Updated to match changes in radiostack.[ch]xx

[flightgear.git] / src / FDM / UIUCModel / uiuc_engine.cpp

diff --git a/src/FDM/UIUCModel/uiuc_engine.cpp b/src/FDM/UIUCModel/uiuc_engine.cpp
index 5e0a52047cd21b0bad14531572b34009339e550a..b8a8e855d4c51bd2bfc669abac8fb63382cc7f6c 100644 (file)
--- a/src/FDM/UIUCModel/uiuc_engine.cpp
+++ b/src/FDM/UIUCModel/uiuc_engine.cpp
@@ -12,16 +12,20 @@
 
 ----------------------------------------------------------------------
 
- REFERENCES:   based on portions of c172_engine.c, called from ls_model
+ REFERENCES:   simple and c172 models based on portions of 
+               c172_engine.c, called from ls_model;
+               cherokee model based on cherokee_engine.c
 
 ----------------------------------------------------------------------
 
  HISTORY:      01/30/2000   initial release
+               06/18/2001   (RD) Added Throttle_pct_input.
 
 ----------------------------------------------------------------------
 
  AUTHOR(S):    Bipin Sehgal       <bsehgal@uiuc.edu>
                Jeff Scott         <jscott@mail.com>
+              Robert Deters      <rdeters@uiuc.edu>
                Michael Selig      <m-selig@uiuc.edu>
 
 ----------------------------------------------------------------------
@@ -65,57 +69,112 @@
  USA or view http://www.gnu.org/copyleft/gpl.html.
 
 **********************************************************************/
+#include <simgear/compiler.h>
 
 #include "uiuc_engine.h"
 
+#if !defined (SG_HAVE_NATIVE_SGI_COMPILERS)
+SG_USING_STD(cerr);
+#endif
+
 void uiuc_engine() 
 {
   stack command_list;
   string linetoken1;
   string linetoken2;
+
+  if (Throttle_pct_input)
+    {
+      double Throttle_pct_input_endTime = Throttle_pct_input_timeArray[Throttle_pct_input_ntime];
+      if (Simtime >= Throttle_pct_input_startTime && 
+          Simtime <= (Throttle_pct_input_startTime + Throttle_pct_input_endTime))
+        {
+          double time = Simtime - Throttle_pct_input_startTime;
+          Throttle_pct = uiuc_1Dinterpolation(Throttle_pct_input_timeArray,
+                         Throttle_pct_input_dTArray,
+                         Throttle_pct_input_ntime,
+                         time);
+        }
+    }
   
-  /* [] mss questions: why do this here ... and then undo it later? 
-     ... does Throttle[3] get modified? */
   Throttle[3] = Throttle_pct;
 
   command_list = engineParts -> getCommands();
-  
+
+  /*
   if (command_list.begin() == command_list.end())
   {
         cerr << "ERROR: Engine not specified. Aircraft cannot fly without the engine" << endl;
         exit(-1);
   }
+  */
  
   for (LIST command_line = command_list.begin(); command_line!=command_list.end(); ++command_line)
     {
       //cout << *command_line << endl;
       
-      linetoken1 = engineParts -> getToken(*command_line, 1); // function parameters gettoken(string,tokenNo);
-      linetoken2 = engineParts -> getToken(*command_line, 2); // 2 represents token No 2
+      linetoken1 = engineParts -> getToken(*command_line, 1);
+      linetoken2 = engineParts -> getToken(*command_line, 2);
       
       switch(engine_map[linetoken2])
-            {
-          case simpleSingle_flag:
-            {
-              //c172 engine lines ... looks like 0.83 is just a thrust reduction
-              /* F_X_engine = Throttle[3]*350/0.83; */
-              /* F_Z_engine = Throttle[3]*4.9/0.83; */
-              /* M_m_engine = F_X_engine*0.734*cbar; */
-              F_X_engine = Throttle[3]*simpleSingleMaxThrust;
-              break;
-            }
-            case c172_flag:
-              {
-                F_X_engine = Throttle[3]*350/0.83;
-                F_Z_engine = Throttle[3]*4.9/0.83;
-                M_m_engine = F_X_engine*0.734*cbar;
-                break;
-              }
-            };
-      
-      Throttle_pct = Throttle[3];
-      return;
+        {
+        case simpleSingle_flag:
+          {
+            F_X_engine = Throttle[3] * simpleSingleMaxThrust;
+            break;
+          }
+        case c172_flag:
+          {
+            //c172 engine lines ... looks like 0.83 is just a thrust increase
+            F_X_engine = Throttle[3] * 350 / 0.83;
+            F_Z_engine = Throttle[3] * 4.9 / 0.83;
+            M_m_engine = F_X_engine * 0.734 * cbar;
+            break;
+          }
+        case cherokee_flag:
+          {
+            static float
+              dP = (180.0-117.0)*745.7,   // Watts
+              dn = (2700.0-2350.0)/60.0,  // d_rpm (I mean d_rps, in seconds)
+              D  = 6.17*0.3048,           // prop diameter
+              dPh = (58.0-180.0)*745.7,   // change of power as function of height
+              dH = 25000.0*0.3048;
+
+            float
+              n,   // [rps]
+              H,   // altitude [m]
+              J,   // advance ratio (ratio of horizontal speed to prop tip speed)
+              T,   // thrust [N]
+              V,   // velocity [m/s]
+              P,   // power [W]
+              eta_engine; // engine efficiency
+
+            /* assumption -> 0.0 <= Throttle[3] <=1.0 */
+            P = fabs(Throttle[3]) * 180.0 * 745.7; /*180.0*745.7 ->max avail power [W]*/
+            n = dn/dP * (P-117.0*745.7) + 2350.0/60.0;
+
+            /*  V  [m/s]   */
+            V = (V_rel_wind < 10.0 ? 10.0 : V_rel_wind*0.3048);
+            J = V / n / D;
+
+            /* Propeller efficiency */
+            eta_engine = (J < 0.7 ? ((0.8-0.55)/(.7-.3)*(J-0.3) + 0.55) : 
+                          (J > 0.85 ? ((0.6-0.8)/(1.0-0.85)*(J-0.85) + 0.8) : 0.8));
+
+            /* power on Altitude */
+            H = Altitude * 0.3048;       /* H == Altitude [m] */
+            P *= (dPh/dH * H + 180.0*745.7) / (180.0*745.7);
+            T = eta_engine * P/V;        /* Thrust [N] */ 
+
+            /*assumption: Engine's line of thrust passes through cg */
+            F_X_engine = T * 0.2248;     /* F_X_engine in lb */
+            F_Y_engine = 0.0;
+            F_Z_engine = 0.0;
+            break;
+          }
+        };
     }
+  return;
 }
 
 // end uiuc_engine.cpp