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A Further Discussion on Trends in the Development of Advanced Manufacturing Technology
YANG Shu-zi, WU Bo, LI Bin
Front. Mech. Eng.. 2006, 1 (1): 1-5.
https://doi.org/10.1007/s11465-005-0002-y
This paper is a supplement to Trends in the Development of Advanced Manufacturing Technology (Yang and Wu in Chin. J. Mech. Eng., 39: 73, 2003) but delves deeper into it. It first points out the strategic status of manufacturing industry in state development. Then, a detailed analysis is given on the features and trends in the development of advanced manufacturing technology in a total of 12 points from three aspects: precision, extreme, and culture from the aspect of the product itself; green, rapidness, saving, and efficiency during the manufacturing process; and digit, auto, integration, networking, and intelligence in view of the manufacturing method. In addition, it emphasizes that all the above aspects should be based on two base points: manufacture and machinery. Finally, it puts forth the guiding ideologies for the development of advanced manufacturing technology and the aspects China should give priority to in development, while stressing on the principles of independence, innovation and human orientation.
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Nanopositioning and Nonlinearity Compensation for Step Imprint Lithography Tool
LU Bing-heng, LIU Hong-zhong, DING Yu-cheng, WANG Li, QIU Zhi-hui
Front. Mech. Eng.. 2006, 1 (1): 6-13.
https://doi.org/10.1007/s11465-005-0003-x
In this paper, the motion mode and nanopositioning accuracy in the step imprinting lithography process are presented, and the positioning errors different from the traditional errors, such as the gap error existing in the hinges of the stage structure and the random error produced during the process of the stage position adjustment, are analyzed. To avoid and eliminate these nonlinearity errors, radial basis function proportional integral derivative and position control algorithms are introduced into the macroand microdriving processes, respectively. The innovation of this driving method is that the motion locus is monotone, nonoscillatory, and a multistep approaching target, which eliminates the root of the random error by single direction driving mode and avoids the backlash error through preloading function. Driving experiments of different motion ranges prove that this nonlinearity compensation is very effective and the positioning accuracy during the step imprinting process can be improved up to 10 nm.
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Superunderactuated Multifingered Hand for Humanoid Robot
ZHANG Wen-zeng, CHEN Qiang, SUN Zhen-guo, XU Lei
Front. Mech. Eng.. 2006, 1 (1): 33-39.
https://doi.org/10.1007/s11465-005-0015-6
A novel underactuated finger mechanism was designed. Finger mechanism was incorporated into a humanoid robot hand to obtain more degrees of freedom with less actuators and good grasping functions with shape adaptation, therefore decreasing the requirements for the control system. A novel superunderactuated multifingered hand (TH-2 Hand) for a humanoid robot was designed based on a previous underactuated finger mechanism. The TH-2 Hand was attached to a humanoid robot because of its high personification, superunderactuation, compactness, easy real-time control, small volume, light weight, and strong grasping function.
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Constitutive Model for an FCC Single-Crystal Material
DING Zhi-ping, LIU Yi-lun, YIN Ze-yong, YANG Zhi-guo, CHENG Xiao-ming
Front. Mech. Eng.. 2006, 1 (1): 40-47.
https://doi.org/10.1007/s11465-005-0012-9
Taking into account the effects that the components of tension stresses couple with components of torsion stresses when off-axis loads are applied to orthotropic materials, Hill s yield criterion for plastically orthotropic solids is modified by adding an invariant that is composed of the product item of quadratic components of the deviatoric stress tensor, and a new yield criterion is put forward in terms of the characteristics of the face-centered cubic (FCC) single-crystal material. The correlation of prediction and experiments is very good, and the new criterion is used to predict the yield stresses of an internal single-crystal, Nickel-based superalloy, DD3, which is more accurate than that of Hill s at 760?C. Equivalent stress and strain that adapt to the new criterion are defined. Thinking of the yield function as a plastic potential function from the associated flow rule, the elastic plastic constitutive model for the FCC single-crystal material is constructed, and the corresponding elastic plastic matrix is educed. The new yield criterion and its equivalent stress and strain will be reduced to Von Mises yield criterion and corresponding equivalent stress and strain for isotropic materials.
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Automatic Design Theory and Realization of Kinematic Schemes for Mechanism System
YE Zhi-gang, ZOU Hui-jun, GUO Wei-zhong, HU Song, TIAN Yong-li, XU Yong
Front. Mech. Eng.. 2006, 1 (1): 48-55.
https://doi.org/10.1007/s11465-005-0014-7
Based on an analysis of mechanism combination methods of a current mechanism system kinematic scheme, input/output kinematic behavior and their constraint relations were proposed to represent the kinematic behavior knowledge of a mechanism system. Furthermore, a tree structure of a kinematic behavior decomposition process for a mechanism system was provided. Considering multiple outputs for a mechanism system, the matching algorithm and the attributes propagation method of kinematic behavior were used to generate a mechanism combination scheme. Its intermediate design solution and the constraint relations between input and output are generated to fill the common blackboard. Moreover, using information in the blackboard as input motion, the behavior attributes of other process actions are transmitted to attribute items of the blackboard, which finally enables a computer-aided automatic design process of a mechanism system kinematic scheme. To avoid the problem of schemes combination explosion caused by unbounded depth in the search process, bounded depth-first search was used to control the number of expanded hierarchies for a design tree. Finally, an example was given to show its feasibility and solution efficiency.
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Kinematic Model Building and Servo Parameter Identification of 3-HSS Parallel Mechanism
YANG Zhi-yong, WU Jiang, HUANG Tian, NI Yan-bing
Front. Mech. Eng.. 2006, 1 (1): 60-66.
https://doi.org/10.1007/s11465-005-0019-2
Aiming at a parallel mechanism with three degrees of freedom, a method for dynamic model building and the parameter identification of its servosystem is presented. First, the reverse solution models of position, velocity, and acceleration of parallelogram branch structure are deduced, and then, its dynamic model of a rigid body is set up by using the virtual work principle. Based on the above model, a method to identify the servo parameter of the parallel mechanism is put up. In this method, the triangle-shaped input with variable frequency is adopted to offset the disadvantages of pseudorandom number sequence in parameter identification, such as dramatically changing the vibration amplitude of the motor, easily impacting the motor that results in its velocity loop to easily open, and so on. Moreover, the rotary inertia can also be identified by the additive mass. The abovementioned data will lay a solid foundation for the optimum performance of the system in the whole workspace.
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Effects of Boundary Condition and Helix Angle on Meshing Performance of TI Worm Gearing
SUN Yue-hai, DUAN Lu-qian, WANG Shu-ren, ZHANG Ce
Front. Mech. Eng.. 2006, 1 (1): 90-95.
https://doi.org/10.1007/s11465-005-0006-7
To exactly describe the contact state and contact area of tooth surface of toroidal involute (TI) worm gearing, the authors introduced boundary condition into contact line analysis.With helix angle chosen as parameter, the criterion for the existence of meshing boundary line on the surface of TI worm gearing is derived. Results show that there can be four situations for meshing boundary line on the tooth surface of gear, namely, inexistence of meshing boundary line, a unique line, two lines, and two coincident lines. If the helix angle is equal to or slightly smaller than the bigger angle, which makes two meshing boundary lines superpose, a preferable meshing performance is obtained. Computer simulation proves the validity of the above conclusion.
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Influence of the Mechanical Seals on the Dynamic Performance of Rotor–Bearing Systems
XU Hua, ZHU Jun
Front. Mech. Eng.. 2006, 1 (1): 96-100.
https://doi.org/10.1007/s11465-005-0008-5
In this paper, to consider the effects of mechanical seals, a lumped-mass model and the transfer matrix method are used to establish the equations for the dynamics performance of rotor bearing system. The general inverted iteration method is also used to solve the eigenvalue problem of these equations. To check the response of the rotor bearing system under unbalance motivation, the Gauss method is used to calculate the dynamic response of the constrained vibration. The results, based on the dynamic properties calculation of a typical mechanical spiral seal, such as stiffness coefficients and damping coefficients, exert the influence of the mechanical seal on the rotor bearing system of the high-speed machinery. Meanwhile, some structure parameters that may affect the dynamic performance and forced vibration under unbalance motivation of the rotor bearing system considering mechanical seals are analyzed in the paper. The analysis results show that the mechanical seal more or less has effects on the rotor bearing system. The mechanical seal has much more effects on the flexible rotor bearing system than on the rigid one. For instance, in a certain case, if the effects of the mechanical seal were taken into account, the system s critical speed may increase by 70 80%.
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Digital Readout System for Micromachined Gyroscope and Analysis for its Demodulation Algorithm
ZHOU Bin, GAO Zhong-yu, CHEN Huai, ZHANG Rong, CHEN Zhi-yong
Front. Mech. Eng.. 2006, 1 (1): 106-110.
https://doi.org/10.1007/s11465-005-0016-5
A new digital readout system for micromachined gyroscope has been proposed to implement flexible parameter adjustment, improve the control performance of gyroscope, and make error compensation. By digitalizing the output of the gyroscope, this system uses a floating-type digital signal processor (DSP) to process the signal demodulation and achieve the feedback control of the gyroscope. Therefore, the small change of capacitance in the micromachined gyroscope can be detected. A new demodulation algorithm of least mean square demodulation (LMSD) has been developed inside DSP. Simulation and measurement results show that LMSD can improve 29% of the noise performance compared with the typical multiplication method. In air pressure, a kind of vibration-wheel micromachined gyroscope has achieved a noise level of 0.0073 deg s-1z(z-1/2 over the 100-Hz bandwidth by using this digital readout technology.
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Research on Microelectromagnetic Relays
LI De-sheng, LIU Ben-dong
Front. Mech. Eng.. 2006, 1 (1): 111-114.
https://doi.org/10.1007/s11465-005-0013-8
A new microelectromagnetic relay is presented and fabricated based on micromachining technology, aiming at the miniaturization and high manufacturing efficiency of electromagnetic relays. This microrelay is composed of a lower magnetic circuit, a planar exciting coil, and an upper magnetic armature. A complete magnetic circuit is composed, and the ON and OFF states are controlled by the current of the exciting coil. The dimension of this microrelay is 5 mm ? 5 mm ? 0.4 mm. The fabrication process mainly includes lithography, sputtering, electroplating, etching, sacrifice-layer technology, etc. Electromagnetic force is calculated theoretically. The calculation results are used for the optimization design of the armature and the number of turns of the exciting coil. A microelectromagnetic relay is fabricated and the initial test results are given. The resistance of the exciting coil is about 300 Ω. The switch-on state resistance is about 1.7 Ω at an exciting current of about 50 mA.
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