Parameter Optimization of Linear Quadratic Controller Based on Genetic Algorithm

The selection of weighting matrix in design of the linear quadratic optimal controller is an important topic in the control theory. In this paper, an approach based on genetic algorithm is presented for selecting the weighting matrix for the optimal controller. Genetic algorithm is adaptive heuristic search algorithm premised on the evolutionary ideas of natural selection and genetic. In this algorithm, the fitness function is used to evaluate individuals and reproductive success varies with fitness. In the design of the linear quadratic optimal controller, the fitness function has relation to the anticipated step response of the system. Not only can the controller designed by this approach meet the demand of the performance indexes of linear quadratic controller, but also satisfy the anticipated step response of close-loop system. The method possesses a higher calculating efficiency and provides technical support for the optimal controller in engineering application. The simulation of a three-order single-input single-output (SISO) system has demonstrated the feasibility and validity of the approach.     

Robust direct adaptive fuzzy control for nonlinear MIMO systems

For a class of nonlinear multi-input multi-output systems with uncertainty, a robust direct adaptive fuzzy control scheme was proposed. The feedback control law and adaptive law for parameters were derived based on Lyapunov design approach. The overall control scheme can guarantee that the tracking error converges in the small neighborhood of origin, and all signals of the closed-loop system are uniformly bounded. The main advantage of the proposed control scheme is that in each subsystem only one parameter vector needs to be adjusted on-line in the adaptive mechanism, and so the on-line computing burden is reduced. In addition, the proposed control scheme is a smooth control with no chattering phenomena. A simulation example was proposed to demonstrate the effectiveness of the proposed control algorithm.     

Optimization of block-floating-point realizations for digital controllers with finite-word-length considerations

The closed-loop stability issue of finite-precision realizations was investigated for digital control-lers implemented in block-floating-point format. The controller coefficient perturbation was analyzed resultingfrom using finite word length (FWL) block-floating-point representation scheme. A block-floating-point FWL closed-loop stability measure was derived which considers both the dynamic range and precision. To facilitate the design of optimal finite-precision controller realizations, a computationally tractable block-floating-point FWL closed-loop stability measure was then introduced and the method of computing the value of this measure for a given controller realization was developed. The optimal controller realization is defined as the solution that maximizes the corresponding measure, and a numerical optimization approach was adopted to solve the resulting optimal realization problem. A numerical example was used to illustrate the design procedure and to compare the optimal controller realization with the initial realization.     

Science Letters：On stochastic optimal control of partially observable nonlinear quasi Hamiltonian systems

A stochastic optimal control strategy for partially observable nonlinear quasi Hamiltonian systems is proposed. The optimal control forces consist of two parts. The first part is determined by the conditions under which the stochastic optimal control problem of a partially observable nonlinear system is converted into that of a completely observable linear system. The second part is determined by solving the dynamical programming equation derived by applying the stochastic averaging method and stochastic dynamical programming principle to the completely observable linear control system. The response of the optimally controlled quasi Hamiltonian system is predicted by solving the averaged Fokker-Planck-Kolmogorov equation associated with the optimally controlled completely observable linear system and solving the Riccati equation for the estimated error of system states. An example is given to illustrate the procedure and effectiveness of the proposed control strategy.     

Robust control for uncertain singular systems with time-varying delay

We study the problem of L2-L∞, control for a class of uncertain singular systems with time-delay and norm-bounded parameter uncer- tainties in this paper. A new delay-dependent robust stability criterion is obtained in terms of linear matrix inequalities （LMIs）. Based on this criterion, a state feedback controller is designed to guarantee that the closed-loop system is regular, impulse free and stable with a prescribed L2-L∞ performance satisfied for all admissible parameter uncertainties. A simulation example is included to illustrate the effectiveness of the proposed method.     

Active Noise Control for Vehicle Exhaust Noise Reduction

An active noise control (ANC) method was developed for exhaust noise reduction for medium-duty diesel trucks. A modified variable step size least mean squares (LMS) algorithm was used for the controller ina variable environment that considered the vehicle‘s acceleration characteristics. The variable step size time-based synchronized filtered-x LMS method (SFX-TB) used an adaptive algorithm that was more efficient than the conventional flltered-x LMS algorithm. The simulation and the experimental tests show that the control trackability and stability provided by the algorithm during acceleration enable the ANC system to effectively reduce the vehicle exhaust noise.     

An Adaptive Model and Algorithm for an Electrohydraulic Position Servo System in Auto Gauge Control for Aluminum Hot Tandem Mill

The electrohydraulic servo position control system (HPC) is the core of an auto gap control for a modern fourhigh continuous hot strip mill. The actuators are loaded with considerable external disturbances, rolling forces, and the system stiffness and position accuracy will become hypersensitive to the leakage and the compressibility of the oil. Many efforts have being made to increase the position accuracies. The conventional resources are proportion integral differential (PID) controller. But the PID controller is faint for a considerable external disturbance. In this paper, by introducing the adaptive control strategy of model reference the reciprocities of the system structure with the loads were analyzed. With the Lyapunov energy function, an adaptive control algorithm applied to improve the system accuracy was formulated. The system simulations and the selection of parameters of the model were also discussed. The simulations show the static state errors at 0.02%. Finally, the industrial experimental result was given.     

多变量系统的鲁棒自适应控制

考虑了具有未建模动态和外来有界干扰的离散时间多变量系统，提出了一种鲁棒自适应控制方案。这种控制器是基于系统的降阶模型设计的，其建模部分的参数估计采用带有死匹的最小二乘算法。在相当一般的假设下，证明了所建立的闭环系统是全局稳定的和跟踪误差是有界的。     

具有未知类反斜线回滞系统的自适应模糊控制

基于变结构控制原理,利用模糊逻辑系统对未知函数进行在线逼近,提出了一种具有监督器的自适应模糊控制方法.该方法通过监督控制器保证闭环系统所有信号有界,并引入最优逼近误差的自适应补偿项以消除建模误差的影响.通过李亚普诺夫方法,证明了跟踪误差收敛到零的一个小邻域内.仿真结果表明了该方法的有效性.     

一种新的极点配置鲁棒自适应控制

一种新的极点配置鲁棒自适应控制张天平，冯纯伯（东南大学自动化研究所，南京２１００１８）自Ｒｏｈｒｓ等人［１］提出：如果系统存在未建模动态，那么在理想条件下给出的自适应算法会产生不稳现象以来，自适应控制系统的鲁棒性一直是控制理论研究的中心课题之一．文献...     

基于观测器和全局收缩映射的设定点控制

在没有速度测量和重力无法精确补偿条件下,研究了并联机器人的设定点控制。利用线性观测器理论对速度信号进行观测,设计了带有速度近似的比例拟微分(PD-proportion pseudo derivative) 有偏标称重力补偿的设定点控制方法。该控制器只能得到全局有偏稳定的控制结果。借助全局收缩映射定理,定义了参数修正算法,利用系统静差对观测器参数进行在线地重复修正,得到全局渐进稳定的控制效果。该观测器不需要系统模型,控制器-观测器结构简单,易于实用。对六自由度并行机器人的仿真实验表明:选择不同的设计参数可以获得不同收敛速度和输出震颤,但都能够确保系统输出收敛到标称点。     

一类具有非线性输入系统的自适应模糊控制

基于滑模控制基本原理,利用I型模糊逻辑系统对未知函数进行在线逼近,提出了一种具有监督器的自适应模糊滑模控制方法.该方法通过监督控制器保证闭环系统所有信号有界,并进一步引入最优逼近误差的自适应补偿项来消除建模误差的影响.通过李亚普诺夫方法,证明了跟踪误差收敛到零.仿真结果表明了该方法的有效性.     

一类单输入单输出非线性系统全局有限时间输出反馈控制

运用高增益方法、几何齐次理论、李雅普诺夫理论和有限时间稳定理论,研究了一类单输入单输出非线性系统的全局有限时间输出反馈控制问题,设计了由线性部分和非线性部分构成的输出反馈控制器。其中,线性部分的作用是确保闭环系统的零解是全局渐近稳定的,而非线性部分的作用是确保闭环系统的零解是局部有限时间稳定的。最后,仿真实例验证了所设计的控制器的有效性。     

基于Backstepping方法对不确定性Chen系统的自适应控制

基于Backstepping方法对含不确定性Chen混沌系统进行控制.当非线性Chen系统含有三个关键参数未知时,通过利用该系统的特殊性质,运用自适应控制器的设计方法,构造恰当的控制器,从而使闭环系统消除混沌并最终达到全局稳定.仿真结果验证了该方法的有效性.     

一类非线性系统的全局自适应输出跟踪控制

研究一类具有不可控不稳定线性化和未知线性化参数的非线性系统的全局自适应控制·控制目标是设计一种鲁棒自适应非线性状态反馈控制器,实现系统的全局实用输出跟踪·应用Lyapunov稳定性理论和修正的自适应增加幂积分方法,给出了一个系统化的设计程序,递推设计了一种非线性自适应光滑状态反馈控制器·该控制器能保证跟踪误差充分小,且闭环系统所有信号全局有界·仿真结果表明该控制器是可行的并且是有效的·     

基于互联系统的鲁棒控制

讨论了一类时滞互联系统的鲁棒控制问题。不同于以往的结论，所讨论系统中的不确定非线性互联项关于一具有未知增益的高阶多项式的函数有界，且不要求系统满足匹配条件。首先提出了能保证闭环系统渐近稳定的线性分散自适应控制器，然后给出了一类可使闭环系统最终一致有界稳定的分散非线性控制器。     

一类不确定非线性时滞系统的自适应控制

考虑了一类不确定非线性时滞系统的自适应控制.基于Lyapunov稳定性理论和线性矩阵不等式(LMI)方法,处理了系统中的时滞项,并且巧妙地构造了自适应控制器和反馈控制器.通过估计非线性部分的未知参数,自适应控制器补偿了系统中的非线性部分,并保证了闭环系统是渐近稳定的.最后,数值例子和仿真结果验证了所设计控制器的有效性.