IDM.java
package org.opentrafficsim.core.gtu.following;
import org.opentrafficsim.core.unit.AccelerationUnit;
import org.opentrafficsim.core.unit.LengthUnit;
import org.opentrafficsim.core.unit.SpeedUnit;
import org.opentrafficsim.core.unit.TimeUnit;
import org.opentrafficsim.core.value.conversions.Calc;
import org.opentrafficsim.core.value.vdouble.scalar.DoubleScalar;
import org.opentrafficsim.core.value.vdouble.scalar.MutableDoubleScalar;
/**
* The Intelligent Driver Model by Treiber, Hennecke and Helbing.
* <p>
* Copyright (c) 2013-2014 Delft University of Technology, PO Box 5, 2600 AA, Delft, the Netherlands. All rights
* reserved. <br>
* BSD-style license. See <a href="http://opentrafficsim.org/node/13">OpenTrafficSim License</a>.
* <p>
* @version 19 nov. 2014 <br>
* @author <a href="http://www.tudelft.nl/pknoppers">Peter Knoppers</a>
*/
public class IDM extends AbstractGTUFollowingModel
{
/** Preferred net longitudinal distance when stopped [m]. */
private final DoubleScalar.Rel<LengthUnit> s0;
/** Maximum longitudinal acceleration [m/s^2]. */
private final DoubleScalar.Abs<AccelerationUnit> a;
/** Longitudinal deceleration [m/s^2]. (Should be a positive value even though it is a <b>de</b>celeration.) */
private final DoubleScalar.Abs<AccelerationUnit> b;
/** Safe time headway. */
private final DoubleScalar.Rel<TimeUnit> tSafe;
/**
* Time slot size used by IDM (not defined in the paper, but 0.5s is a reasonable trade-off between computational
* speed and accuracy).
*/
private final DoubleScalar.Rel<TimeUnit> stepSize = new DoubleScalar.Rel<TimeUnit>(0.5, TimeUnit.SECOND);
/**
* Mean speed limit adherence (1.0: mean free speed equals the speed limit; 1.1: mean speed limit equals 110% of the
* speed limit, etc.).
*/
private final double delta;
/**
* Construct a new IDM car following model with reasonable values (reasonable for passenger cars).
*/
public IDM()
{
this.a = new DoubleScalar.Abs<AccelerationUnit>(1.56, AccelerationUnit.METER_PER_SECOND_2);
this.b = new DoubleScalar.Abs<AccelerationUnit>(2.09, AccelerationUnit.METER_PER_SECOND_2);
this.s0 = new DoubleScalar.Rel<LengthUnit>(3, LengthUnit.METER);
this.tSafe = new DoubleScalar.Rel<TimeUnit>(1.2, TimeUnit.SECOND);
this.delta = 1d;
}
/**
* Construct a new IDM car following model.
* @param a DoubleScalar.Abs<AccelerationUnit>; the maximum acceleration of a stationary vehicle (normal value
* is 1 m/s/s)
* @param b DoubleScalar.Abs<AccelerationUnit>; the maximum deemed-safe deceleration (this is a positive
* value). Normal value is 1.5 m/s/s.
* @param s0 DoubleScalar.Rel<LengthUnit>; the minimum stationary headway (normal value is 2 m)
* @param tSafe DoubleScalar.Rel<TimeUnit>; the minimum time-headway (normal value is 1s)
* @param delta double; the speed limit adherence (1.0; mean free speed equals the speed limit; 1.1: mean free speed
* equals 110% of the speed limit; etc.)
*/
public IDM(final DoubleScalar.Abs<AccelerationUnit> a, final DoubleScalar.Abs<AccelerationUnit> b,
final DoubleScalar.Rel<LengthUnit> s0, final DoubleScalar.Rel<TimeUnit> tSafe, final double delta)
{
this.a = a;
this.b = b;
this.s0 = s0;
this.tSafe = tSafe;
this.delta = delta;
}
/**
* Desired speed (taking into account the urge to drive a little faster or slower than the posted speed limit).
* @param speedLimit DoubleScalarAbs<SpeedUnit>; the speed limit
* @param followerMaximumSpeed DoubleScalar.Abs<SpeedUnit>; the maximum speed that the follower can drive
* @return DoubleScalarRel<SpeedUnit>; the desired speed
*/
private DoubleScalar.Rel<SpeedUnit> vDes(final DoubleScalar.Abs<SpeedUnit> speedLimit,
final DoubleScalar.Abs<SpeedUnit> followerMaximumSpeed)
{
return new DoubleScalar.Rel<SpeedUnit>(Math.min(this.delta * speedLimit.getSI(), followerMaximumSpeed.getSI()),
SpeedUnit.METER_PER_SECOND);
}
/** {@inheritDoc} */
public final DoubleScalar.Abs<AccelerationUnit> computeAcceleration(
final DoubleScalar.Abs<SpeedUnit> followerSpeed, final DoubleScalar.Abs<SpeedUnit> followerMaximumSpeed,
final DoubleScalar.Abs<SpeedUnit> leaderSpeed, final DoubleScalar.Rel<LengthUnit> headway,
final DoubleScalar.Abs<SpeedUnit> speedLimit)
{
// System.out.println("Applying IDM for " + follower + " headway is " + headway);
// dV is the approach speed
DoubleScalar.Rel<SpeedUnit> dV = DoubleScalar.minus(followerSpeed, leaderSpeed).immutable();
DoubleScalar.Abs<AccelerationUnit> aFree =
new DoubleScalar.Abs<AccelerationUnit>(this.a.getSI()
* (1 - Math.pow(followerSpeed.getSI() / vDes(speedLimit, followerMaximumSpeed).getSI(), 4)),
AccelerationUnit.METER_PER_SECOND_2);
if (Double.isNaN(aFree.getSI()))
{
aFree = new DoubleScalar.Abs<AccelerationUnit>(0, AccelerationUnit.SI);
}
MutableDoubleScalar.Rel<AccelerationUnit> logWeightedAccelerationTimes2 =
new MutableDoubleScalar.Rel<AccelerationUnit>(Math.sqrt(this.a.getSI() * this.b.getSI()),
AccelerationUnit.METER_PER_SECOND_2);
logWeightedAccelerationTimes2.multiply(2); // don't forget the times 2
// TODO compute logWeightedAccelerationTimes2 only once per run
/*
* DoubleScalar.Rel<LengthUnit> sStar = DoubleScalar.plus( DoubleScalar.plus(this.s0,
* Calc.speedTimesTime(follower.getLongitudinalVelocity(thisEvaluationTime), this.tSafe)) .immutable(),
* Calc.speedTimesTime( dV, Calc.speedDividedByAcceleration(followerCurrentSpeed,
* logWeightedAccelerationTimes2.immutable()))).immutable();
*/
DoubleScalar.Rel<LengthUnit> right =
DoubleScalar.plus(
Calc.speedTimesTime(followerSpeed, this.tSafe),
Calc.speedTimesTime(
dV,
Calc.speedDividedByAcceleration(followerSpeed,
logWeightedAccelerationTimes2.immutable()))).immutable();
if (right.getSI() < 0)
{
// System.out.println("Fixing negative right");
right = new DoubleScalar.Rel<LengthUnit>(0, LengthUnit.METER);
}
DoubleScalar.Rel<LengthUnit> sStar = DoubleScalar.plus(this.s0, right).immutable();
if (sStar.getSI() < 0) // Negative value should be treated as 0
{
System.out.println("sStar is negative");
sStar = new DoubleScalar.Rel<LengthUnit>(0, LengthUnit.METER);
}
// System.out.println("s* is " + sStar);
DoubleScalar.Rel<AccelerationUnit> aInteraction =
new DoubleScalar.Rel<AccelerationUnit>(-Math.pow(this.a.getSI() * sStar.getSI() / headway.getSI(), 2),
AccelerationUnit.METER_PER_SECOND_2);
DoubleScalar.Abs<AccelerationUnit> newAcceleration = DoubleScalar.plus(aFree, aInteraction).immutable();
if (newAcceleration.getSI() * this.stepSize.getSI() + followerSpeed.getSI() < 0)
{
// System.out.println("Limiting deceleration to prevent moving backwards");
newAcceleration =
new DoubleScalar.Abs<AccelerationUnit>(-followerSpeed.getSI() / this.stepSize.getSI(),
AccelerationUnit.METER_PER_SECOND_2);
}
// System.out.println("newAcceleration is " + newAcceleration);
return newAcceleration;
}
/** {@inheritDoc} */
@Override
public final DoubleScalar.Rel<TimeUnit> getStepSize()
{
return new DoubleScalar.Rel<TimeUnit>(this.stepSize);
}
/** {@inheritDoc} */
@Override
public final DoubleScalar.Abs<AccelerationUnit> maximumSafeDeceleration()
{
return this.b;
}
/** {@inheritDoc} */
@Override
public final String getName()
{
return "IDM";
}
/** {@inheritDoc} */
@Override
public final String getLongName()
{
return String.format("%s (a=%.1fm/s\u00b2, b=%.1fm/s\u00b2, s0=%.1fm, tSafe=%.1fs, delta=%.2f)", getName(),
this.a.getSI(), this.b.getSI(), this.s0.getSI(), this.tSafe.getSI(), this.delta);
}
}