Taichi Matsuoka

STUDY ON VIBRATION CONTROL DEVICE USING POWER GENERATOR

In this paper, the authors propose a vibration control device using power generator in order to develop a small damper which is suitable for structural vibration control in space. The vibration control device consists of a ball screw, piston, ball nut, gear, power generator, and rod ends. The linear motion of the piston is converted into a rotary motion by the ball screw, and then the electric power is generated as dissipation of energy. A very low sinusoidal input displacement is applied to the device, and the characteristics of the damping force are examined with open circuit and short circuit of the generator. Experimental results are compared with theoretical results. Numerical simulation is applied to a flexible structure, by using sinusoidal input motion, and random motion.Copyright

Vibration Tests of a Cut-off System Using Water and Functional Fluids

In the previous paper, the authors proposed a new Cut-off system for vibration control using water and/or functional fluid which acts as a series inertia mass. In this paper, frequency response vibration tests of the Cut-off system installed in one degree of freedom vibration system are carried out using a shaking table. Transmissibility between main mass and base is measured and evaluated. The Cut-off system consists of a piston cylinder, by-pass pipe, and the fluid. It is clarified that the series mass has a large inertia effect which is proportional to the forth power of the inner diameter of the piston cylinder. The experimental results are compared with the numerical analysis, and the effects of vibration isolation are confirmed.

Semi-Active Control of Civil Structures With a One-Step-Ahead Prediction of the Seismic Response

We propose a semi-active control of civil structures based on a one-step-ahead prediction of the seismic response. The vibration control device (VCD), which has been developed by authors, generates two types of resistance forces, i.e., a damping force proportional to the relative velocity and an inertial force proportional to the relative acceleration between two stories. The damping coefficient of the VCD can be changed with a command signal to an electric circuit connected to the VCD. In the present paper the command signal for changing the damping coefficient of each VCD is assumed to take two values, i.e., the command to take the maximum or minimum damping coefficient. The optimal command signal is selected from all candidates of command signals so that the Euclidean norm of the one-step-ahead predicted seismic response is minimized. As an example a semi-active control of a fifteen-story building with three VCDs is considered. The simulation results show that the proposed semi-active control achieves superior performance on vibration suppression compared with a passive control case where the damping coefficient of each VCD is fixed at its maximum value.Copyright

Seismic Performance of Vibration Control Device That Generates Power

In a previous paper the authors proposed a semi-active vibration control device (VCD) that generates power. The device utilizes a ball screw, and has inertial and damping forces. The damping coefficient is adjusted by altering resistance at the terminal of the power generator. A small-scale VCD was manufactured for experimental testing. Frequency responses of a small-scale spring mass structure were measured in order to confirm the effects of vibration suppression within a wide range of frequencies. In this paper, as the next step, vibration tests using a benchmark structure with an installed VCD that has a 30 kN capacity are carried out at the National Center for Research on Earthquake Engineering (NCREE) in Taiwan. The benchmark structure has three stories with a 3 m height and a mass of 6 tons at each floor level for a total height and weight of 9 m and 18 tons, respectively. The VCDs are installed between adjacent floors with steel chevron braces. A simple control law that is based on a minimized Lyapunov function and employs bang-bang operation is used as a variable current controller instead of the modifying the resistance level of the VCD. Scaled earthquake motions including the Imperial Valley El Centro north-south component that is normalized to be a peak level of 0.5 m/s2 , are applied to the base of the steel framed structure in the horizontal direction by a shaking table. Experimental responses of each floor for the uncontrolled and controlled cases are compared with analytical responses, and effects of vibration suppression for the large-scale model are discussed quantitatively.Copyright

Vibration Tests of a Three Story Benchmark Structure with Vibration Control Devices that Generate Power

Recently, structural problems in tall buildings and power plants have become evident as a result of long-period vibrations due to earthquakes. In order to ameliorate these problems a number of damping devices have been developed by many researchers. One of the authors also has developed the Mechatro damper which has a damping force that is imposed on the structure by a power generator. The force of the damper is proportional to its velocity. On the other hand, the mechanical snubber utilizes an inertial force derived from a flywheel that is proportional to acceleration. That is, the device has a so-called series inertia mass. The authors developed a vibration cut-off system using water or a functional fluid that acts as a series inertia mass, and the effects of vibration cut-off have been confirmed. In a previous paper the authors proposed a new vibration control device (VCD) that also generates power. The VCD has an inertial force created by an inertial disk and damping force provided by energy dissipation of the power generator. This device acts as a semi-active damper, and functions as a fail-safe mechanism under controller malfunction. A prototype model was fabricated and vibration tests were carried out in a laboratory. The focus of this paper is application of the prototype large-scale VCD to a real structure. Two new VCDs that have a force capacity in the range of 15 kN have been manufactured and shipped to the National Center for Research on Earthquake Engineering (NCREE) in Taiwan for testing on a three-story structure that is excited by a large shake table. In order to investigate dynamic properties of the VCD, performance tests are carried out and the resisting force characteristics of the device are measured. Next, vibration tests are conducted on the structure by a shake table with the VCDs installed. Seismic responses at each story level are measured for the Imperial Valley, El Centro north-south component of motion. A control law that is based on minimizing the Lyapunov function is used along with bang-bang operation of the VCD. The effects of vibration suppression using the VCD are shown to be confirmed.

Application of Electromagnet Using Magnetization or Demagnetization for Magnetic Damper

In this paper the authors develop a new type of a hybrid magnetic damper which has a variable damping force generated by hybrid electromagnets. The hybrid electromagnet is composed of a ferrite core combined with a rare-earth magnet. The damper can make the damping coefficient increasing from neutral value with magnetized field, or otherwise decreasing it with demagnetized field. It has also a fail-safe mechanism under an electrically malfunction. In order to determine the magnetic damping coefficients created by eddy current depend on a shape of a magnet and a conductive disk, it is accurately calculated by using an arc shape. For investigating about dynamic properties, resisting force characteristics are measured by using a vibration actuator. In experimental results, the damper has a damping coefficient which is proportional to current squared increasing and decreasing from neutral value. Seismic response simulations of one-degree-of-freedom system with the hybrid damper are calculated using LQR control. The effects of vibration suppression are confirmed numerically.Copyright