• Steel and Composite Structures
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• 제44권3호
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• pp.371-388
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• 2022

The present study tackles the problem of forced vibration of imperfect axially functionally graded shell structure with truncated conical geometry. The linear and nonlinear large-deflection of the structure are considered in the mathematical formulation using von-Kármán models. Modified coupled stress method and principle of minimum virtual work are employed in the modeling to obtain the final governing equations. In addition, formulations of classical elasticity theory are also presented. Different functions, including the linear, convex, and exponential cross-section shapes, are considered in the grading material modeling along the thickness direction. The grading properties of the material are a direct result of the porosity change in the thickness direction. Vibration responses of the structure are calculated using the semi-analytical method of a couple of homotopy perturbation methods (HPM) and the generalized differential quadrature method (GDQM). Contradicting effects of small-scale, porosity, and volume fraction parameters on the nonlinear amplitude, frequency ratio, dynamic deflection, resonance frequency, and natural frequency are observed for shell structure under various boundary conditions.

• 제어로봇시스템학회:학술대회논문집
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• 제어로봇시스템학회 2004년도 ICCAS
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• pp.1162-1167
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• 2004

This paper presents the design methodology of digital fuzzy controller(DFC) for the systems with time-delay. We propose the fuzzy feedback controller whose output is delayed with unit sampling period and predicted. The analysis and the design problem considering time-delay become easy because the proposed controller is syncronized with the sampling time. The stabilization problem of the digital fuzzy system with time-delay is solved by linear matrix inequality(LMI) theory. Convex optimization techniques are utilized to solve the stable feedback gains and a common Lyapunov function for designed fuzzy control system. To show the effectiveness the proposed control scheme, the network control example is presented.

• 대한기계학회논문집
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• 제15권1호
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• pp.98-106
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• 1991

본 연구에서는 로봇이용의 자동화를 위하여 가장 필수적인 과정인 로봇의 운 동경로 계획에 관하여 연구하고 작업영역 내에 장애물이 있는 경우에 로봇과 장애물과 의 충돌 회피를 위한 정량적인 양으로 두물체간의 최소거리 및 충돌깊이를 효율적으로 계산할 수 있는 방법을 제안하며 이를 이용하여 로봇이 장애물과 충돌하지 않고 주어 진 작업을 수행할 수 있는 로봇의 경로를 자동으로 생성함으로써 로봇을 보다 상위레 벨에서 운용하기 위한 기초를 마련한다.

• 한국지능시스템학회:학술대회논문집
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• 한국퍼지및지능시스템학회 2003년도 ISIS 2003
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• pp.236-239
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• 2003

In this paper, we investigate the issues for the design and implementation of tele-operation system based on the haptic interface. Here, the 3-DOF haptic device and the x-y-z stage are employed as master controller and slave system respectively. In this master-slave system, the force feedback algorithm, the modeling of virtual environments and the control method of x-y-z stage are proposed. In this paper, inernet network is used for data communication between master and slave. We construct virtual environment of the real convex surface from the force-feedback in controlling the X-Y-Z stage and getting the force applied by the 3-DOF haptic device.

• 대한산업공학회지
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• 제4권2호
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• pp.91-96
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• 1978

A modeling framework and its computational methodology for an industrial sector of the economy are investigated. The suggested industrial sector model is characterized by a programming (process analysis) representation of a production sector and an econometric estimation of the price sensitive (own and cross-prices) demands. By introducing the price sensitive demands into the process analysis representation of the production sector, it becomes possible to analyze and plan the pricing policy, the optimal production schedules and capacity expansion plans within a single framework. The computational scheme suggested in the report is based on the iterative approach each of which solves a separable convex programming problem.

• 한국정밀공학회지
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• 제13권9호
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• pp.156-164
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• 1996

Tool interference is one of the most critical problems in machining die cavities and punches. When machining concave or convex regions of cavities with large radius tool in rough cutting, the tool easily overcuts or undercuts the portions of the surface, which result in machining inaccuracy. So the generation of interference-free tool path must be required for more efficient rough cutting. In this paper, we present a method for modeling die cavities which consist of simple surface or analytic compoyund surfaces and present an algorithm for checking and removing the tool interference occurred in machining the die cavities. Using these algorithms, we can represent a die cavity, and check the interfer- ence regions, and then remove these interferences. Especially we focus on the side interference in the sides of analytic elements and base surface boundary.

• Interaction and multiscale mechanics
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• 제3권3호
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• pp.267-276
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• 2010

A nonlocal finite element model is developed for solving elasto-static frictional contact problems of nanostructures and nanoscale devices. A two dimensional Eringen-type nonlocal elasticity model is adopted. The material is characterized by a stress-strain constitutive relation of a convolution integral form whose kernel is capable to take into account both the diffusion process of nonlocal elasticity and the scale ratio effects. The incremental convex programming procedure is exploited as a solver. Two examples of different nature are presented, the first one presents the behavior of a nanoscale contacting system and the second example discusses the nano-indentation problem.

• 한국소음진동공학회논문집
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• 제14권6호
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• pp.486-494
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• 2004

This paper addresses the dynamic modeling and closed-loop eigenvibration analysis of composite rotating pretwisted fan blade modeled as non-uniform thin-walled beam with bi-convex cross-section fixed at the certain presetting angle and incorporating piezoelectric induced damping capabilities. The blade model incorporates non-classical features such as transverse shear, rotary inertia and includes the centrifugal and Coriolis force field. A velocity feedback control law relating the piezoelectiriccally induced transversal bending moment at the beam tip with the appropriately selected kinematical response quantity is used and the beneficial effects upon the closed loop eigenvibration of the blade are highlighted.

• International Journal of Fuzzy Logic and Intelligent Systems
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• 제3권2호
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• pp.161-165
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• 2003

In this paper, we investigate the issues on the design and implementation of tele-operation system based on the haptic interface. Here, the 3-DOF haptic device and the X-Y-Z stage are employed as master controller and slave system respectively. For this master-slave system, the force feedback algorithm, the modeling of virtual environments and the control method of X-Y-Z stage are presented. In this paper, internet network is used for data communication between master and slave. We construct virtual environment of the real convex surface from the force-feedback in controlling the X-Y-Z stage and measuring the force applied by the 3-DOF haptic device.

• 대한전기학회:학술대회논문집
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• 대한전기학회 1987년도 정기총회 및 창립40주년기념 학술대회 학회본부
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• pp.425-429
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• 1987

This paper describes a collision avoidance method for planning safe trajectories for multi-robot system in common work space. Usually objects have been approximated to convex polyhedra in most previous researches, but in case using such the approximation method it is difficult to represent objects analytically in terms of functions and also to describe tile relationship between the objects. In this paper, in order to solve such problems a modeling method which approximates objects to cylinder ended by hemispheres and or sphere is used and the maximum distance functions is defined which call be calculated simply. Using an objective function with inequality constraints which are related to minimum distance functions, work range and maximum allowable angular velocities of the robots, tile collision avoidance for two robots is formulated to a constrained function optimization problem. With a view to solve tile problem a penalty function having simple form is defined and used. A simple numerical example involving two PUMA-type robots is described.