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 aircraft state required to
36 maintain a specified flight condition. This flight condition can be
37 steady-level with non-zero sideslip, a steady turn, a pull-up or pushover.
38 On-ground conditions can be trimmed as well, but this is currently limited to
39 adjusting altitude and pitch angle only. It is implemented using an iterative,
40 one-axis-at-a-time scheme.
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53 #include "FGFDMExec.h"
54 #include "FGJSBBase.h"
55 #include "FGRotation.h"
56 #include "FGAtmosphere.h"
59 #include "FGAircraft.h"
60 #include "FGTranslation.h"
61 #include "FGPosition.h"
62 #include "FGAuxiliary.h"
65 #include "FGTrimAxis.h"
69 /*%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
71 %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%*/
73 #define ID_TRIM "$Id$"
75 typedef enum { tLongitudinal, tFull, tGround, tPullup,
80 #define snprintf _snprintf
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87 /*%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
88 COMMENTS, REFERENCES, and NOTES [use "class documentation" below for API docs]
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91 /*%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
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95 /** FGTrim -- the trimming routine for JSBSim.
96 FGTrim finds the aircraft attitude and control settings needed to maintain
97 the steady state described by the FGInitialCondition object . It does this
98 iteratively by assigning a control to each state and adjusting that control
99 until the state is within a specified tolerance of zero. States include the
100 recti-linear accelerations udot, vdot, and wdot, the angular accelerations
101 qdot, pdot, and rdot, and the difference between heading and ground track.
102 Controls include the usual flight deck controls available to the pilot plus
103 angle of attack (alpha), sideslip angle(beta), flight path angle (gamma),
104 pitch attitude(theta), roll attitude(phi), and altitude above ground. The
105 last three are used for on-ground trimming. The state-control pairs used in
106 a given trim are completely user configurable and several pre-defined modes
107 are provided as well. They are:
109 <li> tLongitudinal: Trim wdot with alpha, udot with thrust, qdot with elevator</li>
110 <li> tFull: tLongitudinal + vdot with phi, pdot with aileron, rdot with rudder
111 and heading minus ground track (hmgt) with beta</li>
112 <li> tPullup: tLongitudinal but adjust alpha to achieve load factor input
115 <li> tGround: wdot with altitude, qdot with theta, and pdot with phi</li>
117 The remaining modes include <b>tCustom</b>, which is completely user defined and
121 Note that trims can (and do) fail for reasons that are completely outside
122 the control of the trimming routine itself. The most common problem is the
123 initial conditions: is the model capable of steady state flight
124 at those conditions? Check the speed, altitude, configuration (flaps,
125 gear, etc.), weight, cg, and anything else that may be relevant.
128 FGFDMExec* FDMExec = new FGFDMExec();
132 FGInitialCondition* fgic = new FGInitialCondition(FDMExec);
133 FGTrim *fgt(FDMExec,fgic,tFull);
134 fgic->SetVcaibratedKtsIC(100);
135 fgic->SetAltitudeFtIC(1000);
136 fgic->SetClimbRate(500);
137 if( !fgt->DoTrim() ) {
138 cout << "Trim Failed" << endl;
145 /*%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
147 %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%*/
149 class FGTrim : public FGJSBBase
153 vector<FGTrimAxis*> TrimAxes;
154 unsigned int current_axis;
157 int DebugLevel, Debug;
158 double Tolerance, A_Tolerance;
159 double wdot,udot,qdot;
161 double *sub_iterations;
164 int max_sub_iterations;
170 unsigned int axis_count;
172 double xlo,xhi,alo,ahi;
176 double psidot,thetadot;
179 FGInitialCondition* fgic;
183 /** @return false if there is no change in the current axis accel
184 between accel(control_min) and accel(control_max). If there is a
185 change, sets solutionDomain to:
186 0 for no sign change,
187 -1 if sign change between accel(control_min) and accel(0)
188 1 if sign between accel(0) and accel(control_max)
190 bool findInterval(void);
192 bool checkLimits(void);
194 void setupPullup(void);
195 void setupTurn(void);
197 void updateRates(void);
202 /** Initializes the trimming class
203 @param FDMExec pointer to a JSBSim executive object.
204 @param FGIC pointer to a FGInitialCondition object
205 @param TrimMode the set of axes to trim. Can be:
206 tLongitudinal, tFull, tGround, tCustom, or tNone
208 FGTrim(FGFDMExec *FDMExec, FGInitialCondition *FGIC, TrimMode tt);
216 /** Print the results of the trim. For each axis trimmed, this
217 includes the final state value, control value, and tolerance
219 @return true if trim succeeds
223 /** Iteration statistics
227 /** Clear all state-control pairs from the current configuration.
228 The trimming routine must have at least one state-control pair
229 configured to be useful
231 void ClearStates(void);
233 /** Add a state-control pair to the current configuration. See the enums
234 State and Control in FGTrimAxis.h for the available options.
235 Will fail if the given state is already configured.
236 @param state the accel or other condition to zero
237 @param control the control used to zero the state
238 @return true if add is successful
240 bool AddState( State state, Control control );
242 /** Remove a specific state-control pair from the current configuration
243 @param state the state to remove
244 @return true if removal is successful
246 bool RemoveState( State state );
248 /** Change the control used to zero a state previously configured
249 @param state the accel or other condition to zero
250 @param control the control used to zero the state
252 bool EditState( State state, Control new_control );
254 /** automatically switch to trimming longitudinal acceleration with
255 flight path angle (gamma) once it becomes apparent that there
256 is not enough/too much thrust.
257 @param gamma_fallback true to enable fallback
259 inline void SetGammaFallback(bool bb) { gamma_fallback=true; }
261 /** query the fallback state
262 @return true if fallback is enabled.
264 inline bool GetGammaFallback(void) { return gamma_fallback; }
266 /** Set the iteration limit. DoTrim() will return false if limit
267 iterations are reached before trim is achieved. The default
268 is 60. This does not ordinarily need to be changed.
269 @param ii integer iteration limit
271 inline void SetMaxCycles(int ii) { max_iterations = ii; }
273 /** Set the per-axis iteration limit. Attempt to zero each state
274 by iterating limit times before moving on to the next. The
275 default limit is 100 and also does not ordinarily need to
277 @param ii integer iteration limit
279 inline void SetMaxCyclesPerAxis(int ii) { max_sub_iterations = ii; }
281 /** Set the tolerance for declaring a state trimmed. Angular accels are
282 held to a tolerance of 1/10th of the given. The default is
283 0.001 for the recti-linear accelerations and 0.0001 for the angular.
285 inline void SetTolerance(double tt) {
287 A_Tolerance = tt / 10;
291 Debug level 1 shows results of each top-level iteration
292 Debug level 2 shows level 1 & results of each per-axis iteration
294 inline void SetDebug(int level) { DebugLevel = level; }
295 inline void ClearDebug(void) { DebugLevel = 0; }
298 Output debug data for one of the axes
299 The State enum is defined in FGTrimAxis.h
301 inline void DebugState(State state) { debug_axis=state; }
303 inline void SetTargetNlf(float nlf) { targetNlf=nlf; }
304 inline double GetTargetNlf(void) { return targetNlf; }