Iwao Hayashi

Electrostrictive Properties of a PMN Stacked Actuator

This paper reports a precise investigation of the fundamental electrostrictive properties of a Pb(Mg1/3Nb2/3)O3-based ceramic stacked actuator, including the local distribution of the strain induced in the sample, the bias voltage dependence of the effective piezoelectric coefficient, the response speed of the displacement to an applied voltage, and the dependence on pressure and temperature. It was found that an applied voltage deforms the stacked actuator non-uniformly in an arc contour on the driving face. The 7 mm-thick device can generate a displacement up to 8.5 µm under a voltage of 1 kV with a 10 µs response. The maximum generative force reaches 1.7×104 N for a driving area of 3.8 cm2.

Development of a piezoelectric cycloid motor

Abstract Ultrasonic motors have recently been developed which have the advantage over electromagnetic motors that they give high torque at low speed. However, since they are driven by friction between their stator and rotor, they have a problem with wear and, as a result, with the length of useful life. This paper proposes a new piezoelectric cycloid motor, in which the cycloid gear mechanism is used to convert the expansion and contraction of the piezoelectric actuators into the rotational motion of the rotor. Since the motor has no slip motion between its stator and rotor, it is not affected by friction. The fundamental characteristics are theoretically derived, and are examined using a prototype of the motor. The following results are obtained: it rotates steadily and keeps its rotational speed even when the load is increased up to the maximum output torque, 0.014 Nm; the maximum efficiency is 25.5 per cent, which is obtained at 16 rpm within the measuring range of the driving frequency of the motor.

Precision positioning with a rotary-linear motor driven by a pair of 2-D ultrasonic actuators

A new rotary-linear motor is proposed, the spindle of which is driven by a pair of two-dimensional ultrasonic actuators in the axial and rotational directions. A preliminary experiment applying a position feedback control system to a prototype of the motor revealed that a selfinduced voltage of a piezostack reduced the positioning accuracy. An improved control system with a PI controller and an additional RC circuit which compensates the self-induced voltage of a piezostack was proposed and built up. Consequently, step responses with a steady error of 0.007 mm in the axial direction and that of 0.05 degree in rotational direction were achieved.

Grain Size Dependence of Electrostriction in PMN Ceramics

The electrostriction of Pb(Mg1/3Nb2/3)O3-based ceramics is strongly affected in both magnitude and hysteresis by their preparation history. This paper describes the factors determining the electrostrictive response, putting emphasis on the grain size dependence. The electrostrictive strain and the hysteresis decrease mainly with decreasing maximum grain size, even if the average grain size is maintained nearly constant.

A ROTARY LINEAR MOTOR DRIVEN BY A PAIR OF TWO-DIMENSIONAL ULTRASONIC ACTUATORS

There is a need to draw various patterns on the inner wall of a small pipe several millimeters in diameter to develop a precise linear scale. Since the authors have already developed a two-dimensional ultrasonic actuator that can move an object is two orthogonal directions independently, they now offer a rotary linear motor, in which the motor shaft is driven by a pair of two-dimensional ultrasonic actuators. Hence, the motor can rotate and move directly, simultaneously, or independently. Good positioning accuracy was obtained for simultaneous two directional drive by controlling the motor with a proportional control: the steady errors were 1.41° and 0.73 mm in the rotary and linear directions, respectively. However, the positioning accuracy greatly decreased for one-directional drive: the steady errors were 27.5° for rotational motion and 20.3 mm for linear motion. To improve these poor positioning accuracies for the one-directional drive, RC series circuits were connected parallel to the piezoelectric devices of a two-dimensional ultrasonic actuator in order to reduce the interference due to the self-EMF induced by the ultrasonic vibration of one pair of piezoelectric devices on another pair. In addition, proportional control was replaced with proportional and integral control. As the result, the positioning accuracy for one-directional drive has been greatly improved, to 0.05° for rotational motion only and 0.006 mm for linear motion only.

An in-pipe operation microrobot based on the principle of screw-development of a prototype for running in long and bent pipes

Nowadays many types of pipe such as water pipes, drain pipes, and gas pipes, are underground. Also many types of pipeline are used in places where people cannot enter, such as atomic power plants and chemical plants. Maintenance of these pipes and pipelines is an important issue to keep our social life safe and comfortable. Some maintenance robots have already been developed; but all of these maintenance robots are used for pipes of medium or large sizes. No maintenance robots, which are used for pipes of small size with inner diameter of one inch or less, have been developed. The authors have thus been trying to develop a screw-principle microrobot, which can run in a small pipe one inch in diameter and can inspect the inner wall with a CCD camera. In this paper the screw-principle microrobot has been improved for running in a small pipe which is 20 m in length or longer and have some bends. Also the running performance has been experimentally investigated.

The Estimation of the Sound Power Radiating from a Peripherally Fixed Rectangular Plate Subjected to Acoustic Excitation (2nd Report, Estimation and Experiment in Case the Plate is Excited in Diffused Sound Field)

This paper describes the estimation method of the sound power radiating from a four side fixed rectangular plate acoustically excited in a diffused sound field. First, the forced vibration of the plate excited by a plane wave in a free sound field has been solved. In the calculation, the distribution of the plane angles of modal exciting forces is taken into consideration precisely. Next, the stochastic model composed of random plane wave elements is assumed on the diffused sound field. The modal exciting forces and the forced vibration displacement are derived based on the ergodic process. Using the obtained forces and displacement, the equations for calculating the frequency spectra of the parameters for estimation are derived. The estimated frequency responses of radiating sound power coincided well with the measured values.

Real-time measurement of in-plane vibration by double-aperture laser speckle interferometry

This paper describes the real-time measurement of in-plane vibration using an improved double-aperture laser speckle interferometer. To detect the in-plane vibration in real- time, a new signal processing system which can detect the phase angle of the frequency component of the interference fringes in real-time by calculating Fourier coefficients is proposed. The proposed real-time signal processing system is composed of a pulse generator, a sin/cos generator and an A/D converter controlled by a personal computer, and of an analog electronic circuit made of analog ICs. The linearity of the output signal of the prototype due to a number of the detected fringes and noises is experimentally examined. In- plane static displacement and vibration displacements of a specimen driven by a piezostack are measured with a new laser speckle interferometer equipped with the proposed signal processing system and are calibrated with a gap sensor. The measured static in-plane displacements varied in proportion to the given displacement with reproductive error variation with the maximum value of 0.5 micrometers . The vibration displacements measured with the laser speckle interferometer were detected with the maximum sampling frequency of 470Hz. This new laser speckle interferometer thus achieved the measurement of in-plane vibration in real-time.

Modal analysis of a circular plate with a solid shaft and a solid cylinder and estimation of radiating sound power

The natural modes of flexural vibration of a circular plate with a solid shaft and a solid cylinder, which is a simple model of aircraft gears, were theoretically analyzed with a new method proposed by the authors. The calculated natural frequencies and mode shapes coincided well with the values measured by experimental modal analysis. Using the calculated natural frequencies and mode shapes, the three parameters required for the estimation of radiating sound power—total loss factor, radiation loss factor, and driving point mobility—were calculated, and then the radiating sound power from the circular plate was estimated by the estimation theory proposed by the authors in other papers. The frequency response of the estimated sound power coincided well with the values measured by the sound intensity method.

Optimum Motion Control of a Redundant Robot with the Objective Function of Dexterity.

This paper describes an optimum motion control method for robot serial manipulators with multiple redundant degrees-of-freedom. The manipulability measure, which is given using the Jacobian matrix for both the position and posture of the endeffector of a serial manipulator, is proposed as the index for evaluating dexterity, and the manipulator is defined most dexterous when the manipulability measure has a maximum value. To drive serial manipulators most dexterously, two new methods, namely the optimum CP control methods with and without consideration of the posture angle of the endeffector, were proposed and experimentally studied for redundant planar 3R, 4 R and 5 R manipulators. Consequently, the optimum CP control method with consideration of the posture angle of the endeffector gave a better result : the manipulators were driven most dexterously over almost the entire driving range and high response was obtained.