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 /*%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
67 %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%*/
71 typedef enum { tLongitudinal=0, tFull, tGround, tPullup,
72 tCustom, tTurn, tNone } TrimMode;
74 /*%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
76 %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%*/
78 /** The trimming routine for JSBSim.
79 FGTrim finds the aircraft attitude and control settings needed to maintain
80 the steady state described by the FGInitialCondition object . It does this
81 iteratively by assigning a control to each state and adjusting that control
82 until the state is within a specified tolerance of zero. States include the
83 recti-linear accelerations udot, vdot, and wdot, the angular accelerations
84 qdot, pdot, and rdot, and the difference between heading and ground track.
85 Controls include the usual flight deck controls available to the pilot plus
86 angle of attack (alpha), sideslip angle(beta), flight path angle (gamma),
87 pitch attitude(theta), roll attitude(phi), and altitude above ground. The
88 last three are used for on-ground trimming. The state-control pairs used in
89 a given trim are completely user configurable and several pre-defined modes
90 are provided as well. They are:
91 - tLongitudinal: Trim wdot with alpha, udot with thrust, qdot with elevator
92 - tFull: tLongitudinal + vdot with phi, pdot with aileron, rdot with rudder
93 and heading minus ground track (hmgt) with beta
94 - tPullup: tLongitudinal but adjust alpha to achieve load factor input
96 - tGround: wdot with altitude, qdot with theta, and pdot with phi
98 The remaining modes include <b>tCustom</b>, which is completely user defined and
101 Note that trims can (and do) fail for reasons that are completely outside
102 the control of the trimming routine itself. The most common problem is the
103 initial conditions: is the model capable of steady state flight
104 at those conditions? Check the speed, altitude, configuration (flaps,
105 gear, etc.), weight, cg, and anything else that may be relevant.
109 FGFDMExec* FDMExec = new FGFDMExec();
111 FGInitialCondition* fgic = new FGInitialCondition(FDMExec);
112 FGTrim fgt(FDMExec, fgic, tFull);
113 fgic->SetVcaibratedKtsIC(100);
114 fgic->SetAltitudeFtIC(1000);
115 fgic->SetClimbRate(500);
116 if( !fgt.DoTrim() ) {
117 cout << "Trim Failed" << endl;
126 /*%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
128 %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%*/
130 class FGTrim : public FGJSBBase
134 vector<FGTrimAxis*> TrimAxes;
135 unsigned int current_axis;
138 int DebugLevel, Debug;
139 double Tolerance, A_Tolerance;
140 double wdot,udot,qdot;
142 double *sub_iterations;
145 int max_sub_iterations;
151 unsigned int axis_count;
153 double xlo,xhi,alo,ahi;
157 double psidot,thetadot;
160 FGInitialCondition* fgic;
164 /** @return false if there is no change in the current axis accel
165 between accel(control_min) and accel(control_max). If there is a
166 change, sets solutionDomain to:
167 0 for no sign change,
168 -1 if sign change between accel(control_min) and accel(0)
169 1 if sign between accel(0) and accel(control_max)
171 bool findInterval(void);
173 bool checkLimits(void);
175 void setupPullup(void);
176 void setupTurn(void);
178 void updateRates(void);
183 /** Initializes the trimming class
184 @param FDMExec pointer to a JSBSim executive object.
187 FGTrim(FGFDMExec *FDMExec, TrimMode tm=tGround );
195 /** Print the results of the trim. For each axis trimmed, this
196 includes the final state value, control value, and tolerance
198 @return true if trim succeeds
202 /** Iteration statistics
206 /** Clear all state-control pairs and set a predefined trim mode
207 @param tm the set of axes to trim. Can be:
208 tLongitudinal, tFull, tGround, tCustom, or tNone
210 void SetMode(TrimMode tm);
212 /** Clear all state-control pairs from the current configuration.
213 The trimming routine must have at least one state-control pair
214 configured to be useful
216 void ClearStates(void);
218 /** Add a state-control pair to the current configuration. See the enums
219 State and Control in FGTrimAxis.h for the available options.
220 Will fail if the given state is already configured.
221 @param state the accel or other condition to zero
222 @param control the control used to zero the state
223 @return true if add is successful
225 bool AddState( State state, Control control );
227 /** Remove a specific state-control pair from the current configuration
228 @param state the state to remove
229 @return true if removal is successful
231 bool RemoveState( State state );
233 /** Change the control used to zero a state previously configured
234 @param state the accel or other condition to zero
235 @param new_control the control used to zero the state
237 bool EditState( State state, Control new_control );
239 /** automatically switch to trimming longitudinal acceleration with
240 flight path angle (gamma) once it becomes apparent that there
241 is not enough/too much thrust.
242 @param bb true to enable fallback
244 inline void SetGammaFallback(bool bb) { gamma_fallback=bb; }
246 /** query the fallback state
247 @return true if fallback is enabled.
249 inline bool GetGammaFallback(void) { return gamma_fallback; }
251 /** Set the iteration limit. DoTrim() will return false if limit
252 iterations are reached before trim is achieved. The default
253 is 60. This does not ordinarily need to be changed.
254 @param ii integer iteration limit
256 inline void SetMaxCycles(int ii) { max_iterations = ii; }
258 /** Set the per-axis iteration limit. Attempt to zero each state
259 by iterating limit times before moving on to the next. The
260 default limit is 100 and also does not ordinarily need to
262 @param ii integer iteration limit
264 inline void SetMaxCyclesPerAxis(int ii) { max_sub_iterations = ii; }
266 /** Set the tolerance for declaring a state trimmed. Angular accels are
267 held to a tolerance of 1/10th of the given. The default is
268 0.001 for the recti-linear accelerations and 0.0001 for the angular.
270 inline void SetTolerance(double tt) {
272 A_Tolerance = tt / 10;
276 Debug level 1 shows results of each top-level iteration
277 Debug level 2 shows level 1 & results of each per-axis iteration
279 inline void SetDebug(int level) { DebugLevel = level; }
280 inline void ClearDebug(void) { DebugLevel = 0; }
283 Output debug data for one of the axes
284 The State enum is defined in FGTrimAxis.h
286 inline void DebugState(State state) { debug_axis=state; }
288 inline void SetTargetNlf(double nlf) { targetNlf=nlf; }
289 inline double GetTargetNlf(void) { return targetNlf; }