Design and development of a miniature multi-degree-of-freedom in-plane motor using iron-gallium alloy

This paper presents the design and development of a novel miniature multi-degree-of-freedom motor capable of achieving a 3-DOF in-plane motion. The proposed motor employs the impact drive mechanism that comprises the friction and the inertia force to achieve the self-propelling motion. The motor consists of two U-shape driving elements made of iron-gallium alloy (Galfenol) that is distinguished by its outstanding mechanical property. Meanwhile, the magnetomotive force of a permanent magnet is used not only to increase the friction between the motor and the steel substrate, but also to provide a bias magnetic field within Galfenol. This bias magnetic field enables the motor to generate a swing motion. Although Galfenol has a relatively small strain output compared to other smart materials, the swing motion amplifies the displacement of the inertia mass, which leads to an enlarged inertia force. Two modes of driving current are used to achieve the consistent linear motion and rotation, respectively. The experiment result shows that the new motor can achieve a maximum linear motion velocity of 4.03 mm/s and a maximum angular velocity is 15.9°/s. An in-plane motion test shows that the motor is able to track a rectangular trajectory.