Design, Construction, and Evaluation of a Ballbot Driven with a Spherical Induction Motor

Abstract

Ballbots are human-sized, dynamically stable mobile robots that balance on top of a single spherical wheel. They were originally developed to address fundamental problems with locomotion in statically stable mobile robots - statically stable mobile robots must have wide bases and low acceleration to avoid tipping over when moving. This results in slow, clunky, and fat robots. Dynamically stable mobile robots, such as ballbots, avoid this problem by balancing actively. Traditional drive mechanisms for ballbots have been mechanically complex, involving either omniwheels or timing belts and steel rollers. This work details the design, construction, and evaluation of a ballbot driven with a spherical induction motor (SIM). The SIM is extremely mechanically simple, with only the rotor moving with respect to the stators; when used as the drive of a ballbot, it results in a mobile robot with just two moving parts. This work reports both feasibility experimental results for SIMbot (spherical induction motor robot) as well as power efficiency results for SIMbot as compared to the original inverse mouseball drive-based (IMB) ballbot. We show with experimental evidence that SIMbot has comparable performance to the IMB-based ballbot but is, in general, 2-3 times less efficient.