Experiment Study and Machine Learning Prediction of Damping Performance of Ferrofluid Dynamic Vibration Absorber

Xiao Liu,Decai Li 한국자기학회 2022 Journal of Magnetics Vol.27 No.1

In this research, we study four influence factors of the damping performance of ferrofluid dynamic vibration absorber, as well as predict and optimize the damping performance by machine learning method. The vibration absorber in our research is based on the second order buoyancy principle, which consists of a non-magnetic container, a small amount of ferrofluid and a permanent magnet. The effects of the initial amplitude, the cone angle of the cover, the thickness of the gasket and the mass of the ferrofluid on the damping performance are investigated by experiments. Based on the experiment data, we use BP neural network to establish a prediction model between the four influence factors and the damping performance. The prediction error of damping efficiency predicted by BP neural network is mainly within ± 0.4%. Meanwhile, the determination coefficient R² of test data is 0.96242. The both indicate that BP neural network has a good performance in predicting the damping efficiency. Furthermore, we use the search algorithm to find the optimized values of each influence factor through the prediction model and the high damping efficiency is confirmed by experiments. Our work introduces machine learning into the field of vibration absorber designing, which provides an innovative method for the rapid design of high efficiency vibration absorber.

Analysis and Optimizing Method of Transient Performance for LCL-Based Grid-connected Inverter with Passive Damping

Minghan. Dong,Hao. Ma,Zhihong. Bai 전력전자학회 2019 ICPE(ISPE)논문집 Vol.2019 No.5

Dynamic currents and voltages in power electronic converters often exceed rating when changing load. In this way, this paper researches on optimizing transient performance of LCL-type gird-connected inverter systems. Resistor connected in series with capacitor as passive damping (RCSCPD), which is widely used to damp resonance of LCL filter, needs to choose an appropriate resistor to acquire accurate and fast transient performance. To meet this requirement, an approach is proposed for analyzing and improving transient performance. It shows that passive resistor could damp resonance and stable system. Limitation of RCSCPD, which could not optimize dominant transient response, is exhibited as well. Hence, mix damping (MD) is proposed to achieve the goal. It could eliminate overshoot and decrease settling time efficiently when comparing with RCSCPD. MD could configure the poles effectively without adding precision sensors because it uses grid current, which used in control loop, to realize active damping resistor. Experimental results based on single-phase LCL-type gird-connected inverter prototype are given to show optimizing effects of transient performance.

이중선형변환에 의한 극점배치기법을 이용한 H<SUB>∞</SUB> 제어기 설계

박원석(Park Wonsuk),박관순(Park Kwan-Soon),고현무(Koh Hyun-Moo) 대한토목학회 2007 대한토목학회논문집 A Vol.27 No.2A

이 논문에서는 목표감쇠성능(target damping performance)을 보장하는 H<SUB>∞</SUB> 제어기설계를 위하여, 이중선형변환(bilinear transformation)을 통한 극점배치기법(pole placement method)에 관하여 연구하였다. 이 연구에서는 단 자유도 진동계에서 이중선형 변환 매개 변수와 폐루프 시스템의 극 위치 사이의 상관 관계를 해석적으로 유도하고, 이로부터 목표 감쇠 성능을 보장하기 위한 극 위치 및 매개 변수 설정 방법을 제시한다. 이중선형 변환 및 역변환 과정에 사용되는 매개변수는 변환평면의 위치와 크기를 결정하게 되며, 이는 결과적으로 폐루프 시스템의 극점배치효과를 나타내게 되어 얻고자 하는 제어목적을 달성한다. 이 연구에서 제안한 방법으로 지진 하중을 받는 구조물의 능동제어시스템을 설계하고 수치모사 결과의 비교를 통하여 제시한 방법의 타당성을 확인한다. For the design of H<SUB>∞</SUB> controller which provide target damping performance, a pole placement method using bilinear transformation has been studied in this paper. The relationship between the parameters in the bilinear transformation and the pole locations of the closed loop system is analytically derived for a single degree of freedom system. And a method for of determination of the parameters and pole locations is proposed for guaranteeing the target damping performance. The parameters which are used in the bilinear transformation and the inverse transformation determine the size and the location of a transformed plane. This eventually leads to obtain a proper pole location in a complex plane, and as a result, target performance can be achieved. Example designs are performed by the proposed method with use of an earthquake excited structure and comparative numerical results are presented.

Numerical Study on the Improvement of the Motion Performance of a Light Buoy

손보훈,정세민 한국해양공학회 2020 韓國海洋工學會誌 Vol.34 No.2

A light buoy is equipped with lighting functions and navigation signs. Its shape and colors indicate the route to vessels sailing nearby in the daytime, with its lights providing this information at night. It also plays a role in notifying the presence of obstacles such as reefs and shallows. When a light buoy operates in the ocean, the visibility and angle of light from the lantern installed on the buoy changes, which may cause them to function improperly. Therefore, it is necessary for the buoy to have stable and minimal motions under given environmental conditions, mainly waves.In this study, motion analyses for a newly developed lightweight light-buoy in waves were performed to predict the motion performance and determine the effect of the developed appendages for improving the motion performance. First, free decay tests, including benchmark cases, were performed using computational fluid dynamics (CFD) to estimate the viscous damping coefficients, which could not be obtained using potential-based simulations. A comparison was made of the results from potential-based simulations with and without considering viscous damping coefficients, which were estimated using CFD. It was confirmed that the pitch and heave motions of the buoy became smaller when the developed appendages were adopted.

Design of supplemental viscous dampers in inelastic SDOF system based on improved capacity spectrum method

Li, Bo,Liang, Xing-Wen Techno-Press 2007 Structural Engineering and Mechanics, An Int'l Jou Vol.27 No.5

A simplified yet effective design procedure for viscous dampers was presented based on improved capacity spectrum method in the context of performance-based seismic design. The amount of added viscous damping required to meet a given performance objective was evaluated from the difference between the total demand for effective damping and inherent damping plus equivalent damping resulting from hysteretic deformation of system. Application of the method is illustrated by means of two examples, using Chinese design response spectrum and mean response spectrum. Nonlinear dynamic analysis results indicate that the maximum displacements of structures installed with supplemental dampers designed in accordance with the proposed method agree well with the given target displacements. The advantage of the presented procedure over the conventional iterative design method is also highlighted.

Landing Dynamic and Key Parameter Estimations of a Landing Mechanism to Asteroid with Soft Surface

Zhao, Zhijun,Zhao, JingDong,Liu, Hong The Korean Society for Aeronautical and Space Scie 2013 International Journal of Aeronautical and Space Sc Vol.14 No.3

It is of great significance to utilize a landing mechanism to explore an asteroid. A landing mechanism named ALISE (Asteroid Landing and In Situ Exploring) for asteroid with soft surface is presented. The landing dynamic in the first turning stage, which represents the landing performance of the landing mechanism, is built by a Lagrange equation. Three key parameters can be found influencing the landing performance: the retro-rocket thrust T, damping element damping $c_1$, and cardan element damping $c_2$. In this paper, the retro-rocket thrust T is solved with considering that the landing mechanism has no overturning in extreme landing conditions. The damping element damping c1 is solved by a simplified dynamic model. After solving the parameters T and $c_1$, the cardan element damping $c_2$ is calculated using the landing dynamic model, which is built by Lagrange equation. The validities of these three key parameters are tested by simulation. The results show a stable landing, when landing with the three estimated parameters T, $c_1$, and $c_2$. Therefore, the landing dynamic model and methods to estimate key parameters are reasonable, and are useful for guiding the design of the landing mechanism.

Landing Dynamic and Key Parameter Estimations of a Landing Mechanism to Asteroid with Soft Surface

Zhijun Zhao,JingDong Zhao,Hong Liu 한국항공우주학회 2013 International Journal of Aeronautical and Space Sc Vol.14 No.3

It is of great significance to utilize a landing mechanism to explore an asteroid. A landing mechanism named ALISE (Asteroid Landing and In Situ Exploring) for asteroid with soft surface is presented. The landing dynamic in the first turning stage, which represents the landing performance of the landing mechanism, is built by a Lagrange equation. Three key parameters can be found influencing the landing performance: the retro-rocket thrust T, damping element damping c₁, and cardan element damping c₂. In this paper, the retro-rocket thrust T is solved with considering that the landing mechanism has no overturning in extreme landing conditions. The damping element damping c₁ is solved by a simplified dynamic model. After solving the parameters T and c₁, the cardan element damping c₂ is calculated using the landing dynamic model, which is built by Lagrange equation. The validities of these three key parameters are tested by simulation. The results show a stable landing, when landing with the three estimated parameters T, c₁, and c₂. Therefore, the landing dynamic model and methods to estimate key parameters are reasonable, and are useful for guiding the design of the landing mechanism.

버추얼 기반 테일게이트 작동성 해석 평가기법 개발

김정환(Junghwan KIM),김영록(Youngrock KIM) 한국자동차공학회 2020 한국자동차공학회 학술대회 및 전시회 Vol.2020 No.11

Recently, there are a lot of developments of tailgate type vehicles such as SUV, hatchback and wagon. To develop tailgate type vehicles, design and evaluation of tailgate operating and durability performance were actively researching. However, in the field of analysis, proper response is difficult due to the lack of tailgate-related analysis techniques. The purpose of this study is to develop the virtual tailgate operating performance analysis evaluation techniques based on the tailgate gas lift damping coefficient On the study, more detailed gas lift damping coefficient was set up by compared with real-gas lift test results and tail gate operating performance’s consistency also was ensured by comparing with real test results. The development of operating performance analysis technique is expected to be the cornerstone for further planned tailgate gas lift strength analysis.

Performance-Based Seismic Design for High-Rise Buildings in Japan

Nakai, Masayoshi,Koshika, Norihide,Kawano, Kenichi,Hirakawa, Kiyoaki,Wada, Akira Council on Tall Building and Urban Habitat Korea 2012 International journal of high-rise buildings Vol.1 No.3

This paper introduces the outlines of review and approval processes, general criteria and usual practices taken in Japan for the seismic design of high-rise buildings. The structural calculations are based on time-history analyses followed by performance evaluations. This paper also introduces structural design of two high-rise buildings: one is a 100 m high reinforced concrete residential building, and the other is a 300 m high steel building for mixed use.

Performance-based Wind-resistant Design for High-rise Structures in Japan

Nakai, Masayoshi,Hirakawa, Kiyoaki,Yamanaka, Masayuki,Okuda, Hirofumi,Konishi, Atsuo Council on Tall Building and Urban Habitat Korea 2013 International journal of high-rise buildings Vol.2 No.3

This paper introduces the current status of high-rise building design in Japan, with reference to some recent projects. Firstly, the design approval system and procedures for high-rise buildings and structures in Japan are introduced. Then, performance-based wind-resistant design of a 300 m-high building, Abeno Harukas, is introduced, where building configuration, superstructure systems and various damping devices are sophisticatedly integrated to ensure a higher level of safety and comfort against wind actions. Next, design of a 213 m-high building is introduced with special attention to habitability against the wind-induced horizontal motion. Finally, performance-based wind-resistant design of a 634 m-high tower, Tokyo Sky Tree, is introduced. For this structure, the core column system was adopted to satisfy the strict design requirements due to the severest level of seismic excitations and wind actions.