基于影响系数的新型全柔性微动并联机器人运动特性分析

研究了新型全柔性微动三平移并联机器人机构{R／／R／／R／／P（4R）}／／{R／／R／／P（4R）／／R}上{R／／R／／R／／P（4R）}的运动学特性，并进行了模拟仿真验证。首先求解机构的位置正解方程，并对该并联机构的运动学解耦特性进行分析，发现该三平移机构为近似完全解耦的机构；然后利用基于影响系数的方法，比较容易地推导出了该机构的速度、加速度的准确表达式，避免了繁琐的正解方程的求导微分；最后利用ADAMS软件、MATLAB软件对机构的运动学特性进行了仿真模拟与理论计算，验证了理论推导的正确性。     

固定-导向柔顺杆件6R伪刚体模型

为提高固定-导向型伪刚体模型的计算精度,基于伪刚体模型的原理提出了一种固定-导向6R伪刚体模型。建立了该模型的运动学方程,并根据逆运动学分析方法及优化算法求解了模型的4个最优特征半径系数和3个扭簧刚度系数。通过数值算例模拟固定-导向6R伪刚体模型的末端动作路径,并将其与固定-导向2R伪刚体模型及柔顺杆件的末端路径进行对比。结果表明,固定-导向6R伪刚体模型能够更加精确地模拟相应柔顺杆件的末端动作过程,且其相对误差几乎为0。最后,通过ANSYS有限元分析实例验证了该模型在实际计算中的精确性。     

基于3R伪刚体模型的柔顺杆动力学建模及分析

介绍了柔顺机构中的3R伪刚体模型。利用Matlab软件的符号运算推导出了该模型柔顺杆的动能和变形能方程。应用拉格朗日方程建立了柔顺杆末端载荷作用下的动力学模型。特征半径系数和刚度系数代入方程组获得向心力、惯性力矩、科氏惯性力矩等系数,并分析了其相互耦合对伪刚体角变量的影响。通过数值求解二阶变系数微分方程组获得动态响应曲线和位形图,曲线反映出伪刚体杆从1杆到3杆振幅逐渐增大、杆件的耦合降低的振荡情况,较2R伪刚体模型的动力学方程模拟柔顺杆动力特性更具实用性和通用性。     

结构钢缺口试样的R－S－N曲线和等寿命图

基于金属材料非对称循环疲劳极限的估算公式、R－S－N曲线方程和等寿命曲线方程,给出结构钢缺口试样的疲劳极限估算公式、R－S－N曲线方程和等寿命曲线方程及用其方程绘制的R－S－N曲线与等寿命图。     

钛合金缺口试样非对称循环疲劳极限的估算

基于金属材料非对称循环疲劳极限的估算公式、R－S－N曲线方程和等寿命曲线方程，给出钛合金缺口试样的疲劳极限估算公式、R－S－N曲线方程和等寿命曲线方程及用其方程绘制的R－S－N曲线和等寿命图。     

空间8R髋关节康复并联机构的运动学分析

提出了一种二自由度空间8R并联机构用于人体髋关节康复。建立空间8R并联机构模型,运用螺旋理论对机构的初始位形及一般位形进行分析;采用D-H法建立空间8R并联机构的几何模型和运动学方程,得出了机构的运动学方程;运用Adams软件和理论计算共同验证了空间8R并联机构运动学方程的正确性,得出了机构在不同运动下,一个周期内的角位移变化规律。此空间8R并联机构性能稳定,能够进行平稳运动,可以有效提高髋关节康复效果。     

结构钢缺口试样的R—S—N曲线和等寿命图

基于金属材料非对称循环疲劳极限的估算公式、R－S－N曲线方程和寿命曲线方程，给出结构钢缺口试样的疲劳有限估算公式、R－S－N曲线方程和等寿命曲线方程及用其方程绘制的R－S－N曲线与等寿命图。     

结构分析有限元神经计算的时间和误差特性研究

从神经网络的基本方程出发,在理论、数值计算方面对弹性力学神经计算的稳定时间和计算精度进行了研究.理论分析表明偏置电容C、信号网络神经元的放大倍数β影响网络的稳定时间;偏置电阻R、约束网络神经元的惩罚系数α影响求解精度,但在工程上没有必要对R,C,β,α等进行严格的限制.数值模拟结果也证实了理论分析的结论.     

柔顺杆件固定-导向1P2R伪刚体模型

针对固定-导向模式的伪刚体模型模拟柔顺杆件末端位置精度不高且无法表现轴向变形的问题,基于伪刚体模型的原理提出了一种高精度的固定-导向1P2R伪刚体模型。首先综合考虑柔顺杆件各个方向的变形,构建了包含两个转动副和一个移动副的固定-导向1P2R伪刚体模型;其次建立了该模型的运动学方程,并根据优化算法求解了伪刚体模型的最优特征半径系数,利用一元线性回归方法得到了该模型的弹簧和扭簧刚度系数;最后通过数值算例模拟固定-导向1P2R模型末端的动作路径,并将其与固定-导向伪刚体模型及柔顺杆件的末端路径进行对比。结果表明,固定-导向1P2R伪刚体模型完全能够模拟相应柔顺杆件的末端动作过程,且模拟精度高于固定-导向伪刚体模型。研究证明了该模型的优越性,对柔顺机构的变形分析亦有重要参考意义。     

空间7R机构位移分析的新研究

空间一般七杆7R（R代表转动付）机构的位移分析是机构学中尚未彻底解决的最困难问题之一,F.Freudenstein将它喻为机构运动分析中的珠穆朗玛峰[2]。J.Duffy等发表过一篇关于7R机构位移分析的文章[1],导出的输入输出方程是32次多项式。但是,最近,人们相信7R机构的输入输出方程应该是16次。笔者应用复数法,经过努力,终于导出了这个16次方程,从而解决了这一难题。     

Valve dynamic and thermal cycle model in stepless capacity regulation for reciprocating compressor

The existing researches of stepless capacity regulation system by depressing the suction valve for reciprocation compressor always adopt hypothesis that the compressor valves are open or close instantaneously, the valve dynamic has not been taken account into thermal cycle computation, the influence of capacity regulation system on suction valves dynamic performance and cylinder thermal cycle operation has not been considered. This paper focuses on theoretical and experimental analysis of the valve dynamic and thermal cycle for reciprocating compressor in the situation of stepless capacity regulation. The valve dynamics equation, gas forces for normal and back flow, and the cylinder pressure varying with suction valve unloader moment during compression thermal cycle are discussed. A new valve dynamic model based on L-K real gas state equation for reciprocating compressor is first deduced to reduce the calculation errors induced by the ideal gas state equation. The variations of valve dynamic and cylinder pressure during part of compression stroke are calculated numerically. The calculation results reveal the non-normal thermal cycle and operation condition of compressor in stepless capacity regulation situation. The numerical simulation results of the valve dynamic and thermal cycle parameters are also verified by the stepless capacity regulation experiments in the type of 3L-10/8 reciprocating compressor. The experimental results agree with the numerical simulation results, which show that the theoretical models proposed are effective and high-precision. The proposed theoretical models build the theoretical foundation to design the real stepless capacity regulation system.     

进气畸变对发动机压缩系统稳定性影响的数值模拟

介绍了一种在发动机环境下评定航空燃气涡轮发动机压缩系统稳定工作边界的数学物理模型。研究了进气畸变对航空燃气涡轮发动机压缩系统稳定工作边界的影响。对总压畸变进气条件下压气机稳定工作边界的变化进行了计算分析,结果表明进气总压畸变对发动机稳定性有很大的影响,使得压气机稳定工作边界在压气机的特性图中向右下方移动,降低了发动机的喘振裕度。主要数学物理模型可以正确地反映发动机压缩系统的工作状况,用它判断发动机不稳定工作点的重复性和灵敏度都比较好。     

Noise source identification of the hermetic reciprocating compressor for refrigerator

Journal of Mechanical Science and Technology - Noise source identification of the hermetic reciprocating compressor for refrigerator has been investigated. Since the compressor shell housing is...     

冰箱用全封闭压缩机噪声分析与降噪措施的探讨

对冰箱压缩机的噪声进行了分析，并对某一型号的压缩机进行噪声测试，从理论上提出了一些降噪措施，并运用到压缩机的实际产品中。实验证明，改进后压缩机的噪声比改进之前有所降低。     

Vibration reduction of a single cylinder reciprocating compressor based on multi-stage balancing

Basically, a reciprocating compressor consists of three main mechanical subsets: the hermetic housing, the crankcase and the rotor-crankshaft assembly. The counterweight mass located on the rotor-crankshaft is designed to balance the eccentric masses of the slider-crank mechanism which predominate in comparison to the residual distributed unbalance masses due to manufacturing. However, excessive vibration levels can be observed. The objective of the study is to perform a reliable finite element model for balancing the compressor by taking into account the dynamic behavior of the three subsets. The rotor-crankshaft assembly is considered as a flexible body, while the crankcase and the housing are assumed to be rigid. The rotor-crankshaft model is updated by using experimental modal analysis at rest. The characteristics of the fluid film bearings are speed of rotation dependant. The forces of the pressure and of the slider-crank mechanism are expanded by using Fourier transformation. The Influence Coefficient Method is used to investigate several balancing solutions to reduce the vibratory levels of the target plane located on the three main subsets. The experiments carried out show that this multi-stage balancing procedure is rather more efficient than a classical approach based only on the dynamic balancing of the rotor crankshaft assembly.     

排气压力脉动的全封闭往复式压缩机转速测量方法

提出一种基于排气压力脉动的全封闭往复式压缩机转速测量的新方法。全封闭往复式压缩机的吸排气阀片伴随着活塞的往复运动而开启与关闭,使压缩机吸排气产生压力脉动,排气压力脉动比吸气压力脉动明显。排气阀室较排气管出口压力脉动幅值明显,去除趋势项后经CZT变换得到的脉动频率和转速一致,故可将排气管出口压力作为新方法的采样信号。在不同压缩比工况下,新方法测得转速与压缩机实际转速进行对比,实验表明新方法在不同负载工况下都有效,精度为±1 r/min;测量时间为1 s。     

应用小孔喷注噪声原理分析全封闭活塞式制冷压缩机吸排气阀噪声

制冷剂气体流经压缩机吸、排气阀时,由于气流穿过狭小的阀隙,会产生类似喷注的噪声,将小孔喷注噪声原理应用在吸、排气气阀开启瞬间产生的噪声分析中,并理论定量分析制冷剂蒸气流经吸、排气阀产生气流噪声的机理,着重分析了吸、排气过程转角与压差、转角与声压级、压差与声压级的关系.根据噪声产生原理,指出降低噪声的根本途径是降低气流通过气阀前后的压力损失,并给出降低气流噪声的主要途径是:提出减小阀片刚性、厚度以及扩大排气孔孔径等.并给出了几种通过改善吸、排气阀结构来降低压缩机噪声的方法.     

Effect of R600a on tribological behavior of sintered steel under starved lubrication

This paper describes the impact of the isobutane refrigerant on the wear performance of tribopairs at hermetic compressor bearings. The tribological behavior of 100Cr6 steel pin is investigated under starved lubrication condition in air and R600a environments when running against sintered steel which was treated with and without steam. EDS and SEM are carried out on pin and plate samples after wear tests. The results indicate that wear durability is lower for the tests with R600a than those with air. The adverse effect of R600a on wear rate is linked to the change in the viscosity and foaming characteristics of the oil in the presence of R600a as well as the lack of oxides.     

涡旋压缩机工作过程模拟及传热分析

根据涡旋压缩机的运转规律,得到了绝热状态涡旋压缩机非定常流动的数值模拟计算方法;对涡旋压缩机理论计算模型进行网格无关性验证、动网格重构验证,保证其数值模拟计算结果的准确性.得到了涡旋压缩机工作过程的压力场、温度场、速度场分布规律,得到其工作过程曲线与各工作腔的泄漏规律,并与理论绝热过程进行对比,验证了所采用的数值模拟计算方法的正确可行性.进而探究考虑流热耦合传热的涡旋压缩机工作过程的数值模拟计算方法,提出通过合理地设置壁面热力条件参数实现涡旋压缩机达到热力平衡状态的数值模拟计算方法.     

内燃式压缩机动力学分析

将传统内燃机与往复活塞式压缩机工作原理、技术及结构进行集成,提出了一种可方便地将热能转换为气体压力能的内燃式压缩机.建立了等效动力学模型,采用MATLAB软件对其进行了动力学仿真计算.给出了内燃式压缩机一个工作循环中曲轴瞬时转速与转角之间的关系曲线,确定了曲轴速度波动系数与飞轮转动惯量之间的关系,为内燃式压缩机的工作平稳性设计奠定了基础.