Radial Force Analytic Modeling for a Novel Bearingless Switched Reluctance Motor When Considering Rotor Eccentricity

Abstract—Analytic modeling of radial forces is proposed for the novel bearingless switched reluctance motor, where the rotor eccentricity is taken into account. The novel bearingless switched reluctance motor's model is never disclosed, even though there are many advantages, such as fewer suspension windings and simpler control circuit and algorithm, when compared to the conventional bearingless switched reluctance motor. The analytic model of radial forces is very important to achieve this new bearingless switched reluctance motor's suspension control. The rotor eccentricity is a key cause to affect the radial forces. This article calculates the air-gap permeances through considering rotor eccentricity. The self-inductance and mutual-inductance expressions of the motor torque windings and the suspension windings are derived by using the magnetic equivalent circuit method. The derived radial force model discloses the effects of winding currents, rotor position angle, and rotor eccentricity displacement. The finite-element analysis based results verify the built model.     

感应型无轴承电机磁悬浮力解析模型及其反馈控制

由于负载、干扰和径向位移检测误差，无轴承电机悬浮运行时定、转子中心并不重合，产生偏心，影响了其稳定悬浮控制性能。该文从运行原理出发，建立了计及定、转子定位偏心的感应型无轴承电机磁悬浮力的较精确解析模型，采用电机电磁场分析软件ANSOFT验证了它的精度。应用这个模型实现了悬浮力的实时观测，在传统气隙磁场定向矢量控制系统基础上添加了悬浮力的闭环控制，有效地提高了感应型无轴承电机稳定悬浮运行的动、静态性能。     

感应型无轴承电动机的模糊神经网络控制系统

由于负载、干扰和径向位移检测误差,无轴承电动机悬浮运行时定、转子中心并不重合,产生偏心,影响了其稳定悬浮控制性能。从运行原理出发,建立了感应型无轴承电动机磁悬浮力的解析模型,并采用模糊神经网络对其进行控制,有效地提高了感应型无轴承电动机稳定悬浮运行的动、静态性能。     

Torque and suspension force in a bearingless switched reluctance motor

Bearingless switched reluctance motors, which can control rotor radial positions with magnetic force, have been proposed. The bearingless switched reluctance motors are characterized by integration of switched reluctance motors and magnetic bearings. These motors have two kinds of stator windings composed of motor main windings and suspension windings in the same stator in order to produce suspension force that can realize rotor shaft suspension without mechanical contacts or lubrication. For successful stable operation, accurate theoretical formulas of instantaneous torque and suspension force are necessary to a rotational speed controller and a rotor radial position controller. This paper derives the theoretical formulas of the instantaneous torque and the suspension force from an assumption of simple permeance distribution. This derivation process makes an assumption that fringing fluxes are distributed on elliptical lines. It is shown with experimental results that the derived theoretical formulas are very accurate in terms of practical application. © 2006 Wiley Periodicals, Inc. Electr Eng Jpn, 157(2): 72–82, 2006; Published online in Wiley InterScience ( www.interscience.wiley.com ). DOI 10.1002/eej.20157     

无轴承永磁同步电机转子径向位移估算策略

无轴承永磁同步电机实现平稳悬浮的关键是对转子径向位置偏移量进行闭环控制。通常无轴承永磁同步电机高性能悬浮运行时都依赖于位移传感器,但由此破坏了电机结构的坚固性、阻碍了电机的低成本实用化等,需要新的位移估算策略替代传统的机械位移传感器。通过建立无轴承永磁同步电机悬浮、转矩两套绕组的磁链、电压和电流状态方程,构建最小二乘法电机转子位移估算模型,进一步提出基于普通最小二乘法和遗忘因子最小二乘法的混合加权最小二乘法估算策略。通过采样电机两套绕组电压和电流,应用混合加权最小二乘算法对转子位移进行在线辨识。仿真及实验证实该方法能实现无传感器工况下电机转子位移的有效估算,电机悬浮和转动系统性能较好。     

永磁无刷直流电动机场路耦合运动时步有限元分析

提出一种适用于永磁无刷直流电动机的场路耦合运动时步有限元分析方法，解决了电机在非正弦供电时的场路耦合分析问题。电路中考虑了开关元件换流重叠过程和绕组中点的电位波动。给出了控制电路与电磁场方程耦合的时步有限元单元分析方法，采用改进的有限元运动边界处理方法--插值运动边界法解决转子运动问题。应用上述模型对1台无刷直流电动机的进行分析，计算结果和样机的实测波形吻合。该方法也适用于其他非正弦供电电机的场路耦合有限元分析。     

基于转子偏心坐标系的无轴承永磁薄片电机径向悬浮力模型

针对无轴承永磁薄片电机(BPMSM)运行时转子悬浮不够稳定的问题,研究了影响BPMSM转子悬浮性能的主要因素,即转子径向悬浮力模型。依据位移补偿控制理论和角坐标系的概念,建立了新的转子偏心坐标系。在转子偏心坐标系下,基于麦克斯韦应力张量法,利用积分和三角变换推导了转子径向悬浮力模型,并设计悬浮力绕组电流直接控制系统。建立电机的有限元模型,通过对比径向悬浮力的有限元分析结果与数学模型计算结果,验证了所推导数学模型的正确性与准确性。     

无轴承异步电机转子偏心补偿的研究

针对无轴承异步电机转子偏,心工作问题,对其转子偏心时的转子受力情况进行了分析,并以此为基础,应用径向力反馈控制来补偿转子偏心的非线性影响。结果表明,径向力反馈控制有效地提高了无轴承异步电机系统的悬浮精度.     

基于等效磁网络法的混合励磁双定子磁悬浮开关磁阻电机建模研究

提出了一种混合励磁双定子磁悬浮开关磁阻电机(BSRM)的等效磁网络模型,此模型可以分析电机悬浮和转矩绕组的磁链、电感及悬浮力和转矩等静态特性。等效磁网络法(EMN)不仅能保证一定的精度,而且比有限元法（FEM）节省时间。基于一种24/16/8极混合励磁双定子BSRM建立EMN模型,推算出电机定转子齿部、轭部以及气隙磁导的计算公式。建立矩阵方程,求解出各部分的磁通密度,进而求出悬浮和转矩绕组的磁链、电感以及悬浮力和转矩特性,和FEM求解的结果进行对比。可以发现EMN模型求解出的电磁特性和FEM分析的结果吻合效果很好,进一步证明了所建模型的有效性。     

Analysis of no-load characteristics of a bearingless inductionmotor

This paper presents the design and analysis of a bearingless squirrel cage induction motor. There are two sets of stator windings. The main winding is a four-pole arrangement, while the control winding is a two-pole type. The latter is utilized to produce radial forces on the rotor shaft. The two-pole winding currents are regulated by radial position sensors and control strategies in order to maintain the rotor shaft position near the air gap center. The voltage and current relationships of the two-pole windings were derived from the machine inductance model and equivalent circuits. The influences of the secondary rotor circuits were also taken into account. The theoretical values of current, voltage, and radial force were compared with experimental results. It was found that the two-pole windings need only about 2 percent of the voltampere (VA) requirements of the main motor windings     

无轴承电机悬浮控制系统的设计

无轴承电机是利用磁悬浮轴承和交流电机结构的相似性,将产生磁悬浮力的磁悬浮轴承绕组置入电机定子,省去了专门的磁悬浮轴承。通过对转矩绕组和悬浮力绕组的解耦控制,使电机的转子同时具有产生转矩和自悬浮的功能。无轴承电机能够实现高速、无摩擦等优良性能,是当前研究的热点之一,无轴承电机悬浮控制系统设计是该研究的关键。介绍了无轴承电机悬浮控制的基本原理,设计出了基于转矩绕组转子磁场定向的悬浮控制系统。     

单绕组无轴承永磁薄片电机的原理和实现

研究了一种单绕组无轴承永磁薄片电机的工作原理和结构设计。摒弃了传统无轴承电机的双绕组结构,采用一套绕组实现电机转子悬浮和旋转。推导了单绕组无轴承永磁薄片电机径向悬浮力的数学模型,给出相应的控制策略和功率系统设计方案。制作了实验样机,并做了空载和负载实验。实验样机调试结果表明,单绕组无轴承永磁薄片电机成功实现了包括径向、轴向和扭转等方向的5自由度全悬浮。     

Magnetic suspension force in an induction bearingless motor with a squirrel cage rotor

Theoretical equations of magnetic force in an induction bearingless motor have been reported. In the bearing‐less motor, both 4‐pole and 2‐pole windings are stored in stator slots for torque and suspension force generation. In the analysis, squirrel cage rotor currents are considered. These currents are induced by both torque and suspension winding currents. Inductance matrix is represented by four sets of three‐phase windings, thus a 12×12 matrix is constructed. A simplification and reasonable assumptions are introduced to obtain understandable expressions for suspension force and torque representation. The rotor flux linkages in an induction bearingless motor are derived, and a simulation model of suspension force is then constructed. It is shown that the response and the phase of suspension force are delayed in the case of cage rotors. © 2007 Wiley Periodicals, Inc. Electr Eng Jpn, 159(3): 77–87, 2007; Published online in Wiley InterScience ( www.interscience.wiley.com ). DOI 10.1002/eej.20340     

新型无轴承开关磁阻电机双相导通数学模型

针对传统无轴承开关磁阻电机数学模型单相电流导通模式的局限性,提出了一种适用于单、双相导通的无轴承开关磁阻电机数学模型.在建立两相电流导通的等效磁路模型基础上,确定电感矩阵,推导出两相电流导通的径向悬浮力和电磁转矩的表达式.基于该数学模型的双相电流导通模式极大程度地拓宽了无轴承开关磁阻电机的工作区域,增加了其承受径向负载的能力.利用磁场分析法验证了该数学模型的正确性和优良的工作特性.     

Analysis and characteristics of a permanent magnet-type bearingless motor

Super-high-speed and high-power electric machines are required for turbomolecular pumps and spindle drives. High rotational speed and high-power drives can be achieved with bearingless motors. In this paper, a bearingless motor with principles of permanent magnet-type synchronous motors is proposed. High-power factor and high efficiency can be expected in permanent magnet-type bearingless motors. The proposed bearingless motor is a 4-pole permanent magnet synchronous motor, in which additional 2-pole windings are wound together with 4-pole motor windings in stator slots. With currents of 2-pole windings, radial magnetic forces are produced to support a rotor shaft. Principles of radial force production of surface-mounted permanent magnet bearingless motors are analyzed mathematically. The relationships between radial forces and the permanent magnet thickness were derived. From these relationships, the optimal permanent magnet thickness to produce radial forces efficiently is found. A test machine was built to confirm the relationships of radial forces, currents and voltages.     

新型交替极无轴承永磁电机的原理与实现

传统永磁型无轴承电机悬浮力和转矩控制存在耦合，该文对一种新型交替极转子结构的无轴承永磁电机的磁悬浮原理进行了深入分析和数学建模，指出该类型电机所具有的独特的悬浮控制和转矩控制解耦的特点，并构建了无轴承交替极永磁电机的实时控制系统。实验结果表明实现了该新型无轴承永磁电机的动、静态稳定悬浮，验证了悬浮与转矩控制解耦的特性。     

无轴承同步磁阻电机最小二乘法转子位移自检测策略

位移传感器是无轴承同步磁阻电机悬浮运行时转子位置闭环可控的关键部件,但装配多个位移传感器阻碍了无轴承同步磁阻电机的低成本实用化和结构简单化,由此提出最小二乘法转子位移自检测（无传感器）策略。基于电机悬浮绕组和转矩绕组的磁链、电压和电流状态方程,重构最小二乘法转子位移检测模型,通过采样两套绕组电压和电流,应用最小二乘递推算法对转子位移进行在线辨识。仿真实验表明,该方法能准确实现无传感器工况下转子位移自检测,检测系统有较强的负载扰动适应性。     

永磁型无轴承电机无径向位移传感器运行研究

在分析悬浮绕组电感与转子径向位移线性关系的基础上,针对永磁型无轴承电机无径向位移传感器运行的需要,分析了一种基于悬浮绕组高频信号注入的转子径向位移估算自检测方法,讨论了利用高频信号注入、悬浮绕组差分电压提取及转子径向位移跟踪观测器设计等位移检测原理和实现技术,并应用这种位移检测方法建立了永磁型无轴承电机无径向位移传感器控制系统.仿真研究表明,该位移自检测方法能在永磁型无轴承电机全速范围内准确地观测出转子的径向位移,实现无径向位移传感器方式的稳定悬浮运行.     

内插式永磁无轴承电机转子位置/位移综合自检测

为实现无轴承电机的低成本与实用化，解决运行控制中电机转子位置/速度及径向位移的检测，提出了一种基于脉动高频电压信号注入法的转子位置/位移综合自检测方法。通过从转矩绕组注入脉动高频电压信号，利用电机空间凸极效应和转矩绕组与悬浮绕组间的互感特性，同时实现对转子位置/速度和径向位移的有效观测。电磁场分析结果表明，该方法可实现位移检测信号在水平、垂直方向的解耦以及转子位置和位移检测信号间的解耦。应用该检测方法构建了内插式永磁型无轴承电机无传感器运行的矢量控制系统，系统仿真运行表明，该自检测方法能在全速范围内准确观测出转子的位置/速度和位移，并能在大负载扰动条件下实现无传感器方式的稳定悬浮运行。     

基于有限元法的磁悬浮开关磁阻电机数学模型

当电机高速运行时，为避免机械磨损，采用电磁力进行悬浮支撑，而磁轴承占用轴向空间，限制临界转速。磁悬浮开关磁阻电机利用电机定子与轴承机械结构的相似性，在原有的电机定子绕组上附加一套径向力绕组，通过一定的控制策略，同时实现电机的旋转和悬浮。该文在利用有限元软件Ansoft/ Maxwell 2D分析磁悬浮开关磁阻电机磁场的基础上，结合等效磁回路法并根据虚位移定理，推导出磁悬浮开关磁阻电机在考虑a、b轴方向径向偏移及其耦合时的径向力和转矩的数学模型，并用有限元分析结果验证了该模型的正确性和有效性。