[GeeTwo]

Chassis: We built a KOP chassis "long" and modified it into a 5-dualie omni h-drive (4" wheels), probably one CIM per drive train. It's already under 28" wide to make the transport dimensions, but we'll probably cut it down to about 22in so it can drive into the landfill to get the second tote.
Pickup: A rake/contour gauge "hand" picks up totes and containers by the "handles". It's optimized for long-side tote pickups, but capable of lifting a container or pulling totes off the step. Lift will be outside the frame, forklift style, driven by two chains (for stability, not strength). The lift will have a single CIM geared lower than the drives, targeting about 80# lift at 40A. The brake is TBD, but will probably be a pneumatic clamp of some sort and normally slaved to the lift motor control. We plan a "Bottom stacking" strategy, that is, putting a stack atop a single tote. With the KOP chassis and 4" wheels, it stays on the carpet and off of the platform.
Controls: The initial prototype is two joysticks with the Y axes controlling the tank drive trains, one X controlling strafe, and the other the lift. We're planning to program buttons to do some "muscle memory" actions such as line up on a tote, and do a bottom-stack maneuver.
Sensors: KOP camera and a couple of high-resolution rangefinders for navigation, and several limit switches as well as a potentiometer for the lift position. We may also add a current meter to the lift motor, depending on the sampling rate of the PDB meters.
Extras to work on after we get the basic stuff built:
A passive frame at the top of the lift will stabilize tall stacks as we drive.
A skid plate shall protect belts and the strafe wheel in case we run amok and hit a platform.
Autonomous will be selectable between a tote-stack or a simple drive into the auto zone.
A tote-flipper is way on the back burner.
We currently have no debris manipulator; we were planning to have the human players load them into the container, but now we're waiting on an update. As we're already committed to staying on the carpet, we might consider a spoiler to push noodles along the floor rather than run over them.