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Simscape Loaded contact friction issue

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singdt
singdt on 23 Aug 2016
Answered: Steve Miller on 6 Aug 2020
My system has a rack and pinion connection where one of the rack teeth is cut large to produce friction over just that tooth. I am trying to reproduce this localized friction with the loaded contact rotational friction block. The simulation is throwing the error "Transient initialization, solving for consistent states and modes, failed to converge." at simulation start. Am I missing anything obvious, and if not how else might I achieve this?
Attached are images of my simplified system and desired output.

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Swarooph
Swarooph on 24 Aug 2016
Would it make sense to add another inertia on the other side of the contact friction block? I have a feeling the solver is having trouble solving for an ideal situation..
singdt
singdt on 24 Aug 2016
As in put an inertia directly on the fixed point ("housing")?
Swarooph
Swarooph on 29 Aug 2016
Something like that. At this point the 'F' side of the loaded contact friction is mass-less. So adding an inertia on this side that corresponds to the housing might help. I am guessing you have not modeled the full rack and pinion structure yet? When you do that, maybe this end wont be left 'free wheeling' after all, so it will be automatically accounted for in your future developments.

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Answers (1)

Steve Miller
Steve Miller on 6 Aug 2020
I assembled a comparable model and get similar results. This model runs fine in R2018b, though it looks like you are using an earlier release. It does not match your images exactly, but if you enter your parameters I bet it will.
I am guessing you did not wrap the angle coming from the Ideal Rotational Motion Sensor. In earlier releases you had to put extra blocks to handle that, in the current release it is a setting on the block to wrap the angle.

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