Hardware design for roller conveyor on autonomous mobile robot.
The RollerTop product began as my intern project at Fetch Robotics, where I made a proof-of-concept conveyor accessory for the Freight 100 robot base. There was a lot of interest around a conveyor-type mechanism on a mobile robot because with only one degree-of-freedom, a conveyor mechanism is just about the simplest and cheapest active manipulator aside from Fetch's Cart Connect accessory. The initial design used a conveyor belt and drum roller that was driven by an external planetary gearmotor via a belt drive. The conveyor belt approach introduced a lot of complexity as the belt had to be tensioned and the rollers tapered to prevent the belt from walking off to one side. The tensioning mechanism required machined parts and spherical bearings to allow for misalignment of the shaft, and the overall structure was unnecessarily heavy.
When I began full-time as a mechanical engineer at Fetch, I went back to the drawing board on the concept, completely redesigning the mechanism from the ground up. This design approach, which would eventually become the production accessory, used an industry-standard DC-powered motorized roller connected to slave rollers with Poly-V belts. The design saves a lot of cost compared to the initial conceot by using only 5052 Al sheet metal and no machined parts. Compared to using chain to transmit power between the rollers, Poly-V belts are quieter, lighter, cheaper, cleaner, easier to assemble, and require zero ongoing maintenance.
I designed the system and made fabrication and assembly drawings using SolidWorks.
The RollerTop 100 product debuted in the Fetch booth at the MODEX trade show in April 2018 and has since gone into production and shipped to customers. I also led the development of the FetchLink industrial IoT device in parallel to give the RollerTop a way to communicate with existing stationary conveyors in a customers' workflow.