4-■并联机构的动力学性能指标分析

利用位置反解分析4-■并联机构的空间位形,并采用虚设机构法和影响系数矩阵法建立Jacobian和Hessian矩阵,将Hessian矩阵引入全域性能指标中,不同于以往仅采用Jacobian矩阵作为评价机构性能的指标,使得对机构的动力学性能评价更加全面。对全新的4-■ 4自由度并联机构进行速度、加速度和惯性力性能指标分析,给出三项指标的性能图谱。改变机构尺寸,搜索4-■并联机构在不同机构尺寸下的工作空间,在可达工作空间内讨论机构尺寸变化对机构性能的影响,重点讨论Jacobian矩阵和Hessian矩阵对机构加速度性能的影响程度。对比加速度偏差的具体数值,发现Hessian矩阵对机构的加速度性能有着更重要的影响。最后利用Matlab软件对机构进行模型仿真。

太阳光谱辐射计的信号传递与性能表征模型研究

太阳光谱辐射计作为一种专用光谱辐射测量仪器,对于其宽谱段和大动态范围的测量特点,准确完整地表征分光性能是十分重要的。研究内容旨在为太阳光谱辐射计的研制与验证提供明确的理论依据和测试方法,给出清晰而准确的机理模型和指标模型对光谱仪器系统的设计和评估提供指导。因此,重点阐述了光谱仪器系统的信号传递模型到性能指标模型的推导和建立过程。线谱扩展函数这种串联卷积模型能够综合反映仪器的各个元件对系统的影响,而且很容易通过窄带线谱光源测试而得到,并且线谱扩展函数矩阵能够清晰完整地给出光谱仪器的分光性能细节特性。而在线谱扩展函数的基础上再进一步提取关键几何特征,通过简单的算法定义即可得到半高全宽(FWHM),带外抑制和带外辐射这三项示性函数指标,可以很好地对分光系统的性能进行定量表征,是十分有效的光谱仪器系统性能评估的指标模型。

基于ESN的污水处理过程优化控制

针对污水处理过程能耗过高的问题,提出了一种基于状态回声网络(ESN)的在线优化控制方法。建立了污水处理过程预测模型,实现性能指标的预测;根据系统的状态以及预测的性能指标,采用ESN实时优化控制变量的设定值;将优化后的设定值传送给底层控制器进行跟踪控制。将ESN优化控制方法在污水处理过程基准仿真模型(BSM1)上进行了验证,实验结果表明,该方法不但能够满足出水水质的要求,而且降低了污水处理过程运行成本。

Methods of Validating Simulation Model and Program Design

Validating simulation model is one of the important aspects for modeling and simulation. Some methods of validating model are compared and analyzed. Several typical methods, such as TIC’s inequality coefficient, gray interconnected analysis, direct spectrum estimation, maximum entropy spectral estimation based on Burg or Marple, are chosen and programmed in C language. Some examples by using the program are given. The results show that the program is available and it is best to adopt multi methods for validating models.

Discrete element method of improved performance of railway ballast bed using elastic sleeper

With the development of high-speed and heavy-haul railway in China, problems like insufficient thickness of ballast bed and overlarge track stiffness are obvious. Ballast may break into small particles and their contact status will deteriorate under cyclic loading, resulting in ballast degradation. Discrete element method(DEM) was used to research improved performance of ballast bed using elastic sleeper. Clusters were generated by bonding spheres to model real ballasts, while broken bonds were utilized to distinguish breakage. Two kinds of ballast beds with elastic sleeper and conventional sleeper were established, respectively. After applying cyclic loading to the models, differences of mechanical properties between two models were analyzed by contrasting their dynamic behavior indexes, such as particle contact force, sleeper settlement, vibration velocity and acceleration, breakage characteristic. The results illustrate that compared with conventional sleeper, elastic sleeper increases sleeper settlement, while reduces ballast vibration and contact force between particles, which could depress ballast breakage.

Dynamic cluster member selection method for multi-target tracking in wireless sensor network

Multi-target tracking(MTT) is a research hotspot of wireless sensor networks at present.A self-organized dynamic cluster task allocation scheme is used to implement collaborative task allocation for MTT in WSN and a special cluster member(CM) node selection method is put forward in the scheme.An energy efficiency model was proposed under consideration of both energy consumption and remaining energy balance in the network.A tracking accuracy model based on area-sum principle was also presented through analyzing the localization accuracy of triangulation.Then,the two models mentioned above were combined to establish dynamic cluster member selection model for MTT where a comprehensive performance index function was designed to guide the CM node selection.This selection was fulfilled using genetic algorithm.Simulation results show that this method keeps both energy efficiency and tracking quality in optimal state,and also indicate the validity of genetic algorithm in implementing CM node selection.

Distribution of Market Share in the World Soft-Drink Industry

The distribution of market shares within an industry is a relevant performance measure for managers and policy makers, for it allow to determine whether a given industry is competitive or not. Usually, the perfect competition model is the reference to judge the efficiency of markets. However, there is enough empirical evidence that shows that one of the most evident features of global firms is that both their size and market are Zipf-distributed. In this paper, we show that the distribution of market shares in the world cola-drink market is skewed, but it does not follow Zipf＇s law, thus it is inadequate to generalize it to any kind of market.

Riccati difference equation in optimal control formagnetic bearings

A model predictive optimal control method for magnetically suspended flywheel is presented.In order to suppress the conical whirl of the rotor caused by gyroscopic effect,the synchronization error is added to the traditional quadratic performance index.The target performance index is composed of the translatory error,the synchronization error,and the control output predicted by the discrete-time state model.The optimal controller is obtained by means of iterating a Riccati difference equation(RDE).Stability of the control scheme is investigated through fake algebraic Riccati technique(FART).The robust performance of the controller with respect to control parameters is studied by simulation.Results of the simulation and experiment on a compact magnetically suspended flywheel demonstrate that the proposed controller with consideration of the synchronization error is very effective to suppress the conical whirl caused by gyroscopic effect.

A DEA MODEL FOR IDENTIFYING CRITICAL INPUT-OUTPUT PERFORMANCE MEASURES

In this paper,the authors propose a new model for identifying the critical input-output combinations for each DMU.A real-world application case of 21 international tourist hotels(ITHs) is used to illustrate the proposed approach.