Chang-Hwan Lee

Design and characteristic analysis of L1B4 ultrasonic motor considering contact mechanism

Up to the present time, the analysis and design of ultrasonic motors (USMs) have been performed using rough analytic methods or commercial analysis tools without considering the complex contact mechanisms. As a result, it was impossible to achieve an exact analysis and design of a USM. In order to address the problem, we proposed the analysis and design methodology of an L1B4 USM using a three-dimensional finite element method combined with an analytic method that considers complex contact mechanisms in linear operation. This methodology is applicable to many other kinds of USMs which use resonance modes and contact mechanisms. Also, we designed and prototyped the mechanical system and driving circuit of the L1B4 USM, and finally validated the proposed analysis and design methodology by comparing their outcomes with experimental data.

Identification of material constants for piezoelectric transformers by three-dimensional, finite-element method and a design-sensitivity method

In this paper, an inversion scheme for piezoelectric constants of piezoelectric transformers is proposed. The impedance of piezoelectric transducers is calculated using a three-dimensional finite element method. The validity of this is confirmed experimentally. The effects of material coefficients on piezoelectric transformers are investigated numerically. Six material coefficient variables for piezoelectric transformers were selected, and a design sensitivity method was adopted as an inversion scheme. The validity of the proposed method was confirmed by step-up ratio calculations. The proposed method is applied to the analysis of a sample piezoelectric transformer, and its resonance characteristics are obtained by numerically combined equivalent circuit method.

Nonlinear analysis of the three-phase transformer considering the anisotropy with voltage source

In this paper, the Newton-Raphson method, using two-directional (anisotropic) material properties, is applied to the analysis of a three-phase transformer. A new two-dimensional (2-D) model that reflects three-dimensional manufacturing effects, such as air-gap and overlapped stacking, is proposed. These effects cannot be dealt with by conventional 2-D methods. In addition, the new method obtains the current waveform phase difference with respect to the voltage source waveform. The analysis is performed by a finite-element method in which a voltage source is included, and its validity is confirmed experimentally.

Analytic and numerical approaches for characteristic analysis of linear ultrasonic motor

This paper presents analytic and numerical analysis of ultrasonic motors (USM), especially the linear motion ultrasonic machine. For rough estimation of characteristics of a linear ultrasonic motor, the analytical method is used and a three-dimensional numerical analysis with experimental material data using ABAQUS, is performed. The contact problem is included as well. The validity of analysis is confirmed by comparing experimental results with numerical ones.

Two-dimensional analysis of three-phase transformer with load variation considering anisotropy and overlapped stacking

The design of a transformer should consider the analysis of the load variation. This paper describes the current wave calculation when the load condition varies for the newly proposed two-dimensional model in previous work, which can reflect the three-dimensional effects such as air gap and overlapped stacking. The analysis includes the Newton-Raphson method, considering two-directional (anisotropic) material properties. The methods are applied to the analysis of a three-phase transformer under load variations by using the finite element method with voltage source. The validity of the method is confirmed through the comparison between the numerical results and the experimental ones under no-load condition.

Analysis of piezoelectric transformer by using finite element method and equivalent-circuit considering load variation

The three-dimensional finite element analysis for piezoelectric transformers is presented. Numerically combined equivalent-circuit method for consideration of load variation, is proposed. The three-dimensional finite element routine in this paper is confirmed experimentally by analyzing piezoelectric transducer. Using results from finite element analysis of piezoelectric transformer, equivalent-circuit parameters of piezoelectric transformer are obtained. The method to calculate loss parameter of piezoelectric transformer is proposed. Characteristics of piezoelectric transformer due to load variation are analyzed. The validity of the proposed method is confirmed by loss calculations.

Analysis of a nanopositioning actuator using numerical and analytic methods

In this paper, we report on our study of a nanopositioning actuator (NPA), which uses an impact/inchworm mechanism. Various kinds of similar precise positioning actuators, which use the same working mechanism, have been proposed by many researchers for several decades. However, characteristic analysis and design methods for the NPA have not been proposed yet. Moreover, the characteristic analysis and design methods for similar actuators were approximate and inefficient. Hence, this paper presents an analysis method for the NPA, which is based on a combination of numerical and analytic methods, shedding light on the complex working mechanism and taking significant factors in the analysis into consideration for an exact and efficient characteristic analysis of the NPA and similar machines. In the present study, the mechanical and electrical systems of the NPA were prototyped. Finally, the effectiveness of the NPA, the feasibility of the clarified complex working mechanism, and the adequacy of the proposed analysis method were verified by experiments.

Analysis of ultrasonic linear motor by using finite element method and equivalent circuit

In this paper, the three-dimensional finite element method and construction of an equivalent-circuit for the linear ultrasonic motor, is presented. The validity of the three-dimensional finite element routine in this paper is experimentally confirmed by analyzing the impedance of a piezoelectric transducer. Using this confirmed finite element routine, the impedance and vibration mode of a linear ultrasonic motor are calculated. Elliptical motion of the contact point between vibrator and rail of a linear ultrasonic motor is shown for determination of the contact point. Using the finite element method and analytic equations, characteristics of linear ultrasonic motor, such as thrust force, speed, losses, power and efficiency, are calculated. And the results are confirmed by experiment. Finally, equivalent circuit parameters of the linear ultrasonic motor are obtained by three-dimensional finite element method and analytic equations.

Inversion of piezoelectric material coefficients by using finite element method with Asymptotic Waveform Evaluation

In this paper, a fast inversion scheme for piezoelectric constants of piezoelectric transformer is proposed. The effects of material coefficients on piezoelectric transformers are investigated by using three-dimensional finite element method (FEM) which is confirmed experimentally. A design sensitivity method adopted as an inversion scheme and Asymptotic Waveform Evaluation (AWE) is used for fast frequency sweep.

Analysis of the three-phase transformer considering the nonlinear and anisotropic properties using the transmission line modeling method and FEM

The transmission line modeling (TLM) method applied to the nonlinear finite element analysis yields a great reduction of calculation time. This method, however, has a shortcoming that the anisotropic property of a material cannot be considered. In this paper, a novel topology using TLM method which can consider both nonlinearity and anisotropy is developed. This new algorithm is applied to the analysis of a three-phase transformer considering both nonlinear and anisotropic properties.