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This paper presents a project that aims at fabricating a biologically inspired robotic fish. The robotic fish is designed to be capable of propelling itself through oscillations of a flexible caudal fin, like a real underwater fish. In this paper, we describe the design features that underlie the operation of the robotic fish. These features include a unique actuator referred to as electrostatic film motor and a light and flexible power transmission system. The electrostatic film motor is made of two pieces of flexible printed circuit film and can be utilized as a new-type artificial muscle. The power transmission system permits reciprocating power to be converted to periodic oscillations and distributed to the caudal fin. Based on several design considerations inspired by biological concepts, we propose several open-loop swimming control strategies for the constructed robotic fish to accomplish fish-like motion (i.e., cruising, turning, and diving). Experiments of Seidengyo I, the first prototype of our electrostatic fish family, are carried out to confirm the validity of the original design and control. We further design Seidengyo II to improve on Seidengyo I and show the results of the experiments. Index Terms--Artificial muscle, biomimetic robotic fish, electrostatic film motor, fish-like swimming, open-loop control.

We present a zero-power magnetic levitation technique using a composite of magnetostrictive and piezoelectric materials. The composite is bonded to iron yokes with an attached permanent magnet, by which the magnetic force exerted on movable yoke via air gap is controlled by the applied voltage on the piezoelectric material. The magnetic force control is based on the inverse magnetostrictive effect of the magnetostrictive material, i.e., the magnetization is varied with mechanical stress. The advantage of the composite is zero power consumption, because no current flows in static operation as a result of the capacitive property of the piezoelectric material. This feature will be useful in high-precision stage or conveyor systems using magnetic levitation where heat generation and power consumption should be avoided. The zero power characteristic of the composite is valid at any reference gap or load, whereas that of the conventional electromagnetic type is valid only at the equilibrium gap. We performed two levitation experiments: one using the composite to demonstrate the zero power advantage, and the other combining the composite to adjust the bias gap and electromagnet to stabilize the motion of the levitated yoke. The composite driven by a small dc-dc converter successfully varied the gap and maintained it constant with zero power consumption. Index Terms--Magnetic levitation, magnetostrictive material, piezoelectric material, zero-power.

A ferromagnetic material can be levitated by the pinning effect of a field-cooled superconductor. This paper presents two methods for modeling this effect: 1) an approximate calculation to determine the relationship between attractive force and air gap at both room temperature and superconductive temperature (77 K) and 2) a novel way of modeling the pinning effect by a finite-element method (FEM). A comparison of analytical and FEM results with experimental results verifies the validity of the methods. The methods can be used to estimate the system's behavior when the cylindrical yoke is replaced by a ring yoke. The stiffness of the system will increase by 70% (to 5.3 N/mm) when a ring yoke with the same surface area is used instead of a cylindrical yoke. Index Terms--Analytical model, field-cooled high temperature superconductor, finite-element method (FEM), Maxwell theory, numerical modeling, pinning effect, shape effect.

We assemble a composite of giant magnetostrictive material (Terfenol-D) and stack piezoelectric transducer (PZT) actuator, and use it in a linear step motor. Control of the magnetic force exploits the inverse magnetostrictive effect of the Terfenol, in which the composite and a magnetic circuit in combination controls the magnetic force on a movable yoke with the voltage of the PZTs via mechanical stress. The unique feature of this arrangement is zero power consumption needed to maintain a constant magnetic force; once the PZTs have been charged, no current flows in static operation due to the capacitive property. A composite having simple configuration, bonding both Terfenol and PZT to iron yokes, is verified to control the magnetic force over wide variations under appropriate prestress conditions. A linear step motor with four composites as a stator also demonstrates variation of the thrust force and the possibility of motion control. Microstep motion of the mover was achieved using sinusoidal voltage, and zero current was observed with stationary voltage. The principle should be advantageous in high-precision positioning. Index Terms--Composite, linear step motor, magnetostrictive material, piezoelectric material, zero-power.

This paper reports the continuation of the authors' work in the field of linear and rotary submicrometric positioning using electrostatic glass motors. Electrostatic glass motors, a recent development where a glass rotor, once polarized using a static electrostatic field, is synchronously following a moving electrostatic field, have been described previously. The potential application to precise positioning was proven feasible and promising. The present report describes a fully operational rotary prototype, featuring remarkable performance. It will be shown that sub-arc-second positioning is possible in open-loop operation, over an infinite operation range, and over a very broad speed range. After a brief recapitulation of the propulsion principle, the realized system will be presented and characterized, its performance experimentally determined, and discussed. Finally, potential industrial applications of the electrostatic glass motor will be proposed. Index Terms--Electrostatic glass motors, electrostatic induction, linear nanometric positioning, rotary sub-arc-second positioning.

We propose a magnetic force control device consisting of laminate composites of magnetostrictive material and piezoelectric material. The magnetic force control is based on energy conversion in the composite, such that the variation of magnetization of the magnetostrictive material induced by the piezoelectric material is converted to the variation of magnetic force by magnetic circuits. Because of the capacitive property of the piezoelectric material, the device requires little current in order to maintain control of a constant force. The laminate composite can be fabricated easily and in small sizes. In this paper, we report the magnetic force control properties of a composite of Terfenol-D and piezoelectric material plates (PZTs) and discuss the design of the laminate composite. Our theoretical magnetic force formulation derived by an equivalent magnetic analysis and finite-element analysis of strain distribution in the Terfenol-D, and measurements with various thicknesses of PZT demonstrated that there are appropriate thicknesses to provide large variation of the magnetic force and energy conversion efficiency. Stacking the composites was found effective for increasing the effective area of the Terfenol-D. Index Terms--Laminate composite, magnetic force, magnetostrictive material, piezoelectric material.

We investigate the dynamic response of a magnetic force control device composed of a laminate composite of magnetostrictive/piezoelectric material. The device exploits the inverse magnetostrictive effect of a magnetostrictive material so that the variation in the magnetization of the material, and hence the magnetic force in a magnetic circuit, can be controlled with a voltage to the piezoelectric material. Here, we compare the voltage-induced frequency responses of the admittance and flux (magnetic force) between the new device and a conventional electromagnet in order to identify the factors that degrade the response of the device. A finite-element calculation of the modal shape of the composite supports the observed correlation between the vibration of the composite and the flux in the gap in dynamic response. Index Terms--Giant magnetostrictive material, laminate composite, magnetic force, piezoelectric material.

The piezoelectric actuator (PA) has been used for precision positioning from micrometer down to nanometer scale. In this paper, a spring-mounted PA is designed to achieve a high accuracy and self-moving ability in precision positioning motion. The contact force between the hammer and the self-moving stage, and the friction force of Leuven's model caused between the grinded groove and the self-moving stage are considered. The governing equations of the system are formulated by using the finite-element method (FEM). The numerical solutions are provided to compare with the experimental results, and demonstrate the well agreement of the present theoretical formulations.

A smooth impact rotation motor has been operated with a torsional piezo actuator. Revolution direction is reversible, maximum output torque was 56 gfcm, and maximum revolution speed was 27 rpm.

A dynamic simulation model for a surface acoustic wave (SAW) motor employing spherical-shaped sliders is presented. The transient response of the motor speed was simulated. The relationships between frictional factor and time constant and vibration velocity of the stator and the slider speed were elucidated. The levitation and contact condition was verified and the velocity saturation mechanism was clarified.

A probe sensor to be used for high precision coordinate measuring machines, surface roughness measuring tools or scanning probe microscopes (SPM) was constructed. The sensor is composed of a rod vibrating in the axial direction. The longitudinal vibration was excited and also detected by PZT thin film. The PZT thin film was made using a hydrothermal technique. The hydrothermal technique utilizes the reaction process in hot and high pressure aqueous solutions.

Devices for handling microparticles using an ac electric field are proposed and experimentally validated. With the application of balanced multiphase high voltages in the 0.2k-[Vp-p]-2-k[V.sub.p-p] range to a series of encased parallel electrodes with a typical center-to-center pitch width of 400 [[micro]meter], particles on a thin protecting and insulating film become charged and are conveyed by the created traveling field. Devices with various novel transportation and manipulation features, utilizing multiphase ac electric fields that instantly generate particle driving forces, have been designed and produced. Their features include newly developed methods for particle conveyance smoothing, grouping, and sorting, as well as two-dimensional handling. Traced particle conveyance characteristics have been studied under application of three- and six-phase voltages with three different voltage wave profiles and also in diverse environments. Various particle materials with a 5-400-[[micro]meter]-diameter range have been experimentally examined; Fe, Al, glass, and plastic spheres showed the best performances. Index Terms - Charge, devices, electrostatic, microhandling, particles.

This paper reports the successful electrostatic suspension of dielectric materials. In order to implement a stable suspension, the electrostatic forces exerted on a dielectric are actively controlled on the basis of the measured suspension gap lengths. The principle of electrostatic force generation for dielectrics is different from that for conductors. By utilizing a stator electrode pattern containing many boundaries over which potential differences exist, the suspension characteristics, such as dynamic stability, suspension initiation time, and stiffness of lateral motion are greatly improved. The dynamic model of the suspension system and the influence of the resistivity of a dielectric on the closed-loop stability will be described, followed by the experimental apparatus and stabilizing controller. As dielectric objects, glass plates have been suspended electrostatically at a gap length of about 0.3 mm. Apart from the structure of the stator electrode, the suspension initiation time is also influenced by air humidity, glass type, supplied voltage, and gap length, which have been experimentally explored. Experimental results on the lateral dynamic characteristics will be presented, as well. Index Terms - Dielectrics suspension, electrostatic device, electrostatic forces, electrostatic induction, electrostatic suspension.

The possibility of high frequency ultrasonic motors have been demonstrated using high frequency vibrations over 1 MHz. However the use of fluid coupling to transmit the actuation force means that the operational force is tiny. The operation of the friction drive surface acoustic wave motor has been demonstrated at 10 MHz and 20 MHz. Contact conditions between slider and stator are important as squeezed air film can disturb the friction drive. The surface acoustic wave (SAW) transducer is useful as a miniaturized actuator due to its high power density.

Improvements to a micro ultrasonic motor based on PZT thin film have been made using a single process hydrothermal method. The lower distribution of chemical components of the PZT film leads to higher efficiency of the stator transducer. The piezoelectric factor d31 was -30 pC/N and the output torque was 7.0 muNm, with maximum revolution speed of 880 rpm at 15 Vp-p driving voltage.

A design for a transducer for an ultrasonic motor has been proposed, based on two sandwich-type vibrators. There are two vibration modes, symmetrical and anti-symmetric. The transducer tip direction motion is excited by the symmetrical mode, while the lateral motion is excited by the anti-symmetrical mode. The vibration modes are degenerated. Heat treated high strength chromium manganaese steel bolts were used to bind the PZT elements.

A new type of contactless wafer manipulator, featuring 'direct electrostatic levitation and propulsion of silicon wafer (DELP-SW),' has been successfully developed. The novel aspect of this manipulator is that a silicon wafer can be directly levitated and driven via electrostatic forces. In this paper, a brief review of basic principles is presented. This is followed by a description of the structure of a prototype DELP-SW mechanism, including electrode design, position feedback control method, driving principle, and the operational procedure. Experimental results, which demonstrate completely contactless transportation of an 8-in silicon wafer, are also presented. Index Terms - Electrostatic forces, levitation, noncontact manipulation, propulsion, silicon wafers.