--------------------------------------------------------------------------------
01/01/10 T.Kreitler test implementation
01/10/11 T.Kreitler changed to single rotor model
+03/06/11 T.Kreitler added brake, clutch, and experimental free-wheeling-unit
+02/05/12 T.Kreitler brake, clutch, and FWU now in FGTransmission class
%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
SENTRY
%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%*/
#include "FGThruster.h"
+#include "FGTransmission.h"
/*%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
DEFINITIONS
%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%*/
-#define ID_ROTOR "$Id: FGRotor.h,v 1.8 2011/01/17 22:09:59 jberndt Exp $"
+#define ID_ROTOR "$Id: FGRotor.h,v 1.14 2012/03/18 15:48:36 jentron Exp $"
/*%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
FORWARD DECLARATIONS
<numblades> {number} </numblades>
<gearratio> {number} </gearratio>
<nominalrpm> {number} </nominalrpm>
+ <minrpm> {number} </minrpm>
+ <maxrpm> {number} </maxrpm>
<chord unit="{LENGTH}"> {number} </chord>
<liftcurveslope Xunit="1/RAD"> {number} </liftcurveslope>
<twist unit="{ANGLE}"> {number} </twist>
<polarmoment unit="{MOMENT}"> {number} </polarmoment>
<inflowlag> {number} </inflowlag>
<tiplossfactor> {number} </tiplossfactor>
+ <maxbrakepower unit="{POWER}"> {number} </maxbrakepower>
+ <gearloss unit="{POWER}"> {number} </gearloss>
+ <gearmoment unit="{MOMENT}"> {number} </gearmoment>
<controlmap> {MAIN|TAIL|TANDEM} </controlmap>
<ExternalRPM> {number} </ExternalRPM>
<groundeffectexp> {number} </groundeffectexp>
<groundeffectshift unit="{LENGTH}"> {number} </groundeffectshift>
+
</rotor>
// LENGTH means any of the supported units, same for ANGLE and MOMENT.
\<diameter> - Rotor disk diameter (2x R).
\<numblades> - Number of blades (b).
\<gearratio> - Ratio of (engine rpm) / (rotor rpm), usually > 1.
- \<nominalrpm> - RPM at which the rotor usally operates.
+ \<nominalrpm> - RPM at which the rotor usally operates.
+ \<minrpm> - Lowest RPM used in the model, optional and defaults to 1.
+ \<maxrpm> - Largest RPM used in the model, optional and defaults to 2 x nominalrpm.
\<chord> - Blade chord, (c).
\<liftcurveslope> - Slope of curve of section lift against section angle of attack,
per rad (a).
\<massmoment> - Blade mass moment. Mass of a single blade times the blade's
cg-distance from the hub, optional.
\<polarmoment> - Moment of inertia for the whole rotor disk, optional.
- \<inflowlag> - Rotor inflow time constant, sec. Smaller values yield to
- quicker responses to control input (defaults to 0.2).
+ \<inflowlag> - Rotor inflow time constant, sec. Smaller values yield to quicker
+ responses (typical values for main rotor: 0.1 - 0.2 s).
\<tiplossfactor> - Tip-loss factor. The Blade fraction that produces lift.
Value usually ranges between 0.95 - 1.0, optional (B).
+ \<maxbrakepower> - Rotor brake, 20-30 hp should work for a mid size helicopter.
+ \<gearloss> - Friction in gear, 0.2% to 3% of the engine power, optional (see notes).
+ \<gearmoment> - Approximation for the moment of inertia of the gear (and engine),
+ defaults to 0.1 * polarmoment, optional.
+
\<controlmap> - Defines the control inputs used (see notes).
+
\<ExternalRPM> - Links the rotor to another rotor, or an user controllable property.
Experimental properties
-
+
\<groundeffectexp> - Exponent for ground effect approximation. Values usually range from 0.04
- for large rotors to 0.1 for smaller ones. As a rule of thumb the effect
+ for large rotors to 0.1 for smaller ones. As a rule of thumb the effect
vanishes at a height 2-3 times the rotor diameter.
formula used: exp ( - groundeffectexp * (height+groundeffectshift) )
Omitting or setting to 0.0 disables the effect calculation.
- \<groundeffectshift> - Further adjustment of ground effect, approx. hub height or slightly above.
+ \<groundeffectshift> - Further adjustment of ground effect, approx. hub height or slightly above
+ (This lessens the influence of the ground effect).
</pre>
-<h3>Notes:</h3>
+<h3>Notes:</h3>
<h4>- Controls -</h4>
The behavior of the rotor is controlled/influenced by following inputs.<ul>
<li> The power provided by the engine. This is handled by the regular engine controls.</li>
- <li> The collective control input. This is read from the <tt>fdm</tt> property
+ <li> The collective control input. This is read from the <tt>fdm</tt> property
<tt>propulsion/engine[x]/collective-ctrl-rad</tt>. See below for tail rotor</li>
<li> The lateral cyclic input. Read from
<tt>propulsion/engine[x]/lateral-ctrl-rad</tt>.</li>
<li> The longitudinal cyclic input. Read from
<tt>propulsion/engine[x]/longitudinal-ctrl-rad</tt>.</li>
- <li> The tail collective (aka antitorque, aka pedal) control input. Read from
- <tt>propulsion/engine[x]/antitorque-ctrl-rad</tt> or
- <tt>propulsion/engine[x]/tail-collective-ctrl-rad</tt>.</li>
+ <li> The tail rotor collective (aka antitorque, aka pedal) control input. Read from
+ <tt>propulsion/engine[x]/antitorque-ctrl-rad</tt> or
+ <tt>propulsion/engine[x]/tail-collective-ctrl-rad</tt>.</li>
</ul>
is linked to to the main (=first, =0) rotor, and specifing
<tt>\<controlmap\> TAIL \</controlmap\></tt> tells this rotor to read the
collective input from <tt>propulsion/engine[1]/antitorque-ctrl-rad</tt>
- (The TAIL-map ignores lateral and longitudinal input). The rotor needs to be
+ (The TAIL-map ignores lateral and longitudinal input). The rotor needs to be
attached to a dummy engine, e.g. an 1HP electrical engine.
A tandem rotor is setup analogous.
<h4>- Engine issues -</h4>
- Currently the rotor can only be driven with piston and electrical engines. An adaption
- for the turboprop engine might become available in the future.
- In order to keep the rotor speed constant, use of a RPM-Governor system is
+ In order to keep the rotor/engine speed constant, use of a RPM-Governor system is
encouraged (see examples).
+ In case the model requires the manual use of a clutch the <tt>\<gearloss\></tt>
+ property might need attention.<ul>
+
+ <li> Electrical: here the gear-loss should be rather large to keep the engine
+ controllable when the clutch is open (although full throttle might still make it
+ spin away).</li>
+ <li> Piston: this engine model already has some internal friction loss and also
+ looses power if it spins too high. Here the gear-loss could be set to 0.25%
+ of the engine power (which is also the approximated default).</li>
+ <li> Turboprop: Here the default value might be a bit too small. Also it's advisable
+ to adjust the power table for rpm values that are far beyond the nominal value.</li>
+
+ </ul>
+
+ <h4>- Scaling the ground effect -</h4>
+
+ The property <tt>propulsion/engine[x]/groundeffect-scale-norm</tt> allows fdm based
+ scaling of the ground effect influence. For instance the effect vanishes at speeds
+ above approx. 50kts, or one likes to land on a 'perforated' helipad.
+
<h4>- Development hints -</h4>
Setting <tt>\<ExternalRPM> -1 \</ExternalRPM></tt> the rotor's RPM is controlled by
when developing a FDM.
-<h3>References:</h3>
+<h3>References:</h3>
<dl>
<dt>/SH79/</dt><dd>Shaugnessy, J. D., Deaux, Thomas N., and Yenni, Kenneth R.,
- "Development and Validation of a Piloted Simulation of a
+ "Development and Validation of a Piloted Simulation of a
Helicopter and External Sling Load", NASA TP-1285, 1979.</dd>
<dt>/BA41/</dt><dd>Bailey,F.J.,Jr., "A Simplified Theoretical Method of Determining
the Characteristics of a Lifting Rotor in Forward Flight", NACA Rep.716, 1941.</dd>
<dt>/AM50/</dt><dd>Amer, Kenneth B.,"Theory of Helicopter Damping in Pitch or Roll and a
Comparison With Flight Measurements", NACA TN-2136, 1950.</dd>
<dt>/TA77/</dt><dd>Talbot, Peter D., Corliss, Lloyd D., "A Mathematical Force and Moment
- Model of a UH-1H Helicopter for Flight Dynamics Simulations", NASA TM-73,254, 1977.</dd>
+ Model of a UH-1H Helicopter for Flight Dynamics Simulations", NASA TM-73,254, 1977.</dd>
+ <dt>/GE49/</dt><dd>Gessow, Alfred, Amer, Kenneth B. "An Introduction to the Physical
+ Aspects of Helicopter Stability", NACA TN-1982, 1949.</dd>
</dl>
@author Thomas Kreitler
- @version $Id: FGRotor.h,v 1.8 2011/01/17 22:09:59 jberndt Exp $
+ @version $Id: FGRotor.h,v 1.14 2012/03/18 15:48:36 jentron Exp $
*/
/// Destructor for FGRotor
~FGRotor();
- /** Returns the power required by the rotor. Well, to achieve this the rotor
- is cycled through the whole machinery, yielding to a new state.
- (hmm, sort of a huge side effect)
- */
- double GetPowerRequired(void);
+ /// Returns the power required by the rotor.
+ double GetPowerRequired(void)const { return PowerRequired; }
- /** Returns the scalar thrust of the rotor, and adjusts the RPM value. */
- double Calculate(double PowerAvailable);
+ /// Returns the scalar thrust of the rotor, and adjusts the RPM value.
+ double Calculate(double EnginePower);
/// Retrieves the RPMs of the rotor.
double GetRPM(void) const { return RPM; }
-
- // void SetRPM(double rpm) { RPM = rpm; }
+ void SetRPM(double rpm) { RPM = rpm; }
/// Retrieves the RPMs of the Engine, as seen from this rotor.
- double GetEngineRPM(void) const { return GearRatio*RPM; } // bit of a hack.
+ double GetEngineRPM(void) const {return EngineRPM;} //{ return GearRatio*RPM; }
+ void SetEngineRPM(double rpm) {EngineRPM = rpm;} //{ RPM = rpm/GearRatio; }
/// Tells the rotor's gear ratio, usually the engine asks for this.
double GetGearRatio(void) { return GearRatio; }
/// Retrieves the thrust of the rotor.
/// Retrieves the torque
double GetTorque(void) const { return Torque; }
- /// Downwash angle - currently only valid for a rotor that spins horizontally
+ /// Downwash angle - positive values point forward (given a horizontal spinning rotor)
double GetThetaDW(void) const { return theta_downwash; }
- /// Downwash angle - currently only valid for a rotor that spins horizontally
+ /// Downwash angle - positive values point leftward (given a horizontal spinning rotor)
double GetPhiDW(void) const { return phi_downwash; }
+ /// Retrieves the ground effect scaling factor.
+ double GetGroundEffectScaleNorm(void) const { return GroundEffectScaleNorm; }
+ /// Sets the ground effect scaling factor.
+ void SetGroundEffectScaleNorm(double g) { GroundEffectScaleNorm = g; }
+
/// Retrieves the collective control input in radians.
double GetCollectiveCtrl(void) const { return CollectiveCtrl; }
/// Retrieves the lateral control input in radians.
void SetLongitudinalCtrl(double c) { LongitudinalCtrl = c; }
// Stubs. Only main rotor RPM is returned
- string GetThrusterLabels(int id, string delimeter);
- string GetThrusterValues(int id, string delimeter);
+ string GetThrusterLabels(int id, const string& delimeter);
+ string GetThrusterValues(int id, const string& delimeter);
private:
double ConfigValue( Element* e, const string& ename, double default_val=0.0,
bool tell=false);
- void Configure(Element* rotor_element);
+ double Configure(Element* rotor_element);
- // true entry points
- void CalcStatePart1(void);
- void CalcStatePart2(double PowerAvailable);
+ void CalcRotorState(void);
// rotor dynamics
void calc_flow_and_thrust(double theta_0, double Uw, double Ww, double flow_scale = 1.0);
void calc_flapping_angles(double theta_0, const FGColumnVector3 &pqr_fus_w);
void calc_drag_and_side_forces(double theta_0);
void calc_torque(double theta_0);
+ void calc_downwash_angles();
// transformations
FGColumnVector3 hub_vel_body2ca( const FGColumnVector3 &uvw, const FGColumnVector3 &pqr,
double Radius;
int BladeNum;
+ // rpm control
double Sense;
double NominalRPM;
+ double MinimalRPM;
+ double MaximalRPM;
int ExternalRPM;
int RPMdefinition;
FGPropertyManager* ExtRPMsource;
+ double SourceGearRatio;
+ // 'real' rotor parameters
double BladeChord;
double LiftCurveSlope;
double BladeTwist;
double InflowLag;
double TipLossB;
+ // groundeffect
double GroundEffectExp;
double GroundEffectShift;
+ double GroundEffectScaleNorm;
// derived parameters
double LockNumberByRho;
double lambda; // inflow ratio
double mu; // tip-speed ratio
double nu; // induced inflow ratio
- double v_induced; // induced velocity, always positive [ft/s]
+ double v_induced; // induced velocity, usually positive [ft/s]
double theta_downwash;
double phi_downwash;
double LateralCtrl;
double LongitudinalCtrl;
+ // interaction with engine
+ FGTransmission *Transmission;
+ double EngineRPM;
+ double MaxBrakePower;
+ double GearLoss;
+ double GearMoment;
+
};
}
projects / flightgear.git / blobdiff