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This case study proposes the development of damping technology using intelligent materials as working fluids for the landing gear of Unmanned Aerial Vehicles (UAV) during the landing process. The intelligent materials to be used are magnetorheological fluids (MRF), a liquid that has variable viscosity to magnetic fields. This intelligent material can improve the performance of the damping device by allowing it to have variable damping features through viscosity changing. The proposed UAV magnetorheological (MR) dampers design utilizes a magnetic valve that has an annular flow channel configuration with a 0.5 mm gap size equipped with an electromagnetic coil with adjustable current input. Both gap size and the current input selection affect the performance of the damping device. This study discusses the performance to reduce shock during the landing process. The performance is evaluated by analyzing the pressure drop and damping force produced by the device with changes in the current input variation. The numerical and simulation results show that the damping characteristics of the device could be adjusted by changing the current input to the electromagnet. The obtained results are then adjusted based on the needs of the UAV in landing purposes. The study proved that the device performance is suitable to absorb shock during the landing process of the UAV.

This research proposes a new method for boat impact vibration attenuation using the exchange of momentum principle with a pre-straining spring mechanism. The boat dynamic is modeled using a hinged-supported beam structure. The wave excitation on the boat hull is expressed using one degree of freedom spring-mass system. The simulation study is performed to evaluate the impact damper performance in reducing the boat shock response. Two kinds of momentum exchange impact damper i.e., without and with pre-straining spring mechanism, are evaluated. The simulation results show that the impact damper with pre-straining spring mechanism (PSMEID) is better than the passive momentum exchange impact damper (PMEID) in reducing the boat shock vibration response

This research presents a response analysis of a UAV nose landing gear system equipped with an air damper under shock and harmonic excitation. The study begins with dynamic modeling of the UAV landing gear system. The system dynamics consists of a main mass and a wheel mass that are connected to each other by a U-shaped landing gear. The U-shaped landing gear is modeled by a linear spring and dashpot element. The air damper is added to the landing gear to increase the damping. The air damper consists of an air balloon that is connected to the outside via an orifice hole and the connecting pipe. A serial connection of spring, mass, and dashpot elements describes the air damper dynamic model. The simulation study is conducted to evaluate the effect of the landing gear parameters variation on the UAV dynamic response under shock and harmonic excitation. The maximum acceleration and displacement response of the UAV body under shock load is greatly affected by the air balloon cross-sectional area (Aef) and the stiffness of the U-shaped landing gear system (KL). The harmonic response of the UAV body is evaluated from the ratio between the UAV body displacement amplitude and the base excitation amplitude under harmonic excitation. It is shown that the air balloon cross-sectional area (Aef) and the connecting pipe length (lp) have a significant effect on the UAV mass displacement ratio. The experimental study is conducted to validate the simulation results. It is shown that the experimental data can verify the simulation results.

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.

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.

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.