X-Git-Url: https://git.mxchange.org/?a=blobdiff_plain;f=src%2FInstrumentation%2Fmag_compass.cxx;h=223c777087e79fe36b46ebdf17d06775c512779d;hb=43880b201cea2b120fefd99696ae0b43227358dc;hp=e119bb836bb2ca5851cbeb2e84d71ea00549cb99;hpb=04842a0f5b8bc3bf16c930296625a3d9814020ef;p=flightgear.git diff --git a/src/Instrumentation/mag_compass.cxx b/src/Instrumentation/mag_compass.cxx index e119bb836..223c77708 100644 --- a/src/Instrumentation/mag_compass.cxx +++ b/src/Instrumentation/mag_compass.cxx @@ -11,6 +11,7 @@ #endif #include +#include #include "mag_compass.hxx" #include
@@ -20,30 +21,8 @@ MagCompass::MagCompass ( SGPropertyNode *node ) : _error_deg(0.0), _rate_degps(0.0), - name("magnetic-compass"), - 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 magnetic-compass config logic" ); - if ( name.length() ) { - SG_LOG( SG_INSTR, SG_WARN, "Section = " << name ); - } - } - } -} - -MagCompass::MagCompass () - : _error_deg(0.0), - _rate_degps(0.0) + _name(node->getStringValue("name", "magnetic-compass")), + _num(node->getIntValue("number", 0)) { } @@ -55,39 +34,51 @@ void MagCompass::init () { string branch; - branch = "/instrumentation/" + name; + branch = "/instrumentation/" + _name; - SGPropertyNode *node = fgGetNode(branch.c_str(), num, true ); + SGPropertyNode *node = fgGetNode(branch.c_str(), _num, true ); _serviceable_node = node->getChild("serviceable", 0, true); - _roll_node = - fgGetNode("/orientation/roll-deg", true); - _pitch_node = - fgGetNode("/orientation/pitch-deg", true); - _heading_node = - fgGetNode("/orientation/heading-magnetic-deg", true); - _beta_node = - fgGetNode("/orientation/side-slip-deg", true); - _dip_node = - fgGetNode("/environment/magnetic-dip-deg", true); - _north_accel_node = - fgGetNode("/accelerations/ned/north-accel-fps_sec", true); - _east_accel_node = - fgGetNode("/accelerations/ned/east-accel-fps_sec", true); - _down_accel_node = - fgGetNode("/accelerations/ned/down-accel-fps_sec", true); + _roll_node = fgGetNode("/orientation/roll-deg", true); + _pitch_node = fgGetNode("/orientation/pitch-deg", true); + _heading_node = fgGetNode("/orientation/heading-magnetic-deg", true); + _beta_node = fgGetNode("/orientation/side-slip-deg", true); + _dip_node = fgGetNode("/environment/magnetic-dip-deg", true); + _x_accel_node = fgGetNode("/accelerations/pilot/x-accel-fps_sec", true); + _y_accel_node = fgGetNode("/accelerations/pilot/y-accel-fps_sec", true); + _z_accel_node = fgGetNode("/accelerations/pilot/z-accel-fps_sec", true); _out_node = node->getChild("indicated-heading-deg", 0, true); - - _serviceable_node->setBoolValue(true); } void MagCompass::update (double delta_time_sec) { - // don't update if it's broken + // This is the real magnetic + // which would be displayed + // if the compass had no errors. + //double heading_mag_deg = _heading_node->getDoubleValue(); + + + // don't update if the compass + // is broken if (!_serviceable_node->getBoolValue()) return; + /* + * Vassilii: commented out because this way, even when parked, + * w/o any accelerations and level, the compass is jammed. + * If somebody wants to model jamming, real forces (i.e. accelerations) + * and not sideslip angle must be considered. + */ +#if 0 + // jam on excessive sideslip + if (fabs(_beta_node->getDoubleValue()) > 12.0) { + _rate_degps = 0.0; + return; + } +#endif + + /* Formula for northernly turning error from http://williams.best.vwh.net/compass/node4.html: @@ -99,10 +90,11 @@ MagCompass::update (double delta_time_sec) Hc = atan2(sin(Hm)cos(theta)-tan(mu)sin(theta), cos(Hm)) - This function changes the variable names to the more common - psi for the heading, theta for the pitch, and phi for the - roll. It also modifies the equation to incorporate pitch - as well as roll, as suggested by Chris Metzler. + This function changes the variable names to the more common psi + for the heading, theta for the pitch, and phi for the roll (and + target_deg for Hc). It also modifies the equation to + incorporate pitch as well as roll, as suggested by Chris + Metzler. */ // bank angle (radians) @@ -118,8 +110,27 @@ MagCompass::update (double delta_time_sec) double mu = _dip_node->getDoubleValue() * SGD_DEGREES_TO_RADIANS; + /* + Tilt adjustments for accelerations. + + The magnitudes of these are totally made up, but in real life, + they would depend on the fluid level, the amount of friction, + etc. anyway. Basically, the compass float tilts forward for + acceleration and backward for deceleration. Tilt about 4 + degrees (0.07 radians) for every G (32 fps/sec) of + acceleration. + + TODO: do something with the vertical acceleration. + */ + double x_accel_g = _x_accel_node->getDoubleValue() / 32; + double y_accel_g = _y_accel_node->getDoubleValue() / 32; + //double z_accel_g = _z_accel_node->getDoubleValue() / 32; + + theta -= 0.07 * x_accel_g; + phi -= 0.07 * y_accel_g; + //////////////////////////////////////////////////////////////////// - // calculate target compass heading Hc in degrees + // calculate target compass heading degrees //////////////////////////////////////////////////////////////////// // these are expensive: don't repeat @@ -137,78 +148,29 @@ MagCompass::update (double delta_time_sec) double b = cos_theta * cos_psi * cos(mu) - sin_theta * sin_mu; - double Hc = atan2(a, b) * SGD_RADIANS_TO_DEGREES; - - while (Hc < 0) - Hc += 360; - while (Hc >= 360) - Hc =- 360; - - // TODO add acceleration error - // TODO allow binding with excessive dip/sideslip - - _out_node->setDoubleValue(Hc); - - - // algorithm from Alex Perry - // possibly broken by David Megginson - -// // jam on a sideslip of 12 degrees or more -// if (fabs(_beta_node->getDoubleValue()) > 12.0) { -// _rate_degps = 0.0; -// _error_deg = _heading_node->getDoubleValue() - -// _out_node->getDoubleValue(); -// return; -// } - -// double accelN = _north_accel_node->getDoubleValue(); -// double accelE = _east_accel_node->getDoubleValue(); -// double accelU = _down_accel_node->getDoubleValue() - 32.0; // why? - -// // force vector towards magnetic north pole -// double var = _variation_node->getDoubleValue() * SGD_DEGREES_TO_RADIANS; -// double dip = _dip_node->getDoubleValue() * SGD_DEGREES_TO_RADIANS; -// double cosdip = cos(dip); -// double forceN = cosdip * cos(var); -// double forceE = cosdip * sin(var); -// double forceU = sin(dip); - -// // rotation is around acceleration axis -// // (magnitude doesn't matter) -// double accel = accelN * accelN + accelE * accelE + accelU * accelU; -// if (accel > 1.0) -// accel = sqrt(accel); -// else -// accel = 1.0; - -// // North marking on compass card -// double edgeN = cos(_error_deg * SGD_DEGREES_TO_RADIANS); -// double edgeE = sin(_error_deg * SGD_DEGREES_TO_RADIANS); -// double edgeU = 0.0; - -// // apply the force to that edge to get torques -// double torqueN = edgeE * forceU - edgeU * forceE; -// double torqueE = edgeU * forceN - edgeN * forceU; -// double torqueU = edgeN * forceE - edgeE * forceN; - -// // get the component parallel to the axis -// double torque = (torqueN * accelN + -// torqueE * accelE + -// torqueU * accelU) * 5.0 / accel; - -// // the compass has angular momentum, -// // so apply a torque and wait -// if (delta_time_sec < 1.0) { -// _rate_degps = _rate_degps * (1.0 - delta_time_sec) - torque; -// _error_deg += delta_time_sec * _rate_degps; -// } -// if (_error_deg > 180.0) -// _error_deg -= 360.0; -// else if (_error_deg < -180.0) -// _error_deg += 360.0; - -// // Set the indicated heading -// _out_node->setDoubleValue(_heading_node->getDoubleValue() - _error_deg); + // This is the value that the compass + // is *trying* to display. + double target_deg = atan2(a, b) * SGD_RADIANS_TO_DEGREES; + double old_deg = _out_node->getDoubleValue(); + + while ((target_deg - old_deg) > 180.0) + target_deg -= 360.0; + while ((target_deg - old_deg) < -180.0) + target_deg += 360.0; + + // The compass has a current rate of + // rotation -- move the rate of rotation + // towards one that will turn the compass + // to the correct heading, but lag a bit. + // (so that the compass can keep overshooting + // and coming back). + double error = target_deg - old_deg; + _rate_degps = fgGetLowPass(_rate_degps, error, delta_time_sec / 5.0); + double indicated_deg = old_deg + _rate_degps * delta_time_sec; + SG_NORMALIZE_RANGE(indicated_deg, 0.0, 360.0); + + // That's it -- set the messed-up heading. + _out_node->setDoubleValue(indicated_deg); } // end of altimeter.cxx