Introduction

• Typical error messages when simulating:
  • Simulink
    • Cannot solve algebraic loop ...
  • Dymola
    • Failed to reduce the DAE index.
• Possible causes:
  • novice modeller: "bug in simulation programm"
  • experienced modeller: "bug in own model"
  • reality: mathematical problem in model
• Why mathematics fails:
  • modeling needs simplification
  • oversimplification
    • → model becomes unphysical
    • → mathematical description incomplete or inconsistent
• Remedies:
  • extend or fix mathematical description
    • can lead to unphysical behaviour
    • can be difficult to implement
  • add physical details to model
    • mathematical problems disappear
    • but: model has (often lots of) new parameters