This study demonstrates the efficiency of a new semi-active vibration control method validated using real-time hybrid simulation considering a single-degree-of-freedom system. The semi-active control method treated in this study is based on harmonically varying damping. Even if the input to the system doesn't contain the natural frequency of the system, it is possible to choose the frequency of the damping coefficient so that the response includes the natural frequency. As a result of this operation, resonance can be induced, with the phase and amplitude of the resonance adjustable through the damping parameters. Previous study proposed a new vibration control method to take advantage of harmonically varying damping. In the case that the excitation contains the natural frequency of the system, resonance is induced. At the same time, if the additional harmonic vibration induced by the variable damping is at the same frequency of the resonance yet anti-phase, the resonance can be reduced by interference. An expression for the variable damping controller has been developed in the case of an ideal variable damping device and control performance has been confirmed by numerical simulation. However, the control method does not directly apply to actual variable damping devices, because the control laws determine the ideal variable damping ratio, neglecting any nonlinearities of actual damping devices. In this study, the proposed theory has been modified to fit a magneto-rheological (MR) damper. Validation of the modification was performed experimentally using real-time hybrid simulation.

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Pneumatic actuation systems are commonly used to drive the positioning stage due to several merits. However, one of the critical demerits of the pneumatic systems is the problem of the compressibility, which results in the flow disturbance. Another problem of the positioning stage can be addressed to the vibration which occurs due to the active condition of the base plate. This paper concerns the mentioned two issues in a pneumatic positioning stage. In order to suppress the flow disturbance and to reduce the horizontal vibration of the stage due to the reaction force, a combined control scheme is proposed. This scheme is composed of the fusion of flow disturbance observer (FDOB) and base plate jerk feedback (BPJFB) scheme. An enhanced experimental methodology is provided to successfully implement the fusion of the mentioned feedback controllers. The results show the effectiveness of the proposed method.

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In this paper a short overview on observability analysis techniques for inertial navigation systems (INS) is given. There are two approaches in the INS observability analysis: algebraic and numerical analysis approaches. Algebraic analysis provides general observability properties for a class of vehicle motions. This approach is suitable for relatively simple motions. On the contrary, numerical analysis can be applied to any motions. However, in order to draw general observability properties from this approach, a considerable number of tests may be necessary. Analysis techniques are briefly introduced and their relations are given. An illustrative numerical example is presented on the analysis techniques.

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Flapping micro air vehicle (FMAV) is considered to exhibit much better performance at low speeds and small sizes compared to fixed-wing MAVs. To maximize the potential and capabilities of FMAVs also to produce adequate design implications, a new aeroelastic model of a typical flexible FMAV is being developed utilizing Euler-Bernoulli torsion beam and quasi steady aerodynamic model. The new model accounts for all natural existing complex interactions between the mass, inertia, elastic properties, aerodynamic loading, flapping amplitude and frequency of the FMAV as well as the effects of several geometric and design parameters. To validate the proposed theoretical model, a typical FMAV as well as instrumented test stand for the online measurement of forces, flapping angle and power consumption have been constructed. The experimental results are initially utilized to validate the flight dynamic model, and several appropriate conclusions are drawn. The model is subsequently used to demonstrate the flapping propulsion characteristics of the FMAV via simulation. Using dimensionless parameters, a set of new generalized curves have been deduced. The results indicate that by proper adjustment of the wing stiffness parameter as a function of the reduced frequency, the FMAV will attain its optimum propulsive efficiency. This fact raises additional new ideas for further research in this area by utilizing intelligent variable stiffness materials and/or or active morphing technology for the sustained, high-performance flight of FMAVs. The generalized model can also be used to conduct a performance and stability analysis of FMAVs and to design and optimize flapping-wing structures.

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Polycarbonate (PC) laminates offer the possibility of designing strong and light weight panes application in automobile. However, the noise insulation performance of PC pane is worse than glass pane because of its high rate of stiffness to low weight. In this work, a new ultra-thin(less than 10mm) sandwich pane is proposed to obtain high transmission loss(TL). The sandwich structure consists of two thin laminates plates of the same PC material and a thin lightweight damping core bonded between those plates. Then TL is predicted using decoupled equations representing symmetric and anti-symmetric motions for a sandwich PC pane. The effects of various structural and material parameters on noise insulation performance are investigated with numerical examples. Numerical results show that the shear rigidity has evident effect on coincidence frequency and proposed structure has better noise insulation properties than single layer PC pane of equivalent thickness.

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This study investigates the motion of micro-parts of different sizes on a symmetrically vibratory feeder system that consists of a saw-tooth surface made of carbide, brass, and zirconia. The velocity and position of micro-parts are time-dependently measured by the particle tracking velocimetry method. We investigate the micro-parts motion for a range of frequencies applied to the surface. The obtained results show that unidirectional motion can be attained by the present feeder system regardless of the surface material and the micro-part size. The motion behavior of micro-parts varies for different experiments and surfaces in spite of the same driving voltage and frequency. This implies that the motion of micro-parts is affected by uncertainties in the system. The micro-part motion consists of numerous frequencies, and the first frequency coincided with the exciting frequency. The results also show that the carbide saw-tooth surface produces the largest micro-part velocity among the three surface materials. Comparing relationship between feeding velocity and velocity spectrum clarifies that the micro-part moves faster when spectrum was clear. The experiments on the carbide surface indicate that the micro-part moves smoothly and a large velocity is observed within 50-70 Hz of driven frequency.

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This paper presents a new type of damping material composed of flexible porous material such as polyurethane foam and liquid such as water. This new type of damping material costs less than viscoelastic materials such as Sorbothane, and is anticipated to have a better damping effect. At the same time, installation of the new type of damping material is as easy as that of usual viscoelastic materials. The damping effect of this material on the vibration of a cantilever iron plate is experimentally compared with the one of a viscoelastic material. The damping effect on a rail piece with a length of 1.2m and a weight of 72kg is also experimentally investigated. The experimental results show a good damping effect. The design variables of this new damping material such as the liquid viscosity and the hardness of the porous material are thought to influence the damping effect, consequently are investigated by carrying out vibration testing of a cantilever iron plate (material:SS400, size:300×440×5mm, weight:5.2kg).

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The formula for obtaining the absorption horsepower of a Moulinet was rewritten, and the physical meaning of the constant in the formula was clarified. Based on this study, the design method of the Moulinet and the calibration method of the Moulinet that was performed after manufacture were verified experimentally. Consequently, the following was clarified; (1) If the propeller power coefficient was taken to be the proportionality constant, the absorption horsepower of the Moulinet was proportional to the cube of the revolution speed, and the fifth power of the Moulinet diameter. (2) If the Moulinet design was geometrically similar to the standard dimensions of the Aviation Technical Research Center's type-6 Moulinet, the proportionality constant C₁ given in the reference could be used, and the absorption horsepower of the Moulinet was proportional to the cube of the revolution speed, the cube of the Moulinet diameter, and the side projection area of the Moulinet. (3) The proportionality constant C₁ was proportional to the propeller power coefficient C_P.

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For the development of high speed flywheel rotation in a vacuum chamber, technology for establishing ultra low loss magnetic bearings and measures for preventing spillover vibration are necessary. For these purposes, tests on two rigs, one involving active magnetic bearings (AMBs) and the other, a medium-size flywheel, were conducted in the present study. With the former, a technique for reducing AMB loss was investigated. In the latter, many trials were carried out in an attempt to find a means for preventing spillover vibration. Based on the results, two important findings were made.
First, AMB loss could be reduced to 1/6 of that in conventional control through the use of zero-power control and homo-polar magnetic poles. Secondly, flywheel rotation as high as 12,000 rpm was possible with no significant vibration through phase lead adjustment and the use of a stabilizing filter. Both these possibilities may be attributed to the very precise measurement of natural frequency and the damping ratio.

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Effect of base shape on damping characteristics of rocking of rigid body is presented. We pay attention to the fact that free vibration amplitude of rigid body decreases rapidly without dampers or damping materials. We consider rocking of rigid body is very attractive as a low cost dynamic vibration absorber. At first, damping characteristics of rocking of typical rigid body with flat base shape is discussed theoretically. Next, we propose new type rigid body which base shape is polygon in order to design damping characteristics of rigid body in wide range. Theoretical method to calculate damping characteristics of rigid body is derived. Experiment of free vibration of the rigid body is carried out and the calculated results of the proposed method agree well with the experimental results. By calculating damping ratio of proposed rigid body using derived equations, it can be seen polygon base shape is very useful to design damping characteristics of rigid body.

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It is known that, under appropriate conditions, the amplitude of vibration of some blades in the mistuned bladed disk system become large compared to what would be predicted by an analysis of the perfectly tuned system. In this paper, the rms responses of the mistuned bladed disk system subjected to random excitation with the spatial decorrelation and correlations are investigated. The effect of the correlation of the random excitation on the rms response is discussed. It is shown that the rms response of the mistuned system subjected to the spatially-uncorrelated random excitation is almost the same as that of the tuned system. In the case the random excitation is spatially-correlated, it is noted that the rms responses of the mistuned system is much larger than those of the tuned system and that the mistuning configurations effect on the rms responses. With the spatial correlation, it is also noted that the particular mode shapes play an important role in the rms response.

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