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 %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%*/
47 /*%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
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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, tCustom, tNone } TrimMode;
76 #define snprintf _snprintf
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83 /*%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
84 COMMENTS, REFERENCES, and NOTES [use "class documentation" below for API docs]
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87 /*%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
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91 /** FGTrim -- the trimming routine for JSBSim.
92 FGTrim finds the aircraft attitude and control settings needed to maintain
93 the steady state described by the FGInitialCondition object . It does this
94 iteratively by assigning a control to each state and adjusting that control
95 until the state is within a specified tolerance of zero. States include the
96 recti-linear accelerations udot, vdot, and wdot, the angular accelerations
97 qdot, pdot, and rdot, and the difference between heading and ground track.
98 Controls include the usual flight deck controls available to the pilot plus
99 angle of attack (alpha), sideslip angle(beta), flight path angle (gamma),
100 pitch attitude(theta), roll attitude(phi), and altitude above ground. The
101 last three are used for on-ground trimming. The state-control pairs used in
102 a given trim are completely user configurable and several pre-defined modes
103 are provided as well. They are:
105 <li> tLongitudinal: Trim wdot with alpha, udot with thrust, qdot with elevator</li>
106 <li> tFull: tLongitudinal + vdot with phi, pdot with aileron, rdot with rudder
107 and heading minus ground track (hmgt) with beta</li>
108 <li> tGround: wdot with altitude, qdot with theta, and pdot with phi</li>
109 The remaining modes include <b>tCustom</b>, which is completely user defined and
112 Currently, this class cannot trim a non-1g condition and is limited to
113 trimming for constant true airspeed in climbs and descents.
115 Note that trims can (and do) fail for reasons that are completely outside
116 the control of the trimming routine itself. The most common problem is the
117 initial conditions: is the model capable of steady state flight
118 at those conditions? Check the speed, altitude, configuration (flaps,
119 gear, etc.), weight, cg, and anything else that may be relevant.
122 FGFDMExec* FDMExec = new FGFDMExec();
126 FGInitialCondition* fgic = new FGInitialCondition(FDMExec);
127 FGTrim *fgt(FDMExec,fgic,tFull);
128 fgic->SetVcaibratedKtsIC(100);
129 fgic->SetAltitudeFtIC(1000);
130 fgic->SetClimbRate(500);
131 if( !fgt->DoTrim() ) {
132 cout << "Trim Failed" << endl;
139 /*%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
141 %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%*/
143 class FGTrim : public FGJSBBase
147 vector<FGTrimAxis*> TrimAxes;
152 double Tolerance, A_Tolerance;
153 double wdot,udot,qdot;
155 double *sub_iterations;
158 int max_sub_iterations;
166 double xlo,xhi,alo,ahi;
169 FGInitialCondition* fgic;
173 /** @return false if there is no change in the current axis accel
174 between accel(control_min) and accel(control_max). If there is a
175 change, sets solutionDomain to:
176 0 for no sign change,
177 -1 if sign change between accel(control_min) and accel(0)
178 1 if sign between accel(0) and accel(control_max)
180 bool findInterval(void);
182 bool checkLimits(void);
185 /** Initializes the trimming class
186 @param FDMExec pointer to a JSBSim executive object.
187 @param FGIC pointer to a FGInitialCondition object
188 @param TrimMode the set of axes to trim. Can be:
189 tLongitudinal, tFull, tGround, tCustom, or tNone
191 FGTrim(FGFDMExec *FDMExec, FGInitialCondition *FGIC, TrimMode tt);
199 /** Print the results of the trim. For each axis trimmed, this
200 includes the final state value, control value, and tolerance
202 @return true if trim succeeds
206 /** Iteration statistics
210 /** Clear all state-control pairs from the current configuration.
211 The trimming routine must have at least one state-control pair
212 configured to be useful
214 void ClearStates(void);
216 /** Add a state-control pair to the current configuration. See the enums
217 State and Control in FGTrimAxis.h for the available options.
218 Will fail if the given state is already configured.
219 @param state the accel or other condition to zero
220 @param control the control used to zero the state
221 @return true if add is successful
223 bool AddState( State state, Control control );
225 /** Remove a specific state-control pair from the current configuration
226 @param state the state to remove
227 @return true if removal is successful
229 bool RemoveState( State state );
231 /** Change the control used to zero a state previously configured
232 @param state the accel or other condition to zero
233 @param control the control used to zero the state
235 bool EditState( State state, Control new_control );
237 /** automatically switch to trimming longitudinal acceleration with
238 flight path angle (gamma) once it becomes apparent that there
239 is not enough/too much thrust.
240 @param gamma_fallback true to enable fallback
242 inline void SetGammaFallback(bool bb) { gamma_fallback=true; }
244 /** query the fallback state
245 @return true if fallback is enabled.
247 inline bool GetGammaFallback(void) { return gamma_fallback; }
249 /** Set the iteration limit. DoTrim() will return false if limit
250 iterations are reached before trim is achieved. The default
251 is 60. This does not ordinarily need to be changed.
252 @param ii integer iteration limit
254 inline void SetMaxCycles(int ii) { max_iterations = ii; }
256 /** Set the per-axis iteration limit. Attempt to zero each state
257 by iterating limit times before moving on to the next. The
258 default limit is 100 and also does not ordinarily need to
260 @param ii integer iteration limit
262 inline void SetMaxCyclesPerAxis(int ii) { max_sub_iterations = ii; }
264 /** Set the tolerance for declaring a state trimmed. Angular accels are
265 held to a tolerance of 1/10th of the given. The default is
266 0.001 for the recti-linear accelerations and 0.0001 for the angular.
268 inline void SetTolerance(double tt) {
270 A_Tolerance = tt / 10;
273 //Debug level 1 shows results of each top-level iteration
274 //Debug level 2 shows level 1 & results of each per-axis iteration
275 inline void SetDebug(int level) { Debug = level; }
276 inline void ClearDebug(void) { Debug = 0; }