I started playing around today with Solidworks' physical dynamics modeling while developing ideas for a simple, secondary mechanism for our 2007 robot. I thought it might be interesting for others to see how you can assign dynamic properties to parts in an assembly and simulate the interaction of parts based on those properties. For my purposes, I added gravity, a rotary motor at the arm's shoulder joint and a linear spring at the wrist.
Here's the first prototypical model:
http://youtube.com/watch?v=qZKbm0RZX_w
It turns out that allowing the wrist to become colinear with the rest of the arm is bad, so I made some quick changes to the wrist part and arrived at a better solution.
http://youtube.com/watch?v=TJM-8YpX0S4
That works just as I was expecting and hoping -- and I learned that all without cutting a single piece of metal.
I thought that was pretty neat.