Unable to determine signal dimensions

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Mark Hiteshew 2018-4-26

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https://ww2.mathworks.cn/matlabcentral/answers/397571-unable-to-determine-signal-dimensions

编辑： Bryan Callaway 2019-1-15

I am moving a model from 2010a to 2016b. The model works fine in 2010a. When I move to 2016b, I get this error "Unable to determine signal dimensions. There is a loop consisting of 'base/From2' that cannot be resolved because signal dimensions are defined by a cyclic relationship."

Basically, my base model has four blocks that all have buses with lots of signals on them. If I grab the signals I need for a given block at the top 'base' level and THEN input them to the block using them, this problem goes away. But if I take a bus signal and input that to a couple of different blocks and grab the individual signals inside the block using the signal, it gives me this error. I can use a bus structure to solve the problem, but I prefer to not use it because our bus is extremely complicated and has a lot of variables that vary in size from run to run, which gets complicated with the bus structure.

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Answer 1

Mark McBroom 2018-4-28

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https://ww2.mathworks.cn/matlabcentral/answers/397571-unable-to-determine-signal-dimensions#answer_317660

You could try placing a signal specification block on the signals that are giving you problems. Place the block on the signal before the bus is created and specify the Dimension of the signal.

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Bryan Callaway 2019-1-15

编辑：Bryan Callaway 2019-1-15

I have a similar problem popping up all over my model. The first instance I solved by moving the bus out of the function, as described in the orignal problem statement; the next instance I solved by adding a signal specification. But now I am getting errors that the signal specification block apparently does not solve, where I would rather not move the bus outside.

EDIT: Enlarged the screenshot.

Additional edit: turns out that, far away from here, I was giving a bus as an input where I should have been selecting one element from a bus. Apparently the output to that input became an array the size of the bus and looped, resulting in an explosion of bus dimensions, hence 29(917477) in the image below. All of this hapenned far away from the bus selector that Simulink highlighted.