Decentralised control of chromatographic simulated moving bed processes based on wave front reconstruction

The behaviour of chromatographic simulated moving bed processes is described by the movement of concentration profiles through a circle of separation columns. A closed-loop control manipulates the profiles in order to meet demands concerning specified product purity and disturbance attenuation. If steep wave fronts of the concentration profiles occur, the controlled variables undergo fast changes in case of a transient of the process. In this case, a reconstruction of the wave fronts is necessary for a successful control.A simple and effective decentralised controller structure is proposed based on cascaded discrete-time PI controllers. On-line product purity measurements and the reconstructed wave fronts are used for control purposes. Two kinds of process models are used: a rigorous model for dynamic simulations, and strongly simplified plant models for the design of the wave front reconstruction and the controller. The latter models are identified based on experimental step tests with the reference plant and numerical simulations. The performance of the control system is evaluated by numerical simulations.     

Model-based control of a simulated moving bed chromatographic process for the separation of fructose and glucose

Chromatographic separations are an expanding technology for the separation of high value products, particularly in the area of pharmaceutics, food, and fine chemicals. The simulated moving bed (SMB) process as a continuous chromatographic separation process is an interesting alternative to conventional batch chromatography, and gained more and more impact recently. The SMB process is realized by connecting several single chromatographic columns in series. A countercurrent movement of the bed is approximated by a cyclic switching of the inlet and outlet ports in the direction of the fluid stream. Because of its complex dynamics, the optimal operation and automatic control of SMB processes is a challenging task. This paper presents the design of a model-based optimization and control scheme for SMB chromatographic separation processes and its application to the separation of fructose and glucose. We propose a two-layer control architecture where the optimal operating trajectory is calculated off-line by dynamic optimization based on a rigorous process model. The parameters of the model are adapted based on online measurements. The low-level control task is to keep the process on the optimal trajectory despite disturbances and plant/model mismatch. Here identification models based on simulation data of the rigorous process model along the optimal trajectory are combined with a suitable local controller. The efficiency of the trajectory control algorithm is shown in a simulation study for the separation of fructose and glucose on an 8-column SMB plant.     

模拟移动床色谱计算机辅助系统的设计

介绍了采用Visual C 开发的模拟移动床色谱计算机辅助系统。该系统可根据实验参数，快速准确地对模拟移动床色谱的分离过程进行模拟，为操作条件选择提供可靠的依据。该系统的核心部分为模拟移动床色谱动态模型，该模型采用正交配置有限元法求解。该软件用户界面友好，操作简单方便，分层设计的思想利于软件的维护与升级。     

模拟移动床吸附分离技术及其应用

详细地介绍了模拟移动床色谱吸附分离技术的发展历史及其工作原理,由于模拟移动床色谱吸附分离过程是一个具有非线性、非理想、多变量耦合、色谱连续动态分离过程与物料进出口位置周期性切换离散事件相互混合等特征的复杂混合系统,因此重点讨论了描述模拟移动床色谱分离行为的理论模型。在此基础上,综述了该技术国内外的研究进展以及在精细化工、石油化工、制药等方面的主要应用,对该技术在我国的研究现状以及存在的问题也作了介绍。     

模拟移动床色谱非线性的动态过程

研究模拟移动床色谱分离的动态过程。分析模拟移动床色谱柱内物料浓度的分布情况,表明色谱分离是一个动态平衡的过程。组份可以在很小的分离度之下提纯。     

Automatic control of the simulated moving bed process for C8 aromatics separation using asymptotically exact input/output-linearization

An approach to automatic control of the simulated moving bed process (SMB) applied to the separation of C₈ aromatics is presented. The principle of asymptotically exact input/output-linearization is used. The controller is based on a nonlinear state estimator using the true moving bed model (TMB). The estimator receives measurement data from four spectroscopic measurement cells. The problem of moving measurement positions with respect to the TMB model is addressed. An exactly linearizing feedback of the estimated states is designed using the nonlinear TMB model equations. The performance of the controller is shown in simulations using a detailed SMB model as a representative of the real process.     

非线性模拟移动床色谱的浮点编码遗传算法优化策略

开发了一种基于浮点编码遗传算法的模拟移动床色谱自动优化系统。该优化方法中将归一化的生产强度取最大值作为目标函数,同时将纯度的n次方作为罚函数。采用模拟移动床色谱的稳态模型计算浮点编码遗传算法的适度值。采用该优化算法对手性化合物binapththol的模拟移动床分离操作条件进行了优化,结果表明生产强度提高了40％以上。     

基于Vericol工艺的模拟移动床的动态仿真

针对传统模拟移动床(SMB)的工艺是各个进出料口切换周期固定且同步的问题,采用了模拟移动床零附加成本的Varicol工艺设计改造。因为SMB运行方式中各个进出料口在每个固定周期末是同步切换,而Varicol运行方式通过将每个切换周期细化,在细化后的小周期内实现进出料口的异步切换,使得模拟移动床各功能区的柱数配置可随时间变化而进行周期性的变换。本文设计了多种Vericol模式,并对不同模式下的模型进行仿真获得了其对应分离指标。仿真结果表明,Varicol工艺比传统SMB工艺具有更高自由度和更好的表现性。     

A novel robust adaptive control algorithm with finite-time online parameter estimation of a humanoid robot arm

A novel robust adaptive control algorithm is proposed and implemented in real-time on two degrees-of-freedom (DOF) of the humanoid Bristol-Elumotion-Robotic-Torso II (BERT II) arm in joint-space. In addition to having a significant robustness property for the tracking, the algorithm also features a sliding-mode term based adaptive law that captures directly the parameter estimation error. An auxiliary filtered regression vector and filtered computed torque is introduced. This allows the definition of another auxiliary matrix, a filtered regression matrix, which facilitates the introduction of a sliding mode term into the adaptation law. Parameter error convergence to zero can be guaranteed within finite-time with a Persistent-Excitation (PE) condition or Sufficient Richness condition for the demand. The proposed scheme also exhibits robustness both in the tracking and parameter estimation errors to any bounded additive disturbance. This theoretical result is then exemplified for the BERT II robot arm in simulation and for experiments.     

基于隐式差分法的色谱分离过程操作模型研究

该文中以色谱分离过程的平衡-扩散的速率模型为基础,运用隐式差分法研究开发模拟移动床模型数值求解的软件平台,其整个过程都是采用稀疏矩阵进行运算从而使仿真时间大大减少,为以后的系统优化、分离性能的研究提供了良好的基础。仿真结果:表明:隐式差分法得到的数值结果:与实验结果:吻合较好,可以作为实际的色谱分离的操作试验的指导。     

一种新的模糊自适应模拟退火遗传算法

针对遗传算法收敛速度慢、容易"早熟"等缺点,结合模糊推理、模拟退火算法和自适应机制,提出一种改进的遗传算法--模糊自适应模拟退火遗传算法(FASAGA),并分析了该算法的性能和特点,实验研究表明,该算法比标准的遗传算法(SGA)具有更快的收敛速度和寻优效果.     

模拟移动床过程的混杂系统建模方法

模拟移动床过程中连续变量与离散变量并存,属于典型的混杂系统.对此,从混杂系统的角度出发,在简化模拟移动床过程平衡扩散模型的基础上,探索一种新的模型表示方法.通过应用一些近似处理方法,导出了完整的一类混合整数动态模型,并通过对一种混杂非线性的Benchmark模型的仿真实验验证了所建立的混合逻辑动态模型的有效性.     

基于Profibus-DP现场总线的多功能色谱分离装置控制系统设计

为了实现多功能色谱分离装置的精准化控制,加速模拟移动床色谱纯化分离速度,设计基于Profibus-DP现场总线的多功能色谱分离装置控制系统;以STM32F103微处理器作为底层控制设备,连接Profibus-DP协议芯片、VPC3与RS-485接口电路,转化从站地址电路与设定应用模块,利用模拟移动床控制回路,完成Profibus-DP现场总线的硬件电路设计;建立梯度SMB色谱,采用异步切换方式,控制变浓度进料的实际操作行为,分离处理模拟移动床多功能色谱,结合多功能色谱分离装置的控制原理,运用气相色谱法,分析色谱分离过程中的基质效应形式,实现多功能色谱分离装置控制系统软件设计;实验结果表明,基于Profibus-DP现场总线控制系统的模拟移动床色谱纯化分离速度较快,能够有效满足多功能色谱分离装置精准化控制的操作需求.     

Integrated direct/indirect adaptive robust contouring control of a biaxial gantry with accurate parameter estimations

This paper presents an integrated direct/indirect adaptive robust contouring controller (DIARC) for an industrial biaxial high-speed gantry that achieves not only excellent contouring performance but also accurate parameter estimations for secondary purposes such as machine health monitoring and prognosis. Contouring control problem is first formulated in a task coordinate frame. A physical model-based indirect-type parameter estimation algorithm is then developed to obtain accurate on-line estimates of unknown model parameters. A DIARC controller possessing dynamic-compensation-like fast adaptation is subsequently constructed to preserve the excellent transient and steady-state contouring performance of the direct adaptive robust controller (DARC) designs. The proposed DIARC along with previously developed DARC contouring controllers are implemented on a high-speed industrial biaxial gantry to test their achievable performance in practice. Comparative experimental results verify the improved contouring performance and the accurate physical parameter estimates of the proposed DIARC algorithm.     

Some comments on the use of normalization in robust adaptive control

This paper discusses the role of normalization with respect to robust parameter estimation for discrete-time adaptive control in the presence of unmodeled dynamics. It is pointed out that the normalizing signal may be brought into the adaptive law in two distinct ways; (i) via normalization of the regressor and the error signal in the standard parameter update law, and (ii) by replacement of the error signal with a function of the normalizing signal and the error. The convergence properties for both approaches are derived and shown to be similar.     

Stochastic control of processes having moving boundaries—An experimental study

A general state estimator requiring only discrete time measurements has been developed for nonlinear distributed parameter systems having moving boundaries. The state estimator has been combined with an optimal linear-quadratic feedback controller to provide a stochastic feedback control scheme for this class of problem. Both the state estimation and control algorithms were implemented in real time for a laboratory casting process and were found to perform well. The state estimation scheme would seem to hold the most interest for industrial applications.     

An augmented subcutaneous type 1 diabetic patient modelling and design of adaptive glucose control

In the present work, an augmented subcutaneous (SC) model of type 1 diabetic patients (T1DP) is proposed first by estimating the model parameters with the aid of nonlinear least square method using the physiological data. Next, a nonlinear adaptive controller is proposed to tackle two important issues of intra-patient variability (IPV) and uncertain meal disturbance (MD). The proposed patient model agrees quite well with the responses of one of the most popular existing nonlinear model used in the research of artificial pancreas. Further, the developed adaptive control is shown to be capable of providing desired glycemic control without feed-forward action for meal compensation or safety algorithms to avoid hypoglycemia. Due to the simple structure and capability of handling intra-patient variability of the adaptive controller, it can find immediate applicability in the development of the in-silico artificial pancreas.     

A universality advantage of stochastic excitation signals for adaptive control

Adaptive control schemes usually depend on estimation of system parameters, which in turn depends excitation of modes associated with these parameters. Such excitation is supplied by plant noise, the adaptive control signal itself, and any external excitation such as a reference signal. In this note, it is shown that there is a universality advantage for any externally applied signal to be stochastic rather than deterministic. The crucial property of a stochastic signal exploited in this note is its unpredictability by any causal system, such as an adaptive control scheme. When such unpredictable signals excite an adaptive control scheme, there is no need to deliberately constrain the adaptation to be ‘slow’ or ‘excitation maintaining’ to ensure adequate identification.