Jun 2011, Volume 6 Issue 2
    

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  • FEATURE ARTICLE
    Fengfeng XI, Yuwen LI, Hongbo WANG

    This paper presents a method for the design and analysis of reconfigurable parallel robots. The inherent modularity in a parallel robot lends itself as a natural candidate for reconfiguration. By taking the branches as building blocks, many modular parallel robots can be constructed, from which a reconfigurable parallel robot can be realized. Among three types of reconfigurations, namely, geometry morphing, topology morphing, and group morphing, the method presented here is for the last two reconfigurations, thereby advancing the current research that is mainly limited to geometry morphing. It is shown that the module-based method not only provides a systematic way of designing a reconfigurable parallel robot, but also offers a unified modeling for robot analysis. Two examples are provided, one showing the topology morphing and the other showing the group morphing.

  • REVIEW ARTICLE
    Lin LIU, Jing LIU

    Biomedical sensors have been widely used in various areas of biomedical practices, which play an important role in disease detection, diagnosis, monitoring, treatment, health management, and so on. However, most of them and their related platforms are generally not easily accessible or just too expensive or complicated to be kept at home. As an alternative, new technologies enabled from the mobile phones are gradually changing such situations. As can be freely available to almost everyone, mobile phone offers a unique way to improve the conventional medical care through combining with various biomedical sensors. Moreover, the established systems will be both convenient and low cost. In this paper, we present an overview on the state-of-art biomedical sensors, giving a brief introduction of the fundamental principles and showing several new examples or concepts in the area. The focus was particularly put on interpreting the technical strategies to innovate the biomedical sensor technologies based on the platform of mobile phones. Some challenging issues, including feasibility, usability, security, and effectiveness, were discussed. With the help of electrical and mechanical technologies, it is expected that a full combination between the biomedical sensors and mobile phones will bring a bright future for the coming pervasive medical care.

  • RESEARCH ARTICLE
    Kirsten BOBZIN, Lidong ZHAO, Thomas SCHLAEFER, Thomas WARDA

    High-energy ball milling is an effective method to produce nanocrystalline oxides. In this study, a conventional ZrO2-7%Y2O3 spray powder was ball-milled to produce nanocrystalline powders with high levels of crystalline disorders for deposition of thermal barrier coatings. The powder was milled both with 100Cr6 steel balls and with ZrO2-3%Y2O3 ceramic balls as grinding media. The milling time was varied in order to investigate the effect of the milling time on the crystallite size. The powders were investigated in terms of their crystallite sizes and morphologies by X-ray diffraction analysis (XRD), scanning electron microscopy (SEM) and transmission electron microscopy (TEM). The results show that under given milling conditions the powder was already nanostructured after 40 min milling. The crystallite size decreased significantly with increasing milling time within first 120 min. After that, a further increase of milling time did not lead to a significant reduction of the crystallite size. Ball-milling led to lattice microstrains. Milling with the steel balls resulted in finer nano-sized crystal grains, but caused the contamination of the powder. The nano-sized crystal grains coarsened during the heat-treatment at 1250°C.

  • RESEARCH ARTICLE
    Giuseppe CARBONE

    Stiffness can be considered of primary importance in order to guarantee the successful use of any robotic system for a given task. Therefore, this paper proposes procedures for carrying out both numerical and experimental estimations of stiffness performance for multibody robotic systems. The proposed numerical procedure is based on models with lumped parameters for deriving the Cartesian stiffness matrix. Stiffness performance indices are also proposed for comparing stiffness performance. Then, an experimental procedure for the evaluation stiffness performance is proposed as based on a new measuring system named as Milli-CATRASYS (Milli Cassino Tracking System) and on a trilateration technique. Cases of study are reported to show the soundness and engineering feasibility of both the proposed numerical formulation for stiffness analysis and experimental validation of stiffness performance.

  • RESEARCH ARTICLE
    Guang GUO, Bo WU, Shuzi YANG

    A new adaptive job-insertion based heuristic is presented to minimize the mean flowtime in a dynamic flowshop consisting of m machines. Job orders arrive to the system randomly, and the job arrival or release dates are not known in advance. The heuristic is derived by inserting new jobs into the scheduled sequence as needed when the machine becomes free. Computation results indicate that the proposed heuristic performs 2.7%–10.8% better than the SPT dispatching rule, which is currently one of the most effective methods for minimizing the mean flowtime in dynamic flowshops.

  • RESEARCH ARTICLE
    Yanli LIN, Xiaohui SI, Fulei CHU

    Crack on a shaft is one of the common damages in a rotor system. In this paper, transverse vibrations are calculated to compare the influences of transverse crack and slant crack on the rotor system. Results show that the vibration amplitude of the rotor system with a 45° slant crack on the shaft is larger than that with a transverse crack when the two types of crack have the same depth and the rotor system runs in the same condition. Stability and dynamic characteristics of the rotor system with a 45° slant crack on the shaft under torsional excitation are analyzed by considering opening and closing of the crack. It is shown that the instability of the transverse vibration of the rotor system increases with increasing difference between the bending stiffness in two main directions, and the vibration is stable when the two bending stiffness are identical. The spectrum analysis of the steady-state response reveals that the gravity and the eccentricity produce different frequency components, and when the two bending stiffness are identical, the multiple frequency components of the torsional excitation disappear. Further investigation shows that the vibration amplitudes in combined frequencies increase rapidly in transversal, torsional, and axial vibration with increasing slant crack depth. The results are helpful for the understanding the dynamic behavior of a rotor system with a slant crack on a shaft and can be used for the detection of the slant crack on a shaft.

  • RESEARCH ARTICLE
    Rui ZHUO, Guanglan LIAO, Wenliang LIU, Lei NIE, Tielin SHI

    The process of patterned wafer bonding using ultraviolet (UV) adhesive as the intermediate layer was studied. By presetting the UV adhesive guide-layer, controlling the thickness of the intermediate layer (1– 1.5 μm), appropriate pre-drying temperature (60°C), and predrying time (6 min), we obtained the intermediate layer bonding of patterned quartz/quartz. Experimental results indicate that patterned wafer bonding using UV adhesive is achieved under room temperature. The process also has advantages of easy operation, low cost, and no plugging or leakage in the patterned area after bonding. Using the process, a microfluidic chip for red blood cell counting was designed and fabricated. Patterned wafer bonding using UV adhesive will have great potential in the fabrication of microfluidic chips.

  • RESEARCH ARTICLE
    M. H. KORAYEM, H. N. RAHIMI

    The aim of the paper is to analyze the nonlinear dynamics of robotic arms with elastic links and joints. The main contribution of the paper is the comparative assessment of assumed modes and finite element methods as more convenient approaches for computing the nonlinear dynamic of robotic systems. Numerical simulations comprising both methods are carried out and results are discussed. Hence, advantages and disadvantages of each method are illustrated. Then, adding the joint flexibility to the system is dealt with and the obtained model is demonstrated. Finally, a brief description of the optimal motion generation is presented and the simulation is carried out to investigate the role of robot dynamic modeling in the control of robots.

  • RESEARCH ARTICLE
    Guilian YI, Yunkang SUI, Jiazheng DU

    To reduce vibration and noise, a damping layer and constraint layer are usually pasted on the inner surface of a gearbox thin shell, and their thicknesses are the main parameters in the vibration and noise reduction design. The normal acceleration of the point on the gearbox surface is the main index that can reflect the vibration and noise of that point, and the normal accelerations of different points can reflect the degree of the vibration and noise of the whole structure. The K-S function is adopted to process many points’ normal accelerations as the comprehensive index of the vibration characteristics of the whole structure, and the vibration acceleration level is adopted to measure the degree of the vibration and noise. Secondary development of the Abaqus preprocess and postprocess on the basis of the Python scripting programming automatically modifies the model parameters, submits the job, and restarts the analysis totally, which avoids the tedious work of returning to the Abaqus/CAE for modifying and resubmitting and improves the speed of the preprocess and postprocess and the computational efficiency.

  • RESEARCH ARTICLE
    Xiaoli XU, Qiushuang LIU

    To solve many key technical problems during the development of modern instrumentation system integration and provide a new mode and fundamental technical equipment for the research and development (R&D) of modern instrumentation products, based on the concept of an instrumentation flexible developing system (IFDS), this paper discusses the creation and open flexible integration mechanism, perfects the integrated supporting environment and integrated system of the flexible interconnection, and constructs the new flexible integrated system. Based on the operation mechanism of the modern instrumentation developing system and the research and optimization of the rapid integration design method, the paper emphasizes the dynamic integrating method of multiple types of knowledge in a modern instrument R&D system, to effectively utilize the rich integrated resource and achieve rapid integration of the system. Applications show that the new IFDS can improve the integration level and efficiency of R&D of the modern instrumentation system, enforce the reliability of the system, shorten the R&D period, and reduce the development costs.

  • RESEARCH ARTICLE
    Shoujun CHEN, Lianxin GAO, Qi AN

    This paper presents a new calculation method that can calculate the load distribution on pipe threaded connections under tension load. On the basis of elastic mechanics, the new method was developed by analyzing each thread tooth, and a new deformation and covariant equation by making a mechanics analysis on each thread tooth was obtained. Compared with the traditional method proposed by the previous references, the new deformation and covariant equation could be used to describe the relation between the previous and the next thread tooth. By applying the new method on the sample of P-110S pipe threaded connection, the obtained results show that the load on thread tooth mainly concentrates on the four or five threads engaged and the middle teeth were not utilized well to bear the loads. The model offers a new way to calculate the loads carried on the thread teeth under tension load.

  • RESEARCH ARTICLE
    Houjun SU, Tielin SHI, Fei CHEN, Shuhong HUANG

    This paper introduces the basic conception of information fusion and some fusion diagnosis methods commonly used nowadays in rotating machinery. From the thought of the information fusion, a new quantitative feature index monitoring and diagnosing the vibration fault of rotating machinery, which is called distance of information entropy, is put forward on the basis of the singular spectrum entropy in time domain, power spectrum entropy in frequency domain, wavelet energy spectrum entropy, and wavelet space feature entropy in time-frequency domain. The mathematic deduction suggests that the conception of distance of information entropy is accordant with the maximum subordination principle in the fuzzy theory. Through calculation it has been proved that this method can effectively distinguish different fault types. Then, the accuracy of rotor fault diagnosis can be improved through the curve chart of the distance of information entropy at multi-speed.

  • RESEARCH ARTICLE
    Zhaomiao LIU, Qiuying JIN, Chengyin ZHANG, Feng SHEN

    A 3D model of hydrostatic turntable’s oil chamber is established to investigate the lubricants performance with different rheological properties by using FLUENT software and the finite volume method. Newtonian oil and non-Newtonian oil’s performance under varied speeds are compared on the large size hydrostatic turntable system considering the temperature-viscosity relationship and pressure-viscosity relationship. The results show that the property of non-Newtonian fluid viscosity influenced by shear rate largely affects the lubricants performance for most oil added polymer additives. Lubricants cannot simply be regarded as Newtonian fluid. The shear thickening non-Newtonian fluid has a better work property. The results are important to design a large size and high-speed hydrostatic support system, choose lubricant oils, and investigate oil film’s work properties.

  • RESEARCH ARTICLE
    Dashuai ZHOU, Liangsheng WU, Yichuan XIAO

    Reducing the manufacturing time is the trend of high-precision manufacturing, and the precision of a work-piece is very important for manufacturing industry. The high-speed motorized spindle is the most critical part and becoming more widely used in the machine tool at present, and its precision may affect the overall performance of high-speed cutting. Most of the studies on high-speed cutting are focused on the cutting force, the vibration of the spindle and effects of the spindle’s thermal deformations; hence, how to roundly measure and objectively evaluate high-speed spindle is an imminence question of it because the comprehensive dynamic properties and evaluation system of spindles directly affect the cutting ability of the whole machine tool before they are manufactured. This paper presents a comprehensive measurement and evaluation system of high-speed motorized spindle, which reflects the overall performance of motorized spindle and bases on international standard.