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 design, 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 concept by using only 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 used SolidWorks to design the system and make sheet-metal and cable fabrication drawings and assembly drawings.
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. In paralle, I also led the
development of the FetchLink, a general-purpose industrial IoT device that provides the RollerTop a way to communicate with existing stationary conveyors in a customers' workflow through FetchCore,
Fetch's Cloud Robotics Platform.
The RollerTop product page can be viewed on Fetch Robotics' webpage here.