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모듈형 시스템 설계를 위한 플러그인 디지털 해석모델의 통계적 보정 및 검증 기술 최신 동향과 전망
윤병동(Byeng D. Youn),윤헌준(Heonjun Yoon),박정호(Jungho Park),이규석(Guesuk Lee),오현석(Hyunseok Oh) 대한기계학회 2014 대한기계학회 춘추학술대회 Vol.2014 No.11
As engineered products become more complex with a shorter development cycle, many leading conglomerates have introduced the concept of modular system design. With this trend, the role of virtual testing using a computer-aided engineering (CAE) model has increased. However, it is challenging to build a high-fidelity CAE model for plug-in digital analysis of a modular system due to the interactions of modules and joints as well as the complicated nature of the full system. One possible solution is statistical model calibration and validation which can improve and ensure the predictive capability of a CAE model. The purpose of this study is to review the current trends and future directions in model calibration and validation for plug-in digital analysis. Three main areas are focused: (i) correlation metric, (ii) model calibration, and (iii) model validation. This paper attempts to provide insights for adopting an appropriate technique in model calibration and validation for a modular system design.
Resilience Allocation for Resilient Engineered System Design
윤병동(Byeng D. Youn),후차오(Chao Hu),왕핑펭(Pingfeng Wang),윤정택(Joungtaek Yoon) 제어로봇시스템학회 2011 제어·로봇·시스템학회 논문지 Vol.17 No.11
Most engineered systems are designed with high levels of system redundancies to satisfy required reliability requirements under adverse events, resulting in high systems’ LCCs (Life-Cycle Costs). Recent years have seen a surge of interest and tremendous advance in PHM (Prognostics and Health Management) methods that detect, diagnose, and predict the effects of adverse events. The PHM methods enable proactive maintenance decisions, giving rise to adaptive reliability. In this paper, we present a RAP (Resilience Allocation Problem) whose goal is to allocate reliability and PHM efficiency to components in an engineering context. The optimally allocated reliability and PHM efficiency levels serve as the design specifications for the system RBDO (Reliability-Based Design Optimization) and the system PHM design, which can be used to derive the detailed design of components and PHM units. The RAP is demonstrated using a simplified aircraft control actuator design problem resulting in a highly resilient actuator with optimally allocated reliability, PHM efficiency and redundancy for the given parameter settings.
비정상 랜덤 진동 조건에서 압전 에너지 수확 장치의 시변 상관 다변량 응답 특성 분석
윤헌준(Heonjun Yoon),김미소(Miso Kim),박춘수(Choon-Su Park),윤병동(Byeng D. Youn) 대한기계학회 2014 대한기계학회 춘추학술대회 Vol.2014 No.11
The output performances, such as the tip displacement and electric power, of a piezoelectric energy harvester (PEH) are produced as a correlated multivariate response due to the electromechanical coupling. Furthermore, since most ambient vibrations in nature are inherently random and non-stationary, the tip displacement and electric power may also randomly change with time. However, there has been no attempt to investigate the temporal correlated multivariate response of the PEH under a non-stationary random vibration. Therefore, this study aims at statistically comparing the stochastic analytical predictions and experimental observations on the tip displacement and electric power under a nonstationary random vibration. In the stochastic analytical prediction, the output performances were calculated based on the time-varying power spectral density estimated by the smoothed pseudo Wigner-Ville distribution. In the experimental setup, the input acceleration signal was induced by an electrostatic shaker and its amplitude and excitation frequency were randomly modulated. The weighted integrated factor was used as a correlation metric for the temporal response, which calculates an error between stochastic analytical predictions and experimental observations under one experimental setting. Finally, T-pooling metric was used to integrate the evidence from all relevant data of the correlated multivariate response under various experimental settings into a single aggregate measure for assessing the global agreement.
윤헌준(Heonjun Yoon),윤병동(Byeng D Youn),김흥수(Heung Soo Kim) 대한기계학회 2015 대한기계학회 춘추학술대회 Vol.2015 No.11
Although tremendous advances have been made in designing a piezoelectric energy harvester to maximize output power, the research on reliability assessment for durability has been stagnant due to the complicated nature of the multiple failure events of the piezoelectric energy harvester. Furthermore, no clear understanding on statistical coupling between the durability and energy conversion efficiency under uncertainty. This study thus addresses system reliability analysis on the multiple failure events of the piezoelectric energy harvester such as (i) fatigue failure, (ii) output voltage drop, and (iii) output power drop under uncertainty. First, based on the Kirchhoff plate theory, the electromechanicallycoupled analytical model is employed to analyze the electromechanical behaviors of the piezoelectric energy harvester. In calculation of the bending stress of the piezoelectric patch, the voltage-induced stress is taken into consideration. Second, the Monte Carlo simulation (MCS) is implemented for uncertainty propagation analysis. Finally, system reliability analysis is performed by using the Generalized Complementary Intersection method (GCIM).
심장 내 심박 조율기 자가 구동을 위한 나노스케일 혈압 에너지 하베스팅의 수학적 해석 모델
윤헌준(Heonjun Yoon),윤병동(Byeng D. Youn) 대한기계학회 2016 대한기계학회 춘추학술대회 Vol.2016 No.12
Perpetual progress in nanofabrication enables the miniaturization of implantable medical devices, such as a pacemaker. This makes it possible to fit the pacemaker in a tiny capsule which can be implanted intravenously in a heart without leads. Nanoscale energy harvesting from human blood pressure has attracted enormous interests as a promising solution to permanently power a leadless intra-cardiac pacemaker. With this purpose in mind, we propose a multiphysics analytical model to predict the output voltage generated by a nanoscale dielectric plate considering the flexoelectricity, the surface effect, and the nonlocal effects. The flexoelectricity concerns a linear coupling between the strain gradient and the polarization. The existence of the strain gradient locally breaks the inversion symmetry, thereby rendering the formation of dipole moments in all dielectrics. The Kirchhoff plate theory is applied to analyze the bending behavior of the nanoscale dielectric plate. Based on the Gurtin-Murdoch theory, the surface elasticity is taken into consideration by the generalized Young-Laplace equations with non-classical boundary conditions. Hamilton’s principle is used to derive the differential equation of motion. The electrical circuit equation is derived by substituting the piezoelectric constitutive relation involving the higher-order gradient (nonlocal) terms into Gauss’s law. Finally, the output voltage is explicitly obtained under human blood pressure with the low-frequency variation of 1 Hz.