【作者】 安明伟；

【导师】 王丽梅；

【作者基本信息】 沈阳工业大学 ， 电力电子与电力传动， 2010， 硕士

【摘要】 磁悬浮进给系统具有无污染、无机械接触、无摩擦、无润滑、定位精度高、进给速度及加速度高等优良特性,因此提出在龙门移动式数控机床中采用磁悬浮技术以消除移动横梁与导轨间的摩擦,即将移动横梁悬浮在静止导轨上方,使其不与导轨接触,彻底消除摩擦,实现精加工。本文首先在查阅大量国内外参考文献的基础上介绍了龙门移动式数控机床悬浮横梁的进给结构,阐述了移动横梁的悬浮原理,建立了磁悬浮进给系统的单铁悬浮非线性数学模型;在此基础上,对磁悬浮非线性系统采用输出反馈适应性反演控制策略并进行控制系统仿真。其次,运用反馈线性化方法对系统的非线性模型进行线性化处理,分别得到线性电压控制模型和电流控制模型。在线性化模型的基础上,设计了滑模变结构控制器,仿真结果表明该控制方案具有强鲁棒性,快速性的优点也存在着抖振的不足;为消除滑模控制在切换面上存在的抖振,设计了滑模——神经网络的双自由度控制算法,即采用滑模控制原理设计系统的输入控制,再用神经网络来设计输出反馈控制,仿真结果表明神经网络的自学习和处理能力可以削弱滑模控制中的抖振现象。最后针对系统在运行过程中系统可能受到参数摄动、未建模动态以及刀具切削部件引起的系统质量变化等扰动,设计了适应性滑模-H~∞控制,利用适应性控制理论估测滑模控制中不确定的参数值以降低抖振,利用适应性滑模控制器结合鲁棒控制H~∞理论来抑制干扰,以增加系统的鲁棒性。仿真结果表明,此控制器能有效地估测变化的系统参数、具有小稳态误差和高鲁棒性,可以使系统达到精确定位的目的。更多还原

【Abstract】 Electromagnetic levitation system has many good quality characteristics such as no pollution, no mechanical contact, no friction, no lubrication, high precision positioning and high feed speed and acceleration. Therefore electromagnetic levitation technology is adopted in gantry NC machine tool to eliminate the friction between the crossbeam and guide, namely the crossbeam is levitated upon the guide without contact in order to achieve finishing-cut.First, on the basis of reading many foreign and domestic references, it summarizes the structure and the principle of operation of the gantry NC machine tool moving crossbeam to analyze the levitation theory. The mathematic model is built. The output feedback adaptive backstepping control is applied in the electromagnetic levitation nonlinear system based on this. Second, the nonlinear model is linearized by using feedback linearization method and linear voltage control and current control model are obtained respectively. On the basis of the model, sliding mode controller is designed, the simulation result shows it has advantage of strong robustness and rapidity but there is chattering as well. In order to eliminate the chattering of sliding mode surface, two-degree-freedom control with sliding mode and neural network is proposed. Namely the input controller is designed based on sliding mode control method and the output feedback controller is realized by a neural network. The simulation result shows the chattering can be effectively weakened by self-learning and treatment capacity of the neural network. Lastly, focus on the disturbance of parameter perturbation, unmodeled dynamics and system quality changed by cutting, the adaptive sliding- H~∞control is designed. The adaptive control is adopted to estimate uncertain parameter to improve chattering. In order to weaken the disturbance, adaptive sliding mode controller with H~∞method is applied to strengthen the system robustness. The simulation results are illustrated that the controller can achieve the accurate orientation with effectively estimate system parameter, little steady state error and strong robustness.更多还原