Analysis Feature - Distance (+/-)

[jveliquette]

Ive got a working mechanism in WF3.0 and looking to harvest some data from my model. I'd like to have the graph tool plot distance (positive & negative values) as a cam connection travels through it's path. The end result would then be the fore and aft travel from a 'zero' point in both directions. The trouble is the analysis feature I've created keeps data as entirely positive.


Does anyone know of a workaround?

 

[AHA-D]

Can't you get a zero point at maximum or minimum distance. The travel will then be entirely positive by nature, but you know the medium point is in the middle, so you can work it out from there. In mathematical terms : get the analysis to have the X-axis at the bottom of the graph instead of in the middle.

 

[jveliquette]

Here is a screenshot. I understand why the analysis feature I've set up doesn't produce the results Im looking for, but maybe someone has insite into how I could manipulate the analysis or the exported data in excel to put in a more clear format for laypersons who may have a look at this data.


Thanks!

 

[pjw]

How can you have a minus distance?

 

[Kaz Z06]

It is possible to create measures that do recognize direction from a given reference. You must create the measure in "Standard" mode first,and you must have BMX (Behavioral Modeling)as well. Since this is a cam contact point location you wish to track, first create an analysis feature of a distance measurement between the two surfaces that define your cam pair. Inside this measure dialog, check to make sure you create either the "from" or "to" point. This will make a datum point that will always be located at the contact of the two cam surfaces. Next, create a coordinate system that orients and locates one of its axes to point in the direction you wish to measure along. Now, create another analysis feature (distance measure) between the cam contact point and the coordinate system and make sure you select "projected" distance as an option and select the same coordinate system as the reference. Before you close this dialog, make sure check the box to record the projected distance in the direction you need to track (my example is in the "Y" direction). MDX/MDO will automatically track this measure and return positive and negative values for the distance since it's WRT a co-ord direction. My example below shows the non-signed measure and the directional, signed measure plotted together for a cam pair.





The only time this will, in a sense,"fall apart" is if your cam surfaces separate (enable liftoff selected). The measure will still work for this case, but it obviously won't give you the same info.


Cheers,


Chris

 

[jveliquette]

I've found a decent work around. As for having a minus distance, your right, you cannot have a minus distance. What I'm trying to capture though is the path of a point on cam surface (initial contact point) versus a point at the theoretical center of the second cam surface, through the path of cam motion. What I did was used an arbitrary point on first cam surface that will never cross the theoretical center on the second cam surface. After running the motion, and exporting the data to excel, I've modified the data to plot the distance vs. time, with the distance values being less the initial value to establish a zero point. Below is the same motion, using the modified analysis...giving me a plot representing my intentions. Hope this is clear and helps someone in the future.


As you can see, the distance not 'zeroing' creates the appearance in the first analysis plot that the motion is not uniform across a point (which it is). The second plot conveys the idea of uniform travel much more clearly.


Thanks again to all.

 

[Kaz Z06]

I want to make sure it is very clear to everyone thatit is very possible to have positive and negative values for distance measurements. I have done it many times. Again, the only prerequisite is that youmust to have a license of BMX to accomplish it. If BMX is a license that you do not have, I would very highly recommend addingit as Behavioral Modeling is an extremely powerful engineering design & analysis tool. As far as the posted work-around. There is no need to move the data to Excel. You can accomplish the same claculations as a custom measure inside MDX/MDO. Extract your initial zero point from a measure "at time" equal to zero and use this value in an equation as part of a custom measure to generate your offsset curve.


Chris

 

[jveliquette]

Thanks Kaz, I have successfully applied your suggestions and gotten graphtool to produce the exact results I was looking for. I appreciate your adamancy.


Now for an additional question. I would like to measure the length along my cam surface between the starting contact point on my cam surface and the maximum displacement contact point along my cam surface. I attempted to utilize the trace feature, but because that contact point is continually travelling along the cam surface, the trace feature seems to not want to plot this curve (I do have regeneration always enabled for the (Point_To) analysis point of which I'd like the travel along my curve measured. Obviously I could develop the contact points max and min, and drop a curve between the two, but I'd like to know if mechanism (and more thanlikely, trace) can offer me anything here.