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An improved nonlinear adaptive switching control method is presented to relax the assumption on the higher order nonlinear terms of a class of discrete-time non-affine nonlinear systems. The proposed control strategy is composed of a linear adaptive controller, a neural network (NN) based nonlinear adaptive controller and a switching mechanism. An incremental model is derived to represent the considered system and an improved robust adaptive law is chosen to update the parameters of the linear adaptive controller. A new performance criterion of the switching mechanism is designed to select the proper controller. Using this control scheme, all the signals in the system are proved to be bounded. Numerical examples verify the effectiveness of the proposed algorithm. 相似文献
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基于阶跃模型的非线性模糊PID控制算法研究 总被引:1,自引:1,他引:0
针对大多数非线性系统建模和控制较困难的问题,引入了基于C-R模糊阶跃模型的非线性系统建模方法,该模型中的参数ai*是时变的,能够表征系统的非线性特征。根据C-R模糊阶跃模型的结构特点,与PID控制算法结合,将ai*表示出PID控制算法的参数,提出了非线性模糊PID控制算法CR-PID,克服了常规PID控制的参数难以较好地表征非线性的问题。通过对连续搅拌反应釜控制系统的仿真结果表明了该方法的有效性。 相似文献
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A direct nonlinear adaptive control of state feedback linearizable single-input single-output systems is proposed in the case when parametric uncertainties are represented linearly in the unknown parameters. The main feature of the proposed nonlinear adaptive control system is that the linearizing coordinate transformation and the state feedback are updated by parametric adaptive law, derived using the second method of Lyapunov. The proposed adaptive control scheme is relatively straightforward and simple in the sense that it does not use the concept of augmented error. This adaptive control scheme is numerically applied to an exothermic chemical reactor system and is compared with the nonadaptive stale feedback linearization which has an integral action. The simulation shows that the proposed adaptive control scheme can be applied effectively to highly nonlinear, uncertain chemical systems. 相似文献
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基于神经网络和多模型的非线性自适应PID控制及应用 总被引:4,自引:2,他引:2
针对一类未知的单输入单输出离散非线性系统,提出了基于神经网络和多模型的非线性自适应PID控制方法。该方法由线性自适应PID控制器、神经网络非线性自适应PID控制器以及切换机构组成。采用线性自适应PID控制器可保证闭环系统所有信号有界;采用神经网络非线性自适应PID控制器可改善系统性能;通过引入合理的切换机制,能够在保证闭环系统稳定的同时,提高系统性能。理论分析表明,该方法能够保证闭环系统所有信号有界,如果适当地选择神经网络的结构和参数,系统的跟踪误差将收敛于任意给定的紧集。将所提出的方法应用于连续搅拌反应釜,仿真结果验证了所提出方法的有效性。由于该方法基于增量式数字PID控制器,在工业过程中有着广阔的应用前景。 相似文献
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利用正交多项式组合神经网络对聚合反应分子量分布(MWD)进行建模,MWD被解构为若干矩值组成的矩向量函数,由此二元MWD控制问题可被转换为一元分布矩控制问题。以矩向量为直接被控对象,通过对矩的控制实现MWD的跟踪。为便于求解这类非仿射非线性多变量系统的控制策略,提出了改进型非线性自回归正交多项式网络结构,建立模型输出与U(k)之间的线性映射关系;针对高维被控矩向量,证明了矩向量中独立变量与分布函数参变量间的数量对等关系,给出了矩向量降维准则,将高维输出控制转化为低维问题。基于改进的神经网络模型,利用输出反馈方法对MWD矩向量进行控制,实现了对MWD的形状跟踪,仿真实验证明了方法的有效性。所提出的方法为非线性多变量系统的建模控制问题提供了新思路。 相似文献
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针对非线性动态系统的控制问题,提出了一种基于自适应模糊神经网络(adaptive fuzzy neural network, AFNN)的模型预测控制(model predictive control, MPC)方法。首先,在离线建模阶段,AFNN采用规则自分裂技术产生初始模糊规则,采用改进的自适应LM学习算法优化网络参数;然后,在实时控制过程,AFNN根据系统输出和预测输出之间的误差调整网络参数,从而为MPC提供一个精确的预测模型;进一步,AFNN-MPC利用带有自适应学习率的梯度下降寻优算法求解优化问题,在线获取非线性控制量,并将其作用到动态系统实施控制。此外,给出了AFNN-MPC的收敛性和稳定性证明,以保证其在实际工程中的成功应用。最后,利用数值仿真和双CSTR过程进行实验验证。结果表明,AFNN-MPC能够取得优越的控制性能。 相似文献
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In this work, regular solution theory was applied to study the solubility of solids in a supercritical fluid (SCF) with and
without cosolvent, and a new model for binary and ternary systems was proposed. The activity coefficient can be obtained from
the model and the solubility can then be calculated easily. For a binary system there are two adjustable parameters and for
a ternary system, four adjustable parameters; the parameters are related to the interactions between molecules in solution.
The proposed model was compared with the HSVDW1 and HSVDW2 models. The calculated results show that the proposed model is
more accurate, and the AAD for the three models is 4.5%, 7.9% and 18.5%, respectively. The model was further used to correlate
the solubility data of 2-naphthol in SC CO2 with and without cosolvent measured by us before, and the overall AAD is 3.23%. 相似文献
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Many chemical processes can be modeled as Wiener models, which consist of a linear dynamic subsystem follow-ed by a static nonlinear block. In this paper, an effective discrete-time adaptive control method is proposed for Wiener nonlinear systems with uncertainties. The parameterization model is derived based on the inverse of the nonlinear function block. The adaptive control method is motivated by self-tuning control and is derived from a modified Clarke criterion function, which considers both tracking properties and control efforts. The un-certain parameters are updated by a recursive least squares algorithm and the control law exhibits an explicit form. The closed-loop system stability properties are discussed. To demonstrate the effectiveness of the obtained results, two groups of simulation examples including an application to composition control in a continuously stirred tank reactor (CSTR) system are studied. 相似文献
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针对具有输入时滞的多阶段间歇过程,考虑执行器故障影响,提出了无穷时域优化混杂容错控制器设计方法。该方法首先将给定具有输入时滞的模型转化为新的无时滞的状态空间模型,接着再将此模型转换为包含状态变量误差和输出跟踪误差的扩展状态空间模型,并用切换系统模型表示,然后引入有限时域的二次目标函数,利用最优控制理论,设计出在无穷时域中容错控制器。为获得最小运行时间,针对不同阶段设计依赖于Lyapunov函数的驻留时间方法。创新之处在于,控制律设计简单,计算量小,且每一阶段时间求取不需要引用任何其他变量,简单易行。最后,以注塑成型过程为例,仿真结果证明所提出方法具有可行性和有效性。 相似文献
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Decentralized control system design comprises the selection of a suitable control structure and controller parameters. Here, mixed integer optimization is used to determine the optimal control structure and the optimal controller parameters simultaneously. The process dynamics is included explicitly into the constraints using a rigorous nonlinear dynamic process model. Depending on the objective function, which is used for the evaluation of competing control systems, two different formulations are proposed which lead to mixed‐integer dynamic optimization (MIDO) problems. A MIDO solution strategy based on the sequential approach is adopted in the present paper. Here, the MIDO problem is decomposed into a series of nonlinear programming (NLP) subproblems (dynamic optimization) where the binary variables are fixed, and mixed‐integer linear programming (MILP) master problems which determine a new binary configuration for the next NLP subproblem. The proposed methodology is applied to inferential control of reactive distillation columns as a challenging benchmark problem for chemical process control. 相似文献
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Wei Wu Yi-Shyong Chou Ching-Tien Liou Yu-Shu Chien 《Chemical Engineering Communications》2000,183(1):187-206
This work concerns the phenomena in which the feedback linearization control is applied to uncertain nonlinear time-delay processes. Under the I/O linearization algorithm, both nonlinear controllers are used to stabilize the closed-loop system with transformed delay inputs. When the effect of input perturbations can converge to zero or asymptotically vanish, these nonlinear feedback designs with only an adjustable parameter can directly improve the tracking performance. The simple linearizing controller can directly regulate the system output at unstable operating point. Combined with deadtime compensation the nonlinear predictive controller with the aid of appropriate state prediction is valid for the real process in the presence of large time delay. Finally, via computer simulation and test of control ability of both feedback control designs the useful comparative results are presented. 相似文献
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Single wafer rapid thermal processing (RTP) is widely used in semiconductor manufacturing. A precisely applied thermal budget during RTP is crucial and relies on the temperature control of the wafer. However, temperature control in the RTP system with a spike-shaped temperature profile is a challenging task, and achieving perfect servo control is almost impossible because of the high temperature ramp-up/down rate and substantial nonlinearity of the process. This paper presents a novel method of control system design to provide a precise thermal budget in the spike RTP system. By tuning controller parameters and designing the set-point profile, the method targets thermal budget indices instead of temperature servo control. A nonlinear control strategy is proposed based on modeling the RTP system as a nonlinear Wiener model. Furthermore, a multivariable control structure is considered to maintain the temperature uniformity within the wafer. The simulation results show the effectiveness of the proposed control strategy and provide helpful guidelines for the design of a multivariable control configuration to achieve superior wafer temperature uniformity. 相似文献
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S. S. E. H. Elnashaie N. F. Mohamed Mai Kamal 《Chemical Engineering Communications》2004,191(6):813-831
A relatively simple model of optimum degree of sophistication for riser-reactor industrial fluid catalytic cracking (FCC) units is developed. An efficient iterative computer code is developed for the solution of the nonlinear two-point boundary value model equations. Sets of data for three industrial units are used to adjust the parameters of the model. Independent sets of data for each unit are used to verify the reliability of the model without any adjustable parameters. The model is used to investigate the static bifurcation behavior and its implications for design, operation, and control. 相似文献
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Baohua Wang Qunsheng Li Zeting Zhang Jinmiao Yang Yancheng Liu 《Korean Journal of Chemical Engineering》2006,23(1):131-137
In this work, a new model based on the Wilson solution theory was proposed for predicting the solubility of solids in supercritical
fluid (SCF) with and without cosolvent(s) of binary and ternary systems via computation of activity coefficients. For binary
systems the model contains two adjustable parameters, while for ternary systems there are four adjustable parameters. The
calculated results of the proposed model were compared with that of the literature models, and it is shown that the proposed
model is a more accurate one. 相似文献
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WEI WU YI-SHYONG CHOU CHING-TIEN LIOU YU-SHU CHIEN 《Chemical Engineering Communications》2013,200(1):187-206
This work concerns the phenomena in which the feedback linearization control is applied to uncertain nonlinear time-delay processes. Under the I/O linearization algorithm, both nonlinear controllers are used to stabilize the closed-loop system with transformed delay inputs. When the effect of input perturbations can converge to zero or asymptotically vanish, these nonlinear feedback designs with only an adjustable parameter can directly improve the tracking performance. The simple linearizing controller can directly regulate the system output at unstable operating point. Combined with deadtime compensation the nonlinear predictive controller with the aid of appropriate state prediction is valid for the real process in the presence of large time delay. Finally, via computer simulation and test of control ability of both feedback control designs the useful comparative results are presented. 相似文献
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S. S. E. H. ELNASHAIE N. F. MOHAMED MAI KAMAL 《Chemical Engineering Communications》2013,200(6):813-831
A relatively simple model of optimum degree of sophistication for riser-reactor industrial fluid catalytic cracking (FCC) units is developed. An efficient iterative computer code is developed for the solution of the nonlinear two-point boundary value model equations. Sets of data for three industrial units are used to adjust the parameters of the model. Independent sets of data for each unit are used to verify the reliability of the model without any adjustable parameters. The model is used to investigate the static bifurcation behavior and its implications for design, operation, and control. 相似文献
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A novel robust optimization framework is proposed to address general nonlinear problems in process design. Local linearization is taken with respect to the uncertain parameters around multiple realizations of the uncertainty, and an iterative algorithm is implemented to solve the problem. Furthermore, the proposed methodology can handle different categories of problems according to the complexity of the problems. First, inequality‐only constrained optimization problem as studied in most existing robust optimization methods can be addressed. Second, the proposed framework can deal with problems with equality constraint associated with uncertain parameters. In the final case, we investigate problems with operation variables which can be adjusted according to the realizations of uncertainty. A local affinely adjustable decision rule is adopted for the operation variables (i.e., an affine function of the uncertain parameter). Different applications corresponding to different classes of problems are used to demonstrate the effectiveness of the proposed nonlinear robust optimization framework. © 2017 American Institute of Chemical Engineers AIChE J, 64: 481–494, 2018 相似文献