【作者】 康辉民；

【导师】 陈小安；

【作者基本信息】 重庆大学 ， 机械设计及理论， 2010， 博士

【摘要】 高速电主轴作为现代高速加工技术的核心部件之一,广泛应用于各种数控加工中心和高性能的机床主轴上,具有多变量、非线性、强耦合的特点,其内部的电磁转换与主轴动态输出性能之间存在着非常复杂的相互依存关系。因此,研究如何解释和控制这种相互依赖关系,一直是高速电主轴的研究重点之一。但由于高速电主轴运行时,转速非常高,很难对其进行动态加载测试,且由于国外的技术垄断,国内尚未完全掌握主轴内部的电磁耦合关系与主轴转矩动态输出性能之间的作用规律,有关这一方面的基础资料也十分缺乏,严重影响了高速电主轴技术的深入研究和工程应用。基于上述原因,本课题从高速电主轴的电磁特性出发,提出了一套比较完整的高速电主轴动态性能测试方法,并通过对实验数据与理论分析的对比,取得了以下主要结论:①高速电主轴的动态性能测试包括电气参数测试和机械特性参数的测试。利用测功机并结合三相高频电参数仪等辅助设备,可以获得高速电主轴的输入电压、电流、功率因数以及输出转矩、转速和效率等机械和电气参数;而通过单向加载并同时测试力与力的方向上的位移可以获得高速电主轴的动态刚度值。本文对高速电主轴的转矩和动态刚度的测试均给出了机械式和电磁式两种测试方法,并指出采用测功机测试转矩时,对机械接触式加载需解决测功机与被测电主轴及联轴器的动平衡问题;而用非接触式的电涡流测功机,则需保证加载磁场的稳定性和测功机侧电磁热的及时散发。当对高速电主轴的动态刚度进行测试时,若采用机械式的接触式加载,需有效解决接触磨损所导致的加载失效以及磨屑和摩擦热的散失;而采用电磁加载方式时,除了磁场的稳定性外,还需要考虑磁场对位移传感器的干扰,以防止数据采集失败。②由于高速电主轴输出的机械能取决于高速电主轴气隙磁场中的机电能量转换,所以对磁场的控制,是高速电主轴动态性能研究的重点,涉及到高速电主轴数学模型的建立和控制方式的选取。本文根据高速电主轴的特性建立了两种模型:以高速电主轴电磁参数有效值为基础的稳态数学模型和以过程控制为基础的动态数学模型。前者以控制气隙磁场为目的,当负载变化时,通过控制定子电流来近似控制励磁电流恒定,以满足转子电流与负载的线性关系。该模型适应U/f控制方式,控制方法简单,但控制精度不高。后者分别以控制转子磁链和定子磁链为目的,各自对应矢量控制和直接转矩控制方式。本文重点对矢量控制进行了分析和试验,介绍了无速度传感器矢量控制的原理和该控制方式下高速电主轴的动态性能,论述了当主轴负载变化时,该控制方式控制磁通稳定和抵抗外界干扰时所采用的策略,并进行了实验验证。③当主轴的运行频率下降时,U/f控制下的输入电压应根据高速电主轴额定状态下定子绕组反电动势的大小进行电压补偿,以确保低频下的磁通稳定性;而矢量控制时对励磁电流和转矩电流的控制精度取决于高速电主轴动态数学模型中耦合电压的解耦效果。因此,本文详细论述了在U/f控制时,如何有效进行低频电压补偿的方法,并根据实验数据进行了具体论证;而对矢量控制下交叉耦合电压的解耦途径和效果,进行了对比研究,利用实验验证了高速电主轴在矢量控制下的抗扰动能力和动态速度跟随精度。④应用叠加原理,论述了由谐波磁场产生的谐波磁动势如何通过叠加在主轴磁通上来影响主轴的电磁转矩和输出转速的方式,进而对高速电主轴的静动态性能产生严重影响。并指出各阶谐波影响的程度不同:谐波阶次越低,影响越大;高速电主轴运行的频率越低,需要抑制的谐波次数越大。所以高速电主轴的实际负载运行速度不能过低,这是因为谐波的干扰限制了高速电主轴的实际转速范围。⑤应用电机学和运动学原理,分析了高速电主轴电磁热和摩擦热产生的原因,并根据传热学理论确定了高速电主轴各部分的传热系数和导热热阻,从而建立了高速电主轴的整体动力学热模型。试验结果表明,转速越高,主轴的温升越大;而气压和润滑油量对主轴温升的影响存在一个最佳的适应范围。综上所述,本文主要在高速电主轴的动态性能测试方法、稳态和动态数学模型的建立、控制方法与数学模型之间的相互关系、交叉耦合电压的解耦效果以及对主轴动态性能的影响、主轴整体动力学热模型的建立与主轴温升的影响因素等方面取得了一定的理论和试验测试成果,为揭示高速电主轴的结构参数设计和电磁变量对主轴动态性能的影响机理和规律,进行了比较系统的分析和试验研究,获得了一些有用的结论和试验数据,为高速电主轴的后续研究打下了基础,因而具有一定的学术意义和社会经济效益。更多还原

【Abstract】 High speed motorized spindles, one of the most important part among the key technologies of the high speed machining, are now used increasingly in a broad range of CNC machining centers and high-performance spindles. A high speed motorized spindle has multivariate, non-stationary and complex coupling characteristics as well as considerable complicated interactions between dynamic performance and electromagnetic conversion of the spindle. Therefore, to understand and control this relationship has always been the key part of the high speed motorized spindle investigation. However, it is difficult to conduct dynamic test with load since the spindle speed can go up to very high in operation conditions. The knowledge of the relations between spindles’dynamic performance and electromagnetic conversion are limited, as the lack of fundamental information on high speed motorized spindles and the foreign monopoly of advanced technology, which hinders the in-depth investigation and application of high speed motorized spindles in high speed machining industry. Thus, this project puts forward a set of relative complete dynamic performance test methods based on the electromagnetic characteristics of high speed electric spindles, and the following conclusions can be obtained by comparing experimental data with theoretical analysis:①Dynamic performance test of high speed motorized spindles includes testing electrical and mechanical properties parameters. A dynamometer and a three-phase high frequency electrical parameters instrument et al. auxiliary equipments are used to obtain mechanical and electrical parameters of high speed motorized spindles, such as input voltage, current, power factor, output torque, speed and efficiency, whilst the value of dynamic stiffness can be obtained by exerting a force and testing the force and the displacement in the force direction. Two methods of testing high speed motorized spindles’torque and dynamic stiffness, mechanical and electromagnetic testing method, are given in this paper. For the mechanical contact load means, when a dynamometer is used for obtaining torque, problems of dynamic balance among dynamometer, spindle and coupling necessitate to be addressed. For another, using a non-contact eddy current dynamometer, one need to ensure that load magnetic field is stable and electromagnetic heat of the dynamometer dissipates in time. When testing dynamic stiffness of high speed motorized spindles, if the mechanical contact load mode is selected, problems related with contact wear including failure load, wear debris and friction heat dissipation need to be considered; if the electromagnetic loading mode is employed, not only the stability of the magnetic field but also the magnetic field interference with the displacement sensor needs to be considered to avoid failure data collection.②As the output mechanical energy depends on the electromechanical energy conversion in magnetic field of high speed motorized spindles, the magnetic field control is the emphasis of the study of dynamic performance of high speed motorized spindle, involving establishing mathematical model and selecting the control method for high speed motorized spindles. According to high speed motorized spindles’characteristics, two models are put forward in this paper: a steady-state mathematic model based on effective value of electromagnetic parameters and a process-control-based dynamic mathematic model. With the aim of controlling the air gap magnetic field, when the load changes, the steady-state model control the stator current to maintain the excitation current approximate stable to make sure the relationship between the rotor current and the load is linear. The control method with the steady-state model is very simple and the control accuracy is not high, and it is subjected to the U/f control mode. The process-control-based dynamic mathematic model focuses on controlling the rotor flux and the stator flux, corresponding with vector control mode and direct torque control mode, respectively. In this paper, analysis and experiment of vector control is conducted. The theory of speed sensor-less vector control and the dynamic performance of high speed motorized spindle under this condition are introduced, and the strategies used for maintaining the magnetic flux constant and resisting the external interference when the spindle load changes are described as well as experimental verification is performed.③To ensure the flux is stable when high speed motorized spindles are operated at low frequencies, the input voltage with U/f control should be compensated according to the level of back electromotive force of the stator windings of high speed motorized spindles in rated condition. However, under the vector control mode, the control accuracy of exciting current and torque current depends on the decoupling effects of coupling voltages in the dynamic mathematical model of high-speed motorized spindles. Therefore, effective voltage compensating methods at low frequencies with U/f control are discussed in detail, and validated by experiments. Decoupling means and effect of cross coupling voltages under vector control are compared, and anti-disturbance ability and dynamic speed tracking accuracy of high speed motorized spindles under vector control are verified experimentally.④How the harmonic magnetomotive force of harmonic magnetic field superimposes on the spindle flux, the way in which it affects the spindle electromagnetic torque and output speed, thereby exerting severe influences on the spindle static and dynamic performance, is elaborated. The impacts of different harmonics on spindles vary: the lower the harmonic orders, the more serious the impacts; the lower the frequencies of high speed motorized spindles, the higher the harmonics necessitate to be suppressed. As harmonic interference limits the scope of the actual rotational speed of high speed motorized spindles, the spindle actual speed with load cannot be too low.⑤The principles of electromagnetic heat and friction heat of high speed motorized spindles are analyzed on the basis of electrical machines and kinematics, and the heat transfer coefficient and the thermal resistance of the spindle each part are determined according to heat transfer theory. An integrated dynamic thermal model of high speed motorized spindles is established. The experimental results show that the spindle temperature increases with the spindle speed increases, while there is an optimum range for air pressure and lubricant volume where they exert the lest impact on the spindle temperature rise.In conclusion, some significant achievements in both theoretical and experimental terms can be obtained, including: the methods how to test dynamic performance of high speed motorized spindles are illustrated, the static and dynamic mathematic models are established, the relationship between the control method and the mathematic model is revealed, the decoupling effect of the cross-coupling voltages and its effect on spindles’dynamic performance are described, an integrated dynamic thermal model of high speed motorized spindles is developed and the factors related to the temperature rise of spindles are also determined. To investigate how the structural parameter design and electromagnetic parameters of high speed motorized spindles exert effects on spindles’dynamic performance, systematic analysis and experimental researches are performed, and some useful conclusions and experimental datum are obtained. These investigations constitute the basis for further studies of high speed motorized spindles, and thus they have academic significance and social and economic benefits to a large extent.更多还原