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Merge branch 'syd/ias-limit' into next

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This commit is contained in:
Tim Moore 2010-03-27 19:06:53 +01:00
commit 37d3cf7fbb
2 changed files with 43 additions and 4 deletions
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39
src/Instrumentation/airspeed_indicator.cxx
View file

@ -10,6 +10,8 @@
#include "airspeed_indicator.hxx"
#include <Main/fg_props.hxx>
#include <Main/util.hxx>
#include <Environment/environment_mgr.hxx>
#include <Environment/environment.hxx>
// A higher number means more responsive.
@ -27,6 +29,7 @@ AirspeedIndicator::AirspeedIndicator ( SGPropertyNode *node )
_mach_limit(node->getDoubleValue("mach-limit", 0.48)),
_alt_threshold(node->getDoubleValue("alt-threshold", 13200))
{
_environmentManager = NULL;
}
AirspeedIndicator::~AirspeedIndicator ()
@ -45,7 +48,9 @@ AirspeedIndicator::init ()
_static_pressure_node = fgGetNode(_static_pressure.c_str(), true);
_density_node = fgGetNode("/environment/density-slugft3", true);
_speed_node = node->getChild("indicated-speed-kt", 0, true);
_tas_node = node->getChild("true-speed-kt", 0, true);
_mach_node = node->getChild("indicated-mach", 0, true);
// overspeed-indicator properties
if (_has_overspeed) {
_ias_limit_node = node->getNode("ias-limit",0, true);
@ -66,8 +71,9 @@ AirspeedIndicator::init ()
_airspeed_limit = node->getChild("airspeed-limit-kt", 0, true);
_pressure_alt = fgGetNode(_pressure_alt_source.c_str(), true);
_mach = fgGetNode("/velocities/mach", true);
}
_environmentManager = (FGEnvironmentMgr*) globals->get_subsystem("environment");
}
#ifndef FPSTOKTS
@ -102,6 +108,7 @@ AirspeedIndicator::update (double dt)
current_speed_kt,
dt * RESPONSIVENESS);
_speed_node->setDoubleValue(filtered_speed);
computeMach(filtered_speed);
if (!_has_overspeed) {
return;
@ -110,10 +117,36 @@ AirspeedIndicator::update (double dt)
double lmt = _ias_limit_node->getDoubleValue();
if (_pressure_alt->getDoubleValue() > _alt_threshold_node->getDoubleValue()) {
double mmo = _mach_limit_node->getDoubleValue();
lmt = (filtered_speed/_mach->getDoubleValue())* mmo;
lmt = (filtered_speed/_mach_node->getDoubleValue())* mmo;
}
_airspeed_limit->setDoubleValue(lmt);
}
void
AirspeedIndicator::computeMach(double ias)
{
if (!_environmentManager) {
return;
}
FGEnvironment env(_environmentManager->getEnvironment());
// derived from http://williams.best.vwh.net/avform.htm#Mach
// names here are picked to be consistent with those formulae!
double oatK = env.get_temperature_degc() + 273.15; // OAT in Kelvin
double CS = 38.967854 * sqrt(oatK); // speed-of-sound in knots at altitude
double CS_0 = 661.4786; // speed-of-sound in knots at sea-level
double P_0 = env.get_pressure_sea_level_inhg();
double P = _static_pressure_node->getDoubleValue();
double DP = P_0 * (pow(1 + 0.2*pow(ias/CS_0, 2), 3.5) - 1);
double mach = pow(5 * ( pow(DP/P + 1, 2.0/7.0) -1) , 0.5);
// publish Mach and TAS
_mach_node->setDoubleValue(mach);
_tas_node->setDoubleValue(CS * mach);
}
// end of airspeed_indicator.cxx

8
src/Instrumentation/airspeed_indicator.hxx
View file

@ -14,6 +14,8 @@
#include <simgear/props/props.hxx>
#include <simgear/structure/subsystem_mgr.hxx>
// forward decls
class FGEnvironmentMgr;
/**
* Model an airspeed indicator tied to the pitot and static ports.
@ -41,6 +43,7 @@ public:
virtual void update (double dt);
private:
void computeMach(double ias);
string _name;
unsigned int _num;
@ -62,7 +65,10 @@ private:
SGPropertyNode_ptr _speed_node;
SGPropertyNode_ptr _airspeed_limit;
SGPropertyNode_ptr _pressure_alt;
SGPropertyNode_ptr _mach;
SGPropertyNode_ptr _mach_node;
SGPropertyNode_ptr _tas_node;
FGEnvironmentMgr* _environmentManager;
};
#endif // __INSTRUMENTS_AIRSPEED_INDICATOR_HXX