基于二次型性能指标的不确定混沌系统最优控制器设计

研究具有不确定性并带有扰动的混沌控制系统。首先基于成熟线性理论中的二次型最优控制理论将扰动非线性的混沌系统模型转换为无扰动的等价线性系统模型,然后给出了针对伪线性系统的基于二次型性能指标的最优控制器设计方法。对Liu混沌系统的参数不确定性的仿真结果表明：控制品质有了较大的改善和提高。     

非线性液位系统的反馈线性化控制

为了更好地研究非线性液位系统在工作点大范围变化时的控制问题,对A3000过程控制装置中非线性单容水箱的液位控制进行了研究。建立了精确的单容水箱模型,提出了一套基于传统PID控制的反馈线性化控制方案,并在Freelance 800F DCS中成功进行了组态和调试,验证了反馈线性化控制方案在非线性液位系统中的可行性和优越性。     

吹气式液位控制系统在浮选柱液位控制中的应用

液位控制是提高浮选柱分选效率的重要因素。介绍吹气式液位控制系统工作原理及几种常用液位控制系统在大型浮选柱液位控制中的应用情况。结果表明,双吹气管液位控制系统适应性强,液位控制准确,操作维护简单,适宜浮选柱的液位控制。     

锅炉液位PID控制系统的设计

以Rockwell实验室的过程控制实验装置为实验平台,使用Rockwell公司的MicroLogix1500可编程控制器及其梯形图开发软件RSLogix500对锅炉液位控制系统进行控制,完成了锅炉液位PID控制系统的设计.并说明了锅炉液位控制系统的设计的过程和方法及其中的技术要点.     

调节器参数对单回路液位控制系统的影响分析

以贮罐液位控制系统为例,讨论不同调节器参数对液位控制系统过渡过程的影响并得出结论:单回路液位控制系统能够抵制施加在系统上的干扰因素,系统过渡过程具有过渡时间较小、最大偏差较小、系统稳定性较高等特点,采用单回路比例积分控制系统即可抵制干扰因素对液位的影响,能满足一般生产工艺对液位过程控制的要求.     

KMM调节器在锅炉液位调节中的应用

以75t循环硫化床锅炉控制系统中的汽包液位三冲量调节为例,介绍了KMM可编程调节器在锅炉液位中的控制原理及系统的组态。应用效果表明,汽包液位调节质量高,系统运行正常。     

过氧化氢包装计量技术改造

在普通台秤手动重量计量法基础上，增加贮罐液位控制系统和平衡罐，设计了自动加料控制系统，提高了计量精度，见到了明显的社会经济效益。     

常压系统常二线汽提塔液位控制分析及其故障处理

液位测量在化工工业中具有重要地位,它准确测量塔罐等容器的液位,通过自动控制系统使液位控制在规定的范围内,以保证装置正常操作和平稳运行。本文分析介绍常二线汽提塔液位控制系统,即简单控制系统,通过分析其液位控制系统的组成,进而分析液位控制系统产生的故障以及排除故障的方法,并对其常见故障提出相应的解决措施。     

CO2压缩机表面冷凝器液位控制的改造

介绍了尿素装置CO2压缩机表面冷凝器液位在生产运行过程中存在的一些实际问题;从现场仪表和控制系统两方面进行了改造.改造后,提高了CO2压缩机表面冷凝器液位控制的稳定性,真正实现了液位的自动控制.     

Multi-variable Predictive Control Technology for Aromatics Benzene Tower Control System

介绍了多变量预测控制技术在兰州石化公司芳烃抽提先进控制系统中的应用,对利用多变量预测控制技术控制精馏单元苯塔灵敏板温度、塔顶温差、回流罐液位的策略和方案做了研究,评估了多变量预测控制技术在先进控制系统中的应用效果和产生的经济效益.     

NONLINEAR HEAT EXCHANGER CONTROL THROUGH THE USE OF PARTIALLY LINEARIZED CONTROL VARIABLES

The use of partial linearization by nonlinear state variable feedback has been proposed as a means of reducing the detrimental effects of system nonlinearities upon the performance of linear control schemes used with nonlinear systems. In this paper a set of generalized transformed variables are derived for a single pass shell and tube heat exchanger using this technique. The implementation of these generalized transformed variables, which reduce the apparent nonlinear behavior of single pass heat exchangers, eliminates the need to rederive a nonlinear transformation for each heat exchanger controller design. As shown by open loop transient behavior of the system, the transformed variables reduce the nonlinear characteristics of the system response. The closed loop performance of the heat exchanger system has been evaluated for both servo and regulator control, and the effect of model error upon the robustness of the closed loop controller performance has been investigated.     

A DIRECT NONLINEAR ADAPTIVE CONTROL OF STATE FEEDBACK LINEARIZABLE SYSTEMS

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.     

On constrained infinite-time nonlinear optimal control

In this work, we consider the infinite-time optimal control of input affine nonlinear systems subject to point-wise in time inequality constraints on both the process inputs and outputs. Fundamental to solving this constrained infinite-time nonlinear optimal control (CITNOC) problem is the ability to calculate the value function of it's unconstrained counterpart, the infinite-time nonlinear optimal control (ITNOC) problem. Unfortunately, the traditional ITNOC solution procedure of specifying an objective function and then solving for the optimal control policy and corresponding value function is computationally intractable in all but the simplest of examples. However, in many cases one can easily identify a stabilizing feedback for near operating point regulation. Building from this local policy, the proposed method is to construct a meaningful optimal control objective function as well as its corresponding value function. These functions are then used to analyze the closed-loop stability of the proposed policy. Upon return to the constrained case the constructed objective and value functions are again used to develop a self-consistent constrained finite-time scheme that will, for the first time, provide an exact solution to the CITNOC problem. The mechanics of the proposed method are then illustrated by an example from chemical reactor control.     

ROBUST CONTROL OF BATCH REACTORS

The design of robust nonlinear feedback controller is analysed for a trajectory tracking in a single-input single-output nonlinear state variable system x = f(x) + g(x)u, y=cx which arises in nonlinear chemical processes particularly in batch reactor control problems. Simulation results for the batch reactor temperature tracking problem show the effectiveness of the control scheme and its robustness to modelling errors. The method is also applicable to multi-input multi-output system where the number of inputs is equal to that of outputs. The controller design is also analyzed for situations wrier: the kinetics, the activation energy and Ihe heat of reaction are unknown and also only limited measurement of state-variables are available. The method of Youcef-Toumi and Ito (1987) is applied to such problems and the effectiveness of control system is shown by simulation.     

受扰动非线性系统的反馈线性化最优控制

研究具有外界扰动作用下的非线性系统基于状态反馈精确线性化的最优控制器设计问题。首先基于微分同胚将受扰动非线性系统模型转变为无扰动的伪线性系统模型,然后给出了在关系度等于系统阶数情况下基于二次型性能指标的最优控制器设计方法,通过求解Riccati方程得到系统最优扰动抑制控制律。最后通过仿真实例表明了该方法的有效性。     

BIFURCATION ANALYSIS OF MULTIVARIABLE FEEDBACK CONTROL SYSTEMS

The closed-loop dynamic behavior of nonlinear, multivanable systems is often unpredictable due to complex internal structures unaccounted for by linear control theory. Bifurcation analysis is used to explore the characteristics of such systems governed by linear feedback control. Two new theorems are presented concerning the local stability of a broad class of nonlinear, multivanable systems utilizing Proportional and Proportional-Integral control. A dynamic simulation of a binary distillation column reveals a number of interesting phenomena including limit cycle behavior in asymptotically stable areas of the controller gain space and steady-state multiplicity if a controller gain has the wrong sign.     

化学反应器的神经元自适应观测和非线性控制

提出了一种基于神经网络的自适应观测和非线性控制策略,证明了自适应观测器的收敛件和非线性控制系统的稳定性,将其用于连续搅拌釜式放热反应器的浓度控制。根据可在线测量的反应温度,在线估计不可在线测量的反应物浓度和辨识Arrhenius指前因子,并利用重构的状态信息设计出带约束的非线性控制策略。仿真结果表明,观测器/控制器的组合提供了满意的闭环特性,证实了本文方法的有效性。     

CONTROL AND ESTIMATION FOR PERTURBED NONLINEAR PROCESSES WITH DEADTIME

Feedback linearization techniques are used to deal with the nonlinear controller designs which have attracted many researchers' attention in recent years. The approach has been applied successfully to solve a number of practical nonlinear control problems, but typically requires on-line full state measurement which is usually not the case in real chemical process industries. In this paper, we address the problem of synthesizing nonlinear state feedback controllers for time-delay nonlinear systems which are perturbed by disturbances. On-line estimation of the unmeasurable disturbances and unavailable state variables is introduced to facilitate the implementation of coordinate transformations and state feedback and prediction. Two kinds of dynamic compensators are then proposed to handle the process deadtime. Finally numerical simulations in a CSTR example demonstrate the promising performance of the overall nonlinear control structure in disturbance rejection.     

FEEDBACK LINEARIZATION DESIGNS FOR UNCERTAIN NONLINEAR TIME-DELAY PROCESSES: A COMPARATIVE STUDY

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.     

AN EXOTHERMIC CONTINUOUS STIRRED TANK REACTOR IS FEEDBACK EQUIVALENT TO A LINEAR SYSTEM

This brief paper demonstrates the concept of linear feedback equivalence for an exothermic eontinu-ous stirred tank reactor with first order kinetics. Feedback control is achieved by finding a transformation for the nonlinear system which carries this system into a linear controllable system in Brunovsky canonical form. A linear state feedback controller is then designed which achieves control over a broad range of operating conditions. This example demonstrates how recent developments in nonlinear control theory can be applied to chemical systems without relying on the usual methods of local linearization.