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This brief proposes a frequency synchronization method for a full-digital self-oscillating pulsewidth modulation (PWM) signal generator. The self-oscillating PWM signal generator (PSG) generates a variable switching frequency, which results in poor drive performance for a three-phase power inverter or converter. The proposed frequency synchronization method utilizes an additional carrier signal, such as a triangular wave, to fix the switching frequency of a self-oscillating PSG. The switching frequency is synchronized by the triangular wave. As a test case, a switching frequency of 312.5 kHz is used for a performance evaluation of the proposed PSG with a sampling frequency of 12.5 MHz. A first-order noise-shaped output has been obtained. A high-precision PWM signal with low distortion and high resolution of the effective duty cycle has been achieved within the bandwidth. The proposed synchronized self-oscillating PSG is implemented in a three-phase brushless dc motor driver system to confirm the three-phase synchronization performance. Undesirable ripple current from asynchronous operation was not observed. The switching frequencies were synchronized among the three phases. [ABSTRACT FROM PUBLISHER]

This paper describes the air film characteristic in the interface between the slider and stator substrate of a surface acoustic wave (SAW) motor, and the difference of the squeeze film effect by the form of the slider. Because the vibration amplitude of the SAW motor is several 10 nm order, analysis of pressure was performed by using the molecular gas-film lubrication (MGL) equation. In the analysis, the MGL equation was split into advection phase and nonadvection phase, and calculation of advection and nonadvection phases was performed by using the cubic interpolated propagation (CIP) method and the finite difference method, respectively. From analysis results it was found that the time to steady pressure of air film depends on the radius of projection arranged on the contact surface of the slider. Also found was that the steady pressure in the interface does not depend on the radius and height of the projection, but it depends on the minimum spacing between the slider and the stator substrate. [ABSTRACT FROM AUTHOR]

The contact states of the slider and stator substrate greatly affect the drive performance of a surface acoustic wave motor. The contact states are determined by factors such as the friction coefficient, vibration amplitude, rigidity of the contact surface, contact time with the Rayleigh wave, and slider speed. A model was proposed that represented the relationship between these factors and the drive performance. However, guidance has not been provided on how these values should be changed to improve the drive performance. In this research, we use a friction drive model we proposed to analyze the effect of the changes in these parameters on the drive performance and to discuss the motor design and the drive conditions based on evaluations from the perspectives of the drive power, output, and efficiency. [ABSTRACT FROM AUTHOR]

In order to attempt performance improvement of a surface acoustic wave motor, it is necessary to understand the contact condition between the stator substrate and the slider and to determine the relationship between the basic performance and the physical parameters. In this research, a simulation model taking into account the tangential rigidity on the stator substrate surface is proposed. The effects of parameters such as the friction coefficient, amplitude, and rigidity on the driving performance are elucidated. The validity of the proposed model is demonstrated by a comparison with the experimental results. In addition, detailed calculations are carried out, including determination of the normal position change of the slider by means of the simulation model. © 2003 Wiley Periodicals, Inc. Electron Comm Jpn Pt 3, 87(2): 54–66, 2004; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/ecjc.10098 [ABSTRACT FROM AUTHOR]

It is important to improve efficiency of surface acoustic wave motors in order to achieve their commercialization. In the present research, the energy of the surface wave, which has previously not been used effectively for driving the slider, but been consumed in sound-absorbing materials, is now circulated by two techniques, so that the surface wave is excited efficiently. Trial fabrication of surface acoustic wave motors using the energy circulation methods is carried out. It is confirmed that the traveling wave can actually be excited. In addition, the effectiveness of the energy circulation method is demonstrated by comparison of the driving performance with that in the absence of energy circulation methods. © 2003 Wiley Periodicals, Inc. Electron Comm Jpn Pt 3, 87(2): 10–19, 2004; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/ecjc.10132 [ABSTRACT FROM AUTHOR]

High resolution (from nanometer to subnanometer) stepping drives of a surface acoustic wave motor are presented. It was shown that step displacement was easily controlled by adjusting a number of driving waves, using a steel ball slider equipped with permanent magnet for preload. By means of this open loop control, the step displacement was controlled from centimeter-order to submicrometer-order. In this paper, using a silicon slider equipped with a ball bearing linear guide, the stepping motions of a surface acoustic wave motor were investigated. A laser interferometer equipped with a 2-picometer resolution displacement demodulator was introduced. Motions of the slider ranging from several hundreds of nanometers to several nanometers in each step displacement were observed. Reduction of the driving waves down to 25 cycles, under a 100 V[sub peak] driving voltage and a 30 N preload condition, generated about 2 nm stepping motion using our experimental setup under an open loop condition. We also demonstrated subnanometer step movements. These experimental results indicated that the surface acoustic wave motor has an ability of subnanometer positioning with a centimeterlevel stroke. [ABSTRACT FROM AUTHOR]

Presents a study which proposed a simulation model for the operation of a surface acoustic wave (SAW) motor using spherical-shaped sliders. Summary of experimental results of the SAW motor; Difference between the SAW motor and the usual ultrasonic motor; Simulation results; Conclusion.

Examines the optimum preload pressing force, for a slider to obtain superior operation conditions in a surface acoustic wave motor. Transient response of the slider in a short time drive; Description of the threshold and steady speed; Output force of the friction drive.

Acoustic underwater propulsion systems based on bulk acoustic waves and surface acoustic waves have been studied. In this study, an acoustic propulsion system that consists of a 2.065-MHz thickness-vibration-mode lead-zirconate-titanate ultrasonic transducer is evaluated. A prototype swimmer is designed and fabricated. The admittance difference of the transducer in water and air is investigated. The vibration amplitude of the transducer is measured to evaluate transducer performance. The acoustic radiation force is calculated to describe acoustic propulsion. The zero-speed propulsion (ZSP) force and no-load speed (NLS) are measured in water. Swimmer movement starts at a NLS of 6.1 mm/s and a ZSP force of 0.2 mN for an input voltage and input power of 12.4 V peak to peak and 0.4 W, respectively. Although the average efficiency of the acoustic propulsion system is 69% in water, the overall movement efficiency of the swimmer is less than 1% because of fluid resistance and wire traction. Based on admittance, acoustic propulsion calculations, ZSP force, NLS measurements, and efficiency analysis, an evaluation method is proposed for optimizing swimmers with an acoustic underwater propulsion system. Small size, high power density, and simple structure of an acoustic propulsion system with an ultrasonic transducer make such systems suitable for applications such as pipeline inspection and repair. [ABSTRACT FROM AUTHOR]

Needle-type hydrophones with taper shaped titanium (Ti) wire were fabricated in order to avoid back echo reflected at the end of Ti wire. We will report the manufacturing process and measured results of their performance in this paper. The fabricated hydrophones with normal straight Ti wire have back echo from the end of Ti wire. On the contrary, it was confirmed that back echo was suppressed in the fabricated hydrophone with taper-shaped Ti wire. Furthermore, we expected that the frequency characteristics of receiving sensitivity with large peaks and dips were improved using taper-shaped Ti wire. Generally, flat frequency characteristics without peaks and dips are desired in hydrophones. However, flat frequency characteristics cannot be observed for the conventional-type hydrophone with normal straight Ti wire. Obvious improvement in the frequency characteristics was not observed in the case of using taper-shaped Ti wire. [ABSTRACT FROM AUTHOR]

A physical analysis model of a surface acoustic wave (SAW) motor that is driven by frictional force resulting in nanometer elastic vibration has been proposed. In the case of the SAW motor, the vibration amplitude is from 3 to 30 nm at most. The vibration amplitude is almost the same as that of elastic deformation caused by the preload between a slider and a stator. In the analysis model, the elastic deformation, stick, and slip were considered. Numerical simulation was carried out successfully. Experimental results for the SAW motor at 9.6 MHz operation frequency were compared with simulation results. It was observed that a smaller projection slider with many projections has a high contact surface stiffness, thus, superior performances are obtained in terms of speed and thrust. [ABSTRACT FROM AUTHOR]

•The reaction force of acoustic radiation force (ARF) to solid in liquid is defined as acoustic radiation propulsion (ARP). •To challenge the swimmer locomotion in the circulatory system, acoustic radiation propulsion(ARP) with surface acoustic wave (SAW) is proposed in this study. •To investigate the swimmer propulsion system with ARP, The IDT actuator and prototype swimmer are designed to make a self-propelled motion in water. •The ARP with SAW can be analyzed by the ARF calculation. A zero speed propulsion of swimmer is measured with a force gauge to match the ARP calculation. This study is based on the conventional dimension of U-IDT actuator to discuss the feasibility of swimmer propulsion system with surface acoustic wave (SAW). Acoustic radiation force with SAW has been widely used in the field of microfluidics. Acoustic radiation propulsion (ARP), a reaction force of acoustic radiation force (ARF), has rarely been discussed. This reaction phenomenon may actually play a significant role in the swimmer propulsion system. To investigate this phenomenon, a prototype swimmer is designed in this study. The swimmer converts ARP with SAW into movement and force in water. Rayleigh Wave is excited with a 128° Y-rotated X-propagation lithium niobate U-IDT actuator. The evidence of movement and propulsion are confirmed in water by the no load speed and zero speed propulsion measurements. ARP, based on acoustic impedance difference, can shift the gravity center of prototype swimmer every time. At 9.61 MHz, 100 mm/s no load speed and 4 mN zero speed propulsion are measured in water, when driving voltage is around 75 V 0p. ARF with U-IDT actuator is estimated by the time average. The comparison between the calculation and measurement results had a similar response. In future, miniaturization and low voltage of ultrasonic actuator can be achieved with higher frequencies. Simultaneously, high power density will be maintained because the vibration velocity is not varied extremely. Moreover, wave vibration with ARP may maintain blood activation to reduce the possibility of thrombosis during and after surgery. Thus, the micro swimmer propulsion system with SAW deserves to be expected in blood vessels, based on the advantages of high power density, self-propelled and simple structure. [ABSTRACT FROM AUTHOR]

A new piezoelectronic transistor (PET) is proposed for ultralow-voltage high-speed integrated circuits. The device is comprised of a cylindrical piezoresistive (PR) channel and a torus-shaped piezoelectric (PE) gate surrounding the channel for applying pressure from the PE gate to the PR channel without any support structure. The PR channel can largely change its resistivity owing to the metal–insulator transition that is induced by the pressure applied from the PE gate. The PET can achieve high current drivability even at ultralow voltages (e.g., 0.2 V) due to the metallic channel during its ON-state and exhibit low leakage current due to the insulating channel during its OFF-state. In this study, two design methodologies of the PET are proposed to achieve a desired ON-current at an ultralow voltage or a desired OFF-current in the shutoff state. Both the designs can maintain an ON-current density that satisfies a value requested for achieving reliability. Also, we develop an equivalent circuit for analyzing the performance and behavior of the PETs and circuits configured with them. An inverter configured with complementary PETs can exhibit high-speed performance [several gigahertz (GHz) operations] at ultralow voltages (~0.2 V). [ABSTRACT FROM AUTHOR]

Surface acoustic wave atomization is also effective for generating microparticles and nanoparticles, because of the small wavelength with the high frequency. In this work, a novel directional surface acoustic wave (SAW) atomizer via a novel 9.6 MHz unidirectional interdigital transducer (U-IDT), a driving interdigital transducer (D-IDT) and a reflector interdigital transducer (R-IDT), is proposed and studied for the 1-micron spray system, such as the pulmonary drug delivery system and high-precision film deposition system. The atomization characteristics of a water drop are evaluated with atomized droplet size, atomizing particle velocity, and atomizing rate. Around 1 µm atomized droplet diameter, 585 mm/s atomizing particle velocity, and 4.2 ml/min atomizing rate are achieved and investigated. Based on the 1-micron atomized droplet diameter and high diffusion velocity, a novel pulmonary drug delivery system with the SAW spray can be excepted as an effective non-intrusive treatment method. It is also suitable for microparticle and nanoparticle spray without the pump and fan systems in the fields of industry, cosmetics, medicine, and medical devices. [Display omitted] • Based on a 128 ̊ y-rotated x-propagation lithium niobate substrate, a U-IDT device with the D-IDT and R-IDT is designed and manufactured. The power ratio of directional SAW is up to 91.5%. • The directional SAW spray at 9.6 MHz presented a good property of atomized droplet diameter for pulmonary drug delivery system. • The atomizing particle velocity and atomizing rate of the water drop atomization are investigated microscopically and macroscopically. 585 mm/s atomizing particle velocity, and 4.2 ml/min atomizing rate are achieved and investigated. The high diffusion velocity can be achieved without the pump and fan system. [ABSTRACT FROM AUTHOR]

Self-propelled swimmers using ultrasonic transducers have been proposed and studied. The screw and bionic propulsion systems have dominated underwater robots. However, the complex structures make miniaturization difficult. The swimmers with ultrasonic transducers have no moving parts such as fins or propellers and can be driven by the nanomechanical-vibration in the surface of the transducer. Simple structure and high driving frequency make it easy to miniaturize. A 36° Y-cut lithium niobate (LN) thickness-vibration-mode transducer is used to investigate an underwater acoustic propulsion system. LN transducers are manufactured to 10 × 10 mm, 7 × 7 mm, and 4 × 4 mm square plates. The zero-speed propulsion and no-load speed are investigated to evaluate the swimmer performance. A mm-order swimmer is studied with a 4 × 4 mm LN transducer. At last, the multi-degrees-of-freedom swimmer driven by three 7 × 7 mm LN transducers is demonstrated with the advance and sway locomotion. In the future, a small-scale and agile self-propelled swimmer with an acoustic propulsion system can be expected for narrow and complex environment tasks, such as seagrass-prone areas and narrow pipelines. [Display omitted] • At 10 W, the zero-speed propulsions of LN and PZT transducer are 7.8 mN and 4.9 mN. The zero-speed propulsion of LN transducer is 1.6 times greater. • A mm-order miniaturized swimmer with 4 × 4 × 0.35 mm LN transducer is realized. • A triangle multi-degree-of-freedom swimmer with three 7 × 7 mm LN transducers is designed and fabricated. [ABSTRACT FROM AUTHOR]

An autonomous swimmer with the acoustic propulsion system is proposed and evaluated in novel area of acoustofluidic actuation. The ultrasonic transducer has the same or higher propulsion power with the nanometer/micrometer vibration amplitude and the MHz/kHz frequency, compared with the locomotion of jellyfish body. The sound pressure and flow velocity measurements demonstrate the higher-pressure gradient and fluid downstream to investigate the acoustic propulsion force generated by pushing the surrounding water rearward. The performance of acoustic propulsion system is thus evaluated based on the sound pressure and flow velocity measurements equivalently. The vibration distributions in the transducer surface exhibit a ripple effect and gradually decayed from the center to the edge. The radial distributions of the sound pressure and flow velocity in water match the surface vibration amplitudes for thickness-vibration-mode. Based on the investigation of two thickness-vibration-mode PZT disc transducers, the longitudinal sound pressure and flow velocity in the normal direction result in ZSP force. The power radiated by the longitudinal vibration on the surface of the transducer is shown to be the main cause of the propulsion power. The propulsion calculation with vibration velocity is studied to evaluate the propulsion force. For an input power, the acoustic propulsion system with a higher Q-factor transducer has better performance. Autonomous underwater acoustic propulsion systems have a small size, high power density, and a simple structure, making them suitable for pipeline robots, endovascular microrobots, and underwater drones. [Display omitted] • Mechanism of underwater acoustic propulsion system is illustrated in terms of the bio-inspired and biomimetic engineering. • The sound pressure and flow velocity measurements demonstrate the higher-pressure gradient and fluid downstream to investigate the acoustic propulsion force. • The power radiated by the longitudinal vibration on the surface of the transducer is shown to be the main cause of the propulsion power. [ABSTRACT FROM AUTHOR]

A setup and approach for simultaneous measurement of the inverse and direct transverse piezoelectric coefficients of piezoelectric films was constructed. A longitudinal vibration mode resonator with a hydrothermally synthesized (K,Na)NbO 3 film deposited on a SrRuO 3 /SrTiO 3 substrate was investigated. The fabricated vibrator consists of two upper electrodes, one for actuation and the other for sensing. A driving voltage was applied to the actuator electrode to generate mechanical vibration at its resonance frequency. The vibration velocity was measured with a laser Doppler vibrometer, and the output current from the shorted sensing electrode was also measured to simultaneously evaluate the inverse and direct piezoelectric responses. The obtained inverse piezoelectric coefficient e 31 ̅ was −3.60 C/m2, while the direct piezoelectric coefficient e 31 ̅ was almost same at −3.69 C/m2. From these values, the inverse and direct piezoelectric coefficients e 31 , f were −4.93 and −5.05 C/m2, respectively. [Display omitted] • Measurement method establishment of the inverse and direct transverse piezoelectric coefficients for piezoelectric films simultaneously. • Use longitudinal vibration mode resonator using a hydrothermally synthesized (K,Na)NbO 3 film deposited on SrRuO 3 /SrTiO 3 substrate • Almost similar inverse and direct piezoelectric coefficients ( e 31 ̅) value of −3.60 and −3.69 C/m2, respectively. [ABSTRACT FROM AUTHOR]

This paper proposes a novel system for three dimensional – position and velocity measurements with echolocation. It is improved from the former systems, based on low computational one-bit signal processing, to have wider detectability from one and two dimensions to three dimensions with the rearrangement of the ultrasonic receiver positions. The proposed method can measure the object location from non-linear equations without using iterative methods. This method can concurrently measure position and velocity in three dimensional spaces with one-time measurement. The sound radiation and reflection studies using echolocation are also included in this paper. The additive noise: White Gaussian Noise, Colored Gaussian Noise, General Gaussian Noise, Laplacian Noise, and Gaussian Mixture Noise, is considered for the performance study. The system consists of one sound transmitter and three receivers. These devices are simple sound packages to support low-cost applications. In addition, to satisfy the requirement for a low-computation cost, an echo is converted into a one-bit signal by a three-channel delta–sigma-modulation board. Then, FPGA is used to determine recursive cross correlation based on one-bit computation. The object location is then defined with x – y – z coordinates. The object’s velocity is computed using linear-period-modulated signals. The validity and repeatability of experimental results are evaluated using statistics. [ABSTRACT FROM AUTHOR]