随机多智能体系统的多率协同控制

本文针对一类带有非线性动力学的随机多智能体系统研究了基于多率采样机制的一致性控制问题。首先,引入多率采样机制异步地对智能体的状态进行采样,并且使用缓存器来同步智能体不同分量的状态信息。然后,提出了一种基于边的事件触发传输机制将每个智能体的状态信息定向传输给邻居智能体,从而减少了通信资源的使用和控制器的更新频率。接着,本文根据所设计的事件触发传输机制设计了相应的控制协议使得随机多智能体系统可以实现均方一致性。因为每条边上的事件都是独立发生的,所以智能体的邻居之间不需要保证信息的时钟同步。最后,给出了数值仿真例子。通过将同步采样机制、异步采样机制和多率采样机制进行比较,说明了所提出的边事件触发传输机制在多率采样下可以获得更好的系统性能。     

Multi-rate dissipativity based control of process networks

An approach to multi-rate distributed control design for process networks is presented, where the local measurements, local control and controller communication are allowed to operate at different sampling rates. Dissipative systems theory is used to facilitate stability and performance analysis of the process network, based upon dynamic supply rates which have been lifted into a global sampling rate. Quadratic difference forms are used as supply rates and storage functions, leading to less conservative stability and performance conditions as compared to classical types of supply rates. These theoretical results are illustrated by a case study of a heat exchanger network.     

Cycle to cycle adaptive control of simulated moving bed chromatographic separation processes

The simulated moving bed (SMB) technology is increasingly applied in various fields, ranging from the food to the pharmaceutical sectors, for the chromatographic separation of fine (bio)chemicals. In this study, an adaptive controller acting on the fluid flow rates and commutation period is used to regulate the spatial location of the adsorption and desorption waves, and in turn the purity and productivity of the raffinate and extract effluents. This controller is based on a simple discrete-time model of the concentration fronts movement, derived from wave theory. A simple parameter adaptation scheme makes this controller robust to parameter uncertainties and drifts, and allows process start-up with minimum a priori knowledge of the separation parameters. In this study, the performance of the controller is demonstrated for two different applications: the separation of fructo-oligosaccharides (linear isotherms) and cyclopentanone–cycloheptanone (competitive Langmuir isotherms). Different plant/sensor configurations are also examined, indicating the potential of the control strategy even with reduced measurement information.     

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.     

一种优选移动平均预测模型的Min-Min算法

为使移动平均法预测技术的应用从专业化向大众化、人工化向智能化转变,在对一次移动平均模型进行改进之后,以预测的局部残差平方和最小为原则,设计出一种优选移动平均预测模型的Min-Min算法:首先,分别选出一次移动平均模型和二次移动平均模型各自的最优移动项数;然后,在最优的一次模型与最优的二次模型之间作出最优次数的选择;最后,基于优选出的移动平均模型对未来一期开展点预测和区间预测.同既有算法相比,本算法对移动平均法预测技术的进步性主要体现在:a)以先选定移动项数、后选定移动次数的程序算法取代先选定移动次数、后选定移动项数的专家做法,从而将移动平均法的实施从半自动化的人工预测提升至全自动化的智能预测;b)对现行的一次移动平均模型进行改进,从而大幅提高一次移动平均法的预测能力;c)在移动平均模型现行只有点预测的基础上进一步提出区间预测,从而起到完善和丰富预测报告的作用.     

Interpolating optimizing process control

A new model-based optimizing controller for a set of nonlinear systems is proposed. The nonlinear model set is based on a convex combination of two bounding linear models. An optimal control sequence is computed for each of the two bounding models. The proposed control algorithm is based on a convex combination of the two control sequences. A novel feature in these two optimizations is an added constraint related to the feasibility of the ‘other’ bounding model. The control algorithm can for example be used in model predictive control. We provide robust feasibility guarantees and an upper bound on the optimal criterion if the bounding models are linear FIR models. Further, simulation examples demonstrate significant feasibility improvements in the case where the bounding models are general linear state-space models. The proposed method guarantees robust feasibility for a 1-step ahead prediction in the general case. This can be of interest in MPC applications.     

Multi-rate adaptive control with applications to lateral dynamics of aircraft

This paper deals with the development of multi-rate adaptive control algorithms with applications in the control of aircraft lateral dynamics. Several control channels work at different sampling rates so as to improve transient behaviour and disturbance rejection characteristics. Simulation results which corroborate the efficiency of the proposed algorithms are also given.     

Three-dimensional reconstruction of moving arterial beds from digital subtraction angiography

A system for three-dimensional reconstruction of dynamic (moving) vascular bed structures has been developed and is described. Input images are obtained from two-view (bi-plane or ECG correlated) X-ray angiograms. A target structure consisting of vessel branch points (nodes) and lines between the branch points is entered on the first of a sequence of images in one view. The movement of the nodes is indicated on subsequent images and on the images of the second view. The target is linearly warped according to the motion of the node points. Automatic edge detection (with subsequent operator correction) is used to detect centerlines and edges of vessels. Three-dimensional reconstruction is accomplished using a distance minimizing point matching technique. Finally, angle-corrected densitometric methods are used to refine the vessel cross section. Standard shaded surface display techniques are then used to display the moving arterial bed. Flow measurements are obtained by tracking the leading edge of the bolus down the three-dimensional arterial tree.     

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.     

基于飞行器网络控制系统的多速率控制器设计

为了减少网络环境中的时延和数据包丢失对飞行器网络控制器系统的影响,设计了一种具有多速率的保性能控制器设计方法;多速率是指在具有多通道数据传输的系统中,各通道所需控制输入的频率不完全相同;在存在时延和丢包的情况下,利用增广技术对飞行器控制系统在整个循环周期内建立离散模型,此时为了使多速率控制方法更加有效,先基于此模型在控制器输入端构造一个预测器,根据预测器的输出为整个系统设计一个具有多控制速率的动态输出反馈控制器;然后给出并证明保性能控制器的存在条件和求解方法;最后通过某飞行器网络控制系统的数值算例验证了所提方法的有效性。     

一种用于BP网络优化的并行模拟退火遗传算法

针对模拟退火算法和遗传算法存在的不足,提出了并行模拟退火遗传算法,并用于3层BP神经网络优化。在适应度函数中引入模拟退火机制,采用排序、最优保存策略选择算子、启发式交叉和多点非均匀变异改进遗传算子,利用模拟退火算法产生新解增加搜索方向,并结合并行进化思想对经典遗传算法进行改进。通过对英文字母识别的仿真实验,表明该方法全局搜索能力、局部搜索能力和收敛速度都优于经典遗传算法。     

模拟移动床过程的结构优化策略研究

模拟移动床(Simulated Moving Bed,SMB)技术作为主要的吸附分离技术,近年来在石油化工、精细化工、生物医药和食品工业中得到广泛的应用。如何基于模拟移动床的机理数学模型进行优化,以提高模拟移动床分离过程的经济效益,是模拟移动床研究领域的热点问题之一。模拟移动床过程具有复杂的动态特性,例如,由于出入口切换带来的混杂、非线性以及延迟特性。另一方面,由于对过程干扰和系统不确定性的高灵敏性,使得模拟移动床过程在操作点处的鲁棒操作仍然是一个研究的重点。以模拟移动床过程为研究背景,在阐述其工作原理的基础上,通过对模拟移动床过程的不同分区情况以及柱配置情况进行研究,得到了模拟移动床模型的结构优化过程描述,然后通过在不同目标函数情况下进行优化结果:的比较,说明模拟移动床过程结构优化的可行性,对进一步的控制方案设计具有一定的指导意义。以模拟移动床过程为研究背景,在阐述其工作原理的基础上,通过对模拟移动床过程的不同分区情况以及柱配置情况进行研究,得到了模拟移动床模型的结构优化过程描述,然后通过在不同目标函数情况下进行优化结果:的比较,说明模拟移动床过程结构优化的可行性,对进一步的控制方案设计具有一定的指导意义。     

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。     

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。     

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.     

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。     

快速公交线路组合频率优化的禁忌模拟退火算法仿真

针对快速公交(BRT)线路组合的频率优化目标,建立了兼顾公交运营效益和乘客服务要求的BRT运营作业安排数学模型.根据问题的特点,将禁忌算法与模拟退火算法相结合,对BRT线路组合的频率进行优化.多次仿真运算结果及分析表明,该算法具有比禁忌算法、模拟退火算法都更好的效率,是解决该类问题的一个有效途径.     

一种工业过程稳态优化控制算法

针对带有输出关联约束的工业过程,提出一种确定其稳态优化控制的算法.首先通过对数变换将原问题转化为一个等价而且可在对数空间求解的优化控制问题;然后为避免事先选择一个合适罚系数的困难,在算法中引入了目标函数的线性化形式.该优化算法不仅能收敛到正确的系统最优解,而且可用现有的二次规划算法计算.应用简单的滤波技术,改善了算法在有量测噪声情况下的性能.仿真结果表明,所提出的优化算法是有效的.     

Multi-rate model predictive control of particle size distribution in a semibatch emulsion copolymerization reactor

A multi-rate model predictive controller algorithm is presented for the in-batch closed-loop control of the full particle size distribution (PSD) in a semibatch emulsion copolymerization system. The lack of frequent measurements of the PSD and the measurement delay of these measurements are addressed through the use of frequent density measurements from which the current conditions of the system are estimated. The high dimensionality of the discretized full PSD is reduced by the use of model order reduction based on principal component analysis. This method effectively reduces the size of the problem while preserving the main characteristics of the population balance system. Disturbances that perturb the surfactant and monomer amounts inside the semibatch vinyl acetate–butyl acrylate reactor are considered to demonstrate the performance of the proposed control algorithm.