Dead-Time Pseudo-Compensation for Improvement of Accurate Characteristics of a Continuous Control System with Correction According CP a Smith Predictor

This paper describes the use of a cascade compensator constructed according to a Smith scheme in the forward loop of a system being designed for the purpose of analyzing the quality of processes in steady states. This can be effectively used to solve the problem of providing the system with a required reserve of stability by placing a dead-time element outside a closed loop. The dead-time effect manifests only when the transient time increases by the value of dead time with no changes in the overshoot value. It is determined that the velocity Q-factor of the system with a cascade compensator constructed according to a Smith scheme theoretically cannot be larger than the reciprocal of the dead time. This paper also demonstrates the possibility of reducing this negative property of the cascade compensator constructed according to a Smith scheme by dead-time pseudo-compensation with the use of differentiating elements.     

Unified dead-time compensation structure for SISO processes with multiple dead times

This paper proposes a dead-time compensation structure for processes with multiple dead times. The controller is based on the filtered Smith predictor (FSP) dead-time compensator structure and it is able to control stable, integrating, and unstable processes with multiple input/output dead times. An equivalent model of the process is first computed in order to define the predictor structure. Using this equivalent model, the primary controller and the predictor filter are tuned to obtain an internally stable closed-loop system which also attempts some closed-loop specifications in terms of set-point tracking, disturbance rejection, and robustness. Some simulation case studies are used to illustrate the good properties of the proposed approach.     

一种新型增益自适应Smith预估器

在Smith预估器的基础上加入增益自适应，构成了一种新型增益自适应Smith预估器，并针对一阶惯性加纯时滞过程,给出了增益自适应算法。对一阶惯法和二阶惯性加纯时滞过程进行了仿真。结果表明，新型增益自适应预估器对模型结构与参数的精度均无过高的要求，从而有很高的应用价值。     

不锈钢冷轧机AGC系统的模型参考自适应预估控制

针对具有纯时间延迟特性的反馈式AGC(Automatic Gauge Control)系统,依据Smith预估器对纯时间延迟具有补偿作用的原理,给出了模型参考自适应Smith预估器反馈式AGC控制方案并进行了MATLAB仿真。iba-PDA系统记录数据表明:含有模型参考自适应Smith预估器的反馈式AGC系统对森吉米尔冷轧机出口厚度偏差控制具有很好的控制效果,补偿了传统PI厚度反馈控制存在的纯时间延迟,系统自适应调节响应速度加快,能够消除模型参数不完全匹配产生的影响,具有工程应用价值。     

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。     

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.     

Robust and nominal stability conditions for a simplified model predictive controller

A new condition is derived that guarantees robust stability for a set of stable, linear time-invariant plants controlled by using a simplified model predictive control algorithm (SMPC). Discrete single-input-single-output control systems are considered in this paper. Uncertainty is treated in the time domain by considering the stabilization of a set of pulse response functions. The method presented is suitable for stabilizing a set of plants that are not necessarily related. Central to this method is a bounding function, which is a function of the model and controller parameters. The bounding function is designed to have a larger magnitude than all of the pulse response functions in the set of plants to be stabilized. Using this method, it was found that the bounding function is monotonically decreasing when a first-order plus dead-time model is used to design the controller. This allows the coincidence point used in SMPC to be employed directly as a tuning "knob" for robustness, and also simplifies the analysis for dead-time uncertainty. In addition, a comparison of two nominal stability conditions is provided.     

Analytical design and analysis of mismatched Smith predictor

In this paper, an analytical design method is developed for the mismatched Smith predictor on the basis of the internal model control (IMC) method. Design formulas are given and design procedure is significantly simplified. One important merit of the proposed method is that the response of the closed loop system can be easily adjusted. The relation between the controller parameter and the system response is monotonous. In addition, necessary and sufficient condition for the robust stability of mismatched Smith predictor is also given. It is shown that the proposed method can provide good performance for perfectly matched system and a better response for mismatched system. Several numerical examples are given to illustrate the proposed method.     

Improving performance using cascade control and a Smith predictor

Many investigations have been done on tuning proportional-integral-derivative (PID) controllers in single-input single-output (SISO) systems. However, only a few investigations have been carried out on tuning PID controllers in cascade control systems. In this paper, a new approach, namely the use of a Smith predictor in the outer loop of a cascade control system, is investigated. The method can be used in temperature control problems where the secondary part of the process (the inner loop) may have a negligible delay while the primary loop (the outer loop) has a time-delay. Two different approaches, including an autotuning method, to find the controller parameters are proposed. It is shown by some examples that the proposed structure as expected can provide better performance than conventional cascade control, a Smith predictor scheme or single feedback control system.     

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.     

多温区电加热炉温度控制算法的研究与应用

针对多温区电加热炉大时滞、时变性强、强耦合和对象模型难以确定等特点,提出一种基于继电辨识模型的PID自整定算法,该法将Smith预估算法、继电辨识和模糊控制相结合,用继电反馈法在线辨识出Smith预估所需要的对象模型,并整定出控制器PID的初始值,在此基础上,对系统进行Smith预估补偿的同时利用模糊控制在线修正PID参数.经实验证明将该算法运用于多温区电加热炉的温度控制中是合适的,可获得很好的控制精度和鲁棒性.     

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.     

Robust time-delay control of a reclaimer

In this paper, a robust time delay control for a reclaimer is investigated. Supplying the same amount of raw material throughout the reclaimation process, from the raw yard to a sinter plant, is important to keep the quality of the molten steel uniform. As the parameter values of the reclaimer are not available, the boom rotational dynamics. is modeled as a second order differential equation with unknown coefficients. The unknown parameters in the nominal model are estimated using recursive estimation method. Another important factor in the control problem of a reclaimer is the large time delay in output measurement. Assuming a multiplicative uncertainty, that accounts for both the unstructured uncertainty neglected in the modeling and the structured uncertainty in the parameter estimation, a robust Smith predictor is designed. A robust stability criterion for the multiplicative uncertainty is derived. Following the work of Goodwinet al. (1992), a quantifying procedure of the multiplicative uncertainty bound, through experiments, is described. Experimental and simulation results are provided.     

Application of Smith Predictor Based on Single Neural Network in Cold Rolling Shape Control

Flatness is one of the most important criterion factors to evaluate the quality of the steel strip. To improve the strip' s flatness quality, the most frequently used methodology is to employ the closed-loop automatic shape control system. However, in the shape control system, the shape-meter is always installed at the down way of the exit of the cold rolling mill and can not sense the changes of the strip flatness in the rolling gap directly. This kind of installation results in the delay of the feedback in the control system. Therefore, the stability and response performance of the system are strongly affected by the delay. At present, there is still no mature way to design controllers for systems with time delay. Although the conventional PID controller used in most practical applications has the capability to comte the delay, the effect of the compensation is limited, especially for the systems with long time delay. Smith predictor, as a compensator for solving this problem, is now widely used in industry systems. However, the request of highly precise model of the system and the poor adaptive performance to the changes of related parameters limit the application of the Smith predictor in practice. In order to overcome the drawbacks of the Smith predictor, a new Smith predictor based on single neural network PID (SNN-PID) is proposed. Because the single neural network is employed into the Smith predictor to improve the controller's self-adaptability, the adaptive capability to the varying parameters of the system is improved. Meanwhile, for the purpose of solving the problems such as time-consuming and complicated calculation of the neural networks in real time, the learning coefficient of neural network is divided into several stages as usually done in expert control system. Therefore, the control system can obtain fast response due to the improved calculation speed of the neural networks. In order to validate the performance of the proposed controller, the experiment is conducted on the shape control system in a 300 mm four-high reversing cold rolling mill. The experimental results show that the SNN-PID with Smith predictor controller can effectively compeusate the delay effects and achieve better control performance than the conventional PIO controller.     

A new Smith predictor and controller for control of processes with long dead time

Good control of processes with long dead time is often achieved using a Smith predictor configuration. Typically a PI or PID controller is used; however, it is shown in this paper that for some situations improved set point and disturbance responses can be obtained if a PI-PD controller is used. Several methods are possible for selecting the parameters of the PI-PD controller but when the plant transfer function has no zeros, the use of the standard forms provides a simple algebraic approach, and also reveals why difficulties may be encountered if a PID controller is used. Some examples are given to show the value of the approach presented.     

Deep learning-based smith predictor design for a remote grasping control system

In this study, a robotic hand control system was designed based on data gloves, aiming to provide more intuitive control and improved operational performance for a remote robotic hand. Compensation measures were proposed for the time lag effect on the remote-control system to address the input and feedback time delays of the remote robot system. A Smith predictor structure was modified by replacing the linear estimator with a recurrent neural network. A convolutional neural network was applied to the long short-term memory (LSTM) model, as it had a better convergence time and learning performance than the multi-layer perceptron model during training. The experimental results demonstrate that the control effect of this scheme is approximately 0.5 s faster than the normal Smith predictive control, proving its effectiveness.

     

几种特殊动态特性对象的预测PI控制

提出了基于一阶加纯滞后、二阶非振荡及振荡加纯滞后、反向特性加纯滞后和积分特性加纯滞后对象的预测 PI控制器的结构形式。这种预测 PI控制器既具有 PI控制器的功能 ,又具有预测功能 ,特别适合大纯滞后系统的控制 ,而且结构简单 ,可调参数少 ,参数的调节方便、直观。通过几种实际对象的模型仿真表明 :在干扰、噪音存在和模型失配的情况下 ,预测 PI控制器仍然具有良好的控制性能 ,是一种值得在实际工程中推广应用的新型控制器     

Optimal solution,quantitative performance estimation,and robust tuning of the simplifying controller

Recently, a simplifying controller has been proposed based on the principal of simplification of the control system transfer functions, which offers improved control for processes with a large time delay. It is the purpose of this complementary paper to give a comprehensive analysis on the scheme. First, the relationship among the simplifying controller, the Smith predictor, and the internal model control are discussed. Second, an analytical design procedure is developed based on internal model control (IMC) and optimal solution is derived. Third, the problem of estimating the time domain performance of the closed loop system, quantitatively, is discussed. Fourth, a simple robust tuning procedure is presented. Numerical examples are provided to illustrate the proposed method.     

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。