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신응수,김기성 한국생산제조학회 2019 한국생산제조학회지 Vol.28 No.6
This study investigates the motion fluctuations of a cable-drive system with polygonal blocks. First, a simplified five-bar system is introduced for modeling the switching blocks, as well as the straight and curved sections. Then, kinematic analysis is performed by solving the loop equation of the five-bar system. Finally, a parameter study is conducted to determine the effect of the block length on the position and velocity fluctuations at a transition from the curved to straight. The results demonstrate that the system undergoes a two-phase periodic motion, and the block length significantly affects the motion fluctuation both in the axial and lateral directions. Additionally, it is also found that a block length corresponding to a good performance in the axial direction exhibits a poor performance in the lateral direction.
신응수,김기성 한국생산제조학회 2018 한국생산제조학회지 Vol.27 No.6
This study investigates the dynamics characteristics of a cable carrier with respect to the variations in carrier length and axially moving speed. The characteristic equation of the carrier’s lateral vibration is derived from the configuration of blocks connected through pin joints. Then, the modal characteristics and stability behavior of the carrier are obtained by solving the characteristic equation numerically. Results show that natural frequencies decrease as the carrier speed increases, particularly around the stability boundaries. The instability of divergence and flutter occurs as the carrier speed increases. In addition, the critical speed at the stability boundary is observed to be inversely proportional to the carrier length, which requires a tradeoff between the carrier’s workspace and the productivity of the carrier.
신응수,박정호 한국소음진동공학회 2000 소음 진동 Vol.10 No.2
This paper intends to provide an analytic vibrational model of non-circular cutting by a lathe and to investigate its stability criteria. A single degree-of-freedon model based on the orthogonal cutting theory has the characteristics of parametric excitation due to the nonlinear cutting force that changes periodically its direction as well as its magnitude. The Floquet theory has been applied to investigate the stability of the linearized system and the stability diagrams have been obtained with respect to the ovality, the cut velocity and the cut depth. Also nonlinear analysis has been performed to verify the linear analysis and compare the results with those from circular cutting. Results show that a critical cut depth is decreased as the ovality is increased while a critical cut velocity is increased as the ovality is increased. Also, a good agreement in critical conditions has been observed between the linear and nonlinear analyses for the ovality less than 2%. Accordingly, the linear analysis can be said to be applicable for most practical oval cuttings whose ovality are much less than 2%.
양방향 수동 휠체어와 기존 휠체어의 추진 동작 비교 분석
신응수,이희태 한국운동역학회 2001 한국운동역학회지 Vol.11 No.1
This work provides the biomechanical evaluations of a maunal wheelchair with a bi-directional driving system. The new propulsion strategy can be accomplished by employing a special gear system that converts the oscillatory motion of a handrim into the unidirectional output motion of a wheel. A main feature of the forward · backward propulsion is to supply continuous driving torque without break. Motion analysis has been performed through the two-dimensional image processing for measuring the kinematic properties of the upper arm and fore arm. Then, the inverse dynamics analysis has been done for obtaining the joint torques, the handrim forces and the output power. Results show that the output power by the bi-directional propulsion is almost twice as much as that by conventional propulsion. Also, the new propulsion is expected to reduce the fatigues and injuries at arm joints by employing mort muscle groups for movement. In conclusion, the bi-directional propulsion can greatly improve the performances of manual wheelchairs by providing better mobility as well as by guaranteeing several advantages from a biomechanical viewpoint. Future development of a manual wheelchair optimized for the bi-directional propulsion will further improve the propulsion performances.
신응수,이기녕,신태명,김옥현 한국소음진동공학회 2002 한국소음진동공학회 논문집 Vol.12 No.1
This paper intends to investigate the effects of speed fluctuation caused by the cogging torque in permanent magnetic motors on the stability of the transverse vibration for a spinning disk. Based on the Kirchhoff\`s plate theory and the assumed mode methods, a set of discretized equations of motion were derived for an annular disk rotating with a harmonically varying speed. Then, a perturbation method using the multiple time scales was employed and stability boundaries were determined explicitly in terms of the magnitude and frequency of speed fluctuation, a nominal sped and the modal characteristics of the disk. It is found that parametric resonance occurs at several speed ranges and a single mode or a combination of two modes are involved to cause instability. It is also observed that unstable regions become broadened as the spinning speed increases or two modes are combined in parametric instability. As numerical simulations, stability analysis of a conventional CD-ROM drive was performed. Results of this work can e used as guidelines for motor design and operations with low vibration.