带积分的模糊Smith预估器在电加热温度控制中的应用

传统的smith预估器是解决大纯滞后系统控制的有效方法,但它依赖于被控对象精确的数学模型,使应用受到了限制。带积分的模糊smith预估器兼有前者的特性,又不依赖于对象精确的数学模型,且有较强的鲁棒性。论文给出了设计方法及在电加热炉中的应用结果。     

Enhancing the performance of parallel cascade control using Smith predictor

Parallel cascade controllers are used in chemical processing industries to improve the dynamic performance of a control system in the presence of disturbances. In the present work, a delay compensator has been incorporated in the primary loop of the parallel cascade control system. The secondary controller is designed using the internal model control (IMC) method. The primary controller is designed based on a direct synthesis method for the delay-free system. Design of controllers for slow (when the secondary loop dynamics is slow i.e. process contains poles sufficiently slower than the desired closed loop response) as well as fast dynamics (when the inner loop dynamics is fast i.e. process contains poles sufficiently faster than the desired closed loop response) of the secondary process is considered. The method provides robust control performances. Significant improvement in the closed loop performances are obtained with the delay compensator over that of a conventional parallel cascade control system. Several case studies are considered to show the advantage of the proposed method when compared to other recently reported methods.     

自适应Smith预估器仿真研究

Ｓｍｉｔｈ预估器是一种有效的大纯滞后补偿机制,但它的弱鲁棒性限制了它在工程实际中的应用。本文对Ｓｍｉｔｈ预估器的鲁棒性进行了仿真研究,并针对它的缺陷引入了自适应机制,即通过对被控过程的在线辨识获得满足Ｓｍｉｔｈ预估器精度要求的过程数学模型,最后通过仿真实例给出了自适应Ｓｍｉｔｈ预估器系统的控制效果。     

Delay-dependent guaranteed-cost control based on combination of Smith predictor and equivalent-input-disturbance approach

This paper presents a new system configuration and a design method to improve control performance for a system with an input time delay and disturbances. The equivalent-input-disturbance approach is extended to handle a time-delay system. It is combined with the Smith predictor to reject disturbances. A delay-dependent stability condition is devised in terms of a matrix inequality by using the free-weighting matrix approach. The gain of the observer is designed by applying the cone complementary linearization method to the matrix inequality. A numerical example demonstrates the validity of the method.     

基于结构改进Smith预估单神经元PSD的长时延NCS研究

针对长时延网络控制系统（NCS）中存在时延和被控对象等问题,提出了一种新型结构改进Smith预估单神经元PSD控制器.新型控制器由结构改进Smith预估器和单神经元PSD控制器组成,结构改进Smith预估器通过对传统Smith预估器模型结构上的改进,避免了建立网络时延的预估模型,无需对网络时延进行在线测量、估计或辨识,补偿了网络时延对系统的性能带来的影响;单神经元PSD控制器解决了结构改进Smith预估器的模型失配问题,通过Matlab环境下的TrueTime工具箱对NCS进行仿真实验,并对传统PID控制方法、结构改进Smith预估PID控制方法和结构改进Smith预估单神经元PSD控制方法进行了仿真比较.研究结果表明,该新型控制器有效地补偿了网络时延对NCS的性能带来的影响,在模型失配情况下具有良好的鲁棒性和适应性,是对长时延NCS-种可行且有效的控制方法.     

基于模糊控制的Smith预估器的研究和设计

本文介绍了Smith预估控制原理,针对Smith预估器对象模型误差过于敏感的缺点,引入模糊控制代替Smith预估器中的PI控制,Matlab仿真结果表明采用模糊Smith预估控制一定程度上改进了常规PI Smith预估控制和模糊控制的缺点。     

Varying time delay Smith predictor process controller

One of the perceived weaknesses of the classical Smith predictor is that the time delay is fixed. For systems with a varying time delay, underestimating or overestimating the time delay significantly degrades control quality. This paper presents theoretical and practical results of applying the Smith predictor with a varying time delay when the nature of the application allows the time delay to be practically computed in real time.     

New tuning rules of PI-like controllers with transient performances for monotonic time-delay systems

In this note, new tuning methods for Proportional-Integral (PI) are proposed for monotonic time delay systems. Like the Ziegler–Nichols method, the proposed technique requires only parameters obtained from the plant step response. Unlike conventional techniques, the resultant tuning parameters offer the advantage of obtaining stable response with prescribed dynamic behavior with relation to the maximum overshoot. The idea of the design is simple and relies on basics learned in an introductory control course.     

PID控制器参数快速整定的新方法

本文分析了影响控制器参数整定的几个基本问题（控制目标、优化准则和被控过程的特性），提出了精确地确定被控过程模型参数的方法。通过计算机仿真，系统地提出了可适用于多容过程的ＰＩＤ控制器参数快速整定新方法。     

Modified Smith predictor design for periodic disturbance rejection

In this paper, a modified Smith predictor control scheme is proposed for periodic disturbance rejection in both stable and unstable processes with time delay. Without affecting the superior setpoint response of Smith predictor control, the regulation performance under periodic disturbance can be enhanced significantly by the proposed design. Meanwhile, the asymptotical rejection for non-periodic disturbance will also be improved. Internal stability is investigated for a closed-loop control system. The effectiveness of the proposed scheme will be demonstrated by simulations as well as a test on an experimental thermal system.     

Smith predictor based-sliding mode controller for integrating processes with elevated deadtime

An approach to control integrating processes with elevated deadtime using a Smith predictor sliding mode controller is presented. A PID sliding surface and an integrating first-order plus deadtime model have been used to synthesize the controller. Since the performance of existing controllers with a Smith predictor decrease in the presence of modeling errors, this paper presents a simple approach to combining the Smith predictor with the sliding mode concept, which is a proven, simple, and robust procedure. The proposed scheme has a set of tuning equations as a function of the characteristic parameters of the model. For implementation of our proposed approach, computer based industrial controllers that execute PID algorithms can be used. The performance and robustness of the proposed controller are compared with the Matausek-Mici? scheme for linear systems using simulations.     

用单片机实现窑炉温度模糊自适应Smith预估控制

本文根据烧结磁性元件窑炉温度控制的需要,采用模糊自适应Smith预估控制方法,将模糊控制、自适应控制与Smith预估控制之长处综合在一起,在一定程度上弥补上述三者各自的不足。通过仿真和实时运行,温度稳定在1300℃±2℃,烧结的磁性元件特性均匀,取得了满意的结果。     

基于遗传算法的多PID控制器参数整定

为了解决多入多出系统和采用状态控制的单入单出系统的多PID控制器参数整定困难的问题，本文提出了基于遗传算法的多PID控制器参数整定方法，该方法只需给出大概的PID参数范围即可得到控制性能最优的PID参数，本文结合实例证实了该方法的有效性。     

Smith预估模糊PID控制算法及其在粉末定量称重中的应用

针对上海科源电子科技有限公司研发的定量称重系统（由高精度抖粉装置与万分之一天平组成）,在工作中因粉末密度、粉末流动性、颗粒大小、湿度、天平延时等因素造成的非线性和滞后等问题,采用Smith预估模糊PID控制器优化控制方法。首先通过理论分析,得出系统的传递函数,再构建Smith预估的模糊PID控制器,以适应系统的非线性、滞后等特性,最后将此算法代入MATLAB进行仿真并于实际系统中进行1 g定量抖粉实验。Smith预估模糊PID控制算法和传统PID算法的标准差分别为0.0020和0.0042,表明Smith预估模糊PID控制算法在实际环境中稳定性更好,能有效减小系统的称重误差。     

基于建模误差估计的Smith补偿器鲁棒稳定化自动整定算法

本文针对Ｓｍｉｔｈ补偿器研究实现其参数自动整定的方法。通过辨识过程在特定频段上的响应信息估计建模误差的大小,并将其转化为模型参数摄动进行控制器参数的鲁棒稳定化设计。同时给出了针对有关参数摄动鲁棒稳定化设计的一个新充分性判据。仿真结果表明了算法良好的控制效果与可实现性。     

On the selection of tuning methodology of FOPID controllers for the control of higher order processes

In this paper, a comparative study is done on the time and frequency domain tuning strategies for fractional order (FO) PID controllers to handle higher order processes. A new fractional order template for reduced parameter modelling of stable minimum/non-minimum phase higher order processes is introduced and its advantage in frequency domain tuning of FOPID controllers is also presented. The time domain optimal tuning of FOPID controllers have also been carried out to handle these higher order processes by performing optimization with various integral performance indices. The paper highlights on the practical control system implementation issues like flexibility of online autotuning, reduced control signal and actuator size, capability of measurement noise filtration, load disturbance suppression, robustness against parameter uncertainties etc. in light of the above tuning methodologies.     

Autotuning of a new PI-PD Smith predictor based on time domain specifications

The paper extends a recent work on a modified PI-PD Smith predictor, which leads to significant improvements in the control of processes with large time constants or an integrator or unstable plant transfer functions plus long dead time for reference inputs and disturbance rejections. Processes with high orders or long time delays are modeled with lower order plant transfer functions with longer time delays. The PI-PD controller is designed so that the delay-free part of the system output will follow the response of a first-order plant or second-order plant, where it is appropriate, assuming a perfect matching between the actual plant and model in both the dynamics and time delay. The provided simple tuning formulas have physically meaningful parameters. Plant model transfer functions and controller settings are identified based on exact analysis from a single relay feedback test using the peak amplitude and frequency of the process output. Examples are given to illustrate the simplicity and superiority of the proposed method compared with some existing ones.     

Analytical design of modified Smith predictor in a two-degrees-of-freedom control scheme for second order unstable processes with time delay

A modified form of Smith predictor is designed for controlling unstable second order plus time delay (USOPTD) processes, with/without a zero. USOPTD process transfer functions arise in modeling of many chemical and biological systems, such as isothermal continuous stirred tank reactors (CSTR) carrying out autocatalytic reactions, crystallizers and non-isothermal CSTRs. The modified Smith predictor scheme requires the design of three controllers. Synthesis method is used for the design of the three controllers, and analytical formulas are given for these controllers. The method has two tuning parameters, and guidelines are provided for selecting the tuning parameters. Robust disturbance rejection performances are achieved. Different examples are considered, and simulation studies are given, to show the effectiveness of the proposed method. A significant improvement is obtained, when compared with recently reported methods.     

The generalized forced oscillation method for tuning PID controllers

In this paper a generalized tuning methodology for proportional–integral–derivative (PID) controllers is proposed. The methodology is akin to the Ziegler–Nichols forced oscillation method, inheriting fully its practical appeal, but can be applied to much more general classes of plants. This generalization is achieved by employing a relay with adjustable phase (RAP) in a relay feedback experiment, and the tuning consists of formulas based on measurements obtained from this experiment. Experimental results in a liquid processing plant with of-the-shelf industrial equipments illustrate the performance of the methodology and the practical procedures involved in its application, which can be fully automated.     

大纯滞后系统的模糊-Smith控制及参数优化

分析了采用常规Smith预估器的大纯滞后系统控制性能不佳的原因以及常规模糊控制的不足，研究一种适合大纯滞后系统的改进的模糊-Smith控制器，并用遗传算法对其参数进行寻优。仿真实验表明，改进的模糊-Smith控制器具有很好的品质特性和良好的鲁棒性。