基于LS-SVM逆系统的无轴承异步电机解耦控制

无轴承异步电机具有非线性、多变量和强耦合的特点,要实现电机稳定悬浮和旋转运行,必须对其进行非线性动态解耦控制。为了克服逆系统方法精确建模难的局限性,采用基于最小二乘支持向量机(LS-SVM)α阶逆系统方法对无轴承异步电机进行动态解耦控制的研究。首先利用最小二乘支持向量机辨识出无轴承异步电机的逆模型,然后将它串联在原系统前,将无轴承异步电机解耦成四个独立的伪线性子系统-2个径向位移子系统、一个速度子系统和一个磁链子系统。为保证鲁棒性能,最后对解耦后的系统采用非线性内模控制策略。研究表明,LS-SVMα阶逆系统方法能够实现无轴承异步电机径向悬浮力和旋转力之间的动态解耦控制,控制系统具有良好的静态和动态性能。     

基于参数估计的半挂汽车列车稳定性控制研究

车辆参数估计是半挂汽车列车稳定性控制研究的关键,通过递推最小二乘法（RLS）估计整车质量和轮胎侧偏刚度,进而获取挂车横摆转动惯量,将估计的车辆参数应用于稳定性控制系统,修正控制系统参数.基于商用车动力学仿真软件TruckSim建立了某半挂汽车列车的非线性整车仿真模型,在Matlab/Simulink中设计建立了稳定性控制逻辑和参考响应模型,通过TruckSim-Simulink的联合仿真对控制方案进行了验证分析.结果表明,基于名义参数设计的控制系统受载重变化的影响较大,而带有参数估计的控制系统由于能够对控制参数进行修正,可以较好地适应载运工况的变化,受载运工况的影响较小.     

基于PSO-LSSVM的网络流量预测模型

为了提高网络流量的预测精度,考虑到网络流量的长相关、非线性等特性,提出一种粒子群算法优化最小二乘支持向量机参数的网络流量预测模型（PSO-LSSVM）．首先将最小二乘支持向量机参数作为粒子的位置向量,然后利用粒子群算法找到模型的最优参数,最后采用最优参数最小二乘支持向量机建立网络流量预测模型．仿真结果表明,相对于参比模型,PSO-LSSVM能够获得更高的网络流量预测精度,更能准确描述网络流量变化规律．     

磁通门传感器探头温度特性研究

磁通门传感器主要由磁探头与电路部分组成,其输出不仅随磁场变化,而且易受温度的影响。为了确定磁通门传感器磁探头在宽温度范围下的温度漂移情况,通过试验将探头置于-40℃~150℃的温度环境下,记录得到探头在宽温度范围下,其温度特性曲线近似为正比线性关系。分析认为,磁芯磁滞回线受热偏移与线圈漆包线随温度热胀冷缩是磁探头温漂的主要原因。本文提出选用低磁导率磁芯和高温漆包线绕制探头,并优选一致性较好的探头,采用最小二乘法对温度漂移结果进行拟合补偿,有效地消除了温度对磁探头的影响,提高了磁通门传感器的温度稳定性与应用的广泛性。     

EFFICIENT DESIGNS FOR NONLINEAR MODELING

In the modeling of physical systems, such as chemical reactions, nonlinear models in a set of unknown parameters are commonly developed. Using the method of least squares for model fitting the efficiency of the process is measured by the large sample variance of the parameter estimates. Designs which yield desirable properties in the linear case, such as factorial and central composite designs, are often utilized in the nonlinear model setting. In this paper a method for transforming these standard designs, yielding more efficient estimators, in the nonlinear model case is proposed. The procedure is demonstrated on a typical kinetic reaction model.     

Measurement of soybean fatty acids by near-infrared spectroscopy: Linear and nonlinear calibration methods

A key element of successful development of new soybean cultivars is availability of inexpensive and rapid methods for measurement of FA in seeds. Published research demonstrated applicability of NIR spectroscopy for FA profiling in oilseeds. The objectives of this study were to investigate the applicability of NIR spectroscopy for measurement of FA in whole soybeans and compare performance of calibration methods. Equations were developed using partial least squares (PLS), artificial neural networks (ANN), and support vector machines (SVM) regression methods. Validation results demonstrated that (i) equations for total saturates had the highest predictive ability (r ²=0.91–0.94) and were usable for quality assurance applications, (ii) palmitic acid models (r ²=0.80–0.84) were usable for certain research applications, and (iii) equations for stearic (r ²=0.49–0.68), oleic (r ²=0.76–0.81), linoleic (r ²=0.73–0.76), and linolenic (r ²=0.67–0.74) acids could be used for sample screening. The SVM models produced significantly more accurate predictions than those developed with PLS. ANN calibrations were not different from the other two methods. Reduction in the number of calibration samples reduced predictive ability of all equations. The rate of performance degradation of SVM models with sample reduction was the lowest.     

轴对称液桥的形貌与液桥力

液桥在自然界和工业中广泛存在,其中液桥力扮演了重要角色。本文根据最小势能原理推导了控制液桥形状的拉普拉斯方程,然后数值求解了不同形状探头周围液桥的形貌,并将得到的数值结果与近似解析解进行了对比。最后计算了具有圆柱形、圆锥形以及球形等不同探头周围液桥的液桥力。这些分析对于微操作、精密测量及生物过程有一定的价值。     

基于图像反馈的标靶面与光轴垂直调节系统

介绍了摄像机标定的内部参数,阐述了标靶面与光轴垂直可以简化标定的过程.当标靶面与光轴垂直时,利用标靶面上特征圆在CCD成像面上成像也是圆的特点,提出了基于图像反馈的标靶面与光轴垂直的调节方法.一般情况下,标靶面与光轴不垂直,标靶面上特征圆在CCD成像面上成像为椭圆.通过图像处理和最小二乘椭圆拟合法计算出成像椭圆的长短轴及偏角,设计了调整控制策略.实验结果表明,该方法是有效可行的.     

产量递减的时序分析法预测

首次运用时间序列分析的基本理论和方法,以大港油田港东东区块递减期产油量数据为例,建立该区块产量递减的自回归AR(3)模型,用最小二乘法进行参数估计。通过检验模型效果,相对误差较小。     

供热网循环水泵效率的研究

城市供热系统是极其重要而复杂的大系统,为了提高系统的社会效益和经济效益,从大连北海热电集团热电联产供热管网的实际出发,运用了最小二乘法原理,对采暖循环水泵的性能数据进行曲线拟合,得出了水泵的真正运行状况,并且对使用单台水泵、双台并联或3台并联水泵3种不同情况下的水力工况水泵效率进行了比较和分析。结果表明,单纯地增加并列泵数量对增加流量并无显著变化,并且使并列泵的效率明显下降,只有认真进行严格地工况分析,找到最佳工况点,才能保证整个热系统正常运行。