• Journal of Mechanical Science and Technology
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• v.18 no.5
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• pp.780-788
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• 2004

To avoid the unit inconsistency problem in the conventional Jacobian matrix, new formulation of a dimensionally homogeneous inverse Jacobian matrix for parallel manipulators with a planar mobile platform by using three end-effector points was presented (Kim and Ryu, 2003). This paper presents force relationships between joint forces and Cartesian forces at the three End-Effector points. The derived force relationships can then be used for analyses of the input/output force transmission. These analyses, forward and inverse force transmission analyses, depend on the singular values of the derived unit consistent Jacobian matrix. Using the proposed force relationship, a numerical example is presented for actuator size design of a 3-RRR planar parallel manipulator.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.27 no.11
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• pp.1941-1948
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• 2003

This paper is about feasibility study of positioning device using magnetic suspension system which uses only vertical magnetic forces. The proposed system has inherited advantages from contact-free system, simple structure, and high expansibility in operating range different from conventional positioning devices. In this paper, the structure and operating principle are described and the linearized magnetic force and dynamic model are obtained. With the linear control theory, the experiments are executed. finally, the experimental results are shown.

• Proceedings of the KSME Conference
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• 2001.06a
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• pp.837-841
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• 2001

The column-type sensing element in building and mechanical construction parts was designed as three forces and three moments sensor by attaching strain gages approximately. Compared to conventional multi-component sensor, the designed sensor can solve the problem about low stiffness and high cost. The radius of the column was designed analytically and compared with finite element analysis. The coupling errors between components were minimized by using addition and subtraction procedure of signals. The fabricated sensor was tested by using a deadweight force standard machine and a six-component force calibration machine in Korea Research Institute of Standards and Science(KRISS). The calibration showed that the multi-component force/moment sensor had coupling error less than 19.8 % between $F_x$ and $M_y$ components, and 9.0 % in case of other components.

• Proceedings of the KSME Conference
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• 2003.11a
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• pp.1500-1505
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• 2003

In order to avoid the unit inconsistency problem in the conventional Jacobian matrix, previously we presented new formulation of a dimensionally homogeneous inverse Jacobian matrix for parallel manipulators with a planar mobile platform by using three end-effector points based on the velocity relationship [1]. This paper presents force relationships between joint forces and Cartesian forces at the three End-Effector points. The derived force relationships can then be used for analyses of the input/output force transmission. These analyses, forward and inverse force transmission analyses, depend on the singular values of the derived dimensionally homogeneous Jacobian matrix. Using the proposed force relationship, a numerical example is presented for actuator size design of a 3-RRR planar parallel manipulator.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 2002.05a
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• pp.489-494
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• 2002

This paper presents hydraulic model which can capture the hysteric damping force behavior of ER damper. A flow mode rue ER damper is manufactured, and its field-dependent damping forces are measured. Newly proposed hydraulic model which derived from physical hydro-mechanical parameters of ER damper are conventional Bingham model are investigated to represent the field-dependent damping force characteristics of ER damper. After principal parameters of two models are estimated from the measured damping forces data, the force vs velocity hysteresis cycles are then reconstructed. The results show that the proposed hydraulic model can capture the hysteresis behavior of ER damper accurately.

• Transactions of the Korean Society for Noise and Vibration Engineering
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• v.12 no.2
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• pp.108-115
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• 2002

The excitation forces from the periodical firing pressure in cylinder and the rotating crank mechanism cause lots of vibration problems in diesel engines. In this Paper. the computational program for predicting the excitation force is developed and applied to 4-stroke In-line engines. The crank angle is also optimized to reduce the first and second order moment produced by engines. Compared to the conventional uniform crank angle, about 70 % of the first order horizontal and vertical moment can be reduced by re-designing the crank angle non-uniformly.

• Computers and Concrete
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• v.11 no.6
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• pp.515-529
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• 2013

The moment-curvature relation for simple bending is a well-studied subject and the classical moment-curvature diagram is commonly found in literature. The influence of axial forces has generally been considered as compression onto symmetrically reinforced cross-sections, thus strain at the reference fiber never has been an issue. However, when dealing with integral structures, which are usually statically indeterminate in different degrees, these concepts are not sufficient. Their horizontal elements are often completely restrained, which, under imposed deformations, leads to moderate compressive or tensile axial forces. The authors propose to analyze conventional beam cross-sections with moment-curvature diagrams considering asymmetrically reinforced cross-sections under combined influence of bending and moderate axial force. In addition a new diagram is introduced that expands the common moment-curvature relation onto the strain variation at the reference fiber. A parametric study presented in this article reveals the significant influence of selected cross-section parameters.

• The Transactions of The Korean Institute of Electrical Engineers
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• v.57 no.4
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• pp.589-595
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• 2008

Detent force of a permanent magnet linear motor(PMLSM) consist of cogging and drag forces, and should be minimized for high precision control purpose applications. This paper shows that the cogging force can be reduced effectively by employing 9 pole 10 slot structure. The drag force is minimized by optimizing the total length and shape of the exterior teeth of armature core simultaneously by using($1+{\lambda}$) evolution strategy coupled with response surface method. After optimization, the optimized PMLSM is proven to reduce 95% and 92.6% of the cogging and total detent forces, respectively, and give 12% and 6.4% higher Back-emf and thrust force, respectively, compared with a conventional 12 pole 9 slot structure under the same condition. Additionally, Simulation results by the proposed optimum design are verified by the experiment results.

• Proceedings of the Earthquake Engineering Society of Korea Conference
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• 2003.03a
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• pp.465-472
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• 2003

The main concept of base isolation system is to reduce the member forces by decreasing the earthquake forces transmitted to superstructure instead of the conventional techniques of strengthening the structural members. There are two important advantages in friction pendulum systems. The functions of carrying the vertical load and of providing horizontal stiffness are effectively separated. This results in a more stable system that eliminates the need of a fail-safe mechanism. Friction pendulum systems are less sensitive to variations in the frequency content of ground excitation and tend to limit the intensity of the farce imparted to the superstructure. This study investigates the friction coefficients on the FPS test specimens according to the velocity, bearing pressure and test waveform.

• Journal of the Earthquake Engineering Society of Korea
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• v.11 no.3 s.55
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• pp.1-10
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• 2007

In general, the tension forces of hanger cable in suspension bridges play an important role in evaluating the bridge conditions. The vibration method, as a conventional one, has been widely applied to estimate the tension forces by using the measured frequencies on hanger cables. However, the vibration method is not applicable to short hanger cables because the fiequencies of short cables are severely sensitive to flexural rigidity. Thus, in this study, the tension forces of short hanger cables, of which the length is shorter than 10 meters, were estimated through back analysis of the cable fiequencies measured from Gwang-An suspension bridge in Korea. Direct approach to back analysis is adopted using the univariate method among the direct search methods as an optimization technique. The univariate method is able to search the optimal tension forces without regard to the initial ones and has a rapid convergence rate. To verify the feasibility of back analysis, the results from back analysis and vibration method are compared with the design tension forces. From the comparison, it can be inferred that back analysis results are more reasonable agreement with the design tension forces of short hanger cable. Therefore, it is concluded that back analysis applied in this study is an appropriate tool for estimating tension forces of short hanger cables.