• Structural Engineering and Mechanics
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• 제46권5호
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• pp.673-693
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• 2013

This paper presents a systematic design and training procedure for the feed-forward back-propagation neural network (NN) modeling of both forward and inverse behavior of a rotary magnetorheological (MR) damper based on experimental data. For the forward damper model, with damper force as output, an optimization procedure demonstrates accurate training of the NN architecture with only current and velocity as input states. For the inverse damper model, with current as output, the absolute value of velocity and force are used as input states to avoid negative current spikes when tracking a desired damper force. The forward and inverse damper models are trained and validated experimentally, combining a limited number of harmonic displacement records, and constant and half-sinusoidal current records. In general the validation shows accurate results for both forward and inverse damper models, where the observed modeling errors for the inverse model can be related to knocking effects in the measured force due to the bearing plays between hydraulic piston and MR damper rod. Finally, the validated models are used to emulate pure viscous damping. Comparison of numerical and experimental results demonstrates good agreement in the post-yield region of the MR damper, while the main error of the inverse NN occurs in the pre-yield region where the inverse NN overestimates the current to track the desired viscous force.

• 전력전자학회논문지
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• 제7권5호
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• pp.413-418
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• 2002

본 연구는 관성의 변화에 견실한 피드포워드 적응 위치제어기를 제안한다. 제안된 피드포워드 적응 위치제어기는 PI 위치제어기에 피드포워드와 기준모델 적응제어기를 추가한 구조를 가진다. 제어기의 특징은 과도상태에서 적응제어기가 위치오차와 기준모델의 속도 정보를 이용하여 피드포워드 이득을 조정한다. 이것은 과도응답 특성을 향상시키고, 정상상태의 수렴 시간을 개선시킨다. 위치 오차에 속도의 정보를 받아들여 기존의 Pl 위치제어 및 기준모델 적응제어에 비하여 속응성이 우수하다. 그리고, 적응제어기에 규준화 함수를 사용하여 입력크기에 대해 출력신호가 일정한 응답특성을 가지도록 하였다. 시뮬레이션을 통하여 제안된 피드포워드 적응 위치제어기 동작의 타당성을 보였다.

• 한국정밀공학회지
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• 제16권5호통권98호
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• pp.200-208
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• 1999

The statics relation of the Stewart platform has been investigated from the viewpoint of the forward and inverse force transmission analyses. Two eigenvalue problems corresponding to the forward and inverse force transmission analyses have been formulated. The forward force transmission analysis is to determine the ranges of the magnitudes of the force and moment generated at the end-effector for the given magnitude of linear actuator forces. In reverse order, the inverse force transmission analysis is to find the range of the magnitude of actuator forces for the given ranges of the magnitudes of the force and moment at the end-effector. The inverse force transmission analysis is important since it can provide a designer with a valuable information about how to choose the linear actuators. It has been proved that two eigenvalue problems have a reciprocal relation, which implies that solving either of the eigenvalue problems may complete the forward/inverse force transmission analysis. A numerical example has been also presented.

• The Journal of Korean Physical Therapy
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• 제17권3호
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• pp.413-420
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• 2005

The purpose of this study was to determine differences of balance performance to upright standing, forward bending posture, and sudden load during forward bending posture in subjects with and without a history of low back pain. A study was conducted on 8 subjects with low back pain and 13 healthy subjects. Dynamic Balance System was used to measure the postural sway index, left-right sway index, and anterior-posterior sway index on balance performance. There were no differences between subject groups on balance performance during upright standing. Balance performance was increased in forward bending posture and decreased in sudden load during forward bending posture in subjects with low back pain. These results suggest that subjects with low back pain demonstrated increased activity and decreased reaction times of trunk muscles.

• 한국지능시스템학회논문지
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• 제13권6호
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• pp.743-748
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• 2003

In this research, we propose a mechanism to develop an inference engine and expert systems based on relational database (RDB) and SQL (structured query language). Generally, former researchers had tried to develop an expert systems based on text-oriented knowledge base and backward/forward (chaining) inference engine. In these researches, however, the speed of inference was remained as a tackling point in the development of agile expert systems. Especially, the forward inference needs more times than backward inference. In addition, the size of knowledge base, complicate knowledge expression method, expansibility of knowledge base, and hierarchies among rules are the critical limitations to develop an expert system. To overcome the limitations in speed of inference and expansibility of knowledge base, we proposed a relational database-oriented knowledge base and forward inference engine. Therefore, our proposed mechanism could manipulate the huge size of knowledge base efficiently. and inference with the large scaled knowledge base in a short time. To this purpose, we designed and developed an SQL-based forward inference engine using relational database. In the implementation process, we also developed a prototype expert system and presented a real-world validation data set collected from medical diagnosis field.

• 한국군사과학기술학회지
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• 제13권6호
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• pp.976-981
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• 2010

A soft-recoil or FOOB (Fire-Out-Of-Battery) system can reduce the recoil force considerably. Its firing sequency is different from that of a conventional or FIB (Fire-In-Battery) system. In FOOB system, the gun is latched and preloaded in its battery position prior to firing. When unlatched, the gun is accelerated to the forward direction and then the forward momentum of the recoil part is generated. Since this momentum reduces the recoil impulse, the recoil force will decrease significantly. When designing the soft-recoil system it is important to design the forward momentum profile of a recoiling part. In the present study, the method to determine the forward momentum has been studied and its optimum value has been obtained theoretically. The numerical simulation of the soft-recoil system is performed to show that the present soft-recoil system works functionally well.

• 제어로봇시스템학회논문지
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• 제6권7호
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• pp.559-567
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• 2000

This paper proposes simple and practical methods in order to overcome complex formulation and heavy computational burden of the forward kinematics of 6 앨 3-6 type parallel manipulators. Three ap-proaches for the forward kinematics are presented : one extra sensor a modified structure and novel numerical method. The proposed methods are applied to the forward kinematics of a new 6 앨 parallel manipulator with special geometry that has three internal links three external links and a moving platform of a cone shape. The proposed methods use three tetrahedrons for finding the position and orientation vector of the moving platform. The main advantages of the appraches using tetrahedrons are to abbreviate the formulation to easily find so-lutions of the forward kinematics and to be able to practically control of the manipulator in real time.

• Physical Therapy Rehabilitation Science
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• 제10권3호
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• pp.337-342
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• 2021

Objective: Forward head posture can caused by deformation of structures and soft tissues around the neck, which has an uncomfortable effect on daily life as well as functional disorders of the neck. However, studies related to direct forward head posture, neck function, and quality of life have not yet been conducted. Therefore, the purpose of this study is to investigate the effect of improving the forward head posture on the function of the neck and to examine the change in the quality of life. Design: A randomized controlled trial Methods: The participants were 41 adults (22.17±2.67 years) recruited and redivided randomly into two group (Biofeedback, BFG vs. Control). The Biofeedback group was proceeded according to the over load principle through 4 steps. (n=21). The control (n=20) was not applied after TENS padding was applied and 20 minute. This study was conducted three times a week for a total of four weeks. Results: Forward head posture for showed significant improvement in the results in the craneocervical angle (p<0.05, 95% CI: 0.130, 2.858). In neck disability index more significant improvement in BFG than group (p<0.05, 95% CI: 14.346, 17.825), and BFG showed significant increased in the results in the Quality of life (p<0.05, 95% CI: 0.392, 9.549) Conclusions: This study suggected that forward head posture treatment and effective for neck function and quality of life

• 대한물리의학회지
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• 제14권1호
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• pp.15-23
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• 2019

PURPOSE: This study was conducted to investigate the effects of the myofascial meridians release technique on pain and postural control of college students with forward head posture and to compare the intervention effects of the Grastone massage and the Rollfing massage. METHODS: Thirty subjects with forward head posture were randomly and equally allocated to experimental group I (myofascial meridians release technique using Grastone massage, n=15) or experimental group II (myofascial meridians release using Rollfing massage, n=15). All subjects underwent 30 minutes of different myofascial meridians release techniques in addition to general physical therapy (hot pack: 15 min, interferential current therapy: 15 min, ultra sound: 5 min) three times a week for a total of 6 weeks. Outcome was measured before and after 4 weeks of intervention. RESULTS: In both groups, the numerical rating scale of pain was significantly decreased after intervention, with experimental group I showing a greater decrease than experimental group II. The neck disability index decreased significantly after intervention in both groups, with experimental group I showing a significantly greater decrease than the controls. The distance of the head forward displacement did not differ significantly between the two groups (p>.05). CONCLUSION: This study suggests that the Grastone method combined with the myofascial meridians release technique is a more effective intervention for improvement of pain and postural control in adults with moderate forward head posture.

• 대한치과교정학회지
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• 제25권3호
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• pp.273-286
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• 1995

안면골 성장유형에 따른 두개안면골의 성장양상의 차이를 조사하기 위하여 정상교합자 남자 19명 여자 14명으로 부터 8.5세에서 18.5세까지 10년 동안에 걸쳐 촬영한 연속 두부방사선규격사진을 분석 조사하였다. 이 조사에서 안면골 성장유형은 최초 8.5세에서 10년 후인 18.5세 사이의 Y-axis의 총변화량을 기준으로 Drop, Neutral, Forward군으로 구분하였다. 각 군에서 안면 각 부위의 변화를 계측 분석하여 각 유형의 10년간 성장양상의 차이를 조사한 결과는 다음과 같이 요약할 수 있었다. 본 연구에 사용된 대상에서 두개안면골 성장양상의 분포는 Neutral군이 52%, Forward군이 27%, Drop군이 21%로 나타났다. 두개저에 대한 상,하악골익 전방성장은 Forward군이 Drop군에 비해 크게 나타났으며 Neutral군과 Forward군에서 상악에 비해 하악의 전방성장이 크게 나타났다. FH plane에 대한 palaltal plane의 기울기는 연구기간 동안 Forward군이 다른 두 군에 비해 전상방으로 경사되면서 성장하였다. 또한 하악평면은 Forward군이 Drop군에 비해 반시계 방향의 회전이 크게 나타났으며 이런 경향은 남자가 여자보다 크게 나타났다. 하악체부(Go-Me)의 길이 성장은 Drop군이 Forward, Neutral군에 비해 작게 나타났다 본 연구에서 안면골의 성장에 관하여 길이 및 각도적 계측치는 각기 다양하게 나타났으나 수직적 비율의 특성은 각 군에서 비교적 일관성 있게 유지되는 경향을 나타내었다. 이상의 분석자료를 이용하여 교정진단시 개개인의 성장양상을 평가하기 위하여 8.5세에서 18.5세까지 성장유형별 Profilogram을 작성 제시하였다.