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This paper presents the design and control of a ballbot drivetrain that aims to achieve high agility, minimal footprint, and high payload capacity while maintaining dynamic stability. Two hardware platforms and analytical models were developed to test design and control methodologies. The fullscale ballbot prototype (MiaPURE) was constructed using offthe- shelf components and designed to have agility, footprint, and balance similar to that of a walking human. The planar inverted pendulum testbed (PIPTB) was developed as a reduced-order testbed for quick validation of system performance. We then proposed a simple yet robust cascaded LQR-PI controller to balance and maneuver the ballbot drivetrain with a heavy payload. This is crucial because the drivetrain is often subject to high stiction due to elastomeric components in the torque transmission system. This controller was first tested in the PIPTB to compare with traditional LQR and cascaded PI-PD controllers, and then implemented in the ballbot drivetrain. The MiaPURE drivetrain was able to carry a payload of 60 kg, achieve a maximum speed of 2.3 m/s, and come to a stop from a speed of 1.4 m/s in 2 seconds in a selected translation direction. Finally, we demonstrated the omnidirectional movement of the ballbot drivetrain in an indoor environment as a payload-carrying robot and a human-riding mobility device. Our experiments demonstrated the feasibility of using the ballbot drivetrain as a universal mobility platform with agile movements, minimal footprint, and high payload capacity using our proposed design and control methodologies. 

A novel wheelchair called PURE ( Personalized Unique Rolling Experience) that uses hands hands-free (HF) torso leanlean-to -steer control has been developed for manual wheelchair users (mWCUs). PURE addresses limitations of current wheelchairs, such as the in ability to use both hands for life experiences instead of propulsion. PURE uses a ball ball-based robot drivetrain to offer a compactcompact, selfself- balancing , omnidirectional mobile device. A custom sensor system convertconverts rider torso motions into direction and speed commands to control PURE, which is especially useful if a rider has minimal torso range of motion. We explored whether PURE’s HF control performed as well as a traditional joystick (JS) human human- robot interface and mWCUsmWCUs, performed as well as able able-bodied users (ABUs). 10 mWCUs and 10 ABUs were trained and tested to drive PURE through courses replicating indoor settingssettings. Each participant adjusted ride sensitivity settings for both HF and JS control . Repeated Repeated-measures MANOVA tests suggested that the number of collisions collisions, completion time time, NASA TLX scores except physical demand , and index of performance performances were similar for HF and JS control and between mWCUs and ABUs for all sections. Th is suggestsuggests that PURE is effective for controlling this new omnidirectional wheelchair by only using torso motion thus leaving both hands to be used for other tasks during propulsion propulsion.