Inventor doesn't model deforming materials such as rubber, fabric, rope etc.
If the reason for needing movement is for display or presentation, the only easy way I can think of at the moment is to model the accordion as a solid or as a surface (.ipt) and create a parameter for the distance between the peaks (Pitch). You can animate this parameter inside Inventor Studio and the accordion will look as it's compressing and expanding. Check the quick video I attach.
Can't think of a simple way to do it and move it "live" in the Assembly environment.
Hope this helps...
AttachmentsAcc_Video.avi, 1.97 MB
that's what i thought... thanks for the confirmation :)