New features for JSBSim (not to be included in release 2018.3)

The following new features have been added to JSBSim:
* Added the ability to set up the starter and acceleration times of a turbine (parameters <n1spinup>, <n2spinup>, <n1startrate>, <n2startrate>).
* The <integrator> filter can now be reset to 0.0 by setting its <trigger> property to a negative value.
* The integration scheme of the <integrator> filter can now be chosen among "rect" (Euler), "trap" (Trapezoidal), "ab2" 2nd order Adams-BashForth and "ab3" 3rd order Adams-Bashforth
* The following functions can now be used in <function>: floor, ceil and fmod. Their functionalities are the same than the corresponding C/C++ functions.

src/FDM/JSBSim/input_output/FGXMLElement.h

@@ -177,6 +177,7 @@ public:
   /** Retrieves the element name.
       @return the element name, or the empty string if no name has been set.*/
   const std::string& GetName(void) const {return name;}
+  void ChangeName(const std::string& _name) { name = _name; }
 
   /** Gets a line of data belonging to an element.
       @param i the index of the data line to return (0 by default).

src/FDM/JSBSim/math/FGFunction.cpp

@@ -107,6 +107,9 @@ const std::string FGFunction::not_string = "not";
 const std::string FGFunction::ifthen_string = "ifthen";
 const std::string FGFunction::switch_string = "switch";
 const std::string FGFunction::interpolate1d_string = "interpolate1d";
+const std::string FGFunction::floor_string = "floor";
+const std::string FGFunction::ceil_string = "ceil";
+const std::string FGFunction::fmod_string = "fmod";
 
 FGFunction::FGFunction(FGPropertyManager* PropertyManager, Element* el,
                        const string& prefix, FGPropertyValue* var)
@@ -228,6 +231,12 @@ void FGFunction::Load(FGPropertyManager* PropertyManager, Element* el,
     Type = eSwitch;
   } else if (operation == interpolate1d_string) {
     Type = eInterpolate1D;
+  } else if (operation == floor_string) {
+    Type = eFloor;
+  } else if (operation == ceil_string) {
+    Type = eCeil;
+  } else if (operation == fmod_string) {
+    Type = eFmod;
   } else if (operation != description_string) {
     cerr << "Bad operation " << operation << " detected in configuration file" << endl;
   }
@@ -324,7 +333,10 @@ void FGFunction::Load(FGPropertyManager* PropertyManager, Element* el,
                operation == not_string ||
                operation == ifthen_string ||
                operation == switch_string ||
-               operation == interpolate1d_string)
+               operation == interpolate1d_string ||
+               operation == floor_string ||
+               operation == ceil_string ||
+               operation == fmod_string)
       {
         Parameters.push_back(new FGFunction(PropertyManager, element, Prefix, var));
       } else if (operation != description_string) {
@@ -767,6 +779,18 @@ double FGFunction::GetValue(void) const
     else // 
     {temp = 1;}
     break;
+  case eFloor:
+    temp = floor(temp);
+    break;
+  case eCeil:
+    temp = ceil(temp);
+    break;
+  case eFmod:
+    if (Parameters[1]->GetValue() != 0.0)
+      temp = fmod(temp, Parameters[1]->GetValue());
+    else
+      temp = HUGE_VAL;
+    break;
   default:
     cerr << "Unknown function operation type" << endl;
     break;

src/FDM/JSBSim/math/FGFunction.h

@@ -84,6 +84,9 @@ A function definition consists of an operation, a value, a table, or a property
 - avg (takes n args)
 - fraction
 - mod
+- floor (takes 1 arg)
+- ceil (takes 1 arg)
+- fmod (takes 2 args)
 - lt (less than, takes 2 args)
 - le (less equal, takes 2 args)
 - gt (greater than, takes 2 args)
@@ -466,13 +469,36 @@ of the three words refers to one or more instances of a property, value, or tabl
          quotient of 3 and leaves a remainder of 0.
     @code
     <mod>
-      {property, value, table, or other function element} {property, value, table, or other function element}
+      {property, value, table, or other function element}
+      {property, value, table, or other function element}
     </mod>
 
     Example: 5 mod 2, evaluates to 1
 
     <mod> <v> 5 </v> <v> 2 </v> </mod>
     @endcode
+- @b floor returns the largest integral value that is not greater than X.
+    @code
+    <floor>
+      {property, value, table, or other function element}
+    </floor>
+    @endcode
+    Examples: floor(2.3) evaluates to 2.0 while floor(-2.3) evaluates to -3.0
+- @b ceil returns the smallest integral value that is not less than X.
+    @code
+    <ceil>
+      {property, value, table, or other function element}
+    </ceil>
+    @endcode
+    Examples: ceil(2.3) evaluates to 3.0 while ceil(-2.3) evaluates to -2.0
+- @b fmod returns the floating-point remainder of X/Y (rounded towards zero)
+    @code
+    <fmod>
+      {property, value, table, or other function element}
+      {property, value, table, or other function element}
+    </fmod>
+    @endcode
+    Example: fmod(18.5, 4.2) evaluates to 1.7
 - @b lt returns a 1 if the value of the first immediate child element is less
         than the value of the second immediate child element, returns 0
         otherwise
@@ -799,6 +825,9 @@ private:
   static const std::string ifthen_string;
   static const std::string switch_string;
   static const std::string interpolate1d_string;
+  static const std::string floor_string;
+  static const std::string ceil_string;
+  static const std::string fmod_string;
 
   enum functionType {eTopLevel=0, eProduct, eDifference, eSum, eQuotient, ePow, eSqrt, eToRadians,
                      eToDegrees, eExp, eAbs, eSign, eSin, eCos, eTan, eASin, eACos, eATan, eATan2,
@@ -806,7 +835,7 @@ private:
                      eLog2, eLn, eLog10, eLT, eLE, eGE, eGT, eEQ, eNE,  eAND, eOR, eNOT,
                      eIfThen, eSwitch, eInterpolate1D, eRotation_alpha_local,
                      eRotation_beta_local, eRotation_gamma_local, eRotation_bf_to_wf,
-                     eRotation_wf_to_bf} Type;
+                     eRotation_wf_to_bf, eFloor, eCeil, eFmod} Type;
   std::string Prefix;
   bool cached;
   double cachedValue;

src/FDM/JSBSim/models/FGFCS.cpp

@@ -534,8 +534,7 @@ bool FGFCS::Load(Element* document)
         if ((component_element->GetName() == string("lag_filter")) ||
             (component_element->GetName() == string("lead_lag_filter")) ||
             (component_element->GetName() == string("washout_filter")) ||
-            (component_element->GetName() == string("second_order_filter")) ||
+            (component_element->GetName() == string("second_order_filter")) )
-            (component_element->GetName() == string("integrator")) )
         {
           newChannel->Add(new FGFilter(this, component_element));
         } else if ((component_element->GetName() == string("pure_gain")) ||
@@ -555,6 +554,18 @@ bool FGFCS::Load(Element* document)
           newChannel->Add(new FGFCSFunction(this, component_element));
         } else if (component_element->GetName() == string("pid")) {
           newChannel->Add(new FGPID(this, component_element));
+        } else if (component_element->GetName() == string("integrator")) {
+          // <integrator> is equivalent to <pid type="trap">
+          Element* c1_el = component_element->FindElement("c1");
+          if (!c1_el) {
+            cerr << component_element->ReadFrom();
+            throw("INTEGRATOR component " + component_element->GetAttributeValue("name")
+                  + " does not provide the parameter <c1>");
+          }
+          c1_el->ChangeName("ki");
+          if (!c1_el->HasAttribute("type"))
+            c1_el->AddAttribute("type", "trap");
+          newChannel->Add(new FGPID(this, component_element));
         } else if (component_element->GetName() == string("actuator")) {
           newChannel->Add(new FGActuator(this, component_element));
         } else if (component_element->GetName() == string("sensor")) {

src/FDM/JSBSim/models/flight_control/FGFilter.cpp

@@ -68,7 +68,6 @@ FGFilter::FGFilter(FGFCS* fcs, Element* element) : FGFCSComponent(fcs, element)
   else if (Type == "LEAD_LAG_FILTER")     FilterType = eLeadLag    ;
   else if (Type == "SECOND_ORDER_FILTER") FilterType = eOrder2     ;
   else if (Type == "WASHOUT_FILTER")      FilterType = eWashout    ;
-  else if (Type == "INTEGRATOR")          FilterType = eIntegrator ;
   else                                    FilterType = eUnknown    ;
 
   if (element->FindElement("trigger")) {
@@ -170,10 +169,6 @@ void FGFilter::CalculateDynamicFilters(void)
       ca = 2.00 / denom;
       cb = (2.00 - dt*C[1]) / denom;
       break;
-    case eIntegrator:
-      if (PropertyNode[1] != 0L) C[1] = PropertyNode[1]->getDoubleValue()*PropertySign[1];
-      ca = dt*C[1] / 2.00;
-      break;
     case eUnknown:
       cerr << "Unknown filter type" << endl;
     break;
@@ -210,15 +205,6 @@ bool FGFilter::Run(void)
       case eWashout:
         Output = Input * ca - PreviousInput1 * ca + PreviousOutput1 * cb;
         break;
-      case eIntegrator:
-        if (Trigger != 0) {
-          double test = Trigger->getDoubleValue();
-          if (fabs(test) > 0.000001) {
-            Input  = PreviousInput1 = PreviousInput2 = 0.0;
-          }
-        }
-        Output = Input * ca + PreviousInput1 * ca + PreviousOutput1;
-        break;
       case eUnknown:
         break;
     }
@@ -321,12 +307,6 @@ void FGFilter::Debug(int from)
           if (PropertyNode[1] == 0L) cout << "      C[1]: " << C[1] << endl;
           else cout << "      C[1] is the value of property: " << sgn << PropertyNode[1]->GetName() << endl;
           break;
-        case eIntegrator:
-          if (PropertySign[1] < 0.0) sgn="-";
-          else sgn = "";
-          if (PropertyNode[1] == 0L) cout << "      C[1]: " << C[1] << endl;
-          else cout << "      C[1] is the value of property: " << sgn << PropertyNode[1]->GetName() << endl;
-          break;
         case eUnknown:
           break;
        } 

src/FDM/JSBSim/models/flight_control/FGFilter.h

@@ -199,15 +199,15 @@ For an integrator of the form:
 The corresponding filter definition is:
 
 @code
-<integrator name="name">
+<integrator name="{string}">
-  <input> property </input>
+  <input> {property} </input>
-  <c1> value|property </c1>
+  <c1 type="rect|trap|ab2|ab3"> {[-]property | number} </c1>
-  [<trigger> property </trigger>]
+  [<trigger> {property} </trigger>]
   [<clipto>
-    <min> {[-]property name | value} </min>
+    <min> {[-]property | number} </min>
-    <max> {[-]property name | value} </max>
+    <max> {[-]property | number} </max>
   </clipto>]
-  [<output> property </output>]
+  [<output> {property} </output>]
 </integrator>
 @endcode
 
@@ -217,12 +217,32 @@ property value is:
   - not 0: (or simply greater than zero), all current and previous inputs will
            be set to 0.0
 
+By default, the integration scheme is the trapezoidal scheme.
+
+An integrator is equivalent to a PID with the following parameters:
+@code
+<pid name="{string}">
+  <input> {[-]property} </input>
+  <kp> 0.0 </kp>
+  <ki type="rect|trap|ab2|ab3"> {number|[-]property} </ki>
+  <kd> 0.0 </kd>
+  <trigger> {property} </trigger>
+  [<clipto>
+  <min> {[-]property | value} </min>
+  <max> {[-]property | value} </max>
+  </clipto>]
+  [<output> {property} </output>]
+</pid>
+@endcode
+
+As a consequence, JSBSim internally uses PID controllers to simulate INTEGRATOR
+filters.
+
 In all the filter specifications above, an \<output> element is also seen.  This
-is so that the last component in a "string" can copy its value to the appropriate
+is so that the last component in a "string" can copy its value to the
-output, such as the elevator, or speedbrake, etc.
+appropriate output, such as the elevator, or speedbrake, etc.
 
 @author Jon S. Berndt
-@version $Revision: 1.14 $
 
 */
 
@@ -243,7 +263,7 @@ public:
   bool Initialize;
   void ResetPastStates(void);
   
-  enum {eLag, eLeadLag, eOrder2, eWashout, eIntegrator, eUnknown} FilterType;
+  enum {eLag, eLeadLag, eOrder2, eWashout, eUnknown} FilterType;
 
 private:
   double ca;

src/FDM/JSBSim/models/propulsion/FGTurbine.cpp

@@ -70,7 +70,7 @@ FGTurbine::FGTurbine(FGFDMExec* exec, Element *el, int engine_number, struct Inp
   Augmented = AugMethod = Injected = 0;
   BypassRatio = BleedDemand = 0.0;
   IdleThrustLookup = MilThrustLookup = MaxThrustLookup = InjectionLookup = 0;
-  N1_spinup = 1.0; N2_spinup = 3.0;
+  N1_spinup = 1.0; N2_spinup = 3.0; IgnitionN1 = 5.21; IgnitionN2 = 25.18; N1_start_rate = 1.4; N2_start_rate = 2.0; 
   InjectionTime = 30.0;
   InjectionTimer = InjWaterNorm = 0.0;
   EPR = 1.0;
@@ -281,8 +281,8 @@ double FGTurbine::SpinUp(void)
 {
   Running = false;
   FuelFlow_pph = 0.0;
-  N2 = Seek(&N2, 25.18, N2_spinup, N2/2.0);
+  N2 = Seek(&N2, IgnitionN2, N2_spinup, N2/2.0);
-  N1 = Seek(&N1, 5.21, N1_spinup, N1/2.0);
+  N1 = Seek(&N1, IgnitionN1, N1_spinup, N1/2.0);
   EGT_degC = Seek(&EGT_degC, in.TAT_c, 11.7, 7.3);
   OilPressure_psi = N2 * 0.62;
   OilTemp_degK = Seek(&OilTemp_degK, in.TAT_c + 273.0, 0.2, 0.2);
@@ -299,8 +299,8 @@ double FGTurbine::Start(void)
   if ((N2 > 15.0) && !Starved) {       // minimum 15% N2 needed for start
     Cranking = true;                   // provided for sound effects signal
     if (N2 < IdleN2) {
-      N2 = Seek(&N2, IdleN2, 2.0, N2/2.0);
+      N2 = Seek(&N2, IdleN2, N2_start_rate, N2/2.0);
-      N1 = Seek(&N1, IdleN1, 1.4, N1/2.0);
+      N1 = Seek(&N1, IdleN1, N1_start_rate, N1/2.0);
       EGT_degC = Seek(&EGT_degC, in.TAT_c + 363.1, 21.3, 7.3);
       FuelFlow_pph = IdleFF * N2 / IdleN2;
       OilPressure_psi = N2 * 0.62;
@@ -448,6 +448,10 @@ bool FGTurbine::Load(FGFDMExec* exec, Element *el)
     TSFC = el->FindElementValueAsNumber("tsfc");
   if (el->FindElement("atsfc"))
     ATSFC = el->FindElementValueAsNumber("atsfc");
+  if (el->FindElement("ignitionn1"))
+    IgnitionN1 = el->FindElementValueAsNumber("ignitionn1");
+  if (el->FindElement("ignitionn2"))
+    IgnitionN1 = el->FindElementValueAsNumber("ignitionn2");
   if (el->FindElement("idlen1"))
     IdleN1 = el->FindElementValueAsNumber("idlen1");
   if (el->FindElement("idlen2"))
@@ -460,6 +464,10 @@ bool FGTurbine::Load(FGFDMExec* exec, Element *el)
     N1_spinup = el->FindElementValueAsNumber("n1spinup");
   if (el->FindElement("n2spinup"))
     N2_spinup = el->FindElementValueAsNumber("n2spinup");
+  if (el->FindElement("n1startrate"))
+    N1_start_rate = el->FindElementValueAsNumber("n1startrate");
+  if (el->FindElement("n2startrate"))
+    N2_start_rate = el->FindElementValueAsNumber("n2startrate");
   if (el->FindElement("augmented"))
     Augmented = (int)el->FindElementValueAsNumber("augmented");
   if (el->FindElement("augmethod"))

src/FDM/JSBSim/models/propulsion/FGTurbine.h

@@ -66,8 +66,8 @@ CLASS DOCUMENTATION
 <P>
     - STARTING (on ground):
       -# Set the control FGEngine::Starter to true.  The engine will spin up to
-         a maximum of about %25 N2 (%5.2 N1).  This simulates the action of a
+         a maximum of about %25 N2 (%5.2 N1). This value may be changed using the <startnX> parameter.
-         pneumatic starter.
+		 This simulates the action of a pneumatic starter.
       -# After reaching %15 N2 set the control FGEngine::Cutoff to false. If fuel
          is available the engine will now accelerate to idle.  The starter will
          automatically be set to false after the start cycle.
@@ -78,7 +78,7 @@ CLASS DOCUMENTATION
       -# Place the control FGEngine::Cutoff to false.
 <P>
     Ignition is assumed to be on anytime the Cutoff control is set to false,
-    therefore a seperate ignition system is not modeled.
+    therefore a separate ignition system is not modeled.
 
 <h3>Configuration File Format:</h3>
 @code
@@ -89,10 +89,14 @@ CLASS DOCUMENTATION
   <bleed> {number} </bleed>
   <tsfc> {number} </tsfc>
   <atsfc> {number} </atsfc>
+  <ignitionn1> {number} </ignitionn1>
+  <ignitionn2> {number} </ignitionn2>
   <idlen1> {number} </idlen1>
   <idlen2> {number} </idlen2>
   <n1spinup> {number} </n1spinup>
   <n2spinup> {number} </n2spinup>
+  <n1startrate> {number} </n1startrate>
+  <n2startrate> {number} </n2startrate>
   <maxn1> {number} </maxn1>
   <maxn2> {number} </maxn2>
   <augmented> {0 | 1} </augmented>
@@ -111,10 +115,14 @@ CLASS DOCUMENTATION
   bleed       - Thrust reduction factor due to losses (0.0 to 1.0).
   tsfc        - Thrust-specific fuel consumption at cruise, lbm/hr/lbf
   atsfc       - Afterburning TSFC, lbm/hr/lbf
+  ignitionn1  - Fan rotor rpm (% of max) while starting
+  ignitionn2  - Core rotor rpm (% of max) while starting
   idlen1      - Fan rotor rpm (% of max) at idle
   idlen2      - Core rotor rpm (% of max) at idle
-  n1spinup    - Fan rotor rpm starter acceleration (default 1.0)
+  n1spinup    - Fan rotor rpm starter acceleration to ignitionn1 value (default 1.0)
-  n2spinup    - Core rotor rpm starter acceleration (default 3.0)
+  n2spinup    - Core rotor rpm starter acceleration to ignitionn2 value (default 3.0)
+  n1startrate - Fan rotor rpm time taken to accelerate from ignitionn1 to idlen1 value (default 1.4)
+  n2startrate - Core rotor rpm time taken to accelerate to ignitionn2 idlen2 value (default 2.0)
   maxn1       - Fan rotor rpm (% of max) at full throttle 
   maxn2       - Core rotor rpm (% of max) at full throttle
   augmented
@@ -238,6 +246,8 @@ private:
   double ATSFC;            ///< Augmented TSFC (lbm/hr/lbf)
   double IdleN1;           ///< Idle N1
   double IdleN2;           ///< Idle N2
+  double IgnitionN1;       ///< Ignition N1
+  double IgnitionN2;       ///< Ignition N2
   double N1;               ///< N1
   double N2;               ///< N2
   double N2norm;           ///< N2 normalized (0=idle, 1=max)
@@ -248,8 +258,10 @@ private:
   double N2_factor;        ///< factor to tie N2 and throttle
   double ThrottlePos;      ///< FCS-supplied throttle position - modified for local use!
   double AugmentCmd;       ///< modulated afterburner command (0.0 to 1.0)
-  double N1_spinup;        ///< N1 spin up rate from starter (per second)
+  double N1_spinup;        ///< N1 spin up rate from pneumatic starter (per second)
-  double N2_spinup;        ///< N2 spin up rate from starter (per second)
+  double N2_spinup;        ///< N2 spin up rate from pneumatic starter (per second)
+  double N1_start_rate;    ///< N1 spin up rate from ignition (per second)
+  double N2_start_rate;    ///< N2 spin up rate from ignition (per second)
   bool Stalled;            ///< true if engine is compressor-stalled
   bool Seized;             ///< true if inner spool is seized
   bool Overtemp;           ///< true if EGT exceeds limits