capacitance.cpp

/***************************************************************************
 *   Copyright (C) 2003-2005 by David Saxton                               *
 *   david@bluehaze.org                                                    *
 *                                                                         *
 *   This program is free software; you can redistribute it and/or modify  *
 *   it under the terms of the GNU General Public License as published by  *
 *   the Free Software Foundation; either version 2 of the License, or     *
 *   (at your option) any later version.                                   *
 ***************************************************************************/

#include "capacitance.h"

Capacitance::Capacitance( const double capacitance, const double delta )
        : Reactive(delta)
{
        m_cap = capacitance;
        g_eq_old = i_eq_old = 0.;
        m_numCNodes = 2;
        setMethod( Capacitance::m_euler );
}

Capacitance::~Capacitance()
{
}

void Capacitance::setCapacitance( const double c )
{
        m_cap = c;
}

void Capacitance::add_initial_dc()
{
        // We don't need to do anything here, as time_step() will do that for us,
        // apart from to make sure our old values are 0
        g_eq_old = i_eq_old = 0.;
}

void Capacitance::updateCurrents()
{
        if (!b_status) return;
        const double r_i = (p_cnode[0]->v-p_cnode[1]->v)*g_eq_old;
        m_cnodeI[0] = -i_eq_old-r_i;
        m_cnodeI[1] = -m_cnodeI[0];
}


void Capacitance::add_map()
{
        if (!b_status) return;
        
        if ( !p_cnode[0]->isGround )
        {
                p_A->setUse( p_cnode[0]->n(), p_cnode[0]->n(), Map::et_unstable, false );
        }
        if ( !p_cnode[1]->isGround )
        {
                p_A->setUse( p_cnode[1]->n(), p_cnode[1]->n(), Map::et_unstable, false );
        }
        
        if ( !p_cnode[0]->isGround && !p_cnode[1]->isGround )
        {
                p_A->setUse( p_cnode[0]->n(), p_cnode[1]->n(), Map::et_unstable, false );
                p_A->setUse( p_cnode[1]->n(), p_cnode[0]->n(), Map::et_unstable, false );
        }
}


void Capacitance::time_step()
{
        if (!b_status) return;
        
        double v = p_cnode[0]->v-p_cnode[1]->v;
        double i_eq_new = 0.0, g_eq_new = 0.0;
        
        if ( m_method == Capacitance::m_euler )
        {
                g_eq_new = m_cap/m_delta;
                i_eq_new = -v*g_eq_new;
        } else if ( m_method == Capacitance::m_trap ) {
                // TODO Implement + test trapezoidal method
                g_eq_new = 2.*m_cap/m_delta;
        }
        
        if ( g_eq_old != g_eq_new )
        {
                A_g( 0, 0 ) += g_eq_new-g_eq_old;
                A_g( 1, 1 ) += g_eq_new-g_eq_old;
                A_g( 0, 1 ) -= g_eq_new-g_eq_old;
                A_g( 1, 0 ) -= g_eq_new-g_eq_old;
        }
        
        if ( i_eq_new != i_eq_old )
        {
                b_i( 0 ) -= i_eq_new-i_eq_old;
                b_i( 1 ) += i_eq_new-i_eq_old;
        }
        
        g_eq_old = g_eq_new;
        i_eq_old = i_eq_new;
}

bool Capacitance::updateStatus()
{
        b_status = Reactive::updateStatus();
        if ( m_method == Capacitance::m_none ) b_status = false;
        return b_status;
}

void Capacitance::setMethod( Method m )
{
        m_method = m;
        updateStatus();
}

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