How to use Joint functions in Inspire Motion?

Question

The Joint functions in Inspire are different from MotionView's. What's the right way to use them?

this is motionsolve:

I verified in MotionSolve that this fixed flexible joint does carry force in the X direction. But when I use the Joint function to measure or output it, the force reads zero.

I have a template that doesn't seem to take effect in Inspire Motion, but it works fine when imported directly into MotionSolve. Has anyone encountered this issue?

Vishvam · Accepted Answer

Hello @Jin1 Regarding the expression for Joints query. As you mentioned, the expression should be similar to the Motionsolve documentation. The option to choose the component seems to be missing in the expression builder in Inspire Motion. I will raise this issue with the dev team. For now you can use the comp parameter in the expression to be 2 for X-component of force. This should work in your case. JOINT({MODEL.Joint_1.idstring},0,2,0)

Regarding the template issue. If you're using v2026.1 of Inspire, then we have a new feature of easily controlling the simulation and entities, without creating a template. Please refer below image. A new Analysis can be created from Analyst profile, and you can add different type of commands directly in the model. Hope this helps! Regards, Vishvam

Vishvam · Accepted Answer

The expression should work. You can share the motionview model of 4 bar mechansim. I can check it and let you know the exact issue which might be causing it. If you interested in the forces on the joints, then this output is automatically created when the Inspire model is exported to Motionview by default.

Altearnatively, you can also create the Joint Force output as follows directly instead of writing an expression.

For expression error, please share the model

1) Go to File -- Export -- Model -- Click on "Archive Model" and Check the "Create ZIP File" checkbox.

2) Choose the directory and export the model. This should create a zip folder with the mdl file and any geometry files being used in that.

Vishvam · Accepted Answer

Hello @Jin1,

I went through your model and found that Joint_1 is defined as a compliant joint, which means it is treated as a flexible joint in Inspire terms. In the MotionSolve solver deck, compliant joints are represented as bushing elements. Therefore, the BUSH expression you are using is the correct approach.

The only issue with your expression is that it still references the Joint ID. For a bushing expression, you should reference the Compliant Joint ID instead.

If you use the Expression Builder in MotionView, you can find the correct ID under the corresponding compliant joint in the following location.

The expression would look something like below for bushing/compliant joints.

BUSH({Joint_1.bush.id},0,2,0)

I have tried this expression and this works and shows the forces in the .plt file.

Hope this helps!

Regards,

Vishvam