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Abstract: Demands of micro-aspheric glass lenses are increasing in optical devices such as digital cameras and blu-ray players. In this paper, a novel vibration-assisted polishing machine using a magnetostrictive vibrating polisher is proposed and developed to improve the efficiency, surface roughness and stability of finishing. The magnetostrictive vibrating polisher can generate a radius of 30μm circular vibrating motion at frequency 9.2kHz. From the polishing experiments, a smooth removal function was obtained. The form accuracy was improved to less than 100nm P–V and the surface roughness was reduced to 3.3nm Rz (0.4nm Ra). [Copyright &y& Elsevier]

The present paper describes the theoretical analyses, design and experimental verification of a magnetostrictive actuating device, the locomotion of which is inspired by the motion of the smooth impact drive mechanism reported previously by a number of researches of our group. The proposed device is different from the reported device driven by a piezoelectric actuator. The proposed device is actuated by a micro magnetostrictive actuator constructed using an iron-gallium alloy. The proposed magnetostrictive actuating device is an interesting linear-moving mechanism and takes advantage of impact forces coupled with friction forces to achieve a long stroke with fine position resolution. The results of experiments indicate that the maximum speed of the prototype is approximately 1.0 mm/s at a current of 300 mA with a frequency of 4 kHz. [ABSTRACT FROM AUTHOR]

There is strong demand for microactuators in medical and industrial fields. For example, minimally invasive surgery has been progressing, and a series of microactuators useful for positioning, grasping and cutting in a narrow space are required. For this purpose, we are investigating micro magnetostrictive actuators using iron–gallium alloy (Galfenol). Galfenol is an iron-based magnetostrictive material with magnetostriction greater than 200 p.p.m., a high relative permeability μr greater than 100 and a Young's modulus of around 70 GPa. This material is machinable by conventional cutting techniques, and can operate under tensile, bending and impact loads without any degradation in performance. Therefore, a microactuator using Galfenol has advantages over conventional actuators such as electrical motors and piezoelectric actuators in terms of design simplicity, low drive voltage requirements and high robustness. In this paper, we describe two types of actuators consisting of a U-shape core of Galfenol — one providing 1 longitudinal d.o.f. and 2-d.o.f. bending deformation, and the other propelling by a friction drive. These actuators are simple and small, and easily integrated into actuation parts of microrobots. [ABSTRACT FROM AUTHOR]

We propose a two-DOF micro bending actuator using Iron-Gallium alloy (Galfenol). The actuator consists of two parallel beam structures using Galfenol core, square rod of 1-mm² area and 11-mm length with ditches of 0.3-mm width. The beams in the core are wound coils and bonded to an iron end cap to construct close magnetic circuit. The orthogonal parallel beams which the push-pull elongation prebiased by permanent magnets provide bending deformation in two directions, X and Y. The advantages of the actuator are simple and rigid configuration generating high force and the identical first bending resonance frequencies of X, V inherited form the symmetric structure. The displacement, linear round zero current, was observed varied from -15 to 15 µm at both directions. The wobbling motion with amplified displacement around resonance frequencies was also demonstrated. The actuator driven by small power supply will be applicable for cutting or drilling device for, e.g., minimally invasive surgery. [ABSTRACT FROM AUTHOR]

This paper presents a miniature positioning device using Iron-Gallium alloy (Galfenol). Galfenol is a ductile magnetostrictive material with magnetostriction more than 200 ppm, Young's modulus of 70 GPa and high permeability. The actuator consists of a small pin of Galfenol, 1 mm diameter fabricated by ultra high precision cutting, winding coil, housing, and brass mover clamped on a frictional rod. The movement is based on the smooth impact drive mechanism, where the mover frictionally supported is moved step by step by inertia force with the rapid expansion and slow contract of the Galfenol pin. The miniature device driven less than 3 V was verified the velocity of 1 mm/s at driving frequency of 2 kHz with no-traveling limit, which will be applicable for positioning mechanism for mobile electronics. [ABSTRACT FROM AUTHOR]

We propose a stress-based magnetic force control method using the inverse magnetostrictive effect. A basic magnetic circuit consists of iron yokes, permanent magnets, and magnetostrictive material by which compressive stress applied to the material is converted to variations in the magnetic force. The characteristics of the force, such as bias, variation and sensitivity, depend on the inverse magnetostrictive properties of the material. In this paper we investigate the suitability of Galfenol, iron-gallium alloy, which has large permeability and high saturation. Measurements of the relations between stress and strain, flux density, and magnetic force in series and parallel magnetic circuit with a rod of Galfenol or Terfenol-D under compression show the advantages of Galfenol and clarify the design criteria for the magnetic circuit in future applications. [ABSTRACT FROM AUTHOR]

Abstract: Recently, micro-optical lenses are highly required in new fields such as Fresnel lenses for solar panels and Wafer Level Cameras (WLC). The lenses are generally molded by micro ceramic molds. In this paper, a novel vibration-assisted polishing (VAP) method by using a magnetostrictive vibrating polisher is proposed to improve the efficiency and stability of micro-optical mold polishing. The magnetostrictive vibrating polisher is composed of a vibrator and a small polishing tool. The small polishing tool is screwed into the head of the vibrator. The vibrating polisher is fixed on a 5-axis (X, Y, Z, B, C) controlled table via a balancing adjustment mechanism. The vibration characteristics are evaluated and the polisher vibrates in a lateral motion at frequency of 9.2kHz with amplitude of 30μm. The polishing force is controllable within a range of 2–200mN with a resolution of 2mN by the balancing adjustment mechanism. Some fundamental polishing experiments are conducted by using molds made of binderless tungsten carbide; the shape of removal function is acquired and surface roughness is improved from 30nmRz (4nmRa) to 10nmRz (2nmRa). [Copyright &y& Elsevier]

Abstract: In this paper, a novel magnetostrictive vibrator with a unique and integrated design is proposed and developed by using a kind of iron–cobalt alloy (Permendur). Permendur is a giant magnetostrictive material (GMM) with magnetostriction exceeding 70ppm, Young's modulus of 210GPa, high relative permeability and sufficient force for actuation, which shows a good performance as actuator material and has been drawn a lot of attention. The magnetostrictive vibrator has four legs around which the coils are wound. The legs can be pushed (expansion) and pulled (contraction) independently through controlling the input currents of the coils. The actuation principle of the magnetostrictive vibrator is illustrated. The lateral vibrating motion can be generated by using a pair of opposing coils, whereas 2D vibrating motion can be obtained by using two pairs of opposing coils. The finite element analysis (FEA) is adopted to analyze the vibration mode and assist the concrete design of magnetostrictive vibrator. Through some fundamental experiments, the characteristics of the magnetostrictive vibrator are evaluated. For the application, it has been successfully used as a vibrating polisher in the ultra-precision finishing of micro-optic molds. [Copyright &y& Elsevier]

Abstract: We propose a miniature spherical motor using iron–gallium alloy (Galfenol). This motor consists of four rods of Galfenol with square cross-section, a wound coil, a permanent magnet, an iron yoke and a spherical rotor placed on the edge of the rods. The magnetomotive force of the magnet provides bias magnetostriction for the rods and an attractive force that maintains the rotor on the rods. When currents of 180° phase difference flow in pairs of opposing coils, a torque is exerted on the rotor by pushing (expansion) and pulling (contraction) of the rods. Rotation about a single axis is realized by a sawtooth current, such that the rotor rotates with slow expansion and slips at the rapid contraction. The motor can be fabricated at small sizes and driven with a low voltage, suitable for application as a microactuator for rotating the camera and mirror in endoscopes. [Copyright &y& Elsevier]

Abstract: A micro-magnetostrictive vibrator using an iron–gallium alloy (Galfenol) drive element was investigated. Galfenol is an iron-based magnetostrictive material with magnetostrictions greater than 200ppm, a high relative permeability μ r >70 and a Young’s modulus of ∼70GPa. This material is machinable by conventional cutting techniques, and can operate under tensile, bending, and impact loads without degradation in performance. A micro-actuator using Galfenol, therefore, has advantages over a PZT type actuator in design simplicity, low drive voltage requirements, high robustness, and a wide temperature operating range. This paper describes the design, fabrication process, and performance of a micro-vibrator which utilizes either an un-annealed or stress-annealed Galfenol pin as the drive element. A displacement of 1.2μm was observed with a high bandwidth of 30kHz and a high tensile robustness withstanding a suspended weight of 500g (6MPa). The vibrator was also verified to be useful as a speaker which can generate clear sound from the power of a portable music player. [Copyright &y& Elsevier]