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     

Vibration control of a structure using Magneto-Rheological grease damper

This paper describes an application study of Magneto-Rheological (MR) grease damper to a structure with three stories. MR fluid is known as one of successful smart materials whose rheological properties can be varied by magnetic field strength, and has been applied to various kinds of device such as dampers, clutches, engine mounts, etc. However, ferromagnetic particles dispersed in MR fluid settle out of the suspension after a certain interval due to the density difference between the particles and their career fluid. To overcome this defect, we have developed a new type of controllable working fluid using grease as the career of magnetic particles. Network of thickener in grease is expected to hold the magnetic particles and prevent them from settled down. No or little sedimentation was observed in MR grease whose characteristics could be controlled by the magnetic field strength. MR grease was introduced into a cylindrical damper and its performance was studied. As a result, it was confirmed that the damping force of MR grease damper could be controlled by the applied electric current to the coil in the cylinder of damper. Furthermore, vibration response of a three-story model structure equipped with MR grease damper was investigated experimentally, and it was shown that MR grease damper worked effectively as a semi-active damper.     

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)     

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。     

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.     

Reliability analysis of a phaser measurement unit using a generalized fuzzy lambda-tau(GFLT) technique

Nowadays power consumption is increasing day-by-day. To fulfill failure free power requirement, planning and implementation of an effective and reliable power management system is essential. Phasor measurement unit(PMU) is one of the key device in wide area measurement and control systems. The reliable performance of PMU assures failure free power supply for any power system. So, the purpose of the present study is to analyse the reliability of a PMU used for controllability and observability of power systems utilizing available uncertain data. In this paper, a generalized fuzzy lambda-tau (GFLT) technique has been proposed for this purpose. In GFLT, system components' uncertain failure and repair rates are fuzzified using fuzzy numbers having different shapes such as triangular, normal, cauchy, sharp gamma and trapezoidal. To select a suitable fuzzy number for quantifying data uncertainty, system experts' opinion have been considered. The GFLT technique applies fault tree, lambda-tau method, fuzzified data using different membership functions, alpha-cut based fuzzy arithmetic operations to compute some important reliability indices. Furthermore, in this study ranking of critical components of the system using RAM-Index and sensitivity analysis have also been performed. The developed technique may be helpful to improve system performance significantly and can be applied to analyse fuzzy reliability of other engineering systems.     

结合模糊(C+P)均值聚类和SP-V-支持向量机的TSK分类器

为获得具有模糊规则自适应约简性能和较好的泛化性能的TSK分类器,本文提出了一种结合模糊(C+P)均值聚类(FCPM)算法和SP-V-支持向量机(SVM)分类算法来构建TSK(Takagi-Sugeno-Kang)分类器的方法。该方法首先用FCPM聚类算法对训练数据进行聚类;然后根据聚类结果确定TSK分类器的模糊规则前件中的高斯隶属度函数的中心和宽度参数;最后采用成组稀疏约束SP-V-SVM算法对模糊规则后件参数进行学习,该算法不仅改善了系统的泛化性能,还使系统具有模糊规则自适应约简功能,使得系统更为紧凑。与相关算法在UCI和IDA标准数据集分类实验中的模糊规则数和分类性能对比表明:用提出的分类算法所构造的TSK分类器不仅具有较好的分类性能,而且模糊规则数少,有利于构建更为紧凑的模糊分类系统。     

Optimization of bone drilling parameters using grey-based fuzzy algorithm

In this article a modified algorithm (grey based fuzzy algorithm) is used to optimize multiple performance characteristics in drilling of bone. Experiments have been performed with different cutting conditions using full factorial design. The quality parameters considered are temperature, force and surface roughness. Grey relational analysis (GRA) coupled with fuzzy logic is employed to obtain a grey fuzzy reasoning grade (GFRG) combining all the quality characteristics. The highest GFRG is obtained for the feed rate of 40 mm/min and the speed of 500 rpm and is the optimal level. Analysis of variance (ANOVA) carried out to find the significance of parameters on multiple performance characteristics revealed that the feed rate has the highest contribution on GFRG followed by the spindle speed. The optimum level of the process parameters obtained is validated by the confirmation experiment.     

并联液流通道结构的磁流变制动器电磁场和温度场特性分析

为了改善磁流变制动器的制动性能,提出一种并联液流通道结构的磁流变制动器。通过合理利用材料的导磁特性,使磁流变制动器内部的3层轴向阻尼间隙均被利用,有效提升了制动性能。建立了并联液流通道结构的磁流变制动器的力学模型,并对磁流变制动器进行了电磁场仿真分析;由仿真分析可知,磁流变制动器在转速为400 r/min时,最大制动转矩达到76.11 N·m。建立了磁流变制动器的温度场数学模型,对磁流变制动器的热源及生热率进行了理论分析;瞬态温度场仿真结果表明,在制动周期内磁流变制动器最高温度保持在磁流变液的工作范围内;因此并联液流通道结构的磁流变制动器能够正常工作。     

Differential finishing of freeform surfaces (knee joint) using R-MRAFF process and negative replica of workpiece as a fixture

It is difficult and challenging to achieve uniform nanoscale surface finish in the contact zone, particularly on freeform (or sculptured) surfaces having different curvatures at different locations. Femoral (or, Knee joint component) is one of such biomedical freeform component which has complex profile along its curvature. Surface conditions of a femoral decide the life of the implant and they play a crucial role in its functionality. The variation in surface roughness of the femoral should be minimum in the contact zone. For this purpose, a special tooling is being proposed for rotational magnetorheological abrasive flow finishing (R-MRAFF) process. A negative replica of the workpiece (knee joint) as a tool (or a fixture) is used so that the medium flow velocity in the fluid flow channel is almost constant (or minimum possible variations) along the medium flow direction. It is able to do differential finishing also along the curvature. In addition, pulsating magnetic field has been used to generate vibrations in the medium in the finishing zone so that the possibility of fresh abrasive particles interacting with the surface of femoral is high. The surface finish has been achieved ranging from 26 nm to 62 nm using the proposed finishing technique and negative replica of the workpiece (femoral) as a fixture.     

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.     

Design and fabrication of a novel polishing tool for finishing freeform surfaces in magnetic field assisted finishing (MFAF) process

Surface finish is a critical requirement for different applications in industries and research areas. Freeform surfaces are widely used in medical, aerospace, and automobile sectors. Magnetic field assisted finishing process can be used very efficiently to finish freeform surfaces. In this process, magnetorheological fluid is used as the polishing medium and permanent magnet is used to control its rheological properties to generate finishing force during polishing. To avail sufficient magnetic field in the finishing zone, it is necessary to design an optimum polishing tool. In the present study, a specially designed polishing tool is designed using a finite element based software package (Ansys Maxwell^®) based on Maxwell equations. At first, dimension of the permanent magnet is determined for designing optimum tool geometry. After that, dimension and configuration of the magnet fixture are optimized. A special type of metal named mu-metal which is a nickel-iron based alloy is selected for magnet fixture due to its magnetic-field shielding property. Mu-metal directs the magnetic flux lines in such a way that in the finishing zone the magnetic flux can be concentrated on the workpiece surface required for finishing. Also, the Mu-metal magnet fixture shields the magnetic field from outside environment so that MR fluid as well as any surrounding magnetic materials do not stick to the polishing tool. Experiments are carried out to validate the Maxwell simulation results to compare the magnetic flux distribution on the workpiece surface which shows good agreement between them. Also, finishing of flat titanium workpieces are carried out and it is found that the novel polishing tool has the capability to finish the workpieces in the nanometer range.     

Hybrid position/force control of Stewart Manipulator using Extended Adaptive Fuzzy Sliding Mode Controller (E-AFSMC)

A new and effective control method is proposed for the hybrid position/force control of a Stewart Manipulator (SM). The control approach can be divided into the two parts, the first is an estimation of contact parameters between the robot and environment and the second one is the force control of manipulator according to estimated parameters. Hunt–Crossley nonlinear model is considered to describe the normal force in the contact region and Modified Extended Kalman Filter (MEKF) is used for estimating contact parameters. Extended Adaptive Fuzzy Sliding Mode Controller (E-AFSMC) is designed to hybrid position/force control of SM in the presence of state-dependent uncertainties. The proposed method is verified numerically, showing the effectiveness of the proposed method in critical situations such as actuator saturation, unexpected large disturbances, and state-dependent uncertainties.