Simulation, experimental evaluation and performance improvement of a cone dielectric elastomer actuator

Dielectric elastomer actuators （DEAs） are an emerging class of polymer actuation devices and have extensive application prospect in the field of robotics because of their light weight, high efficiency and large deformation. A cone DEA is manufactured and its working principle is analyzed. To obtain the deformation of elastomer and movement of DEA in advance, a finite element method （FEM） simulation is performed first. According to the working principle, two working equilibrium points of DEA, corresponding to the displacements of DEA with voltage off and on, are obtained and validated by experiments, thus work output in a workcycle is computed. Experiments show that the actuator can respond quickly when voltage is applied and can return to its original position rapidly when voltage is released. Simulation results agree well with experimental ones and the feasibility of DEA simulation is proved, and causes for the small difference between them in displacement output are analyzed. The performance of the actuator is improved from the aspects of both displacement and force output. A diamond four-bar linkage mechanism is used as the preload part and a displacement output of 17 mm is obtained. The force output of one actuating unit is about 1.77 N, so three actuating units are assembled in parallel and the force output is heightened to as high as 5.07 N.     

Distribution of extracellular polymeric substances in pilot-scale membrane bioreactor

The spatial distribution of extracellular polymeric substances （EPS） in a pilot-scale membrane bioreactor （MBR） was studied. The sampling points on top of and inside the membrane module were measured and analyzed by the experimental variant function. The content of EPS was spatially interpolated by ordinary Kriging method, and il- lustrated with SURFER software. A case study was carried out in an MBR with membrane aperture of 0.4 ~tm and handling capacity of 120 ma/d in Jizhuangzi sewage treatment plant, Tianjin. From the visualization of EPS distribu- tion, it is seen that on the horizontal plane, the content of EPS was the lowest at the center; and on the vertical plane, the content of EPS decreased with the increase of depth. The shearing force caused by aeration of perforated pipe and the influent mode are the main influencing factors for this distribution.     

Development of a non-cable whole tectorial membrane micro-robot for an endoscope

A novel non-cable whole tectorial membrane micro-robot for an endoscope is developed. The micro-robot we have fabricated and tested can propel itself in the intestine tract of a pig in an autonomous manner by earthworm-like locomotion. The silicone of bellow shape is laid over the outer surface of the micro-robot to reduce the affection of the viscoelastic properties of the intestine. Wireless power transfer and communication systems are employed to realize the non-cable locomotion of the micro-robot. The prototype of the micro-robot is 13.5 mm in diameter and 108 mm in length. The experimental results show that the towing force for the micro-robot is about 0.8 N, which is much smaller than the maximum driving force 2.55 N of the linear actuator. The supplying power of the wireless power transfer system fulfills the needs of the micro-robot system and the micro-robot can creep reliably in the large intestine of a pig and other contact environments.     

Interactions between mycoplasma lipid-associated membrane proteins and the host cells

Mycoplamas are a group of wall-less prokaryotes widely distributed in nature, some of which are pathogenic for humans and animals. There are many lipoproteins anchored on the outer face of the plasma membrane, called lipid-associated membrane proteins （LAMPs）. LAMPs are highly antigenic and could undergo phase and size variation, and are recognized by the innate immune system through Toll-like receptors （TLR） 2 and 6, LAMPs can modulate the immune system, and could induce immune cells apoptosis or death. In addition, they may associate with malignant transformation of host cells and are also considered to be cofactors in the progression of AIDS.     

用于电力系统故障电流限制器的快速合闸开关研究

This paper presents a new type of fault current limiter(FCL) based on fast-closing switch,which is composed of a capacitor bank and a reactor in series.The main control component is a fast-closing switch connected in parallel with the capactitors,which is drien by the electromagnetic repulsion force.It can response the order within 1 ms.When fault occurs,the switch closes and the capacitors are bypassed.and the fault current is limited by the reactor,Simulation analysis and experiment show that the electromagnetic repulsion force actuator can meet the demand of fast-closing switch,it is feasible to develop the FCL with low cost and high reliability.     

Hierarchical models for failure analysis of plates bent by distributed and localized transverse loadings

The failure analysis of simply supported, isotropic, square plates is addressed. Attention focuses on minimum failure load amplitudes and failure locations, von Mises＇ equivalent stress along the plate thickness is also addressed. Several distributed and localized loading conditions are considered. Loads act on the top of the plate. Bi-sinusoidal and uniform loads are taken into account for distributed loadings, while stepwise constant centric and off-centric loadings are addressed in the case of localized loadings. Analysis is performed considering plates whose length-to-thickness ratio a/h can be as high as 100 （thin plates） and as low as 2 （very thick plates）. Results are obtained via several 2D plate models. Classical theories （CTs） and higher order models are applied. Those theories are based on polynomial approximation of the displacement field. Among the higher order theories （HOTs） HOTsa models account for the transverse shear deformations, while HOTs models account for both transverse shear and transverse normal deformations. LHOTs represent a local application of the higher order theories. A layerwise approach is thus assumed： by means of mathematical interfaces, the plate is considered to be made of several fictitious layers. The exact 3D solution is presented in order to determine the accuracy of the results obtained via the 2D models. In this way a hierarchy among the 2D theories is established. CTs provide highly accurate results for a/h greater than 10 in the case of distributed loadings and greater than 20 for localized loadings. Results obtained via HOTs are highly accurate in the case of very thick plates for bi-sinusoidal and centric loadings. In the case of uniform and off-centric loadings a high gradient is present in the neighborhood of the plate top. In those cases, LHOTs yield results that match the exact solution.     

Research on electromagnetic relay＇s dynamic characteristics disturbed by uniform static magnetic field

Electromagnetic relay is a widely used apparatus which usually works in a magnetic disturbance environment. To evaluate its electromagnetic compatibility （EMC） in a static magnetic field, dynamic characteristics of a clapper relay in a uniform static magnetic field situation based on the finite element method （FEM） is studied. Influences of the magnetic field on dynamic parameters （delay time, pick-up time, end pressure, and final velocity） as well as a situation in which the relay cannot function normally are analyzed. Simulation reveals that the external magnetic field which weakens the relay＇s air-gap field has a greater influence on the relay＇s dynamic parameters than the one strengthening the field. The validity of the simulation is verified by measured results of coil current and armature displacement.     

Focusing with the decomposition of the time reversal operator method in noisy environments

This paper presents a detailed analysis of the effects of noise （reverberation） on the focusing performance of decomposition of the time reversal operator （DORT） in a noise-limited case and in a reverberation-limited case, respectively. Quantitative results obtained from simulations and experiments are presented. The results show the DORT method can be efficiently applied to target detection with enough source level to yield significant backscatter. For a target placed on the bottom, the influence of the reverberation on the focusing performance is slight. However, distinguishing between a target and constant backscattering returning from strong local clutter on the bottom （false alarms） needs further research.     

Atmospheric corrosion mapping of copper surfaces from diffuse light scattering measurements by an optoelectronic sensor system

A novel light scattering technique for mapping metal surface corrosion is presented and its results on copper exposed to atmosphere are reported. The front end of the instrument is made up of a sensor module comprising a thin beam light emitting diode （LED） illuminating a small spot on the metal surface, and a matched pair of photodetectors, one for capturing the reflected light and the other for sampling the scattered light. The analog photocurrent signals are digitized and processed online by a per- sonal computer （PC） to determine the corrosion factor defined in terms of the two current values. By scanning the sample surface using the light beam and by computing the corrosion factor values simultaneously, a three dimensional graph and a two dimensional contour map are generated in the PC using Matlab tools. The values of the corrosion factor measured in different durations of exposure to atmosphere, which obey a bilogarithmic law, testify to the validity of our mathematical model.     

Genetic algorithm for scheduling reentrant jobs on parallel machines with a remote server

This paper considers a reentrant scheduling problem on parallel primary machines with a remote server machine, which is required to carry out the setup operation. In this problem, each job has three operations. The first and last operations are performed by the same primary machine, implying the reentrance, and the second operation is processed on the single server machine. The order of jobs is predetermined in our context. The challenge is to assign jobs to the primary machines to minimize the makespan. We develop a genetic algorithm（GA） to solve this problem. Based on a simple strategy of assigning jobs in batches on the parallel primary machines, the standardized random key vector representation is employed to split the jobs into batches. Comparisons among the proposed algorithm, the branch and bound（BB） algorithm and the heuristic algorithm, coordinated scheduling（CS）, which is only one heuristic algorithm to solve this problem in the literature, are made on the benchmark data. The computational experiments show that the proposed genetic algorithm outperforms the heuristic CS and the maximum relative improvement rate in the makespan is 1.66%.     

Simulation and experimental evaluation of a combustion-powered actuator for hopping

A combustion-powered actuator has been proposed in our previous work (Wang et al., 2015), and it has shown great power hopping ability. To explore the hopping process and output performance of the actuator, the model of an actuator driving the hopping process is investigated through theoretical analysis and experimental validation. Firstly, the structure of the actuator and hopping process are described briefly, and the dynamic models of the process are constructed. Secondly, the thermodynamic model of the actuator is established by the Wiebe heat release function and the input energy density is computed by Chemkin for when propane and nitrous oxide with different equivalence ratios are injected into the chamber. Thus, the thermodynamic model is obtained by integrating dynamic and thermodynamic equations. After that, a few output performance parameters are identified to assess system performance. Lastly, the experimental rig of the combustion actuator is set up to test the displacement and pressure of the actuator driven hopping process. By solving the thermodynamic equations, the post-combustion pressure, the displacement and the velocity varying with time are computed, and are compared with the test results, indicating that the computational results match the experimental test well. At the end of the stroke, the velocities of the experiment and simulation are 6.5 m/s and 6.99 m/s, respectively. The hopping results are compared with the simulation when different pressures under equivalence ratio of 1 are injected, and the maximum and minimum deviations are 14.45% and 1.83%, respectively.     

复合舵机直线加载实验台设计和实验

设计了复合舵机直线加载实验台,包括油源、油源控制器、舵机控制器、复合舵机、加载舵机、加载惯量盘以及支撑台体等。油源控制器采用AVR128单片机作为核心控制芯片,控制系统软件使用NI LabWin-dows/CVI和Microsoft Windows操作系统的实时扩展RTX实现实时控制。加载通道的齿轮齿条惯量盘可以模拟飞机舵面的转动惯量,并且可以使用配重块调节转动惯量。该实验台既可以作为复合舵机设计、性能评价的半实物仿真平台,也可以用于本科生、硕士研究生相关课程的实验。     

Review：Recent advances in nonlinear control technologies for shape memory alloy actuators

This paper reviews recent developments in nonlinear control technologies for shape memory alloy (SMA) actuators in robotics and their related applications. SMA possesses large hysteresis, low bandwidth, slow response, and non-linear behavior, which make them difficult to control. The fast response of the SMA actuator mostly depends upon, (1) type of controller, (2) rate of addition and removal of heat, and (3) shape or form of the actuator. Though linear controllers are more desirable than nonlinear ones, the review of literature shows that the results obtained using nonlinear controllers were far better than the former one. Therefore, more emphasis is made on the nonlinear control technologies taking into account the intelligent controllers. Various forms of SMA actuator along with different heating and cooling methods are presented in this review, followed by the nonlinear control methods and the control problems encountered by the researchers.     

Development of an ε-type actuator for enhancing high-speed electro-pneumatic ejector valve performance

A novel ε-type solenoid actuator is proposed to improve the dynamic response of electro-pneumatic ejector valves by reducing moving mass weight. A finite element analysis （FEA） model has been developed to describe the static and dynamic operations of the valves. Compared with a conventional E-type actuator, the proposed ε-type actuator reduced the moving mass weight by almost 65% without significant loss of solenoid force, and reduced the response time （RT） typically by 20%. Prototype valves were designed and fabricated based on the proposed ε-type actuator model. An experimental setup was also established to investigate the dynamic characteristics of valves. The experimental results of the dynamics of valves agreed well with simulations, indicating the validity of the FEA model.     

轮式微型机器人运动机理与步态规划

在一种新型形状记忆合金驱动器的基础上,研制了一种微型蠕动机器人,该机器人采用轮式移动机构.对形状记忆合金驱动器、轮式移动机构的结构和运动机理以及机器人的步距扩大原理进行了讨论.并在此基础上,对机器人的直线运动步态和转弯步态进行了规划,使机器人在偏心轮自锁机构和换向机构作用下,不但可以前后运动,还具有主动转弯能力,在一定程度上克服了传统的形状记忆合金机器人移动速度慢、只能被动转弯的缺点.最后对形状记忆合金驱动器所需加热电流及该机器人的运动性能进行了试验分析.     

Dynamics of installation way for the actuator of a two-stage active vibration-isolator

We investigated the behaviors of an active control system of two-stage vibration isolation with the actuator installed in parallel with either the upper passive mount or the lower passive isolation mount. We revealed the relationships between the active control force of the actuator and the parameters of the passive isolators by studying the dynamics of two-stage active vibration isolation for the actuator at the foregoing two positions in turn. With the actuator installed beside the upper mount, a small active force can achieve a very good isolating effect when the frequency of the stimulating force is much larger than the natural frequency of the upper mount; a larger active force is required in the low-frequency domain; and the active force equals the stimulating force when the upper mount works within the resonance region, suggesting an approach to reducing wobble and ensuring desirable installation accuracy by increasing the upper-mount stiffness. In either the low or the high frequency region far away from the resonance region, the active force is smaller when the actuator is beside the lower mount than beside the upper mount.     

双稳态电磁型微驱动器的研制

1 Introduction Microactuators are the key devices of micro-electro-mechanical system( MEMS) . For many MEMS devicessuch as switches , optical attenuators , pumps andvalves to function, microactuators are required . Mo-tion of microactuators can be achieved by several kindsof actuation mechanisms . Electrostatic ,piezoelectric ,magnetostrictive, magnetic ,thermomechanical actua-tors have been reported[1-5].Among the different actu-ation principles ,the electrostatic actuationis predomi-nant…     

Piezo微步进执行器的时间响应分析

提出了一种新型二维超精密微步进工作台的结构形式,并针对该结构设计了相应的微步进执行器.以新型功能材料Piezo作为驱动元件,分析了微步进执行器的机电耦合模型,在此基础上对其时间响应进行了分析,总结了时间响应的影响因素,同时提出了相应的解决方法.     

中耳植入式助听装置压电悬浮振子的电压特性分析(英文)

针对一种新型悬浮振子式中耳植入助听装置, 分析了其振子的驱动电压特性, 该振子由0.7Pb(Mg1/3Nb2/3)O3-0.3PbTiO3(PMN-30%)叠堆实现. 为了辅助分析, 建立了听骨链与振子的简化耦合力学模型. 首先利用逆向成型技术建立了人体中耳有限元模型, 其可靠性通过镫骨底板的位移模拟值与实验测得数据对比得以验证; 然后利用该中耳有限元模型分析了振子绑定装置处的位移阻抗特性, 并基于此建立听骨链与绑定装置的等效力学模型; 最后建立了听骨链与压电悬浮振子的耦合力学模型, 分析了该振子的驱动电压特性. 研究结果表明:振子所需驱动电压随着频率的增大而减小; 在语音频段, 所需的最大驱动电压为20.9 V; 在感音神经性听力损伤多发生的中高频段, 该驱动电压不高于3.8 V, 满足中耳植入式助听装置低电压、低能耗的要求.     

场诱发相变驱动材料研究

从驱动组元的工作机理角度,系统分析了目前可用于智能材料系统中的驱动材料,提出了场诱发相变驱动材料的设计思想,对场诱发相变的铁电体和反铁电体材料进行优化设计和制造,结果表明:研制场诱发相变的理想驱动材料是可能的。