topic Re: Dynamic simulation bug in Inventor Forum

Dynamic simulation bug

Roger4562 — Thu, 21 Mar 2024 11:02:32 GMT

I have an issue with dynamic simulation in Inventor 2024 and it appears to be a bug.

I have an assembly (unfortunately I can't upload it as it is a prototype) and it contains a revolution joint. I've set it so that after 1 second it ramps up to a constant 14400 degrees per second until 5 seconds using a cubic ramp. As it revolves, other parts of the assemble enact forces on other parts and most of the time I get the consistent results that I would expect.

However, I've noticed that if I 'tug' too much at the revolution joint in assembly mode, which changes it's start position, then when I run the dynamic simulation then I don't get consistent results. It's as if the simulation is not considering every change of degree of the revolution joint as time progresses and I get 'wonky' results.

The problem is I can't 'reset' this behaviour. Undoing the 'tug' (ctrl z) to got back to the previous start position doesn't help. Restarting Inventor doesn't help. I can't see any function in VBA to reset it that would help. I've even tried changing the advanced settings such as solver precision. Nothing seems to fix it. Once I have this wonky simulation then it remains wonky.

The only work around I have is to go back to a previously saved version of the assembly. So this bug is saved into assembly files.

Any ideas how to 'reset' dynamic simulation?

Roger

Re: Dynamic simulation bug

JDMather — Thu, 21 Mar 2024 11:19:14 GMT

Set Initial Positions before moving anything (I also set “Home Position” constraints in assembly environment that I suppress before going into Dynamic Simulation.

Best to only simulate through Joint Imposed Motion and not through mouse dragging.

If you are going to impose motion through mouse dragging - be sure to increase number of time steps first and move slowly so as not to overrun the calculations.

Re: Dynamic simulation bug

Roger4562 — Thu, 21 Mar 2024 12:07:24 GMT

I am using imposed motion as I explain (the cubic ramp) to perform the dynamic simulation. I've also tried altering initial positions in dynamic simulation.

The issue is, I have to perform mouse dragging to tug the parts in the assembly into place as I assemble new prototypes. But I've worked out if I tug too hard then I can not perform an accurate dynamic simulation. So I'm looking for a way to 'reset' dynamic simulation rather than having to go back to previously saved versions, which is time consuming.

Roger

Re: Dynamic simulation bug

JDMather — Thu, 21 Mar 2024 13:23:09 GMT

Locked Home Positions in Assembly Environment

Initial Positions in Dynamic Simulation Environment

Without actual files - it is difficult to offer specific advice.

I might have some examples in here somewhere...

https://www.youtube.com/playlist?list=PLp5izJt_zvN08mpY4UcYrzJV2N6QOLAIR

https://www.youtube.com/playlist?list=PLp5izJt_zvN0GnwEUFR1zE06nQvDAWxz2

Check in particular the Dancing Robot Practice and Pick and Place Robot Practice videos.

Re: Dynamic simulation bug

Roger4562 — Thu, 21 Mar 2024 17:48:08 GMT

Thanks, I'll take a look. I think as you say the key is to lock everything down as you assemble, I'm just hoping there was a way to 'reset' an assembly in case you haven't done that, I haven't found a way yet, but I'll try adding more locked home positions in assembly and see if that helps