SUMO - Simulation of Urban MObility
 All Data Structures Namespaces Files Functions Variables Typedefs Enumerations Enumerator Friends Macros Groups Pages
MSCFModel_Krauss.cpp
Go to the documentation of this file.
1 /****************************************************************************/
11 // Krauss car-following model, with acceleration decrease and faster start
12 /****************************************************************************/
13 // SUMO, Simulation of Urban MObility; see http://sumo-sim.org/
14 // Copyright (C) 2001-2013 DLR (http://www.dlr.de/) and contributors
15 /****************************************************************************/
16 //
17 // This file is part of SUMO.
18 // SUMO is free software: you can redistribute it and/or modify
19 // it under the terms of the GNU General Public License as published by
20 // the Free Software Foundation, either version 3 of the License, or
21 // (at your option) any later version.
22 //
23 /****************************************************************************/
24 
25 
26 // ===========================================================================
27 // included modules
28 // ===========================================================================
29 #ifdef _MSC_VER
30 #include <windows_config.h>
31 #else
32 #include <config.h>
33 #endif
34 
35 #include <microsim/MSVehicle.h>
36 #include <microsim/MSLane.h>
37 #include <microsim/MSGlobals.h>
38 #include "MSCFModel_Krauss.h"
41 
42 
43 // ===========================================================================
44 // method definitions
45 // ===========================================================================
47  SUMOReal dawdle, SUMOReal headwayTime)
48  : MSCFModel_KraussOrig1(vtype, accel, decel, dawdle, headwayTime) {
49 }
50 
51 
53 
54 
56 MSCFModel_Krauss::followSpeed(const MSVehicle* const veh, const SUMOReal speed, SUMOReal gap, SUMOReal predSpeed, SUMOReal predMaxDecel) const {
57  return MIN2(_vsafe(gap, predSpeed, predMaxDecel), maxNextSpeed(speed, veh));
58 }
59 
60 
62 MSCFModel_Krauss::stopSpeed(const MSVehicle* const veh, const SUMOReal speed, SUMOReal gap) const {
63  return MIN2(_vsafe(gap, 0, 0), maxNextSpeed(speed, veh));
64 }
65 
66 
69  // generate random number out of [0,1]
70  SUMOReal random = RandHelper::rand();
71  // Dawdle.
72  if (speed < myAccel) {
73  // we should not prevent vehicles from driving just due to dawdling
74  // if someone is starting, he should definitely start
75  // (but what about slow-to-start?)!!!
76  speed -= ACCEL2SPEED(myDawdle * speed * random);
77  } else {
78  speed -= ACCEL2SPEED(myDawdle * myAccel * random);
79  }
80  return MAX2(SUMOReal(0), speed);
81 }
82 
83 
86 MSCFModel_Krauss::_vsafe(SUMOReal gap, SUMOReal predSpeed, SUMOReal predMaxDecel) const {
87  if (predSpeed < predMaxDecel) {
88  // avoid discretization error at low speeds
89  predSpeed = 0;
90  }
91  if (predSpeed == 0) {
92  if (gap < 0.01) {
93  return 0;
94  }
95  // g = t * x + x^2 / (2 * b)
96  const SUMOReal result = (SUMOReal)(-myTauDecel + sqrt(myTauDecel * myTauDecel + 2. * myDecel * gap));
97  assert(result >= 0);
98  return result;
99  }
100  if (gap < 0) {
101  gap = 0;
102  }
103  // follow the leader
104  // g=gap, t=myHeadwayTime, a=predMaxDecel, b=myDecel, v=predSpeed, x=vSafe
105  // Solution approach: equal distances after leader and follower have stopped (partly discretized).
106  // g + (v^2 - a*v)/(2*a) = x*t + (x^2 - b*x)/(2*b) + 0.5
107  // The term (+ 0.5) gives an upper bound for the follower stopping distance to handle discretization errors.
108  // Unfortunately, the solution approach is not correct when b > a since the
109  // follower path may cross the leader path even with equal stopping distances.
110  // As a workaround we lower the value of b to get a collision free model
111  // This approach should be refined to get a higher (still safe) following speed.
112  const SUMOReal egoDecel = MIN2(myDecel, predMaxDecel);
113  const SUMOReal result = (SUMOReal)(0.5 * sqrt(
114  4.0 * egoDecel * (2.0 * gap + predSpeed * predSpeed / predMaxDecel - predSpeed - 1.0)
115  + (egoDecel * (2.0 * myHeadwayTime - 1.0))
116  * (egoDecel * (2.0 * myHeadwayTime - 1.0)))
117  + egoDecel * (0.5 - myHeadwayTime));
118  // XXX recheck use of both branches of the quadratic forumula
119  if (ISNAN(result)) {
120  return 0;
121  } else {
122  return MAX2((SUMOReal)0, result);
123  }
124 }
125 
126 
127 MSCFModel*
129  return new MSCFModel_Krauss(vtype, myAccel, myDecel, myDawdle, myHeadwayTime);
130 }
131 
132 
133 //void MSCFModel::saveState(std::ostream &os) {}
134 
MSCFModel_Krauss(const MSVehicleType *vtype, SUMOReal accel, SUMOReal decel, SUMOReal dawdle, SUMOReal headwayTime)
Constructor.
Representation of a vehicle in the micro simulation.
Definition: MSVehicle.h:77
SUMOReal _vsafe(SUMOReal gap, SUMOReal predSpeed, SUMOReal predMaxDecel) const
Returns the &quot;safe&quot; velocity.
#define ACCEL2SPEED(x)
Definition: SUMOTime.h:61
virtual SUMOReal maxNextSpeed(SUMOReal speed, const MSVehicle *const veh) const
Returns the maximum speed given the current speed.
Definition: MSCFModel.cpp:86
The car-following model abstraction.
Definition: MSCFModel.h:58
SUMOReal myAccel
The vehicle&#39;s maximum acceleration [m/s^2].
Definition: MSCFModel.h:292
static SUMOReal rand()
Returns a random real number in [0, 1)
Definition: RandHelper.h:61
The original Krauss (1998) car-following model and parameter.
T MAX2(T a, T b)
Definition: StdDefs.h:63
~MSCFModel_Krauss()
Destructor.
SUMOReal stopSpeed(const MSVehicle *const veh, const SUMOReal speed, SUMOReal gap2pred) const
Computes the vehicle&#39;s safe speed for approaching a non-moving obstacle (no dawdling) ...
SUMOReal myHeadwayTime
The driver&#39;s desired time headway (aka reaction time tau) [s].
Definition: MSCFModel.h:298
SUMOReal myTauDecel
The precomputed value for myDecel*myTau.
The car-following model and parameter.
Definition: MSVehicleType.h:74
SUMOReal myDawdle
The vehicle&#39;s dawdle-parameter. 0 for no dawdling, 1 for max.
SUMOReal followSpeed(const MSVehicle *const veh, SUMOReal speed, SUMOReal gap2pred, SUMOReal predSpeed, SUMOReal predMaxDecel) const
Computes the vehicle&#39;s safe speed (no dawdling)
T MIN2(T a, T b)
Definition: StdDefs.h:57
T ISNAN(T a)
Definition: StdDefs.h:98
MSCFModel * duplicate(const MSVehicleType *vtype) const
Duplicates the car-following model.
SUMOReal dawdle(SUMOReal speed) const
Applies driver imperfection (dawdling / sigma)
#define SUMOReal
Definition: config.h:215
SUMOReal myDecel
The vehicle&#39;s maximum deceleration [m/s^2].
Definition: MSCFModel.h:295