利用工业大系统动态信息建立稳态模型及其强一致性分析

本文提出了一种在相当弱的条件下，仅仅利用优化过程中系统设定点例行阶跃变化作为激励信号，对各子系统并行使用简单最小二乘法和近似动态线性模型，充分运用大系统的动态信息，得到了大系统稳态模型的一致估计的理论证明，并利用数字仿真进一步验证了其方法的有效性。还给出了一种实用的，能强一致估计线性渐近定常大系统稳态模型的方法。     

基于神经网络的工业大系统辨识及稳态递阶优化方法

为了对工业大系统进行稳态递阶优化,必须首先获得系统的稳态模型.从神经网络的分 析人手,给出了工业大系统稳态模型的动态辨识方法及基于神经网络模型的推导方法.为了 提高算法的收敛速度,引入Lagrange函数解决大系统优化问题中的各种约束,并用Hopfield 网络实现了大系统稳态递阶优化的网络算法,最后给出了某一大系统辨识及优化的仿真结果.     

工业大系统双层结构预测控制的集中优化与分散控制策略

为降低工业大系统模型预测控制(Model predictive control,MPC)在线计算复杂度,同时保证系统的全局优化性能,提出一种集中优化、分散控制的双层结构预测控制策略.在稳态目标计算层(Steady-state target calculation, SSTC),基于全局过程模型对系统进行集中优化,将优化结果作为设定值传递给动态控制层;在动态控制层,将大系统划分为若干个子系统,每个子系统分别由基于各自子过程模型的模型预测控制进行控制,为减少各子系统之间的相互干扰,在各个子系统之间添加前馈控制器对扰动进行补偿,提高系统的总体动态控制性能.该策略的优点在于能确保系统全局最优性的同时降低了在线计算量,提高了工业大系统双层结构预测控制方法的实时性.仿真实例验证该方法的有效性.     

大工业过程的稳态模型分散辨识及其强一致性分析

针对动态线性大工业过程,提出了获得其可分稳态模型强一致性估计的分散辨识方法.该方法仅使用设定点的阶跃信号作为输入激励信号,并且每个子过程的输入输出稳态模型辨识是在相应的局部单元完成的,因而大大减少了对过程的干扰和信息的交换量.所提出的方法简洁,并且辨识精度高,仿真结果说明了该辨识方法的有效性和实用性.     

带有持续扰动的时滞非线性大系统的最优跟踪控制

研究具有外界持续扰动的时滞非线性大系统的无静差最优跟踪控制问题.将时滞非线性大系统分解为带有互联项的N个时滞非线性子系统,基于内模原理对子系统构造扰动补偿器,将带有外部持续扰动的子系统化为无扰动的增广系统.通过灵敏度法求解不含时滞的两点边值问题,得到子系统的最优跟踪控制律,截取最优跟踪控制律的前N项作为次优控制律来近似系统的最优控制律.仿真实例表明了该设计方法的有效性.     

Optimal tracking control for nonlinear large-scale systems with persistent disturbances

This paper studies the optimal control with zero steady-state error problem for nonlinear large-scale systems affected by external persistent disturbances. The nonlinear large-scale system is transformed into N nonlinear subsystems with interconnect terms. Based on the internal model principle, a disturbance compensator is constructed such that the ith subsystem with external persistent disturbances is transformed into an augmented subsystem without disturbances. According to the sensitivity approach, the optimal tracking control law for the ith nonlinear subsystem can be obtained. The optimal tracking control law for the nonlinear large-scale systems can be obtained. A numerical simulation shows that the method is effective.     

广义系统信息融合稳态与自校正满阶Kalman滤波器

基于线性最小方差标量加权融合算法和射影理论,对带多个传感器和带相关噪声的广义系统,提出了分布式标量加权融合稳态满阶Kalman滤波器.推得了任两个传感器子系统之间的稳态满阶滤波误差互协方差阵,其解可任选初值离线迭代计算.所提出的稳态融合滤波器避免了每时刻计算协方差阵和融合权重,减小了在线计算负担.当系统含有未知模型参数时,基于递推增广最小二乘算法和标量加权融合算法,提出了一种两段融合自校正状态滤波器.其中第1段融合获得未知参数的融合估计;第2段融合获得分布式自校正融合状态滤波器.与局部估计和加权平均融合估计相比,所提出的标量加权融合参数估计和自校正状态估计都具有更高的精度.仿真研究验证了其有效性.     

Design of distributed PID-type dynamic matrix controller for fractional-order systems

With the continuous requirements for product quality and safety operation in industrial production, it is difficult to describe the complex large-scale processes with integer-order differential equations. However, the fractional differential equations may precisely represent the intrinsic characteristics of such systems. In this paper, a distributed PID-type dynamic matrix control method based on fractional-order systems is proposed. First, the high-order approximate model of integer order is obtained by utilising the Oustaloup method. Then, the step response model vectors of the plant is obtained on the basis of the high-order model, and the online optimisation for multivariable processes is transformed into the optimisation of each small-scale subsystem that is regarded as a sub-plant controlled in the distributed framework. Furthermore, the PID operator is introduced into the performance index of each subsystem and the fractional-order PID-type dynamic matrix controller is designed based on Nash optimisation strategy. The information exchange among the subsystems is realised through the distributed control structure so as to complete the optimisation task of the whole large-scale system. Finally, the control performance of the designed controller in this paper is verified by an example.     

Well-posed linear models for large-scale zero-memory composite systems

A class of admissible linear approximate models is determined for large-scale interconnected steady-state systems having structures described by interconnection matrices. With applications in mind, emphasis is laid on fast stabilizability (rapid decay of transient processes) and appropriate insensitivity of system models both to variations in model inputs and model parameters. The set of well-posed linear models is then defined. An accuracy analysis of well-posed linear models is performed, and the computation of an optimum model from the data obtained in an identification experiment by using the Monte Carlo approach is discussed.     

非线性大系统的跟踪具有不同幅值轨线的分散型迭代学习控制器

在大型工业过程递阶稳态优化中, 可行的方法是利用系统的实际信息以修正基于模型的最优解. 在这种情形下, 得出一幅值不等的阶跃型控制值序列, 而且该控制值序列依次激励实际系统. 本文将一组迭代学习控制器分散地嵌入到一类非线性工业过程的递阶稳态优化进程中, 每一子系统的迭代学习控制器将产生一强化的控制信号序列以替代相应的具有不同幅值的阶跃型控制值序列, 目的是不断改进系统的暂态品质. 通过卷积的 Hausdorff-Young 不等式, 本文分析了学习控制律在 Lebesgue-P 范数意义下的收敛性, 讨论了系统的非线性性和关联性对控制律收敛性的影响. 最后, 数字仿真验证了所研究的学习控制机理的正确性和有效性.     

Iterative learning controllers for discrete-time large-scale systems to track trajectories with distinct magnitudes

In the procedure of steady-state hierarchical optimization for large-scale industrial processes, it is often necessary that the control system responds to a sequence of step function-type control decisions with distinct magnitudes. In this paper a set of iterative learning controllers are de-centrally embedded into the procedure of the steady-state optimization. This generates upgraded sequential control signals and thus improves the transient performance of the discrete-time large-scale systems. The convergence of the updating law is derived while the intervention from the distinction of the scales is analysed. Further, an optimal iterative learning control scheme is also deduced by means of a functional derivation. The effectiveness of the proposed scheme and the optimal rule is verified by simulation.     

Adaptive on-line steady-state optimization of slow dynamic processes

A software package OLIOPT was developed for the on-line optimization of the steady-state behaviour of slow dynamic processes in a relatively short time period. In the starting phase, the independently variable inputs are changed according to a special test signal. A nonlinear dynamic process model is identified on-line. Based on the static part of the model and the known inputs, the gradients of the performance index are calculated. An optimization algorithm changes the inputs towards their optimal values. On-line identification of the nonlinear model continues and the prediction of the optimum improves. In the last phase, the inputs take their optimal values and the process follows, feedforward controlled, to its optimal steady-state. The method is suited for industrial processes with one or more variable inputs, where a small gain in efficiency turns out to give a relatively large financial return. Results are shown for the on-line optimization of a thermal pilot process.     

Decentralized PDC for large-scale T-S fuzzy systems

This paper studies the decentralized stabilization problem for a large-scale system. The considered large-scale system comprises of a number of subsystems and each subsystem is represented by a Takagi-Sugeno (T-S) fuzzy model. The interconnection between any two subsystems may be nonlinear and satisfies some matching condition. By the concept of parallel distributed compensation (PDC), the decentralized fuzzy control for each subsystem is synthesized, in which the control gain depends on the strength of interconnections, maximal number of the fired rules in each subsystem, and the common positive matrix P/sub i/. Based on Lyapunov criterion and Riccati-inequality, some sufficient conditions are derived and the common P/sub i/ is solved by linear matrix inequalities (LMI) so that the whole closed loop large-scale fuzzy system with the synthesized fuzzy control is asymptotically stable. Finally, a numerical example is given to illustrate the control synthesis and its effectiveness.     

On a two-level identification scheme of large-scale systems for open-loop steady-state optimization

In this paper an attempt is made to combine the problems of the control and modelling of large-scale systems. Starting from the idea of the model-based (open-loop) solution of the two-layer steady-state optimization problem for the noiseless large-scale system, or one corrupted by slow-varying disturbances, an appropriate two-level identification scheme is derived and discussed. The problems connected with its numerical realization are also stated. The considerations are confined to systems with the cascade structure—typical of most production processes—and to the case when the observations of system input/output signals, from which the system model is determined, are noise-free.     

Monitoring and prediction of big process data with deep latent variable models and parallel computing

Process monitoring and quality prediction are crucial for maintaining favorable operating conditions and have received considerable attention in previous decades. For majority complicated cases in chemical and biological industrial processes with particular nonlinear characteristics, traditional latent variable models, such as principal component analysis (PCA), principal component regression (PCR), partial least squares (PLS), may not work well. In this paper, various nonlinear latent variable models based on autoencoder (AE) are developed. In order to extract deeper nonlinear features from process data, the basic shallow AE models are extended to the deep latent variable models, which provides a deep generative structure for nonlinear process monitoring and quality prediction. Meanwhile, with the ever increasing scale of industrial data, the computational burden for process modeling and analytics has becoming more and more tremendous, particularly for large-scale processes. To handle the big data problem, the parallel computing strategy is further applied to the above model, which partitions the whole computational task into a few sub-tasks and assigns them to parallel computing nodes. Then the parallel models are utilized for process monitoring and quality prediction applications. The effectiveness of the developed methods are evaluated through the Tennessee Eastman (TE) benchmark process and a real-life industrial process in an ammonia synthesis plant (ASP).     

Non-linear system identification using the Hammerstein model

An algorithm for the identification of non-linear systems which can be described by a Hammerstein model consisting of a single-valued non-linearity followed by a linear system is presented. Cross-correlation techniques are employed to decouple the identification of the linear dynamics from the characterization of the non-linear element. These results are extended to include the identification of the component subsystems of a feedforward process consisting of a Hammerstein model in parallel with another linear system.     

大规模工业过程非凸稳态优化控制的两级协调法

针对具有输出关联不等式的束和非凸目标函数的大规模工业过程稳态优化控制问题，提出一种全新的两级协调求解算法。该算法由三层构成，上层和中层是两个协调器，下层是各局部决策单元。在较弱的条件下，获得了算法的全局收敛性定理。数字仿真结果表明了该算法的有效性和实用性。     

Closed-loop identification of multivariable processes with part of the inputs controlled

In many multivariable industrial processes a subset of the available input signals is being controlled. In this paper it is analysed in which sense the resulting partial closed-loop identification problem is actually a full closed-loop problem, or whether one can benefit from the presence of non-controlled inputs to simplify the identification problem. The analysis focuses on the bias properties of the plant estimate when applying the direct method of prediction error identification, and the possibilities to identify (parts of) the plant model without the need of simultaneously estimating full-order noise models.