Angular Position Measurement in Creo Mechanism

Forum|Forum|4 years ago
July 7, 2021
3 replies
5332 views

Hi All,

I've searched around a bit with no luck thus far. Hopefully this is an easy question.

I'm analyzing a mechanism similar to a universal joint with an output shaft angle that differs from the input shaft angle. My current goal is to plot input angle vs. output angle.

I see angular velocity as a measure in mechanism, but not angular position / rotation. I've set up a user defined measure for angular position based on x displacement & some simple trig, but this obviously isn't accurate once you change quadrants. I could set up a more elaborate user defined measure to account for this, but it seems like there might be a better/easier method for angular position measurement in mechanism?

Thanks in advance.

Mechanism Design

tbraxton

22-Sapphire II

A position measure should be available in deg or radians if the joint has an angular DOF defined. I don't have access to a Mechanism license currently but I have in the past plotted measures in a mechanism using the input crank position as the X axis on a graph for analysis. I was able to plot different measures as a function of the crankshaft position.

On your output shaft is there a connection defined with an angular DOF?

G

GM_6889676

Author

1-Visitor

Thanks for the reply @tbraxton .

No, there is not. That's the basis of my issue. Due to the mechanism design, the output also translates slightly, so I can't strictly fix is as a rotational axis. I do see you can define an angular position measurement if you define a fixed rotational axis. I have no problem measuring the input angle... just the output.

I have a coordinate system defined that translates with the output shaft (that I want to measure rotation relative to). I can measure x and y coordinates relative to this translating coordinate system. If something like the atan2 function was available I could easily make a user defined measurement. I guess I could export the coordinates to excel and use the atan2 function.

tbraxton

22-Sapphire II

If you have two Csys that you want to track relative position of have you considered using the transform matrix measurement function? This would provide the rotation angles (implicitly) of the output shaft relative to your selected reference csys.

To Create info.trf file:
1. Analysis> Measure> Transform
2. Select two coordinate system
3. Click Display information for this feature (blue "i")icon in Transform windows
4. In INFORMATION WINDOWS(info.trf),click File, Save or Save as

Review this for reference:

https://www.ptc.com/en/support/article/CS200881

G

GM_6889676

Author

1-Visitor

I completely forgot about the atan2 function in some programming languages. If this was available in the 'user defined' measurements it would easily solve this problem.

K

KenFarley

21-Topaz II

There is an atan2 function available in Creo relations. Hopefully that means its available to you for your calculations. If it were me, though, given past weird Creo angular math problems, I'd test it out with a bunch of values in all the quadrants to ensure I'd get the right values (i.e. not -90 degrees, but 270 degrees, etc.) Trig functions in programming languages are always such a pain. Converting from degrees to radians and such.

D

Domen_130833