基于阻尼粒子群优化的地磁场测量误差补偿

针对三轴磁力仪在磁场测量过程中的磁干扰问题,提出了基于阻尼粒子群优化算法的磁测误差补偿方法。建立了磁力仪误差和载体磁干扰的一体化误差补偿模型,分别采用阻尼粒子群算法和Two-step方法对非线性观测模型进行参数估计。以质子磁力仪数据作为真值,借助无磁转台充分连续采样,实验结果显示,阻尼粒子群算法对于磁场测量误差具有良好的抑制作用。补偿后,由阻尼粒子群算法和Two-step方法得到的均方根误差分别由1 025.7降至60.304 4、581 n T。结果表明,阻尼粒子群算法取得了更好的补偿效果,补偿精度提高了至少一个数量级,为磁场测量误差提供了一种非常有效的补偿方法。     

基于粒子群优化算法的航天器惯性参数辨识

在地面上精确测量航天器的惯性参数是困难的,并且由于燃料的消耗、航天器的交会对接、载荷及姿态的变化等因素将会使航天器的惯性参数在轨发生变化。因而航天器的控制系统、状态估计系统将会受到航天器惯性参数变化的影响。在轨辨识出航天器的惯性参数,可以为更加优化、实时的控制航天器服务。文中提出了一种基于粒子群优化算法的航天器惯性参数辨识算法。建立了引入带有模型误差以及由于航天器惯性参数变化引起的误差的航天器姿态运动学与动力学模型,基于模型误差最小准则建立目标函数,利用改进的粒子群优化算法对模型误差进行实时估计,从而实现对航天器惯性参数的辨识,并将其应用到航天器的姿态控制中,并通过仿真实验证明了该算法的有效性以及实用性。     

果蝇优化算法和粒子群优化算法的应用对比

参数优化一直是控制系统重要的一个环节,现在常用的优化算法有蚁群算法、遗传算法、粒子群优化算法。然而现在这些算法普遍存在鲁棒性差、陷入局部最优等缺点。果蝇优化算法作为一种较新的群体优化算法与粒子群有颇多的相似之处。本文以水轮机组调速系统PI控制参数为优化对象,分别以粒子群优化算法和果蝇优化算法进行参数优化,通过分析二者的优化过程与结果,对比了两种优化算法的优缺点,证明了果蝇优化算法的可行性。     

基于改进粒子群算法的数控加工参数优化研究

为优化数控加工参数,提高数控机床加工性能,研究改进粒子群算法的数控加工参数优化方法,设置最低生产成本以及最高生产率为数控加工参数的优化目标,利用协调系数将多目标优化问题转化为单目标优化问题建立目标函数,设置切削速度、进给量约束、切削进给力、切削功率、切削转矩约束、表面粗糙度要求为约束条件,采用惯性权重值适应性递减方法改进粒子群算法,令惯性权重随粒子群进化适应性提升,采用改进粒子群算法快速寻找数控加工参数目标函数最优值,实现数控加工参数优化.实例分析结果表明,该方法可有效优化数控加工参数,满足实际加工需求,优化后的实验数控机床加工性能佳.     

基于改进粒子群算法的数控加工参数优化研究

为优化数控加工参数,提高数控机床加工性能,研究改进粒子群算法的数控加工参数优化方法,设置最低生产成本以及最高生产率为数控加工参数的优化目标,利用协调系数将多目标优化问题转化为单目标优化问题建立目标函数,设置切削速度、进给量约束、切削进给力、切削功率、切削转矩约束、表面粗糙度要求为约束条件,采用惯性权重值适应性递减方法改进粒子群算法,令惯性权重随粒子群进化适应性提升,采用改进粒子群算法快速寻找数控加工参数目标函数最优值,实现数控加工参数优化.实例分析结果表明,该方法可有效优化数控加工参数,满足实际加工需求,优化后的实验数控机床加工性能佳.     

基于粒子群算法的铣削参数优化

针对加工中心环境下铣削加工切削参数的优化选择问题,通过考虑机床加工、工件和刀具的实际约束,建立以最大生产率为目标函数的铣削参数数学模型,采用粒子群优化算法对铣削参数进行了寻优并进行了实例验证,结果表明粒子群算法优化铣削参数可以缩短加工时间,提高生产率.     

基于粒子群算法的加工参数多目标优化技术研究

在数控加工中,为了尽可能提高生产效率和降低生产成本,采用粒子群优化算法对加工参数进行多目标优化。以切削速度、切削宽度和每齿进给量为决策变量,以加工时间和成本为目标函数,并以机床性能、刀具参数、工件质量等为约束条件,建立优化模型。采用罚函数法对约束条件进行处理,将多目标问题转化为单目标优化问题进行求解。为解决粒子群优化算法优化效果受参数影响较大的问题,提出了参数自适应协同粒子群优化算法(WCVPSO),算法参数按照一定规律变化,提高了优化算法的精度和收敛速度。实际加工试验表明,提出的优化方法提高了加工效率,降低了加工成本。     

粒子群优化算法在求解线性规划方程中的效率研究

提出了使用粒子群优化算法求解线性规划方程的方法,并对粒子群优化算法设置不同的参数求解线性规划方程,研究粒子群优化算法在求解线性规划方程时所表现出的效率,实验表明,粒子群优化算法在求解线性规划方程时当设置参数φ1,=2.8,φ2=1.3,粒子人口数选择40时该算法表现出较高的效率.     

PID控制器的量子粒子群多目标优化设计

智能算法如粒子群算法已被应用于PID控制器的参数优化,以弥补传统优化方法容易产生振荡和较大超调量的不足,但是粒子群算法存在易于早熟的缺点,在分析量子粒子群算法的基础上,提出了使用量子粒子群算法优化PID控制器的参数.为了兼顾控制系统的各项性能指标,根据控制器的实际要求对各项指标进行加权作为算法的目标函数,对PID控制器进行多目标寻优.通过2个传递函数实例,分别使用Z-N、粒子群算法和量子粒子群算法进行了PID控制器参数优化设计,并对结果进行了分析.     

粒子群优化人工神经网络在高速铣削力建模中的应用

将粒子群优化人工神经网络理论应用于高速铣削力的建模研究中.采用粒子群算法与反向传播算法相结合的方法,对反向传播神经网络模型进行优化.用粒子群算法训练网络参数,直到误差趋于一稳定值,然后用优化的权值进行反向传播算法运算,以实现高速铣削力的预测.充分发挥了粒子群算法的全局寻优能力和反向传播算法的局部搜索优势.仿真结果表明,与其他几种反向传播算法相比较,粒子群算法与反向传播算法的学习算法训练的神经网络,不仅训练时间明显缩短,而且其预报精度也得到了较大的提高,能够有效地建立铣削力模型,并对铣削力进行准确的预测.     

磁悬浮电主轴单元径向轴承的磁场分析

介绍了磁悬浮电主轴单元的工作原理,以5.5kW电主轴单元为例,利用ANSYS软件对其径向磁轴承磁场进行了有限元分析.找出其系统磁场分布的变化规律和影响因素.分析表明:在主轴正常悬浮且单边气隙值取0.3±0.004mm,主轴支承处轴颈圆度取0.003mm,径向磁轴承磁极内圈圆度取0.007mm时,磁路磁漏不影响控制系统的性能,主轴实际中心线距理想位置的最大偏移量为0.0025mm,可满足精密机床主轴径向旋转精度性能要求.研究结果为磁悬浮电主轴单元的径向支承结构的优化设计提供了理论依据.     

磁悬浮轴承结构与磁路分析

从受控自由度数、磁力产生方式、磁极结构形式、控制电流性质等方面对磁悬浮轴承进行了分类与比较.针对各种典型磁悬浮轴承给出了其结构与磁路示意图,并进行了定性分析与比较,最后分析了磁悬浮轴承结构与磁路方面研究与发展方向.     

Rotating magnetic beacons magnetic field strength size in SAGD

Rotation magnetic beacons magnetic field strength is very important to drill parallel horizontal twin wells in steam assisted gravity drainage (SAGD). This paper analyzes a small magnet with a diameter of 25.4 mm. At each end, there is a length of 12.6 mm with permanent magnet, and in the middle, there is a length of 78mm with magnetic materials. The magnetic field strength generated by the magnetic material of 1J12, 1J50, and 1J79 is analyzed, respectively. ANSOFT software is used to simulate the magnetic field strength generated by different magnetic materials above, which also be tested through experimental methods. The comparison of the simulation and experimental results show that experimental and simulation results are basically consistent, and the results can meet the specific requirements of engineering applications.     

磁悬浮陀螺飞轮用隐式洛伦兹力磁轴承

针对磁悬浮陀螺飞轮用显式洛伦兹力磁轴承气隙磁密均匀性差的问题,提出了一种磁钢内置的隐式洛伦兹力磁轴承,并采用三维有限元法对两种方案的气隙磁密进行比较分析。隐式方案的气隙磁密在周向和纵向的变化率分别为0.8%和8.4%,远优于显式方案的15.0%和23.7%。利用磁场分割法对隐式方案的磁阻进行了区域分割,采用积分法精确计算各区域磁阻,建立了磁轴承磁路数学模型,得到了影响偏转电流刚度的关键结构参数,并基于有限元法对隐式方案形状及结构参数进行详细优化。结果表明,在不恶化气隙磁密变化率的前提下,优化前后绕组区域的最大磁密和最小磁密分别从0.404T和0.368T增加至0.464T和0.427T,增幅为14.6%和16.0%。根据优化结果研制了一台隐式洛伦兹力磁轴承,并进行了气隙磁密和偏转电流刚度实验测试,测试结果与设计结果相符,对洛伦兹力磁轴承的设计具有重要意义。     

Tribological properties of Mn-Zn-Fe magnetic fluids under magnetic field

A controllable and variable magnetic field was got by improving the oil cup of a MS-800 four-ball tester. By this improved four-ball tester, the tribological properties of Mn_0.78Zn_0.22Fe₂O₄ magnetic fluid in the magnetic field were tested. The worn surfaces of the steel balls lubricated with 6 wt% Mn_0.78Zn_0.22Fe₂O₄ magnetic fluid under different magnetic fields were observed by using a scanning electron microscope (SEM), while the elemental compositions of the wear scars were analyzed by means of energy dispersive spectrometry (EDS). It was found that the Mn_0.78Zn_0.22Fe₂O₄ nanoparticles had a diameter about 20 nm. Under magnetic field, the 46^# turbine oil containing 6 wt% Mn_0.78Zn_0.22Fe₂O₄ nanoparticles showed much better friction-reducing and anti-wear abilities compared with lubrication without magnetic field. The worn surface, lubricated by 6 wt% Mn_0.78Zn_0.22Fe₂O₄ magnetic fluid lubricated under the effect of magnetic field, is smooth and the plowing is almost disappeared. Moreover, it is found that 22 mT magnetic induction is the optimum magnetic induction. Form theory study we found that under the effect of magnetic field, the bearing capacity increasing with the increasing of magnetic induction. When the eccentricity is small, the side leakage is highly decreased.     

Nuclear magnetic resonance apparatus for pulsed high magnetic fields

A nuclear magnetic resonance apparatus for experiments in pulsed high magnetic fields is described. The magnetic field pulses created together with various magnet coils determine the requirements such an apparatus has to fulfill to be operated successfully in pulsed fields. Independent of the chosen coil it is desirable to operate the entire experiment at the highest possible bandwidth such that a correspondingly large temporal fraction of the magnetic field pulse can be used to probe a given sample. Our apparatus offers a bandwidth of up to 20 MHz and has been tested successfully at the Hochfeld-Magnetlabor Dresden, even in a very fast dual coil magnet that has produced a peak field of 94.2 T. Using a medium-sized single coil with a significantly slower dependence, it is possible to perform advanced multi-pulse nuclear magnetic resonance experiments. As an example we discuss a Carr-Purcell spin echo sequence at a field of 62 T.     

Wear coatings for magnetic thin film magnetic recording heads

Many coatings are in use today for the wear protection of thin film heads. With the trend towards smaller head-media distances, the thickness of the coating has to diminish. In this paper some of these coatings: zirconia, chromium nitride, chromium oxide and diamond (+diamond-like carbon) will be discussed. It will be shown that the film hardness is influenced by the microcrystalline structure, the texture and the film stress. The film hardness shows a good correlation with the reciprocal wear coefficient. The wear resistance of the materials discussed increases in the order: zirconia, chromium nitride, chromium oxide, diamond.     

大承载轴向混合磁力轴承磁性能分析

针对大承载储能飞轮对混合磁力轴承的设计要求,及考虑到混合磁力轴承的对称性,利用ANSOFT软件中的2D模块对其进行建模,并分析了磁力轴承在平衡位置工作点的磁密线分布,磁密分布及漏磁。分析结果表明该磁轴承整个磁路为不饱和,设计合理,以及计算得出漏磁系数相对较大,这是由于磁悬浮轴承整体结构较大,磁路较长,气隙大等原因造成的,该分析为后续的设计提供了可靠的依据。     

助基于磁梯度张量的金属磁记忆检测方法

金属磁记忆是对铁磁材料早期微观损伤及应力集中进行无损检测的有效方法。为提高磁记忆检测的可靠性,充分利用磁记忆信号的矢量信息,将磁梯度张量测量及分析方法引入磁记忆检测中。根据张量缩并分析理论得到了磁记忆信号的磁梯度张量模量,通过求解梯度局部相位的一阶导数得到信号的梯度局部波数,然后分析信号的磁梯度张量模量和梯度局部波数分布特征,得到磁梯度模量和梯度局部波数极值点分别与应力集中边界和中心位置的对应关系。实验结果表明：磁梯度张量方法能够克服检测方向与缺陷夹角变化对测量信号的影响,准确地对应力集中进行判断。     

Thrust bearing using a magnetic fluid lubricant under magnetic fields

This paper describes a thrust bearing using a magnetic fluid lubricant under a magnetic field. The critical pressures of the bearing versus the magnitude of the magnetic flux densities have been investigated experimentally. It is shown that the critical pressures of the proposed bearing are larger than those of the normal lubricated bearing under high speeds.