• International Journal of Control, Automation, and Systems
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• 제6권3호
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• pp.364-377
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• 2008

Due to the difficulty in solving the Hamilton-Jacobi-Isaacs equation, the nonlinear optimal control approach is not very practical in general. To overcome this problem, Ezal et al. (2000) first solved a linear optimal control problem for the linearized model of a nonlinear system given in the strict-feedback form. Then, using the backstepping procedure, a nonlinear feedback controller was designed where the linear part is same as the linear feedback obtained from the linear optimal control design. However, their construction is based on the cancellation of the high order nonlinearity, which limits the application to the smooth ($C^{\infty}$) vector fields. In this paper, we develop an alternative method for backstepping procedure, so that the vector field can be just $C^1$, which allows this approach to be applicable to much larger class of nonlinear systems.

• 복식문화연구
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• 제25권5호
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• pp.708-717
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• 2017

Industrial innovation in Britain, during the eighteenth and nineteenth centuries, stimulated the introduction of the factory system and the migration of people from rural agricultural communities to urban industrial societies. The factory system brought elevated levels of economic growth to the purveyors of capitalism, but forced people to migrate into cities where working conditions in factories were, in general, harsh and brutal, and living conditions were cramped, overcrowded and unsanitary. Industrial developments, known collectively as the 'Industrial Revolution', were driven initially by the harnessing of water and steam power, and the widespread construction of rail, shipping and road networks. Parallel with these changes, came the development of purchasing 'middle class', consumers. Various technological ripples (or waves of innovative activity) continued (worldwide) up to the early-twenty-first century. Of recent note are innovations in digital technology, with associated developments, for example, in artificial intelligence, robotics, 3-D printing, materials technology, computing, energy storage, nano-technology, data storage, biotechnology, 'smart textiles' and the introduction of what has become known as 'e-commerce'. This paper identifies the more important early technological innovations, their influence on textile manufacture, distribution and consumption, and the changed role of the designer and craftsperson over the course of these technological ripples. The implications of non-ethical production, globalisation and so-called 'fast fashion' and non-sustainability of manufacture are examined, and the potential benefits and opportunities offered by new and developing forms of social media are considered. The message is that hand-crafted products are ethical, sustainable and durable.

• Smart Structures and Systems
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• 제1권4호
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• pp.325-338
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• 2005

Utilizing robotic based reconfigurable nodal structural health monitoring systems has many advantages over static or human positioned sensor systems. However, creating a robot capable of traversing a variety of civil infrastructures is a difficult task, as these structures each have unique features and characteristics posing a variety of challenges to the robot design. This paper outlines the design and implementation of a novel robotic platform for deployment on ferromagnetic structures as an enabling structural health monitoring technology. The key feature of this design is the utilization of an attachment device which is an advancement of the common magnetic base found in the machine tool industry. By mechanizing this switchable magnetic circuit and redesigning it for light weight and compactness, it becomes an extremely efficient and robust means of attachment for use in various robotic and structural health monitoring applications. The ability to engage and disengage the magnet as needed, the very low power required to do so, the variety of applicable geometric configurations, and the ability to hold indefinitely once engaged make this device ideally suited for numerous robotic and distributed sensor network applications. Presented here are examples of the mechanized variable force magnets, as well as a prototype robot which has been successfully deployed on a large construction site. Also presented are other applications and future directions of this technology.

• 한국태양에너지학회 논문집
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• 제38권5호
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• pp.27-36
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• 2018

The purpose of this paper is to apply the numerical solution procedure to compute conduction time series factors (CTSF) for construction materials with large thermal capacities. After modifying the procedure in Ref. [9], it is applied to find the CTSF for the wall type 19 and the roof type 18 of ASHRAE. The response periods for one hr pulse load are longer than 24hrs for these wall and roof. The CTSF generated using modified procedure agree well with the values presented in the ASHRAE handbook. The modified procedure is a general procedure that can be applied to find CTSF for materials with complex structures. For the large thermal capacity materials, it should be checked whether thermal response period of the material is over 24hr or not. With suggested solution procedure, it is easy to check the validity of the CTSF based on 24hr period.

• Smart Structures and Systems
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• 제24권2호
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• pp.223-231
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• 2019

The properties of Electroactive Polymer (EAP) materials are attracting the attention of engineers and scientists from many different disciplines. From the point-of-view of robotics, Ionic Polymer Metal Composites (IPMC) belong to the most developed group of the EAP class. To allow effective design of IPMC-actuated mechanisms with large induced strains, it is necessary to have adequate analytical tools for predicting the behavior of IPMC actuators as well as simulating their response as part of prototyping methodologies. This paper presents a novel IPMC motor construction. To simulate the bending behavior that is the dominant phenomenon of motor movement process, a nonlinear model is used. To accomplish the motor design, the IPMC model was identified via a series of experiments. In the proposed model, the curvature output and current transient fields accurately track the measured responses, which is verified by measurements. In this research, a three-dimensional Finite Element Method (FEM) model of the IPMC motor, composed of IPMC actuators, simultaneously determines the mechanical and electrical characteristics of the device and achieves reliable analysis results. The principle of the proposed drive and the output signals are illustrated in this paper. The proposed modelling approach can be used to design a variety of controllers and motors for effective micro-robotic applications, where soft and complex motion are required.

• 한국BIM학회 논문집
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• 제10권1호
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• pp.1-8
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• 2020

In managing building facilities, spatial information is the basic data for decision making. However, the method of acquiring spatial information is not easy. In many cases, the site and drawings are often different due to changes in facilities and time after construction. In this case, the site data should be scanned to obtain spatial information. The scan data actually contains spatial information, which is a great help in making space related decisions. However, to obtain scan data, an expensive LiDAR (Light Detection and Ranging) device must be purchased, and special software for processing data obtained from the device must be available.Recently, SLAM (Simultaneous localization and mapping), an advanced map generation technology, has been spreading in the field of robotics. Using SLAM, 3D spatial information can be obtained quickly in real time without a separate matching process. This study develops and tests whether SLAM technology can be used to obtain spatial information for facility management. This draws considerations for developing a SLAM device for real-time remote scanning for facility management. However, this study focuses on the system development method that acquires spatial information necessary for facility management through SLAM technology. To this end, we develop a prototype, analyze the pros and cons, and then suggest considerations for developing a SLAM system.

• 대한토목학회논문집
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• 제26권6D호
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• pp.969-974
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• 2006

국내 건설현장 기능 인력 부족 문제가 심각하다. 현재 국내 건설현장은 신규 인력 진입 저조에 따른 공급 부족과 기능 인력의 고령화에 따른 생산성 저하 등 양적, 질적인 문제를 동시에 겪고 있다. 여기에 현재 계획되고 있는 대규모 국가사업으로 향후 건설현장 기능 인력의 부족은 더욱 심각해질 전망이다. 건설현장 기능인력 수급 불균형 문제에 대한 해결방안으로서의 공급 확보 정책은 시대의 흐름과 기술 발전에 따른 미래 전망을 고려해볼 때, 어느 정도 한계가 있다고 판단되며, 기술적 접근을 통해 기능 인력에 대한 수요를 줄이는 노력이 병행되어야 한다고 판단된다. 기술 발전을 통한 기능인력 수요 감소를 위해서는 현장에서 수행되는 작업 프로세스의 생산성과 효율성을 향상시킬 수 있는 분야에 연구의 초점이 맞춰져야 하며, 기능인력 수요 저감의 핵심이 되며 연구개발 노력이 필요한 분야로서 1) 건설 자동화 및 기계화 확대를 통한 기능 인력의 대체, 2) 고성능 건설 자재 개발 및 활용으로 현장 작업량 저감, 3) 정보화 기술 도입으로 현장 작업대기 시간 감축에 의한 생산성 향상, 4) 모듈화, 선조립, 공장제작 등 선작업 방식의 적용을 통한 현장 기능 인력 수요 저감 및 생산성 향상, 5) 재설계/재시공 예방으로 추가 작업 발생 방지, 6) 기능 및 직종 통합에 의한 다기능 인력 양성, 7) 시공 프로세스 개선에 의한 작업 생산성 향상 등의 7가지 주제를 제시하였다.

• 한국전산구조공학회논문집
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• 제33권2호
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• pp.95-101
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• 2020

풍력터빈 블레이드는 바람의 운동에너지를 축일로 변환하는 장치로서 상대적으로 고속 회전하면서 양력과 항력의 다양한 하중 조합과 진동에 견딜 수 있도록 내구 강도가 큰 경량의 재료를 선택하여 강성을 증가시키는 구조를 갖도록 설계되어야 한다. 본 연구는 CFRP 프리프레그를 사용하여 소형 풍력 블레이드를 제작하는 경우 공정 시간을 단축하는 기술을 개발하려는 목적으로 수행되었다. QBlade 수치해석 프로그램을 사용하여 블레이드의 형상을 결정하였다. 주어진 풍속에서 바람에 의해 부가되는 양력과 항력을 계산하는 유체역학 수치해석을 수행하고, 대표적인 블레이드 구조에 대해 블레이드 외피 재료에 가해지는 폰미세스 응력을 예측하는 재료역학 수치해석을 수행하였다. 인장 강도 시험의 불확실도를 개선하기 위해 ASTM D638 규정을 수정하여 새로운 시편의 형상을 제안하였고, 기존 형상의 인장 강도와 유사한 평균값을 얻되 파단 위치의 재현성이 향상됨을 확인하였다. 일련의 실험을 통해 소형 풍력블레이드의 제작에 블래더 가압 방식을 적용하면 충분한 내구 강도를 확보하면서 공정시간을 단축할 수 있음을 확인하였다.

• 제어로봇시스템학회:학술대회논문집
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• 제어로봇시스템학회 2003년도 ICCAS
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• pp.1927-1932
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• 2003

In a previous study, the authors have proposed the Cooperative Collision Avoidance (CCA) method which enables mobile robots to cooperatively avoid collisions, by extending the concept of the Velocity Obstacle to multiple robot systems. The method introduced an evaluation function considering an operation objective so that each robot can choose the velocity which optimizes the function. As the evaluation function could be of an arbitrary type, this method is applicable to a wide variety of tasks. However, it complicates the optimization of the function especially in real-time. In addition, construction of the evaluation function requires an operation objective of the other robot which is very hard to obtain without communication. In this paper, the CCA method is improved considering such problems for implementation. To decrease computational costs, the previous method is simplified by introducing two essential assumptions. Then, by treating the desired direction of locomotion for each robot as the operation objective, an operation objective estimator which estimates the desired direction of the other robot is introduced. The only measurement required is the other robot's relative position, since the other information can be obtained through the estimation. Hence, communicational devices that are necessary for most other cooperative methods are not required. Moreover, mobile robots employing the method can avoid collisions with uncooperative robots or moving obstacles as well as with cooperative robots. Consequently, this improved method can be applied to general dynamic environments consisting of various mobile robots.

• 드라이브 ㆍ 컨트롤
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• 제17권1호
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• pp.27-36
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• 2020

The aim of this study is to design a simulation model for an electric All-Wheel-Drive (AWD) tractor to evaluate the performance of the selected component and agricultural work ability. The electric AWD tractor consists of four motors independently for each drive wheel, and each motor is combined with an engine generator, a battery pack, and reducers. The torque data of a 78 kW-class tractor was measured during plow tillage and driving operation to develop a workload cycle. A simulation model was developed by using commercial software, Simulation X, and it used the workload as the simulation condition. As a result of simulation analysis, the drive system, including an electric motor and reducers, was able to cope with high load during plow tillage. The SOC (State of Charge) level was influenced by the output power of the motor, and it was maintained in the range of 50~80%. The fuel consumed by the engine was about 18.23 L during working on a total of 8 fields. The electric AWD tractor was able to perform agricultural work for about 7 hours. In the future study, the electric AWD tractor will be developed reflecting the simulation condition. Research on the comparison between the simulation model and the electric AWD tractor should be performed.