Distributed Control Strategy with Smith's Predictor in a Pilot-Scale Diabatic Distillation Unit

Intrinsic characteristics of distillation such as dead time and high nonlinearities do not allow the complete elimination of transient times when any external disturbance or set-point change occurs. Thus, aiming at the use of easy-tuning systems, a distributed-action control in trays of a diabatic distillation unit with Smith's predictor was implemented in the Simulink environment to further reduce transient times and out-of-specification product. The distributed-action strategy with Smith's predictor led to a reduction of 33.3 min (33 %) in the transient time of the top temperature control loop and 66 % in out-of-specification product, when compared with the conventional strategy, and thus is shown to be an efficient approach to increasing the productivity of distillation plants.     

On oscillation reduction in feedback control for processes with an uncertain dead time and internal–external disturbances

This paper aims to find a practical solution to reduce oscillation on the Smith Predictor (SP) based design with the dead time (DT) uncertainty, making it less sensitive to DT change and more effective in disturbance rejection. First, a conditional feedback mechanism is introduced in SP to reduce the amount of oscillation caused by the model inaccuracies in the DT parameter. Then, to address the oscillation caused by the phase lag in traditional PI controller and uncertain dynamics, this conditional SP is combined with active disturbance rejection control (ADRC), assisted by the knowledge of process dynamics. A practical tuning method is provided for the practicing engineers. The proposed approach is validated in extensive simulation studies with different types of plants and in frequency domain analysis. The simulation results show significant improvements in performance robustness and transient response.     

模糊Smith预估控制在圆锥破碎机控制系统中的应用

针对圆锥破碎机控制系统是一个带有不确定时滞及非线性特性电振给矿机的大纯滞后系统，采用Smith预估控制和模糊控制相结合的串级控制，对系统的主、副回路进行设计，使系统在高性能下运行。     

Lifting transform via Savitsky-Golay filter predictor and application of denoising

The Savitsky-Golay filter is a smoothing filter based on polynomial regression. It employs the regression fitting capacity to improve the smoothing results. But Savitsky-Golay filter uses a fix sized window. It has the same shortage of Window Fourier Transform. Wavelet mutiresolution analysis may deal with this problem. In this paper, taking advantage of Savitsky-Golay filter＇s fitting ability and the wavelet transform＇s multiscale analysis ability, we developed a new lifting transform via Savitsky-Golay smoothing filter as the lifting predictor, and then processed the signals comparing with the ordinary Savitsky-Golay smoothing method. We useed the new lifting in noisy heavy sine denoising. The new transform obviously has better denoise ability than ordinary Savitsky-Golay smoothing method. At the same time singular points are perfectly retained in the denoised signal. Singularity analysis, multiscale interpolation, estimation, chemical data smoothing and other potential signal processing utility of this new lifting transform are in prospect.     

基于神经网络的预测控制

基于神经网络的预测控制器由神经单元自适应PID控制器和基于神经网络的Smith预估器组成.预估器对输出进行多步预测,使控制器超前动作以消除时滞对系统的影响.自适应PID控制器通过有监督的Hebb学习算法实现其权值调节,通过权系数的在线调整实现自适应控制.并以仿真试验给予了验证.     

Smith 预估模糊自适应PID 控制在时滞系统中的应用

为确保系统的实时性和稳定性,设计一种新的Smith预估模糊自适应PID控制器。以气液增力缸的自动控制为具体研究对象,将模糊自适应控制器与传统的PID控制器结合,通过Smith预估器将控制过程中出现的纯滞后环节移至闭环系统之外,并在Matlab中进行仿真验证。验证结果表明：该设计能消除纯滞后现象,提高响应实时性和稳定性。     

Temperature Control Based on Fuzzy Logic Two-degree-of-freedom Smith Internal Model

According to the characteristics of the large time delay, nonlinearity and the great inertia of temperature control system in biomass pyrolysis reactor, a two-degree-of-freedom Smith internal model controller based on fuzzy control is proposed. Firstly, the mathematical model of the temperature control system is established by using the step response method, and then the two-degree-of-freedom Smith internal model controller is designed, and the good tracking per-formance and disturbance suppression performance can be obtained by designing the set value tracking controller and interference rejection capability. Secondly, the fuzzy control algorithm is used to realize the on-line tuning of the control parameters of the two-degree-of-freedom Smith internal model algorithm. The simulation results show that, compared with the traditional internal model control, fuzzy internal model PID control and two-degree-of-freedom Smith internal model control, the algorithm proposed in this paper improves the influence of lag time on the control system, realizes the separation control of set point tracking and anti-jamming performance and the self-tuning of control parameters, and improves the control performance of the system.     

矢量网络分析仪的时频域阻抗测量技术

由于传输线阻抗不连续性导致的串扰问题会严重影响信号传输的质量,从而导致信号完整性问题。从矢量网络分析仪阻抗测试原理出发,通过对比网络仪开路校准及端口补偿后的Smith圆图测量结果、阻抗和相位格式测量结果,说明网络仪频域3种测量格式所表述的阻抗信息;利用矢量网络分析仪时域变换功能从时域上对传输线进行评估,可以获得传输线阻抗不连续点和各位置阻抗信息。最后通过对一段3.5 mm传输线的测试,说明如何利用矢量网络分析仪的频域和时域同时对传输线特性尤其是阻抗特性进行评估,为传输线测试提供了一种新的方法。     

基于改进型Smith预估器的同步施工网络控制系统

根据同步施工网络控制系统的控制原理,分析了时变、随机和不确定的网络时延对同步误差控制所产生的影响。针对传统Smith预估器用于多被控对象同步控制时存在的缺陷与不足进行了分析,提出了一种改进型Smith预估器,实现了对网络时延、被控对象纯滞后因子以及同步误差控制器的多重Smith预估补偿,将其从内部反馈回路中彻底消除,预估模型无需预估与在线测量其大小与变化规律。通过基于控制器局域网络(controller area network,简称CAN)的盾构管片拼装机同步网络控制系统,对常规比例积分微分(proportion integral derivative,简称PID)同步网络控制和基于改进型Smith预估器的PID同步网络控制性能进行了仿真对比分析,并通过实验进行了验证。结果表明,常规PID网络控制同步误差为-3～3mm,基于改进型Smith预估器的PID网络控制同步误差为-1.5～1.5mm,后者可显著提高同步施工网络控制系统的同步控制性能与精度。