Design, Development, and Analysis of a Hemispherical Singularity Drive System for Instantaneously Omnidirectional Motion With Kinematic Isotropy

This paper presents an omnidirectional drive system with instantaneous omnidirectionality and kinematic isotropy, the Hemispherical Singularity Drive (HSD). By driving a hemispherical wheel mounted on a pointing mechanism, a thrust vector can be generated with arbitrary direction and magnitude. The direction of this thrust is determined by the pointing mechanism’s heading and the magnitude is a function of wheel speed and effective wheel radius, which is in turn dictated by the degree of wheel tilt. At “neutral” position, the wheel operates at its singularity point, producing no thrust regardless of wheel speed. This paper presents the design, kinematics, and an approach to the inverse kinematics of a single module. An omnidirectional robot can have one or more of these modules, effecting increased degrees of mobility, and the governing equations for control of a robot with three or more modules are presented.

An Omnidirectional, Direct Singularity Drive System and its Inverse Kinematic Model

This paper presents an omnidirectional drive system. The design presented here involves a spinning hemispherical wheel mounted on a gimbal. The wheel operates at its singularity point when in the “neutral” or static position. As the gimbal is tilted, the wheel provides a thrust vector to the vehicle. The tilt determines the effective radius of the wheel, which in turn determines the amount of power that can be transmitted for motion. The paper presents the design and kinematic and inverse kinematics analysis of a singularity drive mechanism. Vehicles can have single or multiple singularity drive mechanisms to achieve increasing levels of maneuverability. From a control standpoint, each singularity drive is kinematically decoupled from other drives on the same vehicle. Vehicles with one, two and three singularity drive mechanisms are introduced and some experimental results are presented.