球による動力伝達機構を用いたアクティブキャスタの運動解析と機構設計

概要

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This paper presents a new wheel mechanism for the active-caster drive system. The active-caster provides omnidirectional mobility with no using free rolling mechanism. The original active-caster equips with an absolute encoder to detect a wheel orientation and two motors for driving wheel and steering axis independently. A computer system needs to detect an absolute wheel orientation and coordinate velocity components for wheel and steering drive to provide wheel motion in an arbitrary direction. To simplify the wheel control system, a new active-caster mechanism is proposed. A proposed active-caster system includes a ball transmission to distribute a traction velocity to wheel and steering axis mechanically without using an angle sensor or coordinated motor control. In this paper, kinematics of the proposed wheel mechanism is analyzed and mechanical condition for realizing the caster motion is derived. A kinematic model of the proposed active-caster mechanism with a ball transmission is analyzed and a mechanical condition for realizing caster motion is derived. Based on the kinematic model and the mechanical condition, computer simulations of the mechanism are performed. In the simulations, the active-caster shows successful caster motions with no sensor or computer system.