Design and Control of a Ballbot Drivetrain with High Agility, Minimal Footprint, and High Payload

TL;DR

This paper introduces a novel ballbot drivetrain design and a robust LQR-PI control strategy that enables high agility, minimal footprint, and high payload capacity, demonstrated through a full-scale prototype and reduced-order testbed.

Contribution

It presents a new ballbot drivetrain with a simple control approach, validated on hardware, achieving high payload and agility with minimal footprint.

Findings

Payload capacity of 60 kg achieved

Maximum speed of 2.3 m/s demonstrated

Effective omnidirectional movement validated

Abstract

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 full-scale ballbot prototype (MiaPURE) was constructed using off-the-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 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.