• 대한의용생체공학회:의공학회지
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• 제45권2호
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• pp.57-65
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• 2024

Recently, several studies have been conducted to lower the cost of transport of human by adding external joint stiffness elements. However, it has not been clearly elucidated whether adaptation time is required for human subjects to adapt to the added external joint stiffness. In this study, carbon plates in the form of shoe midsoles were added to the metatarsophalangeal joint, and the lower limb joint torque and mechanical energy consumption were compared before and after a total of 5 sessions (2.5 weeks) of running. A total of 11 young healthy participants exhibited higher elastic energy storage in carbon plates in the fifth session compared to the first session, and lower power in the ankle joint. This suggests that a single training session may be insufficient to validate the efficiency effect of added joint stiffness, and the human body seems to increase the elastic energy stored in the assistive joint stiffness and its reutilization.

• 제어로봇시스템학회논문지
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• 제5권6호
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• pp.705-713
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• 1999

In this paper, we propose a new motion and force control methodology for constrained robots as an approach of hybrid discrete-continuous dynamical system. The hybrid dynamic system modeling of robotic manipulation tasks with constraints is presented, and the hybrid system control architecture for unconstrained and constrained motion system with parametric uncertainties is synthesized. The optimal reference stiffness of robot manipulator is generated by the hybrid automata as a discrete state system and the control behavior of constrained system which has poor modeling information and time-varying constraint function is improved by the constrained robots as a continuous state system. The performance of the proposed constrained motion control system is successfully evaluated via experimental studies to the constraint tasks.

• 제어로봇시스템학회논문지
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• 제6권8호
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• pp.703-709
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• 2000

This paper proposes a compliance control strategy for the robot manipulators accidentally interact-ing with an unknown environment. In this proposed method each in the diagonal stiffness matrix corre-sponding to the task coordinate in a Cartesian space is adaptively adjusted during contact along the corresponding axis based on the contact force with its environment. This method can be used for both unconstrained and constrained motions without any switching mechanism which often causes undesirable instability and/or vibrational motion of the end-effector. The experimental results show the effectiveness of the proposed method by employing a two link direct drive manipulator interacting with an unknown environment.

• 대한전기학회:학술대회논문집
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• 대한전기학회 1992년도 하계학술대회 논문집 A
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• pp.408-410
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• 1992

An adaptive hybrid position/force controller for constrained manipulator with uncertain dynamic model parameters and environment stiffness is presented. In this paper, the compliance frame model is constructed by independent positions and forces to be controlled. The adaptive controller based on this compliance frame dynamic model is designed. Lyapunov theory is used for controller design and Stability analysis.

• Smart Structures and Systems
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• 제13권2호
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• pp.219-233
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• 2014

In a companion paper, Pasala and Nagarajaiah analytically and experimentally validate the Adaptive Length Pendulum Smart Tuned Mass Damper (ALP-STMD) on a primary structure (2 story steel structure) whose frequencies are time invariant (Pasala and Nagarajaiah 2012). In this paper, the ALP-STMD effectiveness on a primary structure whose frequencies are time varying is studied experimentally. This study experimentally validates the ability of an ALP-STMD to adequately control a structural system in the presence of real time changes in primary stiffness that are detected by a real time observer based system identification. The experiments implement the newly developed Adaptive Length Pendulum Smart Tuned Mass Damper (ALP-STMD) which was first introduced and developed by Nagarajaiah (2009), Nagarajaiah and Pasala (2010) and Nagarajaiah et al. (2010). The ALP-STMD employs a mass pendulum of variable length which can be tuned in real time to the parameters of the system using sensor feedback. The tuning action is made possible by applying a current to a shape memory alloy wire changing the effective length that supports the damper mass assembly in real time. Once a stiffness change in the structural system is detected by an open loop observer, the ALP-STMD is re-tuned to the modified system parameters which successfully reduce the response of the primary system. Significant performance improvement is illustrated for the stiffness modified system, which undergoes the re-tuning adaptation, when compared to the stiffness modified system without adaptive re-tuning.

• 대한치과의사협회지
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• 제57권12호
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• pp.747-756
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• 2019

This paper reviews the adaptation accuracy and mechanical properties of currently used denture processing systems with base resin materials and introduces the latest research on the development of antimicrobial denture base resins. Poly(methyl methacrylate) has been successfully used as a dental denture base resin material by the compress-molding method and heat polymerization for a long time, but recently, new processing techniques, injection molding-methods or fluid-resin technique are also used for fabricating denture base. However, studies indicated that there was no difference between the injectionmolding and the conventional compression-molding method in terms of adaption accuracy of denture base. The fluid-resin fabrication and one injection-molding systems exhibited better adaptation accuracy than the other processing methods. Resin denture bases in the oral cavity may undergo midline fractures due to flexural fatigue from repeated masticatory loading. For those patients, impact resistant denture base resins are recommended to prevent denture fracture during service. Thermoplastic denture base resins can be helpful for patients suffering from allergic reaction to resin monomers with a soft-fit, however, thermoplastic resins with low stiffness can irritate gum tissues and accelerate abnormal alveolar ridge resorption. Moreover, due to low chemical durability in oral cavity, those should be used for a limited period of time.

• Smart Structures and Systems
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• 제21권3호
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• pp.359-371
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• 2018

Strong seismic events commonly cause large drift and deformation, and functionality failures in the superstructures. One way to prevent functionality failures is to design structures which are ductile and flexible through yielding when subjected to strong ground excitations. By developing forces that assist motion as "negative stiffness forces", yielding can be achieved. In this paper, we adopt the weakening and damping method to achieve a new approach to reduce all of the structural responses by further adjusting damping phase. A semi-active control system is adopted to perform the experiments. In this adaptation, negative stiffness forces through certain devices are used in weakening phase to reduce structural strength. Magneto-rheological (MR) dampers are then added to preserve stability of the structure. To adjust the voltage in MR dampers, an inverse model is employed in the control system to command MR dampers and generate the desired control forces, where a velocity control algorithm produces initial required control force. An extensive numerical study is conducted to evaluate proposed methodology by using the smart base-isolated benchmark building. Totally, nine control systems are examined to study proposed strategy. Based on the numerical results of seven earthquakes, the use of proposed strategy not only reduces base displacements, base accelerations and base shear but also leads to reduction of accelerations and inter story drifts of the superstructure. Numerical results shows that the usage of inverse model produces the desired regulated damping, thus improving the stability of the structure.

• 디지털융복합연구
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• 제13권9호
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• pp.515-521
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• 2015

본 연구에서는 우리는 평균 연령이 높은 제주 해녀의 경-대퇴 맥파 전도 속도와 발목-상완지표를 측정하여 찬물에서 산소의 보조 없이 채취활동을 하는 제주 해녀의 동맥 혈관의 경직도를 측정하였으며, 결과는 다음과 같다. 첫째, 경-대퇴 맥파 전도 속도는 동연령대의 일반여성보다 유의하게 낮게 나타났다. 둘째, 발목-상완지표(ABI)는 해녀와 일반여성 모두 정상범위 안에 포함되어 있었으며, 일반여성보다 해녀집단이 높은 경향을 보였다. 이러한 결과는 고령의 나이임에도 불구하고 장기간 침수활동을 통해 신체의 적응이 이미 완료된 상태로써 저온 및 높은 수압환경에 대한 적응이 완료된 신체상태이며, 아울러 높은 신체활동 수준으로 인하여 말초혈관저항이 고연령임에도 불구하고 감소되지 않았으며, 오히려 동연령 여성들보다 양호한 수준임을 확인할 수 있었다. 하지만 해녀들의 고령화는 여전히 진행되고 있는 중요한 현상이기에 동맥혈관경직도에 대한 관심과 향후의 지속적인 연구는 반드시 더 필요할 것으로 보인다.

• 한국산업융합학회 논문집
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• 제18권2호
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• pp.119-128
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• 2015

In this paper, we propose a new motion control technology to design robust control system of industrial robot. The system modeling of robotic manipulation tasks with constraints is presented, and the control architecture for unconstrained and constrained motion system with parametric uncertainties is synthesized. The optimal reference of robot manipulator is generated by the reference controller as a discrete state system and the control behavior of constrained system which has poor modeling information and time-invariant constraint function is improved motion control system is successfully evaluated by experiment to the desired tasks.

• 한국철도학회:학술대회논문집
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• 한국철도학회 2002년도 추계학술대회 논문집(II)
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• pp.807-819
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• 2002

The air spring is used in secondary suspension system for railway vehicle to reduce and absorb the vibration and noise. In this paper, the characteristics and durability test was conducted in laboratory by using servo hydraulic fatigue testing system to evaluate the reliability. And to guarantee the adaptation of this air spring, the ride comfort and air pressure variation were measured in train test. The experimental results show that the characteristics and durability of domestic development productions are obtained the good results and the stiffness of the air spring which had become 6 year over increased. Also, the dynamic characteristics of domestic and existing product agree well the results obtained.