li-ion-energy-source.cc

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/*
 * Copyright (c) 2010 Andrea Sacco
 *
 * This program is free software; you can redistribute it and/or modify
 * it under the terms of the GNU General Public License version 2 as
 * published by the Free Software Foundation;
 *
 * This program is distributed in the hope that it will be useful,
 * but WITHOUT ANY WARRANTY; without even the implied warranty of
 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
 * GNU General Public License for more details.
 *
 * You should have received a copy of the GNU General Public License
 * along with this program; if not, write to the Free Software
 * Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA  02111-1307  USA
 *
 * Author: Andrea Sacco <andrea.sacco85@gmail.com>
 */
 
#include "li-ion-energy-source.h"
 
#include "ns3/assert.h"
#include "ns3/double.h"
#include "ns3/log.h"
#include "ns3/simulator.h"
#include "ns3/trace-source-accessor.h"
 
#include <cmath>
 
namespace ns3
{
 
NS_LOG_COMPONENT_DEFINE("LiIonEnergySource");
 
NS_OBJECT_ENSURE_REGISTERED(LiIonEnergySource);
 
TypeId
LiIonEnergySource::GetTypeId()
{
    static TypeId tid =
        TypeId("ns3::LiIonEnergySource")
            .SetParent<EnergySource>()
            .SetGroupName("Energy")
            .AddConstructor<LiIonEnergySource>()
            .AddAttribute("LiIonEnergySourceInitialEnergyJ",
                          "Initial energy stored in basic energy source.",
                          DoubleValue(31752.0), // in Joules
                          MakeDoubleAccessor(&LiIonEnergySource::SetInitialEnergy,
                                             &LiIonEnergySource::GetInitialEnergy),
                          MakeDoubleChecker<double>())
            .AddAttribute("LiIonEnergyLowBatteryThreshold",
                          "Low battery threshold for LiIon energy source.",
                          DoubleValue(0.10), // as a fraction of the initial energy
                          MakeDoubleAccessor(&LiIonEnergySource::m_lowBatteryTh),
                          MakeDoubleChecker<double>())
            .AddAttribute("InitialCellVoltage",
                          "Initial (maximum) voltage of the cell (fully charged).",
                          DoubleValue(4.05), // in Volts
                          MakeDoubleAccessor(&LiIonEnergySource::SetInitialSupplyVoltage,
                                             &LiIonEnergySource::GetSupplyVoltage),
                          MakeDoubleChecker<double>())
            .AddAttribute("NominalCellVoltage",
                          "Nominal voltage of the cell.",
                          DoubleValue(3.6), // in Volts
                          MakeDoubleAccessor(&LiIonEnergySource::m_eNom),
                          MakeDoubleChecker<double>())
            .AddAttribute("ExpCellVoltage",
                          "Cell voltage at the end of the exponential zone.",
                          DoubleValue(3.6), // in Volts
                          MakeDoubleAccessor(&LiIonEnergySource::m_eExp),
                          MakeDoubleChecker<double>())
            .AddAttribute("RatedCapacity",
                          "Rated capacity of the cell.",
                          DoubleValue(2.45), // in Ah
                          MakeDoubleAccessor(&LiIonEnergySource::m_qRated),
                          MakeDoubleChecker<double>())
            .AddAttribute("NomCapacity",
                          "Cell capacity at the end of the nominal zone.",
                          DoubleValue(1.1), // in Ah
                          MakeDoubleAccessor(&LiIonEnergySource::m_qNom),
                          MakeDoubleChecker<double>())
            .AddAttribute("ExpCapacity",
                          "Cell Capacity at the end of the exponential zone.",
                          DoubleValue(1.2), // in Ah
                          MakeDoubleAccessor(&LiIonEnergySource::m_qExp),
                          MakeDoubleChecker<double>())
            .AddAttribute("InternalResistance",
                          "Internal resistance of the cell",
                          DoubleValue(0.083), // in Ohms
                          MakeDoubleAccessor(&LiIonEnergySource::m_internalResistance),
                          MakeDoubleChecker<double>())
            .AddAttribute("TypCurrent",
                          "Typical discharge current used to fit the curves",
                          DoubleValue(2.33), // in A
                          MakeDoubleAccessor(&LiIonEnergySource::m_typCurrent),
                          MakeDoubleChecker<double>())
            .AddAttribute("ThresholdVoltage",
                          "Minimum threshold voltage to consider the battery depleted.",
                          DoubleValue(3.3), // in Volts
                          MakeDoubleAccessor(&LiIonEnergySource::m_minVoltTh),
                          MakeDoubleChecker<double>())
            .AddAttribute("PeriodicEnergyUpdateInterval",
                          "Time between two consecutive periodic energy updates.",
                          TimeValue(Seconds(1.0)),
                          MakeTimeAccessor(&LiIonEnergySource::SetEnergyUpdateInterval,
                                           &LiIonEnergySource::GetEnergyUpdateInterval),
                          MakeTimeChecker())
            .AddTraceSource("RemainingEnergy",
                            "Remaining energy at BasicEnergySource.",
                            MakeTraceSourceAccessor(&LiIonEnergySource::m_remainingEnergyJ),
                            "ns3::TracedValueCallback::Double");
    return tid;
}
 
LiIonEnergySource::LiIonEnergySource()
    : m_drainedCapacity(0.0),
      m_lastUpdateTime(Seconds(0.0))
{
    NS_LOG_FUNCTION(this);
}
 
LiIonEnergySource::~LiIonEnergySource()
{
    NS_LOG_FUNCTION(this);
}
 
void
LiIonEnergySource::SetInitialEnergy(double initialEnergyJ)
{
    NS_LOG_FUNCTION(this << initialEnergyJ);
    NS_ASSERT(initialEnergyJ >= 0);
    m_initialEnergyJ = initialEnergyJ;
    // set remaining energy to be initial energy
    m_remainingEnergyJ = m_initialEnergyJ;
}
 
double
LiIonEnergySource::GetInitialEnergy() const
{
    NS_LOG_FUNCTION(this);
    return m_initialEnergyJ;
}
 
void
LiIonEnergySource::SetInitialSupplyVoltage(double supplyVoltageV)
{
    NS_LOG_FUNCTION(this << supplyVoltageV);
    m_eFull = supplyVoltageV;
    m_supplyVoltageV = supplyVoltageV;
}
 
double
LiIonEnergySource::GetSupplyVoltage() const
{
    NS_LOG_FUNCTION(this);
    return m_supplyVoltageV;
}
 
void
LiIonEnergySource::SetEnergyUpdateInterval(Time interval)
{
    NS_LOG_FUNCTION(this << interval);
    m_energyUpdateInterval = interval;
}
 
Time
LiIonEnergySource::GetEnergyUpdateInterval() const
{
    NS_LOG_FUNCTION(this);
    return m_energyUpdateInterval;
}
 
double
LiIonEnergySource::GetRemainingEnergy()
{
    NS_LOG_FUNCTION(this);
    // update energy source to get the latest remaining energy.
    UpdateEnergySource();
    return m_remainingEnergyJ;
}
 
double
LiIonEnergySource::GetEnergyFraction()
{
    NS_LOG_FUNCTION(this);
    // update energy source to get the latest remaining energy.
    UpdateEnergySource();
    return m_remainingEnergyJ / m_initialEnergyJ;
}
 
void
LiIonEnergySource::DecreaseRemainingEnergy(double energyJ)
{
    NS_LOG_FUNCTION(this << energyJ);
    NS_ASSERT(energyJ >= 0);
    m_remainingEnergyJ -= energyJ;
 
    // check if remaining energy is 0
    if (m_supplyVoltageV <= m_minVoltTh)
    {
        HandleEnergyDrainedEvent();
    }
}
 
void
LiIonEnergySource::IncreaseRemainingEnergy(double energyJ)
{
    NS_LOG_FUNCTION(this << energyJ);
    NS_ASSERT(energyJ >= 0);
    m_remainingEnergyJ += energyJ;
}
 
void
LiIonEnergySource::UpdateEnergySource()
{
    NS_LOG_FUNCTION(this);
    NS_LOG_DEBUG("LiIonEnergySource:Updating remaining energy at node #" << GetNode()->GetId());
 
    // do not update if simulation has finished
    if (Simulator::IsFinished())
    {
        return;
    }
 
    m_energyUpdateEvent.Cancel();
 
    CalculateRemainingEnergy();
 
    m_lastUpdateTime = Simulator::Now();
 
    if (m_remainingEnergyJ <= m_lowBatteryTh * m_initialEnergyJ)
    {
        HandleEnergyDrainedEvent();
        return; // stop periodic update
    }
 
    m_energyUpdateEvent =
        Simulator::Schedule(m_energyUpdateInterval, &LiIonEnergySource::UpdateEnergySource, this);
}
 
/*
 * Private functions start here.
 */
void
LiIonEnergySource::DoInitialize()
{
    NS_LOG_FUNCTION(this);
    UpdateEnergySource(); // start periodic update
}
 
void
LiIonEnergySource::DoDispose()
{
    NS_LOG_FUNCTION(this);
    BreakDeviceEnergyModelRefCycle(); // break reference cycle
}
 
void
LiIonEnergySource::HandleEnergyDrainedEvent()
{
    NS_LOG_FUNCTION(this);
    NS_LOG_DEBUG("LiIonEnergySource:Energy depleted at node #" << GetNode()->GetId());
    NotifyEnergyDrained(); // notify DeviceEnergyModel objects
}
 
void
LiIonEnergySource::CalculateRemainingEnergy()
{
    NS_LOG_FUNCTION(this);
    double totalCurrentA = CalculateTotalCurrent();
    Time duration = Simulator::Now() - m_lastUpdateTime;
    NS_ASSERT(duration.GetSeconds() >= 0);
    // energy = current * voltage * time
    double energyToDecreaseJ = totalCurrentA * m_supplyVoltageV * duration.GetSeconds();
 
    if (m_remainingEnergyJ < energyToDecreaseJ)
    {
        m_remainingEnergyJ = 0; // energy never goes below 0
    }
    else
    {
        m_remainingEnergyJ -= energyToDecreaseJ;
    }
 
    m_drainedCapacity += (totalCurrentA * duration).GetHours();
    // update the supply voltage
    m_supplyVoltageV = GetVoltage(totalCurrentA);
    NS_LOG_DEBUG("LiIonEnergySource:Remaining energy = " << m_remainingEnergyJ);
}
 
double
LiIonEnergySource::GetVoltage(double i) const
{
    NS_LOG_FUNCTION(this << i);
 
    // integral of i in dt, drained capacity in Ah
    double it = m_drainedCapacity;
 
    // empirical factors
    double A = m_eFull - m_eExp;
    double B = 3 / m_qExp;
 
    // slope of the polarization curve
    double K = std::abs((m_eFull - m_eNom + A * (std::exp(-B * m_qNom) - 1)) * (m_qRated - m_qNom) /
                        m_qNom);
 
    // constant voltage
    double E0 = m_eFull + K + m_internalResistance * m_typCurrent - A;
 
    double E = E0 - K * m_qRated / (m_qRated - it) + A * std::exp(-B * it);
 
    // cell voltage
    double V = E - m_internalResistance * i;
 
    NS_LOG_DEBUG("Voltage: " << V << " with E: " << E);
 
    return V;
}
 
} // namespace ns3