• 소음진동
• /
• 제8권4호
• /
• pp.715-722
• /
• 1998

An investigation into the stochastic bifurcation and response statistics of an autoparameteric system under broad-band random excitation is made. The specific system examined is a spring-pendulum system with internal resonance, which is known to be a good model for a variety of engineering systems, including ship motions with nonlinear coupling between pitching and rolling motions. The Fokker-Planck equations is used to genrage a general first-order differential equation in the dynamic moment of response coordinates. By means of the Gaussian and non-Gaussian closure methods the dynamic moment equations for the random responses of the system are reduced to a system of autonomous ordinanary differential equations. In view of equilibrium solutions of this system and their stability we examine the stochastic bifurcation and response statistics. The analytical results are compared with results obtained by Monte Carlo simulation.

• Journal of Mechanical Science and Technology
• /
• 제18권12호
• /
• pp.2225-2235
• /
• 2004

An observatory termed 'Steel Swing' has been developed, where a 15000 kg pendulum is hanged from a stiff steel frame. A building element can be tested after inserted between the pendulum and the frame. Free vibration, forced vibration tests and earthquake monitoring were performed on an exposed-type steel column base. The response records monitored during natural earthquakes were used to identify the vibration property of the specimen. Identified system gain was approximated by a theoretical gain of linear SDOF system, and the response calculated based on such a linear system agrees with the monitored response fairly well. This research technique can be applied to check the behaviors of new materials and new details of connections and the safety of non-structural elements as well.

• 한국자동차공학회논문집
• /
• 제6권6호
• /
• pp.276-284
• /
• 1998

Optimum design of bumper beam is investigated using nonlinear CAE structural analysis techniques.In order to minimize its weight, while enhancing structural performances, bumper beam structural analyses were carried out to produce optimum section. Model is composed of bumper beam and stay. First, considering FMVSS safety standard, static strength and energy absorbing capability were estimated for several competitive bumpers through pendulum static analysis, and most promising section was chosen. Next, to ensure dynamic crashworthinesss performance for center pole impact was evaluated for the bumper beam with chosen section through pendulum static analysis, referring to DHS bumper dynamic impact standard. Finally, 2.5 mph bumper beam was designed and its structural performance was estimated. Through this investigation, an optimized bumper beam section with less weight of 20% while maintaining almost equal carshworthiness, compared with a conventional bumper beam section which proved its impact crashworthiness by experiments, was developed.

• 한국산업융합학회 논문집
• /
• 제4권2호
• /
• pp.133-139
• /
• 2001

The nonlinear response statistics of an spring-pendulum system with internal resonance under narrow band random excitation is investigated analytically- The center frequency of the filtered excitation is selected to be close to natural frequency of directly excited spring mode. The Fokker-Planck equations is used to generate a general first-order differential equation in the dynamic moment of response coordinates. By means of the Gaussian closure method the dynamic moment equations for the random responses of the system are reduced to a system of autonomous ordinary differential equations. The nonlinear phenomena, such as jump and multiple solutions, under narrow band random excitation were found by Gaussian closure method.

• Wind and Structures
• /
• 제32권4호
• /
• pp.341-354
• /
• 2021

Articulated towers are one of the class of compliant offshore structures that freely oscillates with wind and waves, as they are designed to have low natural frequency than ocean waves. The present study deals with the dynamic response of a double-pendulum articulated tower under hydrodynamic and aerodynamic loads. The wind field is simulated by two approaches, namely, single-point and multiple-point. Nonlinearities such as instantaneous tower orientation, variable added mass, fluctuating buoyancy, and geometrical nonlinearities are duly considered in the analysis. Hamilton's principle is used to derive the nonlinear equations of motion (EOM). The EOM is solved in the time domain by using the Wilson-θ method. The maximum, minimum, mean, and standard deviation and salient power spectral density functions (PSDF) of deck displacement, bending moment, and central hinge shear are drawn for high and moderate sea states. The outcome of the analyses shows that tower response under multiple-point wind-field simulation results in lower responses when compared to that of single-point simulation.

• 한국지능시스템학회논문지
• /
• 제21권2호
• /
• pp.192-197
• /
• 2011

본 논문은 선형 상태 관측기의 성능 및 실용화 검증을 위하여 도립진자 시스템의 출력 피드백 제어 실험을 수행하였다. 도립진자 시스템으로는 (주)셈웨어의 CEM-IP-01를 실험에 사용하였다. 동역학 해석을 위하여 라그랑지안 방정식 및 자코비안 선형화 방법을 이용하였고, 모의실험을 통하여 일반 상태 피드백 제어기의 출력 응답과 제안된 제어기의 출력 응답을 먼저 비교 분석하였다. 마지막으로 실제 도립진자 시스템에 적용함으로써 제어기 구현에서 발생하는 문제점을 파악하고 해결함으로써 실용화 가능성을 직접 확인하였다.

• 한국멀티미디어학회논문지
• /
• 제19권8호
• /
• pp.1587-1596
• /
• 2016

This paper presents an interactive locomotion controller using motion capture data and inverted pendulum model. Most of the data-driven character controller using motion capture data have two kinds of limitation. First, it needs many example motion capture data to generate realistic motion. Second, it is difficult to make natural-looking motion when characters navigate dynamic terrain. In this paper, we present a technique that uses dimension reduction technique to motion capture data together with the Gaussian process dynamical model (GPDM), and interpolates the low-dimensional data to make final motion. With the low-dimensional data, we can make realistic walking motion with few example motion capture data. In addition, we apply the inverted pendulum model (IPM) to calculate the root trajectory considering the real-time user input upon the dynamic terrain. Our method can be used in game, virtual training, and many real-time applications.

• 한국정밀공학회지
• /
• 제19권10호
• /
• pp.163-170
• /
• 2002

The dynamic model of a high-speed vacuum circuit breaker mechanism with spring-actuated cam and linkage is derived to simulate the high-speed closing and opening operations. Its validation for an analysis of high-speed motion behavior is checked through experiments. The characteristics of the friction on the camshaft are investigated using the nonlinear pendulum experiment. The parameters of the friction model are estimated using the optimization technique. The analysis exhibits that the friction of the pendulum depends on stick-slip, Stribeck effect and viscous damping. Comparing simulation results with actual responses using a high-speed camera, the appropriateness of derived dynamic models for the rapid closing and opening operations is shown. The spring motion, which has much influence on the closing responses, is observed.

• 소음진동
• /
• 제3권3호
• /
• pp.231-243
• /
• 1993

The dynamic characteristics of two types of mathematical models for a rigid body suspension system are analyzed and compared in this paper. One is a linearized model which is commonly used in the engine mount system analysis, the other is a nonlinear model which usually applied to the pendulum type system. The typical 3 d.o.f's mathematical model, for convenience, is chosen as a simulation model, because it has fundamental dynamic characteristics of suspension system. Time responses and unbalance responses of the rigid body, transmitted forces and torques are simulated by using the mathematical model. From the results of computer simulation, it is approved that he nonlinear model is valid and the linearized model gives erroneous results in the case of the pendulum type suspension system. In addition, in this study the effects of design change on the dynamic characteristics of the suspension system are investigated. Mount locations, mount angles, lengths, stiffness and damping coefficients of suspension bars are chosen as design parameters.

• 제어로봇시스템학회논문지
• /
• 제10권12호
• /
• pp.1210-1216
• /
• 2004

This paper deals with a human-like gait generation of a biped robot with a balancing weight of an inverted pendulum type by using genetic algorithm. The ZMP (Zero Moment Point) is the most important index in a biped robot's dynamic walking stability. To perform a stable walking of a biped robot, a balancing motion is required according to legs' trajectories and a desired ZMP trajectory. A dynamic equation of the balancing motion is nonlinear due to an inverted pendulum type's balancing weight. To solve the nonlinear equation by the FDM (Finite Difference Method), a linearized model of equation is proposed. And GA (Genetic Algorithm) is applied to optimize a human-like balancing motion of a biped robot. By genetic algorithm, the index of the balancing motion is efficiently optimized, and a dynamic walking stability is verified by the ZMP verification equation. These balancing motion are simulated and experimented with a real biped robot IWR-IV. This human-like gait generation will be applied to a humanoid robot, at future work.