Make your Simcenter Amesim model real-time compatible

«A good model is a judicious trade-off between realism and simplicity.” [Anu Maria, Introduction to modeling and simulation]

Make-your-Simcenter-Amesim-model-real-time-compatible.jpgThis statement perfectly highlights the challenge of choosing the right level of modeling / assumptions when starting a new simulation study. It is particularly true when you want to reach real-time capability for doing virtual sensing, IIOT on edge, model-based system testing or simply want to have your model running faster.

In this blog post, we provide you with some tips on how to make your Simcenter Amesim models run faster.

This can be done through the following best practices:



  • Avoid generating implicit variables

  • Avoid useless states variables

  • Define the best simulation run parameters

  • Avoid useless discontinuities

  • Save only useful variables

  • Condition correctly your maps


 


Avoid generating implicit variables


Implicit variables are generated by the solver whenever there is an algebraic loop in the system. An algebraic loop occurs when there is no order in which the submodels can be called such that all the inputs of each submodel are known when the submodel is called.


Example: ? = (?, ?)

Simcenter-Amesim-model-reduction1.png

The solution to remove an implicit loop can be to include a time constant within the loop (inertia, first order lag, inductor …) or to remove the calculation of the variable generating the algebraic loop.


 


Avoid useless states variablesSimcenter-Amesim-model-reduction2.png


The computation time is directly impacted by the number of states N. For a standard problem to solve within Simcenter Amesim, Adams’ method is used where CPU = k*N. When backward differential formulae method is used, CPU=k1*N + k2*N².

The solution to reduce the number of states variables is to group hydraulic volumes, mechanical masses or electric resistances.


 


Define the best run parameters


Usually, the higher the tolerance of the integrator is, the higher the simulation time is.Simcenter-Amesim-model-reduction3.png

The solution is to minimize the tolerance parameter without compromising the simulation results accuracy.


 


Avoid useless discontinuities


A discontinuity appears when a variable is suddenly jumping from one value to another (switch from laminar to turbulent flow, friction stick-slip, hysteresis…). This causes a restart of the solver to manage the interpolation between the two values.Simcenter-Amesim-model-reduction4.png

The solution for avoiding useless discontinuities can be to disable the discontinuity handling of tabulated submodels (when possible) or to add damping.


 


Save only useful variables


Simulation results are written in a data file all along the simulation and by default all submodels variables are saved (the frequency of the results saving is set by the user in Run Parameters’ Print interval).Simcenter-Amesim-model-reduction5.png

The solution for reducing the number of saved data is either to save only the required variables or to increase the print interval (for the complete simulation or dynamically during the simulation).


 


Condition correctly your maps


Maps imported from experimental data can typically be quite noisy or contain discontinuities.Simcenter-Amesim-model-reduction6.png

The solution to properly condition your maps is either to disable the discontinuity handling, use an appropriate data sample or filter the noisy signals.


Simcenter-Amesim-model-reduction7.png

 


Print out our step-by-step process 


Most of the information above are explained in the infographic below, for the particular case of reaching real-time capacity:


Make-your-Simcenter-Amesim-model-real-time-compatible-infographic.png

Finally, a dedicated hands-on workshop can be organized on-site to walk you through the process.


 


Need more information?


Contact your local Siemens PLM team or ask a question on our System Simulation Forum

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