• 한국공간구조학회논문집
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• 제8권4호
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• pp.73-80
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• 2008

본 논문의 목적은, LQR 제어이득의 효율적 산정에 의한 지진하중을 받는 빌딩 구조물의 능동지진제어를 위하여 능동텐던 장치를 적용한 구조물의 지진응답제어를 위한 최적화 방법을 제시한 것이다. 텐던을 이용한 구조물 지진응답제어 문제의 정식화를 위해 Ricatti 폐회로 제어이론 및 위상보정에 의한 시간지연현상을 도입하였으며, 상태방정식의 해를 산정하기 위해 전달 행렬을 이용한 수치해석법을 이용 사다리꼴적분법에 의해 상태벡터의 해를 산정하였다. 성능지수의 최적화를 위해, 최소 가중행렬비를 설계변수로, IBC 2000의 허용층간변위 규정과 텐던의 최대제어력을 제약조건으로 하여, SUMT 기법에 의해 최적 해를 산정토록 최적제어 프로그램을 개발하였다. 8층 빌딩구조물에 대한 적용 예에서, 최적제어를 적용한 시스템이 비제어 시스템에 비해 층간제어효과가 우수하고, 일정 가중행렬비 적용 제어시스템에 비해 낮은 성능지수가 요구되었다.

• Structural Engineering and Mechanics
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• 제61권3호
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• pp.347-357
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• 2017

The applications of active control is being more popular nowadays. Several control algorithms have been developed to determine optimum control force. In this paper, a Chaotic Particle Swarm Optimization (CPSO) technique, based on Logistic map, is used to compute the optimum control force of active tendon system. A chaotic exploration is used to search the solution space for optimum control force. The response control of Multi-Degree of Freedom (MDOF) shear buildings, equipped with active tendons, is introduced as an optimization problem, based on Instantaneous Optimal Active Control algorithm. Three MDOFs are simulated in this paper. Two examples out of three, which have been previously controlled using Lattice type Probabilistic Neural Network (LPNN) and Block Pulse Functions (BPFs), are taken from prior works in order to compare the efficiency of the current method. In the present study, a maximum allowable value of control force is added to the original problem. Later, a twenty-story shear building, as the third and more realistic example, is considered and controlled. Besides, the required Central Processing Unit (CPU) time of CPSO control algorithm is investigated. Although the CPU time of LPNN and BPFs methods of prior works is not available, the results show that a full state measurement is necessary, especially when there are more than three control devices. The results show that CPSO algorithm has a good performance, especially in the presence of the cut-off limit of tendon force; therefore, can widely be used in the field of optimum active control of actual buildings.

• Structural Engineering and Mechanics
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• 제69권3호
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• pp.307-315
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• 2019

This paper proposes a chattering-free sliding mode control (CFSMC) method for seismically excited structures. The method is based on a fuzzy logic (FL) model applied to smooth the control force and eliminate chattering, where the switching part of the control law is replaced by an FL output. The CFSMC is robust and keeps the advantages of the conventional sliding mode control (SMC), whilst removing the chattering and avoiding the time-consuming process of generating fuzzy rule basis. The proposed method is tested on an 8-story shear frame equipped with an active tendon system. Results indicate that the new method not only can effectively enhance the seismic performance of the structural system compared to the SMC, but also ensure system stability and high accuracy with less computational cost. The CFSMC also requires less amount of energy from the active tendon system to produce the desired structural dynamic response.

• Smart Structures and Systems
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• 제18권1호
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• pp.31-52
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• 2016

The paper first reviews the theory of active tendon control with decentralized Integral Force Feedback (IFF) and collocated displacement actuator and force sensor; a formal proof of the formula giving the maximum achievable damping is provided for the first time. Next, the potential of the control strategy for the control of suspension bridges with active stay cables is evaluated on a numerical model of an existing footbridge; several configurations are investigated where the active cables connect the pylon to the deck or the deck to the catenary. The analysis confirms that it is possible to provide a set of targeted modes with a considerable amount of damping, reaching ${\xi}=15%$. Finally, the control strategy is demonstrated experimentally on a laboratory mock-up equipped with four control stay cables equipped with piezoelectric actuators. The experimental results confirm the excellent performance and robustness of the control system and the very good agreement with the predictions.

• Smart Structures and Systems
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• 제25권2호
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• pp.229-240
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• 2020

In this research, toggled actuator forces were examined. For achieving to this object, an actuator was installed in a toggle pattern in a S.D.O.F frame and actuator forces were investigated thru a numerical analysis process. Within past twenty years, researchers tried to use strong bracing systems as well as huge dampers to stabilize tall buildings during intensive earthquakes. Eventually, utilizing of active control systems containing actuators to counter massive excitations in structures was emerged. However, the more powerful earthquake excitations, the more robust actuators were required to be installed in the system. Subsequently, the latter process made disadvantage to the active control system due to very high price of the robust actuators as well as their large demands for electricity. Therefore, through a numerical process (Part I), influence of toggled actuator pattern was investigated. The algorithm used in the system was LQR and ATmega328 was selected as a control platform. For comparison, active tendon control system was chosen. The final results show clearly that using the toggle pattern mitigates the required actuator forces enormously leading to deploy much lighter actuators.

• 대한의용생체공학회:의공학회지
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• 제32권2호
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• pp.93-104
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• 2011

The purpose of this study was to investigate lower-limb joint torque of the two groups as it changed by somatosensory stimulation during the descent down three stairs of different heights and to describe the difference between the two groups, which are young people group and elderly people group. Subjects of each groups climbed down a stair at four stimulation conditions, which are non-stimulation, tibialis anterior tendon stimulation, achilles tendon stimulation, tibialis anterior - achilles tendon stimulation. Motion capture data were collected using 3D optoelectric motion tracking system that utilizes active infrared LEDs, near infrared sensor and force plate. The obtained motion capture data was used to build 3D computer simulation model. The results show that lower-limb joint torque of the two groups changed with somatosensory stimulation as they descended the stairs and the joint torque of the two groups differed from each other.

• 한국소음진동공학회:학술대회논문집
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• 한국소음진동공학회 2000년도 추계학술대회논문집
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• pp.282-286
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• 2000

In this paper, magneto-rheological(MR) damper is studied for vibration control of large infra structures under earthquake. Generally, active control devices need a large control force and a high power supply system to reduce the vibration effectively. Large and miss tuned control force may induce the dangerous situation such that the generated large control force acts to amplify the structural vibration. Recently, to overcome the weaknesses of the active control, the semi-active control method is suggested by many researchers. Semi-active control uses the passive control device of which the characteristics can be modified. Control force of the semi-active device is not generated from the actuator with power supply. It is generated as a dynamic reaction force of the device same as in the passive control case, so the control system is inherently stable and robust. Unlike the case of passive control, control force of semi-active control is adjusted depending on the measured response of the structure, so the vibration can be reduced more effectively against various unknown environmental loads. Magneto-rheological(MR) damper is one of the semi-active devices. Dynamic characteristics of the MR material can be changed by applying the magnetic fields. So the control of MR damper needs only small power. Response time of MR to the input voltage is very short, so the high performance control is possible. MR damper has a high force capacity so it is adequate to the vibration control of large infra structure. Because MR damper has a nonlinear property, normal control method used in active control may not be effective. Clipped optimal control, modified bang-bang control etc. have been suggested to MR damper by many researchers. In this study, sliding mode fuzzy control(SMFC) is applied to MR damper. Genetic algorithm is used for the controller tuning. To verify the applicability of MR damper and suggested algorithm, numerical simulation on the aseismic control is carried out. Simulation model is three-story building structure, which was used in the paper of Dyke, et al. The control performance is compared with clipped optimal control. The present results indicate that the SMFC algorithm can reduce the earthquake-induced vibration very effectively.

• Structural Engineering and Mechanics
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• 제10권6호
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• pp.517-532
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• 2000

A direct output feedback control scheme was recently proposed by the authors for single-story building structures resting on flexible soil body. In this paper, the control scheme is extended to mitigate the seismic responses of multi-story buildings. Soil-structure interaction is taken into account in two parts: input at the soil-structure interface/foundation and control algorithm. The former reflects the effect on ground motions and is monitored in real time with accelerometers at foundation. The latter includes the effect on the dynamic characteristics of structures, which is formulated by modifying the classical linear quadratic regulator based on the fundamental mode shape of the soil-structure system. Numerical result on the study of a $\frac{1}{4}$-scale three-story structure, supported by a viscoelastic half-space of soil mass, have demonstrated that the proposed algorithm is robust and very effective in suppressing the earthquake-induced vibration in building structures even supported on a flexible soil mass. Parametric studies are performed to understand how soil damping and flexibility affect the effectiveness of active tendon control. The selection of weighting matrix and effect of soil property uncertainty are investigated in detail for practical applications.

• 대한골관절종양학회지
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• 제2권1호
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• pp.8-17
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• 1996

The purpose of this study is a comparative evaluation of range motion, especially extension deficit between the group of total patellectomy and that of intact patella, after reconstruction of the patellar tendon in the prosthetic replacement of a proximal tibia. Between 1990 and 1994, 15 patients who had a primary malignancy on proximal tibia were operated on. All patients were evaluated clinically and radiographically. Two patients were excluded because one had a deep infection treated with arthrodesis of the knee and the other was a composite allograft. The mean follow-up of the 13 patients was 27 months(15-47), including 10 osteosarcomas, 1 chondrosarcoma, 1 malignant fibrous histiocytoma and 1 malignant giant cell tumor. Eleven patients had a resection of the proximal tibia and 2 had an extracapsular total knee resection with distal femur. Reconstruction of the defect was done in 8 cases with a custom-made Link Endo-Model Total Rotation Knee Joint Prosthesis, and in 5 with How Medica Modular Resection System (HMRS). We used two methods to reconstruct the ligamentum patellae. Fixation of the patellar tendon to the prosthesis only with suturing and/or stapling(group SS) was done in 7. Transposition of gastrocnemius muscle to enhance fixation and to cover the prosthesis(group TG) was done in 6. Regardless of fixation methods, total patellectomy was done in 5 either to lengthen the patellar tendon or to make primary skin closure easier or for both. In 8 cases, patella was left intact or resurfaced with polyethylene prosthesis. Active extension was measured while the patient was in a sitting position. There is no statistically meaningful difference in terms of extension deficit (Wilcoxon rank test, p=0.8800) between patellectomy group and intact patella group, and between group of fixation only with suturing and that of gastrocnemius transposition. Two cases of extension deficit over 30 degree were seen in group SS and in the group of intact patella. Conclusively, total patellectomy could be an option without increasing the risk of extension deficit when primary skin closure is difficult or patellar tendon is a little bit short to be fixed. There is no rating in the Enneking system of functional evaluation that this finding into consideration.

• 대한골관절종양학회지
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• 제3권1호
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• pp.18-25
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• 1997

Prosthetic replacement is one of the most common methods of reconstruction after resection of malignant tumor around the knee. Gait analysis provides a relative objective data about the gait function of patients with prosthesis. The purpose of this study was to compare the gait pattern of the patients who underwent limb salvage surgery with prosthesis for distal femur and that of patients with prosthesis for proximal tibia. This study included ten patients (4 males, 6 females, mean age 22.7 years, range 14-36) who underwent a wide resection and Kotz hinged modular reconstruction prosthesis replacement and six normal adult(Control). The site of bone tumor was the distal femur (Group 1) in six patients and proximal tibia (Group 2) in 4 patients. The follow-up period ranged from 15 to 82 months (mean : 33 months). The evaluation consisted of clinical assessment, radiographic assessment, gait analysis using VICON 370 Motion Analysis System. The gait analysis included the linear parameters such as, walking velocity, cadence, step length, stride length, stance time, swing time, single support and double support time and the three-dimensional kinematics (joint rotation angle, velocity of joint rotation) of ankle, knee, hip and pelvis in sagittal, coronal and transverse plane. For the kinetic evaluation, the moment of force (unit: Nm/kg) and power (unit: Watt/kg) of ankle, knee and hip joint in sagittal, coronal and transverse plane. In the linear parameters, cadence, velocity, step time and single support were decreased in both group 1 and group 2 compared with control. Double support decreased in group 2 compared with control significantly(p<.05). In contrast to our hypothesis, there was no significant difference between group 1 and group 2. In Kinematics, we observed significant difference (p<.05) of decreased knee flexion in loading response (G2