Search

The setting parameters of the image enhancement times, the threshold level of the image binarization, and the size of the detecting area were investigated to confirm the accuracy of the four-time-step PTV. The particle density formed the peak distribution as a function of the threshold level of image binarization, and the peak decreased and flattened with the increase of the image enhancement times. Therefore, the wide valid selection of the threshold level of the image binarization and the preservation of high particle density were realized when the image sharpness times was set to be the upper limit of the adequate particle density for four-time-step PTV. Furthermore, as the tendency of the occurring ratio between the correct and error velocity suddenly changed with the variation of the size of detecting area of four-time-step PTV, the size of detecting area was set around that boarder to acquire the velocity field effectively.

Active vibration damper have been gradually used to reduce vibration drastically and adaptively. One of the main defects is to require a big amount of energy. This paper proposes an active mass type regenerative damper. Vibration energy is converted into electric power and stored in the electric battery. But the damper has nonlinear characteristics with dead zone. For lowspeed motion, passive or active control algorithms are applied to the same actuator to achieve good damping performance. This idea is applied to a dynamic absorber system which is composed of electrodynamic actuator and spring. The system is simulated on a computer and a simple experiment is performed. The results are showing that the system has better performance than the pure passive damper and the energy is regenerated.

Active vibration dampers have been gradually used because they have the advantages of reducing the vibration drastically and adaptively. However, one main drawback is the requirement of large amount of energy. Vibration itself is one type of energy and an actuator is an energy converter, so the question arises as to how we can utilize this energy. This paper describes an energy -regenerative-type vibration damper. In this study, electric power is regenerated during high-speed motion of the actuator. For low-speed motion, an active or passive control algorithm is applied to the same actuator to achieve good damping performance. This method is applied to a single degree-of-freedom vibrating system with a linear DC motor. The system is simulated on a computer and a simple experiment is performed. The results show that the proposed system performs better than purely passive vibration control and can regenerate vibration energy.

Electromagnetic bearings have attractive characteristics such as cleanliness and low drag torque, and their application has been gradually increasing. In order to get wide application, however, high-speed stability should be established. There are two kinds of coupling effects ; gyroscopic moment and inductive force. They sometimes adversely affect the system stability when the rotor runs at high speed. In this paper, a high-speed rotor supported by an anisotropically controlled magnetic bearing is analized, and the damping property and stable region are calculated using the root locus diagram. It is found from the analysis that the anisotropic controller stabilizes the inductive coupling effect drastically. This idea is applied to the 3-mass 2-journal bearing rotor, and its capability is tested.

It has been known that the composite loss factor of a partially covered beam with the constrained viscoelastic layers becomes higher than that of a fully covered beam, depending on the beam geometry and the properties of the viscoelastic layer. Damping mechanism of this partial coverage effect, however, has not been examined in detail now. In this paper, the strain energy analyses of the three types of partially covered beams are carried out in order to investigate such damping mechanism. The results of analyses for the center covered beam and the end constrained beam indicate that the partial coverage effect is caused by the shear strain energy dissipation at the outer edges of the viscoelastic layers and also this dissipation depends on both the shear stiffness of the viscoelastic layer and the tensile stiffness of the constraining layers. The composite loss factor of the separately covered beam, which separates viscoelastic layers only at the beam center, becomes higher than that of the partially covered beam due to the energy dissipation of the inner edges of viscoelastic layers. The damping characteristics of these beams are confirmed by some experimental results.

Solenoid has been widely used as a highly reliable and short stroke actuator. However, the main defects are the delay of the actuator motion and its low driving efficiency. Analyzing the various driving parameters, three major factors of solenoid delay are found: mechanical delay caused by movable inertia, current delay by solenoid inductance, and magnetic flux delay by eddy-current. This paper introduces two improvement methods: a driving circuit which utilizes the constant current of a choke coil to make the solenoid current response faster, and a ferrite core which is widely used as a radio frequency magnetic material to decrease the eddy-current loss. These ideas reduce both current delay and magnetic flux delay and also improve the driving efficiency of the actuator. The resulting motion indicates a very small dead time, which is considered very good for servoactuator. High speed solenoid actuator is applied to develop a direct-drive servo-valve and a linear hydraulic servo system. A lthought here is room for improvementt, h e results indicatet he capability of this solenoid actuator to the highly efficient servo system.

It is not uncommon in structural analysis that Some parameters can not be derived theoretically. One of the recent technique for overcoming this problem is to test the structure experimentally and use this information to help estimating the parameters. To calculate all of the structural parameters, however, requires a lot experimental data and the computational time. This paper introduces an efficient method for identifying some of the structural parameters using a receptance reanalysis technique. A simple cantilever beam is simulated on an analog computer and tested to determine parameters related to the clamped end. The results obtained are discussed in detail.

For the purpose of clean and high speed rotation, an actively controlled magnetic bearing has been developed. Recently, a digital control system has been used to get high performance by using the state variable feedback. However, the gyroscopic or inductive mutual effect of a rotating disc sometimes makes the high speed rotor unstable.