Abstract
This article presents an active ball joint mechanism (ABENICS) enhanced by interactions of spherical gears. The gear-based joint drives three rotational degrees of freedom (RDoF) without slippage. The capabilities were inspired by the unique interactions between two different innovative gears [the cross spherical gear (CS-gear) and monopole gear (MP-gear)] and the superimposition of those interactions by the CS-gear's quadrature spherical tooth structure. One MP-gear constrains two of the three RDoF of the CS-gear. The driving module which drives the MP-gear converts this “constraint” into a “drive” and drives the CS-gear with two RDoF. The CS-gear orthogonally superimposes the interactions caused by two MP-gears to achieve three RDoF driving forces. The principle was revealed by analyzing an equivalent linkage modeled on the mechanism of ABENICS. The linkage also led to the kinematics and torque equations. The theory and physical characteristics of ABENICS were verified in comprehensive and continuous positioning experiments on manufactured prototypes. The flexibility of the actuator placement was also verified in different configurations of the driving modules. The active ball joint, ABENICS can transmit high torque and reliable positioning in three RDoF without an orientation sensor, which applies to robot joints and orientation control mechanisms.
Highlights
R ESEARCH on multi-degrees of freedom (DoF) mechanisms, actuators, and integrated robot joints has been ongoing, which is motivated by societal expectations
This study proposes a new ABENICS based on spherical gear meshing
The study introduced a cross spherical gear (CS-gear) with a quadrature spherical tooth structure and an monopole gear (MP-gear) with a unique geometry that allows continuous meshing with the CS-gear
Summary
R ESEARCH on multi-DoF mechanisms, actuators, and integrated robot joints has been ongoing, which is motivated by societal expectations. If multiple degrees of freedom (DoF) can be actuated in a single joint, robots will become smaller, less costly, or more functional than conventional robots. Manuscript received July 31, 2020; revised December 23, 2020; accepted February 24, 2021. Date of publication April 26, 2021; date of current version October 1, 2021. This article was recommended for publication by Associate Editor Q. Yim upon evaluation of the reviewers’ comments. Yim upon evaluation of the reviewers’ comments. (Corresponding author: Kazuki Abe.)
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