基于预前控制异步电机直接转矩控制方案的研究

在传统异步电动机直接转矩控制方案中，由于负载的变化规律不可预测，因此其常会带来较大的开关频率的变化，为此提出了一种基于预前控制的异步电动机直接转矩控制的方法。该方法依据前一个周期的磁链和转矩误差，对下一个开关周期所应施加到异步电动机的定子电压矢量进行预测，然后借助空间矢量PWM的方法，合成此开关电压矢量。样机实验结果表明，该方案不但能维持逆变器的开关频率基本恒定，而且还具有比传统直接转矩控制更为优良的动静态特性。     

利用弧形光栅尺测量大型转轴扭矩的原理研究

利用弧形光栅尺的旋转微位移测量功能,组建一组测量体系,用于测量巨型转轴的扭矩。采用四组相同的弧形光栅尺同时测量两截面的相对转角,通过多点测量实现误差均化,得出了消除转轴直径对测量影响的公式,使仪器的环境适应能力得到了极大地提高。根据不同的工作情况,提出了相应的动态测量扭矩的计算方程。实现了大型机械设备主传动的动力监测,为设备自动化、智能化奠定了基础。     

The driving torque of a rotating levitated cylindrical permanent magnet above a superconductor

Due to the Meissner effect, a permanent magnet is levitated, when released above a high temperature superconductor. When there is an inhomogeneous temperature field around the magnet, the magnet might start to oscillate with increasing amplitude until it remains in a continuous rotation. A mathematical model for the described effect is presented which couples heat transfer and electromagnetic forces with the equation of motion, yielding to a multiphysics task. In a detailed analysis it is found, that the torque which drives the rotation of the magnet, is explicitly given in terms of Bessel functions and the Fourier coefficients of order zero and one of the temperature field of the surrounding air.     

交流电机变频调速中矢量控制与直接转矩控制的研究

随着交流电机在现代社会生产中的广泛应用,三相交流异步交流调速控制系统成为研究的热点,各种各样的变频调速方案相继出现,作为当前两种主要的交流电机变频控制方法,矢量控制和直接转机控制在实际中得到广泛的应用。本文以矢量控制与直接转矩控制比较为核心,对二者的控制原理、特性以及应用进行了分析与比较。同时,在分析的直接转矩控制原理的基础上,基于Simulink环境下对直接转矩控制系统进行仿真模型的搭建,并得到相应的仿真图象。     

交流电机高性能转矩控制教学内容设计

交流电机高性能转矩控制是交流调速课程讲授的核心,也是学生学习的难点。本文从交流电机产生转矩的物理本质出发,结合转矩和磁链解耦控制特征,全面阐述了交流电机中高性能转矩控制数学模型;基于这些模型分析了当前两种典型的交流电动机高性能转矩控制系统结构,最后给出实验结果。课堂教学结果显示,本文提出的教学内容设计能够使得学生迅速抓住交流电机高性能转矩控制本质,取得了很好的教学效果。     

节能灯灯头扭矩测试仪器的改进

针对目前广泛使用的节能灯灯头扭矩测试仪器采用人手直接施加扭矩的缺陷进行改进。     

智能视频监控中目标跟踪的研究与实现

目标跟踪是智能监控领域的关键技术,本文主要是研究实现这一关键技术。提出一种融合运动目标的面积和矩特征进行匹配的算法,并结合运动估计算法对下一时刻目标最可能存在的方位进行预测,实现了对运动目标的跟踪。实验表明该算法能够准确跟踪运动目标,在一定程度上满足了实时性的要求。     

Magnetization switching modes in nanopillar spin valve under the external field

The current-induced magnetic switching is studied in Co/Cu/Co nanopillar with an in-plane magnetization traversed under the perpendicular-to-plane external field.Magnetization switching is found to take place when the current density exceeds a threshold.By analyzing precessional trajectories,evolutions of domain walls and magnetization switching times under the perpendicular magnetic field,there are two different magnetization switching modes:nucleation and domain wall motion reversal;uniform magnetization ...     

高频主轴驱动器RS51在磨床上的应用

随着高速切削、精密加工、快速制造等先进制造技术的发展,高频电主轴及其驱动装置成了制造业实现数字化的关键,是决定高速、高精、多轴联动的高档数控机床性能、可靠性、成本价格的关键因素     

Relaxation Dynamics and Magnetic Anisotropy in a Low‐Symmetry DyIII Complex

The magnetic behaviour of a Dy(LH)₃ complex (LH^? is the anion of 2‐hydroxy‐N′‐[(E)‐(2‐hydroxy‐3‐methoxyphenyl)methylidene]benzhydrazide) was analysed in depth from both theoretical and experimental points of view. Cantilever torque magnetometry indicated that the complex has Ising‐type anisotropy, and provided two possible directions for the easy axis of anisotropy due to the presence of two magnetically non‐equivalent molecules in the crystal. Ab initio calculations confirmed the strong Ising‐type anisotropy and disentangled the two possible orientations. The computed results obtained by using ab initio calculations were then used to rationalise the composite dynamic behaviour observed for both pure Dy^III phase and Y^III diluted phase, which showed two different relaxation channels in zero and non‐zero static magnetic fields. In particular, we showed that the relaxation behaviour at the higher temperature range can be correctly reproduced by using a master matrix approach, which suggests that Orbach relaxation is occurring through a second excited doublet.