Modeling and free vibration behavior of rotating composite thin-walled closed-section beams with SMA fibers

Smart structure with active materials embedded in a rotating composite thin-walled beam is a class of typical structure which is using in study of vibration control of helicopter blades and wind turbine blades. The dynamic behavior investigation of these structures has significance in theory and practice. However, so far dynamic study on the above-mentioned structures is limited only the rotating composite beams with piezoelectric actuation. The free vibration of the rotating composite thin-walled beams with shape memory alloy(SMA) fiber actuation is studied. SMA fiber actuators are embedded into the walls of the composite beam. The equations of motion are derived based on Hamilton’s principle and the asymptotically correct constitutive relation of single-cell cross-section accounting for SMA fiber actuation. The partial differential equations of motion are reduced to the ordinary differential equations of motion by using the Galerkin’s method. The formulation for free vibration analysis includes anisotropy, pitch and precone angle, centrifugal force and SMA actuation effect. Numerical results of natural frequency are obtained for two configuration composite beams. It is shown that natural frequencies of the composite thin-walled beam decrease as SMA fiber volume and initial strain increase and the decrease in natural frequency becomes more significant as SMA fiber volume increases. The actuation performance of SMA fibers is found to be closely related to the rotational speeds and ply-angle. In addition, the effect of the pitch angle appears to be more significant for the lower-bending mode ones. Finally, in all cases, the precone angle appears to have marginal effect on free vibration frequencies. The developed model can be capable of describing natural vibration behaviors of rotating composite thin-walled beam with active SMA fiber actuation. The present work extends the previous analysis done for modeling passive rotating composite thin-walled beam.     

Modeling and experiment of a morphing wing integrated with a trailing edge control actuation system

Morphing wing has attracted many research attention and effort in aircraft technology development because of its advantage in lift to draft ratio and flight performance.Morphing wing technology combine...     

形状记忆合金双程弯曲驱动器的设计及试验

为解决变体机翼中蒙皮大变形与承载力之间的矛盾,同时满足光顺性及疲劳寿命的要求,提出了一种以形状记忆合金板为驱动元件的双程弯曲驱动器。基于形状记忆效应及材料力学弯曲理论,通过对驱动器变形过程中的力学特性进行分析,推导出双程弯曲驱动器的设计理论,再利用热成形法与反变形训练法制备出驱动器样件并进行了变形性能测试。研究结果表明：依据推导出的理论所设计的形状记忆合金双程弯曲驱动器的变形量与试验结果一致;随着加热温度的升高,驱动器的挠度及输出力逐渐增大,直至达到最大值;随着回复弹簧钢板厚度的增大,驱动器的最大挠度及最大输出力减小,加热变形响应速度减慢,但冷却回复响应速度加快;经过循环激励后,驱动器的变形效果稳定。     

Genetic algorithm-based hysteresis modeling and identification of rotary SMA actuators

This paper describes a new, modified generalized Preisach model for actuators that have severe dead-zone hysteresis, which is mainly observed in rotary SMA actuators. Along with the Preisach model, a new approach of hysteresis modeling and parameter identification using genetic algorithm was proposed. This modeling method achieved significant improvements in both accuracy and computation time. The proposed approach is general; therefore, it can be applied to identify any type of hysteresis. To demonstrate the efficiency of the proposed model, experimental results on hysteresis identification of Rotary SMA Actuator and performance of inverse hysteresis openloop controller are provided and compared.     

基于两级压力源的液压机快锻节能控制研究

针对传统电液比例阀控快锻液压机系统功率浪费严重的问题,采用四象限负载轨迹分析方法,对其快锻工况下能量分配及流动情况进行研究,得到不同执行器的负载特性,并以满足不同执行器的负载匹配为目标,同时兼顾快锻过程中的能量回收及再利用,提出一种基于两级压力源的新型液压机快锻节能系统。研究两级压力源的参数设计及匹配问题,给出两级压力源构成元件的模型和参数计算方法。采用功率键合图的建模方法,建立快锻液压机系统的数学模型,对两级压力源快锻液压机系统的功率流进行仿真分析;基于0.6 MN液压机试验台,对该快锻系统的控制和节能特性进行试验验证。结果表明,基于两级压力源的新型液压机快锻系统加载时控制精度达到1.5 mm,有用功提高至24.4%。与传统的电液比例阀控系统和采用蓄能器的液压机快锻系统相比,该系统不仅满足了不同执行器的负载匹配需求,而且具有能量存储和再利用的功能,大大降低了装机功率和节流损失,且实现了零溢流。     

Fabrication of 3D soft morphing structure using shape memory alloy (SMA) wire/polymer skeleton composite

The most common method of fabricating a smart structure using a shape memory alloy (SMA) is to create an SMA-embedded structure. However, if the structure is too thick, actuation is decreased significantly. Hence, SMA-embedded structures and robots are usually thin, leaving no space for additional parts. In this research, an SMA-embedded soft morphing structure with large thickness and deformation was developed. A skeletal structure and hinges, which could amplify actuating displacement, were used to increase the overall actuation by maximizing the actuation in a specific area. Also payload of prototype is enough to lift additional weight. A prototype of the design was fabricated via rapid prototyping (RP) and casting. The performance of the prototype was evaluated, and large deformation and actuation force were demonstrated. A cell phone robot was suggested as an application, and the resulting fabricated prototype exhibited crawling actuation.     

Improvement of the performance of hysteresis compensation in SMA actuators by using inverse Preisach model in closed — loop control system

The aim of this paper is to increase the performance of hysteresis compensation for Shape Memory Alloy (SMA) actuators by using inverse Preisach model in closed — loop control system. This is used to reduce hysteresis effects and improve accuracy for the displacement of SMA actuators. Firstly, hysteresis is identified by numerical Preisach model implementation. The geometrical interpretation from first order transition curves is used for hysteresis modeling. Secondly, the inverse Preisach model is formulated and incorporated in closed-loop PID control system in order to obtain desired current-to-displacement relationship with hysteresis reducing. The experimental results for hysteresis compensation by using this method are also shown in this paper.     

混合动力液压挖掘机液压马达能量回收的仿真及试验

针对混合动力挖掘机提出利用液压马达对液压执行元件的回油进行能量回收的节能方案。建立液压挖掘机能量回收的仿真模型,对各执行元件的可回收能量所占比重和系统的节能效果进行仿真计算。搭建混合动力液压马达能量回收试验台,进行能量回收过程中的能量转化效率和操控性能的试验研究。试验和仿真结果表明,在混合动力液压挖掘机系统中采用马达能量回收和发电机转速控制执行元件运动速度的节能方案是可行的。     

车辆CVT液压系统功率匹配控制与仿真

以金属带式无级变速器（V-belt continuously variable transmission，CVT）液压系统为研究对象，建立了系统压力、流量和功率特性的仿真模型；对车辆行驶循环下的CVT功率特性进行了仿真和功率匹配分析，提出了减小液压系统功率损失、实现系统功率匹配的方案；进行了双联泵供油的CVT液压系统功率匹配控制的方案设计、动态建模和仿真分析。计算表明，采用的双联泵功率匹配系统能有效提高CVT液压系统效率。研究结果为CVT液压系统的节能控制提供了理论依据。     

核电用高温合金Inconel 617B高温变形本构模型

传统的Arrhenius本构模型因对流变应力的预测精度较低而存在局限性。通过应变量补偿构建高温合金Inconel 617B的唯象型本构模型,同时构建合金的BP人工神经网络（Back propagation-artificial neural network,BP-ANN）型本构模型。结果表明：合金的流变应力对变形温度、变形速率和应变量较为敏感。唯象型本构模型预测流变应力的相对误差δ为9.020%,相关系数R为0.981 4;而BP-ANN型本构模型（最佳结构确定为3×20×1）预测结果的相对误差仅为1.527%,R达到0.998 9,可更加准确地预测Inconel 617B的流变应力。说明BP-ANN构建本构模型可提高预测精度,更为合理地描述Inconel 617B高温合金的流变应力与变形参数间的本构关系。     

风能驱动抽油机节能技术研究

我国油田风资源丰富,合理地利用风资源可实现油田节能。在分析了油田风能利用现状后,找出了目前采用风力发电供能模式存在的一些问题,并针对这些问题,提出了全新的风能利用方法:通过风机液压传动技术与机械-液压混合动力技术的有机结合,可以实现高效利用风能和节约电能。依据系统结构建立了数学模型,并通过Matlab/Simulink仿真软件与Amesim仿真软件建立了系统的整体仿真模型;提出了该系统的参数设计方法;通过联合仿真研究,对比不同参数组合下的系统效率和节能特性,提出系统在压力区间10~15 MPa内工作时,风机-泵系统与机械-液压混合动力系统可同时达到最佳效率,节电率最大达到62%。     

记忆合金柔性机械手研究

介绍了一种新型SMA驱动器 ,从理论和实验上研究了驱动器的弯曲变形原理。通过开环实验 ,得到了SMA驱动器的控制模型 ,并对驱动器P+控制进行了实验研究。最后 ,利用多驱动器的组合制作了一柔性机械手演示装置 ,实验证明 ,该手爪能完成快速柔顺的抓取动作     

SMA驱动变体机翼后缘精确控制研究

对基于形状记忆合金(SMA)驱动器的变体机翼后缘结构进行了设计分析与精确控制研究。经过详细准确的计算分析,确定了SMA的规格和布局方案,然后在CATIA软件中建立实体模型并通过数控加工得到变体机翼后缘模型;设计了基于数字信号处理(DSP)的测控系统,采用分段控制和PID控制相结合的控制策略,分别对变体机翼后缘第三旋转关节结构和整体结构的偏转进行了精确控制实验,结果表明偏转角度最大误差小于4%,响应时间小于6.7 s,初步实现了变体后缘偏转的精确控制。     

超大型液压挖掘机闭式回转系统惯量分析

超大型液压挖掘机应用日趋广泛,其回转系统具有时变超大惯量特性,对装载效率、节能性和操控性产生重大影响。建立了300 t超大型液压挖掘机闭式回转系统的AMESim ADMAS 联合仿真模型,研究了一个回转循环中工作装置的位置变化对回转惯量的影响,获得了回转惯量呈“U”形的变化规律,并揭示了回转惯量对回转系统压力响应的影响,为超大型液压挖掘机闭式回转系统的设计与控制提供了理论依据。     

A simple smart wing actuator using Ni-Ti SMA

One way shape memory effect (SME) is not sufficient in the application of the automatic repeated actuation of the SMA wire because the actuator using SME cannot return to its initial shape after it cools down. In the present study, the two-way SME under residual stress is considered. An actuator using the two-way effect of SMA returns to its initial shape by increasing or decreasing the temperature of SMA under initial residual stress. Using the two-way effect, we manufactured a simple smart wing actuator which consists of the SMA wire and a torsional spring to induce variable residual stresses. The SMA wire after the specific training procedure in order for the actuator to be used for the repeated actuations without performance deteriorations in the specified actuation requirements was used. The simple smart wing actuator has been tested for repeated actuations in still-air as an environmental thermal condition for the practical aspect of its usage. The characteristics of actuator behavior according to operation thermal cycle duration time, i.e., the response characteristics for rapid actuation were investigated. By the application of the simple smart wing actuator using the SMA wire, SMA shows novel performance in repeated actuations.     

[绿色设计]面向2020年的质子交换膜燃料电池汽车生命周期评价及预测

运用GaBi软件建模，以我国燃料电池技术2020年发展目标为基础，结合美国能源部2020年燃料电池汽车技术计划，对2020年我国燃料电池汽车的全生命周期节能减排绩效进行定量评价计算和预测分析。结果表明：2020年我国每台燃料电池汽车全生命周期平均矿产资源消耗量EADP(e)、化石能源消耗量FADP(f)和温室气体排放量QGWP分别为0.609 kg（锑当量）、3.99×105 MJ以及2.99×104 kg（CO2当量）。从其全生命周期来看，EADP(e)、FADP(f)与原材料获取阶段贵金属铂的生产、制氢技术以及燃料电池的效率有关，QGWP则主要来源于制氢过程中消耗的化石燃料和电能。降低燃料电池汽车对资源环境影响的有效措施有：加快研发关键材料及金属铂的高效回收策略，从而不断降低贵金属的消耗量；改进制氢技术，由化石能源主导变为可再生清洁能源主导；逐步优化电力结构，有效降低氢气压缩过程中的煤电消耗量等。     

面向结构形状控制的压电纤维复合薄膜驱动器布局方式与控制参数协同优化设计

能够根据工作环境改变翼面形状的自适应变形能力是未来航空、航天飞行器结构设计追求的重要目标。研究驱动器布局方式以及控制参数的设计技术是实现该目标的关键。以压电纤维复合薄膜(Macro fiber composites,MFC)作为驱动器,研究在一定数量的MFC驱动器条件下,通过驱动器布局与控制参数的协同设计,以实现类翼面平板结构具有理想形状的最优控制设计方法。以驱动器的铺设位置、铺设角度、层数、对称性以及控制电压为设计变量,以驱动器的击穿电压、铺设位置限制等为约束,建立多参数下的协同优化设计模型。数值算例以类机翼平板的弯曲、扭转、弯扭型面作为理想型面,以实际型面与理想型面在81个参考点位置的均方差为评价指标,设计获得弯曲、扭转和弯扭组合型面的均方差分别为9.977×10–5、4.394×10–4和5.308×10–4,实现了较高的变形控制精度。研究了驱动器数量对变形精度的影响,制作了具有6个驱动器的类翼面平板结构测试平台,仿真与试验结果高度吻合,从而验证了所提出的驱动器布局与控制电压协同优化设计模型的有效性和可行性。     

Numerical analyses of the coupled-dynamic behavior of droplets on a vibrating membrane with a microsphere array at a three-phase interface

Analyses of the dynamic behavior of droplets are significant for a broad range of industrial applications. However, previous works have primarily studied the dynamic behavior on solid flat plates. Therefore, they could consider both the effect of geometric structure and energy simultaneously. In order to analyze the coupled-dynamic behavior of droplets, SMA membranes with microsphere arrays were used to apply the effects of both geometry and energy to droplet surfaces. The shape of the droplet changed harmonically with time during actuation. In the simulation, 50 and 200 Hz excitations related to the first and second droplet frequencies, respectively were used in order to investigate the coupled-behavior of the droplet. COMSOL Multiphasics™ was used to numerically analyze the dynamic behavior of droplets. The simulation results showed that the dynamic behavior of the water droplet was strongly affected by the natural frequency, and the interface and behavior were determined by both the mode shape and vibrating energy. As the actuation frequency increased, the energy equilibrium changed at the interface and occasionally broke. And then, the contact line on the actuated surface was changed to create new stable state.     

Structural design of morphing trailing edge actuated by SMA

In this paper, the morphing trailing edge is designed to achieve the up and down deflection under the aerodynamic load. After a detailed and accurate computational analysis to determine the SMA specifications and layout programs, a solid model is created in CATIA and the structures of the morphing wing trailing edge are produced by CNC machining. A set of DSP measurement and control system is designed to accomplish the controlling experiment of the morphing wing trailing edge. At last, via the force analysis, the trailing edge is fabricated with four sections of aluminum alloy, and the arrangement scheme of SMA wires is determined. Experiment of precise control integral has been performed to survey the control effect. The experiment consists of deflection angle tests of the third joint and the integral structure. Primarily, the ultimate deflection angle is tested in these two experiments. Therefore, the controlling experiment of different angles could be performed within this range. The results show that the deflection error is less than 4% and response time is less than 6.7 s, the precise controlling of the morphing trailing edge is preliminary realized.     

基于AMESim的地铁车辆空气制动系统的建模及仿真

介绍了地铁车辆空气制动系统的结构,分析该系统的制动风路,利用工程系统仿真软件AMESim对地铁车辆空气制动系统的各主要组成部分:EP阀、中继阀、防滑阀分别进行建模,再对整个系统进行建模并仿真。通过该系统模型的建立及仿真可知,利用AMESim中的气动库能对车辆空气制动系统的研究提供一种方法。