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Motion Analysis Motor Calculation Issues

Question asked by John Sebree on Sep 2, 2014
Latest reply on Sep 5, 2014 by Jared Conway

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I've been trying to convert an animation that i have been working on to a motion analysis study so that i can perform a stress analysis on the study. However, when i switch to motion analysis, i have a number of different problems. The most influential one is that my motors no longer work and cause my study to be unable to calculate. The study will calculate right up until the motors are supposed to become active. Solidworks gives me a list of reasons why this little crash might be happening, but i have worked my way through the list to the best of my abilities, and cant seem to find a solution to my problem. I would appreciate any and all help that i can get! Thanks!

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Jared Conway Sep 2, 2014 2:21 PM
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how many redunancies?
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- John Sebree @ Jared Conway on Sep 2, 2014 3:03 PM
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  None that i know of
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  - Jared Conway @ John Sebree on Sep 3, 2014 12:06 AM
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    when you start solving, check the results tree, it will tell you what your grubler count is and the number of redundancies
    
    what you describe sounds like an assembly that was built in solidworks for animation or dragging but not for motion. ie there are mates that are over constraining the assembly such that when you try to drive in motion where everything is taken into account it starts to break down. you can try basic motion if you don't care so much about the engineering outputs. it is a little less stringent. but then you'll lose your ability to export to fea.
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    - John Sebree @ Jared Conway on Sep 3, 2014 10:02 AM
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      It says 349 redundancies... I'm going ti assume that is quite high?
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      - Jared Conway @ John Sebree on Sep 4, 2014 4:08 PM
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        bushings is probably not going to help you here
        really should look at building an assembly for motion specifically
        if you want good exports to simulation, you need zero redundancies
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    - John Sebree @ Jared Conway on Sep 3, 2014 10:12 AM
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      I tried the "replace redundant mates with bushings" option in the Motion Study Properties menu yesterday, and the results remained unsuccessful. Is there another method to remove the existing mate redundancies?
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      - John Sebree @ John Sebree on Sep 4, 2014 4:55 PM
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        Sounds good, what do you recommend that i do differently in an assembly specific for motion?
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        Jared Conway @ John Sebree on Sep 5, 2014 12:57 PM
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        minimize assembly level mates
        which means making subassemblies..etc.
        concentrate on not duplicating any DOF restraints
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Roland Schwarz Sep 4, 2014 5:32 PM
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Motors in SW Motion have never worked right. SW PTBs insist that they should and do work right, but I've never seen it happen. Even the simplest mechanism with constant speed motor gets verbuggert.
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- Jared Conway @ Roland Schwarz on Sep 5, 2014 12:58 PM
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  different experience here. a good assembly with motors works pretty good.
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  - Roland Schwarz @ Jared Conway on Sep 5, 2014 1:25 PM
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    Lots of say-so, but still plenty of no-show. Every time I've presented this to a VAR for help, the issue trickled off into oblivion without a solution.
    
    Yes, Jared, I've tried experiments on simplified mechanisms and made sure there were no redundant mates. No dice. If a constant speed motor pushes a mechanism through a variable force resistance, it just doesn't work. Everyone likes to say I'm doing it wrong but no one has come through to show how it's "done right". Usually ends more like "Hmm.. it shouldn't do that... I'll keep trying and get back to you."
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    - Jared Conway @ Roland Schwarz on Sep 5, 2014 1:58 PM
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      jared@hawkridgesys.com next time you run into that, would love to take a look.
      
      the only time i've seen a motor go sideways other than lots of redundancies is if you try and drive 2 parts together where one is fixed using a motor. eventually the contact breaks down. but from a physical perspective, the motor would probably just burn out.
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Motion Analysis Motor Calculation Issues

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