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양방향 변형이 가능한 1 자유도 변형 바퀴 메커니즘의 자율 설계
김중호(Jungho Kim),심정원(Jeong Won Shim),김영수(Youngsoo Kim),김윤영(Yoon Young Kim) 대한기계학회 2022 대한기계학회 춘추학술대회 Vol.2022 No.11
The 1-DOF (degree of freedom) mechanism has a simple structure and is easy to control, so it is desirable for a mobile robot using a tri-footed wheel to overcome various obstacles. So far, the designs of 1-DOF transformable wheel mechanisms have been mainly limited to simple shape changes between wheel and legs or unidirectional transformation, so they are not stable in overcoming the combined obstacles of climbing and descent. Here, we develop an autonomous synthesis method of a 1-DOF mechanism that can adaptively implement both ascending and descending motions. First, we construct the target motion of the mechanism to satisfy the required climbing performance. Second, the synthesis formulation is constructed to satisfy the target pose of the mechanism. We succeeded in synthesizing a 1-DOF RPRP mechanism capable of bidirectional transformation by adjusting the current design methodology to prevent problems in structural analysis at the transition point with a singular configuration.
양방향 변형이 가능한 1 자유도 변형 바퀴 메커니즘의 자율 설계
김중호(Jungho Kim),심정원(Jeong Won Shim),김영수(Youngsoo Kim),김윤영(Yoon Young Kim) 대한기계학회 2022 대한기계학회 춘추학술대회 Vol.2022 No.11
The 1-DOF (degree of freedom) mechanism has a simple structure and is easy to control, so it is desirable for a mobile robot using a tri-footed wheel to overcome various obstacles. So far, the designs of 1-DOF transformable wheel mechanisms have been mainly limited to simple shape changes between wheel and legs or unidirectional transformation, so they are not stable in overcoming the combined obstacles of climbing and descent. Here, we develop an autonomous synthesis method of a 1-DOF mechanism that can adaptively implement both ascending and descending motions. First, we construct the target motion of the mechanism to satisfy the required climbing performance. Second, the synthesis formulation is constructed to satisfy the target pose of the mechanism. We succeeded in synthesizing a 1-DOF RPRP mechanism capable of bidirectional transformation by adjusting the current design methodology to prevent problems in structural analysis at the transition point with a singular configuration.
조홍기 (Honggi Cho),윤백 (Baek Youn),김중호 (Jungho Kim) 대한설비공학회 2012 대한설비공학회 학술발표대회논문집 Vol.2012 No.6
The Characteristics of heat transfer and pressure drop in a concentric heat exchanger with inner tube was investigated by using a commercial CFD program. Four different inner tubes were studied. Bare tube has no fin and SPL 1, 2 and 3 have fin spirally attached on their surface. In case of SPL 1 & 3, the fin pitch is same with 1.18mm and the fin shape is triangular. However, the fin height is 1.00mm and 1.20mm for SPL 1 & 3, respectively. The fin height of SPL 2 is 1.05mm and the fin shape looks like an airfoil. The fin pitch of SPL 2 is 1.05mm. For all inner tubes with fin, the heat transfer rate increased from 1.8 to 2.3 times and the pressure drop increased from 5.5 to 8.6 times bare tube. SPL 3 with the highest fin height of 1.20mm showed the largest heat transfer rate, also the pressure drop increased significantly. It is seen that SPL 2 shows the best heat transfer and pressure drop characteristics, since SPL 2 showed similar heat transfer rate with SPL 3 but lower pressure drop by 17% than SPL 3. Since heat transfer and pressure drop strongly depend on the fin geometry of inner tube and have a trade-off relationship, the fin geometry should be selected for its application and condition.
조홍기(Honggi Cho),김태헌(Tae-Hun Kim),홍순철(Soon-Cheol Hong),김경록(Kyoungrock Kim),김중호(Jungho Kim),이창선(Changseon Lee) 대한설비공학회 2013 대한설비공학회 학술발표대회논문집 Vol.2013 No.6
The objective of present work is to investigate the performance of enhanced tubes with inner grooves by using a commercial CFD program. Four different enhanced tubes have been studied. G_0 and G_max tubes have no inner grooves on their inner surfaces, therefore, their inner surfaces are smooth. The inner diameter of G_0 and G_max are 8.9 mm and 9.9 mm, respectively. G_6 has 6 inner grooves and G_12 has 12 inner grooves. For all enhanced tubes, Serrated fins are manufactured on their outside surfaces and the inner groove is 1.0mm in width and 0.5mm in depth. As the number of inner grooves increase from 0 to 6 and 12, the pressure drops for G_6 and G_12 increased by 18% and 20% and the heat transfer rates increased by 7% and 14% under the mass flow rate of 189 kg/hr. In case of G_max, pressure drop and heat transfer rate decreased by 29% and 6% than those of G_0, because G_max have no inner grooves and its diameter is larger than that of G_0 by 1.0 mm.