1 /**********************************************************************
3 FILENAME: uiuc_engine.cpp
5 ----------------------------------------------------------------------
7 DESCRIPTION: determine the engine forces and moments
9 ----------------------------------------------------------------------
13 ----------------------------------------------------------------------
15 REFERENCES: simple and c172 models based on portions of
16 c172_engine.c, called from ls_model;
17 cherokee model based on cherokee_engine.c
19 ----------------------------------------------------------------------
21 HISTORY: 01/30/2000 initial release
22 06/18/2001 (RD) Added Throttle_pct_input.
24 ----------------------------------------------------------------------
26 AUTHOR(S): Bipin Sehgal <bsehgal@uiuc.edu>
27 Jeff Scott <jscott@mail.com>
28 Robert Deters <rdeters@uiuc.edu>
29 Michael Selig <m-selig@uiuc.edu>
31 ----------------------------------------------------------------------
35 ----------------------------------------------------------------------
39 ----------------------------------------------------------------------
45 ----------------------------------------------------------------------
47 CALLED BY: uiuc_wrapper.cpp
49 ----------------------------------------------------------------------
53 ----------------------------------------------------------------------
55 COPYRIGHT: (C) 2000 by Michael Selig
57 This program is free software; you can redistribute it and/or
58 modify it under the terms of the GNU General Public License
59 as published by the Free Software Foundation.
61 This program is distributed in the hope that it will be useful,
62 but WITHOUT ANY WARRANTY; without even the implied warranty of
63 MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
64 GNU General Public License for more details.
66 You should have received a copy of the GNU General Public License
67 along with this program; if not, write to the Free Software
68 Foundation, Inc., 59 Temple Place - Suite 330, Boston, MA 02111-1307,
69 USA or view http://www.gnu.org/copyleft/gpl.html.
71 **********************************************************************/
72 #include <simgear/compiler.h>
74 #include "uiuc_engine.h"
76 #if !defined (SG_HAVE_NATIVE_SGI_COMPILERS)
86 if (Throttle_pct_input)
88 double Throttle_pct_input_endTime = Throttle_pct_input_timeArray[Throttle_pct_input_ntime];
89 if (Simtime >= Throttle_pct_input_startTime &&
90 Simtime <= (Throttle_pct_input_startTime + Throttle_pct_input_endTime))
92 double time = Simtime - Throttle_pct_input_startTime;
93 Throttle_pct = uiuc_1Dinterpolation(Throttle_pct_input_timeArray,
94 Throttle_pct_input_dTArray,
95 Throttle_pct_input_ntime,
100 Throttle[3] = Throttle_pct;
102 command_list = engineParts -> getCommands();
105 if (command_list.begin() == command_list.end())
107 cerr << "ERROR: Engine not specified. Aircraft cannot fly without the engine" << endl;
112 for (LIST command_line = command_list.begin(); command_line!=command_list.end(); ++command_line)
114 //cout << *command_line << endl;
116 linetoken1 = engineParts -> getToken(*command_line, 1);
117 linetoken2 = engineParts -> getToken(*command_line, 2);
119 switch(engine_map[linetoken2])
121 case simpleSingle_flag:
123 F_X_engine = Throttle[3] * simpleSingleMaxThrust;
126 case simpleSingleModel_flag:
128 /* simple model based on Hepperle's equation
129 * exponent dtdvvt was computed in uiuc_menu.cpp */
130 F_X_engine = Throttle[3] * t_v0 * (1 - pow((V_rel_wind/v_t0),dtdvvt));
131 if (slipstream_effects) {
132 tc = F_X_engine/(Dynamic_pressure * LS_PI * propDia * propDia / 4);
133 w_induced = 0.5 * V_rel_wind * (-1 + pow((1+tc),.5));
134 eta_q = (2* w_induced + V_rel_wind)*(2* w_induced + V_rel_wind)/(V_rel_wind * V_rel_wind);
135 /* add in a die-off function so that eta falls off w/ alfa and beta */
136 eta_q = Cos_alpha * Cos_alpha * Cos_beta * Cos_beta * eta_q;
137 /* determine the eta_q values for the respective coefficients */
138 if (eta_q_Cm_q_fac) {eta_q_Cm_q *= eta_q * eta_q_Cm_q_fac;}
139 if (eta_q_Cm_adot_fac) {eta_q_Cm_adot *= eta_q * eta_q_Cm_adot_fac;}
140 if (eta_q_Cmfade_fac) {eta_q_Cmfade *= eta_q * eta_q_Cmfade_fac;}
141 if (eta_q_Cl_beta_fac) {eta_q_Cl_beta *= eta_q * eta_q_Cl_beta_fac;}
142 if (eta_q_Cl_p_fac) {eta_q_Cl_p *= eta_q * eta_q_Cl_p_fac;}
143 if (eta_q_Cl_r_fac) {eta_q_Cl_r *= eta_q * eta_q_Cl_r_fac;}
144 if (eta_q_Cl_dr_fac) {eta_q_Cl_dr *= eta_q * eta_q_Cl_dr_fac;}
145 if (eta_q_CY_beta_fac) {eta_q_CY_beta *= eta_q * eta_q_CY_beta_fac;}
146 if (eta_q_CY_p_fac) {eta_q_CY_p *= eta_q * eta_q_CY_p_fac;}
147 if (eta_q_CY_r_fac) {eta_q_CY_r *= eta_q * eta_q_CY_r_fac;}
148 if (eta_q_CY_dr_fac) {eta_q_CY_dr *= eta_q * eta_q_CY_dr_fac;}
149 if (eta_q_Cn_beta_fac) {eta_q_Cn_beta *= eta_q * eta_q_Cn_beta_fac;}
150 if (eta_q_Cn_p_fac) {eta_q_Cn_p *= eta_q * eta_q_Cn_p_fac;}
151 if (eta_q_Cn_r_fac) {eta_q_Cn_r *= eta_q * eta_q_Cn_r_fac;}
152 if (eta_q_Cn_dr_fac) {eta_q_Cn_dr *= eta_q * eta_q_Cn_dr_fac;}
154 /* Need engineOmega for gyroscopic moments */
155 engineOmega = minOmega + Throttle[3] * (maxOmega - minOmega);
160 //c172 engine lines ... looks like 0.83 is just a thrust increase
161 F_X_engine = Throttle[3] * 350 / 0.83;
162 F_Z_engine = Throttle[3] * 4.9 / 0.83;
163 M_m_engine = F_X_engine * 0.734 * cbar;
169 dP = (180.0-117.0)*745.7, // Watts
170 dn = (2700.0-2350.0)/60.0, // d_rpm (I mean d_rps, in seconds)
171 D = 6.17*0.3048, // prop diameter
172 dPh = (58.0-180.0)*745.7, // change of power as function of height
178 J, // advance ratio (ratio of horizontal speed to prop tip speed)
182 eta_engine; // engine efficiency
184 /* assumption -> 0.0 <= Throttle[3] <=1.0 */
185 P = fabs(Throttle[3]) * 180.0 * 745.7; /*180.0*745.7 ->max avail power [W]*/
186 n = dn/dP * (P-117.0*745.7) + 2350.0/60.0;
189 V = (V_rel_wind < 10.0 ? 10.0 : V_rel_wind*0.3048);
192 /* Propeller efficiency */
193 eta_engine = (J < 0.7 ? ((0.8-0.55)/(.7-.3)*(J-0.3) + 0.55) :
194 (J > 0.85 ? ((0.6-0.8)/(1.0-0.85)*(J-0.85) + 0.8) : 0.8));
196 /* power on Altitude */
197 H = Altitude * 0.3048; /* H == Altitude [m] */
198 P *= (dPh/dH * H + 180.0*745.7) / (180.0*745.7);
199 T = eta_engine * P/V; /* Thrust [N] */
201 /*assumption: Engine's line of thrust passes through cg */
202 F_X_engine = T * 0.2248; /* F_X_engine in lb */
209 double Xp_input_endTime = Xp_input_timeArray[Xp_input_ntime];
210 if (Simtime >= Xp_input_startTime &&
211 Simtime <= (Xp_input_startTime + Xp_input_endTime))
213 double time = Simtime - Xp_input_startTime;
214 F_X_engine = uiuc_1Dinterpolation(Xp_input_timeArray,
219 double Zp_input_endTime = Zp_input_timeArray[Zp_input_ntime];
220 if (Simtime >= Zp_input_startTime &&
221 Simtime <= (Zp_input_startTime + Zp_input_endTime))
223 double time = Simtime - Zp_input_startTime;
224 F_Z_engine = uiuc_1Dinterpolation(Zp_input_timeArray,
229 double Mp_input_endTime = Mp_input_timeArray[Mp_input_ntime];
230 if (Simtime >= Mp_input_startTime &&
231 Simtime <= (Mp_input_startTime + Mp_input_endTime))
233 double time = Simtime - Mp_input_startTime;
234 M_m_engine = uiuc_1Dinterpolation(Mp_input_timeArray,
245 // end uiuc_engine.cpp