Parameter identification for Wiener-finite impulse response system with output data of missing completely at random mechanism and time delay

In this paper, the parameter estimation issue of Wiener system with random time delay and missing output data is studied. The linear part of Wiener system is described by Finite Impulse Response (FIR) model. The mathematical formula of the Expectation Maximum algorithm to identify Wiener-FIR system that contains the random time delay and the nonlinear output data in missing completely at random mechanism is derived, which is never considered before. To obtain the unmeasurable intermediate variable in Wiener-FIR system, the idea of auxiliary model is adopted. The time delay and system parameters can be estimated simultaneously by this method. Numerical example and the identification of water tank system example are carried out, the effectiveness of the algorithm is proved.     

Fully distributed tracking control for non‐identical multi‐agent systems with matching uncertainty

This article addresses the fully distributed consensus tracking control problem of linear multi‐agent systems with parameter uncertainties. First, a new class of distributed protocol, based on the relative states of neighbors, is proposed. Theoretical analysis indicates that the considered problem can be solved if the control gain constant of the protocol is larger than the norm bound of the leader's nonlinear inputs. Furthermore, a distributed adaptive control protocol is proposed for the case without available global information. The distributed consensus tracking control problem of uncertain linear multi‐agent systems is solved based only on local information under the proposed adaptive protocol. Finally, an application in low‐Earth‐orbit satellite formation flying is provided to illustrate the theoretical results. Copyright © 2014 John Wiley & Sons, Ltd.     

Benefits of variable structure techniques for parameter estimation in stochastic systems using least squares method and instrumental variables

In this paper, we study the benefits of the equivalent control method, implemented on parameter estimation algorithms like the least squares method and instrumental variables on continuous‐time stochastic systems. Here, we show how the equivalent‐control, adapted to the stochastic case, improves the performance of these estimation algorithms in continuous‐time systems under white noise perturbations. Some numerical examples show the effectiveness of these techniques. Copyright © 2014 John Wiley & Sons, Ltd.     

Parameter characterization of HTPEMFC using numerical simulation and genetic algorithms

This paper develops a novel approach to the parameterisation of high temperature exchange membrane fuel cells (HTPEMFC) with limited and non-invasive measurements. The proposed method allows an effective identification of electrochemical parameters for three-dimensional fuel cell models by combining computational simulation tools and genetic algorithms. To avoid each evaluation undertaken by the optimisation method involving a complete computational simulation of the 3D model, a strategy has been designed that, thanks to an iterative process, makes it possible to decouple the fluid dynamic resolution from the electrochemistry one.Two electrochemical models have been incorporated into these tools to describe the behaviour of the catalyst layer, Butler-Volmer and spherical aggregate. For each one, a case study has been carried out to validate the results by comparing them with empirical data in the first model and with data generated by numerical simulation in the second. Results show that, from a set of measured operating conditions, it is possible to identify a unique set of electrochemical parameters that fits the 3D model to the target polarisation curve. The extension of this framework can be used to systematically estimate any model parameter in order to reduce the uncertainty in 3D simulation predictions.     

Influence of operation number on arc erosion behavior of Ag/Ni electrical contact materials

Arc erosion behavior of Ag/Ni materials with different operation numbers was investigated by OM, 3DOP and SEM. The results indicated that the arc erosion of Ag/10Ni electrical contact material fabricated by sintering? extrusion technology was more and more serious with the operation numbers increasing from 1000 to 40000. With the same operation numbers, the arc erosion on anode was more serious than that on cathode. Besides, the pores preferred to emerge around the arc effect spot during the first 10000 operations. And the morphology of the molten silver on cathode and anode was different due to the action of gravity and arc erosion. Furthermore, the relationships among arc energy, arc time, welding force, electric resistivity, temperature and mass change on contacts were discussed, which indicated that the mass loss on cathode was mainly caused by the fracture of molten bridge.     

Identification and U-control of a state-space system with time-delay

This article presents a state-space model with time-delay to map the relationship between known input-output data for discrete systems. For the given input-output data, a model identification algorithm combining parameter estimation and state estimation is proposed in line with the causality constraints. Consequently, this article proposes a least squares parameter estimation algorithm, and analyzes its convergence for the studied systems to prove that the parameter estimation errors converge to zero under the persistent excitation conditions. In control system design, the U-model based control is introduced to provide a unilateral platform to improve the design efficiency and generality. A simulation portfolio from modeling to control is provided with computational experiments to validate the derived results.     

基于优化粒子数和分段权值的粒子群直线电机PID整定

以工程中直线电机伺服系统为研究对象,提出一种优化粒子数量加分段式惯性权重递减的粒子群PID控制器参数优化算法。优化粒子数量的方法可降低函数调用次数,通过对近两代的全局最优值进行比较,得到的误差值如果大于设定值,认为是在初始寻优阶段,保持粒子数量,否则在最终优化阶段,减少粒子数量,所减少的粒子特征是最接近最佳粒子的粒子,以保证在欧氏距离内实现粒子的分散性。最后再结合指数衰减曲线加线性递减曲线构成的分段式惯性权重递减策略提升算法的全局寻优和局部寻优能力。经数值验证分析,该优化算法在保证遍历性的同时,在一定程度上提高了算法的运行速度和寻优精度。实验仿真结果表明,该算法对PID控制器进行参数优化,直线电机系统响应速度快,超调量小,调节时间短。     

LD27-2油田稠油油藏蒸汽吞吐中后期注采参数优化研究

蒸汽吞吐是稠油油藏开发的最有效措施之一，但是对于海上油田的特殊条件，在进行蒸汽吞吐3~4轮后，即意味着进入蒸汽吞吐中后期。此时，如何调整注采参数，是海上稠油油藏高效开发的关键。针对LD27-2油田稠油油藏的开发特点，在地质建模和高度历史拟合的情况下，对LD27-2油田稠油油藏开发状况进行多轮次预测；基于生产历史拟合的油藏数值模型，开展了不同蒸汽干度、注汽强度、注汽强度递增等条件下A22H井和A23H井蒸汽吞吐至开采至10年的油藏数值模拟，明确不同注采参数的影响规律，优化了LD27-2油田稠油油藏蒸汽吞吐中后期注采参数。     

Modeling of sequence length distribution for olefin copolymerization with vanadium-based catalyst

Some thermodynamic and mechanical properties of a polyolefin, such as the melting temperature and the rigidity, are dependent on the nature of its sequence distribution. Accurate modeling of sequence length distribution (SLD) is important in precisely tuning and optimizing the properties of polymers produced. In this article, we proposed a model to predict the molecular weight distribution (MWD) and SLD for olefin copolymerization with vanadium-based catalyst. Due to the 2,1-insertion of α-olefin with vanadium-based catalyst, the SLD is expressed by uninterrupted methylene sequence distribution instead of conventional triad sequence distribution. To obtain a reliable model, parameter estimation with experimental data is first conducted. The SLD model along with the estimated kinetic parameters can be used to predict unmeasurable sequence length fraction. For the experimental conditions studied, the average methylene sequence length is predicted to change from 10 to 4 units as the propylene/ethylene mole feed ratio increases from 1.1 to 3.4.