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
40 %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
42 %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%*/
47 /*%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
49 %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%*/
51 #include "FGFDMExec.h"
52 #include "FGRotation.h"
53 #include "FGAtmosphere.h"
56 #include "FGAircraft.h"
57 #include "FGTranslation.h"
58 #include "FGPosition.h"
59 #include "FGAuxiliary.h"
62 #include "FGTrimAxis.h"
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68 %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%*/
70 #define ID_TRIM "$Id$"
72 /*%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
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76 typedef enum { tLongitudinal, tFull, tGround, tCustom, tNone } TrimMode;
78 /*%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
79 COMMENTS, REFERENCES, and NOTES [use "class documentation" below for API docs]
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82 /*%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
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86 /** FGTrim -- the trimming routine for JSBSim.
87 FGTrim finds the aircraft attitude and control settings needed to maintain
88 the steady state described by the FGInitialCondition object . It does this
89 iteratively by assigning a control to each state and adjusting that control
90 until the state is within a specified tolerance of zero. States include the
91 recti-linear accelerations udot, vdot, and wdot, the angular accelerations
92 qdot, pdot, and rdot, and the difference between heading and ground track.
93 Controls include the usual flight deck controls available to the pilot plus
94 angle of attack (alpha), sideslip angle(beta), flight path angle (gamma),
95 pitch attitude(theta), roll attitude(phi), and altitude above ground. The
96 last three are used for on-ground trimming. The state-control pairs used in
97 a given trim are completely user configurable and several pre-defined modes
98 are provided as well. They are:
100 <li> tLongitudinal: Trim wdot with alpha, udot with thrust, qdot with elevator</li>
101 <li> tFull: tLongitudinal + vdot with phi, pdot with aileron, rdot with rudder
102 and heading minus ground track (hmgt) with beta</li>
103 <li> tGround: wdot with altitude, qdot with theta, and pdot with phi</li>
104 The remaining modes include <b>tCustom</b>, which is completely user defined and
107 Currently, this class cannot trim a non-1g condition and is limited to
108 trimming for constant true airspeed in climbs and descents.
110 Note that trims can (and do) fail for reasons that are completely outside
111 the control of the trimming routine itself. The most common problem is the
112 initial conditions: is the model capable of steady state flight
113 at those conditions? Check the speed, altitude, configuration (flaps,
114 gear, etc.), weight, cg, and anything else that may be relevant.
117 FGFDMExec* FDMExec = new FGFDMExec();
121 FGInitialCondition* fgic = new FGInitialCondition(FDMExec);
122 FGTrim *fgt(FDMExec,fgic,tFull);
123 fgic->SetVcaibratedKtsIC(100);
124 fgic->SetAltitudeFtIC(1000);
125 fgic->SetClimbRate(500);
126 if( !fgt->DoTrim() ) {
127 cout << "Trim Failed" << endl;
134 /*%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
136 %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%*/
141 vector<FGTrimAxis*> TrimAxes;
146 float Tolerance, A_Tolerance;
147 float wdot,udot,qdot;
149 float *sub_iterations;
152 int max_sub_iterations;
160 float xlo,xhi,alo,ahi;
163 FGInitialCondition* fgic;
167 /** @return false if there is no change in the current axis accel
168 between accel(control_min) and accel(control_max). If there is a
169 change, sets solutionDomain to:
170 0 for no sign change,
171 -1 if sign change between accel(control_min) and accel(0)
172 1 if sign between accel(0) and accel(control_max)
174 bool findInterval(void);
176 bool checkLimits(void);
179 /** Initializes the trimming class
180 @param FDMExec pointer to a JSBSim executive object.
181 @param FGIC pointer to a FGInitialCondition object
182 @param TrimMode the set of axes to trim. Can be:
183 tLongitudinal, tFull, tGround, tCustom, or tNone
185 FGTrim(FGFDMExec *FDMExec, FGInitialCondition *FGIC, TrimMode tt);
193 /** Print the results of the trim. For each axis trimmed, this
194 includes the final state value, control value, and tolerance
196 @return true if trim succeeds
200 /** Prints a summary of simulator state (speed, altitude,
203 void ReportState(void);
205 /** Iteration statistics
209 /** Clear all state-control pairs from the current configuration.
210 The trimming routine must have at least one state-control pair
211 configured to be useful
213 void ClearStates(void);
215 /** Add a state-control pair to the current configuration. See the enums
216 State and Control in FGTrimAxis.h for the available options.
217 Will fail if the given state is already configured.
218 @param state the accel or other condition to zero
219 @param control the control used to zero the state
220 @return true if add is successful
222 bool AddState( State state, Control control );
224 /** Remove a specific state-control pair from the current configuration
225 @param state the state to remove
226 @return true if removal is successful
228 bool RemoveState( State state );
230 /** Change the control used to zero a state previously configured
231 @param state the accel or other condition to zero
232 @param control the control used to zero the state
234 bool EditState( State state, Control new_control );
236 /** automatically switch to trimming longitudinal acceleration with
237 flight path angle (gamma) once it becomes apparent that there
238 is not enough/too much thrust.
239 @param gamma_fallback true to enable fallback
241 inline void SetGammaFallback(bool bb) { gamma_fallback=true; }
243 /** query the fallback state
244 @return true if fallback is enabled.
246 inline bool GetGammaFallback(void) { return gamma_fallback; }
248 /** Set the iteration limit. DoTrim() will return false if limit
249 iterations are reached before trim is achieved. The default
250 is 60. This does not ordinarily need to be changed.
251 @param ii integer iteration limit
253 inline void SetMaxCycles(int ii) { max_iterations = ii; }
255 /** Set the per-axis iteration limit. Attempt to zero each state
256 by iterating limit times before moving on to the next. The
257 default limit is 100 and also does not ordinarily need to
259 @param ii integer iteration limit
261 inline void SetMaxCyclesPerAxis(int ii) { max_sub_iterations = ii; }
263 /** Set the tolerance for declaring a state trimmed. Angular accels are
264 held to a tolerance of 1/10th of the given. The default is
265 0.001 for the recti-linear accelerations and 0.0001 for the angular.
267 inline void SetTolerance(float tt) {
269 A_Tolerance = tt / 10;
272 //Debug level 1 shows results of each top-level iteration
273 //Debug level 2 shows level 1 & results of each per-axis iteration
274 inline void SetDebug(int level) { Debug = level; }
275 inline void ClearDebug(void) { Debug = 0; }