Branch data Line data Source code
1 : : /*%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
2 : :
3 : : Header: FGLGear.h
4 : : Author: Jon S. Berndt
5 : : Date started: 11/18/99
6 : :
7 : : ------------- Copyright (C) 1999 Jon S. Berndt (jon@jsbsim.org) -------------
8 : :
9 : : This program is free software; you can redistribute it and/or modify it under
10 : : the terms of the GNU Lesser General Public License as published by the Free Software
11 : : Foundation; either version 2 of the License, or (at your option) any later
12 : : version.
13 : :
14 : : This program is distributed in the hope that it will be useful, but WITHOUT
15 : : ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or FITNESS
16 : : FOR A PARTICULAR PURPOSE. See the GNU Lesser General Public License for more
17 : : details.
18 : :
19 : : You should have received a copy of the GNU Lesser General Public License along with
20 : : this program; if not, write to the Free Software Foundation, Inc., 59 Temple
21 : : Place - Suite 330, Boston, MA 02111-1307, USA.
22 : :
23 : : Further information about the GNU Lesser General Public License can also be found on
24 : : the world wide web at http://www.gnu.org.
25 : :
26 : : HISTORY
27 : : --------------------------------------------------------------------------------
28 : : 11/18/99 JSB Created
29 : :
30 : : %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
31 : : SENTRY
32 : : %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%*/
33 : :
34 : : #ifndef FGLGEAR_H
35 : : #define FGLGEAR_H
36 : :
37 : : /*%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
38 : : INCLUDES
39 : : %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%*/
40 : :
41 : : #include "models/propulsion/FGForce.h"
42 : : #include "models/FGPropagate.h"
43 : : #include "math/FGColumnVector3.h"
44 : : #include <string>
45 : :
46 : : /*%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
47 : : DEFINITIONS
48 : : %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%*/
49 : :
50 : : #define ID_LGEAR "$Id: FGLGear.h,v 1.40 2010/07/30 11:50:01 jberndt Exp $"
51 : :
52 : : /*%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
53 : : FORWARD DECLARATIONS
54 : : %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%*/
55 : :
56 : : namespace JSBSim {
57 : :
58 : : class FGAircraft;
59 : : class FGPropagate;
60 : : class FGFCS;
61 : : class FGState;
62 : : class FGMassBalance;
63 : : class FGAuxiliary;
64 : : class FGTable;
65 : : class Element;
66 : :
67 : : /*%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
68 : : CLASS DOCUMENTATION
69 : : %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%*/
70 : :
71 : : /** Landing gear model.
72 : : Calculates forces and moments due to landing gear reactions. This is done in
73 : : several steps, and is dependent on what kind of gear is being modeled. Here
74 : : are the parameters that can be specified in the config file for modeling
75 : : landing gear:
76 : : <p>
77 : : <h3>Physical Characteristics</h3>
78 : : <ol>
79 : : <li>X, Y, Z location, in inches in structural coordinate frame</li>
80 : : <li>Spring constant, in lbs/ft</li>
81 : : <li>Damping coefficient, in lbs/ft/sec</li>
82 : : <li>Dynamic Friction Coefficient</li>
83 : : <li>Static Friction Coefficient</li>
84 : : </ol></p><p>
85 : : <h3>Operational Properties</h3>
86 : : <ol>
87 : : <li>Name</li>
88 : : <li>Brake Group Membership {one of LEFT | CENTER | RIGHT | NOSE | TAIL | NONE}</li>
89 : : <li>Max Steer Angle, in degrees</li>
90 : : </ol></p>
91 : : <p>
92 : : <h3>Algorithm and Approach to Modeling</h3>
93 : : <ol>
94 : : <li>Find the location of the uncompressed landing gear relative to the CG of
95 : : the aircraft. Remember, the structural coordinate frame that the aircraft is
96 : : defined in is: X positive towards the tail, Y positive out the right side, Z
97 : : positive upwards. The locations of the various parts are given in inches in
98 : : the config file.</li>
99 : : <li>The vector giving the location of the gear (relative to the cg) is
100 : : rotated 180 degrees about the Y axis to put the coordinates in body frame (X
101 : : positive forwards, Y positive out the right side, Z positive downwards, with
102 : : the origin at the cg). The lengths are also now given in feet.</li>
103 : : <li>The new gear location is now transformed to the local coordinate frame
104 : : using the body-to-local matrix. (Mb2l).</li>
105 : : <li>Knowing the location of the center of gravity relative to the ground
106 : : (height above ground level or AGL) now enables gear deflection to be
107 : : calculated. The gear compression value is the local frame gear Z location
108 : : value minus the height AGL. [Currently, we make the assumption that the gear
109 : : is oriented - and the deflection occurs in - the Z axis only. Additionally,
110 : : the vector to the landing gear is currently not modified - which would
111 : : (correctly) move the point of contact to the actual compressed-gear point of
112 : : contact. Eventually, articulated gear may be modeled, but initially an
113 : : effort must be made to model a generic system.] As an example, say the
114 : : aircraft left main gear location (in local coordinates) is Z = 3 feet
115 : : (positive) and the height AGL is 2 feet. This tells us that the gear is
116 : : compressed 1 foot.</li>
117 : : <li>If the gear is compressed, a Weight-On-Wheels (WOW) flag is set.</li>
118 : : <li>With the compression length calculated, the compression velocity may now
119 : : be calculated. This will be used to determine the damping force in the
120 : : strut. The aircraft rotational rate is multiplied by the vector to the wheel
121 : : to get a wheel velocity in body frame. That velocity vector is then
122 : : transformed into the local coordinate frame.</li>
123 : : <li>The aircraft cg velocity in the local frame is added to the
124 : : just-calculated wheel velocity (due to rotation) to get a total wheel
125 : : velocity in the local frame.</li>
126 : : <li>The compression speed is the Z-component of the vector.</li>
127 : : <li>With the wheel velocity vector no longer needed, it is normalized and
128 : : multiplied by a -1 to reverse it. This will be used in the friction force
129 : : calculation.</li>
130 : : <li>Since the friction force takes place solely in the runway plane, the Z
131 : : coordinate of the normalized wheel velocity vector is set to zero.</li>
132 : : <li>The gear deflection force (the force on the aircraft acting along the
133 : : local frame Z axis) is now calculated given the spring and damper
134 : : coefficients, and the gear deflection speed and stroke length. Keep in mind
135 : : that gear forces always act in the negative direction (in both local and
136 : : body frames), and are not capable of generating a force in the positive
137 : : sense (one that would attract the aircraft to the ground). So, the gear
138 : : forces are always negative - they are limited to values of zero or less. The
139 : : gear force is simply the negative of the sum of the spring compression
140 : : length times the spring coefficient and the gear velocity times the damping
141 : : coefficient.</li>
142 : : <li>The lateral/directional force acting on the aircraft through the landing
143 : :
144 : : gear (along the local frame X and Y axes) is calculated next. First, the
145 : : friction coefficient is multiplied by the recently calculated Z-force. This
146 : : is the friction force. It must be given direction in addition to magnitude.
147 : : We want the components in the local frame X and Y axes. From step 9, above,
148 : : the conditioned wheel velocity vector is taken and the X and Y parts are
149 : : multiplied by the friction force to get the X and Y components of friction.
150 : : </li>
151 : : <li>The wheel force in local frame is next converted to body frame.</li>
152 : : <li>The moment due to the gear force is calculated by multiplying r x F
153 : : (radius to wheel crossed into the wheel force). Both of these operands are
154 : : in body frame.</li>
155 : : </ol>
156 : :
157 : : <h3>Configuration File Format:</h3>
158 : : @code
159 : : <contact type="{BOGEY | STRUCTURE}" name="{string}">
160 : : <location unit="{IN | M}">
161 : : <x> {number} </x>
162 : : <y> {number} </y>
163 : : <z> {number} </z>
164 : : </location>
165 : : <orientation unit="{RAD | DEG}">
166 : : <pitch> {number} </pitch>
167 : : <roll> {number} </roll>
168 : : <yaw> {number} </yaw>
169 : : </orientation>
170 : : <static_friction> {number} </static_friction>
171 : : <dynamic_friction> {number} </dynamic_friction>
172 : : <rolling_friction> {number} </rolling_friction>
173 : : <spring_coeff unit="{LBS/FT | N/M}"> {number} </spring_coeff>
174 : : <damping_coeff [type="SQUARE"] unit="{LBS/FT/SEC | N/M/SEC}"> {number} </damping_coeff>
175 : : <damping_coeff_rebound [type="SQUARE"] unit="{LBS/FT/SEC | N/M/SEC}"> {number} </damping_coeff_rebound>
176 : : <max_steer unit="DEG"> {number | 0 | 360} </max_steer>
177 : : <brake_group> {NONE | LEFT | RIGHT | CENTER | NOSE | TAIL} </brake_group>
178 : : <retractable>{0 | 1}</retractable>
179 : : <table type="{CORNERING_COEFF}">
180 : : </table>
181 : : </contact>
182 : : @endcode
183 : : @author Jon S. Berndt
184 : : @version $Id: FGLGear.h,v 1.40 2010/07/30 11:50:01 jberndt Exp $
185 : : @see Richard E. McFarland, "A Standard Kinematic Model for Flight Simulation at
186 : : NASA-Ames", NASA CR-2497, January 1975
187 : : @see Barnes W. McCormick, "Aerodynamics, Aeronautics, and Flight Mechanics",
188 : : Wiley & Sons, 1979 ISBN 0-471-03032-5
189 : : @see W. A. Ragsdale, "A Generic Landing Gear Dynamics Model for LASRS++",
190 : : AIAA-2000-4303
191 : : */
192 : :
193 : : /*%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
194 : : CLASS DECLARATION
195 : : %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%*/
196 : :
197 : : class FGLGear : public FGForce
198 : : {
199 : : public:
200 : : /// Brake grouping enumerators
201 : : enum BrakeGroup {bgNone=0, bgLeft, bgRight, bgCenter, bgNose, bgTail };
202 : : /// Steering group membership enumerators
203 : : enum SteerType {stSteer, stFixed, stCaster};
204 : : /// Contact point type
205 : : enum ContactType {ctBOGEY, ctSTRUCTURE};
206 : : /// Report type enumerators
207 : : enum ReportType {erNone=0, erTakeoff, erLand};
208 : : /// Damping types
209 : : enum DampType {dtLinear=0, dtSquare};
210 : : /// Friction types
211 : : enum FrictionType {ftRoll=0, ftSide, ftDynamic};
212 : : /** Constructor
213 : : @param el a pointer to the XML element that contains the CONTACT info.
214 : : @param Executive a pointer to the parent executive object
215 : : @param number integer identifier for this instance of FGLGear
216 : : */
217 : : FGLGear(Element* el, FGFDMExec* Executive, int number);
218 : : /// Destructor
219 : : ~FGLGear();
220 : :
221 : : /// The Force vector for this gear
222 : : FGColumnVector3& GetBodyForces(void);
223 : :
224 : : /// Gets the location of the gear in Body axes
225 : : FGColumnVector3& GetBodyLocation(void) { return vWhlBodyVec; }
226 : 0 : double GetBodyLocation(int idx) const { return vWhlBodyVec(idx); }
227 : :
228 : : FGColumnVector3& GetLocalGear(void) { return vLocalGear; }
229 : 0 : double GetLocalGear(int idx) const { return vLocalGear(idx); }
230 : :
231 : : /// Gets the name of the gear
232 : 0 : string GetName(void) const {return name; }
233 : : /// Gets the Weight On Wheels flag value
234 : 0 : bool GetWOW(void) const {return WOW; }
235 : : /// Gets the current compressed length of the gear in feet
236 : 0 : double GetCompLen(void) const {return compressLength;}
237 : : /// Gets the current gear compression velocity in ft/sec
238 : 0 : double GetCompVel(void) const {return compressSpeed; }
239 : : /// Gets the gear compression force in pounds
240 : 0 : double GetCompForce(void) const {return StrutForce; }
241 : : double GetBrakeFCoeff(void) const {return BrakeFCoeff;}
242 : :
243 : : /// Gets the current normalized tire pressure
244 : : double GetTirePressure(void) const { return TirePressureNorm; }
245 : : /// Sets the new normalized tire pressure
246 : : void SetTirePressure(double p) { TirePressureNorm = p; }
247 : :
248 : : /// Sets the brake value in percent (0 - 100)
249 : : void SetBrake(double bp) {brakePct = bp;}
250 : :
251 : : /// Sets the weight-on-wheels flag.
252 : : void SetWOW(bool wow) {WOW = wow;}
253 : :
254 : : /** Set the console touchdown reporting feature
255 : : @param flag true turns on touchdown reporting, false turns it off */
256 : 0 : void SetReport(bool flag) { ReportEnable = flag; }
257 : : /** Get the console touchdown reporting feature
258 : : @return true if reporting is turned on */
259 : : bool GetReport(void) const { return ReportEnable; }
260 : 0 : double GetSteerNorm(void) const { return radtodeg/maxSteerAngle*SteerAngle; }
261 : 0 : double GetDefaultSteerAngle(double cmd) const { return cmd*maxSteerAngle; }
262 : : double GetstaticFCoeff(void) const { return staticFCoeff; }
263 : :
264 : : int GetBrakeGroup(void) const { return (int)eBrakeGrp; }
265 : : int GetSteerType(void) const { return (int)eSteerType; }
266 : :
267 : 0 : bool GetSteerable(void) const { return eSteerType != stFixed; }
268 : : bool GetRetractable(void) const { return isRetractable; }
269 : : bool GetGearUnitUp(void) const { return GearUp; }
270 : 0 : bool GetGearUnitDown(void) const { return GearDown; }
271 : : double GetWheelRollForce(void) {
272 : 0 : FGColumnVector3 vForce = mTGear.Transposed() * FGForce::GetBodyForces();
273 : 0 : return vForce(eX)*cos(SteerAngle) + vForce(eY)*sin(SteerAngle); }
274 : : double GetWheelSideForce(void) {
275 : 0 : FGColumnVector3 vForce = mTGear.Transposed() * FGForce::GetBodyForces();
276 : 0 : return vForce(eY)*cos(SteerAngle) - vForce(eX)*sin(SteerAngle); }
277 : 0 : double GetWheelRollVel(void) const { return vWhlVelVec(eX)*cos(SteerAngle)
278 : 0 : + vWhlVelVec(eY)*sin(SteerAngle); }
279 : : double GetWheelSideVel(void) const { return vWhlVelVec(eY)*cos(SteerAngle)
280 : 0 : - vWhlVelVec(eX)*sin(SteerAngle); }
281 : 0 : double GetWheelSlipAngle(void) const { return WheelSlip; }
282 : 0 : double GetWheelVel(int axis) const { return vWhlVelVec(axis);}
283 : 0 : bool IsBogey(void) const { return (eContactType == ctBOGEY);}
284 : : double GetGearUnitPos(void);
285 : 0 : double GetSteerAngleDeg(void) const { return radtodeg*SteerAngle; }
286 : : FGPropagate::LagrangeMultiplier* GetMultiplierEntry(int entry);
287 : : void SetLagrangeMultiplier(double lambda, int entry);
288 : : FGColumnVector3& UpdateForces(void);
289 : :
290 : : void bind(void);
291 : :
292 : : private:
293 : : int GearNumber;
294 : : static const FGMatrix33 Tb2s;
295 : : FGMatrix33 mTGear;
296 : : FGColumnVector3 vGearOrient;
297 : : FGColumnVector3 vWhlBodyVec;
298 : : FGColumnVector3 vLocalGear;
299 : : FGColumnVector3 vWhlVelVec, vLocalWhlVel; // Velocity of this wheel
300 : : FGColumnVector3 normal, cvel, vGroundNormal;
301 : : FGLocation contact, gearLoc;
302 : : FGTable *ForceY_Table;
303 : : double dT;
304 : : double SteerAngle;
305 : : double kSpring;
306 : : double bDamp;
307 : : double bDampRebound;
308 : : double compressLength;
309 : : double compressSpeed;
310 : : double staticFCoeff, dynamicFCoeff, rollingFCoeff;
311 : : double Stiffness, Shape, Peak, Curvature; // Pacejka factors
312 : : double brakePct;
313 : : double BrakeFCoeff;
314 : : double maxCompLen;
315 : : double SinkRate;
316 : : double GroundSpeed;
317 : : double TakeoffDistanceTraveled;
318 : : double TakeoffDistanceTraveled50ft;
319 : : double LandingDistanceTraveled;
320 : : double MaximumStrutForce, StrutForce;
321 : : double MaximumStrutTravel;
322 : : double FCoeff;
323 : : double WheelSlip;
324 : : double TirePressureNorm;
325 : : double GearPos;
326 : : bool useFCSGearPos;
327 : : bool WOW;
328 : : bool lastWOW;
329 : : bool FirstContact;
330 : : bool StartedGroundRun;
331 : : bool LandingReported;
332 : : bool TakeoffReported;
333 : : bool ReportEnable;
334 : : bool isRetractable;
335 : : bool GearUp, GearDown;
336 : : bool Servicable;
337 : : bool Castered;
338 : : bool StaticFriction;
339 : : std::string name;
340 : : std::string sSteerType;
341 : : std::string sBrakeGroup;
342 : : std::string sRetractable;
343 : : std::string sContactType;
344 : :
345 : : BrakeGroup eBrakeGrp;
346 : : ContactType eContactType;
347 : : SteerType eSteerType;
348 : : DampType eDampType;
349 : : DampType eDampTypeRebound;
350 : : double maxSteerAngle;
351 : :
352 : : FGPropagate::LagrangeMultiplier LMultiplier[3];
353 : :
354 : : FGAuxiliary* Auxiliary;
355 : : FGPropagate* Propagate;
356 : : FGFCS* FCS;
357 : : FGMassBalance* MassBalance;
358 : : FGGroundReactions* GroundReactions;
359 : :
360 : : void ComputeRetractionState(void);
361 : : void ComputeBrakeForceCoefficient(void);
362 : : void ComputeSteeringAngle(void);
363 : : void ComputeSlipAngle(void);
364 : : void ComputeSideForceCoefficient(void);
365 : : void ComputeVerticalStrutForce(void);
366 : : void ComputeGroundCoordSys(void);
367 : : void ComputeJacobian(const FGColumnVector3& vWhlContactVec);
368 : : void CrashDetect(void);
369 : : void InitializeReporting(void);
370 : : void ResetReporting(void);
371 : : void ReportTakeoffOrLanding(void);
372 : : void Report(ReportType rt);
373 : : void Debug(int from);
374 : : };
375 : : }
376 : :
377 : : //%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
378 : :
379 : : #endif
|
