Arm's not moving: Mechanical or Programming

Technical Technical Discussion
1

Visually, our motor appears to be stalling out, the motor just “twitches” - but its acting the same regardless of if the arm is in the “upswing” or “downswing” - we’re beating our heads against the wall and need some advice on which direction to trouble shoot…

  • motor is currently a miniCIM (we started this morning with a PG71, same problem), 10 tooth sprocket to 42 sprocket on a hex shaft, arm is attached to hex shaft

  • victor SP lights are what we expect…

  • arm is 35 inches long, weight started at 25 pounds, we’ve stripped down to ~10 pounds, still no change in movement

  • running our numbers through JVN-Design Calc gives Current Draw as 17 A and Stall Load as 97 lbs, does that mean we theoretically shouldn’t stall until we hit 97 pounds?

Where would you focus on troubleshooting? Is it something in the code? We’re new to Java but we’ve gotten all our other subsystems running… Or are we asking too much of the motor?

2

Without seeing the mechanism or the stuff it’s interacting with (elevator?), My best guess is that the lenth of the arm is causing a rather large moment, and thus causing binding. Can you post images?

3

Can you confirm that it’s stalling with how hot the motor is?

the motor just “twitches”

My gut instinct is that this might be related to a battery that’s nearly dead.

victor SP lights are what we expect…

Then it probably isn’t a programming problem. I would confirm that you’re getting expected voltage at the other side of the Victor.

4

If you run the motor free, does it work as expected?

So you need 350 in-lb of torque to lift this arm, and my back of the napkin calcs say you have less than 50. You need to gear down significantly more to move your arm.

5

My gut agrees with this.
I’d suggest at least a 10:1 additional reduction (taking up some inefficiency)

6

I agree with that as well, a 35 in arm takes a lot of torque to move. I suggest gearing down, adding a 10:1 or so (can play around with until you find what works best). If your looking for faster movement with enough torque you could try Andymark’s deCIMate or something similar.