About My Research - Adaptive vibration control of structures - * Origination of majoring in vibration control In my sophomore year, despite hardships I made a device that could always face a light with two motors and four photocells. Since that moment, I have known the profound delight that comes from creating new things, and then I chose the field of the control. As the time goes on, I clearly feel my growing up as a professional engineer that I dreamed of since my early years. * Why adaptive control? I want to introduce my major easily with some technical terms. The following conversation was a real situation, which alludes to my future. - Novice: Women have a small absolute value of transfer function. They need a large amount of input, but produce only a small output. - Intermediate: You don't know women exactly. If you excite women with their natural frequency, you can get almost infinite output from them. - Master: But the natural frequency of women varies frequently. We can't know the natural frequencies. - Guru: So adaptive control is needed. You identify the natural frequencies of women at any given time, and then excite in the natural frequency with the identified one at each moment. Real-time system identification is hard to realize, but it can be the solution. The structures, I'm studying, are linear and have limitations on changes, but my wife is nonlinear and is not bounded. I must prove my theories when applying them to structures, but I don't have to prove my studies on her. I would be a guru on the vibration control, but I can't imagine even an intermediate on my wife. * Applications of adaptive vibration control Lightweight and flexible structures made of composite materials often have a vibration problem. For example, minute vibrations in a satellite can spoil drastically the resolution of a picture. Vibration suppression adds high values to structures, especially to semiconductor facilities. If the payload of a robot manipulator changes arbitrarily, the classical vibration controllers fail in their duty. Adaptive control can be a possible approach. * Features of adaptive vibration control In control theory, there is no perfect solution, namely, every controller, including the adaptive vibration controller, has advantages and disadvantages at the same time. The adaptability often requires heavy computational load to a controller and can cause stability problems. * My contributions in adaptive control My major contributions are the suggestion of a real-time estimation method of multi-modal frequencies that needs a light computational burden, and the proposition of an adaptive controller, adaptive PPF, using previous estimations. And I'm preparing a patent with an adaptive shunt circuit that suppresses the vibration adaptively requiring fewer facilities.