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kinematic always spline fit?

wildfirebrigade

New member
I need to simulate a typical hydraulic crane-arm with
MDO.
I use a path and slot-connection to simulate a desired
movement of the arm and I use a table as input for servo-
motor input on the slot-connection. So far so good in
static-analysis which gives me the position of each
cylinder in time.
Now I want to measure the force on each cylinder in time,
so I run a dynamic analysis with gravity.
After a while I found out that the servo-motor
automatically uses a spline-fit Interpolation instead of
linear fit, though the settings are still the same.
Whats going on?

ps. I find it amazing that there are no really good
tutorials available for MDO, they are all so superficial,
if any..!
 
If a linear fit is used, there may be instances where the velocity or acceleration will become infinite, and of course F=ma will then cause issues with a dynamic analysis! The code needs to smooth-out the table to avoid mathematical "errors" in differentiating a position table. Earlier versions overcompensated too much and could drastically change the position table, depending on your table increment. This has been fixed to rearrange the input data to points very local to any discontinuities in order to preserve the intended original position table.It is fixed in Creo 2 and possibly Creo 1, I can't recall now which one.


Hope this helps.
 
Hi! I am also simulating main boom - jib - extension mechanism and also want to know how to get forces out in following case. My assembly contains two cylinder, one for the jib and one for extension ( jib is as telescope). Extension cylinder is actuating after jib, i.e. when jib is horizontal and parallel to main boom, extension movement starts. l want to use constant cylinder forces and measure max. load @ tip of the extension (in vertical and horizontal direction). Max load is varying in function of boom parts position. In other words l want to know lifting and draging force of the crane.
 
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