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Digital manufacturing—the development direction of the manufacturing technology in the 21st century
XIONG You-lun, YIN Zhou-ping
Front. Mech. Eng.. 2006, 1 (2): 125-130.
https://doi.org/10.1007/s11465-006-0021-3
After introducing the concepts of digital manufacturing technology, the discipline framework of digital manufacturing is presented in the paper by discussing its basic concept, theory foundation, key technology and scientific problems in detail. As the core of the advanced manufacturing technology, digital manufacturing is gradually becoming the main manufacturing technology of the twenty-first century. Firstly, the main features of digital manufacturing are indicated and its key supporting technologies are investigated by grouping them into four levels related to product development, numerical control, production management, and enterprise collaboration, respectively. Moreover, the existing problems in the research on the multi-discipline theory foundation of digital manufacturing such as manufacturing informatics, computational manufacturing, and manufacturing intelligence, are also indicated. Then, the core scientific problems of digital manufacturing are discussed in depth, which focuses on digitization of manufacturing information, modeling of manufacturing constraints, high-speed and high-precision numerical control theory, and Internet-based collaboration and integration. Lastly, the development trends and application perspectives of digital manufacturing are concluded.
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Crack fault quantitative diagnosis based on finite element of B-spline wavelet on the interval
XIANG Jia-wei, CHEN Xue-feng, HE Zheng-jia, HE Yu-min
Front. Mech. Eng.. 2006, 1 (2): 177-182.
https://doi.org/10.1007/s11465-006-0001-7
The model-based forward and inverse problems in the diagnosis of structural crack faults were studied. The forward problem is to solve the natural frequencies through a cracked structural model and the inverse problem is to quantitatively determine the crack parameters using the experimental testing frequencies. Then, the one-dimensional crack element of B-spline wavelet on the interval (BSWI) was built to solve the forward problem. Contour plots of normalized crack location versus normalized crack size were plotted by using the first three natural frequencies as the inputs. The intersection of the three curves predicted the normalized crack location and size. The experimental study verified the validity of the wavelet-based crack element in solving crack singular problems to overcome the disadvantages of the traditional finite element method (FEM), such as low efficiency, insufficient accuracy, slow convergence to correct solutions, etc. At the same time, it had adequate identification precision. The new method can be applied to prognosis and quantitative diagnosis of incipient crack.
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Research on transmission principle and kinematics analysis for involute spherical gear
PAN Cun-yun, WEN Xi-sen, YANG Kun-yu, XU Xiao-jun, LIU Min, YAO Qi-shui
Front. Mech. Eng.. 2006, 1 (2): 183-193.
https://doi.org/10.1007/s11465-006-0010-6
A new kind of transmission-type spherical gear called ring involute spherical gear mechanism is introduced. Compared to the famous TRALLFA spherical gear, this new spherical gear has an involute tooth profile, and a ring tooth that is distributed continuously on the surface of the sphere. This allows the gear to overcome two disadvantages of the TRALLFA spherical gear: the drive principle error and the manufacturing difficulty. The new transmission and the formation principle of the tooth s surface of the new spherical gear mechanism are first introduced, then another mechanism, called disk rack, is introduced, which is derived from the spherical gear mechanism when one of the spherical gear s tooth number reaches infinity. To make the research more convenient, every part of the new spherical gear mechanism is named. In the following sections, some problems are discussed, such as the assembly form, the construction characteristics, the correct meshing condition, the continuum transmission condition and so on. Furthermore, the paper deduces the surface formula of the conjugate teeth profiles, which proves that the conjugate teeth profiles is also one of the ringed involute spherical gear. In order to analyze the relationship between two coordinate systems, which is attached respectively to the diving spherical gear and the driven spherical gear, the orientation cosine matrix method is utilized. By series rotational transformation, the kinematics model and inverse kinematics model are deduced. Using the method for calculating the transmission ratio of planet gear train, the relationship of the two oscillating angle between output axis and the bracket is established. Based on the research, the kinematics graphic simulation of spherical gear mechanism and disk rack are made respectively. The results prove correctness of the kinematics model.
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Precision analysis of a weakly-coupled parallel mechanism with three translational degrees of freedom
MA Lv-zhong, GUO Zong-he, YANG Qi-zhi, YIN Xiao-qin, HAN Ya-li, SHEN Hui-ping
Front. Mech. Eng.. 2006, 1 (2): 227-232.
https://doi.org/10.1007/s11465-006-0005-3
This paper analyzes the precision of the dissymmetrical parallel mechanism of 3-RRRP(4R) with three translational degrees of freedom (DOF). The parallel mechanism has weakly-coupled, decoupled and real-time characteristics, thus error compensation can be done using control software. Based on topology structure analysis, the inverse and forward solutions are analyzed and the precision is studied using complete differential method. The influencing factors of the manipulator s precision are studied carefully and the means to enhance the precision are also discussed. It is found that the position errors of the moving platform have nonlinear relation with the position of the mechanism. The δθ'3 error has the biggest influence on the nonlinear errors of the position. Otherwise, the original errors of the mechanism are the main reason leading to more errors. Thus enhancing machining and assembling precision is an important method to enhance the precision of the mechanism.
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A novel method of plotting sensor sensitivity field and image reconstruction algorithm for electrical capacitance tomography system
CHEN De-yun, YANG Cong-jing, ZHENG Gui-bin, YU Xiao-yang, SUN Li-juan
Front. Mech. Eng.. 2006, 1 (2): 242-247.
https://doi.org/10.1007/s11465-006-0008-0
Sensor sensitivity field in electrical capacitance tomography is affected by the distribution of multiphase medium, which is the peculiarity of soft field. This brings great difficulty for image reconstruction. To improve the quality of image reconstruction, it is important to analyze the distribution of the sensitivity field. In this article, using the finite element method, we expound a kind of novel plotting pattern to field, which is the distribution of sensitivity field through computer simulation. From experiments and results of sensitivity field analysis, a novel method of image reconstruction based on genetic algorithms is presented. The finite element model is correct and simulation result is fine by adopting unequal interval plotting patterns. At the same time, the result of image reconstruction has high precision.
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