Operating regime based dynamic engine modelling

In this paper the nonlinear model identification of combustion engines using operating regime model structures is discussed. The split of the engine process into several local operating regimes, characterised by the dominant influence of load and speed, allows one to overcome the highly nonlinear dynamic complexity of the engine. Additionally, local limits in terms of engine protection and combustion stability can be considered much easier. Such a model, with physical a priori information embedded in the model structure, provides excellent generalisation capability and a real-time application of the model is easily possible.     

Active fault detection and control: Unified formulation and optimal design

A new unified formulation of the active fault detection and control problem for discrete-time stochastic systems and its optimal solution are proposed. The problem formulation stems from the optimal stochastic control problem and includes important special cases: an active detector and controller, an active detector and input signal generator, and an active detector with a given input signal generator. The optimal solution is derived using the so-called closed loop information processing strategy. This strategy respects the influence of the current decision and/or input on the future behavior of the observed system, allows penalizing future wrong decisions, and improves the quality of fault detection. The proposed formulation and obtained solution also provide better understanding of the active fault detection and its relation to the optimal stochastic control. The results are illustrated in numerical examples.     

序贯实验设计方法在变换反应动力学方程模型参数估值研究中的应用

根据序贯实验设计原理,提出用于 B_(110-2)催化剂的动力学模型参数估值程序,并提出B_(110-2)催化剂的中温变换反应本征动力学方程。     

Optimal input design for parameter estimation in a single and double tank system through direct control of parametric output sensitivities

In this paper the traditional and well-known problem of optimal input design for parameter estimation is considered. In particular, the focus is on input design for the estimation of the flow exponent present in Bernoulli's law. The theory will be applied to a water tank system with a controlled inflow and free outflow. The problem is formulated as follows: Given the model structure (f, g), which is assumed to be affine in the input, and the specific parameter of interest (θ), find a feedback law that maximizes the sensitivity of the model output to the parameter under different flow conditions in the water tank. The input design problem is solved analytically. The solution to this problem is used to estimate the parameter of interest with a minimal variance. Real-world experimental results are presented and compared with theoretical solutions.     

Robust optimal experiment design for system identification

This paper develops the idea of min-max robust experiment design for dynamic system identification. The idea of min-max experiment design has been explored in the statistics literature. However, the technique is virtually unknown by the engineering community and, accordingly, there has been little prior work on examining its properties when applied to dynamic system identification. This paper initiates an exploration of these ideas. The paper considers linear systems with energy (or power) bounded inputs. We assume that the parameters lie in a given compact set and optimise the worst case over this set. We also provide a detailed analysis of the solution for an illustrative one parameter example and propose a convex optimisation algorithm that can be applied more generally to a discretised approximation to the design problem. We also examine the role played by different design criteria and present a simulation example illustrating the merits of the proposed approach.     

Optimal design of the double sampling X¯ chart with estimated parameters based on median run length

The double sampling (DS) chart when the process parameters are unknown and have to be estimated from a reference Phase-I dataset is studied. An expression for the run length distribution of the DS chart is derived, by conditioning and taking parameter estimation into account. Since the shape and the skewness of the run length distribution change with the magnitude of the mean shift, the number of Phase-I samples and sample sizes, it is shown that the traditional chart’s performance measure, i.e. the average run length, is confusing and not a good representation of a typical chart’s performance. To this end, because the run length distribution is highly right-skewed, especially when the shift is small, it is argued that the median run length (MRL) provides a more intuitive and credible interpretation. From this point of view, a new optimal design procedure for the DS chart with known and estimated parameters is developed to compute the chart’s optimal parameters for minimizing the out-of-control MRL, given that the values of the in-control MRL and average sample size are fixed. The optimal chart which provides the quickest out-of-control detection speed for a specified shift of interest is designed according to the number of Phase-I samples commonly used in practice. Tables are provided for the optimal chart parameters along with some empirical guidelines for practitioners to construct the optimal DS charts with estimated parameters. The optimal charts with estimated parameters are illustrated with a real application from a manufacturing company.     

Robustness of the estimators of transition rates for size-classified matrix models

Matrix models are often used to model the dynamics of age-structured or size-structured populations. The Usher model is an important particular case that relies on the following hypothesis: between time steps t and t+1, individuals either remain in the same class, move up to the following class, or die. There are then two ways of handling data that do not meet this condition: either remove them prior to data analysis or rectify them. These two ways correspond to two estimators of transition parameters. The former, which corresponds to the classical estimator, is obtained from the latter by a data trimming. The two estimators of transition parameters are compared on the basis of their robustness in order to obtain a criterion of choice between the two estimators. The influence curve of both estimators is first computed, then their gross sensitivity and their asymptotic variance. The untrimmed estimator is more robust than the classical one. Its asymptotic variance can be lower or greater than that of the classical estimator depending on the boundaries used for data trimming. The results are applied to a tropical rain forest in French Guiana, with a discussion on the role of the class width.     

对Ⅱ型建模误差有强鲁棒性的混合MRAC系统设计

本文推导了一种混合模型参考自适应控制方案。对建模误差，尤其是对Ⅱ型建模误差的影响，有很强的鲁律性。仿真结果表明控制效果与理论分析是一致的。     

μXL在高校实验中的应用

在简单介绍μＸＬ系统基本组成的基础上,从教学实验的角度,分别叙述了μＸＬ控制设备在过程建模、控制器参数整定和组织专门控制系统等方面的应用。     

A computational method for solving optimal control and parameter estimation of linear systems using Haar wavelets

In this article, a computational method based on Haar wavelet in time-domain for solving the problem of optimal control of the linear time invariant systems for any finite time interval is proposed. Haar wavelet integral operational matrix and the properties of Kronecker product are utilized to find the approximated optimal trajectory and optimal control law of the linear systems with respect to a quadratic cost function by solving only the linear algebraic equations. It is shown that parameter estimation of linear system can be done easily using the idea proposed. On the basis of Haar function properties, the results of the article, which include the time information, are illustrated in two examples.     

Stable polyhedra in parameter space

A typical uncertainty structure of a characteristic polynomial is P(s)=A(s)Q(s)+B(s) with A(s) and B(s) fixed and Q(s) uncertain. In robust controller design Q(s) may be a controller numerator or denominator polynomial; an example is the PID controller with Q(s)=K_I+K_Ps+K_Ds². In robustness analysis Q(s) may describe a plant uncertainty. For fixed imaginary part of Q(jω), it is shown that Hurwitz stability boundaries in the parameter space of the even part of Q(jω) are hyperplanes and the stability regions are convex polyhedra. A dual result holds for fixed real part of Q(jω). Also σ-stability with the real parts of all roots of P(s) smaller than σ is treated.Under the above conditions, the roots of P(s) can cross the imaginary axis only at a finite number of discrete “singular” frequencies. Each singular frequency generates a hyperplane as stability boundary. An application is robust controller design by simultaneous stabilization of several representatives of A(s) and B(s) by a PID controller. Geometrically, the intersection of convex polygons must be calculated and represented tomographically for a grid on K_P.     

A novel model-based approach to optimization and control design of batch processes

Traditionally, many industrial batch processes have been operated according to rigid recipies, in spite of the fact that production would yield more profit or a better product if they were efficiently adapted to changes in quality and cost of the used and/or produced products, process and scheduling conditions, and so on. In this paper a approach, called the flexible recipe approach, is given, which transforms the common rather static recipes into recipes that can be easily improved and used for systematic and efficient production adaptation at the start of a batch and during the processing. To be able to use this approach in an industrial environment a practical implementation is made in the software package FRIS. A fermentation process chosen as an example shows the methods and gives an indication of the expected profit.     

一种次最优鲁棒调节器的设计方法

本文基于最优控制和极点配置理论,提出一种灵敏度低、动特性好的次最优鲁棒调节器设计法。它具有计算方便、结构简单的特点。     

Optimal refractive index design for an optical fibre-based evanescent field sensor

Optical fibre-based evanescent field sensors are proving to be viable and useful in the detection of chemicals, toxins, gases and other species. Such fibre sensors rely on weak interactions between the surrounding environment and the external “evanescent” field associated with bound modes of electromagnetic radiation propagating through an optical fibre. Of fundamental importance in the design of such sensors is the fraction of the total guided field power that propagates as the evanescent field. By increasing this relative evanescent field power, sensor gain can be improved. As the evanescent field is determined by the refractive index profile (RIP) of the sensor and the surrounding environment, design of the sensor RIP is critical. This paper presents a rigorous approach to this RIP design problem, formulated in terms of an optimization problem with the normalized evanescent field power as the payoff, RIP as the input, and a simple electric field model as the constraint. An RIP design procedure utilizing dynamic programming is then presented, along with an example that illustrates the improvement obtainable over existing designs.     

Optimization of a thin film deposition process using a dynamic model extracted from molecular simulations

This study presents and demonstrates an algorithm for computing a dynamic model for a thin film deposition process. The proposed algorithm is used on high dimensional Kinetic Monte Carlo (KMC) simulations and consists of applying principal component analysis (PCA) for reducing the state dimension, a self organizing map (SOM) for grouping similar surface configurations and simple cell mapping (SCM) for identifying the transitions between different surface configuration groups. The error associated with this model reduction approach is characterized by running more than 1000 test simulations with highly dynamic and random input profiles. The global error, which is the normalized Euclidean distance between the simulated and predicted states, is found to be less than 1% on average relative to the test simulation results. This indicates that our reduced order dynamic model, which was developed using a rather small simulation set, was able to accurately predict the evolution of the film microstructure for much larger simulation sets and a wide range of process conditions. Minimization of the deposition time to reach a desired film structure has also been achieved using this model. Hence, our study showed that the proposed algorithm is useful for extracting dynamic models from high dimensional and noisy molecular simulation data.     

航空快速电磁阀的设计和仿真研究

根据某小型发动机控制系统改型需要设计了小电压、小流量快速电磁阀取代原有的液压调节阀,以动态电磁方程为基础对其核心的电磁部分进行了参数设计计算;并以流量连续方程和力平衡方程为基础建立了整个电磁阀的微分形式的数学模型,由MATLAB中的simulink软件直接进行仿真研究和参数分析。研究结果表明:所设计的快速电磁阀,响应速度快,工作稳定、控制精度高,完全满足设计要求,证实了方法的有效性和准确性;直接由微分方程仿真的方法既避免了惯用的小增量线性化对非线性系统的影响,也能实时修正非线性元件和系统的非线性参数,对工程动态设计、反设计、优化提供了依据。