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Mayfield Robotics developed a household robot toy called Kuri that interacted with people and pets using physical gestures, and documented memories autonomously with a camera and microphone.
Function was asked to develop a mobile base including casters, suspension, drivetrain, and bumper.
Kuri drivetrain and suspension detail
My primary role was developing mechanical subsystems within the base area. The robot could quietly and smoothly traverse household terrain like carpet and flooring thresholds, and detect impacts with its environment. Challenges included a small footprint, high center of mass, tight packaging, low ground clearance, and aggressive cost goals.
Kuri was supported by 2 casters (f & r) and 2 drive wheels (l & r). Each was ramped to aid traversing over bumps.
The treaded wheels were driven by a motor and 2-stage speed reduction that used a timing belt and internal gearing for low noise, high efficiency, and moderate torque at low robot travel speeds.
The suspension swingarm connected the two drivetrain assemblies in a semi-rigid manner, to provide significant lateral tip stability while also allowing some compliance for traversing thresholds at oblique angles.
I tested the success rate of the robot traversing flooring and carpet transitions using a tethered prototype base that simulated the mass, inertia, and behavior of the whole robot.
Results informed my design of the suspension including swingarm torsional stiffness, spring rate, and limit stop configuration.
I also designed a bumper mechanism to detect impacts and determine the impact direction. I tested the bumper's reliability using a PLC to command air cylinders applying calibrated impacts in a randomized sequence.
Results informed my design of springs, bearing surfaces, bumper stiffness, and switch placement.
Drivetrain shaft with injection molded belt pulley and sintered spur gear
I worked with a manufacturer in Taiwan to refine the drivetrain design for high-volume production. They were experts in small, high-precision, low-cost injection molded plastic and sintered brass gears, but were less familiar with belt drives.
I helped the manufacturer develop an assembly process, coordinated prototype builds on site, and solved assembly issues with root cause analysis.
Finally, I supported manufacturing bring-up at 3 factories:
Drivetrain assembly (Taipei, Taiwan) - reviewed FAI for drivetrain, helped with testing procedures and quality control
Injection molded body parts (Dongguan, CN) - reviewed FAI for structural frame and cosmetic body panels
Robot final assembly (Dongguan, CN) - reviewed assembly SOPs, root caused fit issues, developed functional QC procedures
Drivetrain assembly station (Taipei, Taiwan)
Kuri assembly line (Dongguan, CN)
Other Responsibilities:
Performed HALT/HASS testing on head assemblies to assess reliability and risks
Outcomes:
Suspension and drivetrain designs enabled Kuri to traverse all ADA-compliant surfaces
Mayfield shipped 100+ robots to customers before their owner, Bosch, decided to shut down the company for lack of organizational fit
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