuePointer<float>(&_towLength));
  64     _node->tie("tow/elastic-constant",SGRawValuePointer<float>(&_towElasticConstant));
  65     _node->tie("tow/weight-per-m-kg-m",SGRawValuePointer<float>(&_towWeightPerM));
  66     _node->tie("tow/brake-force",SGRawValuePointer<float>(&_towBrakeForce));
  67     _node->tie("winch/max-speed-m-s",SGRawValuePointer<float>(&_winchMaxSpeed));
  68     _node->tie("winch/rel-speed",SGRawValuePointer<float>(&_winchRelSpeed));
  69     _node->tie("winch/initial-tow-length-m",SGRawValuePointer<float>(&_winchInitialTowLength));
  70     _node->tie("winch/min-tow-length-m",SGRawValuePointer<float>(&_winchMinTowLength));
  71     _node->tie("winch/max-tow-length-m",SGRawValuePointer<float>(&_winchMaxTowLength));
  72     _node->tie("winch/global-pos-x",SGRawValuePointer<double>(&_winchPos[0]));
  73     _node->tie("winch/global-pos-y",SGRawValuePointer<double>(&_winchPos[1]));
  74     _node->tie("winch/global-pos-z",SGRawValuePointer<double>(&_winchPos[2]));
  75     _node->tie("winch/max-power",SGRawValuePointer<float>(&_winchPower));
  76     _node->tie("winch/max-force",SGRawValuePointer<float>(&_winchMaxForce));
  77     _node->tie("winch/actual-force",SGRawValuePointer<float>(&_winchActualForce));
  78     _node->tie("tow/end-force-x",SGRawValuePointer<float>(&_reportTowEndForce[0]));
  79     _node->tie("tow/end-force-y",SGRawValuePointer<float>(&_reportTowEndForce[1]));
  80     _node->tie("tow/end-force-z",SGRawValuePointer<float>(&_reportTowEndForce[2]));
  81     _node->tie("force",SGRawValuePointer<float>(&_forceMagnitude));
  82     _node->tie("open",SGRawValuePointer<bool>(&_open));
  83     _node->tie("force-is-calculated-by-other",SGRawValuePointer<bool>(&_forceIsCalculatedByMaster));
  84     _node->tie("local-pos-x",SGRawValuePointer<float>(&_pos[0]));
  85     _node->tie("local-pos-y",SGRawValuePointer<float>(&_pos[1]));
  86     _node->tie("local-pos-z",SGRawValuePointer<float>(&_pos[2]));
  87     _node->tie("tow/dist",SGRawValuePointer<float>(&_dist));
  88     _node->tie("tow/dist-time-lag-corrected",SGRawValuePointer<float>(&_timeLagCorrectedDist));
  89     _node->tie("tow/connected-to-property-node",SGRawValuePointer<bool>(&_towEndIsConnectedToProperty));
  90     _node->tie("tow/connected-to-mp-node",SGRawValuePointer<bool>(&_nodeIsMultiplayer));
  91     _node->tie("tow/connected-to-ai-node",SGRawValuePointer<bool>(&_nodeIsAiAircraft));
  92     _node->tie("tow/connected-to-ai-or-mp-id",SGRawValuePointer<int>(&_nodeID));
  93     _node->tie("debug/hitch-height-above-ground",SGRawValuePointer<float>(&_height_above_ground));
  94     _node->tie("debug/tow-end-height-above-ground",SGRawValuePointer<float>(&_winch_height_above_ground));
  95     _node->tie("debug/tow-rel-lo-pos",SGRawValuePointer<float>(&_loPosFrac));
  96     _node->tie("debug/tow-lowest-pos-height",SGRawValuePointer<float>(&_lowest_tow_height));
  97     _node->tie("is-slave",SGRawValuePointer<bool>(&_isSlave));
  98     _node->tie("speed-in-tow-direction",SGRawValuePointer<float>(&_speed_in_tow_direction));
  99     _node->tie("mp-auto-connect-period",SGRawValuePointer<float>(&_mpAutoConnectPeriod));
 100     _node->tie("mp-time-lag",SGRawValuePointer<float>(&_mp_time_lag));
 101     _node->setStringValue("tow/node","");
 102     _node->setStringValue("tow/connected-to-ai-or-mp-callsign");
 103     _node->setBoolValue("broken",false);
 104 }
 105
 106 Hitch::~Hitch()
 107 {
 108     _node->untie("tow/length");
 109     _node->untie("tow/elastic-constant");
 110     _node->untie("tow/weight-per-m-kg-m");
 111     _node->untie("tow/brake-force");
 112     _node->untie("winch/max-speed-m-s");
 113     _node->untie("winch/rel-speed");
 114     _node->untie("winch/initial-tow-length-m");
 115     _node->untie("winch/min-tow-length-m");
 116     _node->untie("winch/max-tow-length-m");
 117     _node->untie("winch/global-pos-x");
 118     _node->untie("winch/global-pos-y");
 119     _node->untie("winch/global-pos-z");
 120     _node->untie("winch/max-power");
 121     _node->untie("winch/max-force");
 122     _node->untie("winch/actual-force");
 123     _node->untie("tow/end-force-x");
 124     _node->untie("tow/end-force-y");
 125     _node->untie("tow/end-force-z");
 126     _node->untie("force");
 127     _node->untie("open");
 128     _node->untie("force-is-calculated-by-other");
 129     _node->untie("local-pos-x");
 130     _node->untie("local-pos-y");
 131     _node->untie("local-pos-z");
 132     _node->untie("tow/dist");
 133     _node->untie("tow/dist-time-lag-corrected");
 134     _node->untie("tow/connected-to-property-node");
 135     _node->untie("tow/connected-to-mp-node");
 136     _node->untie("tow/connected-to-ai-node");
 137     _node->untie("tow/connected-to-ai-or-mp-id");
 138     _node->untie("debug/hitch-height-above-ground");
 139     _node->untie("debug/tow-end-height-above-ground");
 140     _node->untie("debug/tow-rel-lo-pos");
 141     _node->untie("debug/tow-lowest-pos-height");
 142     _node->untie("is-slave");
 143     _node->untie("speed-in-tow-direction");
 144     _node->untie("mp-auto-connect-period");
 145     _node->untie("mp-time-lag");
 146
 147     delete _state;
 148 }
 149
 150 void Hitch::setPosition(float* position)
 151 {
 152     int i;
 153     for(i=0; i<3; i++) _pos[i] = position[i];
 154 }
 155
 156 void Hitch::setTowLength(float length)
 157 {
 158     _towLength = length;
 159 }
 160
 161 void Hitch::setOpen(bool isOpen)
 162 {
 163    //test if we already processed this before
 164     //without this test a binded property could
 165     //try to close the Hitch every run
 166     //it will close, if we are near the end
 167     //e.g. if we are flying over the parked
 168     //tow-aircraft....
 169     if (isOpen==_last_wish)
 170         return;
 171     _last_wish=isOpen;
 172     _open=isOpen;
 173 }
 174
 175 void Hitch::setTowElasticConstant(float sc)
 176 {
 177     _towElasticConstant=sc;
 178 }
 179
 180 void Hitch::setTowBreakForce(float bf)
 181 {
 182     _towBrakeForce=bf;
 183 }
 184
 185 void Hitch::setWinchMaxForce(float f)
 186 {
 187     _winchMaxForce=f;
 188 }
 189
 190 void Hitch::setTowWeightPerM(float rw)
 191 {
 192     _towWeightPerM=rw;
 193 }
 194
 195 void Hitch::setWinchMaxSpeed(float mws)
 196 {
 197     _winchMaxSpeed=mws;
 198 }
 199
 200 void Hitch::setWinchRelSpeed(float rws)
 201 {
 202     _winchRelSpeed=rws;
 203 }
 204
 205 void Hitch::setWinchPosition(double *winchPosition)//in global coordinates!
 206 {
 207     for (int i=0; i<3;i++)
 208         _winchPos[i]=winchPosition[i];
 209 }
 210
 211 void Hitch::setMpAutoConnectPeriod(float dt)
 212 {
 213     _mpAutoConnectPeriod=dt;
 214 }
 215
 216 void Hitch::setForceIsCalculatedByOther(bool b)
 217 {
 218     _forceIsCalculatedByMaster=b;
 219 }
 220
 221 const char *Hitch::getConnectedPropertyNode() const
 222 {
 223     if (_towEndNode)
 224         return _towEndNode->getDisplayName();
 225     else
 226         return 0;
 227 }
 228
 229 void Hitch::setConnectedPropertyNode(const char *nodename)
 230 {
 231     _towEndNode=fgGetNode(nodename,false);
 232 }
 233
 234 void Hitch::setWinchPositionAuto(bool doit)
 235 {
 236     static bool lastState=false;
 237     if(!_state)
 238         return;
 239     if (!doit)
 240     {
 241         lastState=false;
 242         return;
 243     }
 244     if(lastState)
 245         return;
 246     lastState=true;
 247     float lWinchPos[3];
 248     // The ground plane transformed to the local frame.
 249     float ground[4];
 250     _state->planeGlobalToLocal(_global_ground, ground);
 251
 252     float help[3];
 253     //find a normalized vector pointing forward parallel to the ground
 254     help[0]=0;
 255     help[1]=1;
 256     help[2]=0;
 257     Math::cross3(ground,help,help);
 258     //multiplay by initial tow length;
 259     //reduced by 1m to be able to close the
 260     //hitch either if the glider slips backwards a bit
 261     Math::mul3((_winchInitialTowLength-1.),help,help);
 262     //add to the actual pos
 263     Math::add3(_pos,help,lWinchPos);
 264     //put it onto the ground plane
 265     Math::mul3(ground[3],ground,help);
 266     Math::add3(lWinchPos,help,lWinchPos);
 267
 268     _state->posLocalToGlobal(lWinchPos,_winchPos);
 269     _towLength=_winchInitialTowLength;
 270     fgSetString("/sim/messages/pilot", "Connected to winch!");
 271     _open=false;
 272
 273     _node->setBoolValue("broken",false);
 274
 275     //set the dist value (if not, the hitch would open in the next calcforce run
 276     float delta[3];
 277     Math::sub3(lWinchPos,_pos,delta);
 278     _dist=Math::mag3(delta);
 279 }
 280
 281 void Hitch::findBestAIObject(bool doit,bool running_as_autoconnect)
 282 {
 283     static bool lastState=false;
 284     if(!_state)
 285         return;
 286     if (!running_as_autoconnect)
 287     {
 288         //if this function is binded to an input, it will be called every frame as long as the key is pressed.
 289         //therefore wait for a key-release before running it again.
 290         if (!doit)
 291         {
 292             lastState=false;
 293             return;
 294         }
 295         if(lastState)
 296             return;
 297         lastState=true;
 298     }
 299     double gpos[3];
 300     _state->posLocalToGlobal(_pos,gpos);
 301     double bestdist=_towLength*_towLength;//squared!
 302     _towEndIsConnectedToProperty=false;
 303     SGPropertyNode * ainode = fgGetNode("/ai/models",false);
 304     if(!ainode) return;
 305     char myCallsign[256]="***********";
 306     if (running_as_autoconnect)
 307     {
 308         //get own callsign
 309         SGPropertyNode *cs=fgGetNode("/sim/multiplay/callsign",false);
 310         if (cs)
 311         {
 312             strncpy(myCallsign,cs->getStringValue(),256);
 313             myCallsign[255]=0;
 314         }
 315         //reset tow length for search radius. Lentgh will be later copied from master
 316         _towLength=_winchInitialTowLength;
 317     }
 318     bool found=false;
 319     vector <SGPropertyNode_ptr> nodes;//<SGPropertyNode_ptr>
 320     for (int i=0;i<ainode->nChildren();i++)
 321     {
 322         SGPropertyNode * n=ainode->getChild(i);
 323         _nodeIsMultiplayer = strncmp("multiplayer",n->getName(),11)==0;
 324         _nodeIsAiAircraft = strncmp("aircraft",n->getName(),8)==0;
 325         if (!(_nodeIsMultiplayer || _nodeIsAiAircraft))
 326             continue;
 327         if (running_as_autoconnect)
 328         {
 329             if (!_nodeIsMultiplayer)
 330                 continue;
 331             if(n->getBoolValue("sim/hitches/aerotow/open",true)) continue;
 332             if(strncmp(myCallsign,n->getStringValue("sim/hitches/aerotow/tow/connected-to-ai-or-mp-callsign"),255)!=0)
 333                 continue;
 334         }
 335         double pos[3];
 336         pos[0]=n->getDoubleValue("position/global-x",0);
 337         pos[1]=n->getDoubleValue("position/global-y",0);
 338         pos[2]=n->getDoubleValue("position/global-z",0);
 339         double dist=0;
 340         for (int j=0;j<3;j++)
 341             dist+=(pos[j]-gpos[j])*(pos[j]-gpos[j]);
 342         if (dist<bestdist)
 343         {
 344             bestdist=dist;
 345             _towEndNode=n;
 346             _towEndIsConnectedToProperty=true;
 347             //_node->setStringValue("tow/node",n->getPath());
 348             _node->setStringValue("tow/node",n->getDisplayName());
 349             _nodeID=n->getIntValue("id",0);
 350             _node->setStringValue("tow/connected-to-ai-or-mp-callsign",n->getStringValue("callsign"));
 351             _open=false;
 352             found = true;
 353         }
 354     }
 355     if (found)
 356     {
 357         if (!running_as_autoconnect)
 358         {
 359             std::stringstream message;
 360             message<<_node->getStringValue("tow/connected-to-ai-or-mp-callsign")
 361                     <<", I am on your hook, distance "<<Math::sqrt(bestdist)<<" meter.";
 362             fgSetString("/sim/messages/pilot", message.str().c_str());
 363         }
 364         else
 365         {
 366             std::stringstream message;
 367             message<<_node->getStringValue("tow/connected-to-ai-or-mp-callsign")
 368                 <<": I am on your hook, distance "<<Math::sqrt(bestdist)<<" meter.";
 369             fgSetString("/sim/messages/ai-plane", message.str().c_str());
 370         }
 371         if (running_as_autoconnect)
 372             _isSlave=true;
 373         //set the dist value to some value below the tow lentgh (if not, the hitch
 374         //would open in the next calc force run
 375         _dist=_towLength*0.5;
 376         _mp_open_last_state=true;
 377     }
 378     else
 379         if (!running_as_autoconnect)
 380         {
 381             fgSetString("/sim/messages/atc", "Sorry, no aircraft for aerotow!");
 382         }
 383 }
 384
 385 void Hitch::setWinchInitialTowLength(float length)
 386 {
 387     _winchInitialTowLength=length;
 388 }
 389
 390 void Hitch::setWinchPower(float power)
 391 {
 392     _winchPower=power;
 393 }
 394
 395 void Hitch::setWinchMaxTowLength(float length)
 396 {
 397     _winchMaxTowLength=length;
 398 }
 399
 400 void Hitch::setWinchMinTowLength(float length)
 401 {
 402     _winchMinTowLength=length;
 403 }
 404
 405 void Hitch::setGlobalGround(double *global_ground, float *global_vel)
 406 {
 407     int i;
 408     for(i=0; i<4; i++) _global_ground[i] = global_ground[i];
 409     for(i=0; i<3; i++) _global_vel[i] = global_vel[i];
 410 }
 411
 412 void Hitch::getPosition(float* out)
 413 {
 414     int i;
 415     for(i=0; i<3; i++) out[i] = _pos[i];
 416 }
 417
 418 float Hitch::getTowLength(void)
 419 {
 420     return _towLength;
 421 }
 422
 423 void Hitch::calcForce(Ground *g_cb, RigidBody* body, State* s)
 424 {
 425     float lWinchPos[3],delta[3],deltaN[3];
 426     *_state=*s;
 427     s->posGlobalToLocal(_winchPos,lWinchPos);
 428     Math::sub3(lWinchPos,_pos,delta);
 429     if(!_towEndIsConnectedToProperty)
 430         _dist=Math::mag3(delta);
 431     else
 432         _dist=Math::mag3(lWinchPos); //use the aircraft center as reference for distance calculation
 433                                   //this position is transferred to the MP-Aircraft.
 434                                   //With this trick, both player in aerotow get the same length
 435     Math::unit3(delta,deltaN);
 436     float lvel[3];
 437     s->velGlobalToLocal(s->v,lvel);
 438     _speed_in_tow_direction=Math::dot3(lvel,deltaN);
 439     if (_towEndIsConnectedToProperty && _nodeIsMultiplayer)
 440     {
 441         float mp_delta_dist_due_to_time_lag=0.5*_mp_time_lag*(-_mp_v+_speed_in_tow_direction);
 442         _timeLagCorrectedDist=_dist+mp_delta_dist_due_to_time_lag;
 443         if(_forceIsCalculatedByMaster && !_open)
 444         {
 445             s->velGlobalToLocal(_mp_force,_force);
 446             return;
 447         }
 448     }
 449     else
 450         _timeLagCorrectedDist=_dist;
 451     if (_open)
 452     {
 453         _force[0]=_force[1]=_force[2]=0;
 454         return;
 455     }
 456     if(_dist>_towLength)
 457         if(_towLength>1e-3)
 458             _forceMagnitude=(_dist-_towLength)/_towLength*_towElasticConstant;
 459         else
 460             _forceMagnitude=2*_towBrakeForce;
 461     else
 462         _forceMagnitude=0;
 463     if(_forceMagnitude>=_towBrakeForce)
 464     {
 465         _forceMagnitude=0;
 466         _open=true;
 467         _node->setBoolValue("broken",true);
 468         _force[0]=_force[1]=_force[2]=0;
 469         _towEndForce[0]=_towEndForce[1]=_towEndForce[2]=0;
 470         _reportTowEndForce[0]=_reportTowEndForce[1]=_reportTowEndForce[2]=0;
 471         return;
 472     }
 473     Math::mul3(_forceMagnitude,deltaN,_force);
 474     Math::mul3(-1.,_force,_towEndForce);
 475     _winchActualForce=_forceMagnitude; //missing: gravity on this end and friction
 476     //Add the gravitiy of the rope.
 477     //calculate some numbers:
 478     float grav_force=_towWeightPerM*_towLength*9.81;
 479     //the length of the gravity-expanded row:
 480     float leng=_towLength+grav_force*_towLength/_towElasticConstant;
 481     // The ground plane transformed to the local frame.
 482     float ground[4];
 483     s->planeGlobalToLocal(_global_ground, ground);
 484
 485     // The velocity of the contact patch transformed to local coordinates.
 486     //float glvel[3];
 487     //s->velGlobalToLocal(_global_vel, glvel);
 488
 489     _height_above_ground = ground[3] - Math::dot3(_pos, ground);
 490
 491     //the same for the winch-pos (the pos of the tow end)
 492     _winch_height_above_ground = ground[3] - Math::dot3(lWinchPos, ground);
 493
 494     //the frac of the grav force acting on _pos:
 495     float grav_frac=0.5*(1+(_height_above_ground-_winch_height_above_ground)/leng);
 496     grav_frac=Math::clamp(grav_frac,0,1);
 497     float grav_frac_tow_end=1-grav_frac;
 498     //reduce grav_frac, if the tow has ground contact.
 499     if (_height_above_ground<leng) //if not, the tow can not be on ground
 500     {
 501         float fa[3],fb[3],fg[3];
 502         //the grav force an the hitch position:
 503         Math::mul3(-grav_frac*grav_force,ground,fg);
 504         //the total force on hitch postion:
 505         Math::add3(fg,_force,fa);
 506         //the grav force an the tow end position:
 507         Math::mul3(-(1-grav_frac)*grav_force,ground,fg);
 508         //the total force on tow end postion:
 509         //note: sub: _force on tow-end is negative of force on hitch postion
 510         Math::sub3(fg,_force,fb);
 511         float fa_=Math::mag3(fa);
 512         float fb_=Math::mag3(fb);
 513         float stretchedTowLen;
 514         stretchedTowLen=_towLength*(1.+(fa_+fb_)/(2*_towElasticConstant));
 515         //the relative position of the lowest postion of the tow:
 516         if ((fa_+fb_)>1e-3)
 517             _loPosFrac=fa_/(fa_+fb_);
 518         else
 519             _loPosFrac=0.5;
 520         //dist to tow-end parallel to ground
 521         float ground_dist;
 522         float help[3];
 523         //Math::cross3(delta,ground,help);//as long as we calculate the dist without _pos, od it with lWinchpos, the dist to our center....
 524         Math::cross3(lWinchPos,ground,help);
 525         ground_dist=Math::mag3(help);
 526         //height of lowest tow pos (relative to _pos)
 527         _lowest_tow_height=_loPosFrac*Math::sqrt(Math::abs(stretchedTowLen*stretchedTowLen-ground_dist*ground_dist));
 528         if (_height_above_ground<_lowest_tow_height)
 529         {
 530             if (_height_above_ground>1e-3)
 531                 grav_frac*=_height_above_ground/_lowest_tow_height;
 532             else
 533                 grav_frac=0;
 534         }
 535         if (_winch_height_above_ground<(_lowest_tow_height-_height_above_ground+_winch_height_above_ground))
 536         {
 537             if (_winch_height_above_ground>1e-3)
 538                 grav_frac_tow_end*=_winch_height_above_ground/
 539                     (_lowest_tow_height-_height_above_ground+_winch_height_above_ground);
 540             else
 541                 grav_frac_tow_end=0;
 542         }
 543     }
 544     else _lowest_tow_height=_loPosFrac=-1; //for debug output
 545     float grav_force_v[3];
 546     Math::mul3(grav_frac*grav_force,ground,grav_force_v);
 547     Math::add3(grav_force_v,_force,_force);
 548     _forceMagnitude=Math::mag3(_force);
 549     //the same for the tow end:
 550     Math::mul3(grav_frac_tow_end*grav_force,ground,grav_force_v);
 551     Math::add3(grav_force_v,_towEndForce,_towEndForce);
 552     s->velLocalToGlobal(_towEndForce,_towEndForce);
 553
 554     if(_forceMagnitude>=_towBrakeForce)
 555     {
 556         _forceMagnitude=0;
 557         _open=true;
 558         _node->setBoolValue("broken",true);
 559         _force[0]=_force[1]=_force[2]=0;
 560         _towEndForce[0]=_towEndForce[1]=_towEndForce[2]=0;
 561     }
 562
 563
 564 }
 565
 566 // Computed values: total force
 567 void Hitch::getForce(float* force, float* off)
 568 {
 569     Math::set3(_force, force);
 570     Math::set3(_pos, off);
 571 }
 572
 573 void Hitch::integrate (float dt)
 574 {
 575     //check if hitch has opened or closed, if yes: message
 576     if (_open !=_oldOpen)
 577     {
 578         if (_oldOpen)
 579         {
 580             if (_dist>_towLength*1.00001)
 581             {
 582                 std::stringstream message;
 583                 message<<"Could not lock hitch (tow length is insufficient) on hitch "
 584                        <<_node->getName()<<" "<<_node->getIndex()<<"!";
 585                 fgSetString("/sim/messages/pilot", message.str().c_str());
 586                 _open=true;
 587                 return;
 588             }
 589             _node->setBoolValue("broken",false);
 590         }
 591         std::stringstream message;
 592         if (_node->getBoolValue("broken",false)&&_open)
 593             message<<"Oh no, the tow is broken";
 594         else
 595             message<<(_open?"Opened hitch ":"Locked hitch ")<<_node->getName()<<" "<<_node->getIndex()<<"!";
 596         fgSetString("/sim/messages/pilot", message.str().c_str());
 597         _oldOpen=_open;
 598     }
 599
 600     //check, if tow end should be searched in all MP-aircrafts
 601     if(_open && _mpAutoConnectPeriod)
 602     {
 603         _isSlave=false;
 604         _timeToNextAutoConnectTry-=dt;
 605         if ((_timeToNextAutoConnectTry>_mpAutoConnectPeriod) || (_timeToNextAutoConnectTry<0))
 606         {
 607             _timeToNextAutoConnectTry=_mpAutoConnectPeriod;
 608             //search for MP-Aircraft, which is towed with us
 609             findBestAIObject(true,true);
 610         }
 611     }
 612     //check, if tow end can be modified by property, if yes: update
 613     if(_towEndIsConnectedToProperty)
 614     {
 615         if (_node)
 616         {
 617             //_towEndNode=fgGetNode(_node->getStringValue("tow/node"), false);
 618             char towNode[256];
 619             strncpy(towNode,_node->getStringValue("tow/node"),256);
 620             towNode[255]=0;
 621             _towEndNode=fgGetNode("ai/models")->getNode(towNode, false);
 622             //AI and multiplayer objects seem to change node?
 623             //Check if we have the right one by callsign
 624             if (_nodeIsMultiplayer || _nodeIsAiAircraft)
 625             {
 626                 char MPcallsign[256]="";
 627                 const char *MPc;
 628                 MPc=_node->getStringValue("tow/connected-to-ai-or-mp-callsign");
 629                 if (MPc)
 630                 {
 631                     strncpy(MPcallsign,MPc,256);
 632                     MPcallsign[255]=0;
 633                 }
 634                 if (((_towEndNode)&&(strncmp(_towEndNode->getStringValue("callsign"),MPcallsign,255)!=0))||!_towEndNode)
 635                 {
 636                     _timeToNextReConnectTry-=dt;
 637                     if((_timeToNextReConnectTry<0)||(_timeToNextReConnectTry>10))
 638                     {
 639                         _timeToNextReConnectTry=10;
 640                         SGPropertyNode * ainode = fgGetNode("/ai/models",false);
 641                         if(ainode)
 642                         {
 643                             for (int i=0;i<ainode->nChildren();i++)
 644                             {
 645                                 SGPropertyNode * n=ainode->getChild(i);
 646                                 if(_nodeIsMultiplayer?strncmp("multiplayer",n->getName(),11)==0:strncmp("aircraft",n->getName(),8))
 647                                     if (strcmp(n->getStringValue("callsign"),MPcallsign)==0)//found
 648                                     {
 649                                         _towEndNode=n;
 650                                         //_node->setStringValue("tow/node",n->getPath());
 651                                         _node->setStringValue("tow/node",n->getDisplayName());
 652                                     }
 653                             }
 654                         }
 655                     }
 656                 }
 657             }
 658             if(_towEndNode)
 659             {
 660                 _winchPos[0]=_towEndNode->getDoubleValue("position/global-x",_winchPos[0]);
 661                 _winchPos[1]=_towEndNode->getDoubleValue("position/global-y",_winchPos[1]);
 662                 _winchPos[2]=_towEndNode->getDoubleValue("position/global-z",_winchPos[2]);
 663                 _mp_lpos[0]=_towEndNode->getFloatValue("sim/hitches/aerotow/local-pos-x",0);
 664                 _mp_lpos[1]=_towEndNode->getFloatValue("sim/hitches/aerotow/local-pos-y",0);
 665                 _mp_lpos[2]=_towEndNode->getFloatValue("sim/hitches/aerotow/local-pos-z",0);
 666                 _mp_dist=_towEndNode->getFloatValue("sim/hitches/aerotow/tow/dist");
 667                 _mp_v=_towEndNode->getFloatValue("sim/hitches/aerotow/speed-in-tow-direction");
 668                 _mp_force[0]=_towEndNode->getFloatValue("sim/hitches/aerotow/tow/end-force-x",0);
 669                 _mp_force[1]=_towEndNode->getFloatValue("sim/hitches/aerotow/tow/end-force-y",0);
 670                 _mp_force[2]=_towEndNode->getFloatValue("sim/hitches/aerotow/tow/end-force-z",0);
 671
 672                 if(_isSlave)
 673                 {
 674 #define gf(a,b) a=_towEndNode->getFloatValue(b,a)
 675 #define gb(a,b) a=_towEndNode->getBoolValue(b,a)
 676                     gf(_towLength,"sim/hitches/aerotow/tow/length");
 677                     gf(_towElasticConstant,"sim/hitches/aerotow/tow/elastic-constant");
 678                     gf(_towWeightPerM,"sim/hitches/aerotow/tow/weight-per-m-kg-m");
 679                     gf(_towBrakeForce,"sim/hitches/aerotow/brake-force");
 680                     gb(_open,"sim/hitches/aerotow/open");
 681                     gb(_mp_is_slave,"sim/hitches/aerotow/is-slave");
 682 #undef gf
 683 #undef gb
 684                     if (_mp_is_slave) _isSlave=false; //someone should be master
 685                 }
 686                 else
 687                 {
 688                     //check if other has opened hitch, but is neccessary, that it was closed before
 689                     bool mp_open=_towEndNode->getBoolValue("sim/hitches/aerotow/open",_mp_open_last_state);
 690                     if (mp_open != _mp_open_last_state) //state has changed
 691                     {
 692                         _mp_open_last_state=mp_open; //store that value
 693                         if(!_open)
 694                         {
 695                             if(mp_open)
 696                             {
 697                                 _oldOpen=_open=true;
 698                                 std::stringstream message;
 699                                 message<<_node->getStringValue("tow/connected-to-ai-or-mp-callsign")
 700                                     <<": I have released the tow!";
 701                                 fgSetString("/sim/messages/ai-plane", message.str().c_str());
 702                             }
 703                         }
 704                     }
 705                 }
 706                 //try to calculate the time lag
 707                 if ((_mp_last_reported_dist!=_mp_dist)||(_mp_last_reported_v!=_mp_v)) //new data;
 708                 {
 709                     _mp_last_reported_dist=_mp_dist;
 710                     _mp_last_reported_v=_mp_v;
 711                     float total_v=-_mp_v+_speed_in_tow_direction;//mp has opposite tow direction
 712                     float abs_v=Math::abs(total_v);
 713                     if (abs_v>0.1)
 714                     {
 715                         float actual_time_lag_guess=(_mp_dist-_dist)/total_v;
 716                         //check, if it sounds ok
 717                         if((actual_time_lag_guess>0)&&(actual_time_lag_guess<5))
 718                         {
 719                             float frac=abs_v*0.01;
 720                             if (frac>0.05) frac=0.05;
 721                             // if we are slow, the guess of the lag can be rather wrong. as faster we are
 722                             // the better the guess. Therefore frac is proportiona to the speed. Clamp it
 723                             // at 5m/s
 724                             _mp_time_lag=(1-frac)*_mp_time_lag+frac*actual_time_lag_guess;
 725                         }
 726                     }
 727                 }
 728             }
 729         }
 730     }
 731     //set the _reported_tow_end_force (smoothed)
 732     //smooth it a bit and store it
 733     float sc=10.*dt; //100ms
 734     float tmp[3];
 735     Math::mul3(sc,_towEndForce,tmp);
 736     Math::mul3(1.-sc,_reportTowEndForce,_reportTowEndForce);
 737     Math::add3(tmp,_reportTowEndForce,_reportTowEndForce);
 738
 739     if (_open) return;
 740     if (_winchRelSpeed==0) return;
 741     float factor=1,offset=0;
 742     if (_winchActualForce>_winchMaxForce)
 743         offset=-(_winchActualForce-_winchMaxForce)/_winchMaxForce*20;
 744     if (_winchRelSpeed>0.01) // to avoit div by zero
 745     {
 746         float maxForcePowerLimit=_winchPower/(_winchRelSpeed*_winchMaxSpeed);
 747         if (_winchActualForce>maxForcePowerLimit)
 748             factor-=(_winchActualForce-maxForcePowerLimit)/maxForcePowerLimit;
 749     }
 750     _towLength-=dt*(factor*_winchRelSpeed+offset)*_winchMaxSpeed;
 751     if (_towLength<=_winchMinTowLength)
 752     {
 753         if (_winchRelSpeed<0)
 754             _winchRelSpeed=0;
 755         _towLength=_winchMinTowLength;
 756         return;
 757     }
 758     if (_towLength>=_winchMaxTowLength)
 759     {
 760         if (_winchRelSpeed<0)
 761             _winchRelSpeed=0;
 762         _towLength=_winchMaxTowLength;
 763         return;
 764     }
 765 }
 766
 767
 768
 769
 770 }; // namespace yasim