SimMechanics - Spherical Joint "kinematic constraint cannot be maintained"

Question

Christopher 2013-7-25

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https://ww2.mathworks.cn/matlabcentral/answers/83132-simmechanics-spherical-joint-kinematic-constraint-cannot-be-maintained

评论： Muhammad Suleman Shafqat 2023-10-31

Hi,

I developed a more or less complex SimMechanics model with different types of joints. The model diagram can be updatet as well as the visualization in the mechanics explorer without any problems. But when I want to simulate the model, there is always a failure with the spherical joints. The following message comes up:

"kinematic constraints cannot be maintained. Check solver type and consistency tolerance in the Simscape Solver Configuration block. Check Simulink solver type and tolerances in Model Configuration Parameters. A kinematic singularity might be the source of this problem."

Do you have any clue how to solve this problem or how to analyze it?

Thank you very much in advance!

Kind regards, Chris

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祺 2023-9-26

How did you solve the problem in the end

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Answer 1

Guy Rouleau 2013-7-25

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Open the loop by removing one of the joints. Then connect one sensor on each CS that was connected to the loop. Simulate for 0 seconds. You should see that their position does not match. Then go up on the branch that is not where you think it should be and you should be able to figure out why the loop cannot be closed.

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Mohammed 2016-1-19

This is in First generation. How can I connect sensor on each CS in Second generation to know their positions don't match

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Answer 2

Christopher 2013-7-26

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https://ww2.mathworks.cn/matlabcentral/answers/83132-simmechanics-spherical-joint-kinematic-constraint-cannot-be-maintained#answer_92809

Thanks to you both for your answers!! @ Tony: There are several spherical joints and revolute joints. What more information do you need?

@ Guy: I did this. The position deviation is less than 1e-11 [m]. That should be ok, is it?

If I increase the consistency tolerance in the solver configuration to about 1e-1 the model runs for a few seconds. But the position of the joints is moving and it looks like the joints are not assembled.