Using Inventor for Arm torque calcs

[kramarczyk]

Originally Posted by ChrisH

Has anyone else out there been playing with this stuff? Or am I the only one who has had the requisite curiosity?

You are not alone. I played with the FEA package a little last year and I concluded that it was linear. I haven't seen anything that leads me to believe that a non-linear material is available.

I also played with the dynamic analysis this fall in trying to simulate the shock loads of reversing the drive train. That was a bit confusing as I couldn't figure out how to model the slack in the system. I hope to take another shot at it shortly to model our gripper/ejector. I'm planning to mount a string pot to a pneumatic cylinder to take displacement vs. time data with LabVIEW and then use that as the input for the dynamic simulation to see if we can optimize it further. We'll see how that pans out.

As far as the original poster is concerned, can you use the CG feature in Inventor to determine the mass and CG location of your 'arm' assembly. If x is the distance from the CG to you pivot as measured parallel to the ground then the minimum torque you need to generate is simply = mass * gravity * x. This torque divided by your motor torque gives you the gear ratio required. Note that if you use the motor's stall torque in the previous eqn then the ratio generated is what is required to stall the arm, not lift it. If you pick a motor torque at the point that you want it to operate, say 25% of stall, then you should be able to move the arm at the corresponding speed. That's a simple way to address the issue, hope it's helpful.