Robots with increased number of degree-of-freedom with single exciting force

This paper presents the results of the development and investigation of a new class of novel multi-degree-of-freedom robots based on a new concept – the application of kinematic pairs with alternating degree-of-freedom (DOF) controlled by a single force or moment, changing its direction in space. The number of DOF of the kinematic pairs is controlled periodically from 0 to 3, exploiting the dependence of frictional forces on the oscillation in the contact zone of links. The advantages of this new class of robots include significant weight reduction, simple design and control, and specific applications in space robotics and soft robotic spines. In more complicated cases of trunk robots, elastic kinematic pairs are used with a number of DOF controlled by electro- or magneto-rheological fluids with viscosities that change as a result of applied electric or magnetic fields. Expressions for the generalized inertia matrix of the robots with a large number of joints have been derived using the computer algebra technique with the subsequent automatic program code generation. As shown in this paper, such an application could drastically reduce the number of floating point product operations for an efficient numerical simulation of robots.     

Analysis of magnetorheological fluid behavior in chemo-mechanical magnetorheological finishing (CMMRF) process

Advanced nanofinishing is an important process in manufacturing technologies due to its direct influence on optical quality, bearing performance, corrosion resistivity, bio-medical compatibility and micro-fluidics attributes. Chemo-mechanical magnetorheological finishing (CMMRF) process, one of the advanced nanofinishing process, was developed by combining essential aspects of chemo-mechanical polishing (CMP) process and magnetorheological finishing (MRF) process for surface finishing of engineering materials. The CMMRF process was experimentally analyzed on silicon and copper alloy to generate surface roughness of the order of few angstroms and few nanometers respectively. However, the process needs theoretical exploration towards better understanding, process optimization and result prediction. Hence, an attempt has been made for theoretical study of CMMRF process to analyze the effects of MR fluid under various process parameters. The present theoretical work is split as per following two sub-activities to simplify intricacy of the work.1) FEA-CFD simulation to analyze magnetism, polishing pad formation and polishing pressure during the CMMRF process. The simulation results are used to conduct experiments on aluminium alloy.2) A mathematical model has been developed to predict material removal as well as surface roughness during the CMMRF process. Model validation is conducted by comparing finite element simulation results with the experiments on aluminium alloy.The theoretical results show good agreement with the experimental data and the same has been discussed in this paper.     

基于Pareto集和Bingham模型的磁流变减振器多目标优化与试验验证

磁流变减振器和半主动悬架可以同时兼顾车辆操纵稳定性和行驶安全性,是目前汽车电子技术的研究热点。磁流变减振器的设计大多只考虑某一优化目标,基于Pareto集多目标方法和带精英策略的非支配排序遗传算法(the elitist Nondominated Sorting Genetic Algorithm,NSGA-Ⅱ),以阻尼力和动力可调系数为优化目标,设定7个优化变量,构建了车用磁流变减振器多目标优化模型与实现算法。分析了7个优化变量对阻尼力和动力可调系数的设计敏感性,并通过有限元分析和试验验证优化解的可靠性。研究发现:阻尼通道间隙对优化目标影响最大,最大阻尼力和最大动力可调系数呈负相关关系。该多目标优化计算的最优解满足实际工程需求,证明了提出的优化方法快速有效,为磁流变减振器的设计提供了可靠的工具。     

磁流变液屈服应力测试仪磁路设计与仿真

分析了平行圆盘式磁流变液屈服应力测试仪的工作原理,结合磁路欧姆定律和安培环路定理,对一种圆盘式磁流变液屈服应力测试装置的磁路进行计算,确定励磁线圈的相关参数。在此基础上,运用有限元软件Ansys中的磁场分析单元对磁路进行建模和仿真。仿真结果表明,工作区间的磁场为匀强磁场,磁场强度随励磁电流的增大而增大。     

磁流变耦合轮对车辆高速曲线通过性能研究和探讨

为使磁流变耦合轮对车辆向高速铁路的工程化有较大的进展,建立31自由度的车辆系统数学模型。仿真计算表明：磁流变屈服应力小于某一值和曲线半径小于一定值时,对轮对的横移、摇头、轮轨横向力和车体横向加速度造成的波动较大,有的可能会出现两点接触;屈服应力在随后的一定范围内,车辆在不同半径曲线上的以上性能参数变化平缓且较小;继续增大屈服应力,以上性能参数则增加。因此,当磁流变的屈服应力在一定范围内变化时,磁流变耦合轮对车辆才具有较好的高速曲线通过性能。     

正弦曲面磁流变抛光的收敛比与斑参数的关系研究

以二维正弦曲面为加工对象,采用反转变换的加工方法,研究了磁流变抛光斑的长度、宽度以及峰值去除率等参数对周期面形收敛能力的影响.仿真结果显示,当抛光斑的宽度小于空间周期一半时,收敛比大于2,获得较好的加工效果.     

双筒单出杆式磁流变阻尼器力学特性研究

介绍了一种基于流动模式的双筒单出杆式磁流变阻尼器结构和工作原理,推导了其阻尼力公式。对基于上述结构的MRF阻尼器的阻尼力、电流、位移、速度和频率等力学特性进行了试验研究。结果表明流动模式磁流变阻尼器的阻尼力随控制电流的增大呈非线性增加,其耗能减振能力优于传统的被动阻尼器。气囊导致压缩行程终点阻尼力放大,并可以在一定程度上消除复原行程的空程现象。而阻尼器的结构尺寸和所选用的磁流变液一旦确定,其可调倍数只依赖于最优的磁路设计。通过深入分析该型阻尼器的动力特性,为改进研制装甲车辆磁流变减振器奠定了基础。     

Analytical study on damping performances of magnetorheological grease damper based on disk squeeze mode and experimental test

In this paper, a small displacement-type magnetorheological grease (MRG) damper based on disk squeeze mode is proposed. The squeeze flow differential equation is obtained. The Navier slip condition is considered on the surfaces and the boundary compatible condition is established. The radial velocity profiles and the radial pressure distributions are derived respectively, and the mathematical stress expression is calculated. To verify rationality of analytical method, the MRG damper is designed and fabricated according to the technical requirements of an engine vibration isolation system. The experimental damping force from MTS870 Electro-hydraulic Servo with sine wave excitation shows that the proposed analytical method is feasible and provides the reference value for designing MRG damper based on disk squeeze mode.     

磁流变抛光对熔石英激光损伤特性的影响

为进一步提升熔石英元件的激光损伤阈值,研究了氢氟酸(HF)动态酸刻蚀条件下磁流变抛光工艺对熔石英元件激光损伤特性的影响规律。首先,采用不同工艺制备熔石英元件,测量它们的表面粗糙度。然后,采用飞行时间-二次离子质谱法(OF-SIMS)检测磁流变加工前后熔石英元件中金属杂质元素的含量和深度;采用1-on-1方法测试激光损伤阈值,观测损伤形貌,并对损伤坑的形态进行统计。最后,分析了磁流变抛光工艺提升熔石英损伤阈值的原因。与未经磁流变处理的熔石英元件进行了对比,结果显示:磁流变抛光使熔石英元件的零概率激光损伤阈值提升了23.3%,金属杂质元素含量也显著降低,尤其是对熔石英激光损伤特性有重要影响的Ce元素被完全消除。得到的结果表明,磁流变抛光工艺能够被用作HF酸动态酸刻蚀的前道处理工艺。     

增加车辆刹车可控性设计

防抱死制动系统(Antilock braking system,ABS)是通过车轮角加速度与阈限值的比较进行制动力控制.这种系统的优势是只需角速度传感器信号就足够了;缺点是工作时会出现制动压力连续的超调,使车轮从抱死模式到滚动模式来回转换,这样制动器不能产生在当前道路状况下最大可能的制动力矩值.增加制动效率的构思是制动压力增加的强度取决于当前道路状况,但面临的问题是制动器产生的制动力矩值、当前道路状况和牵引系数值是未知数.本文通过建立三层神经网络模型来识别和获取这些参数,并在设计的随机路面上进行仿真实验,验证了所设计控制器工作的准确性.     

磁流变阻尼器的设计和性能分析

提出一种基于磁流变液体(Magnetorheologicalfluid)阻尼器,该阻尼器采用阻尼缸和阻尼阀并联的结构形式,其长度不受系统气缸行程的限制。其中阻尼阀采用双线圈磁路设计,可有效地减少导磁轴的横截面积,改善漏磁。该阻尼器具有体积小,结构紧凑的特点。介绍了该阻尼器的结构和工作原理、阻尼阀的结构设计方法,并通过性能测试实验,分析阻尼器的性能。实验结果表明该阻尼器的性能良好,可用气动伺服系统,实现系统较高精度的精确定位,配合实时控制系统,可提高系统的稳定性、精确性、可靠性和快速响应性。     

Water based cutting fluids and human health

The question of whether machining operations and exposure to water-base cutting fluids constitutes a human health problem is complex. The literature on the subject is hard to find; it is difficult to create study groups of workers large enough to develop statistically significant information; there is often a lag phase of several years between exposure to cutting fluids and the appearance of a medical problem; public attitudes restrain research on the subject; the identity of the chemicals involved is not completely known and animal studies involving cutting fluids are not adequate at present. Until adequate information is available, efforts should be directed towards minimizing exposure and controlling the microbial loads found in these products.     

Creep and recovery behaviors of magnetorheological elastomers

This paper presents experimental and modeling study of creep and recovery behaviors of magneto-rheological elastomers (MREs) under constant stresses. Experimental study was accomplished using a rheometer with parallel-plate geometry. Under constant stresses ranging from a small value to a large one, the resultant strains were recorded. The experimental results demonstrated that MREs behave as linear visocleastic properties. The effects of the magnetic field and stress on MRE creep behaviors were discussed. Moreover, a four-parameter viscoelastic model was developed to describe MRE creep behaviors. The comparison between the experimental results and the modeling predictions indicates that the model can predict MRE creep behaviors very well.     

基于磁流变阻尼器的半主动悬架控制与仿真

基于磁流变阻尼器的Bouc-Wen模型,设计了半主动悬架系统的控制器.该控制器由系统控制器和阻尼器控制器组成,系统控制器采用二次型最优控制LQR算法,阻尼器控制器采用基于Signum函数的方法.进行了基于Simulink的仿真分析,通过比较被动控制和主动控制,表明该半主动控制算法具有良好的控制效果.     

雾状油膜水滴冷却润滑车削试验研究

油膜水滴是使用冷空气、微量可自然降解油剂和少量水,经复合喷雾法形成可自然分解的、新型绿色切削液.与传统切削液相比,油膜水滴在保护环境,节省资源等方面有很大的优势.通过车削试验,比较和分析不同冷却润滑条件下刀具磨损和已加工表面质量,揭示出雾状油膜水滴绿色切削液的优越性.     

车辆单筒充气磁流变减振器的阻尼力数学模型及试验仿真

介绍一种车辆单筒充气磁流变减振器的结构和工作原理,其内部的磁流变液材料是一种新型的智能材料,其流变特性可随所加载磁场强度的变化而变化,并且这一过程是可逆的,用磁流变液制成的减振器具有体积小、阻尼力大、动态范围广和频响高等优点。研究利用磁流变液的非牛顿宾汉流体模型和流体运动微分方程,建立反映单筒充气磁流变减振器阻尼力特性的数学模型;对单筒充气磁流变减振器进行台架试验,得到不同电流的减振器示功特性图;通过试验测得磁流变减振器的仿真参数,然后在Matlab软件环境下完成阻尼力数学模型的仿真;试验的示功特性与数学模型仿真进行分析比较,结果表明仿真数据与试验数据较吻合,验证了建立的单筒充气阻尼力数学模型的正确性。     

圆盘式MRF离合器的研究

磁流变液离合器是一种利用磁流变液剪切应力来进行离合的一种装置，它传递的力矩随外加磁场的变化迅速变化。本文在理论上给出了盘式磁流变液离合器的设计方法，推出了磁流变液离合器传递力矩的方程，得出了盘式磁流变液离合器中磁流变液体积、厚度等的计算公式。为盘式磁流变液离合器的设计奠定了理论基础。     

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.     

基于自抗扰控制器的无刷直流电机调速系统的建模与仿真

在分析自抗扰控制器和无刷直流电机数学模型的基础上，基于simulink软件建立了无刷直流电机控制系统的仿真模型。采用单环调速系统进行仿真。仿真结果证明了该方法的有效性．为实际电机控制系统的设计提供了新的思路。     

基于simulink磁流变液制动器性能仿真与分析

介绍了磁流变液的组成和性能,阐述了磁流变液制动器的结构和原理。根据磁流变液的流变特性,推导了单盘式圆盘型磁流变液制动器和圆筒型磁流变液制动器的制动力矩公式,并在Simulink环境内建立了单盘式圆盘型磁流变液制动器和圆筒型磁流变液制动器模型,分析了2种磁流变液制动器的性能特点。分析结果可为磁流变液制动器的理论研究和设计提供参考。