Over-Constrained mechanism

hi,

I am want to model overconstrained Mechanism in MotionView/MotionSolve. Is it possible to simulate the behavior of the over-constrained mechanism in MotionSolve?

Warning: Row Deficiency Detected:
This may indicate a kinematic model or over constrained model.
Program will continue with redundant constraints removal.

From the warning I understand that the program is not for over-constrained models.

Any suggestions ?

Thanks.

Manisha

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Altair Forum User

Hi Manisha,

MotionSolve will automatically remove any over constrained model. It looks like the same has happened in your case.

You can either play around with different joints to check and remove redundancy.

If you still have problem, please share the .mdl file with us to debug.

Altair Forum User

Hi Prakash,

The Mechanism is an over-constrained with mobility 1. Is it not possible to get the desired motion of structure for over-constrained with MotionSolve?

Thanks.

Regards,
Manisha

Altair Forum User

Hi Manisha,

can you share the h3d (close-open_without_constraints.h3d) file used to generate the bodies?

Altair Forum User

Hi Manisha,

I think you missed to connect one of the bodies to ground body so that it will not fall continuously. Can you connect one of the relavant joints to ground body and check if you are able to desired motion?

Altair Forum User

Hi Prakash,

I did that, and still the software tries to break one of the joints.

Altair Forum User

My Question would be, is it possible to simulate over-constrained mechanism using MotionView? Are there any Software which does that? Or do I modify one of the rigid bodies?

Altair Forum User

I think if you convert your rigid body model into flexible one you might get what you want.

Altair Forum User

Hi,

I am facing same issue of in motionView during simulation

WARNING: Row Deficiency Detected!

This may indicate a kinematic or over-constrained model.
Program will continue with redundant constraints removal.

INFO: Total Number of Independent Coordinates = 14

How I can check for ovre-constrain model

Simon Križnik

Hi @jadhavsw

The model checker can be found in menu at Tools > Check Model. If one discovers that the sum of the DOF is negative during the model check, the chosen joints will have to be checked again and to be modified. A negative count for DOF implies that some of the constraints are redundant. MotionSolve will release the necessary constraints to obtain a determinate system.

from Practical Aspects of Multi-Body Simulation with HyperWorks:

Avoid Redundant Constraints
• Use joint primitives to precisely impose only the necessary constraints and avoid introducing redundant ones. This may
require much thought in case of complex mechanisms.
• If the above step is not feasible, then consider using flexible bodies. Flexible bodies add degrees of freedom to your
model and reduce the likelihood of a redundant constraint. They may also provide more accurate results.