1 /*%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
7 ------------- Copyright (C) 1999 Anthony K. Peden (apeden@earthlink.net) -------------
9 This program is free software; you can redistribute it and/or modify it under
10 the terms of the GNU General Public License as published by the Free Software
11 Foundation; either version 2 of the License, or (at your option) any later
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 General Public License for more
19 You should have received a copy of the GNU 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.
23 Further information about the GNU General Public License can also be found on
24 the world wide web at http://www.gnu.org.
28 --------------------------------------------------------------------------------
32 FUNCTIONAL DESCRIPTION
33 --------------------------------------------------------------------------------
35 This class takes the given set of IC's and finds the angle of attack, elevator,
36 and throttle setting required to fly steady level. This is currently for in-air
37 conditions only. It is implemented using an iterative, one-axis-at-a-time
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42 %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%*/
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51 #include "FGFDMExec.h"
52 #include "FGJSBBase.h"
53 #include "FGRotation.h"
54 #include "FGAtmosphere.h"
57 #include "FGAircraft.h"
58 #include "FGTranslation.h"
59 #include "FGPosition.h"
60 #include "FGAuxiliary.h"
63 #include "FGTrimAxis.h"
67 /*%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
69 %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%*/
71 #define ID_TRIM "$Id$"
73 typedef enum { tLongitudinal, tFull, tGround, tPullup,
78 #define snprintf _snprintf
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85 /*%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
86 COMMENTS, REFERENCES, and NOTES [use "class documentation" below for API docs]
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93 /** FGTrim -- the trimming routine for JSBSim.
94 FGTrim finds the aircraft attitude and control settings needed to maintain
95 the steady state described by the FGInitialCondition object . It does this
96 iteratively by assigning a control to each state and adjusting that control
97 until the state is within a specified tolerance of zero. States include the
98 recti-linear accelerations udot, vdot, and wdot, the angular accelerations
99 qdot, pdot, and rdot, and the difference between heading and ground track.
100 Controls include the usual flight deck controls available to the pilot plus
101 angle of attack (alpha), sideslip angle(beta), flight path angle (gamma),
102 pitch attitude(theta), roll attitude(phi), and altitude above ground. The
103 last three are used for on-ground trimming. The state-control pairs used in
104 a given trim are completely user configurable and several pre-defined modes
105 are provided as well. They are:
107 <li> tLongitudinal: Trim wdot with alpha, udot with thrust, qdot with elevator</li>
108 <li> tFull: tLongitudinal + vdot with phi, pdot with aileron, rdot with rudder
109 and heading minus ground track (hmgt) with beta</li>
110 <li> tGround: wdot with altitude, qdot with theta, and pdot with phi</li>
111 The remaining modes include <b>tCustom</b>, which is completely user defined and
114 Currently, this class cannot trim a non-1g condition and is limited to
115 trimming for constant true airspeed in climbs and descents.
117 Note that trims can (and do) fail for reasons that are completely outside
118 the control of the trimming routine itself. The most common problem is the
119 initial conditions: is the model capable of steady state flight
120 at those conditions? Check the speed, altitude, configuration (flaps,
121 gear, etc.), weight, cg, and anything else that may be relevant.
124 FGFDMExec* FDMExec = new FGFDMExec();
128 FGInitialCondition* fgic = new FGInitialCondition(FDMExec);
129 FGTrim *fgt(FDMExec,fgic,tFull);
130 fgic->SetVcaibratedKtsIC(100);
131 fgic->SetAltitudeFtIC(1000);
132 fgic->SetClimbRate(500);
133 if( !fgt->DoTrim() ) {
134 cout << "Trim Failed" << endl;
141 /*%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
143 %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%*/
145 class FGTrim : public FGJSBBase
149 vector<FGTrimAxis*> TrimAxes;
150 unsigned int current_axis;
153 int DebugLevel, Debug;
154 double Tolerance, A_Tolerance;
155 double wdot,udot,qdot;
157 double *sub_iterations;
160 int max_sub_iterations;
166 unsigned int axis_count;
168 double xlo,xhi,alo,ahi;
173 FGInitialCondition* fgic;
177 /** @return false if there is no change in the current axis accel
178 between accel(control_min) and accel(control_max). If there is a
179 change, sets solutionDomain to:
180 0 for no sign change,
181 -1 if sign change between accel(control_min) and accel(0)
182 1 if sign between accel(0) and accel(control_max)
184 bool findInterval(void);
186 bool checkLimits(void);
188 void setupPullup(void);
189 void setupTurn(void);
194 /** Initializes the trimming class
195 @param FDMExec pointer to a JSBSim executive object.
196 @param FGIC pointer to a FGInitialCondition object
197 @param TrimMode the set of axes to trim. Can be:
198 tLongitudinal, tFull, tGround, tCustom, or tNone
200 FGTrim(FGFDMExec *FDMExec, FGInitialCondition *FGIC, TrimMode tt);
208 /** Print the results of the trim. For each axis trimmed, this
209 includes the final state value, control value, and tolerance
211 @return true if trim succeeds
215 /** Iteration statistics
219 /** Clear all state-control pairs from the current configuration.
220 The trimming routine must have at least one state-control pair
221 configured to be useful
223 void ClearStates(void);
225 /** Add a state-control pair to the current configuration. See the enums
226 State and Control in FGTrimAxis.h for the available options.
227 Will fail if the given state is already configured.
228 @param state the accel or other condition to zero
229 @param control the control used to zero the state
230 @return true if add is successful
232 bool AddState( State state, Control control );
234 /** Remove a specific state-control pair from the current configuration
235 @param state the state to remove
236 @return true if removal is successful
238 bool RemoveState( State state );
240 /** Change the control used to zero a state previously configured
241 @param state the accel or other condition to zero
242 @param control the control used to zero the state
244 bool EditState( State state, Control new_control );
246 /** automatically switch to trimming longitudinal acceleration with
247 flight path angle (gamma) once it becomes apparent that there
248 is not enough/too much thrust.
249 @param gamma_fallback true to enable fallback
251 inline void SetGammaFallback(bool bb) { gamma_fallback=true; }
253 /** query the fallback state
254 @return true if fallback is enabled.
256 inline bool GetGammaFallback(void) { return gamma_fallback; }
258 /** Set the iteration limit. DoTrim() will return false if limit
259 iterations are reached before trim is achieved. The default
260 is 60. This does not ordinarily need to be changed.
261 @param ii integer iteration limit
263 inline void SetMaxCycles(int ii) { max_iterations = ii; }
265 /** Set the per-axis iteration limit. Attempt to zero each state
266 by iterating limit times before moving on to the next. The
267 default limit is 100 and also does not ordinarily need to
269 @param ii integer iteration limit
271 inline void SetMaxCyclesPerAxis(int ii) { max_sub_iterations = ii; }
273 /** Set the tolerance for declaring a state trimmed. Angular accels are
274 held to a tolerance of 1/10th of the given. The default is
275 0.001 for the recti-linear accelerations and 0.0001 for the angular.
277 inline void SetTolerance(double tt) {
279 A_Tolerance = tt / 10;
283 Debug level 1 shows results of each top-level iteration
284 Debug level 2 shows level 1 & results of each per-axis iteration
286 inline void SetDebug(int level) { DebugLevel = level; }
287 inline void ClearDebug(void) { DebugLevel = 0; }
290 Output debug data for one of the axes
291 The State enum is defined in FGTrimAxis.h
293 inline void DebugState(State state) { debug_axis=state; }
295 inline void SetTargetNlf(float nlf) { targetNlf=nlf; }
296 inline double GetTargetNlf(void) { return targetNlf; }