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Not able to find variables used in Stewart platform model on simscape multibody (matlab 2018b)

Asked by Enrico Puglisi on 10 Oct 2018
Latest activity Answered by Alisha Schor on 24 Oct 2018
Hi all, I'm studying the Stewart platform model provided by matlab as example (it can be runned using the command sm_stewart_platform) to get some insight on multibody modelling in Simscape environment. The model in the example is fully customizable by the use of many parameters, the problem is that I'm not able to find where those parameters are defined. For example, to describe the base of the platform in 'Stewart Platform System/Manipulator/Base/Skewed Hexagon' the variable cross_sect is used in a solid block to define the points from which an extrusion is generated. Well, I can't find where this variable is defined, it isn't neither in the Base nor in the Model Workspace. I even tried with:
>> Simulink.findVars('sm_stewart_platform', 'Name', 'cross_sect')
Thank you in advance for the help!

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1 Answer

Answer by Alisha Schor on 24 Oct 2018

Hi Enrico,
Most of the parameters appear to be defined as mask parameters (see the Documentation on Block Masks for more info). They are entered by double-clicking on the mask, and then subsequent values are sometimes calculated from those. For example, you can find where "cross_sect" is calculated as follows:
  1. Navigate to the Skewed Hexagon: sm_stewart_platform/Stewart Platform System/Manipulator/Platform
  2. Select the block and press Ctrl+M or right-click the block and choose Mask > View Mask...
  3. In the Mask Editor dialog that opens, click the Initialization tab.
  4. You can see here that cross_sect is calculated from angles, which in turn is calculated from skew, which in turn is a parameter that you enter in the mask dialog (and has the value hex_skew here).
In short, there are lots of nested mask parameters and some values calculated based on those. If the documentation above is not sufficient, there is also a walkthrough on how to create a mask that should help clarify how they work.

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