On-line process identification and PID controller autotuning

We propose a new and simple on-line process identification method for the automatic tuning of the PID controller. It does not require a special type of test signal generators such as relay or P controller only if the signals are persistently exciting. That is, a user can choose arbitrary signal generators such as relay, a P controller, the controller itself, pulse signal and step signal generator because it needs only the measured process output and the controller output. It can incorporate nonlinearities due to actuator saturation or manual mode operation during identification work and shows a good robustness to measurement noises, nonlinearity of the process and disturbances. The proposed autotuner combined with the identification method and tuning rule using a model reduction shows good control properties compared with previous autotuning methods.     

Control of pH processes based on the genetic algorithm

In this work, we propose a PID control strategy based on the genetic algorithm coupled with cubic spline interpolation method for the control of pH processes. The control scheme proposed in the present work consists of closed-loop identification based on the genetic algorithm and cubic spline method. First, we compute the parameters (K_C, Τ_I, Τ_D) of the PID controller using relay feedback and apply these parameters to control the pH Process. Then approximate linear models corresponding to each pH range are obtained by the closed-loop identification based on closed-loop operation data. The optimal parameters of the PID controller at each pH region are then computed by using the genetic algorithm. From numerical simulations and control experiments we could achieve better control performance compared to the conventional fixed gain PID control method. This paper is dedicated to Professor Hyun-Ku Rhee on the occasion of his retirement from Seoul National University.     

微结构注塑机注射速度控制及仿真研究

为了对注射速度进行精密控制,建立起一个液压控制系统,对该系统中影响注射速度的相关器件进行结构分析并且建立数学模型,针对注射速度非线性以及时变等特性,设计一种自适应模糊PID控制器,利用MATLAB软件建立仿真模型,对两种控制器下的注射速度曲线进行对比分析。结果表明,与传统PID控制器相比,自适应模糊PID控制器具有注射速度响应更迅速,稳态无误差和鲁棒性能好等优势。     

区间二型模糊免疫PID在环己烷无催化氧化温度控制系统中的应用

环己烷无催化氧化过程具有非线性、多变量耦合、大时滞等特点,使用常规比例积分微分(PID)控制方案无法达到理想的控制性能。提出了一种区间二型模糊免疫PID控制器,其本质上是一种基于免疫PID的非线性控制器,利用区间二型模糊逻辑系统来逼近免疫反馈律中的非线性函数,以提升控制器处理和逼近复杂不确定非线性系统的能力。将所提出的控制器应用于环己烷无催化氧化温度控制系统,仿真结果表明该方法是有效的。     

SOME THEORETICAL INSIGHTS INTO RECENT CONTROL DESIGN ALGORITHMS

Internal Model Control (IMC) design procedure is known to offer valuable advantages over classical control methods, especially for robust controller design. The Perfect Controller is defined using the well-known classical PID algorithm and its equivalence to IMC. After the definition of the Perfect Controller the IMC filter tuning parameter, which is used to maintain robustness, is obtained as a result of reparametrization of the classical PID control algorithm and factorization of the model. Through factorization, invertible part of the model is used directly in defining the perfect controller and the noninvertibility effects of the model are lumped into the new IMC tuning parameter. Closed loop IMC controller design is obtained with appropriate plant parameter uncertainty representation. Theoretical foundation for the transition from classical PID design to IMC design is analyzed using simple common chemical process models.     

区间二型模糊免疫PID在环己烷无催化氧化温度控制系统中的应用

环己烷无催化氧化过程具有非线性、多变量耦合、大时滞等特点,使用常规比例积分微分(PID)控制方案无法达到理想的控制性能。提出了一种区间二型模糊免疫PID控制器,其本质上是一种基于免疫PID的非线性控制器,利用区间二型模糊逻辑系统来逼近免疫反馈律中的非线性函数,以提升控制器处理和逼近复杂不确定非线性系统的能力。将所提出的控制器应用于环己烷无催化氧化温度控制系统,仿真结果表明该方法是有效的。     

基于继电反馈的辨识的研究

详细论述继电反馈技术在模型辨识中的应用,阐述各种继电反馈辨识方法的原理与优缺点。在此基础上,分析继电反馈辨识技术今后可能的发展方向。     

A new predictive PID controller for the processes with time delay

A new proportional-integral-derivative (PID) controller is proposed based upon a simplified generalized predictive control (GPC) control law. The tuning parameters of the proposed predictive PID controller are obtained from the simplified GPC control law for the 1 ^st -order and 2 ^nd -order processes with time delays of integer and non-integer multiples of the sampling time. The internal model technique is employed to compensate the effect of time delay of the target process. The predictive PID controller is equivalent to the PI controller when the target process is 1 ^st -order and to the PID controller when the target process is an integrating process. The performance of the proposed predictive PID controller is almost the same as that of the simplified GPC. The main advantage of the proposed control scheme over other control methods is the ease of tuning and operation.     

典型大时变时滞系统神经网络模糊PID控制及应用

针对典型大时变时滞系统,设计了一种基于神经网络的模糊PID控制器.该控制器综合模糊逻辑、神经网络与PID调节的各自优点,既具有模糊控制简单和有效的非线性控制作用,又具有神经网络的学习和适应能力,同时还具备PID控制的广泛适应性.该控制器能实现系统参数大范围失配情况下的闭环鲁棒稳定,并使闭环系统达到设定值无静差跟踪及满意的动态性能.     

基于神经网络和多模型的非线性自适应PID控制及应用

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。     

Assessment of controller performance: a relay feedback approach

Assessment of control loop performance is one of the important tasks to be carried out in a plant, regardless of the control strategy. The present work utilizes the shape information from single relay feedback test to assess the performance of a feedback system. The process considered is a typical first-order plus dead time process and the controller used is PI type of controller. An ideal relay is introduced in the feedback loop before the controller. The shape of the relay output characterizes the performance of the controller. The mismatch in the integral time can also be observed from the shape. Based on the shape information, analytical expressions for relay feedback responses are derived and straightforward procedures are evolved to assess the performance of the controller. The proposed scheme assesses the controller performance and computes the new tuning parameters, in case retuning of the controller is necessary. The robustness of the method is also tested for second-order plus dead time as well as for higher order systems. More importantly the present approach employs only one relay test for (1) assessment and (2) retuning of the controller. It provides a reliable way that is compatible even to a non-expert operator to assess the controller performance.     

模糊PID控制器的发展

将模糊控制技术和PID控制相结合，可克服常规PID控制器的不足，使PID控制器具有参数自适应能力。介绍了模糊控制器和PID控制器间的关系，从一维、二维及三维模糊控制器的输入－输出形式上，以及解析分析角度出发，可以说模糊控制器人本质上讲是一种非线性PID控制器。还总结了模糊PID控制器的结构。模糊PID控制器可分成两大类，一类由参数可变的PID控制器及一个模糊控制器共同构成，模糊控制器用于完成PID参数的在线整定，控制信号仍由PID控制器生成；另一类直接用模糊控制器来构造、实现PID控制功能。分别归纳了这两类控制器的多种结构形式。最后还对模糊PID控制器的发展进行了展望，提出了模糊PID 控制器结构的选择、控制器参数调整及控制器评价标准的确定这几方面是今后工作的重点。     

连续搅拌釜式反应器的鲁棒最优控制

针对一类带不确定性的连续搅拌釜式反应器,提出基于滑模控制理论的鲁棒最优控制算法。输入输出线性化方法用于线性化对象模型,假设系统的不确定因素有界,滑模面采用积分型滑模面以确保系统稳态误差为零,将线性二次型理论用于等效控制律的设计中,保证了系统的性能指标最优,自适应滑模切换控制增益的选取在降低系统抖振的前提下补偿了系统的不确定因素及外部扰动,实现了控制器的鲁棒最优。通过仿真实验表明,提出的控制器对匹配的不确定性因素及外部扰动具有鲁棒性,且闭环系统的性能指标最优。     

Process operation near an unstable steady state using nonlinear feedback control

Process performance is sometimes best at an unstable steady state. Following a new control philosophy, stable operation near an unstable steady state can be realized using a relay with hysteresis as a feedback controller. Properly designed, this control scheme produces a stable, small amplitude oscillation in the neighborhood of the desired state. Approximate solutions for such oscillations can be obtained by Tsypkin's method or Describing Function analysis. Comparisons of these solutions with exact simulation results for an example reveal that replacing the relay with the describing function is a major source of error in the approximate analysis.     

计量泵行程调节的鲁棒非脆弱PID控制器设计

This job focuses on the stroke regulation of a class of high-precision metering pumps.A parametertuning method of robust non-fragile PID(proportional-integral-derivative)controllers is proposed with the assumption that a PID controller has additive gain perturbations.An H-infinite robust PID controller can be obtained by solving a linear matrix inequality.This approach can guarantee that the closed-loop control systems is asymptotically stable and the H-infinite norm of the transfer function from the disturbance to the output of a controlled system is less than a given constant to attenuate disturbances.The simulation case shows that the control performance of the proposed strategy is significantly better than the traditional PID approach in the situation with perturbations of controller parameters.     

不稳定时滞过程PID控制器时域直接设计法

直接在时域上设计不稳定时滞过程比例积分微分(PID)控制器.采取双回路三环节的控制结构,满足时域指标-阻尼系数的要求,并对积分增益进行优化.首先设计出满足时城指标要求的理想PID控制器,然后将微分运算等效移动到内部反馈支路,最后合并3个环节得到设定值加权PID控制嚣.仿真表明该方法是有效的,所整定的控制系统具有好的鲁棒...     

Polypropylene degradation control during reactive extrusion

In this work, a proportional‐integral‐derivative (PID) control scheme with two different tuning methods to control the degree of degradation of polypropylene (PP) during reactive extrusion is proposed. The concentration of dicumyl peroxide is taken as the manipulated variable. The molten viscosity of PP under processing is taken as the controlled variable. The degree of degradation is determined by a viscosity function derived by an off‐line identification. A first‐order‐plus‐time‐delay empirical model is identified to simulate the system plant. Both Ziegler–Nichols tuned PID and internal model control (IMC)‐based PID controllers are implemented on the system. Better performances in settling time and precision can be achieved using the IMC‐based PID controller. © 2004 Wiley Periodicals, Inc. J Appl Polym Sci 95: 280–289, 2005     

Nonlinear adaptive switching control for a class of non-affine nonlinear systems

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.     

FUZZY GAIN SCHEDULED CSTR WITH GA-BASED PID

In this article, a new control scheme, the gain scheduled genetic algorithm (GA)-based PID is proposed for a continuous stirred tank reactor (CSTR). A CSTR is a highly nonlinear process that exhibits stability in certain regions and instability in other regions. The proposed control scheme implements the characteristics of the genetic algorithm's (GA) global optimization to optimize the PID's three control parameters, k_p, k_i, k_d, to obtain the best control effect by minimizing the integral square error online. The PID controller parameters tuned by the GA for each region are gain scheduled by a fuzzy logic scheduler. Fuzzy gain scheduling is a special form of fuzzy control that uses linguistic rules and fuzzy reasoning to determine the controller parameter transition policy for the dynamic plant subject to large changes in its operating state. Simulation results show the feasibility of using the proposed controller for the control of the dynamical nonlinear CSTR.     

湿磨干烧水泥生产线分解炉温度控制

湿磨干烧水泥生产线的分解炉中生料量波动大,利用HoneywellC200系统自带的带规PID无法满足温度控制工艺要求,本工作利用线性神经元参数自学习PID控制和前馈控制,通过Control Build编制成控制模块,下载到底层控制器实现温度控制,与利用API函数编制用户算法在上层计算机上运行相比,该方案克服了采样和控制周期受计算机负菏影响而变化的缺陷,而不受通讯影响,实际应用结果表明了本文提供出的控制方法的有效性。