[Thad House]

Originally Posted by Nuttyman54

Just to make sure people understand here: Adam's example is valid proof that putting an encoder on an outer wheel axle will not inherently add too much variability to produce reliable autos.

I feel that it's worth adding that this is possible because 254 properly tensions their chains, which means the backlash/slop between the outer wheels and directly driven wheels is minimal. If you're using WCP sliding versablocks, you should be able to tension your chain/belt well enough to make this a viable solution as well.

As an aside, 254 and 971 gave a great talk at Champs 2015 which is recorded on Youtube about Motion Profiling and Control which is super helpful to understand how they get such reliable auto control. Worth looking at.

TLDR; If you have a reasonable tensioning method for your chains (esp sliding bearing blocks) you should be fine putting an encoder on one of the outer wheel axles.

I think think another trick is making sure you put the encoder on the weighted wheels. That way you don't have to worry about chain tension, and the encoder should always be touching the ground, at least in most cases. Another thing some teams do is preload their chains. Instead of pushing your robot forward into its starting position, push it too far forward, and then pull back. This will preload the chains to they are tensioned in the right direction for moving forward, which helps reduce shock loads.