磁流变阻尼器密封机制研究

为解决大型阻尼器工作中传统密封方式磨损老化维护困难问题,针对磁流变阻尼器的工作特点,在磁流变阻尼器中充分利用新型智能材料磁流变液的优异特性,建立一种新型的非接触式磁密封机制。探讨非接触式磁密封机制的工作原理和具体结构,使用有限元仿真软件对阻尼器工作部位磁场进行仿真分析,建立磁密封理论耐压能力的理论计算模型。表明此种非接触式磁密封较传统密封方法具有高可靠性,超长维修间隔时间,摩擦小,效率高,无方向性的优势。     

Trajectory control of electro-hydraulic excavator using fuzzy self tuning algorithm with neural network

This paper presents the trajectory control of a 2DOF mini electro-hydraulic excavator by using fuzzy self tuning with neural network algorithm. First, the mathematical model is derived for the 2DOF mini electro-hydraulic excavator. The fuzzy PID and fuzzy self tuning with neural network are designed for circle trajectory following. Its two links are driven by an electric motor controlled pump system. The experimental results demonstrated that the proposed controllers have better control performance than the conventional controller. This paper was recommended for publication in revised form by Associate Editor Kyongsu Yi Le Duc Hanh received the B. S. degree in the department of Mechanical Engineering from Hochiminh City University of Technology in 2006, the M.Sc. degree in Mechanical and Automotive Engineering from University of Ulsan in 2008. His research interests are electro-hydraulic excavator, remote control, intelligent control. Kyoung Kwan Ahn received the B. S. degree in the department of Mechanical Engineering from Seoul National University in 1990, the M. Sc. degree in Mechanical Engineering from Korea Advanced Institute of Science and Technology (KAIST) in 1992 and the Ph.D. degree with the title “A study on the automation of out-door tasks using 2 link electro-hydraulic manipulator from Tokyo Institute of Technology in 1999, respectively. He is currently a Professor in the school of Mechanical and Automotive Engineering, University of Ulsan, Ulsan, Korea. His research interests are hybrid excavator, fluid power control, design and control of smart atuator using smart material, rehabilization robot and active damping control. He is a member of IEEE, ASME, SICE, RSJ, JSME, KSME, KSPE, KSAE, KFPS, and JFPS. Bao Kha Nguyen received the B. S. and M. S. degree from Hochiminh City University of Technology in 2001 and 2003, respectively, all in Automatic Control Engineering and the Ph.D. degree from University of Ulsan in 2006. His research interests focus on intelligent control, modern control theory and their applications, design and control of smart actuator systems. WooKeun Jo received the B.S. degree in the department of Mechanical and Automotive Engineering from University of Ulsan in 2007. And he matriculated M.S. at University of Ulsan. Currently, he’s syudying on it. His research interests focus on fluid control, welfare vehicle, mobile robot     

New approach to designing an MR brake using a small steel roller and MR fluid

A generated resistance force in the deformation process is considered to increase the resistance torque of a Magneto-Rheological (MR) brake when a variable stiffness material is rolled under the cylindrical form of a roller. This paper proposes a new approach to increase the resistance torque of an MR brake using a large-size magnetic particle which can be considered as the roller mentioned above (steel roller or rolling pin). Due to the cylindrical form of the roller and a line contact between the roller and the surface of the motion part, the steel roller can contribute to create a stronger magnetic field and larger resistance force than the conventional one. In this paper, a new MR brake is successfully designed to generate a higher braking torque than the conventional one, which only uses typical MR fluid. To verify the effect of the roller, the proposed MR brake is compared with the conventional one. Both of the MR brakes are designed with the same magnetic circuit and the same material parameters. The performance of the proposed MR brake is compared with that of the conventional MR brake. The proposed MR brake is verified to have about 200% larger torque than the conventional one. This paper was presented at the 9th Asian International Conference on Fluid Machinery (AICFM9), Jeju, Korea, October 16–19, 2007.recommended for publication in revised form by Associate Editor Yang Na Tran Hai Nam received his B.S. and M.S. degree in Mechanical Engineering from the Hochiminh City University of Technology in 2002 and 2005, respectively. He is currently a doctoral candidate in the Department of Mechanical and Automotive Engineering of the University of Ulsan in Ulsan, Korea. His research interests focus on machinery design, hydraulics, and smart actuator systems. Kyoung Kwan Ahn received the B.S. degree in the Department of Mechanical Engineering from Seoul National University in 1990, the M. Sc. degree in Mechanical Engineering from Korea Advanced Institute of Science and Technology (KAIST) in 1992 and the Ph.D. degree from Tokyo Institute of Technology in 1999, respectively. He is currently a Professor in the School of Mechanical and Automotive Engineering, University of Ulsan, Ulsan, Korea. His research interests are design and control of smart actuator using smart material, fluid power control and active damping control. He is a Member of IEEE, ASME, SICE, RSJ, JSME, KSME, KSPE, KSAE, KFPS, and JFPS.     

Bouc-Wen model parameter identification for a MR fluid damper using computationally efficient GA

A non-symmetrical Bouc-Wen model is proposed in this paper for magnetorheological (MR) fluid dampers. The model considers the effect of non-symmetrical hysteresis which has not been taken into account in the original Bouc-Wen model. The model parameters are identified with a Genetic Algorithm (GA) using its flexibility in identification of complex dynamics. The computational efficiency of the proposed GA is improved with the absorption of the selection stage into the crossover and mutation operations. Crossover and mutation are also made adaptive to the fitness values such that their probabilities need not be user-specified. Instead of using a sufficiently number of generations or a pre-determined fitness value, the algorithm termination criterion is formulated on the basis of a statistical hypothesis test, thus enhancing the performance of the parameter identification. Experimental test data of the damper displacement and force are used to verify the proposed approach with satisfactory parameter identification results.     

Modeling and testing of a field-controllable magnetorheological fluid damper

In this study, an experimental and a theoretical study were carried out to predict the dynamic performance of a linear magnetorheological (MR) fluid damper. After having designed and fabricated the MR damper, its dynamic testing was performed on a mechanical type shock machine under sinusoidal excitation. A theoretical flow analysis was done based on the Bingham plastic constitutive model to predict the behavior of the prototyped MR damper. The theoretical results were then validated by comparing them against experimental data, and it was shown that the flow model can accurately capture the dynamic force range of the MR damper. In addition to the flow model, a modified parametric algebraic model was proposed to capture the hysteretic behavior of the MR damper. The superiority of the proposed modified model was shown by comparing it with the Alg model as well as with a widely adopted modified Bouc-Wen model through an error analysis. It is observed that although all the three models are comparable at the excitation velocities of 0.05, 0.10, and 0.15 m/s, the mAlg model is remarkably successful at the highest excitation velocity of 0.2 m/s over the other two. The improvements in the predictions were found to be over 50%, relative to unmodified model especially at lower current inputs. Therefore, it was concluded that the present flow model can be successfully adopted to design and predict the dynamic behavior of MR dampers, while the mAlg model can be used to develop more effective control algorithms for such devices.     

Study on damping properties of magnetorheological damper

To research the properties of a new kind of smart controllable MR (magnetorheological) fluid, in this paper, the rheological models are discussed. On the basis of analyzing the structural forms of MR dampers, an improved structure of the MR damper is introduced; the properties of the novel MR damper are then tested. The experimental results reveal that the Herschel-Bulkley model predicts the force-velocity well; the damping properties of the ameliorated structure of the MR damper have improved; when the excitation is a trigonal signal, the MR damper reveals a thinning effect at high velocity; and when the excitation is a sinusoidal signal, the MR damper reveals a nonlinear hysteretic property between the damping force and relative velocity. Finally, the main unsolved problems have been put forward. __________ Translated from Ningxia Engineering Technology, 2005, 24 (4) (in Chinese)     

基于AR模型-分形维的磁流变减振器性能研究

建立了磁流变减振器的动力学方程,利用与其同阶的时间序列AR模型的对应关系,推导出基于时间序列的动态特性参数计算公式,在不同工况下振动实验检测获得时间序列,计算了动态特性参数、时间序列分形盒维数和系统特征根实部,以及这些参数间的相关系数,拟合了动态特性参数、分形盒维数、工况参数三者相互间的关系曲线,分析了磁流变减振器性能变化。分析结果表明,AR(2)模型对减振器振动信号有较高的模拟精度,基于时间序列AR模型的动态特性参数求解方法便捷有效;时间序列盒维数与动态特性参数间存在高度相关,可作为量化衡量系统振动平稳性和响应快速性综合动态特性的参数,可配合特征根选取磁流变减振器的最佳工况。     

磁流变液的流变性能及其工程应用

磁流变液是一种新兴的智能材料，由于其良好的可控性能和力学性能，因而可以广泛应用于航空航天、机械工程、汽车工程、精密加工工程、控制工程等领域。介绍磁流变液的研究进展和有关磁流变液及其性能的研究、磁流变液应用器件的发展情况，分析了磁流变液存在问题和未来发展展望。     

基于Bingham模型的磁流变阻尼器的优化设计

利用磁流变液这种智能材料设计制作阻尼耗能器件在近些年得到了广泛重视,但多数采用经验公式决定结构尺寸的方法具有片面性。本文利用Bingham轴对称模型并根据具体使用要求优化设计了阻尼器的结构参数,并编程进行了计算。根据计算结果制作的磁流变阻尼器经测试其性能达到了预期的要求,表明优化设计方法是正确可行的。     

Optimal control of structural vibrations using a mixed-mode magnetorheological fluid mount

In this work, a mixed-mode magnetorheological (MR) mount is proposed and applied to the vibration control of a flexible beam structure subjected to external disturbances. On the basis of non-dimensional Bingham number, an appropriate size of the MR mount is designed and manufactured. After experimentally evaluating the field-dependent damping force of the MR mount, a structural system consisting of a flexible beam and vibrating rigid mass is established. The governing equation of motion of the system is derived and expressed as a state space control model. A linear quadratic Gaussian (LQG) controller is then designed in order to attenuate the vibration of the structural system. The controller is empirically realized and control responses such as acceleration and displacement of the structural system are evaluated and presented in frequency domain.     

一种面向供应链的ATP系统(SC-ATP)建模与计算

增加客户订单承诺和履行的准确性 ,缩短订单处理提前期 ,提高客户满意度成为增强企业竞争力的关键。其核心就是先进的ATP订单承诺系统。文中提出了一个基于供应链的全球ATP系统 (SC ATP)的框架模型及算法描述 ,并详细讨论了其核心模块ATP、CTP和PTP的计算过程。最后以某药业为应用对象 ,用一个紧急订单的承诺实例对整个系统的应用作了说明。     

Optimisation of cobalt-based hardfacing in carbon steel using the fuzzy analysis for the robust design

In this paper, we present the application of the fuzzy logic analysis to a Taguchi orthogonal experiment for developing a robust model with high efficiency in multiple performance characteristics (MPCs) of the plasma transfer arc welding (PTAW) hardfacing process. It eliminates uncertain information and is a simple, effective, and efficient approach. A fuzzy logic system is used to simultaneously investigate relationships between various MPCs and to determine the efficiency of each trial of the Taguchi experiments. From the fuzzy inference process, we are able to determine the optimal setting of factor-levels for the MPCs. In addition, we also use the analysis of variance (ANOVA) to identify the significant factors, which coincide with findings from the fuzzy logic analysis and are found to account for about 79% of the total variance. Furthermore, a confirmation experiment of the optimal process is conducted, and it verifies that both individual performance characteristics and MPCs are successfully optimized and satisfy our desired levels of MPCs.     

Comparative study of modeling and identification of the pneumatic artificial muscle (PAM) manipulator using recurrent neural networks

The paper deals with the PAM manipulator modeling and identification based on autoregressive recurrent neural networks. For the first time, the most powerful types of neural-network-based nonlinear autoregressive models, namely, NNARMAX, NNOE and NNARX models, will be applied comparatively to the PAM manipulator identification. Furthermore, the evaluation of different nonlinear neural network auto-regressive models of the PAM manipulator with different number of neurons in hidden layer is completely discussed. On this basis, the merits of each identified model of the highly nonlinear PAM manipulator have been analyzed and compared. The results show that the nonlinear NNARX model yields better performance and higher accuracy than the other nonlinear NNARMAX and NNOE model schemes. These results can be applied to model and identify not only the PAM manipulator but also to control other nonlinear and time-varying industrial systems.     

Suggestion of MSTV (Modified-Stick-Transition-Velocity) model for hysteretic damping mechanism

To decrease vibration and noise in washing machines, lubricated friction dampers were installed. Although the structure of the friction damper is simple, it was not easy to develop a mathematical model for the dynamic behavior of the lubrication damper. To see the dynamic behavior of a friction damper, physical tests were carried out via a material testing machine by changing exciting amplitudes and frequencies. Complicated curves of spring characteristics and damping showed a hysteretic behavior. In this paper, a reasonable model for a friction damper is suggested. To model the hysteretic behavior of a friction damper, a Coulomb friction model was first applied. To get a refined model for stick and transition, an STV (stick transition velocity) model was analyzed. To develop a more accurate mathematical model, an MSTV (modified stick transition velocity) model was proposed. In the MSTV model, the friction force could be changed due to the velocity of the damper, and the damping force was calculated according to the relative velocity between the external displacement and the deformation of the sponge in the friction damper. The MSTV model was in a good agreement with the experimental results.     

Dual colorimetric and fluorescent determination of iron (III) using a novel squaraine dye

A novel squaraine dye, 6-carboxy-2-[[3-[1,3-dihydro-3,3-dimethy-1-ethyl-2H-indol-2-ylidene)methyl]-2-hydroxy-4-oxo-2-cyclobuten-1-ylidene]methyl]-3,3-trimethy-3H-indolium, has been synthesized. The squaraine dye was found to be a dual colorimetric and fluorescent probe for the determination of iron (III) in CH₃CH₂OH/H₂O (4:1, v/v) exhibiting high selectivity and sensitivity. The binding of squaraine dye +Fe³⁺ was studied by a Job’s plot and Fourier transform infrared and ¹H nuclear magnetic resonance spectroscopies. The result indicates that the squaraine dye may be utilized as a naked-eye and real-time probe for the efficient determination of Fe^3+.     

Tris(2-octyldodecyl)cyclopentane,a low volatility,wide liquid range,hydrocarbon fluid

Tris(2–octyldodecyl)cyclopentane, prepared by the hydrogenation of the product of alkylation of cyclopentadiene by 2–octyldodecanol, is a wide liquid range hydrocarbon fluid (pour point, −57°C; vapour pressure at 20 °C, 1 × 10⁻¹²). This new fluid compares favourably with other hydrocarbons and per fluoropolyethers (PFPAEs) in properties useful for vacuum applications in which low temperature fluidity and low volatility are important properties. It is half the density of PFPAE and exhibits inhibitable oxidation properties similar to other hydrocarbons. The pressure-viscosity coefficient is similar to those of PAOs and PFPAEs.     

Application of multi-objective controller to optimal tuning of PID gains for a hydraulic turbine regulating system using adaptive grid particle swam optimization

A hydraulic turbine regulating system (HTRS) is one of the most important components of hydropower plant, which plays a key role in maintaining safety, stability and economical operation of hydro-electrical installations. At present, the conventional PID controller is widely applied in the HTRS system for its practicability and robustness, and the primary problem with respect to this control law is how to optimally tune the parameters, i.e. the determination of PID controller gains for satisfactory performance. In this paper, a kind of multi-objective evolutionary algorithms, named adaptive grid particle swarm optimization (AGPSO) is applied to solve the PID gains tuning problem of the HTRS system. This newly AGPSO optimized method, which differs from a traditional one-single objective optimization method, is designed to take care of settling time and overshoot level simultaneously, in which a set of non-inferior alternatives solutions (i.e. Pareto solution) is generated. Furthermore, a fuzzy-based membership value assignment method is employed to choose the best compromise solution from the obtained Pareto set. An illustrative example associated with the best compromise solution for parameter tuning of the nonlinear HTRS system is introduced to verify the feasibility and the effectiveness of the proposed AGPSO-based optimization approach, as compared with two another prominent multi-objective algorithms, i.e. Non-dominated Sorting Genetic Algorithm II (NSGAII) and Strength Pareto Evolutionary Algorithm II (SPEAII), for the quality and diversity of obtained Pareto solutions set. Consequently, simulation results show that this AGPSO optimized approach outperforms than compared methods with higher efficiency and better quality no matter whether the HTRS system works under unload or load conditions.     

Predictability of high-performance spindles using a complete thermo-elastohydrodynamic lubrication (TEHD) solution

Spindles experience problems related to increased power and velocity, and can have very high power consumption. The work reported here is aimed at improving design methods for high-performance spindles and machine-tool bearings, and is aimed at determining the influence, of the oil quantity supplying the contact, on power consumption and on contact temperature. A finite element program, TACT, can efficiently predict power loss and the thermal state of machine-tool bearings, and the remaining unknown in these thermo-piezo-viscous-elastic (TPVE) calculations is inlet oil film height. The authors address this problem and, within the context of this work, develop a high-speed ISO 50 spindle which has a thin-wall bearing housing, and is ‚thermally tuned‚, so avoiding thermal instability, while the preload stays constant. Its experimentally determined power consumption values agree well with the TPVE prediction for an assumed inlet film height of 0.5 μm.     

夏季短期电力负荷预测的MGM（1，n）建模及应用

在对浙江省嘉兴市的历史气象数据进行分析的基础上，提出了一种带气象因素校正的灰色短期负荷预测模型，称为MGM（1，n）模型。实例分析表明，这种方法能较大地提高夏季短期负荷的预测精度，是预测夏季短期电力负荷的一种行之有效的方法。     

Simultaneous measurement of magnetic vortex polarity and chirality using scanning electron microscopy with polarization analysis (SEMPA)

The magnetic vortex structure is an equilibrium configuration frequently found in patterned magnetic nanostructures. It is characterized by an in-plane curling of the magnetization with clockwise or anticlockwise chirality and by an out-of-plane vortex core that can have a positive or negative polarity. The small size of the vortex core, on the order of 10 nm, makes it technologically interesting due to potential data storage, but also difficult to measure or image directly. In this work, we used Scanning Electron Microscopy with Polarization Analysis (SEMPA) to directly image magnetic vortex cores in patterned NiFe/Ta bilayer structures. With SEMPA we can simultaneously measure the in-plane and the out-of-plane component of the surface magnetization and thereby determine both the vortex chirality and the vortex core polarity in a single measurement. Our magnetic simulation of the vortex core, considering only the exchange and magnetostatic energy, is in good agreement with the SEMPA measurement of the magnetization when other experimental factors are taken into account.