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Unread 03-12-2012, 19:16
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wireties wireties is offline
Principal Engineer
AKA: Keith Buchanan
FRC #1296 (Full Metal Jackets)
Team Role: Mentor
 
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Re: Balancing an Arm

Quote:
Originally Posted by JVN View Post
The bigger advantage of course is that if you reduce the load your motor needs to lift, you can use a less powerful motor to accomplish the task at the same speed. 148 (and 217) have used a single globe motor as our shoulder joint in years where many other teams are using a CIM or 1 or 2 FP motors...

The weight of the arm is (reasonably) balanced, so the motor just needs to lift the weight of the game object.

-John
And Team 1296 dutifully read the awesome JVN blog and did exactly the same thing! We used surgical tubing to save costs. Our arms worked beautifully - now if we can only make more elegant grippers...

I saw a couple of references to "slowing things down with software" in this thread. In general it is good practice to never ask more (with your software) out of a motor than it can give. Don't design software that asks the motor and the appendage to violate any laws of physics. This is often as simple as adding a trapezoidal velocity profile (or let the PID classes do it for you) or filtering the linear input from the driver station with a cubic function.

HTH
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