// airspeed_indicator.cxx - a regular pitot-static airspeed indicator. // Written by David Megginson, started 2002. // // This file is in the Public Domain and comes with no warranty. #include #include #include "airspeed_indicator.hxx" #include
#include
// A higher number means more responsive. #define RESPONSIVENESS 50.0 AirspeedIndicator::AirspeedIndicator ( SGPropertyNode *node ) : name("airspeed-indicator"), num(0), pitot_port("/systems/pitot"), static_port("/systems/static") { int i; for ( i = 0; i < node->nChildren(); ++i ) { SGPropertyNode *child = node->getChild(i); string cname = child->getName(); string cval = child->getStringValue(); if ( cname == "name" ) { name = cval; } else if ( cname == "number" ) { num = child->getIntValue(); } else if ( cname == "pitot-port" ) { pitot_port = cval; } else if ( cname == "static-port" ) { static_port = cval; } else { SG_LOG( SG_AUTOPILOT, SG_WARN, "Error in aispeed-indicator config logic" ); if ( name.length() ) { SG_LOG( SG_AUTOPILOT, SG_WARN, "Section = " << name ); } } } } AirspeedIndicator::AirspeedIndicator ( int i ) : name("airspeed-indicator"), num(0), pitot_port("/systems/pitot"), static_port("/systems/static") { num = i; } AirspeedIndicator::~AirspeedIndicator () { } void AirspeedIndicator::init () { string branch; branch = "/instrumentation/" + name; pitot_port += "/total-pressure-inhg"; static_port += "/pressure-inhg"; SGPropertyNode *node = fgGetNode(branch.c_str(), num, true ); _serviceable_node = node->getChild("serviceable", 0, true); _total_pressure_node = fgGetNode(pitot_port.c_str(), true); _static_pressure_node = fgGetNode(static_port.c_str(), true); _density_node = fgGetNode("/environment/density-slugft3", true); _speed_node = node->getChild("indicated-speed-kt", 0, true); _serviceable_node->setBoolValue(true); } #ifndef FPSTOKTS # define FPSTOKTS 0.592484 #endif #ifndef INHGTOPSF # define INHGTOPSF (2116.217/29.9212) #endif void AirspeedIndicator::update (double dt) { if (_serviceable_node->getBoolValue()) { double pt = _total_pressure_node->getDoubleValue() * INHGTOPSF; double p = _static_pressure_node->getDoubleValue() * INHGTOPSF; double r = _density_node->getDoubleValue(); double q = ( pt - p ); // dynamic pressure // Now, reverse the equation (normalize dynamic pressure to // avoid "nan" results from sqrt) if ( q < 0 ) { q = 0.0; } double v_fps = sqrt((2 * q) / r); // Publish the indicated airspeed double last_speed_kt = _speed_node->getDoubleValue(); double current_speed_kt = v_fps * FPSTOKTS; _speed_node->setDoubleValue(fgGetLowPass(last_speed_kt, current_speed_kt, dt * RESPONSIVENESS)); } } // end of airspeed_indicator.cxx