Nuclear data requirements for the ADS conceptual design EFIT: Uncertainty and sensitivity study

In this paper, we assess the impact of activation cross-section uncertainties on relevant fuel cycle parameters for a conceptual design of a modular European Facility for Industrial Transmutation (EFIT) with a “double strata” fuel cycle. Next, the nuclear data requirements are evaluated so that the parameters can meet the assigned design target accuracies. Different discharge burn-up levels are considered: a low burn-up, corresponding to the equilibrium cycle, and a high burn-up level, simulating the effects on the fuel of the multi-recycling scenario.     

Robust PID control of fully-constrained cable driven parallel robots

In this paper dynamic analysis and robust PID control of fully-constrained cable driven parallel manipulators are studied in detail. Since in this class of manipulators cables should remain in tension for all maneuvers in their workspace, feedback control of such robots becomes more challenging than that of conventional parallel robots. In this paper, structured and unstructured uncertainties in dynamics of the robot are considered and a robust PID controller is proposed for the cable robot. To ensure that all cables remain in tension internal force concept is used in the proposed PID control algorithm. Then, robust stability of the closed-loop system with proposed control algorithm is analyzed through Lyapunov direct method and it is shown that by suitable selection of the PID controller gains, the closed-loop system would be robustly stable. Finally, the effectiveness of the proposed PID algorithm is examined through experiments on a planar cable driven robot and it is shown that the proposed control structure is able to provide suitable performance in practice.     

Risk analysis: Casing-while-Drilling (CwD) and modeling approach

In today's volatile economy and uncertain drilling environment, managers are encouraged to reduce well cost and time and have implemented Casing-while-Drilling (CwD) to improve operational excellence. Risk analysis is another valid tool that can be used to improve drilling operations. This paper discusses CwD as a new technology and how its benefits can be strengthened by including risk analysis as a complementary technique. A modeling approach is presented to demonstrate how risk analysis can be applied to CwD programs and to discuss the main concerns a well planner must address to achieve a successful drilling program. The integration of both CwD and risk analysis will add value to the overall excellence of the well operation. Very little work has been done on this integration, and the hope is that this approach will be a standard practice in the future.     

Seismic performance assessment of steel moment frames with generic Locally Reinforced connections

Seismic performance of Steel Moment-Resisting Frames (SMRFs) with generic Locally-Reinforced (LR) connections has been investigated incorporating both earthquake-induced and modeling uncertainties. The LR connections were numerically modeled following the suggestions made by previous researches and were used to numerically model three buildings with various heights which were designed regarding the specifications of current standards. For reflecting the record-to-record (RTR) variability, the Incremental Dynamic Analysis (IDA) procedure was utilized within the Performance-Based Earthquake Engineering (PBEE) methodology. In this regard, the structures’ performance in a multitude of structural response levels was probabilistically assessed in “considering” and “neglecting” conditions of modeling uncertainties. For performing the modeling uncertainty analysis, a number of modeling parameters that best reflected the structures’ variability due to lack of knowledge were selected as random variables. Perturbing the modeling variables from their median values, a set of sensitivity IDAs were performed and a polynomial response surface was established. Incorporation of the response surface in conjunction with Monte Carlo simulation led, finally, to a fully probabilistic performance evaluation of the studied structures in varied structural response levels. The effect of modeling uncertainties in altering the predicted performances was found to be insignificant in the range of buildings and structural elements studied in this article.     

Robust H∞ filtering for switched linear discrete‐time systems with polytopic uncertainties

In this paper, the problem of robust H_∞ filtering for switched linear discrete‐time systems with polytopic uncertainties is investigated. Based on the mode‐switching idea and parameter‐dependent stability result, a robust switched linear filter is designed such that the corresponding filtering error system achieves robust asymptotic stability and guarantees a prescribed H_∞ performance index for all admissible uncertainties. The existence condition of such filter is derived and formulated in terms of a set of linear matrix inequalities (LMIs) by the introduction of slack variables to eliminate the cross coupling of system matrices and Lyapunov matrices among different subsystems. The desired filter can be constructed by solving the corresponding convex optimization problem, which also provides an optimal H_∞ noise‐attenuation level bound for the resultant filtering error system. A numerical example is given to show the effectiveness and the potential of the proposed techniques. Copyright © 2006 John Wiley & Sons, Ltd.     

The Effect of Uncertainties in the Kuhn-Mark-Houwink-Sakurada Constants on the Quantitative Analysis by Gel Permeation Chromatography

The effect of uncertainties in Kuhn-Mark-Houwink-Sakurada (KMHS) constants on weight average and number average molecular weights and molecular weight distributions of some poly(ethyl methacrylate) samples have been investigated. Parameters were computed by the Weiss and Cohn-Ginsberg method. Whereas errors introduced in M_w, M_n and HI values due to uncertainty in the K value are insignificant, uncertainties in the KMHS exponent present a serious problem. Deviations of ± 3% around a particular a value cause a ± 20% error in M_w and ± 15% error in M_n, values. The effect of deviations in the KMHS exponent on the HI values is dependent on the polydisperity of the sample investigated.     

一类非线性互联系统的H∞模型参考跟踪分散输出反馈模糊控制

本文对一类不确定状态不可测非线性互联系统,给出了一种基于观测器的H_∞模型参考跟踪分散输出反馈模糊控制方法.设计中,首先采用模糊不确定T-S模型对非线性互联系统进行模糊建模,在此基础上,给出模糊分散观测器的H_∞设计和基于观测器的模型参考跟踪分散模糊控制的设计.应用李亚普诺夫和线性矩阵不等式方法给出了模糊分散系统稳定的充分条件.仿真结果进一步验证了所提出的模糊分散控制方法的有效性.     

最近电压稳定临界点的两层规划模型和信赖域算法

考虑了负荷变化的不确定性,提出负荷分布范围的棱锥状模型。建立了求解最近电压稳定临界点的非线性二层规划模型,提出一种求解该问题的信赖域方法。该方法先计算已知负荷增长方向上的电压稳定临界点,然后建立只有上、下界约束的近似模型,基于信赖域方法的思想迭代搜索最近电压稳定临界点,求取临界点时考虑了发电机无功出力的限制。算例分析表明,该算法收敛速度快、鲁棒性好,全局寻优能力强,并可找出系统电压稳定的薄弱区域和母线。     

Adaptive sliding mode current control with sliding mode disturbance observer for PMSM drives

This paper focuses on the current control of a permanent magnet synchronous motor (PMSM) for electric drives with model uncertainties and external disturbances. To improve the performance of the PMSM current loop in terms of the speed of response, tracking accuracy, and robustness, a hybrid control strategy is proposed by combining the adaptive sliding mode control and sliding mode disturbance observer (SMDO). An adaptive law is introduced in the sliding mode current controller to improve the dynamic response speed of the current loop and robustness of the PMSM drive system to the existing parameter variations. The SMDO is used as a compensator to restrain the external disturbances and reduce the sliding mode control gains. Experiments results demonstrate that the proposed control strategy can guarantee strong anti-disturbance capability of the PMSM drive system with improved current and speed-tracking performance.