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Using CombitTables for quarter car modelling (Open loop)

Posted 9 years ago

Hi,

I am trying to use SystemModeler to simulate a quarter car. I've been using the multi body library. I'm struggling to understand how to make use of the CombiTable component in the Modelica library. The plan is to first model a quarter open-loop, then move onto the closed loop. Later then to also model a full car. I understand i still have a mountain ahead of me.

Im trying to model the system with having the floor being the point of excitation. We were given a set of values that we needed to read from.

A this stage these are my problems: 1. Is the model correct? (I removed the prismatic joints and the one fixed point because of an error I kept receiving) 2. What is the window asking for when I try to connect the CombiTable to my model? I can't find any documentation explaining (simply enough for someone like me to understand). I have attached the files needed to complete the simulation. Please excuse my basic understanding of the program (coding + syntax is almost non-existent!)

Any help with this problem is greatly appreciated!

enter image description here

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POSTED BY: bjorn bellmann

Hi Bjorn! Cool model, though I can not tell you anything about its correctness. Hopefully I can help you with your CombiTimeTable problems instead!

A CombiTimeTable can contain several dataset in a single table, so the first part of the dialog is asking you to specify which dataset you want to connect from. Multibody forces are three-dimensional so the second part of the dialog is asking you in which direction you want the force to be applied to.

The 3 signals of the force connector are interpreted as the x-, y- and z-coordinates of a force acting at the frame connector to which frame_b of this component is attached.

I think your datafile need to be in a certain format for CombiTimeTable to be able to read it. One easy way to create such files is using Mathematica:

Needs["WSMLink`"];
Export["combitimetable.txt", {{"var1", {{0, 0}, {1, 2}, {2, 
      4}}}, {"var2", {{0, 2}, {1, 3}, {2, 
      4}}}}, {"ModelicaCombiTimeTable"}]

I have attached your data in the CombiTimeTable format. Please note that you will need to specify the table name "vehicleForce" in the tableName parameter and the columns to read from {2,3} in the columns parameter. When you do that the output from your CombiTimeTable will be an 2-dimensional array where y[1] will be the interpolated values from the second column and y[2] from the third.

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POSTED BY: Patrik Ekenberg
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