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RISS 인기검색어
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- 저자 : Ji Aimin (검색결과 3 건)
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Aimin Ji,Xu Yin,Minghai Yuan 대한기계학회 2015 JOURNAL OF MECHANICAL SCIENCE AND TECHNOLOGY Vol.29 No.9
There are two problems in Collaborative optimization (CO): (1) the local optima arising from the selection of an inappropriate initialpoint; (2) the low efficiency and accuracy root in inappropriate relaxation factors. To solve these problems, we first develop the Latinhypercube design (LHD) to determine an initial point of optimization, and then use the non-linear programming by quadratic Lagrangian(NLPQL) to search for the global solution. The effectiveness of the initial point selection strategy is verified by three benchmark functionswith some dimensions and different complexities. Then we propose the Adaptive relaxation collaborative optimization (ARCO)algorithm to solve the inconsistency between the system level and the disciplines level, and in this method, the relaxation factors are determinedaccording to the three separated stages of CO respectively. The performance of the ARCO algorithm is compared with the standardcollaborative algorithm and the constant relaxation collaborative algorithm with a typical numerical example, which indicates thatthe ARCO algorithm is more efficient and accurate. Finally, we propose a Hybrid collaborative optimization (HCO) approach, whichintegrates the selection strategy of initial point with the ARCO algorithm. The results show that HCO can achieve the global optimalsolution without the initial value and it also has advantages in convergence, accuracy and robustness. Therefore, the proposed HCO approachcan solve the CO problems with applications in the spindle and the speed reducer.
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Collaborative optimization of NURBS curve cross-section in a telescopic boom
Aimin Ji,Changsheng Chen,Liping Peng,Pin Lv,Xiaodi He 대한기계학회 2017 JOURNAL OF MECHANICAL SCIENCE AND TECHNOLOGY Vol.31 No.8
To improve the carrying capacity and reduce the weight of telescopic boom structure in a truck crane, a Collaborative optimization (CO) approach was applied to solve the problems of strength, stiffness and local stability in the telescopic boom structure. First, the complex optimization problem of the telescopic boom structure was decomposed into two-level optimizations: the system level and two subsystem levels for strength and local stability. Second, the underside curve of the boom’s cross-section was constructed by the Nonuniform rational B-Splines (NURBS) curve. 3D parametric solid model and the parametric finite element analysis model for the strength and the local stability were then established. Third, the mathematical models of the strength and local stability for the subsystem levels, and the system level were optimized, respectively. The adaptive relaxation factor algorithm and the penalty function approach were applied to improve the efficiency of CO. Next, the CO process which integrates the ANSYS package with ISIGHT platform was implemented. The optimal results show that the carrying capacity of the telescopic boom structure can be significantly improved and its weight efficiently is reduced. Finally, with the comparison of the stress values obtained from both the experimental test and the theoretical computation, highly coincident results could be obtained to verify the reliability of CO of a telescopic boom.
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Influence of hexapod robot foot shape on sinking considering multibody dynamics
Gang He,Zhaoyuan Cao,Qian Li,Denglin Zhu,Ji Aimin 대한기계학회 2020 JOURNAL OF MECHANICAL SCIENCE AND TECHNOLOGY Vol.34 No.9
Hexapod robots have attracted attention for their excellent terrain adaptabilities. When a robot walks on soft soil, dynamic subsidence and slippage greatly reduce its walking performance. The influence of foot’s shape is usually ignored or simply studied without considering the multibody dynamics of the robot. This study is focused on the influence of the foot shape on the walking performance of a robot by coupling the sinkage with multibody dynamics. A composite contact model based on the Bekker, spring-damping, and Janosi– Hanamoto models was used to model the interaction of the robot and soft soil. Non-uniform rational B-spline (NURBS) surface and mesh were used to describe the geometries of foot and soft soil, respectively. The influences of three foot shapes on the sinkage and walking stability of the robot were analyzed by comparsion. The improved X-shaped foot reduced the robot’s sinkage and improved its walking stability.
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