Itsuro KAJIWARA

This study evaluates the basic characteristics of smart structures composed of dielectric elastomer actuators (DEAs) to suppress vibrations. A DEA, which is a lightweight, flexible polymer that can induce high deformations, should realize next-generation actuators. Additionally, DEA can achieve vibration control of structures with complex shapes or curved surfaces. Herein the performance and efficacy of DEAs are evaluated as an actuator for vibration control at high frequencies. First, the appro

A vibration suppression technique for lightweight and flexible membrane structures is proposed using smart structure technology with a dielectric elastomer actuator (DEA). DEA, which is a lightweight flexible polynomial material with a large deformation and high response time, can easily be applied to membrane structures for vibration suppression over a wide frequency range. Herein, active vibration control for membrane structures with DEA is examined. A non-contact excitation system with a high

The design variables of both the structural and the control parameters are optimized simultaneously by the sensitivity analyse to minimize the response due to disturbances of both white noise and colored noise subjected to a constraint so that the system is stable corresponding to high-order natural modes. Three kinds of models are adopted in the approach, namely, the original spatial model by finite element method, the reduced modal model for designing the control system, and the original modal

A health-monitoring system is proposed to detect holes drilled in a pipe based on laser plasma acoustic excitations and acoustic measurements. In this system, an acoustic excitation is applied to a pipe via a laser-induced plasma in air generated by a high-power Nd: YAG pulse laser. Laser-induced plasmas can realize non-contact acoustic impulse excitations. A microphone is used to measure the time response of the acoustic pressure. In this study, we focus on the detection of a hole in the pipe.

A method for structural dynamic optimization is proposed using sensitivity analysis of resonance and anti-resonance frequencies. The sensitivity of the anti-resonance frequency is newly defined. An approach for eliminating the resonance peak from the frequency response function (FRF) is proposed using this sensitivity, modifying both the frequencies of this resonance and the neighboring anti-resonance bottom to the same value. The proposed method is applied to determine the optimum thickness of

The purpose of this study is to develop a simple and practical controller design method without modeling controlled objects. In this technique, modeling of the controlled object is not necessary and a controller is designed with an actuator model, which includes a single-degree-of-freedom virtual structure inserted between the actuator and the controlled object. The parameters of the virtual structure are determined so that indirect active vibration suppression is effectively achieved by conside

Technology for micro air vehicles (MAV) has been attracting the attention of researchers. Multidisciplinary optimization is expected to help achieve the stability and higher performance required for successful MAVs. This paper demonstrates the use of simultaneous aerodynamic shape optimization and control system design for improved stability and performance. The objective of the optimization is to reduce the control energy and improve stability for controlling the roll motion, which becomes incr

For active vibration control of powertrain oscillations, the purpose of this research is to present a simple fuzzy-reasoning-based compensation strategy for a time-varying control cycle limitation of an actuator. A simplified drivetrain dynamics model is shown, and the simulation configuration with the control cycle limitation is constructed. A model predictive compensation using a sampled-data controller is employed to tackle the maximal phase delay of the control input due to the time-varying

The authors propose an approach of optimal design for simultaneous optimization of structure and control systems. The dynamic characteristics of the regulator system is optimized against given disturbances. The present report considers two kinds of disturbances applied to the structural system. One is a white noise disturbance and the other is a harmonic wave disturbance. In case of a white noise disturbance, optimization is achieved by modifying the performance indexes with respect to both the

Model-based controllers with adaptive design variables are often used to control an object with time-dependent characteristics. However, the controller’s performance is influenced by many factors such as modeling accuracy and fluctuations in the object’s characteristics. One method to overcome these negative factors is to tune model-based controllers. Herein we propose an online tuning method to maintain control performance for an object that exhibits time-dependent variations. The proposed meth

Active vibration control of automotive drivetrains must be developed to compensate for the backlash of gears because it causes undesired responses. In addition, an engine used as an actuator has a constraint which makes the control periods longer and time-varying, resulting in deterioration of the control performance. The contribution of this study is to cope with all the issues described above, backlash and the control period constraint, simultaneously. First, a basic experimental device, which

The direct tuning of controller parameters, which is based on data-driven control, has been attracting considerable attention because of the ease of its control system design. In practical use, it is important to consider the stability of the closed-loop system and model matching with few design parameters. In this study, we propose a direct tuning method based on a fictitious reference signal that considers the bounded-input bounded-output (BIBO) and model matching without repeating experiments

A vibration experiment technique based on a dielectric elastomer actuator (DEA) excitation for apples is proposed. The characteristics of DEAs such as flexibility, lightweight, large deformation, and a fast response are conducive to vibration applications. Moreover, DEAs composed of soft rubber-like materials should be compatible with diverse objects. They can be applied to structures with curved surfaces and transfer excitation forces effectively. Herein, as an agricultural application, a DEA e