Jun Kuroda

Design of resonant frequencies for piezoelectric actuator with integrated components

Piezoelectric actuators are used in a wide range of electrical devices, including piezoelectric speakers, buzzers, haptics and ultrasonic transducers. For piezoelectric actuator systems used in mobile devices, the most important issue is improving the electromechanical conversion efficiency. The power consumed by the actuators must be minimized due to the small size of the batteries used. The frequency response around the mechanical resonance must be carefully designed to enable low power driving. The resonant frequencies of piezoelectric actuators that consist of integrated components, such as the metal cones in ultrasonic speakers, are determined by the energy dispersion of the total system. Therefore, factors such as the size and physical properties of each component must be designed to optimize the resonant frequencies for practical applications. The total energy of the piezoelectric system is described by Lagrange-Maxwell equations. Even though it is not easy to solve the differential equations writt...

Study to fabricate high-quality and portable parametric speakers

Parametric speakers provide narrow directional audible sounds using modulated ultrasounds. Parametric speakers are employed to build audio communication with privacy protection, which is expected to be installed into various instruments. To respond to this requirement, slim-sized parametric speakers delivering high-quality sound must be fabricated. Ultrasonic transducers usually consist of piezoelectric elements and metal resonators, which have a number of resonant modes. To demodulate audible sounds by the non-linearity of a finite amplitude sonic wave, a large amplitude carrier wave must be emitted. Therefore a predominant resonant mode of an ultrasonic transducer is used to transmit carrier wave. Moreover, frequency band around the predominant resonance is used to transmit modulated Fourier components of signals. While considering these principals of sonic transmission, two issues must be solved to fabricate a slim-sized and high quality parametric speaker, i.e., 1) widening of available bandwidth and ...

Model-based design of multibeam sonar system

Multibeam sonar is a technique used in many applications in offshore activities. Sonar consists of an integrated system of components: acoustic transducers, signal transmitters and receivers, and signal processing circuits. Numerical prototyping by model-based design (MBD) is widely employed to develop various instruments, which could also be useful in designing signal processing algorithms and configurations of sonar systems. A sonar system is divided roughly into two subsystem blocks, block 1: electric circuits and signal processing subsystem, and block 2: acoustic subsystem. The design of block 2 requires numerical simulation of an ultrasound wave reflected by targets. One issue for MBD of multibeam sonar is to study a high speed and low cost computational method to simulate echo signals. Numerical computation methods, such as finite-element method, require significant computational resources to solve a large acoustic field. However, multibeam sonar is used for targets which are typically located away ...