Intial calibration of a robotic arm

[dizzync]

We are designing an arm with three joints that move in a 2D plane. Neither of the joints can pass over each other. My question is what is the best method to set an initial zero degree offset? From this offset, the arm's position is then calibrated over a known location. The arm must be able to locate to a defined position with no more than a 0.10 inch error. From past experiences, limit switches and hard stops have not been given us the desired accuracy.

 

[IRstuff]

Assuming a 30 inch arm, 0.1 inch positioning error means 3 milliradian or 0.2 degree angle error. You'll need optical encoder or resolver to meet this requirement

TTFN

 

[dizzync]

The resolvers that we have dealt with in the past have not been consistant in the their counts from resolver to resolver and from changes in power states. Currently we are using encoders for position determination. We are looking for a method to tell the encoder, very accurately, that a certain encoder count is zero degrees.

 

[IRstuff]

The angle offset, if you can't get rid of it in the assembly of the arm, would need to be calibrated and removed in the controller.

TTFN