1 // vacuum.cxx - a vacuum pump connected to the aircraft engine.
2 // Written by David Megginson, started 2002.
4 // This file is in the Public Domain and comes with no warranty.
11 #include <Main/fg_props.hxx>
14 VacuumSystem::VacuumSystem ( SGPropertyNode *node )
16 _name(node->getStringValue("name", "vacuum")),
17 _num(node->getIntValue("number", 0)),
18 _scale(node->getDoubleValue("scale", 1.0))
22 for ( i = 0; i < node->nChildren(); ++i ) {
23 SGPropertyNode *child = node->getChild(i);
24 string cname = child->getName();
25 string cval = child->getStringValue();
26 if ( cname == "rpm" ) {
27 _rpms.push_back(cval);
29 SG_LOG( SG_SYSTEMS, SG_WARN, "Error in vacuum config logic" );
30 if ( _name.length() ) {
31 SG_LOG( SG_SYSTEMS, SG_WARN, "Section = " << _name );
37 VacuumSystem::~VacuumSystem ()
46 branch = "/systems/" + _name;
48 SGPropertyNode *node = fgGetNode(branch.c_str(), _num, true );
49 _serviceable_node = node->getChild("serviceable", 0, true);
50 for ( i = 0; i < _rpms.size(); i++ ) {
51 SGPropertyNode_ptr _rpm_node = fgGetNode(_rpms[i].c_str(), true);
52 _rpm_nodes.push_back( _rpm_node );
54 _pressure_node = fgGetNode("/environment/pressure-inhg", true);
55 _suction_node = node->getChild("suction-inhg", 0, true);
64 VacuumSystem::unbind ()
69 VacuumSystem::update (double dt)
71 // Model taken from steam.cxx
76 if (!_serviceable_node->getBoolValue()) {
79 // select the source with the max rpm
81 for ( i = 0; i < _rpm_nodes.size(); i++ ) {
82 double tmp = _rpm_nodes[i]->getDoubleValue() * _scale;
87 double pressure = _pressure_node->getDoubleValue();
88 // This magic formula yields about 4 inhg at 700 rpm
89 suction = pressure * rpm / (rpm + 4875.0);
91 // simple regulator model that clamps smoothly to about 5 inhg
92 // over a normal rpm range
93 double max = (rpm > 0 ? 5.39 - 1.0 / ( rpm * 0.00111 ) : 0);
94 if ( suction < 0.0 ) suction = 0.0;
95 if ( suction > max ) suction = max;
97 _suction_node->setDoubleValue(suction);