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The aim of this research is to evaluate the performance of impact-induced vibration control using momentum exchange impact damper with pre-straining spring mechanism (PSMEID) based on the energy analysis and verifying the effectiveness of the proposed method experimentally using a simple three-body collision model. It is shown from the simulation study that the fraction of energy absorbed by the primary mass was small if the excitation frequency differs from the primary mass natural frequency. In the case of excitation frequency is lower than the primary mass natural frequency, most of the impact energy is transferred to the damper mass. For excitation frequencies higher than the primary mass natural frequency, a large amount of impact energy is reflected after the collision. The energy absorption ratio is small if the damper mass ratio(M d /M p ) approaches 0.2 and the ratio between pin force (f )and the reference friction force (f ) closest to 1. The optimum condition of the pre-straining spring stiffness increases when the impact damper mass ratio is increased. The experiment was conducted to validate the simulation results. The experimental data has shown that the fref minimum acceleration response is obtained using the pre-straining spring deflection ratio (xps/xpsref= 0.18).

This study proposes a new method for reducing the shock vibration response of an Unmanned Aerial Vehicle (UAV) during the landing process by means of the momentum exchange principle (MEID). The performance of the impact damper is improved by adding a pre-straining spring to the damper system. This research discusses the theoretical application of the damper to the UAV landing gear system. The UAV dynamics is first modeled as a simple lumped mass translational vibration system. Then we analyze a more complex two-dimensional model of UAV dynamics. This model consists of the main wheel, nose wheel and main body. Three cases of UAV landing gear mechanisms: without damper, with passive MEID (PMEID) and with pre-straining spring MEID (PSMEID) are simulated. The damper performance is evaluated from the maximum acceleration and force transmission to the main body. The energy balance calculation is conducted to investigate the performance of PSMEID. The simulation results show that the proposed PSMEID method is the most effective method for reducing the maximum acceleration and force transmission of UAV during impact landing.

A Combination of dynamic vibration absorbers (DVAs) consist of Tuned Mass Damper (TMD) and Tuned Liquid Column Damper (TLCD) for reducing vibration response of a two-DOF shear structure model is proposed. The absorber parameters are optimized using Genetic Algorithm (GA). The cost function is derived from the ratio between structure response and the excitation signal. The limitation in absorber space and fluid motion are considered during optimization process. The simulation results show that GA optimization procedure is effective to get the optimal absorber parameters in the case of limited absorber size and motion.

This research is aimed to design and analyze the performance of double dynamic vibration absorber (DVA) using a pendulum and a spring-mass type absorber for reducing vibration of two-DOF vibration system. The conventional fixed-points method and genetics algorithm (GA) optimization procedure are utilized in designing the optimal parameter of DVA. The frequency and damping ratio are optimized to determine the optimal absorber parameters. The simulation results show that GA optimization procedure is more effective in designing the double DVA in comparison to the fixed-points method. The experimental study is conducted to verify the numerical result.

Tuned liquid column damper (TLCD) is a simple technique used to increase the structure resistance to the external load. This type of damper can effectively decrease the structure response when the TLCD parameters such as the natural frequency and damping factor are well selected. Even though several TLCD models have been proposed and many algorithms to optimize the TLCD parameters have been developed. However, it is very little research has been conducted to evaluate the TLCD damping factor experimentally. A simple method for adjusting the TLCD damping factor empirically is by varying the orifice blocking ratio. In this research, 5 types of blocking ratio were trialled in the TLCD. They were without orifice and with 2, 4, 6 and 8 18 mm diameter orifices. The TLCD is positioned at the second floor of a Two-DOF shear structure. A frequency response function showing the ratio between the response magnitude and the excitation force on the structure in the frequency domain was recorded for each trial. The results show that the TLCDs with orifices damped vibrations more effectively than the one without orifice. The larger the blocking ratio, the larger the TLCD damping factor. Two 18 mm orifices were insufficient to damp the vibration as the blocking ratio is too large and TLCD is less responsive to the vibrations. The optimum condition of a U-Shaped TLCD blocking ratio was found to be 70.77% which corresponded to 4 holes of 18 mm orifice diameter. This type of TLCD dampened up to 80.04% of the vibration magnitude.

In the authors’ previous study, we proposed a novel shock vibration control method using the active momentum exchange impact damper (AMEID). By using this method, the shock vibration of the vibratory system is greatly reduced by transferring part of its momentum to the damper mass. This feature is effective for suppressing the first large peak value of the acceleration response due to a shock load. However, the validity of AMEID for actual implementations has not yet been investigated. In this paper, the active control of shock vibration using AMEID under real conditions is evaluated by simulation and experiment. A one-degree-of-freedom vibratory system is used as the controlled object. The controller is designed using the linear quadratic regulator optimal control theory. Reductions in the acceleration response and transmitted force to the base are investigated using simulations. Experiments are carried out to verify the simulation results.

Impact vibration such as a floor vibration caused by jumping of children or vibration of a press machine is very important engineering problem. The momentum exchange impact damper has been proposed to solve these problems. The basic principle of this damper is based on the energy transfer on collision of three body systems. However energy or momentum transfer at the impact is not explained theoretically. This paper considers the energy transfer incurred during collisions in three body systems. The three body systems considered herein consists of an impact mass, a main body and an absorber mass. When the impact mass collides with the main body, part of its kinetic energy is transferred to the main body. When the main body simultaneously collides with the absorber mass, part of the kinetic energy of the main body is transferred to the absorber mass. Consequently, the main body receives a small amount of shock and it is possible to keep the main body nearly stationary. In this study, the influence of contact frequency and natural frequency of the system on the energy transfer during collision is analyzed. A theoretical model is developed to analyze the effect of various system parameters. It is shown that the maximum transfer of energy that can be obtained occurs when the contact frequencies are the same. The theoretical analysis is validated with experimental results., Special Issue on The Twelfth Asia Pacific Vibration Conference (APVC2007)

This paper proposes an active control type of momentum exchange impact damper (AMEID) and its application to reducing shock vibration of the floor. The floor is modeled as a one-degree-of-freedom system. The active component of AMEID is realized by using a linear motor. The controller design of AMEID is based on the LQR optimal control theory. The simulation results show that the performance of AMEID is not affected by the mass ratio. In addition, the performance of AMEID is compared with the conventional passive momentum exchange impact damper (PMEID), the active mass damper (AMD) and the conventional active control method in reducing the floor shock vibration. It is shown that the shock reduction performance obtained by AMEID is larger than that obtained by PMEID. The power consumption and the stroke of the actuator for AMEID are lower than those of AMD. Furthermore, the transmitted force obtained by AMEID is smaller than that of the conventional active control.

This paper deals with reducing floor impact vibration and sound by using a momentum exchange impact damper. The impact damper consists of a spring and a mass that is contact with the floor. When a falling object collides with the floor, the floor interacts with the damper mass, and the momentum of the falling object is transferred to the damper. In this works a computational model is formulated to simulate dynamic floor vibration induced by impact. The floor vibration is simulated for various sized damper masses. A proof-of-concept experimental apparatus was fabricated to represent a floor with an impact damper. This example system consists of an acrylic plate, a ball for falling object, and an impact damper. A comparison between simulated and experimental results were in good agreement in suggesting that the proposed impact damper is effective at reducing floor impact vibration and sound by 25% and 63%, respectively.

In recent research it was found that squeal noise caused by friction-induced vibration can result in mode coupling instability. Presently, there is no method that can be reliably used to eliminate this kind of noise. This paper is focused on the use of dynamic vibration absorbers (DVAs) to suppress the generation of squeal noise. The performance of the DVA is investigated numerically for two simple cases, i.e. a simple two-degree of freedom model, and an L-shape space frame. It is found that the DVA can be applied to shifting or reducing the unstable region of mode coupling, by which the unstable region is removed from the operating condition. Particularly, the addition of the DVA in horizontal direction on the near-point-of-friction can possibly avoid unstable mode coupling. However, the addition in vertical direction will increase the possibility of squeal noise incident. Moreover, a high frequency DVA in horizontal direction at the near-point-of-friction shifts the unstable region into higher normal contact stiffness and higher friction coefficient. Consequently, addition of a mass with very stiff spring or a rigid mass in the horizontal direction can prevent the occurrence of unstable mode coupling, as long as it is not coupled with the vertical direction. If the added mass affects the dynamic behaviors in both vertical and horizontal directions, squeal noise in the original normal contact stiffness can still occur.

The authors' previous study proposed a novel shock vibration control using the active momentum exchange impact damper (AMEID) in simulations. By using this method, the shock vibration of the vibratory system is greatly reduced by transferring a part of its momentum to the damper mass. This feature is effective for suppressing the first large peak value of the acceleration response due to a shock load. In this paper, the active control of shock vibration using AMEID in actual conditions is evaluated by experiments. A one-degree-of-freedom vibratory system is used as the controlled object. The controller is designed by using the discrete-time LQR optimal control theory. The effectiveness of the AMEID approach is verified experimentally.

Nowadays, a passive vibration control technique using dynamic vibration absorbers (DVA) has drawn many researchers’ attention in the structural dynamic field. The reason is that this technique is simple and it can work effectively in reducing the vibration response when its parameters are optimally designed. The DVA fundamental concept is the addition of a new vibration system to the primary system. This new system addition causes reduction of the vibration response of the primary system during excited by a dynamic load. One simple technique to realize the DVA for structural application is by using water vibration. This research is aimed to develop one type of dynamic vibration absorber using the water vibration system in a U-shaped container for a two-story building structure model. Besides being used as the dynamic absorber, this U-shaped container is also functioned as the water storage tank in the building. Regarding reduce the first bending mode response of the structure in x-z and y-z plane, two U-shaped water storage tanks are placed on the upper floor of the building. The dimensions of the water storage tanks are designed so that the natural frequency of moving water in the tank is the same as the natural frequency of the first bending mode of the structure in x-z and y-z plane. The performance of dynamic absorber is evaluated by applying the impulsive and seismic loads on the building. The simulation results show that the U-shaped water storage tank placed on the upper floor of the building can reduce the response amplitude of the structure under impulsive loads. Meanwhile, for the seismic load case, the performance of dynamic absorber is clearly seen when the excitation frequency is close to the natural frequency of the building structure.