未知传递函数情况下主动电磁悬浮系统支承特性在线测量

分析了主动电磁悬浮系统支承的等效刚度和阻尼的理论计算方法。从闭环系统的角度出发,提出了一种不依赖于系统传递函数的等效刚度和阻尼的在线测量方法。以PID控制为例进行对比实验,分析了控制参数、激振幅度和激振频率对主动电磁悬浮系统支承等效刚度和阻尼的影响。结果表明,所提出的测量方法能够实时在线地对主动电磁悬浮系统支承的等效刚度和阻尼进行准确识别。     

磁悬浮轴承的刚度阻尼测量

提出一种磁悬浮轴承刚度阻尼的测量方法。通过对转子施加脉冲激振,计算局部时段的电磁力,识别出磁悬浮轴承的刚度和阻尼。仿真和实验研究表明,此方法可有效测量磁悬浮轴承刚度阻尼。     

径向-推力联合浮环动静压轴承动态特性试验研究

在径向-推力联合浮环动静压轴承理论计算和分析的基础上,设计制造了轴承试件及相关的试验装置,改制了试验台。采用静动法和激振法相结合首次测得了径向部分内外膜8个刚度系数和轴向部分2个刚度系数及径向部分总的4个阻尼系数和轴向部分的1个阻尼系数。根据试验数据绘制不同转速下各动特性系数随偏心率的变化曲线,并与理论计算结果进行比较,二者基本一致。     

正弦激振测定轴承的刚度和阻尼

在研究机床主轴系统动态性能时,必须知道轴承的支承参数,即,径向刚度K、径向阻尼C_r、角刚度K_c和角阻尼C_a,见图(1)。目前这些参数值,往往是通过试验确定。在结构分析中,刚度值可以通过静态或动态试验来测定,但阻尼系数的识别只能用动态方法测定,所以一般采用动态试验同时测定刚度和阻尼。在被测系统上施以单频的正弦扫频激振或是宽频的瞬态的随机激振,测出系统在激振力F的响应,根据参数识别的基本理论,就可求出系统的各参数。笔者在对某型机床主轴特性进行研究时,为了建立可供电算的主轴系统力学模型,采用一些     

滚动轴承支承刚度计算

滚动轴承的支承刚度计算是研究轴-滚动轴承系统动力学的关键问题之一。文中以深沟球轴承为例,采用力法和Hertz理论研究滚动轴承的受力与变形关系,在此基础上得到滚动轴承的支承刚度计算公式。着重探讨滚动体位置变化、离心力的作用、轴承的游隙和预紧、径向力和轴向力作用等因素对滚动轴承支承刚度的影响。计算结果表明:离心力的作用、轴承的游隙和预紧、径向力和轴向力作用对滚动轴承的支承刚度影响较大,滚动体位置变化对滚动轴承的支承刚度影响较小。所得结果为准确计算轴-滚动轴承系统动力学问题提供了前提条件。     

不同瓦面形貌参数的曲面可倾瓦推力轴承动特性仿真研究*

为了揭示瓦块曲面形貌参数对船舶可倾瓦推力轴承动特性的影响规律,建立可倾瓦推力轴承瞬态热流体动压润滑模型,采用轴向扰动法研究轴承刚度和阻尼系数的计算方法并进行了验证。设计6种瓦面形貌,仿真分析不同形貌类型和瓦面弯曲程度对推力轴承动特性的影响规律。结果表明：推力轴承刚度系数随激振频率的增加而上升,阻尼系数随激振频率的增加而下降;在相同激振频率下,仅考虑一个方向的形貌改变,周向瓦面凸起量的增加可以增加油膜厚度,降低轴承的刚度和阻尼系数,但径向凸起量的增加对轴承的刚度阻尼系数几乎无影响;仅考虑径向凹陷时,阻尼系数随凹陷量的增加而增加并可达到最大;当同时考虑周向和径向的形貌变化时,则周向凸起量是轴承主要的影响因素。     

缝纫机旋梭轴转子动力学特性研究

针对缝纫机旋梭轴系高速运行不稳定的问题,计算了旋梭轴系的转子动力学,分析了失稳的原因,对旋梭轴系稳定性进行了理论分析,对旋梭轴转子动力学特性进行了仿真研究。首先,根据缝纫机转子瞬时位置及其受力情况,推导出了转子动力学方程,建立了旋梭轴系动力学分析模型;然后,在ANSYS Workbench软件中对刚性支承下旋梭轴系进行了转子动力学仿真分析,通过模态分析和不平衡响应分析,找到了旋梭轴系在工作转速内失稳的原因;最后,研究了旋梭轴径、支承位置、支承刚度、阻尼系数、轴向预紧力对旋梭轴系稳定性的影响,确定了满足使用工况的旋梭轴系结构和支承刚度范围。研究结果表明：缝纫机工作转速内有1个临界转速,影响了旋梭轴系的稳定性;增大轴径对提升临界转速的效果不明显;增加一个支承点,轴承刚度高于1 000 N/mm,轴套支承刚度高于100 N/mm,阻尼系数小于0.1,轴向预紧力小于100 N;旋梭轴系在工作转速内可以稳定运行。     

考虑激振频率的可倾瓦推力轴承动特性理论与试验研究

为了研究激振频率对可倾瓦推力轴承动特性的影响,提出考虑激振频率的动特性建模方法和试验方法。依据可倾瓦轴承刚度和阻尼定义,将激振频率引入可倾瓦推力轴承动特性计算过程,通过建立轴向扰动下的膜厚方程、雷诺方程及瓦块运动方程,推导出包含激振频率的可倾瓦推力轴承动特性数学模型,计算分析刚度和阻尼随扰动频率(激振频率与主轴转频的比值)、转速及载荷的变化规律;采用脉冲激振法在可倾瓦推力轴承试验台进行动特性试验,得到不同激振频率、转速及载荷条件下刚度、阻尼的试验结果,并和相应的理论计算值进行对比分析。结果表明：当扰动频率较小时,可倾瓦推力轴承刚度随其增加而逐步增大,阻尼随其增加而逐步减小;当扰动频率增加到一定程度后,其刚度和阻尼逐步趋于稳定。此外,转速和载荷对其刚度和阻尼随扰动频率的变化幅度基本无影响。     

基于叶轮转子系统下的干气密封轴向振动分析*

为探究基于叶轮转子系统下干气密封轴向振动特性,基于干气密封结构特性,建立叶轮转子-轴承-干气密封系统轴向振动模型,采用待定系数法进行求解,推导得出静环轴向振动幅值表达式;建立叶轮转子-轴承-干气密封系统几何模型,运用ANSYS Workbench软件进行模拟仿真计算,分析气膜刚度和激振力对轴向振动的影响。结果表明:气膜刚度对动、静环振动幅值的影响不大;动、静环振动频率相同、振动幅值相同,说明动、静环的追随性高,其间隙稳定,从而保证干气密封的稳定运行;动、静环位振动幅值与激振力成正比关系,说明激振力严重影响干气密封的稳定性,为提高干气密封的稳定性,应平衡好叶轮的轴向激振力。     

密封和内阻尼对火箭发动机液氢涡轮泵转子系统动力稳定性的影响

考虑内阻尼的Timoshenko梁一轴有限元离散化转轴,用Muszynska密封力模型描述非线性密封流体激振力,建立实际火箭发动机液氢涡轮泵转子系统的非线性有限元模型。结合已有试验数据,结合打靶法和Floquet 理论研究该系统在刚性支承和柔性支承两种工况下密封和内阻尼对系统稳定性的影响。分析轴承阻尼、轴向雷诺数以及密封各参数在两种支承下对系统临界失稳角速度的影响。     

On the Relation of Load to Average Gap in the Contact Between Surfaces with Longitudinal Roughness

A computer simulation model for the contact between longitudinally-oriented rough surfaces has been formulated. This model closely duplicates the actual surf ace contact deformation behavior by taking into account the elastic interactions between the asperities. There were no assumptions made about the shapes, or any deformation behavior of the asperities, except for their obeying the laws of elasticity. The plastic deformations on the high asperity peaks were taken into account by setting a ceiling on their contact pressures at the material hardness value. The simulations used real surface profiles which were digitized from unworn circumferentially ground steel surfaces. Each pair of these profiles was mathematically combined to form an equivalent rough profile pressing against an infinitely rigid flat and having the appropriately adjusted elastic modulus. A total of 28 different pairs of profiles were used in the simulations. Each contacting pair was subjected to 30 different load levels and the local contact pressures and deformations were calculated. The contact simulations yielded some important mathematical relationships between parameters, such as the real area of contact, average gap, and average asperity load through statistical curve fitting. Two analytical functions were generated to relate the average load to average gap and the real area of contact to load.     

三绕组变压器的双绕组等效建模及在Matpower中的应用

针对实际电网存在着大量的三绕组变压器,但国际上一些著名商业软件,如BPA仿真软件、Matpower这一权威潮流计算开源软件,均只提供双绕组变压器模型,限制了其在具有三绕组变压器的电力系统中的应用的问题,潮流计算是自主开发的电力系统各种应用软件的核心模块,因此依托国际权威开源程序进行二次开发,是一种较好的选择。对Matpower要求的数据格式进行了归纳,对变压器的一般的等值电路及带理想变压器的等值电路和带标幺值的等值电路进行了分析研究,提出了三绕组变压器转换为双绕组等效模型的建模方法,使得原先只适应双绕组变压器的潮流计算软件可以适用于三绕组变压器电网的潮流计算;最后以Matpower软件为例进行了案例计算,并用PSASP仿真软件进行对比验证。研究结果证明,所提出的建模方法是有效的。     

电站锅炉模糊风险评价方法研究与应用

针对电站锅炉风险等级评价问题,将模糊综合评价技术应用到电站锅炉风险等级评价中。开展了电站锅炉失效影响因素及模糊评价因素的重要程度分析,建立了一套科学合理适于在线评价的电站锅炉风险评价体系,提出了模糊综合评价技术与改进的模糊层次分析法相结合的模糊风险评价方法,利用改进的模糊层次分析法计算了指标体系中各层指标权重。对某一台电站锅炉的实际运行工况影响子因素进行了模糊风险评价,采用模糊合成算子进行模糊综合运算得到电了站锅炉运行工况影响子因素的评价向量。研究结果表明:电站锅炉的运行工况影响子因素的风险评价等级为第6级,失效可能性等级为小,该电站锅炉运行工况良好。     

交通荷载作用下桥梁结构参数识别方法

应用动力节点加载法,将作用在桥梁上的交通荷载转化为等效节点荷载,再用两步构造法识别结构物理参数.第1步,用Newmark-β方法变换结构运动方程,并用结构的加速度响应求得变换空间内的位移、速度和加速度响应;第2步,基于最小二乘原理,构造出变换空间内求解结构参数的递推式,进行结构物理参数识别.数值模拟结果表明,在交通荷载作用下,该方法能够快速、准确地进行桥梁结构参数识别.     

Quantum Cooperative Robotics and Autonomy

The intersection of Quantum Technologies and Robotics Autonomy is explored in the present paper.The two areas are brought together in establishing an interdisci...     

考虑进油孔有限长滑动轴承油膜力的近似解析解

针对具有进油孔的有限长滑动轴承油膜力求解问题,采用变分原理和分离变量法,求得了有限长滑动轴承油膜压力分布的近似解析表达式。将油膜压力分布的近似解析表达式在油膜存在区域上进行积分,即得到了油膜力。将提出的计算有限长滑动轴承油膜力方法与无限长轴承模型、有限元方法的计算结果进行了比较,发现了提出的方法与有限元方法的计算结果很接近。最后,研究了进油孔位置和进油压力对油膜存在区域、油膜力等的影响,研究结果表明进油孔位置和进油压力对油膜存在区域和油膜力有较大的影响。     

RLS and LMS blind adaptive multi-user detection method and comparison in acoustic communication

RLS and LMS blind adaptive multi-user detection algorithm and multi-user detector was proposed to solve the problem of multi-user signal detection problem encountered in underwater acoustic communication networks.In simulation analysis,RLS and the LMS blind adaptive multi-user detector were designed and tested for synchronous and asynchronous multi-user communication process.The results of SIR comparison and MMSE comparison show that,both of the two methods can realize blind adaptive detection when any user change in multi-user communication,during this process,the training communication sequences are not needed.The RLS algorithm has about 5 dB higher in SIR compared with LMS algorithm,and the convergence velocity of RLS algorithm is also higher than LMS algorithm when the communication users change.RLS algorithm has better ability in multi-user detection than that of LMS algorithm,and it has great attraction and guiding significance for solving the problem of multiple access interference(MAI) in multi-user communication.     

Robust Impedance Control of Robots Using an Adaptive Interaction Force Observer

For robot interaction control,the interaction force between the robot and the manipulated object or environment should be monitored.Impedance control is a type ...     

Research on key techniques of expendable conductivity temperature depth measuring system

This paper analysis the developing of expendable conductivity temperature depth measuring system(XCTD)and introduce its principle of measuring about temperature,salinity and depth of ocean.Some key techniques are put forward.According to the real needs of XCTD,conductivity sensor with high sensitivity is designed by principle of electromagnetic induce,the ocean conductivity from induced electromotive force has been calculated.Adding temperature correction circuit would help to reduce error of conductivity measurement because of sharply changing temperature.Advanced temperature measuring circuit of high precision and the constant current source is used to weaken effect of self-heating of resistance and fluctuation of the source.On respect of remote data transmission,LVDS is a good choice for the purpose of guarantee the quality of data transmitted and the transmission distance is reaching to thousand meters in the seawater.Modular programming method is also brought into this research aimed at improve the stability,reliability and maintainability of the whole measuring system.In February,2015,the trials in South China Sea demonstrate that the developed XCTD realize effective measurement at a speed of 6 knots and detection depth at 800 m.The consistency coefficient of the acquired data is greater than 0.99 and the success rate of probe launching is above 90%.     

CHARACTERISTCS OF FLUID FILM IN OPTIMIZED SPIRAL GROOVE MECHANICAL SEAL

In order to investigate the sealing performance variation resulted from the thermal deformation of the end faces, the equations to calculate the fluid film pressure distribution, the bearing force and the leakage rate are derived, for the fluid film both in parallel gap and in wedgy gap. The geometrical parameters of the sealing members are optimized by means of heat transfer analysis and complex method. The analysis results indicate that the shallow spiral grooves can generate hydrodynamic pressure while the rotating ring rotates and the bearing force of the fluid film in spiral groove end faces is much larger than that in the flat end faces. The deformation increases the bearing force of the fluid film in flat end faces, but it decreases the hydrodynamic pressure of the fluid film in spiral groove end faces. The gap dimensions which determine the characteristics of the fluid film is obtained by coupling analysis of the frictional heat and the thermal deformation in consideration of the equilibrium condition of the bearing force and the closing force. For different gap dimensions, the relationship between the closing force and the leakage rate is also investigated, based on which the leakage rate can be controlled by adjusting the closing force.