Automatic Brakes for carts and pallet dollies

TL;DR — brakes that are automatically set when robots leave the carts and automatically unset when the robot picks the cart up. Also the humans need to be able to easily and quickly release the brakes to move the carts.

There are several ways this could be done. Here are some examples:

Mimic air brakes on large trucks — springs are used to apply brakes (rubber pads or similar pressing against the wheels of the casters), air is used to release them. An airbag (think of a furniture lifter or blood pressure cuff) between the Kingpin and the Crown could be flattened when engaging with the cart, which would displace air through hoses, which would press back against the springs to release the brakes.

Hydraulic — similar to above (or below), but using mineral oil rather than air.

Cable actuated Mimicing bicycle brakes — spring loaded lever or plunger presses a pad against the wheels. Mechanical lever built into the crown is actuated when the Kingpin is engaged into the cart. The lever pulls on cables to compress the springs, lifting the pads off the wheels to release the brakes. If handles are mounted to the carts then brake levers from bicycles could be used to provide a parallel actuation method for people to release the brakes when needed. Bicycle cables, cable-housings, levers, springs, etc. could be used.

Suspension casters — if the casters were spring loaded slightly, they could provide an assist to the robot to actually lift the cart, instead of just hitching to the cart. When the weight of the cart presses down on the springs then rubber feet contact the floor but with the assistance of the Kingpin lifting up the cart, the rubber feet would be lifted up off the floor and the casters would remain in contact with the floor. This is a very, very problematic solution in trying to make the spring force adjustable so that it works properly with the range of payload weight varying from empty to full, unevenly loaded, etc. Also uneven floors could be problematic. If the springs aren’t damped then oscillations could happen. Carts might tip when going around corners and payloads and CGs could shift…

Mechanical lever actuated feet — lever built into the crown is actuated by kingpin, lever actuates rods, which deploy feet, which contact the ground in parallel to the caster wheels.