Hideo Adachi

Tactility providing apparatus and manipulating device using the same

A detecting portion outputs a contact state signal in accordance with a contact state with respect to an object to be manipulated. The contact state signal represents at least one of information of a sense of sliding of the detection portion with respect to the object and surface information such as surface roughness of the object. A signal processing section converts the contact state signal from the detecting portion into tactility information corresponding to at least one of the information of the sense of sliding and the surface information. A tactility providing portion is excited in accordance with the tactility information from the signal processing section to generate at least one of a traveling wave corresponding to the information of the sense of sliding and a standing wave corresponding to the surface information. A transmission portion transmits at least one of the traveling wave and the standing wave generated by the tactility providing portion to a finger of an operator.

Simulations of Ferroelectric Characteristics Using a One-Dimensional Lattice Model

Simulations of ferroelectric characteristics have been carried out using a one-dimensional model of polarization reversal in ferroelectrics in which latent nuclei are randomly distributed. Characteristics studied include pulse response, P-e hysteresis loops, differential electric susceptibility versus applied field (dP/de-e curves) and switching current versus applied field (i-e curves) in ferroelectrics. Results of simulations show that P-e hysteresis loops, dP/de-e curves and i-e curves depend on the viscosity which causes the delay in motion of the individual dipole moment, the interaction between neighboring atoms and the applied field.

Preparation of Piezoelectric Thick Films using a Jet Printing System.

Pb(Zr, Ti)O3 piezoelectric thick films were prepared on Pt/Cr/SiO2/Si substrate using an improved jet printing system (JPS). X-ray diffraction (XRD) and scanning electron microscopy (SEM) analysis and measurements of electrical properties, including dielectricity, ferroelectricity and piezoelectricity, were carried out on these films. A very high deposition rate of 3 µm/min and films with thicknesses above 100 µm were obtained without peeling. However, the films prepared in this fashion demonstrate lower piezoelectric behavior than bulk PZT ceramics. The reason for this has been explored using element analysis. Furthermore, we have developed a mask depositing technique as a surface leveling.

Tactile sensor using piezoelectric resonator

A new type of tactile sensor probe head which detects compliance of live tissue has been developed. The sensor consists of a Colpitts circuit including a 1.5 mm/spl times/1.5 mm piezoelectric resonator on a mount 2.4 mm in diameter. This size is small enough to be inserted into the human body. Experimental results show that the oscillating frequency change versus the contact force is related to the object compliance. Especially, the maximum gradient of the oscillating frequency versus contact force curve is able to identify the difference of the compliance. It is possible to measure accurate compliance without setting the contact force constant.

Simulations of Polarization Reversals by a Two-Dimensional Lattice Model

Simulations of step-type and pulse responses have been performed using a two-dimensional lattice model in ferroelectrics in which latent nuclei are randomly distributed. Polarization and current responses under the step-type applied field and the narrow applied pulse field shorter than switching time t sw are described. The critical pulse width t*, for which the system returns to the initial polarization state after the narrow applied pulse field is removed, is obtained, and it is found that the value of t* depends on the applied field and the interaction between neighboring dipole moments

Fabrication of Ultrasonic Transducers with KNbO3 Piezoelectric Single Crystal for Detecting Harmonic Signals

An ultrasonic transducer with a circular aperture has been designed and fabricated for the development of a harmonic imaging system with high sensitivity. The transducer consists of two piezoelectric elements; one is made from Pb(Zr, Ti)O3 (PZT) ceramics for transmitting a finite-amplitude ultrasonic pulse, and the other is made from a KNbO3 (KN) piezoelectric single crystal for receiving second harmonic signals generated in a nonlinear medium. They are arranged coaxially. Using this transducer, acoustic characteristics were measured and the observation of sponge phantom images was performed. Compared with other transducers with PZT and PbTiO3 (PT) ceramics, we have confirmed that higher sensitivity and stronger correlation between the sensitivity and figure-of-merit can be obtained. Additionally, the third harmonic detection has been demonstrated.

Numerical analyses of ferroelectric characteristics for memory use by using a lattice model

The numerical analyses of fundamental ferroelectric characteristics for memory use have been carried out by using a one-dimensional model of polarization reversal in ferroelectrics, in which latent nuclei are distributed randomly. Studied characteristics include pulse response, hysteresis (P-e curves), and switching current versus voltage (i-v curves) in ferroelectrics. Obtained results have been discussed.

Feasibility of low-frequency ultrasound imaging using parametric sound

The penetration depth of high-frequency ultrasound is limited, since the ultrasound at high frequency is much attenuated by medium viscosity. In this study, to resolve this problem, we propose low-frequency ultrasound imaging using parametric sound sources as a low-frequency directive sound. In order to verify the proposed imaging method in water, a ring type transducer with the center hole was used to transmit modulated primary ultrasounds with center frequency of 2.8 MHz, and a hydrophone placed within the hole of transmitter was used to receive chirp-modulated parametric sound echoes with center frequency of 300 kHz and a bandwidth of 400 kHz. After receiving parametric sound echo signals from a target with dimensions of several centimeters, a pulse compression technique was applied to the signals in order to improve the range resolution and signal-to-noise ratio. The obtained B mode images reveal the feasibility of low-frequency ultrasound imaging using compressed parametric sounds.

Cross-coupling Properties of Ultrasonic Phased Array Probe.

The frequency dependence of cross-coupling is described for a phased array probe developed for sector-scanning endoscopic ultrasonic diagnosis. The sweep frequency range is set from 0.5 MHz to 10.5 MHz for a 48-element phased array transducer with a center frequency of 5 MHz. Cross-coupling measurements were carried out on various piezoelectric elements at different positions in the probe. The relationship between the cross-coupling and the position of piezoelectric elements as determined by the measurements shows good agreement with the results of static-mode finite-element method (FEM) calculations.

Feasibility of low-frequency ultrasound imaging using pulse compressed parametric ultrasound

HIGHLIGHTSLow‐frequency ultrasound imaging is realized using parametric ultrasound.Pulse compression improves the signal‐to‐noise ratio of the parametric ultrasound.The obtained range resolution agrees well with the theoretical value.The proposed method enables imaging of overlapping targets. ABSTRACT When using high‐frequency (HF) ultrasound in sonography, attenuation due to the viscosity of the medium limits the available imaging depth, and strong reflection and scattering from hard tissue, such as bone, render biological diagnosis very difficult. In order to resolve these problems, the feasibility of low‐frequency (LF) parametric ultrasound imaging with high directivity was explored in the present study. A pulse compression technique was applied to chirp‐modulated parametric ultrasound waves in the frequency band of 100–500kHz generated from modulated primary ultrasound waves with a center frequency of 2.8MHz in order to improve the signal‐to‐noise ratio (SNR). Low‐frequency ultrasound images of brass rods obtained using pulse compressed parametric ultrasound exhibit accurate target distances, a 3‐mm range resolution, which agrees well with the theoretical value, and an 8‐dB improvement in SNR. Parametric ultrasound imaging with pulse compression makes easy to separate overlapping targets in comparison with HF ultrasound imaging, and indicates the image with brightness independent of distance in comparison with directly radiated LF ultrasound imaging. These results reveal that pulse compressed LF parametric ultrasound is not only a useful method for improving the SNR and providing accurate distance measurements, but also enables imaging of overlapping targets.