# Thread: Dynamics Analysis- Redundancy Problem

1. Hi guys,

I am currently running dynamic analysis of a complex assembly.

Some force results are obviously wrong and I assume it is due to constraints redundancy.

Since the assembly is very complex, is there a function in proe that would examine the redundancy automatically, or do i have to calculate it myself?

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2. Are you using MDO to solve your problem or Mechanica. If you are using MDO, there is a measure you can plot of the redundancy for the system. You can also have it report the DOFs in the system as well. It will not indicate where these redundancies are, so you will need to thoroughly go through the model, using the DOF at each joint, and determine where it is you need to release DOFs to reduce the redundancies.

If you are using Mechanica on an assembly, you will be getting accurate forces at all contact surfaces IF each individual contact location is its own surface to report its own contact force reaction. Pro/E likes to lump surfaces together that are made from the same feature even though they may be discontinuous.

Hope this helps.

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3. Originally Posted by Kaz Z06
Are you using MDO to solve your problem or Mechanica. If you are using MDO, there is a measure you can plot of the redundancy for the system. You can also have it report the DOFs in the system as well. It will not indicate where these redundancies are, so you will need to thoroughly go through the model, using the DOF at each joint, and determine where it is you need to release DOFs to reduce the redundancies.

If you are using Mechanica on an assembly, you will be getting accurate forces at all contact surfaces IF each individual contact location is its own surface to report its own contact force reaction. Pro/E likes to lump surfaces together that are made from the same feature even though they may be discontinuous.

Hope this helps.

Thanks for the reply. I am using Mechanism to conduct my dynamic analysis. I am still confused about how to use DOF at each joint, and do I have to assign a new coordinate system at each joint?

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4. Your best bet to understand DOFs is to look at the on-line guide. Coordinate systems are required for "6DOF" and "weld" joint in WF4. There are tutorials included with on-line documentation as well that would be very helpful. Take a look at these then post any questions you may have.

Cheers,

Kaz

5. Hello Kaz,
I have read your comments on redundancies in mechanism. I am simulating a power transmission mechanism, I am too facing the problem of redundancies but I am unable to do it.

I am not understanding which constraint should in assembling L-links with hub so that I get rid of redundancies. I have used cylinder connection at input and output hub and different combinations of connections, but none solved my problem.
If you could give me some insight about it. Thanks

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