【作者】 周海波；

【导师】 段吉安；

【作者基本信息】 中南大学 ， 机械工程， 2010， 博士

【摘要】 磁悬浮直线运动是运用电磁力实现运动体无机械接触地稳定悬浮于直线导轨上方指定位置,同时利用电磁直线驱动技术驱动运动体沿导轨做直线运动。磁悬浮直线运动具有无摩擦、无磨损、无需润滑等优点,这种直线运动装置能提供超精密、高速度的直线定位运动,适合超洁净工作环境,在现代精密制造领域有着非常广泛的应用前景。但由于磁悬浮直线运动系统是一个具有强耦合、强非线性特性的复杂多输入多输出系统,其运动精度和承载特性主要取决于平台的结构参数和控制系统。因此,磁悬浮直线运动系统的设计及高性能解耦控制器的研究具有极其重大的意义。本文利用磁悬浮支撑技术和电磁直线驱动技术,设计了一种新型大行程磁悬浮精密快速直线定位运动系统。该系统能提供大行程的超精密快速直线运动,系统由悬浮子系统和直线驱动子系统两部分组成。悬浮子系统由直线导轨、悬浮体及测量反馈系统组成,通过安装在悬浮体内的六对电磁铁实现悬浮体无接触地稳定悬浮于导轨上方指定位置；直线驱动子系统则由永磁定子、可控电磁动子及测量反馈系统组成,以实现悬浮体沿水平导轨方向的大行程直线往返运动。在悬浮子系统中,采用差动式双电磁力驱动结构,大大提高了悬浮体的悬浮刚度。通过有限元软件分析平台在静止和稳定悬浮两种状态下的静力学变形、各阶模态,获得了最优的运动平台结构参数。针对多个电磁铁之间存在的磁场耦合及发热问题,运用有限元方法对电磁铁进行磁场分析和热分析,根据磁场分析结果对电磁铁的结构和空间布局进行了优化,最大程度地减少了电磁铁间的磁场耦合。根据电磁铁的发热量及热流分析结果设计出了电磁铁的冷却装置。为实现磁浮直线运动平台的高性能稳定运动,控制器、功率放大器具有非常重要的作用。本文针对磁浮直线运动系统开发了基于DSP的数字控制器和一种具有可调偏置电流的PWM型开关功率放大器。在磁浮直线运动平台的悬浮运动中,由于悬浮体内多对电磁铁间存在明显的动力学耦合,悬浮运动控制成为了整个平台控制的重点和难点。本文首先设计了六个独立的DSP数字控制器,并利用PID控制算法实现了悬浮体的稳定悬浮。由于没有考虑悬浮运动中各个驱动力之间的相互耦合,系统的悬浮精度、动态性能欠佳。为实现平台的高性能解耦运动控制,综合分析了各驱动力之间的耦合特性,并提出了一种利用位置反馈和力反馈相结合的解耦控制策略。通过对平台的悬浮子系统进行控制建模及参数辨识,找出了解耦策略的一种简单表达式并实现了平台各悬浮力之间的动力学解耦控制。针对电磁铁内在的强非线性特性,为提高悬浮运动控制器的精度,进一步提出了一种新型的具有自适应能力的二型模糊控制算法,该二型模糊自适应控制算法具有处理各种非线性不确定因素的能力。最终的实验数据显示该自适应二型模糊控制器进一步提高了整个平台的控制精度。本文通过对精密磁悬浮直线运动系统的开发和解耦控制方法的研究,对解决未来超精密高速直线定位运动等关键技术问题、提升相关产业装备的质量,缩短相关精密制造装备的研发周期都起到了非常重要的作用。更多还原

【Abstract】 The magnetic levitation linear motion system employs magnetic levitation mechanism and magnetic linear propulsion motor, and has the potential to achieve ultra-precision, long-range and high-speed motion of an object. It has many advantages over traditional moving mechanisms due to its contact-free and wear-free. It has been widely used in various motion systems such as high-speed maglev trains and frictionless bearings. Therefore, it has become a feasible choice for developing ultra-precision positioning mechanisms. However, maglev transportation system is a complicated nonlinear multi-input multi-output (MIMO) coupling system. The bearing characteristic of maglev platform is not only determined by its structural configuration, but also the controller design. Therefore, it has great significance to investigate a decoupling nonlinear control system for the magnetic suspension platform.In this dissertation, a novel maglev transportation platform is constructed for realizing large travel ultra precision high-speed linear motion. The present maglev transportation platform consists of a levitation subsystem and a propulsion subsystem. In the levitation subsystem, six pairs of electromagnets are used to suspend the moving platform. For every pair of electromagnets, differential electromagnet driving mode is employed to provide suspension force. Such differential electromagnet driving gives better suspension stiffness and suspension performance. Through analyzing the magnetic coupling of electromagnets with finite-element (FE) method, an optimized electromagnets spatial distribution is designed. The optimal case uses eight U-shaped and four E-shaped electromagnets to assemble the levitation subsystem, and it greatly diminishes the magnetic coupling effects among electromagnets. With FE method, the heat generation mechanism and heat flow in electromagnet is analyzed and the cooling mechanism is also designed. A special digital DSP controller and a unique PWM power amplifier are designed for the magnetic suspension plate.To remove the redundant constraints or dynamic coupling existing among six electromagnets, a decoupling levitation control strategy is developed for the novel maglev transportation system. In the decoupling control strategy, three separate controllers are employed for three electromagnets pairs of four ones, and then by real-time computing the electromagnetic force of the three electromagnets pairs, the decoupling controller creates the corresponding decoupling control signal for the fourth electromagnets pairs. Therefore, the control of the fourth electromagnets pairs follows the changes of other three electromagnets pairs’electromagnetic forces, and the fourth electromagnets pairs bring no wallop to the existed three electromagnets pairs. All four controllers work for their own electromagnets pairs and the coupling effects among them are removed. Additionally, this decoupling levitation strategy facilitates the controller design. The experimental results show that the decoupling levitation control strategy decouples the interactions among four channels perfectly. Moreover, the controllers are simple, effective and easy to be implemented in practice.To handle the uncertainties in electromagnets and magnetic suspension stage, a novel Type 2 adaptive fuzzy control method is proposed. Because the T2 fuzzy set is three-dimensional and includes a spatial uncertainty band, the T2 fuzzy set will provide a better capability of modeling uncertainties. In the Type 2 adaptive fuzzy controller, a simple type-reducer is employed to avoid the complex iterative computation. Then to determine the quanity of T2 fuzzy control better than its Tl counterpart, a genetic algorithm is used to optimize the controller parameters and compare their performance under various settings in simulation. Finally, the new Type 2 adaptive fuzzy control method is used to control the present magnetic suspension platform. The experimental control performance verifies that the new method has better control performance and robustness.In this dissertation, a novel magnetic decoupling control method is proposed. This study gives great guidance to achieve ultra-precision and high-speed linear positioning movement, and it plays a key role in improvement of the industrial equipments and reduction of R & D periods in precision manufacturing facilities.更多还原