A Stiffness Variable Passive Compliance Device with Reconfigurable Elastic Inner Skeleton and Origami Shell

Devices with variable stiffness are drawing more and more attention with the growing interests of human-robot interaction,wearable robotics,rehabilitation robotics,etc.In this paper,the authors report on the design,analysis and experiments of a stiffness variable passive compliant device whose structure is a combination of a reconfigurable elastic inner skeleton and an origami shell.The main concept of the reconfigurable skeleton is to have two elastic trapezoid four-bar linkages arranged in orthogonal.The stiffness variation generates from the passive deflection of the elastic limbs and is realized by actively switching the arrangement of the leaf springs and the passive joints in a fast,simple and straightforward manner.The kinetostatics and the compliance of the device are analyzed based on an efficient approach to the large deflection problem of the elastic links.A prototype is fabricated to conduct experiments for the assessment of the proposed concept.The results show that the prototype possesses relatively low stiffness under the compliant status and high stiffness under the stiff status with a status switching speed around 80 ms.

Force Control Compensation Method with Variable Load Stiffness and Damping of the Hydraulic Drive Unit Force Control System

Each joint of hydraulic drive quadruped robot is driven by the hydraulic drive unit（HDU）, and the contacting between the robot foot end and the ground is complex and variable, which increases the difficulty of force control inevitably. In the recent years, although many scholars researched some control methods such as disturbance rejection control, parameter self-adaptive control, impedance control and so on, to improve the force control performance of HDU, the robustness of the force control still needs improving. Therefore, how to simulate the complex and variable load characteristics of the environment structure and how to ensure HDU having excellent force control performance with the complex and variable load characteristics are key issues to be solved in this paper. The force control system mathematic model of HDU is established by the mechanism modeling method, and the theoretical models of a novel force control compensation method and a load characteristics simulation method under different environment structures are derived, considering the dynamic characteristics of the load stiffness and the load damping under different environment structures. Then, simulation effects of the variable load stiffness and load damping under the step and sinusoidal load force are analyzed experimentally on the HDU force control performance test platform, which provides the foundation for the force control compensation experiment research. In addition, the optimized PID control parameters are designed to make the HDU have better force control performance with suitable load stiffness and load damping, under which the force control compensation method is introduced, and the robustness of the force control system with several constant load characteristics and the variable load characteristics respectively are comparatively analyzed by experiment. The research results indicate that if the load characteristics are known, the force control compensation method presented in this paper has positive compensation effects on the load characteristics variation, i.e., this method decreases the effects of the load characteristics variation on the force control performance and enhances the force control system robustness with the constant PID parameters, thereby, the online PID parameters tuning control method which is complex needs not be adopted. All the above research provides theoretical and experimental foundation for the force control method of the quadruped robot joints with high robustness.

Theoretical and experimental research on a new system of semi-active structural control with variable stiffness and damping

In this paper,a new system of semi active structural control with active variable stiffness and damping (AVSD) is suggested.This new system amplifies the structural displacement to dissipate more energy,and in turn,effectively reduces the structural response in the case of relatively small story drifts,which occur during earthquakes.A predictive instantaneous optimal control algorithm is established for a SDOF structure equipped with an AVSD system Comparative shaking table tests of a 1/4 scale single story structural model with a full scale control device have been conducted.From the experimental and analytical results,it is shown that when compared to structures without control or with the active variable stiffness control alone, the suggested system exhibits higher efficiency in controlling the structural response,requires less energy input,operates with higher reliability,and can be manufactured at a lower cost and used in a wider range of engineering applications.

A low-frequency pure metal metamaterial absorber with continuously tunable stiffness

To address the incompatibility between high environmental adaptability and deep subwavelength characteristics in conventional local resonance metamaterials,and overcome the deficiencies in the stability of existing active control techniques for band gaps,this paper proposes a design method of pure metal vibration damping metamaterial with continuously tunable stiffness for wideband elastic wave absorption.We design a dual-helix narrow-slit pure metal metamaterial unit,which possesses the triple advantage of high spatial compactness,low stiffness characteristics,and high structural stability,enabling the opening of elastic flexural band gaps in the low-frequency range.Similar to the principle of a sliding rheostat,the introduction of continuously sliding plug-ins into the helical slits enables the continuous variation of the stiffness of the metamaterial unit,achieving a continuously tunable band gap effect.This successfully extends the effective band gap by more than ten times.The experimental results indicate that this metamaterial unit can be used as an additional vibration absorber to absorb the low-frequency vibration energy effectively.Furthermore,it advances the metamaterial absorbers from a purely passive narrowband design to a wideband tunable one.The pure metal double-helix metamaterials retain the subwavelength properties of metamaterials and are suitable for deployment in harsh environments.Simultaneously,by adjusting its stiffness,it substantially broadens the effective band gap range,presenting promising potential applications in various mechanical equipment operating under adverse conditions.

MRE耗能阻尼器力学性能及半主动控制分析

根据磁流变弹性体(magnetorheological elastomer,简称MRE)的可调力学特性提出了基于MRE的新型耗能阻尼器,并对制备完成的硅橡胶基磁流变弹性体及阻尼器分别进行力学性能试验。利用Matlab/Simulink对各层均装有MRE阻尼器的7层框架结构进行建模仿真分析,将被动控制与基于半主动控制策略的经典最优控制和序列最优控制进行比较。力学测试结果表明:MRE在0~500 mT磁感应强度下其剪切模量变化值达到132.43 kPa,磁流变效应约提高274%;增大加载幅值和加载速率,均能提高MRE阻尼器的力学性能;对阻尼器施加电流激励,在0~10 A增大过程中其等效刚度和阻尼可以实现连续可调。仿真结果表明:基于MRE阻尼器的半主动控制系统可以有效减小结构在地震作用下的响应,3种控制均能对结构动力响应起到良好的控制效果,其中序列最优控制算法的控制效果最为显著且精确度更高;系统在实际测试中需考虑多方面因素影响,尽可能减小误差。

大部件装配中的MRE被动柔顺装置研究

随着我国航天制造领域智能化要求的不断提升,利用工业机器人实现大部件的柔顺辅助装配对实现航天器的智能制造具有重要意义。然而在进行大部件的高精度装配时,机器人易受限于本体性能而难以弥补物理上的机械设计误差。据此,基于磁流变弹性体(Magnetorheological Elastomer,MRE)设计了一种可变刚度的被动柔顺装置置于机器人末端,并对其进行了仿真及实验测试,结果表明,升高通入电流可提高装置刚度,且装置在1 A电流差下的位移差约为20%,适配柔顺辅助装配的不同过程。

基于被动变阻尼变刚度装置组合隔震新体系性能化设计方法

被动变阻尼变刚度装置是一种无需外部能源输入和反馈控制的装置,具有变阻尼耗能和变刚度限位功能。当与隔震支座组合使用时,这种装置构成了一种新的隔震体系,能够有效控制不同类型和烈度大小的地震波。根据性能化设计理论,提出了针对组合隔震体系的设计方法,通过该方法可以完成隔震层中被动变阻尼变刚度装置和隔震支座的参数设计工作。研究还提供了完整的设计流程和详细的设计过程说明,并通过工程实例验证了设计方法的可行性和有效性。这种性能设计方法可以广泛应用于组合隔震新体系的工程设计领域,为相关工程提供了一种可靠的设计方法和技术支持。通过这种先进的设计方法,可使结构能够更好地应对地震带来的灾害,保障结构的安全性和稳定性。

Research on the evolution law of dynamic performance of CR400BF EMU train based on stochastic dynamics simulation

Purpose–This paper aims to obtain the evolution law of dynamic performance of CR400BF electric multiple unit(EMU).Design/methodology/approach–Using the dynamic simulation based on field test,stiffness of rotary arm nodes and damping coefficient of anti-hunting dampers were tested.Stiffness,damping coefficient,friction coefficient,track gauge were taken as random variables,the stochastic dynamics simulation method was constructed and applied to research the evolution law with running mileage of dynamic index of CR400BF EMU.Findings–The results showed that stiffness and damping coefficient subjected to normal distribution,the mean and variance were computed and the evolution law of stiffness and damping coefficient with running mileage was obtained.Originality/value–Firstly,based on the field test we found that stiffness of rotary arm nodes and damping coefficient of anti-hunting dampers subjected to normal distribution,and the evolution law of stiffness and damping coefficient with running mileage was proposed.Secondly stiffness,damping coefficient,friction coefficient,track gauge were taken as random variables,the stochastic dynamics simulation method was constructed and applied to the research to the evolution law with running mileage of dynamic index of CR400BF EMU.

磁流变惯容器设计与性能分析

为了提高传统磁流变阻尼器在低频域的减振性能,提出了一种新型磁流变惯容器,包括变阻尼单元和惯容单元两部分,由磁流变阀、液压马达与飞轮等组成。利用活塞杆与缸筒的相对运动,实现变阻尼单元内的磁流变液在磁流变阀内往复流动,通过调控线圈上电流大小改变输出阻尼的大小;同时,实现油液推动液压马达输出轴及飞轮转动,输出器件的惯容特性。为提高磁流变阀内置通道的磁场利用率,提出了磁路设计优化方法,采用有限元方法对磁流变阀内部磁场强度进行仿真。结合磁场仿真与理论分析,设计并试制了样机,搭建了器件性能平台进行测试。结果表明,所设计器件能够表现出惯容特性,具有良好的阻尼可控性。

Mechanism of electro-hydraulic exciter for new tamping device

A new tamping device which is driven by an electrohydraulic exciter was proposed to overcome the limitations of mechanically driven devices.The double-rod oscillation cylinder drives the tamping arm to realize vibration.A new spin valve was designed in order to fulfill dynamic state requirements of the oscillation cylinder.Parametric analysis was carried out by establishing mathematic model.Then,the relationships among the structure of valve port and the frequency,amplitude,output shock force of the cylinder were researched.An experimental device of the electrohydraulic exciter was established to validate the theoretical results.The signals were acquired by AVANT dynamic signal analyser of vibration.The results show that new tamping device can satisfy all kinds of complex working conditions with the flexible adjustment of frequency and amplitude.

基于可变刚度抗蛇行减振器的车辆动力学性能研究

CRH3系列高速动车组在长期服役过程中偶有发生蛇行运动稳定性裕量不足的问题,车辆装配T60型抗蛇行减振器,在车轮磨耗末期易发生构架横向加速度报警问题,装配T70型抗蛇行减振器,则在新轮或车轮磨耗初期易发生“晃车”的问题。针对晃车和报警问题开展可变刚度抗蛇行减振器的仿真与试验研究,以满足车辆在不同轮轨接触状态下车辆的蛇行运动稳定性需求。动力学仿真表明,可变刚度抗蛇行减振器能有效兼顾解决“晃车”和“报警”问题;进一步分析可变刚度抗蛇行减振器与两种高速踏面的适应性,采用S1002CN踏面时车辆临界速度高于350 km/h,而采用LMB10踏面时仅为220 km/h,且S1002CN踏面对应的平稳性和舒适度指标都优于LMB10踏面。最后通过整车滚振台架试验对变刚度抗蛇行减振器性能进行了试验验证,结果表明该减振器可以兼顾轮轨低锥度和高锥度匹配状态,可使车辆均具有良好的动力学性能。

PVDD装置多参数性能试验与隔震新体系控制分析

为研究被动变阻尼装置(passive variable damping device,简称PVDD)耗能性能和出力过程与多项参数设计的关系,对装置的不同形状控制阀和预压力值进行了性能试验。结果表明:孔型对装置最大阻尼力和出力过程产生影响,不同阻尼孔形状组合后可实现装置宽幅值、多出力过程的设计输出;预压力值对变阻尼启动条件产生影响,装置启动前表现为普通黏滞阻尼器,启动后可实现变阻尼力输出。将PVDD与隔震支座组合为隔震新体系,针对9层Benchmark模型进行了不同孔型和预压力值下结构控制效果的数值计算分析。结果表明:隔震新体系具有更好的减震效果;不同孔型的装置对不同形式地震有不同的控制效果;初始预压力使速度响应控制范围整体向后平移,装置有效控制区间得到最大利用。该研究成果对PVDD的设计应用具有参考和指导作用。

斜盘式恒压变量柱塞泵动态特性研究

该文针对变量泵压力控制元件对变量泵的压力输出特性进行研究,通过模拟仿真研究压力控制阀上阻尼孔尺寸和弹簧刚度的影响规律。研究结果表明阻尼孔尺寸增加,减小变量泵输出压力的稳定时间,同时增大变量泵的泄漏量,压力输出偏差也会增大;调压弹簧刚度增加导致变量泵压力响应速度降低,同时泵的输出压力偏差会有所增大。

机器人变刚度柔性关节实验装置研制

针对本科生和研究生关于共融机器人的教学需求,采用基于阿基米德螺旋移位原理的支点调节机构具体化变刚度方案,研制了一套具有“模块化程度高、刚度调节范围宽、具有可拓展性”等优点的机器人变刚度柔性关节实验装置。该装置可用于关节刚度标定、关节刚度调节等实验教学,涵盖机械原理、机械设计、传感与测试技术、机电伺服系统设计等课程内容,有助于学生深入了解共融机器人特性,进一步提升学生的实践动手能力。

Vibration suppression of composite panel with variable angle tow design and inerter-based nonlinear energy sink

This study investigates the vibration transmission and suppression of a laminated composite panel with variable angle tow(VAT)designs and an attached inerter-based passive nonlinear energy sink.Based on analytical and numerical methodologies,the substructure technique is used to obtain a steady-state dynamic response and the results are verified by experimental and analytical methods.It is demonstrated that fiber orientation has a significant impact on the natural frequencies.The dynamic responses and energy transmission path characteristics are determined and evaluated by forced vibration analysis.The main vibration transmission paths inside the structure are displayed using power flow density vectors.It is demonstrated that the dynamic responses of the plate can be changed considerably by using various fiber placement schemes and passive suppression devices.In addition,it is indicated that the vibration transmission paths are significantly influenced by the tailored fiber angles for improved dynamic performance.Our investigation enhances the understanding of enhanced vibration suppression designs of variable-stiffness composite plates with attached passive devices.

形状记忆合金改进型双凹面变曲率摩擦摆隔震支座理论分析与数值模拟研究

介绍了形状记忆合金改进型双凹面变曲率摩擦摆隔震支座(SMA-DVFPB)的基本构造,阐述了SMA-DVFPB应具备的功能。通过静力平衡原理推导了SMA-DVFPB在平面内运动时力与位移的关系式。通过ABAQUS软件对SMA拉索和隔震支座进行了模拟,分析了支座的滞回特性,并计算了理论与模拟误差。研究了不同摩擦系数、拉索横截面积对SMA-DVFPB滞回曲线、等效刚度及等效阻尼比的影响,并分析了支座的应力情况。结果表明:理论推导与数值模拟吻合较好,耗能和等效刚度误差在10%以内;SMA-DVFPB的耗能、等效刚度、等效阻尼比均随摩擦系数增大而增大;SMA-DVFPB的耗能、等效刚度随SMA拉索横截面积增大而增大,等效阻尼比随SMA拉索横截面积增大而减小;SMA-DVFPB最大应力出现在SMA拉索与支承板的连接处,设计时应充分考虑其在锚固处的应力集中情况。

磁流变动力系统变刚度变阻尼扭转吸振研究

磁流变变刚度变阻尼扭转动力吸振器(MR-VSDTVB)为实现动力传动系统扭转振动的有效半主动控制提供了思路.为此,建立了可变刚度和阻尼的汽车动力系统扭转振动动力学模型,加速工况下研究磁流变吸振器不同刚度和阻尼对系统输出响应的影响规律;进而,基于AMEsim和MATLAB/Simulink联合仿真,分析动力系统在加速工况下半主动控制对系统扭转振动的抑制效果,验证磁流变变刚度变阻尼扭转动力吸振器对动力传动系统扭转振动抑制的有效性.

向心式变摩擦阻尼器控制结构地震反应分析

介绍了向心式变摩擦阻尼器的原理及其基本力学性能，探讨了安装向心式变摩擦阻尼器结构在自由振动和强迫振动时的动力特性和动力反应特点，揭示了向心式变摩擦阻尼器引起结构抖振的机理，对安装向心式变摩擦阻尼器的结构的地震反应进行了分析，研究了向心式变摩擦阻尼器的参数对结构动力特性及地震反应的影响，给出了受控结构的非线性反应谱。

主—被动变刚度柔性单腿建模及能耗分析

为了改善传统刚性足式机器人运动高能耗问题,通过仿生学研究总结人类跑跳运动刚度与能效相关性,建立具有主—被动复合变刚度的串联柔性单腿数学模型,对减速器、柔性关节阻尼、功率流进行了详细描述;选定单腿模型主要参数并结合仿生学设计关节"三段式"被动变刚度特性,采用Hertz模型进行触地碰撞仿真,验证了具有被动变刚度特性的柔性单腿比定刚度柔性单腿具有更好的稳定性;通过对原地跳跃运动、支撑相水平运动两个过程的仿真计算,得出不同运动情况下腿部刚度与能耗的变化规律。研制了具有主—被动复合式变刚度柔性关节及基于该关节的单腿样机,联合NI-cRIO系统实验,验证了不同运动情况下合理调整刚度系数能够改善足式机器人能耗的结论,与仿生学研究相符。

风力发电系统机械传动机构动态模型研究

针对基于双馈感应发电机的变速风力发电机组轴系的特点,用等效集中质量法和动力学方程建立了机械传动机构动态的轴系模型,弥补了现有各种模型过于简化的不足。针对机械传动机构的动态模型,分别考虑了风机、发电机惯量及其传动轴系的阻尼系数与刚度系数对风力发电系统的瞬态性能影响,求出了机械传动机构动态轴系模型的自然振荡频率及其阻尼系数的解析表达式。仿真结果验证了理论分析的正确性,最后利用实验室所建风力发电地面模拟实验平台,基于可变惯量风机模拟器,改变不同的风机惯量值,验证了风机惯量对系统瞬态性能的影响,实验结果有力地支持了理论分析与仿真结果。