-/*******************************************************************************
+/*%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
Header: FGLGear.h
Author: Jon S. Berndt
--------------------------------------------------------------------------------
11/18/99 JSB Created
-********************************************************************************
+%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
SENTRY
-*******************************************************************************/
+%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%*/
#ifndef FGLGEAR_H
#define FGLGEAR_H
-/*******************************************************************************
-COMMENTS, REFERENCES, and NOTES
-********************************************************************************
-
-[1] Cooke, Zyda, Pratt, and McGhee, "NPSNET: Flight Simulation Dynamic Modeling
- Using Quaternions", Presence, Vol. 1, No. 4, pp. 404-420 Naval Postgraduate
- School, January 1994
-[2] D. M. Henderson, "Euler Angles, Quaternions, and Transformation Matrices",
- JSC 12960, July 1977
-[3] Richard E. McFarland, "A Standard Kinematic Model for Flight Simulation at
- NASA-Ames", NASA CR-2497, January 1975
-[4] Barnes W. McCormick, "Aerodynamics, Aeronautics, and Flight Mechanics",
- Wiley & Sons, 1979 ISBN 0-471-03032-5
-[5] Bernard Etkin, "Dynamics of Flight, Stability and Control", Wiley & Sons,
- 1982 ISBN 0-471-08936-2
-
-********************************************************************************
+/*%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
INCLUDES
-*******************************************************************************/
+%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%*/
#ifdef FGFS
# include <simgear/compiler.h>
#endif
+#include "FGJSBBase.h"
+#include "FGFDMExec.h"
#include <string>
#include "FGConfigFile.h"
-#include "FGMatrix.h"
-#include "FGFDMExec.h"
-#include "FGState.h"
+#include "FGColumnVector3.h"
-/*******************************************************************************
+/*%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
DEFINITIONS
-*******************************************************************************/
+%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%*/
-/*******************************************************************************
-CLASS DECLARATION
-*******************************************************************************/
+#define ID_LGEAR "$Id$"
+
+/*%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
+FORWARD DECLARATIONS
+%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%*/
+
+namespace JSBSim {
class FGAircraft;
class FGPosition;
class FGRotation;
+class FGFCS;
+class FGState;
+class FGMassBalance;
-class FGLGear
+/*%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
+CLASS DOCUMENTATION
+%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%*/
+
+/** Landing gear model.
+ Calculates forces and moments due to landing gear reactions. This is done in
+ several steps, and is dependent on what kind of gear is being modeled. Here
+ are the parameters that can be specified in the config file for modeling
+ landing gear:
+ <p>
+ <b><u>Physical Characteristics</u></b><br>
+ <ol>
+ <li>X, Y, Z location, in inches in structural coordinate frame</li>
+ <li>Spring constant, in lbs/ft</li>
+ <li>Damping coefficient, in lbs/ft/sec</li>
+ <li>Dynamic Friction Coefficient</li>
+ <li>Static Friction Coefficient</li>
+ </ol></p><p>
+ <b><u>Operational Properties</b></u><br>
+ <ol>
+ <li>Name</li>
+ <li>Steerability attribute {one of STEERABLE | FIXED | CASTERED}</li>
+ <li>Brake Group Membership {one of LEFT | CENTER | RIGHT | NOSE | TAIL | NONE}</li>
+ <li>Max Steer Angle, in degrees</li>
+ </ol></p>
+ <p>
+ <b><u>Algorithm and Approach to Modeling</u></b><br>
+ <ol>
+ <li>Find the location of the uncompressed landing gear relative to the CG of
+ the aircraft. Remember, the structural coordinate frame that the aircraft is
+ defined in is: X positive towards the tail, Y positive out the right side, Z
+ positive upwards. The locations of the various parts are given in inches in
+ the config file.</li>
+ <li>The vector giving the location of the gear (relative to the cg) is
+ rotated 180 degrees about the Y axis to put the coordinates in body frame (X
+ positive forwards, Y positive out the right side, Z positive downwards, with
+ the origin at the cg). The lengths are also now given in feet.</li>
+ <li>The new gear location is now transformed to the local coordinate frame
+ using the body-to-local matrix. (Mb2l).</li>
+ <li>Knowing the location of the center of gravity relative to the ground
+ (height above ground level or AGL) now enables gear deflection to be
+ calculated. The gear compression value is the local frame gear Z location
+ value minus the height AGL. [Currently, we make the assumption that the gear
+ is oriented - and the deflection occurs in - the Z axis only. Additionally,
+ the vector to the landing gear is currently not modified - which would
+ (correctly) move the point of contact to the actual compressed-gear point of
+ contact. Eventually, articulated gear may be modeled, but initially an
+ effort must be made to model a generic system.] As an example, say the
+ aircraft left main gear location (in local coordinates) is Z = 3 feet
+ (positive) and the height AGL is 2 feet. This tells us that the gear is
+ compressed 1 foot.</li>
+ <li>If the gear is compressed, a Weight-On-Wheels (WOW) flag is set.</li>
+ <li>With the compression length calculated, the compression velocity may now
+ be calculated. This will be used to determine the damping force in the
+ strut. The aircraft rotational rate is multiplied by the vector to the wheel
+ to get a wheel velocity in body frame. That velocity vector is then
+ transformed into the local coordinate frame.</li>
+ <li>The aircraft cg velocity in the local frame is added to the
+ just-calculated wheel velocity (due to rotation) to get a total wheel
+ velocity in the local frame.</li>
+ <li>The compression speed is the Z-component of the vector.</li>
+ <li>With the wheel velocity vector no longer needed, it is normalized and
+ multiplied by a -1 to reverse it. This will be used in the friction force
+ calculation.</li>
+ <li>Since the friction force takes place solely in the runway plane, the Z
+ coordinate of the normalized wheel velocity vector is set to zero.</li>
+ <li>The gear deflection force (the force on the aircraft acting along the
+ local frame Z axis) is now calculated given the spring and damper
+ coefficients, and the gear deflection speed and stroke length. Keep in mind
+ that gear forces always act in the negative direction (in both local and
+ body frames), and are not capable of generating a force in the positive
+ sense (one that would attract the aircraft to the ground). So, the gear
+ forces are always negative - they are limited to values of zero or less. The
+ gear force is simply the negative of the sum of the spring compression
+ length times the spring coefficient and the gear velocity times the damping
+ coefficient.</li>
+ <li>The lateral/directional force acting on the aircraft through the landing
+
+ gear (along the local frame X and Y axes) is calculated next. First, the
+ friction coefficient is multiplied by the recently calculated Z-force. This
+ is the friction force. It must be given direction in addition to magnitude.
+ We want the components in the local frame X and Y axes. From step 9, above,
+ the conditioned wheel velocity vector is taken and the X and Y parts are
+ multiplied by the friction force to get the X and Y components of friction.
+ </li>
+ <li>The wheel force in local frame is next converted to body frame.</li>
+ <li>The moment due to the gear force is calculated by multiplying r x F
+ (radius to wheel crossed into the wheel force). Both of these operands are
+ in body frame.</li>
+ </ol>
+ @author Jon S. Berndt
+ @version $Id$
+ @see Richard E. McFarland, "A Standard Kinematic Model for Flight Simulation at
+ NASA-Ames", NASA CR-2497, January 1975
+ @see Barnes W. McCormick, "Aerodynamics, Aeronautics, and Flight Mechanics",
+ Wiley & Sons, 1979 ISBN 0-471-03032-5
+ @see W. A. Ragsdale, "A Generic Landing Gear Dynamics Model for LASRS++",
+ AIAA-2000-4303
+*/
+
+/*%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
+CLASS DECLARATION
+%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%*/
+
+class FGLGear : public FGJSBBase
{
public:
- FGLGear(FGConfigFile*, FGFDMExec*);
- ~FGLGear(void);
+ /// Brake grouping enumerators
+ enum BrakeGroup {bgNone=0, bgLeft, bgRight, bgCenter, bgNose, bgTail };
+ /// Steering group membership enumerators
+ enum SteerType {stSteer, stFixed, stCaster};
+ /// Report type enumerators
+ enum ReportType {erNone=0, erTakeoff, erLand};
+ /** Constructor
+ @param Executive a pointer to the parent executive object
+ @param File a pointer to the config file instance */
+ FGLGear(FGConfigFile* File, FGFDMExec* Executive);
+ /** Constructor
+ @param lgear a reference to an existing FGLGear object */
+ FGLGear(const FGLGear& lgear);
+ /// Destructor
+ ~FGLGear();
+
+
+ /// The Force vector for this gear
+ FGColumnVector3& Force(void);
+ /// The Moment vector for this gear
+ FGColumnVector3& Moment(void) {return vMoment;}
- FGColumnVector Force(void);
- FGColumnVector Moment(void) {return vMoment;}
+ /// Gets the location of the gear in Body axes
+ FGColumnVector3& GetBodyLocation(void) { return vWhlBodyVec; }
+ double GetBodyLocation(int idx) { return vWhlBodyVec(idx); }
+ FGColumnVector3& GetLocalGear(void) { return vLocalGear; }
+ double GetLocalGear(int idx) { return vLocalGear(idx); }
+
+ /// Gets the name of the gear
inline string GetName(void) {return name; }
+ /// Gets the Weight On Wheels flag value
inline bool GetWOW(void) {return WOW; }
- inline float GetCompLen(void) {return compressLength;}
- inline float GetCompVel(void) {return compressSpeed; }
- inline float GetCompForce(void) {return Force()(3); }
+ /// Gets the current compressed length of the gear in feet
+ inline double GetCompLen(void) {return compressLength;}
+ /// Gets the current gear compression velocity in ft/sec
+ inline double GetCompVel(void) {return compressSpeed; }
+ /// Gets the gear compression force in pounds
+ inline double GetCompForce(void) {return Force()(3); }
+ inline double GetBrakeFCoeff(void) {return BrakeFCoeff;}
+
+ /// Gets the current normalized tire pressure
+ inline double GetTirePressure(void) { return TirePressureNorm; }
+ /// Sets the new normalized tire pressure
+ inline void SetTirePressure(double p) { TirePressureNorm = p; }
+
+ /// Sets the brake value in percent (0 - 100)
+ inline void SetBrake(double bp) {brakePct = bp;}
+ /** Set the console touchdown reporting feature
+ @param flag true turns on touchdown reporting, false turns it off */
+ inline void SetReport(bool flag) { ReportEnable = flag; }
+ /** Get the console touchdown reporting feature
+ @return true if reporting is turned on */
+ inline bool GetReport(void) { return ReportEnable; }
+ inline double GetSteerAngle(void) { return SteerAngle;}
+ inline double GetstaticFCoeff(void) { return staticFCoeff;}
+
+ inline int GetBrakeGroup(void) { return (int)eBrakeGrp; }
+ inline int GetSteerType(void) { return (int)eSteerType; }
+
+ inline bool GetRetractable(void) { return isRetractable; }
+ inline bool GetGearUnitUp(void) { return GearUp; }
+ inline bool GetGearUnitDown(void) { return GearDown; }
+ inline double GetWheelSideForce(void) { return SideForce; }
+ inline double GetWheelRollForce(void) { return RollingForce; }
+ inline double GetBodyXForce(void) { return vLocalForce(eX); }
+ inline double GetBodyYForce(void) { return vLocalForce(eY); }
+ inline double GetWheelSlipAngle(void) { return WheelSlip; }
+ double GetWheelVel(int axis) { return vWhlVelVec(axis);}
+
private:
- enum {eX=1, eY, eZ};
- FGColumnVector vXYZ;
- FGColumnVector vMoment;
- float kSpring, bDamp, compressLength, compressSpeed;
- float statFCoeff, rollFCoeff, skidFCoeff;
- float frictionForce, compForce;
- float brakePct, brakeForce, brakeCoeff;
+ FGColumnVector3 vXYZ;
+ FGColumnVector3 vMoment;
+ FGColumnVector3 vWhlBodyVec;
+ FGColumnVector3 vLocalGear;
+ FGColumnVector3 vForce;
+ FGColumnVector3 vLocalForce;
+ FGColumnVector3 vWhlVelVec; // Velocity of this wheel (Local)
+ double SteerAngle;
+ double kSpring;
+ double bDamp;
+ double compressLength;
+ double compressSpeed;
+ double staticFCoeff, dynamicFCoeff, rollingFCoeff;
+ double brakePct;
+ double BrakeFCoeff;
+ double maxCompLen;
double SinkRate;
double GroundSpeed;
- double DistanceTraveled;
+ double TakeoffDistanceTraveled;
+ double TakeoffDistanceTraveled50ft;
+ double LandingDistanceTraveled;
double MaximumStrutForce;
double MaximumStrutTravel;
+ double SideWhlVel, RollingWhlVel;
+ double RollingForce, SideForce, FCoeff;
+ double WheelSlip;
+ double lastWheelSlip;
+ double TirePressureNorm;
bool WOW;
+ bool lastWOW;
bool FirstContact;
- bool Reported;
+ bool StartedGroundRun;
+ bool LandingReported;
+ bool TakeoffReported;
+ bool ReportEnable;
+ bool isRetractable;
+ bool GearUp, GearDown;
+ bool Servicable;
string name;
+ string sSteerType;
+ string sBrakeGroup;
+ string sRetractable;
+
+ BrakeGroup eBrakeGrp;
+ SteerType eSteerType;
+ double maxSteerAngle;
- FGFDMExec* Exec;
- FGState* State;
- FGAircraft* Aircraft;
- FGPosition* Position;
- FGRotation* Rotation;
+ FGFDMExec* Exec;
+ FGState* State;
+ FGAircraft* Aircraft;
+ FGPosition* Position;
+ FGRotation* Rotation;
+ FGFCS* FCS;
+ FGMassBalance* MassBalance;
- void Report(void);
+ void Report(ReportType rt);
+ void Debug(int from);
};
-
+}
#include "FGAircraft.h"
#include "FGPosition.h"
#include "FGRotation.h"
+#include "FGFCS.h"
+#include "FGMassBalance.h"
+
+//%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
+
+#include "FGState.h"
-/******************************************************************************/
#endif
projects / flightgear.git / blobdiff