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 Lesser 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 Lesser General Public License for more
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.
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.
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.
42 %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
44 %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%*/
49 /*%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
51 %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%*/
53 #include "FGFDMExec.h"
54 #include "FGJSBBase.h"
55 #include "FGTrimAxis.h"
59 /*%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
61 %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%*/
63 #define ID_TRIM "$Id$"
65 #if defined(_WIN32) && !defined(__CYGWIN__)
66 #define snprintf _snprintf
69 /*%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
71 %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%*/
75 typedef enum { tLongitudinal=0, tFull, tGround, tPullup,
76 tCustom, tTurn, tNone } TrimMode;
78 /*%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
80 %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%*/
82 /** The trimming routine for JSBSim.
83 FGTrim finds the aircraft attitude and control settings needed to maintain
84 the steady state described by the FGInitialCondition object . It does this
85 iteratively by assigning a control to each state and adjusting that control
86 until the state is within a specified tolerance of zero. States include the
87 recti-linear accelerations udot, vdot, and wdot, the angular accelerations
88 qdot, pdot, and rdot, and the difference between heading and ground track.
89 Controls include the usual flight deck controls available to the pilot plus
90 angle of attack (alpha), sideslip angle(beta), flight path angle (gamma),
91 pitch attitude(theta), roll attitude(phi), and altitude above ground. The
92 last three are used for on-ground trimming. The state-control pairs used in
93 a given trim are completely user configurable and several pre-defined modes
94 are provided as well. They are:
95 - tLongitudinal: Trim wdot with alpha, udot with thrust, qdot with elevator
96 - tFull: tLongitudinal + vdot with phi, pdot with aileron, rdot with rudder
97 and heading minus ground track (hmgt) with beta
98 - tPullup: tLongitudinal but adjust alpha to achieve load factor input
100 - tGround: wdot with altitude, qdot with theta, and pdot with phi
102 The remaining modes include <b>tCustom</b>, which is completely user defined and
105 Note that trims can (and do) fail for reasons that are completely outside
106 the control of the trimming routine itself. The most common problem is the
107 initial conditions: is the model capable of steady state flight
108 at those conditions? Check the speed, altitude, configuration (flaps,
109 gear, etc.), weight, cg, and anything else that may be relevant.
113 FGFDMExec* FDMExec = new FGFDMExec();
115 FGInitialCondition* fgic = new FGInitialCondition(FDMExec);
116 FGTrim fgt(FDMExec, fgic, tFull);
117 fgic->SetVcaibratedKtsIC(100);
118 fgic->SetAltitudeFtIC(1000);
119 fgic->SetClimbRate(500);
120 if( !fgt.DoTrim() ) {
121 cout << "Trim Failed" << endl;
130 /*%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
132 %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%*/
134 class FGTrim : public FGJSBBase
138 vector<FGTrimAxis*> TrimAxes;
139 unsigned int current_axis;
142 int DebugLevel, Debug;
143 double Tolerance, A_Tolerance;
144 double wdot,udot,qdot;
146 double *sub_iterations;
149 int max_sub_iterations;
155 unsigned int axis_count;
157 double xlo,xhi,alo,ahi;
161 double psidot,thetadot;
164 FGInitialCondition* fgic;
168 /** @return false if there is no change in the current axis accel
169 between accel(control_min) and accel(control_max). If there is a
170 change, sets solutionDomain to:
171 0 for no sign change,
172 -1 if sign change between accel(control_min) and accel(0)
173 1 if sign between accel(0) and accel(control_max)
175 bool findInterval(void);
177 bool checkLimits(void);
179 void setupPullup(void);
180 void setupTurn(void);
182 void updateRates(void);
187 /** Initializes the trimming class
188 @param FDMExec pointer to a JSBSim executive object.
191 FGTrim(FGFDMExec *FDMExec, TrimMode tm=tGround );
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 and set a predefined trim mode
211 @param tm the set of axes to trim. Can be:
212 tLongitudinal, tFull, tGround, tCustom, or tNone
214 void SetMode(TrimMode tm);
216 /** Clear all state-control pairs from the current configuration.
217 The trimming routine must have at least one state-control pair
218 configured to be useful
220 void ClearStates(void);
222 /** Add a state-control pair to the current configuration. See the enums
223 State and Control in FGTrimAxis.h for the available options.
224 Will fail if the given state is already configured.
225 @param state the accel or other condition to zero
226 @param control the control used to zero the state
227 @return true if add is successful
229 bool AddState( State state, Control control );
231 /** Remove a specific state-control pair from the current configuration
232 @param state the state to remove
233 @return true if removal is successful
235 bool RemoveState( State state );
237 /** Change the control used to zero a state previously configured
238 @param state the accel or other condition to zero
239 @param new_control the control used to zero the state
241 bool EditState( State state, Control new_control );
243 /** automatically switch to trimming longitudinal acceleration with
244 flight path angle (gamma) once it becomes apparent that there
245 is not enough/too much thrust.
246 @param bb true to enable fallback
248 inline void SetGammaFallback(bool bb) { gamma_fallback=bb; }
250 /** query the fallback state
251 @return true if fallback is enabled.
253 inline bool GetGammaFallback(void) { return gamma_fallback; }
255 /** Set the iteration limit. DoTrim() will return false if limit
256 iterations are reached before trim is achieved. The default
257 is 60. This does not ordinarily need to be changed.
258 @param ii integer iteration limit
260 inline void SetMaxCycles(int ii) { max_iterations = ii; }
262 /** Set the per-axis iteration limit. Attempt to zero each state
263 by iterating limit times before moving on to the next. The
264 default limit is 100 and also does not ordinarily need to
266 @param ii integer iteration limit
268 inline void SetMaxCyclesPerAxis(int ii) { max_sub_iterations = ii; }
270 /** Set the tolerance for declaring a state trimmed. Angular accels are
271 held to a tolerance of 1/10th of the given. The default is
272 0.001 for the recti-linear accelerations and 0.0001 for the angular.
274 inline void SetTolerance(double tt) {
276 A_Tolerance = tt / 10;
280 Debug level 1 shows results of each top-level iteration
281 Debug level 2 shows level 1 & results of each per-axis iteration
283 inline void SetDebug(int level) { DebugLevel = level; }
284 inline void ClearDebug(void) { DebugLevel = 0; }
287 Output debug data for one of the axes
288 The State enum is defined in FGTrimAxis.h
290 inline void DebugState(State state) { debug_axis=state; }
292 inline void SetTargetNlf(double nlf) { targetNlf=nlf; }
293 inline double GetTargetNlf(void) { return targetNlf; }