Dynamic model and performance analysis of landing buffer for bionic locust mechanism

The landing buffer is an important problem in the research on bionic locust jumping robots, and the different modes of landing and buffering can affect the dynamic performance of the buffering process significantly. Based on an experimental observation, the different modes of landing and buffering are determined, which include the different numbers of landing legs and different motion modes of legs in the buffering process. Then a bionic locust mechanism is established, and the springs are used to replace the leg muscles to achieve a buffering effect. To reveal the dynamic performance in the buffering process of the bionic locust mechanism, a dynamic model is established with different modes of landing and buffering. In particular, to analyze the buffering process conveniently, an equivalent vibration dynamic model of the bionic locust mechanism is proposed.Given the support forces of the ground to the leg links, which can be obtained from the dynamic model, the spring forces of the legs and the impact resistance of each leg are the important parameters affecting buffering performance, and evaluation principles for buffering performance are proposed according to the aforementioned parameters. Based on the dynamic model and these evaluation principles, the buffering performances are analyzed and compared in different modes of landing and buffering on a horizontal plane and an inclined plane. The results show that the mechanism with the ends of the legs sliding can obtain a better dynamic performance. This study offers primary theories for buffering dynamics and an evaluation of landing buffer performance,and it establishes a theoretical basis for studies and engineering applications.

Impact response and energy absorption of metallic buffer with entangled wire mesh damper

An innovative metallic buffer consisting of series-connected hat-shaped entangled wire mesh damper(EWMD)and parallel springs are proposed in this work to enhance the reliability of engineering equipment.The impact response and the energy dissipation mechanism of hat-shaped EWMD under different quasi-static compression deformations(2-7 mm)and impact heights(100-200 mm)are investigated using experimental and numerical methods.The results demonstrate distinct stages in the quasi-static mechanical characteristics of hat-shaped EWMD,including stiffness softening,negative stiffness,and stiffness hardening.The loss factor gradually increases with increasing compression deformation before entering the stiffness hardening stage.Under impact loads,the hat-shaped EWMD exhibits optimal impact energy absorption when it enters the negative stiffness stage(150 mm),resulting in the best impact isolation effect of metallic buffer.However,the impact energy absorption significantly decreases when hat-shaped EWMD enters the stiffness hardening stage.Interestingly,quasi-static compression analysis after experiencing different impact loads reveals the disappearance of the negative stiffness phenomenon.Moreover,with increasing impact loads,the stiffness hardening point progressively shifts to an earlier stage.

Contract theory based incentive mechanism design for buffer resource in wireless caching networks

Evidences indicate that,due to the limited caching capacity or inaccurate estimation on users’preferences,the requested files may not be fully cached in the network edge.The transmissions of the un-cached files will also lead to duplicated transmissions on backhaul channels.Buffer-aided relay has been proposed to improve the transmission performance of the un-cached files.Because of the limited buffer capacity and the information asymmetric environment,how to allocate the limited buffer capacity and how to incentivize users in participating buffer-aided relay have become critical issues.In this work,an incentive scheme based on the contract theory is proposed.Specifically,the backlog violation probability,i.e.,the buffer overflow probability,is provided based on the martingale theory.Next,based on the backlog violation probability,the utility functions of the relay node and users are constructed.With the purpose to maximize the utility of the relay node,the optimal contract problem is formulated.Then,the feasibility of the contract is also demonstrated,and the optimal solution can be obtained by the interior point method.Finally,numerical results are presented to demonstrate effectiveness of the proposed contract theory scheme.

Design of an Automatic Autonomous Mini Prone-cone Microsatellite Docking Mechanism

The capability of docking, refueling, repairing, and updating microsatellites using automatic autonomous vehicles will be of significance critical value for design and operation of several space systems in the near feature. Automatic docking capability was successfully tested by many institutions such as National Space Development Agency in Japan, European Space Agency, National Aeronautics and Space Administration in USA, etc. However, there is still much more space for improvement of degree of automation during the process of docking with large deviations of the initial attitude. A novel automatic autonomous probe-cone docking mechanism used for microsatellite docking is proposed. This docking mechanism is designed according to the design indices such as miniaturization, degree of automation and automatic capture capability within large deviation of the initial attitude. On the basis of the virtual work principle, the dynamics modeling of the docking process is presented. The position of the contact point is then analyzed. Comprehensive system level simulation is conducted in the 13 kinds of typical operating conditions with the initial deviations. Capture performance is analyzed. The simulation results show that the docking mechanism can be smoothly captured within 2 s in all cases of large attitude deviation between the active and passive spacecrafts. A virtual prototype model of the docking mechanism is established through ADAMS for further verifying the correctness of the buffer parameter model and the autonomous docking capability. A laboratory platform is designed for on-the-ground experimental validation of the property of mini probe-cone docking mechanism. Repeated docking tests prove the proposed design of the mini probe-cone docking mechanism system for its high reliability, and automatic capture capability within large attitude range. The kinetic model of the docking capture process and the mechanism structure could provide some references for similar mechanism design of in-orbit spacecraft.

膨润土砌体墙受压性能及其本构模型的构建

我国高放地质处置库“三步走”战略稳步推进,研究缓冲/回填材料砌体结构力学性能及其破坏特性,可为缓冲/回填材料砌体结构的设计,以及砌块的地面堆砌储存提供基础数据。本文采用合适的压制路径将高庙子钠基膨润土粉末压制成砌块,并采用干砌方法堆砌成砌体墙,设计并进行了砌块单元间界面性能试验和轴心抗压试验,得到了砌块单元间界面剪切强度与剪切位移关系,分析了砌体墙应力-应变曲线和破坏形态。试验结果表明,砌体墙变形破坏经历特性变形、局部裂纹扩展、竖向裂纹贯通、失稳破坏和残余变形几个阶段。砌体墙的第一条裂隙出现在单个砌块单元内部,反映了砌块单元的压制质量是控制砌体墙工程性能的重要影响因素之一。基于试验数据,通过对比分析施楚贤、朱伯龙、TURNSEK和HODGKINSON及仲继清的本构关系发现,在峰前上升曲线段采用试验数据对仲继清模型参数进行修正,获得的理论应力-应变曲线与试验曲线较为吻合。

落石冲击下压实度对红层泥岩垫层缓冲机制影响研究

西南地区山地众多,落石频发,红层地质分布广泛,工程上红层隧道区可用红层泥岩作为棚洞垫层材料以抵抗落石冲击。但红层泥岩为细粒黏性缓冲材料,与无黏性粗粒材料不同,压实度对其缓冲机制影响仍不明晰,为此开展落石冲击红层泥岩垫层材料模型试验及数值模拟研究。通过搭建室内落石冲击试验平台,进行红层泥岩材料不同压实度下的模型冲击试验,监测落石及垫层内加速度大小,研究压实度对垫层缓冲效果的影响规律,并借助离散元(PFC)与有限差分(FLAC)耦合方法对模型试验进行了对比验证,揭示了压实度对红层泥岩垫层缓冲机制的影响规律。研究结果表明:1)不同压实度中(K=0.9、0.8、0.7),压实度越低,落石冲击力越小,K=0.7的冲击力较K=0.9减少54.08%;2)垫层内峰值加速度随水平距离增加呈指数衰减,且压实度越小,垫层加速度衰减越显著;3)重复冲击使垫层缓冲效果存在劣化现象,导致落石冲击力及垫层内加速度增加,工程中需加以注意;4)压实度低时,力链越不稳定,力链因易破坏重组而无法提供长期、稳定阻力,致使落石冲击力降低;同时垫层松散使冲击波传播时间增加,垫层吸收更多能量;因此,压实度低时垫层具有更好的缓冲效果。研究结果可为西南地区红层泥岩垫层材料的应用提供借鉴。

高浓度磷酸盐缓冲液中多巴胺电化学氧化过程的在线质谱分析

研究高浓度缓冲盐体系中物质的电化学氧化还原过程,对于准确理解电化学反应机理具有重要意义。本研究研制了一款体积小、性能稳定、结构简单、制作方便的流动电解池,将其与大气压化学电离质谱联用,构建了一种可在线分析高浓度缓冲盐溶液中电化学过程的电化学-质谱分析装置,用于在线、实时研究缓冲盐溶液中多巴胺的电化学氧化过程。结果表明,通过热沉积方式可高效地在线去除缓冲溶液中的无机盐组分,有机组分可经大气压化学电离方式进行离子化,随后进入质谱检测。多巴胺电化学氧化质谱分析结果表明:在0 V氧化电位下,多巴胺不发生氧化,主要获得多巴胺的质子化信号m/z 154[M+H]^(+);当氧化电位为+0.3 V时,除多巴胺的质子化信号外,还可获得多巴胺失去4个e-的氧化产物多巴色素(dopachrome)质子化峰m/z 150[M+H]^(+),以及多巴色素与多巴胺通过分子间氢键形成的加合物信号m/z 303[M+H]^(+);当氧化电位升高至+0.6 V时,氧化产物m/z 150和303的丰度进一步提高。

汽车碰撞磁流变脂缓冲器设计与仿真分析

针对目前汽车保险杠阻尼系数不可调,只在特定碰撞工况下具有较理想缓冲性能的缺陷,设计一款工作模式多样、磁场利用率高以及多通道流动的磁流变脂缓冲装置。基于Herschel-Bulkley力学模型推导出阻尼力与速度和电流之间的关系,利用MATLAB/Simulink软件进行汽车碰撞仿真,分析汽车在中低速碰撞时不同电流下汽车碰撞加速度、速度、位移和冲击力变化情况,同时与传统汽车保险杠碰撞进行对比,验证了磁流变脂缓冲装置在汽车碰撞方面具有速度和加速度变化缓慢、冲击力缓冲效果良好、碰撞位移减小的优越性。

煤矸石分选柔性机械爪设计

为了解决煤矸石底面或周边不平整工况下无法精准抓取的难题,设计一种由缓冲装置和抓取装置组成的煤矸石分选柔性机械爪。缓冲装置通过高频低幅摆动,减弱并消除机械爪突然停止和遭受撞击的能量。抓取装置根据煤矸石大小,通过横向连杆结构控制机械爪的张开角度和抓力。机械爪下爪受力超过限值时将不再向下运动,并微调抓取角度,自适应不规则物体形状,减少了损伤率、带煤率和受阻率,提高了煤矸石的抓取率和夹持的稳定性。

飞机起落架收放机构的设计与仿真分析

飞机起落架收放机构是飞机起降过程中的关键部件,围绕起落架的结构形式、收放方式两方面开展研究,以安全性能高、结构紧凑且易于收放作为设计目标,以可折叠前三点式作为布置形式,利用三维设计软件对机构进行了建模,通过理论计算对飞机起落架收放收放机构的关键零部件防扭臂、缓冲器、位置锁和收放作动筒等进行了结构设计,并对收放机构的运动过程进行了运动仿真分析,验证了其运行的合理性和可行性,最后对收放作动筒的外筒和内筒进行了有限元分析,得到外筒和内筒的最大应力分别为44.00 MPa与46.09 MPa,均小于材料的屈服极限,符合设计要求。

Bionic Design and Analysis of a Novel Quadruped Robot with a Multistage Buffer System

Large quadruped mammals,such as ruminants,have outstanding motion ability,including running and bounding.These advanced motion abilities are related to the buffer effect of their complicated musculoskeletal systems.However,the buffer effect of most bio-robots is not satisfactory owing to the simple design of their buffer systems.In this paper,a physiological analysis of the ruminant musculoskeletal system is presented to explain the intrinsic buffer mechanism of motion.Based on the physical buffer parts of the ruminant limbs,the corresponding bionic mappings were determined.These mappings were used to guide the mechanism design of the robot multistage buffer system.The multistage buffer system includes two main buffer mechanisms:the first stage and the second stage.The buffer mechanism analysis of the first stage and multiple stages is discussed in theory to compare the effects between the normal single buffer system and the novel multistage buffer system.Then,the detailed mechanical structure of the limbs was designed based on the limb mechanism design.To further verify the superior efficacy of the multistage buffer system,the corresponding walking simulation experiments were conducted after the virtual prototype of a quadruped robot with a novel limb was built completely.Both theoretical analysis and simulation experiments prove that the bionic robot design with the novel multistage buffer system achieves better motion performance than the traditional robot buffer design and can be regarded as the design template of the robot limb.

Environment Adaptability Evaluation for Buffering Airbag of Heavy Equipment During Airdrop Landing

Aimed at the difficulties in analyzing the buffer characteristics of airbag system by using thermodynamic or experimental method only,the finite element method was used to establish nonlinear models for heavy equipment and its airbag system.The models' efficiency and correctness were validated by using on-site experiment data in vehicle airdrop landing.The simulation results agree very well with the experiment results.Then,the environment adaptability of airbag system of heavy equipment under high-altitude condition was studied by using the models.Finally,some solutions were given to solve the overturn problem in the landing.

Kinetic and Mechanistic Study of Oxidation of Piperazines by Bromamine-T in Acidic Medium

Oxidations of piperazine, 1-methylpiperazine and 1-ethylpiperazine by bromamine-T (BAT) in buffered acidic medium have been kinetically studied at 303 K. The reaction shows a first-order dependence of the rate each on [BAT]0 and [piperazine]0, and an inverse fractional-order dependence on [H+]. The additions of halide ions and the reduction product of BAT, p-toluenesulfonamide, have no effect on the reaction rate. The variation of ionic strength of the solvent medium has no influence on the rate. Activation parameters have been evaluated from the Arrhenius and Eyring plots. A common mechanism consistent with the kinetic data has been proposed for all piperazines. The protonation constants of substrates have been evaluated. The Hammett linear free-energy relationship has been observed for the reaction with ρ = ?0.5 indicating that the electron-donating groups enhance the reaction rate by stabilizing the transition state. An isokinetic relationship observed shows β = 368 K indicating the dominance of enthalpy factors on the reaction rate.

Simulations of THM processes in buffer-rock barriers of high-level waste disposal in an argillaceous formation

The main objective of this paper is to investigate and analyse the thermo-hydro-mechanical（THM） coupling phenomena and their influences on the repository safety.In this paper,the high-level waste（HLW） disposal concept in drifts in clay formation with backfilled bentonite buffer is represented numerically using the CODE BRIGHT developed by the Technical University of Catalonia in Barcelona.The parameters of clay and bentonite used in the simulation are determined by laboratory and in situ experiments.The calculation results are presented to show the hydro-mechanical（HM） processes during the operation phase and the THM processes in the after-closure phase.According to the simulation results,the most probable critical processes for the disposal project have been represented and analyzed.The work also provides an input for additional development regarding the design,assessment and validation of the HLW disposal concept.

ON OPTIMAL LOCAL BUFFER ALLOCATION IN FLEXIBLE MANUFACTURING SYSTEMS

An optimal design problem of local buffer allocation in the FMS is discussed in order to maximize a reward earned from processed jobs at all workstations. Structural properties of the optimal design problem are analyzed for the model with two job routing policies. Based on these properties, approaches to optimal solutions are given.

双线圈和螺线管复合式电磁斥力机构运动特性分析

为了满足高压直流断路器对其操动机构快速性和高电压等级的要求,针对126 kV真空断路器设计了一种适用于长行程且具有较高分合闸速度的新型电磁斥力机构,其由双线圈和螺线管式电磁斥力机构串联而成。首先,运用有限元方法进行电磁力仿真模拟,通过对机构的电磁斥力和位移/时间特性分析,初步验证了其可行性。然后,采用单一变量法对其运动特性进行仿真分析,得到了机构间相互配合关系和参数优化设计原则。最后,为降低分闸弹跳,设计电磁式缓冲器,分析了缓冲驱动电路参数和缓冲投入时间对缓冲特性的影响。研究表明:该电磁斥力机构具有刚分速度大,加速时间长,适用于长行程驱动的特性。在分闸电容3500μF、电压1200 V,缓冲电容3500μF、电压1800 V参数群组配合下,所设计电磁斥力机构全行程开断时间较短,仅有5.41 ms。

基于平台力波动的压溃管结构参数优化设计

在列车碰撞时,车钩缓冲装置是最先开始发生变形的部分,其能量吸收特性、压溃平稳性会影响后续列车碰撞的动态行为特性。为提高车钩缓冲装置在碰撞过程中压溃的平稳性,采用基于模型的多目标遗传算法的优化方法,研究车钩压溃管吸能结构碰撞力学参数的最优配置。通过建立车钩压溃管仿真模型,分析比对仿真模型与试验测试的力学曲线,采用样本方差S2体现平台力波动,分析压溃管厚度T,加压管锥角α和加压管外半径r对比吸能(Sea)、平台力(Favg)和平台力波动(S2)的影响。将Sea,|Favg-1200|作为评价指标,S2作为约束,基于试验设计采用径向基函数法建立T,α和r关于Sea和|Favg-1200|的响应面模型,并基于模型采用多目标遗传算法对车钩压溃管结构的力学参数进行多目标优化,通过多目标优化的帕累托前沿得到了车钩压溃管的最优参数配置。研究结果表明:在所有的设计变量中,加压管外半径r对Sea的影响最大,压溃管厚度T对Favg影响最大,加压管外半径r对S2影响最大。除加压管外半径r对S2是负相关的关系,其余变量对Sea,Favg和S2都是正相关的关系。在最优参数配置下Sea提高了12.16%,Favg提高了8.35%,S2下降了58.47%,吸能量提高了6.34%。优化后的力学参数配置方案提高了车钩的吸能量,降低了压溃管平台力的波动,提高了车钩压溃管在碰撞过程中压溃的平稳性。

不停丝工况下的自动化铲板设计

针对纺丝箱内可进行铲板操作的空间有限且狭小的问题,提出铲板和排丝功能一体化的自动化铲板系统设计。应用滑环设计实现了排丝组件中居中旋转的吸丝漏斗和静止延伸的排丝管道的结构连接,从而保障排丝顺畅;将杠杆原理和弹簧串并联作用相结合,开展了铲板组件的缓冲结构设计,以实现悬臂偏置的铲刀和喷丝板面的有效贴合和刮铲,并应用ANSYS分析验证了该缓冲设计可保证刀刃与喷丝板面的接触力分布均匀;为避免铲刀抵触喷丝板面时的刚性冲击,对铲板组件的对刀运动进行力学建模,并计算得到铲板组件缓冲结构的具体参数设计值。最后开发不停丝工况下的自动化铲板模拟试验台,通过实验验证了自动化铲板系统的铲板和排丝功能一体化的结构设计的正确性和有效性。

焊装生产线积放式缓存(ACC Buffer)机电设计安装要求

针对整车制造焊装积放式缓存系统,就其机电结构和主要部件功能进行了论述。同时按照不同使用场景,对其各方面的安全设计要求进行详细探讨。从而对焊装生产线积放式缓存的机电设计安装原则得到完整的一般性理解。

油液温度对液压缓冲阀动力学特性影响分析

油温对重型车辆机械控制式液压缓冲阀的运动部件动力学特性及出口压力调节过程均会产生显著影响。依据某重型车辆液压缓冲阀,建立阀芯及缓冲活塞的动力学模型,通过流场仿真对阀芯过流面积、流量系数及射流角进行详细解析,最后在20~100℃油温下对换挡缓冲液压系统进行仿真分析和实验对比研究,从而揭示了油温对缓冲阀运动部件及调压过程的作用机理。研究表明,随着温度升高:缓冲阀入口流量系数小幅增大,入口射流角及阀芯黏性摩擦力先增大后减小;阀芯和活塞运动速度增大;100℃时的压力调节时间较20℃时缩短36%,缩短幅值大;缓冲结束时,对稳定输出的压力影响不大;缓冲阀在缓冲升压阶段的起止压力不会因油液温度变化产生较大变化。