模糊控制在磁悬浮球系统实时控制中的应用

在磁悬浮球系统中采用PID控制时,动态性能较差,控制效果不理想.为了获得控制效果较好的控制器,根据模糊控制原理,设计磁悬浮模糊控制器.根据PID实时控制中的经验,确定模糊控制器的输入输出变量模糊化范围,建立合理的模糊规则表.在Matlab/Simulink中组建实时控制模块,并分别对磁悬浮球系统在无干扰和有干扰下进行实时控制.对控制效果进行分析讨论,证明模糊控制器具有良好的鲁棒性和在非线性系统控制中的有效性.     

Wavelet CMAC for MIMO uncertain nonlinear systems using a modified social ski-driver algorithm

This study uses a Mexican hat wavelet membership function for a cerebellar model articulation controller (CMAC) to develop a more efficient adaptive controller for multiple input multiple output (MIMO) uncertain nonlinear systems. The main controller is called the adaptive Mexican hat wavelet CMAC (MWCMAC), and an auxiliary controller is used to remove the residual error. For the MWCMAC, the online learning laws are derived from the gradient descent method. In addition, the learning rate values are very important and have a great impact on the performance of the control system; however, they are difficult to choose accurately. Therefore, a modified social ski driver (SSD) algorithm is proposed to find optimal learning rates for the control parameters. Finally, a magnetic ball levitation system and a nine-link biped robot are used to illustrate the effectiveness of the proposed SSD-based MWCMAC control system. The comparisons with other existing control algorithms have shown the superiority of the proposed control system.     

A new predictor–corrector approach for the numerical integration of coupled electromechanical equations

In this paper, a new approach for the numerical solution of coupled electromechanical problems is presented. The structure of the considered problem consists of the low‐frequency integral formulation of the Maxwell equations coupled with Newton–Euler rigid‐body dynamic equations. Two different integration schemes based on the predictor–corrector approach are presented and discussed. In the first method, the electrical equation is integrated with an implicit single‐step time marching algorithm, while the mechanical dynamics is studied by a predictor–corrector scheme. The predictor uses the forward Euler method, while the corrector is based on the trapezoidal rule. The second method is based on the use of two interleaved predictor–corrector schemes: one for the electrical equations and the other for the mechanical ones. Both the presented methods have been validated by comparison with experimental data (when available) and with results obtained by other numerical formulations; in problems characterized by low speeds, both schemes produce accurate results, with similar computation times. When high speeds are involved, the first scheme needs shorter time steps (i.e., longer computation times) in order to achieve the same accuracy of the second one. A brief discussion on extending the algorithm for simulating deformable bodies is also presented. An example of application to a two‐degree‐of‐freedom levitating device based on permanent magnets is finally reported. Copyright © 2015 John Wiley & Sons, Ltd.     

磁悬浮球模糊控制系统的研究

本文介绍了磁悬浮球控制系统的结构及工作原理,提出利用模糊控制技术实现钢球稳定悬浮的算法,并通过实验设计了实用的模糊控制器。     

A practical robust nonlinear controller for maglev levitation system

In order to explore the precise dynamic response of the maglev train and verify the validity of proposed controller, a maglev guideway-electromagnet-air spring-cabin coupled model is developed in the first step. Based on the coupled model, the stresses of the modules are analyzed, and it is pointed out that the inherent nonlinearity, the inner coupling, misalignments between the sensors and actuators, and external disturbances are the main issues that should be considered for the maglev engineering. Furthermore, a feedback linearization controller based on the mathematical model of a maglev module is derived, in which the nonlinearity, coupling and misalignments are taken into account. Then, to attenuate the effect of external disturbances, a disturbance observer is proposed and the dynamics of the estimation error is analyzed using the input-to-state stability theory. It shows that the error is negligible under a low-frequency disturbance. However, at the high-frequency range, the error is unacceptable and the disturbances can not be compensated in time, which lead to over designed fluctuations of levitation gap, even a clash between the upper surface of electromagnet and lower surface of guideway. To solve this problem, a novel nonlinear acceleration feedback is put forward to enhancing the attenuation ability of fast varying disturbances. Finally, numerical comparisons show that the proposed controller outperforms the traditional feedback linearization controller and maintains good robustness under disturbances.     

无轴承异步电动机的有限元分析

阐述无轴承异步电动机径向悬浮力产生原理及其数学模型。用有限元方法分析了无轴承异步电动机气隙磁场分布状况及径向悬浮力与绕组中电流之间的非线性关系，为无轴承异步电动机获得最大径向悬浮力的优化设计及对应的控制策略提供了依据。     

单自由度磁悬浮微动机器人的智能控制

提出了一种利用磁力作为机器人运动驱动的新型微动机器人，研究了单自由度微动机器人的工作原理，研究了微动机器人的控制系统，系统包括分析了位移传感器、电磁铁、功率驱动电路、A/D和D/A转换卡等．提出了一种双CMAC的智能控制方式，并用C++和Matlab语言编写了控制程序，经过实验证明所研制的系统能够满足机器人的运动控制要求．     

无轴承异步电机悬浮子系统独立控制的研究

无轴承异步电机转矩绕组和悬浮绕组的独立控制是该电机实现超高速运转的有效途径。针对这一强耦合的非线性复杂系统，本文研究了一套独立的悬浮绕组控制子系统，其中所需的转矩绕组气隙磁链的幅值和相位可通过独立的电压模型方法辩识得到。这样一来，不仅超高速运转成为可能，而且转矩绕组的控制原则上可采用任意的调速方法，特别是低成本、高可靠性的通用变频器的运用将大大提高无轴承异步电机的实用性。实验证明本文提出的悬浮绕组独立的控制子系统能较好地满足电机径向悬浮的稳、动态性能要求。     

Effect of sample radius on stabilityof electromagnetic levitation melting

Based on the power dissipating model of spherical sample in free convection gas medium and the expression of input power, the model of temperature calculation for electromagnetic levitation melting sample was established. Considering the limitation of levitation force and levitation sample temperature, the principle of stability levitation zone computation was determined. A spherical sample (ThDy)Fe2 under the protection of argon gas was examined, and the effect of radius of levitation sample and perturbation on the stable levitation zone was investigated.The results show that longitudinal perturbation and transverse perturbation can shorten the length of stable levitation zone and the range of levitation sample radius. By increasing the sample radius and weakening the perturbation the electromagnetic levitation melting stability of sample can be improved.     

Vergleich des Stofftransports von hängenden und akustisch levitierten Wassertropfen in CO2

High‐pressure acoustic levitation devices allows a contact‐free investigation of liquids. Here, acoustically levitated water droplets and pendant water droplets were examined in regards to the mass transfer coefficient in a static CO₂‐atmosphere under elevated pressures. Based on the droplet geometry and the decrease of the droplet volume over time, it was possible to calculate the mass transfer coefficient of water into CO₂ at any given time. Additionally, open questions regarding possible differences between pendant and acoustically levitated water droplets were discussed.