The included model DamperBug1 leads to the following error:

Unbekannter Fehler warning | division by zero in partial equation: ((-$ZERO.$DER.springdamper3.flange_b.phi) * idealrollingwheel2.radius) / (idealrollingwheel2.radius - idealrollingwheel1.radius) because idealrollingwheel2.radius - idealrollingwheel1.radius == 0: File: /usr/lib/omlibrary/Modelica 3.1/Mechanics/Rotational.mo Line: 3644

        | at Time=0.000000

        | [line] 487 | [file] DamperBug1.c

throw   | [line] 45 | [file] util/division.c

        | division by zero

Changing one of the SpringDamper blocks to a Spring works (example DamperBug3).
Deleting the Wheels and staying in the rotational domain works (example DamperBug2).

    Greetings
        Peter

model DamperBug1
  Modelica.Mechanics.Rotational.Sources.ConstantTorque constanttorque1(tau_constant = 100);
  Modelica.Mechanics.Rotational.Components.Inertia inertia1(J = 0.6, w(start = 83.7758, fixed = true), phi(start = 0.0, fixed = true));
  Modelica.Mechanics.Rotational.Components.SpringDamper springdamper3(c = 7500, d = 1);
  Modelica.Mechanics.Rotational.Components.SpringDamper springdamper1(c = 7500, d = 1);
  Modelica.Mechanics.Rotational.Components.IdealRollingWheel idealrollingwheel1(radius = 0.3);
  Modelica.Mechanics.Rotational.Components.IdealRollingWheel idealrollingwheel2(radius = 0.3);
  Modelica.Mechanics.Translational.Components.Mass mass1(m = 1200, v(start = 0, fixed = true));
equation
  connect(idealrollingwheel2.flangeT,mass1.flange_a);
  connect(idealrollingwheel1.flangeT,mass1.flange_a);
  connect(springdamper1.flange_b,idealrollingwheel1.flangeR);
  connect(springdamper3.flange_b,idealrollingwheel2.flangeR);
  connect(springdamper3.flange_a,inertia1.flange_b);
  connect(inertia1.flange_b,springdamper1.flange_a);
  connect(constanttorque1.flange,inertia1.flange_a);
end DamperBug1;

model DamperBug2
  Modelica.Mechanics.Rotational.Sources.ConstantTorque constanttorque1(tau_constant = 100);
  Modelica.Mechanics.Rotational.Components.Inertia inertia1(J = 0.6, w(start = 83.7758, fixed = true), phi(start = 0.0, fixed = true));
  Modelica.Mechanics.Rotational.Components.SpringDamper springdamper3(c = 7500, d = 1);
  Modelica.Mechanics.Rotational.Components.SpringDamper springdamper1(c = 7500, d = 1);
  Modelica.Mechanics.Rotational.Components.Inertia inertia2(J = 2, w(start = 0, fixed = true));
equation
  connect(springdamper3.flange_b,inertia2.flange_a);
  connect(springdamper1.flange_b,inertia2.flange_a);
  connect(springdamper3.flange_a,inertia1.flange_b);
  connect(inertia1.flange_b,springdamper1.flange_a);
  connect(constanttorque1.flange,inertia1.flange_a);
end DamperBug2;

model DamperBug3
  Modelica.Mechanics.Rotational.Sources.ConstantTorque constanttorque1(tau_constant = 100);
  Modelica.Mechanics.Rotational.Components.Inertia inertia1(J = 0.6, w(start = 83.7758, fixed = true), phi(start = 0.0, fixed = true));
  Modelica.Mechanics.Rotational.Components.SpringDamper springdamper3(c = 7500, d = 1);
  Modelica.Mechanics.Rotational.Components.IdealRollingWheel idealrollingwheel1(radius = 0.3);
  Modelica.Mechanics.Rotational.Components.IdealRollingWheel idealrollingwheel2(radius = 0.3);
  Modelica.Mechanics.Translational.Components.Mass mass1(m = 1200, v(start = 0, fixed = true));
  Modelica.Mechanics.Rotational.Components.Spring spring1(c = 7500);
equation
  connect(spring1.flange_b,idealrollingwheel1.flangeR);
  connect(spring1.flange_a,inertia1.flange_b);
  connect(idealrollingwheel2.flangeT,mass1.flange_a);
  connect(idealrollingwheel1.flangeT,mass1.flange_a);
  connect(springdamper3.flange_b,idealrollingwheel2.flangeR);
  connect(springdamper3.flange_a,inertia1.flange_b);
  connect(constanttorque1.flange,inertia1.flange_a);
end DamperBug3;

You can buy a commercial simulation program, throw bug reports in a black hole, pay for yearly updates and hope that some of  your bugs have been fixed in a year or so (and I could name a few examples!).

Or you can use OpenModelica!

Thanks for your fast help
   Peter

Hi,

I've come across this error too and it is most disturbing. I've tried several workarounds without success.
So if I can do anything to push it up the developers' todo list, let me know!

   Regards
      Peter

The attached model is a small part of a SystemDynamics package. Check and instantiation work, but compiling leads to the error:

Translation    17:34:26        0:0-0:0    Error building simulator. Buildlog: gcc   -falign-functions -march=native -mfpmath=sse -fPIC   -I"/usr/include/omc" -I. -L"/home/peter/tmp/raus"   -c -o TestConveyor.o TestConveyor.c
TestConveyor.c: In Funktion »eqFunction_5«:
TestConveyor.c:289:33: Fehler: »$P$PRE$Pconstantflow1$PconstRate« nicht deklariert (erste Benutzung in dieser Funktion)
TestConveyor.c:289:33: Anmerkung: jeder nicht deklarierte Bezeichner wird nur einmal für jede Funktion, in der er vorkommt, gemeldet
make: *** [TestConveyor.o] Fehler 1

Any suggestions for a workaround are highly welcome!
    Greetings
        Peter

------

Update error, therefore code following:

TestConveyor.mo
------------------------

connector MassPort
  flow Real dm;
  Real data; 
end MassPort;

model ConstantFlow
  MassPort outflow;
  parameter Real constRate = 1.0;
protected
  Real inRate;
  Real rate;
equation
  rate = inRate;
  outflow.dm = -rate;
  inRate = constRate;
end ConstantFlow;

model Conveyor
  MassPort inflow(data(start=0));
  MassPort outflow(data(start=0));
  Modelica.Blocks.Interfaces.RealOutput out1;
  parameter Integer nDelay = 5;
  parameter Modelica.SIunits.Time samplePeriod = 1;
  parameter Modelica.SIunits.Time startTime = 0.1;
protected
  Real store[nDelay-1];
  Real load, last;
equation
  when sample(startTime, samplePeriod) then
    store[1] = pre(inflow.dm);
    store[2:end] = pre(store[1:end-1]);
    last = pre(store[end]);
    load = sum(store);
  end when;
  out1 = load;
  inflow.data = 0;
  outflow.data = last;
end Conveyor;

model TestConveyor
  ConstantFlow constantflow1(constRate = 2);
  Conveyor conveyor1;
equation
  connect(constantflow1.outflow,conveyor1.inflow);
end TestConveyor;

testConveyor.mos
-------------------------
loadModel(Modelica);
loadFile("TestConveyor.mo");
simulate(TestConveyor,startTime=0.0,stopTime=6.0);
plot(conveyor1.outflow.dm);

Has anybody a working example showing a 3d animation of a MultiBody model in openModelica?
I'm a bit confused about what should work (and how) and what is still too come...

    Thanks
       Peter

Ok, everything works now! The problem was: One has to install the dev package of libexpat as well to get the correct links. This is probably a bug in expat, but who cares. Now the daily build works for me. And this makes bug #1599 obsolete - everything works fine.

Thanks for your fast help.
    Peter

Actually it is not in /usr/lib/x86_64-linux-gnu/ !

Confusing results (for me):

> echo "int main() {return 0;}" | gcc -x c - -lexpat



/usr/bin/ld: cannot find -lexpat

collect2: ld returned 1 exit status

and

> locate libexpat.so



/daten/local/prog/matlab2011a/bin/glnxa64/libexpat.so.1

/daten/local/prog/matlab2011a/bin/glnxa64/libexpat.so.1.5.0

/lib/x86_64-linux-gnu/libexpat.so.1

/lib/x86_64-linux-gnu/libexpat.so.1.5.2

/lib32/libexpat.so

/lib32/libexpat.so.1

/lib32/libexpat.so.1.5.2

/usr/lib/vmware/lib/libexpat.so.0

/usr/lib/vmware/lib/libexpat.so.0/libexpat.so.0

/usr/lib/vmware/ovftool/libexpat.so.0

/usr/lib/vmware-installer/1.1/lib/lib/libexpat.so.0

/usr/lib/vmware-installer/1.1/lib/lib/libexpat.so.0/libexpat.so.0

and finally

# ldconfig -v | grep expat

/sbin/ldconfig.real: Pfad »/lib/x86_64-linux-gnu« mehrfach angegeben

/sbin/ldconfig.real: Pfad »/usr/lib/x86_64-linux-gnu« mehrfach angegeben

    libexpat.so.1 -> libexpat.so.1.5.2

    libexpatw.so.1 -> libexpatw.so.1.5.2

    libexpat.so.1 -> libexpat.so.1.5.2

    libexpatw.so.1 -> libexpatw.so.1.5.2

Simulating any model (e.g. with OMShell) on a Ubuntu 11-04 (64 bit) system leads to the error
   /usr/bin/ld: cannot find -lexpat
The expat library is properly installed (checked with ldconfig).

This happens with 9705-1 (nightly-ubuntu) and older versions. 9040-1 (stable) works though.

   Greetings
      Peter