Hello,
I have experience in SW simulation of parts (i.e. assemblies with no internal degrees of freedom, which I call kinematic sets. Another way to put this is to say kinematic sets are sets of parts rigidly linked together and which move together). Now I am willing to perform a simulation of an assembly with internal degrees of freedom (i.e. the system now includes different kinematic sets linked by prismatic and pivot linkages), this is all new to me. I have reviewed the different ways offered by SW simulation to solve such a system, but as this is new to me I do not feel confident on which approach I should use - i.e. which approach is the most standard.
Here are the methods I could think about:
- Simulate each kinematic set individually: compute the efforts at all internal and external links (to get to know the interactions between kinematic sets) then simulate each kinematic set individually
- This brings me back to the situation I know how to handle in SW
- But I need an extra stage where I compute all the link efforts. Getting these link efforts can be done in several ways:
- A static study by hand: this is the "back to school" way where you simplify your system, write the equations and solve them
- I find this approach time consuming and error prone
- Perform a motion study: motion studies allow to record the efforts in links (over time) and later import these in SW simulation
- This is more than what I want to do (as you study the system for a range of time - which I do not really need)
- You need the Motion plugin in order to do so
- Simulate kinematic sets one after another: simulate a single kinematic set, probe the resultant efforts in the links (this is done is SW simulation) then simulate the contiguous kinematic set (re-applying the resultant efforts probed at the previous kinematic set)
- This may not be very accurate as the resultant efforts over a whole link may arise from a very non-uniform distribution of the constraints inside the link (there can even be opposite constraints inside the same link)
- Hence the resultant effort may not represent the behavior inside the link
- A static study by hand: this is the "back to school" way where you simplify your system, write the equations and solve them
- Simulate links using contacts: you use the geometry of the link to simulate its kinematic effect
- Very resource intensive and does not always find a solution
- Need to simplify the model in case of complex geometry (rather often)
- Seems overkill (but I am not an expert)
- Parametric link: use the mates put in place in the modeler to set-up constraints on the mesh nodes
- This "gut feeling solution" does not not seem to be possible for some (dark) theoretical reasons
- More specifically: I find it weird to be able to specify parametric mechanical links for the fixtures (prismatic, pivot...) but not to be able to do so for connection
- I guess there is a theoretical reason behind this which finds its roots in the FEM used by the simulation (but this goes beyond my knowledge of simulation)
Anyone having advice on the technique I should use? What is the most standard approach used by the professionals? My gut feeling is that using contacts seems the easiest way, though is seems a bit overkill...
Thanks for your help,
Antoine.
when you say movable links and mechanical links, you mean the guides right?
your options are either include them and apply contact
or don't include them and fix them