进给平台直线电动机磁悬浮系统控制策略的研究

Research on Control Strategy of Linear Motor Magnetic Levitation System for Feed Platform

针对用于数控机床进给平台的直线电动机磁悬浮系统(Linear motor magnetic levitation system,LMMLS)具有非线性、扰动的不确定性以及随负载质量而变化的参数不确定性的特点,文章提出采用距离型模糊控制(Distance type fuzzy reasoning control,DFC)策略,以保证系统对这些不确定性具有良好的控制性能。首先,建立LMMLS的数学模型,给出悬浮力的解析表达式以及状态方程;其次,构造输入与输出语言变量的隶属度函数以及模糊规则;然后,利用曼哈顿算法计算每一条控制规则的前件与给定事实之间的距离,并根据该特征求出推理结果的模糊集合,最后,根据分离原则计算出推理结果;仿真结果表明,与PI控制相比较,DFC控制的磁悬浮系统响应速度快、超调量小,有效改善系统的动态性能;对于外界不确定性扰动具有较强的鲁棒性与稳定性。

For the characteristics of Linear motor magnetic levitation system(LMMLS) for the CNC machine feed platform with nonlinearity, disturbance uncertainty and parameter uncertainty varying with load quality, a distance type fuzzy control(DFC) strategy is adopted to ensure that the system has good control performance for these uncertainties. Firstly, the mathematical model of the LMMLS is established, and the analytical expressions of the levitation force and the state equations are given. Secondly, constructing the membership function of the input and output linguistic variables and the fuzzy rules;then, using the Manhattan algorithm to calculate the distance between the antecedent of each control rule and the given fact, and based on the feature, the fuzzy set of the inference results can be obtained. Finally, the inference results are calculated according to the separation principle. The simulation results show that compared with the PI control, the DFC controlled magnetic levitation system has fast response speed and small overshoot, which effectively improves the dynamic performance of the system. For external uncertainty disturbances, it has strong robustness and stability.