src/FDM/UIUCModel/uiuc_engine.cpp

   1 /**********************************************************************
   2
   3  FILENAME:     uiuc_engine.cpp
   4
   5 ----------------------------------------------------------------------
   6
   7  DESCRIPTION:  determine the engine forces and moments
   8
   9 ----------------------------------------------------------------------
  10
  11  STATUS:       alpha version
  12
  13 ----------------------------------------------------------------------
  14
  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
  18
  19 ----------------------------------------------------------------------
  20
  21  HISTORY:      01/30/2000   initial release
  22                06/18/2001   (RD) Added Throttle_pct_input.
  23
  24 ----------------------------------------------------------------------
  25
  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>
  30
  31 ----------------------------------------------------------------------
  32
  33  VARIABLES:
  34
  35 ----------------------------------------------------------------------
  36
  37  INPUTS:       -engine model
  38
  39 ----------------------------------------------------------------------
  40
  41  OUTPUTS:      -F_X_engine
  42                -F_Z_engine
  43                -M_m_engine
  44
  45 ----------------------------------------------------------------------
  46
  47  CALLED BY:   uiuc_wrapper.cpp
  48
  49 ----------------------------------------------------------------------
  50
  51  CALLS TO:     none
  52
  53 ----------------------------------------------------------------------
  54
  55  COPYRIGHT:    (C) 2000 by Michael Selig
  56
  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.
  60
  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.
  65
  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.
  70
  71 **********************************************************************/
  72 #include <simgear/compiler.h>
  73
  74 #include "uiuc_engine.h"
  75
  76 #if !defined (SG_HAVE_NATIVE_SGI_COMPILERS)
  77 SG_USING_STD(cerr);
  78 #endif
  79
  80 void uiuc_engine()
  81 {
  82   stack command_list;
  83   string linetoken1;
  84   string linetoken2;
  85
  86   if (Throttle_pct_input)
  87     {
  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))
  91         {
  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,
  96                          time);
  97         }
  98     }
  99
 100   Throttle[3] = Throttle_pct;
 101
 102   command_list = engineParts -> getCommands();
 103
 104   /*
 105   if (command_list.begin() == command_list.end())
 106   {
 107         cerr << "ERROR: Engine not specified. Aircraft cannot fly without the engine" << endl;
 108         exit(-1);
 109   }
 110   */
 111
 112   for (LIST command_line = command_list.begin(); command_line!=command_list.end(); ++command_line)
 113     {
 114       //cout << *command_line << endl;
 115
 116       linetoken1 = engineParts -> getToken(*command_line, 1);
 117       linetoken2 = engineParts -> getToken(*command_line, 2);
 118
 119       switch(engine_map[linetoken2])
 120         {
 121         case simpleSingle_flag:
 122           {
 123             F_X_engine = Throttle[3] * simpleSingleMaxThrust;
 124             break;
 125           }
 126         case c172_flag:
 127           {
 128             //c172 engine lines ... looks like 0.83 is just a thrust increase
 129             F_X_engine = Throttle[3] * 350 / 0.83;
 130             F_Z_engine = Throttle[3] * 4.9 / 0.83;
 131             M_m_engine = F_X_engine * 0.734 * cbar;
 132             break;
 133           }
 134         case cherokee_flag:
 135           {
 136             static float
 137               dP = (180.0-117.0)*745.7,   // Watts
 138               dn = (2700.0-2350.0)/60.0,  // d_rpm (I mean d_rps, in seconds)
 139               D  = 6.17*0.3048,           // prop diameter
 140               dPh = (58.0-180.0)*745.7,   // change of power as function of height
 141               dH = 25000.0*0.3048;
 142
 143             float
 144               n,   // [rps]
 145               H,   // altitude [m]
 146               J,   // advance ratio (ratio of horizontal speed to prop tip speed)
 147               T,   // thrust [N]
 148               V,   // velocity [m/s]
 149               P,   // power [W]
 150               eta_engine; // engine efficiency
 151
 152             /* assumption -> 0.0 <= Throttle[3] <=1.0 */
 153             P = fabs(Throttle[3]) * 180.0 * 745.7; /*180.0*745.7 ->max avail power [W]*/
 154             n = dn/dP * (P-117.0*745.7) + 2350.0/60.0;
 155
 156             /*  V  [m/s]   */
 157             V = (V_rel_wind < 10.0 ? 10.0 : V_rel_wind*0.3048);
 158             J = V / n / D;
 159
 160             /* Propeller efficiency */
 161             eta_engine = (J < 0.7 ? ((0.8-0.55)/(.7-.3)*(J-0.3) + 0.55) :
 162                           (J > 0.85 ? ((0.6-0.8)/(1.0-0.85)*(J-0.85) + 0.8) : 0.8));
 163
 164             /* power on Altitude */
 165             H = Altitude * 0.3048;       /* H == Altitude [m] */
 166             P *= (dPh/dH * H + 180.0*745.7) / (180.0*745.7);
 167             T = eta_engine * P/V;        /* Thrust [N] */
 168
 169             /*assumption: Engine's line of thrust passes through cg */
 170             F_X_engine = T * 0.2248;     /* F_X_engine in lb */
 171             F_Y_engine = 0.0;
 172             F_Z_engine = 0.0;
 173             break;
 174           }
 175         case forcemom_flag:
 176           {
 177             double Xp_input_endTime = Xp_input_timeArray[Xp_input_ntime];
 178             if (Simtime >= Xp_input_startTime &&
 179                 Simtime <= (Xp_input_startTime + Xp_input_endTime))
 180               {
 181                 double time = Simtime - Xp_input_startTime;
 182                 F_X_engine = uiuc_1Dinterpolation(Xp_input_timeArray,
 183                                                   Xp_input_XpArray,
 184                                                   Xp_input_ntime,
 185                                                   time);
 186               }
 187             double Zp_input_endTime = Zp_input_timeArray[Zp_input_ntime];
 188             if (Simtime >= Zp_input_startTime &&
 189                 Simtime <= (Zp_input_startTime + Zp_input_endTime))
 190               {
 191                 double time = Simtime - Zp_input_startTime;
 192                 F_Z_engine = uiuc_1Dinterpolation(Zp_input_timeArray,
 193                                                   Zp_input_ZpArray,
 194                                                   Zp_input_ntime,
 195                                                   time);
 196               }
 197             double Mp_input_endTime = Mp_input_timeArray[Mp_input_ntime];
 198             if (Simtime >= Mp_input_startTime &&
 199                 Simtime <= (Mp_input_startTime + Mp_input_endTime))
 200               {
 201                 double time = Simtime - Mp_input_startTime;
 202                 M_m_engine = uiuc_1Dinterpolation(Mp_input_timeArray,
 203                                                   Mp_input_MpArray,
 204                                                   Mp_input_ntime,
 205                                                   time);
 206               }
 207           }
 208         };
 209     }
 210   return;
 211 }
 212
 213 // end uiuc_engine.cpp