package org.opentrafficsim.road.gtu.lane.control;
   
   import org.djunits.value.vdouble.scalar.Acceleration;
   import org.opentrafficsim.base.parameters.ParameterException;
   import org.opentrafficsim.base.parameters.ParameterTypeDouble;
   import org.opentrafficsim.base.parameters.Parameters;
   import org.opentrafficsim.base.parameters.constraint.NumericConstraint;
   import org.opentrafficsim.road.gtu.lane.LaneBasedGTU;
   import org.opentrafficsim.road.gtu.lane.perception.PerceptionCollectable;
  import org.opentrafficsim.road.gtu.lane.perception.headway.HeadwayGTU;
  
  /**
   * Simple linear CACC implementation.
   * <p>
   * Copyright (c) 2013-2019 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 $Revision$, $LastChangedDate$, by $Author$, initial version Mar 13, 2019 <br>
   * @author <a href="http://www.tbm.tudelft.nl/averbraeck">Alexander Verbraeck</a>
   * @author <a href="http://www.tudelft.nl/pknoppers">Peter Knoppers</a>
   * @author <a href="http://www.transport.citg.tudelft.nl">Wouter Schakel</a>
   */
  public class LinearCACC extends AbstractLinearFreeControl
  {
  
      /**
       * Constructor using default sensors with no delay.
       * @param delayedActuation DelayedActuation; delayed actuation
       */
      public LinearCACC(final DelayedActuation delayedActuation)
      {
          super(delayedActuation);
      }
  
      /** Gap error gain parameter. */
      public static final ParameterTypeDouble KS =
              new ParameterTypeDouble("ks", "Gap error gain", 0.2, NumericConstraint.POSITIVE);
  
      /** Speed error gain parameter. */
      public static final ParameterTypeDouble KV =
              new ParameterTypeDouble("kv", "Speed error gain", 0.4, NumericConstraint.POSITIVE);
  
      /** Acceleration error gain parameter. */
      public static final ParameterTypeDouble KA =
              new ParameterTypeDouble("ka", "Acceleration error gain", 1.0, NumericConstraint.POSITIVE);
  
      /** {@inheritDoc} */
      @Override
      public Acceleration getFollowingAcceleration(final LaneBasedGTU gtu,
              final PerceptionCollectable<HeadwayGTU, LaneBasedGTU> leaders) throws ParameterException
      {
          Parameters params = gtu.getParameters();
          HeadwayGTU leader = leaders.first();
          double es;
          double kaui;
          if (leader.getAcceleration() == null)
          {
              // ACC mode
              es = leader.getDistance().si - gtu.getSpeed().si * params.getParameter(TDACC).si - params.getParameter(X0).si;
              kaui = 0.0;
          }
          else
          {
              // CACC mode
              es = leader.getDistance().si - gtu.getSpeed().si * params.getParameter(TDCACC).si - params.getParameter(X0).si;
              kaui = params.getParameter(KA) * leader.getAcceleration().si;
          }
          double ev = leader.getSpeed().si - gtu.getSpeed().si;
          return Acceleration.createSI(params.getParameter(KS) * es + params.getParameter(KV) * ev + kaui);
      }
  
  }