非线性地基上正交异性矩形板的非线性热振动

研究了非线性地基上正交异性矩形板的非线性固有热振动.采用常规的L-P法分析非线性地基上正交异性矩形板的非线性热振动难以得到高精度的近似解,为此,先对该强非线性振动系统进行参数变换,将该强非线性振动系统转化为弱非线性振动系统.然后采用改进的L-P法进行求解,得到了强非线性振动系统的高精度近似解.此外,讨论了温度、地基特征参数、长宽比等因素对非线性地基上正交异性矩形板非线性热振动固有频率的影响,得到了非线性地基上正交异性矩形板热振动频率随温度下降、地基特征参数变大、长宽比变大而增大的结论.     

基于神经网络的非线性系统多步预测控制

针对离散非线性系统,利用非线性激励函数的局部线性表示,提出一种可用于非线性过程的神经网络多步预测控制方法,并给出了控制律的收敛性分析．该方法将非线性系统处理成简单的线性和非线性两部分,对复杂的非线性多步预测方程给出了直观而有效的线性形式,并用线性预测控制方法求得控制律,避免了复杂的非线性优化求解．仿真结果表明了该算法的有效性．     

数字微波通信系统中的非线性

本文简要分析数字微波通信系统中非线性的来源、变化规律及其对系统传输特性的影响,介绍了对抗系统非线性的几种措施,提出了一种可用于计算机模拟的非线性分析方法,还讨论了系统非线性特性的测试,以及有关非线性的几个重要概念。     

互联非线性系统反馈主导控制设计方法及汽门开度控制应用

分析了电力系统非线性的数学性质,指出电力系统非线性是一种有界非线性.在此基础上,将反馈主导方法(feedback domination method,FDM)引入多机电力系统非线性控制.该方法与反馈线性化方法不同;反馈线性化方法是通过反馈将原非线性系统转化为线性系统,反馈主导方法则是通过反馈将原非线性系统转换为特定形式的非线性系统,该特定形式的非线性系统的动态由反馈引入的非线性部分主导.以多机系统非线性汽门控制问题为例,设计了反馈主导非线性汽门控制器,该控制器仅包含本地量测量,易于实现.数值仿真表明,多机系统反馈主导非线性汽门控制器可显著提高电力系统暂态稳定性.     

基于支持向量机的可分离非线性动态系统辨识

针对状态变量和控制变量可分离的非线性动态系统模型,通过引入两个非线性核函数重新设计了标准支持向量机的回归估计模型,使之适用于非线性动态系统的辨识. 它包含两个分别关于状态变量和控制变量的非线性函数,用于辨识可分离变量非线性动态系统中的两个非线性函数.文中的仿真实验验证了我们算法用于非线性动态系统辨识的有效性.     

传感器动态非线性补偿方法及DSP实现

利用Hammerstein模型描述传感器的动态非线性。动态非线性环节表示为静态非线性子环节和动态线性子环节的串联,相应的动态非线性补偿分为两个阶段：动态线性补偿和静态非线性校正。通过仿真和对腕力传感器响应的补偿验证了两阶段补偿方法的可行性。研制了基于DSP的动态非线性实时补偿系统,通过实验验证了动态非线性补偿方法的有效性。     

一种新型非线性PID控制器及其参数设计

方法简单、参数效率高是非线性PID控制器所期望的特征. 本文提出一种新的非线性PID控制器设计方法,并就其非线性函数的函数特点以及控制器参数选择问题进行了分析. 首先, 利用电容极间场强的作用原理提出了一种非线性函数构造方法, 并用来对常规PID控制器进行修正, 形成一种非线性PID控制器; 其次, 对非线性函数进行了分析, 指出了不同参数对非线性函数的影响; 最后, 利用T–无源的有关结论对这种非线性PID控制器的稳定性进行分析, 得到了这一非线性PID控制器的参数设计依据. 仿真实例表明了文中所提控制     

超宽带系统电路的非线性研究

对超宽带非线性系统进行了详细分析,论证了超宽带电路脉冲信号、放大器和混频滤波耦合器的非线性特性,设计了超宽带系统非线性关键电路。周期性稳态分析仿真表明,电路满足超宽带非线性性能指标。     

一类非线性PID控制系统稳定性分析

针对一类由非线性增益函数与典型PID控制器级联组成的非线性系统,采用波波夫判据对此类闭环控制系统进行稳定性分析.分别确定了确保非线性PID,P,PI,PD闭环控制系统稳定的非线性增益的有效取值范围,为此类非线性控制系统的实际工程应用奠定了基础.     

基于模型分解的间歇聚丙烯过程预测控制

针对间歇聚丙烯过程的非线性,间歇性,提出了基于模型分解的非线性前馈一线性反馈相结合的控制方案。在分析过程非线性特性的基础上,采用基于过程模型的前馈抵消反应热对过程的非线性影响。通过引入非线性前馈控制粗调,使反馈控制细调的控制模型得以近似为线性模型,方便地实现了具有优异控制性能的线性预测控制方法,达到了集非线性前馈适应严重非线性过程特性与线性预测控制实现了高精度的控制质量的有机结合。实验结果显示了该方法的有效性。     

Robust nonlinear control associating robust feedback linearization and H/sub /spl infin// control

In this note, a robust nonlinear controller for a nonlinear system subject to model uncertainties is proposed. Such a controller associates a "robust feedback linearization" with a robust linear H/sub /spl infin// controller. The robust feedback linearization exactly transforms the nonlinear system into a linear system equal to the linear approximation of the original nonlinear system around a nominal operating point. The robustness of the resulting overall nonlinear controller is proved by theoretical arguments and illustrated through an application example, the control of a magnetic bearing system.     

Nonlinear state feedback controller for nonlinear systems:Stability analysis and design based on fuzzy plant model

This paper presents the stability analysis of a fuzzy-model-based control system consisting of a nonlinear plant and a nonlinear state feedback controller and the design of the nonlinear gains of the controller. The nonlinear plant is represented by a fuzzy model having p rules. A nonlinear state feedback controller is designed to close the feedback loop. Under this design, the stability condition is reduced to p linear matrix inequalities. An application example on stabilizing a mass-spring-damper system will be given     

基于控制系统直接方法的非线性系统预见控制器设计

针对一类非线性离散时间系统给出最优预见控制器设计方法. 首先运用非线性控制系统直接控制方法的思想, 将非线性反馈部分作为形式输入, 使得系统成为“形式上”的线性系统; 然后, 针对该线性系统, 利用最优预见控制的基本方法设计最优预见控制器; 最后, 利用形式输入与实际输入的关系得到非线性离散时间系统的最优预见控制器. 证明了如果形式线性系统满足一定的可镇定和可检测条件, 则闭环系统是渐近稳定的. 数值仿真结果表明了控制器的有效性.

     

Advanced automotive thermal management – Nonlinear radiator fan matrix control

Advanced automotive cooling systems for gasoline and diesel engines can improve the powertrain performance. The replacement of the mechanical driven coolant pump and radiator fans with computer controlled servo-motor actuators, and update of the wax-based thermostat valve with a 3-way variable position smart valve, allow the coolant flow rate and proportion directed through the radiator to be carefully adjusted. A smart thermal management system approach can regulate the forced convection heat transfer process to match the engine׳s cooling needs. This paper presents a Lyapunov based nonlinear control strategy to solely operate the radiator fan matrix for transient engine temperature tracking. A reduced order mathematical model serves as the basis for the closed-loop feedback system. An adaptive backstepping method was implemented to derive the control law. An experimental test bench with multiple radiator fans, heat exchanger, wind tunnel, coolant pump, three way valve, and engine thermal load has been fabricated. Representative numerical and experimental tests demonstrate that the advanced control strategy can regulate the engine temperature tracking error within 0.12 °C and compensate the unknown heat load. The nonlinear controller provided superior performance in terms of power consumption and temperature tracking as evident by the reduced magnitude when compared to a classical PI with lookup table based controller and a bang bang controller.     

Structure and stability analysis of a Takagi–Sugeno fuzzy PI controller with application to tissue hyperthermia therapy

 In this paper, we first reveal the analytical structure of a simple Takagi–Sugeno (TS) fuzzy PI controller relative to the linear PI controller. The fuzzy controller consists of two linear input fuzzy sets, four TS fuzzy rules with linear consequent, Zadeh fuzzy logic AND and the centroid defuzzifier. We prove that the fuzzy controller is actually a nonlinear PI controller with the gains changing with process output. Utilizing the well-known small Gain Theorem in control theory, we then derive sufficient conditions for global stability of the fuzzy control systems involving the TS fuzzy PI controller. Finally, as an application demonstration, we apply the fuzzy PI controller to control issue temperature, in computer simulation, during hyperthermia therapy. The relationship between heat energy and tissue temperature is represented by a linear time-varying model with a time delay. The sufficient conditions for global stability are used to design a stable fuzzy control system. Our simulation results show that the fuzzy PI control system achieves satisfactory temperature control performance. The control system is robust and stable even when the model parameters are changed suddenly and significantly.     

基于QCNN的非线性跟踪问题研究

针对如何快速准确地跟踪到非线性系统的状态问题, 研究了量子细胞神经网络(QCNN)在非线性跟踪中的应用。在满足Lyapunov函数指数收敛的条件下, 设计了一种新型参数形式的控制器, 在此基础上, 对三种非线性系统即确定性非线性运动、参数和运动规律未知的非线性数据系统以及典型蔡氏电路进行了QCNN跟踪研究。仿真结果表明, 在QCNN系统中, 通过设计合理的控制器可以实现非线性问题状态的有效跟踪, 且实验结果为QCNN系统复杂度与跟踪的及时性之间关系提供了参考依据和有力的说明。设计的新型控制器及对实际问题处理方法为QCNN的理论及应用研究具有借鉴意义。     

Nonlinear controller construction based on a model with state-dependent representation for a nonlinear system

This paper addresses a method of nonlinear controller construction based on a model with a state-dependent representation for a nonlinear system. In this method, the controller construction and generation of manipulated values are separated. A nonlinear system and its controller are firstly expressed by the coefficients of the state-dependent representation without any approximation. At the stage of controller implementation for the nonlinear system, the manipulated values are calculated by means of an algorithm of the numerical analysis. The properties of the proposed method are analysed. With the analytical considerations and simulation studies, the proposed method is compared with several nonlinear control methods, such as exact linearization method and the linear approximation method, and its merits are verified.     

多输入非线性系统控制的分步变换与设计

研究多输入非线性系统基于分步变换及设计思想的非线性控制器设计问题。针对一般多输入非线性系统，首先利用非线性状态变换的方法进行非线性变换，得到一中间非线性系统模型，然后引入状态反馈，使得闭环系统为线性能控标准模型；从而利用分步设计的思想，实现非线性系统的最优控制。最后以－液位－温度控制系统为例，通过仿真说明该方法的有效性和可行性。     

发电机的非线性自适应逆推综合控制

发电机励磁和汽门系统是一个典型的多变量、非线性、强耦合、不确定复杂系统,其综合控制将会改善电力系统稳定性和动态品质,所以设计简单、有效的综合控制器既必要又困难.针对单机无穷大励磁与汽门系统,运用自适应逆推方法和系统的Lyapunov函数,获得了发电机的非线性综合控制器和参数替换律,文中给出了该控制器的具体设计步骤.由于在控制器设计中没有运用任何线性化方法,因而所得控制器充分利用了系统的非线性特性;同时考虑了发电机阻尼系数的不确定性,使得控制器对系统参数的变化具有很强的鲁棒性.数字仿真结果表明,所设计的控制器具有鲁棒性,并可有效地提高电力系统的稳定性.     

Temperature control of industrial gas phase polyethylene reactors

The performance of linear and nonlinear temperature control schemes is assessed for an open-loop unstable gas-phase polyethylene reactor (GPPER), based on speed, damping, robustness and the ability to maintain closed-loop stability in different operating regimes. An existing industrial GPPER model is improved by modelling the temperature states in the external heat exchanger using linear and nonlinear driving force models with varying numbers of heat transfer stages. Differences in heat exchanger models do not produce gain mismatch but do result in phase mismatch. It is shown that the nonlinear error trajectory controller (ETC) exhibits significantly superior responses in terms of speed, damping and robustness compared with an optimally-tuned PID controller. Therefore, substantial benefits could be realized using nonlinear controllers because they can provide good disturbance rejection capabilities and ensure closed-loop stability over a wide range of operating conditions. An approach is presented for tuning ETCs for minimum-phase processes of arbitrary relative degree.