Introduction

The main research subjects consist of optimum design, health monitoring, and deformation/shape control of structures. These researches are,

to express design problems or identification problems by Mathematical Models
to obtain the optimal solution by using optimization methods, e.g. Mathematical Programming Method and Genetic Algorithm.

Recently, we have also studied prediction methods of mechanical properties of composite structures/materials. Contents of each subject are as follows :

Optimum Design of Spacecraft Structures
Health Monitoring of Space Structures
Deformation and Shape Control of Space Structures
Evaluation of Mechanical Properties of Composite Structures/Materials

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1. Optimum Design of Spacecraft Structures

Minimum weight design of wing/body structures is important in aircraft and spacecraft design. Stress distribution or displacement of the structures under applied external forces can be evaluated by Finite Element Method. In structural design, structures with minimum weight can be determined in detail by using Finite Element Analysis with Optimization Method.

The results obtained through the research on optimal design of spacecraft structures can sharply improve the performance of structures by saving their weight, their safety and reliability by optimal design. We have examined the optimization procedures for structural design, which can save the computational time and obtain the nearly optimal solutions by adopting some new schemes on the formulation and solution methods of optimization problems. We can obtain the stable and reliable optimal solutions by choosing proper optimization method, like mathematical programming methods, genetic algorithms, or so on, which depends on the nature of the optimization problem.

We have studied Optimum Design of Composite Structures under various constraints, e.g. strength, buckling, vibration, aeroelasticity, and so on. Optimum Design Method of composite laminates based on the concept of Lamination Parameters has been developed and Efficient Optimum Design Methods based on Approximation Technique have also been proposed.

Aeroelastic characteristics, like flutter or divergence instability, are some of the most important factors for spacecraft and aircraft design. Aeroelastic tailoring technique which obtains optimum structures by using composite materials can realize the unique aircraft like X-29 forward-swept wing aircraft shown in Figure.1. We have studied aeroelastic tailoring and control techniques based on optimization approaches for future aircraft and spacecraft structures.

Figure 1. Optimum Design of Spacecraft Structures

Areas of Interest :

[Dr. Thesis] Stabilization of Numerical Simulation of Damage Propagation in FRP Laminated Structures

[Dr. Thesis] An Efficient Design Approach for Aeroelastic Tailoring and Control of Composite Plate Wings

[Dr. Thesis] Optimal Material Distribution for Improving the Fracture Strength of Functionally Graded Thick Cylinders

[Dr. Thesis] Improvements of Space Debris Protection System of Space Structures

[Ms. Thesis] Optimum Design of Lattice Cylindrical Shells under Axial Compression

[Ms. Thesis] Optimum Design of Composite Plate Wings for Flutter Characteristics

[Ms. Thesis] Optimum Design of Composite Wing Considering Stiffened Panel Buckling

[Ms. Thesis] Optimal Topology and Material Constitution of Composites Using A Homogenization Method

[Ms. Thesis] Flutter Suppression of Composite Plate Wings Focused on Twist Vibration Mode

[Ms. Thesis] Study of Low-velocity Impacts in Composite Laminated Plate

[Ms. Thesis] Panel Flutter Analysis of Delaminated Plates

Topology Optimization of Truss Structures

Efficient Optimization of Truss Structures Using Nonlinear Programming Method

Optimization of 3-D Truss Structures for Vibration Characteristics

Dynamic Characteristics of CFRP Laminated Cylindrical Shells

Analysis on Static Aeroelastic Deflection of Composite Plate Wings

Fundamental Study on Morphing Wing

Effect of Actuator Location on Static Aeroelastic Control of Composite Plate Wings

Experimental Verification of Vibration Characteristics of Cantilevered Plates

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2. Health Monitoring of Space Structures

Space structures like the space station as shown in Figure 2 are under construction. We have developed the health monitoring system in order to evaluate the damage of space structures due to fatigue damage, collision of space debris and so on. This health monitoring system can sharply save the maintenance cost, and improve the safety and reliability of space structures, aircraft structures, and others.

Damage location and its magnitude can be identified based on the structural vibration responses or static responses, which are obtained by using accelerometers, piezoelectric sensors or so on.

System identification has also been studied to evaluate the stiffness distribution of the spacecraft and the space structures from their structural responses.

Figure 2. Optimum Design of Space Structures （ © JAXA ）

Areas of Interest :

[Dr. Thesis] Real-Time Impact Force Identification of Plates and Shells

[Ms. Thesis] Damage Identification of Laminated Plates and Truss Structures Based on Dynamic Residual Forces

[Ms. Thesis] Delamination Identification of Composite Laminates Based on Vibration Characteristics

[Ms. Thesis] Parameter Identification Using Vibration Characteristics Based on Experimental Design

[Ms. Thesis] Stiffness Identification of Symmetric Laminates Using Vibration Data

[Ms. Thesis] Impact Force Identification of Composite Structures Using Modal Sensor

[Ms. Thesis] Impact Force Identification of Laminated Plates Using PZT

[Ms. Thesis] Measurement of Modal Displacement and Application to Impact Force Identification

[Ms. Thesis] Study of High Accurate Identification of Impact Force Acting on Composite Structures

[Ms. Thesis] Precise Measurement of Modal Displacement in Structural Vibration

[Ms. Thesis] Study of Impact Damage Monitoring Techniques on CFRP Laminates

[Ms. Thesis] Study of a Highly Accurate Method for Solving Inverse Problem of Impact Force Acting on CFRP Laminates

[Ms. Thesis] Experimental Identification of Impact Force Location and History on CFRP Composite Structures

[Ms. Thesis] Impact Force Identification of CFRP Stiffened Panel under Multiple Loading

[Ms. Thesis] Experimental Identification of Impact Force on Frame Structures

[Ms. Thesis] Damage Monitoring of CFRP Plates by Impact Force Identification

[Ms. Thesis] Rapid Impact Force Identification of Plate Structures

[Ms. Thesis] Non-power Structural Health Monitoring using Piezoelectric Energy Harvesting

[Ms. Thesis] Impact Force Identification of Plates using Piezoelectric Materials

[Ms. Thesis] Experimental Impact Force Identification of FRP Composite Tanks under Multiple Loadings

[Ms. Thesis] Impact Force Identification of Plates Using Sound Waves

Parameter Identification Based on Frequency Response Functions

Damage Location of Truss Structures Based on Vibration Mode Expansion

Impact Force Identification of Laminated Plates Using Strain Gauges

Identification of Boundary Conditions Using Dynamic Responses

Experiment of Impact Force Identification of CFRP Laminated Plates with Embedded Piezoelectric Sensors

Impact Force Identification of CFRP Laminated Plates Based on Experimental Model

Impact Force Identification of Composite Structures Using Measurement Data

Impact Force Identification of CFRP Stiffened Panel

Impact Force Identification of CFRP Stiffened Panel using Piezoelectric Transducer

Identification of Multiple Impact Force Histories of CFRP Stiffened Panels

Sensor Location for Impact Force Identification of CFRP Laminates

Experimental Identification of Impact Force Using Lamb Wave

Experimental Identification of Impact Force of Composite Tank

Identification of Impact Force Location of CFRP Stiffened Panels using Lamb Wave

Impact Force Identification of CFRP Structures Using Sound Waves

Experimental Estimation of Dynamic Response of CFRP Laminated Plates

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3. Deformation and Shape Control of Space Structures

Space Antennas are needed to keep their own shape with high accuracy against external disturbance or temperature change. Besides, Space Truss Structures are needed to suppress vibration due to dynamic external disturbance.

Shape control or vibration control are indispensable techniques for space structures as shown in Figure 3. We have studied the optimal placement of sensors and actuators for the deformation and shape control of large-scale space structures. The results obtained through this research can realize the automatic and real-time control of space structures, and sharply improve their safety and reliability.

We have also studied the optimal topology or the optimal shape for adaptive structures like deployable truss structures or variable geometry truss (VGT).

Figure 3. Deformation and Shape Control of Space Structures （ © JAXA ）

Areas of Interest :

[Dr. Thesis] Study of High Accurate Static Shape Control and Vibration Control of Space Structures Based on the Optimal Placement of Sensors and Actuators

[Ms. Thesis] Actuator/Sensor Location for Static Shape Control of Truss Structures

[Ms. Thesis] Vibration Control of Laminated Plates Using Modal Sensor/Piezoelectric Actuator

[Ms. Thesis] Static Shape Estimation of Truss Antennas Based on Strain Measurements

[Ms. Thesis] Vibration Control of CFRP Laminated Plate Using Highly Accurate Modal Sensor

[Ms. Thesis] Energy Recycling Vibration Control using Piezoelectrics

[Ms. Thesis] Vibration Control of CFRP Laminated Plate Using Piezoelectric Actuators and Sensors

[Ms. Thesis] Vibration Control of CFRP Laminated Plate using Piezoelectric Fiber Actuators

[Ms. Thesis] Vibration Measurement/Control of Plates with Consideration of Higher-order Mode Vibrations

[Ms. Thesis] Vibration Control of CFRP Cantilever Beam Using Piezoelectric Energy-harvesting Technique

[Ms. Thesis] Self-sensing Semi-active Vibration Control using Piezoelectric Materials

[Ms. Thesis] Vibration Control of Plates based on the Optimal Placement of Piezoelectric Fiber Actuator

[Ms. Thesis] Semi-Active Vibration Control of CFRP Laminated Plates Using Piezoelectric Devices

Deployment/Retraction Characteristics of Two-Dimensional Deployable Truss Structures

Actuator Location for Shape Control of Truss Structures

Piezoelectric Actuator Location for Vibration Control of Laminated Plates

Construction of Modal Sensor by Optimization of Sensor/Gain Distribution

Optimal Location of Actuators for Shape Control of Truss Antenna Structures

Experimental Verification of Modal Sensor Using Strain Data

Effect of Actuator Location on Vibration Control of CFRP Laminated Plates

Experiment of Vibration Control of CFRP Laminated Plates Based on LQR Control Law

Vibration Control of CFRP Laminated Plates Subjected to Impact Force

Fundamental Study on Vibration Control Based on Stiffness Variation

Passive Vibration Control using Piezoelectrics

Switch Timing in Semi-active Vibration Control

Vibration Control of Cantilevered Plates based on Experimental Modal Analysis

Vibration Control of CFRP Beams Using SSDV

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4. Evaluation of Mechanical Properties of Composite Structures/Materials

Carbon nanotube reinforced composites are some of ideal candidates for future lightweight composite materials. We constructed a structural mechanics three-dimensional beam model based on the molecular force field theory of molecular mechanics and the computational structural mechanics, and then we have studied a method for evaluation of materials based on multi-scale analysis, where the effect of the interaction between the nanotube and the outer polymer matrix at the level of atoms is taken into account.

On the other side, we have also studied an active sensing technique based on Lamb wave propagation as damage identification techniques for CFRP laminates of aircraft structures and so on. For the damage identification using Lamb wave propagation characteristics, a highly accurate and efficient wave propagation analysis technique is quite essential. We have developed a new wave propagation analysis technique based on a hybrid spectral method by using spectral elements and highly-accurate finite elements.