基于模糊控制的双闭环直流可逆调速系统的设计

对于双闭环直流可逆调速系统,提出了一种将模糊控制与常规PI控制相结合应用在转速环调节器设计的方法。根据工程经验与专家知识所确定的模糊控制规则,进行模糊推理,实现转速环调节器参数的动态整定。应用Matlab软件构建了双闭环直流可逆调速系统的仿真模型,并对转速环分别采用模糊PI控制器和常规PI控制器的直流可逆调速系统分别进行仿真实验并对比结果。从仿真结果可以得出采用模糊控制可以对直流可逆调速系统的动态与静态特性、抗扰性能、恢复性能以及跟踪性能有比较明显的改善与提高。     

基于单神经元PID的直流脉宽调速系统研究

针对传统直流调速系统存在因PID控制器参数固定而导致调速性能差的问题,提出了基于单神经元PID的双闭环直流脉宽调速系统的设计方法,即采用单神经元PID控制器替代传统的转速PI调节器,并用S函数编写该控制器的算法程序。Matlab仿真结果表明,基于单神经元PID的双闭环直流脉宽调速系统具有较快的响应速度和较强的抗干扰能力,调速性能得到了较好的改善。     

直流双闭环调速系统及其模糊控制的仿真

给出了常规直流双闭环调速系统的仿真模型,采用Matlab对该模型进行了仿真,得出结论:常规直流双闭环调速系统具有较好的动态与静态特性,可以很好地抑制扰动量对电动机转速的影响,但该系统依赖精确数学模型,在增加解决环节的同时,系统模型趋于复杂,可能还会影响系统的可靠性。在该分析结果的基础上,提出了一种基于模糊控制+PI转速调节器的直流双闭环调速系统的设计方案,该方案中电流环仍采用常规PI调节,转速环改为模糊控制器与常规PI调节分时作用方式。仿真结果表明,引入模糊控制器的新系统响应速度高、过渡稳定、系统超调得到改善。     

直流电机双闭环调速系统

采用工程设计方法对双闭环直流调速系统进行辅助设计,选择调节器结构,进行参数计算和近似校验.并建立起制动、抗电网电压扰动和抗负载扰动的Simulink仿真模型.分析转速和电流的仿真波形,并进行调试,使双闭环直流调速系统趋于完善、合理。     

基于Matlab的双闭环直流调速系统的仿真

针对直流电机的快速起制动、突加负载和动态速降小等特点,首先建立了转速、电流双闭环直流调速系统;然后为了使系统无静差,设计了转速和电流调节器(PI调节器);最后在Matlab/Simulink中,采用Power System模块搭建了转速电流双闭环控制直流调速系统仿真模型,仿真结果可以直观的观察到转速、电流双闭环调速系统的启动过程。     

基于模糊PI控制的无刷直流电机调速系统仿真

针对传统PI控制方法在对稀土永磁无刷直流电动机进行控制时鲁棒性差、精度低等缺点,提出了一种参数自整定模糊PI控制方法,即采用传统的PI控制与模糊控制相结合的新型控制方法。将方法应用于永磁无刷直流电动机双闭环调速系统的转速闭环中,并利用MATLAB软件中的模糊控制工具箱进行了系统的辅助设计与仿真。仿真结果表明,参数自整定模糊PI控制方法改善了电机的动静态性能,系统的鲁棒性和精度也大大提高。     

动力集中型列车调速系统仿真研究

介绍了采用电流、转速双闭环进行直流调速的方法,分别对电流和速度调节器进行了设计,描述了系统的组成及其数学模型。采用MATLAB中SIMULINK仿真软件,对动力集中型SS9(韶山9电力机车)直流调速系统进行建模仿真,仿真结果与实际数据相吻合。     

直流调速系统广义通用模型控制器的设计及应用

在直流调速系统中,转速、电流双闭环调速系统是应用最广的直流调速系统,设想应用Lie导数概念结合通用模型控制器对于直流调速系统的电流调节器和转速调节器进行设计,可以将被控对象的模型嵌入到控制器中,适当地选择主导极点可以获得比较好的调节品质,仿真结果验证了所设计的控制器的有效性.     

直流电机神经元PID调速系统设计与仿真

针对传统PI双闭环直流电机调速系统存在响应速度慢、超调量大、抗干扰能力及自适应能力差等问题,提出了一种双闭环直流电机调速系统的神经元PID转速调节器设计方法。该转速调节器采用神经元控制器和比例控制相结合进行设计,从而构成了一种具有自学习、自适应能力的神经元PID控制器,然后与传统单神经元PID设计的转速调节器控制效果进行了对比。结果表明,基于神经元PID转速调节器的双闭环直流电机调速系统具有较快的响应速度、良好的动态和静态稳定性、较强的自适应能力和抗干扰能力。     

基于模糊控制的双闭环直流调速系统控制器设计研究

介绍了基于模糊控制的双闭环直流调速系统控制器的设计方案,并比较分析了传统PI与模糊控制的实例。提供了对传统直流双闭环调速系统的一种改进方案。     

Vague集向Fuzzy集转化的一种新方法

提出Vague值向Fuzzy值转化的实用方法的定义。针对文献[6]中的一个Vague值向Fuzzy值转化的均值修正法,提出了加权均值修正法,并证明了这种方法同样是Vague值向Fuzzy转化的一种非常实用的方法。     

The importance of introducing a waiting time for Lattice Monte Carlo simulations of a polymer translocation process

For a standard Lattice Monte Carlo (LMC) simulation of a random walker subject to a bias, it is impossible to obtain both a correct mean velocity and diffusion coefficient. To correct this, a modified LMC algorithm has been developed where the introduction of a probability of remaining in the current state allows for a distribution of intervals between jumps. In this paper, we demonstrate the impact of this modification for a first-passage problem: the translocation of a polymer through a nanopore. We find that while either approach yields the correct mean first-passage time, the incorporation of a waiting time is necessary to obtain the correct spread of times.     

A disruption recovery plan in a three-stage production-inventory system

This paper proposes a recovery plan for managing disruptions in a three-stage production-inventory system under a mixed production environment. First, a mathematical model is developed to deal with a disruption at any stage while maximizing total profit during the recovery-time window. The model is solved after the occurrence of a disruption event, with changed data used to generate a revised plan. We also propose a new and efficient heuristic for solving the developed mathematical model. Second, multiple disruptions are considered, where a new disruption may or may not affect the recovery plans of earlier disruptions. The heuristic, developed for a single disruption, is extended to deal with a series of disruptions so that it can be implemented for disruption recovery on a real-time basis. We compare the heuristic solutions with those obtained by a standard search algorithm for a set of randomly generated disruption test problems, and that show the consistent performance of our developed heuristic with lower computational times. Finally, some numerical examples and a real-world case study are presented to demonstrate the benefits and usefulness of our proposed approach.     

The conversion of a dynamic B-spline curve into piecewise polynomials in power form

The evaluation of points and the computations of inflection points or cusps on a curve are often necessary in CAGD applications. When a curve is represented in a B-spline form, such computations can be made easier once it is transformed into a set of piecewise polynomial curves in power form. The usual practice of the transformation of a B-spline curve into a set of piecewise polynomial curves in power form is done either by a knot refinement followed by basis conversions, or by applying a Taylor expansion on each knot span of a B-spline curve.Presented in this paper is a new algorithm to convert a B-spline curve into a set of piecewise polynomial curves in power form. Experiment shows that the proposed algorithm significantly outperforms the conventional approach when one or more control points of a B-spline curve are continuously moving.     

Monocular Vision for Mobile Robot Localization and Autonomous Navigation

This paper presents a new real-time localization system for a mobile robot. We show that autonomous navigation is possible in outdoor situation with the use of a single camera and natural landmarks. To do that, we use a three step approach. In a learning step, the robot is manually guided on a path and a video sequence is recorded with a front looking camera. Then a structure from motion algorithm is used to build a 3D map from this learning sequence. Finally in the navigation step, the robot uses this map to compute its localization in real-time and it follows the learning path or a slightly different path if desired. The vision algorithms used for map building and localization are first detailed. Then a large part of the paper is dedicated to the experimental evaluation of the accuracy and robustness of our algorithms based on experimental data collected during two years in various environments.     

Catadioptric Projective Geometry

Catadioptric sensors are devices which utilize mirrors and lenses to form a projection onto the image plane of a camera. Central catadioptric sensors are the class of these devices having a single effective viewpoint. In this paper, we propose a unifying model for the projective geometry induced by these devices and we study its properties as well as its practical implications. We show that a central catadioptric projection is equivalent to a two-step mapping via the sphere. The second step is equivalent to a stereographic projection in the case of parabolic mirrors. Conventional lens-based perspective cameras are also central catadioptric devices with a virtual planar mirror and are, thus, covered by the unifying model. We prove that for each catadioptric projection there exists a dual catadioptric projection based on the duality between points and line images (conics). It turns out that planar and parabolic mirrors build a dual catadioptric projection pair. As a practical example we describe a procedure to estimate focal length and image center from a single view of lines in arbitrary position for a parabolic catadioptric system.     

An energy efficient re-access scheme for data caching in data broadcast of a mobile computing environment

Data caching is used to improve the response time and the power consumption of a mobile client in a mobile computing environment. To enhance the performance of data caching, one needs to improve the hit ratio and to reduce the cost in processing a cache miss. In a mobile computing environment, a cached data item of a mobile client needs to remain up-to-date with respect to its corresponding data item in the server. A cached data item which is out of date is called a cached invalidated data item. Accessing a cached invalidated data item can be regarded as processing a cache miss. To access a cached invalidated data item, a mobile client needs to download the new content of the data item from the broadcast channel. This operation is called a re-access operation in this paper. Re-accessing a cached invalidated data item incurs large tuning time overhead. In this paper, we propose a re-access scheme that reduces this overhead by allowing a mobile client to access a cached invalidated data item from the broadcast channel without accessing indices. We analyze the performance of the proposed scheme and validate the analysis through experiments. The experiments showed that the proposed scheme significantly reduces the tuning time of a mobile client. Furthermore, the proposed scheme is robust in the sense that it allows changes on the broadcast structure in data broadcasting.     

Reliability analysis of a repairable duplex system

We analyse the survival time of a repairable duplex system characterised by cold standby and by a pre-emptive priority rule. We allow general probability distributions for failure and repair. Moreover, an important realistic feature of the system is the general assumption that the non-priority unit has a memory. This combination of features has not been analysed in the previous literature. Our (new) methodology is based on a concatenation of a Cauchy-type integral representation of the modified Heaviside unit-step function and a two-sided stochastic inequality. Finally, we introduce a security interval related to a security level and a suitable risk-criterion based on the survival function of the system. As a practical application, we analyse some particular cases of the survival function jointly with the security interval corresponding to a security level of 90.     

A Combined Feedforward–Feedback Control Strategy for Improving the Dynamics of a Flexible Mechanism

Modern high-speed mechanisms often experience undesirable vibrations,which may render a required accuracy unattainable or, even worse, leadto a failure of the whole process. Instead of suppressing the vibrationby a stiffer design, active control methods may greatly improve thesystem performance and lead the way to a reduction of the mechanism'sweight.We investigate a four-bar-linkage mechanism and show that byintroducing an additional degree of freedom for a controlled actuatorand providing a suitable control strategy, the dynamically inducedinaccuracies can be substantially reduced and new reference paths bedescribed. The modeling of the four-bar-linkage mechanism as a hybridmultibody system and the modeling of the complete system including theactuator is briefly explained. From the combined feedforward–feedbackoptimal control approach presented in [11], a time-varying outputcontrol law is derived that leads to a very good system performancefor both a regulating and a tracking problem. The experimental resultsshow the effectiveness of the applied control strategies.