--- /dev/null
+// heading_indicator_fg.cxx - a flux_gate compass.
+// Based on the vacuum driven Heading Indicator Written by David Megginson, started 2002.
+//
+// Written by Vivian Meazza, started 2005.
+//
+// This file is in the Public Domain and comes with no warranty.
+
+#include <simgear/compiler.h>
+#include STL_IOSTREAM
+#include STL_STRING
+#include <sstream>
+
+#include "heading_indicator_fg.hxx"
+#include <Main/fg_props.hxx>
+#include <Main/util.hxx>
+
+
+HeadingIndicatorFG::HeadingIndicatorFG ( SGPropertyNode *node )
+ :
+ name("heading-indicator-fg"),
+ num(0)
+{
+ 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 {
+ SG_LOG( SG_INSTR, SG_WARN, "Error in flux-gate heading-indicator config logic" );
+ if ( name.length() ) {
+ SG_LOG( SG_INSTR, SG_WARN, "Section = " << name );
+ }
+ }
+ }
+}
+
+HeadingIndicatorFG::HeadingIndicatorFG ()
+{
+}
+
+HeadingIndicatorFG::~HeadingIndicatorFG ()
+{
+}
+
+void
+HeadingIndicatorFG::init ()
+{
+ string branch;
+ branch = "/instrumentation/" + name;
+
+ _heading_in_node = fgGetNode("/orientation/heading-deg", true);
+ SGPropertyNode *node = fgGetNode(branch.c_str(), num, true );
+ _offset_node = node->getChild("offset-deg", 0, true);
+ _serviceable_node = node->getChild("serviceable", 0, true);
+ _error_node = node->getChild("heading-bug-error-deg", 0, true);
+ _nav1_error_node = node->getChild("nav1-course-error-deg", 0, true);
+ _heading_out_node = node->getChild("indicated-heading-deg", 0, true);
+ _last_heading_deg = (_heading_in_node->getDoubleValue() +
+ _offset_node->getDoubleValue());
+ _electrical_node = fgGetNode("/systems/electrical/outputs/DG", true);
+}
+
+void
+HeadingIndicatorFG::bind ()
+{
+ std::ostringstream temp;
+ string branch;
+ temp << num;
+ branch = "/instrumentation/" + name + "[" + temp.str() + "]";
+
+ fgTie((branch + "/serviceable").c_str(),
+ &_gyro, &Gyro::is_serviceable, &Gyro::set_serviceable);
+ fgTie((branch + "/spin").c_str(),
+ &_gyro, &Gyro::get_spin_norm, &Gyro::set_spin_norm);
+
+}
+
+void
+HeadingIndicatorFG::unbind ()
+{
+ std::ostringstream temp;
+ string branch;
+ temp << num;
+ branch = "/instrumentation/" + name + "[" + temp.str() + "]";
+
+ fgUntie((branch + "/serviceable").c_str());
+ fgUntie((branch + "/spin").c_str());
+}
+
+void
+HeadingIndicatorFG::update (double dt)
+{
+ // Get the spin from the gyro
+ _gyro.set_power_norm(_electrical_node->getDoubleValue());
+
+ _gyro.update(dt);
+ double spin = _gyro.get_spin_norm();
+
+ // No time-based precession for a flux gate compass
+ // We just use offset to get the magvar
+
+ double offset = _offset_node->getDoubleValue();
+
+ // TODO: movement-induced error
+
+ // Next, calculate the indicated heading,
+ // introducing errors.
+ double factor = 0.01 / (spin * spin * spin * spin * spin * spin);
+ double heading = _heading_in_node->getDoubleValue();
+
+ // Now, we have to get the current
+ // heading and the last heading into
+ // the same range.
+ while ((heading - _last_heading_deg) > 180)
+ _last_heading_deg += 360;
+ while ((heading - _last_heading_deg) < -180)
+ _last_heading_deg -= 360;
+
+ heading = fgGetLowPass(_last_heading_deg, heading, dt/factor);
+ _last_heading_deg = heading;
+
+ heading += offset;
+ while (heading < 0)
+ heading += 360;
+ while (heading > 360)
+ heading -= 360;
+
+ _heading_out_node->setDoubleValue(heading);
+
+ // calculate the difference between the indicacted heading
+ // and the selected heading for use with an autopilot
+ static SGPropertyNode *bnode
+ = fgGetNode( "/autopilot/settings/heading-bug-deg", false );
+ double diff = 0;
+ if ( bnode ){
+ diff = bnode->getDoubleValue() - heading;
+ if ( diff < -180.0 ) { diff += 360.0; }
+ if ( diff > 180.0 ) { diff -= 360.0; }
+ _error_node->setDoubleValue( diff );
+ }
+ // calculate the difference between the indicated heading
+ // and the selected nav1 radial for use with an autopilot
+ SGPropertyNode *nnode
+ = fgGetNode( "/instrumentation/nav/radials/selected-deg", true );
+ double ndiff = 0;
+ if ( nnode ){
+ ndiff = nnode->getDoubleValue() - heading;
+ if ( ndiff < -180.0 ) { ndiff += 360.0; }
+ if ( ndiff > 180.0 ) { ndiff -= 360.0; }
+ _nav1_error_node->setDoubleValue( ndiff );
+ }
+
+
+}
+
+// end of heading_indicator_fg.cxx
--- /dev/null
+// heading_indicator.hxx - a vacuum-powered heading indicator.
+// Written by David Megginson, started 2002.
+//
+// This file is in the Public Domain and comes with no warranty.
+
+
+#ifndef __INSTRUMENTS_HEADING_INDICATOR_FG_HXX
+#define __INSTRUMENTS_HEADING_INDICATOR_FG_HXX 1
+
+#ifndef __cplusplus
+# error This library requires C++
+#endif
+
+#include <simgear/props/props.hxx>
+#include <simgear/structure/subsystem_mgr.hxx>
+
+#include "gyro.hxx"
+
+
+/**
+ * Model an electicallym-powered fluxgate compass
+ *
+ * Input properties:
+ *
+ * /instrumentation/"name"/serviceable
+ * /instrumentation/"name"/spin
+ * /instrumentation/"name"/offset-deg
+ * /orientation/heading-deg
+ * /systems/electrical/outputs/DG
+ *
+ * Output properties:
+ *
+ * /instrumentation/"name"/indicated-heading-deg
+ */
+class HeadingIndicatorFG : public SGSubsystem
+{
+
+public:
+
+ HeadingIndicatorFG ( SGPropertyNode *node );
+ HeadingIndicatorFG ();
+ virtual ~HeadingIndicatorFG ();
+
+ virtual void init ();
+ virtual void bind ();
+ virtual void unbind ();
+ virtual void update (double dt);
+
+private:
+
+ Gyro _gyro;
+ double _last_heading_deg;
+
+ string name;
+ int num;
+
+ SGPropertyNode_ptr _offset_node;
+ SGPropertyNode_ptr _heading_in_node;
+ SGPropertyNode_ptr _serviceable_node;
+ SGPropertyNode_ptr _heading_out_node;
+ SGPropertyNode_ptr _electrical_node;
+ SGPropertyNode_ptr _error_node;
+ SGPropertyNode_ptr _nav1_error_node;
+
+
+
+};
+
+#endif // __INSTRUMENTS_HEADING_INDICATOR_HXX
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