Articulating chassis???

[Jon Stratis]

From page 4, section 8 The Robot:

FRAME PERIMETER – the polygon defined by the outer-most set of exterior vertices on the ROBOT (without the BUMPERS attached) that are within the BUMPER ZONE. To determine the FRAME PERIMETER, wrap a piece of string around the ROBOT at the level of the BUMPER ZONE - the string
describes this polygon.

And <R11>

The FRAME
PERIMETER must be comprised of fixed, non-articulated structural elements of the ROBOT. The FRAME PERIMETER must remain a fixed, unchanging polygon throughout the MATCH.

So a fully articulating chassis is not allowed - it would change the polygon that defines your FRAME PERIMETER whenever it bends.

You could have a suspension system with your wheels to accomplish the same thing, however.