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# RE: [femm] Automation

- To: "'femm@yahoogroups.com'" <femm@yahoogroups.com>
- Subject: RE: [femm] Automation
- From: Finlay Evans <finlay.evans@renishaw.com>
- Date: Thu, 23 May 2002 09:00:23 +0100

    Hi,

    There is a way to do what you want, using Lua scripting, but it takes a bit
    of setting up initially.

    I have several models, mostly motors, whereby I step the armature along with
    respect to the stator, calculating the force as I go. The results of the
    force calculation get appended to a file, then I use Matlab to plot it.

    Basically what I do is parameterise my model into several parameters which
    completely define the model, so that after assigning values to each
    parameter I can call a Lua script which reads in the parameters and draws
    the model. The same script assigns block properties (including correctly
    phased current blocks for coils), meshes the model and saves it to a
    temp.fem file name before solving.

    In full, I have a controlling script which does the following:-

    Step 1:	Define the simulation. Define parameter values, and which ones will
    vary over the simulation etc.
    Write a parameter file.

    Step 2:	Open the data file and write some header info, such as model type,
    number of simulations etc. then close the data file again.

    Step 3:	Do a For loop that completes a series of individual simulations by
    calling 2 Lua scripts.
    The first script reads in the parameter file, creates the model file as
    described above, saves it to a model file and solves the model. It then
    calls the second script to extract the force, and then exits.

    The second script does the following:
    Reads in the parameter file. Amongst the variables calculated from my
    model parameters are co-ordinates of points that define an acceptable
    integration path for force calculation. I also have several key points,
    again defined by variables, that I extract flux densities from so that I can
    collect information about saturations or flux reversals in important areas.
    This force and flux information is then written to the data file in append
    mode along with the current model parameters, before exiting the
    postprocessor.

    Back in the control script, I then increment a parameter and create a new
    parameter file, ready for the next loop.

    At the end of the loop I delete the solution files generated by triangle to
    clean up a bit, and am left with a single data file containing header
    information, and rows of parameter information and the forces and flux
    densities I calculated. One row for each simulation point.

    You can plot results using Excel, Matlab (or the free Scilab which is
    great!) or anything that can read a text file.

    I have used this method for simulations up to 600 points long (even a matrix
    of 20 x 30 solutions). The only snag I get is that somewhere in the code
    there is a gradual build up of memory not released, and Femm hangs after
    about 600 or so simulation points.

    It takes a while to set up, but if you want detailed simulations over a
    parameter range it works very well.

    It is possible to automate this using active X controls, so that the
    controlling script is written in your language of choice (Matlab, Visual
    Basic etc.). Femm and Lua then run in the background and your front end
    can have a pictorial view of the model you are using. I am (have been)
    working on implementing the controls into the code, but I don't have time to
    finish it at the moment. Anyone else doing something similar?

    Finlay Evans.

    ----Original Message-----
    From: agnaldo@if.ufrj.br [mailto:agnaldo@if.ufrj.br]
    Sent: 22 May 2002 17:14
    To: femm@yahoogroups.com
    Subject: [femm] Automation

    Hi people!
    Does anybody know how to perform force calculations in an automatic way
    using
    femm?
    I mean something like a command that would allow the automatic variation of
    distance between two blocks, force calculation and graphic presentation.
    Is there any possibility?

    Agnaldo

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