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共有20条相似文献,以下是第1-20项 搜索用时 125 毫秒

1.  A comparative study on thermo-economic performance between subcritical and transcritical Organic Rankine Cycles under different heat source temperatures  
   Shuangying Wu  Chun Li  Lan Xiao  Chao Liu  Yourong Li《科学通报(英文版)》,2014年第59卷第33期
   In this paper, the net power output, exergy efficiency and levelized energy cost of system were selected as performance indicators for assessing Organic Rankine Cycle (ORC). Firstly, the turbine inlet temperature and pressure meeting the requirement of pinch point temperature difference of evaporator in transcritical ORC (trans-ORC) were determined based on performance opti- mization. Subsequently, the thermo-economic performance of a subcritical ORC (sub-ORC) using R601 as working fluid and a trans-ORC using R134a as working fluid were compared under different heat source temperatures and a fixed outlet temperature of flue gas. Results show that for trans-ORC, when the pinch point temperature difference of evaporator lies between the inlet and outlet of evaporator, a lower inlet pressure of turbine is favorable; when the pinch point temperature difference of evaporator is located at the outlet of evaporator, there exists an optimal inlet pressure of turbine. Either for sub-ORC or trans-ORC, the net power output increases and levelized energy cost decreases with the increase in heat source temperature. For sub-ORC, exergy efficiency of system increases monotonously with heat source temperature, while for trans-ORC, exergy efficiency of system grows up firstly and then reduces (or keeps constant) with the increasing of heat source tem- perature. Moreover, for net power output and exergy efficiency of system, there exist a range of heat source temperatures making trans-ORC better than sub-ORC, and the heat source temperature region extends with the increase in pinch point temperature difference of evapo- rator. For levelized energy cost of system, the sub-ORC is always superior to trans-ORC.    

2.  Intelligent Scheduling of Public Traffic Vehicles Based on a Hybrid Genetic Algorithm  
   张飞舟  ;曹学军  ;杨东凯《清华大学学报》,2008年第13卷第5期
   A genetic algorithm (GA) and a hybrid genetic algorithm (HGA) were used for optimal scheduling of public vehicles based on their actual operational environments. The performance for three kinds of vehicular levels were compared using one-point and two-point crossover operations. The vehicle scheduling times are improved by the intelligent characteristics of the GA. The HGA, which integrates the genetic algorithm with a tabu search, further improves the convergence performance and the optimization by avoiding the premature convergence of the GA. The results show that intelligent scheduling of public vehicles based on the HGA overcomes the shortcomings of traditional scheduling methods. The vehicle operation management efficiency is improved by this essential technology for intelligent scheduling of public vehicles.    

3.  Research on the Winding/Unwinding Control System Based on Fuzzy Control Theory  
   何勇  李艳  高中秋  成玲《东华大学学报(英文版)》,2008年第25卷第4期
   A fuzzy controller of the winding/unwinding control system used in jig-dyeing machine is introduced, which is superior to the one with conventional optimal PID controller in convergence speed and stability. Its mathematical model and transfer function are presented based on mechanism of the winding/unwinding control system. Simulation of the fuzzy controller carried out in the MATLAB (Simulink) environment proves that the control system based on fuzzy controller is superior in quality, precision and operation to a conventional optimal PID controller. The outlined experimental results also show the effectiveness and the robustness of the fuzzy PID controller in good dynamic performance, high robustness to parameter variation and disturbance.    

4.  Task Space Division and Trajectory Planning for a Flexible Macro-Micro Manipulator System  
   罗凌智 张宇 孙增圻《清华大学学报》,2007年第12卷第5期
   This paper deals with a flexible macro-micro manipulator system, which includes a long flexible manipulator and a relatively short rigid manipulator attached to the tip of the macro manipulator. A flexible macro manipulator possesses the advantages of wide operating range, high speed, and low energy consumption, but the disadvantage of a low tracking precision. The macro-micro manipulator system improves tracking performance by compensating for the endpoint tracking error while maintaining the advantages of the flexible macro manipulator. A trajectory planning scheme was built utilizing the task space division method. The division point is chosen to optimize the error compensation and energy consumption for the whole system. Then movements of the macro-micro manipulator can be determined using separate inverse kinematic models. Simulation results for a planar 4-DOF macro-micro manipulator system are presented to show the effectiveness of the control system.    

5.  Design of PID controller with incomplete derivation based on differential evolution algorithm  被引次数:5
   Wu Lianghong  Wang Yaonan  Zhou Shaowu  Tan Wen《系统工程与电子技术(英文版)》,2008年第19卷第3期
   To determine the optimal or near optimal parameters of PID controller with incomplete derivation, a novel design method based on differential evolution (DE) algorithm is presented. The controller is called DE-PID controller. To overcome the disadvantages of the integral performance criteria in the frequency domain such as IAE, ISE, and ITSE, a new performance criterion in the time domain is proposed. The optimization procedures employing the DE algorithm to search the optimal or near optimal PID controller parameters of a control system are demonstrated in detail. Three typical control systems are chosen to test and evaluate the adaptation and robustness of the proposed DE-PID controller. The simulation results show that the proposed approach has superior features of easy implementation, stable convergence characteristic, and good computational efficiency. Compared with the ZN, GA, and ASA, the proposed design method is indeed more efficient and robust in improving the step response of a control system.    

6.  Analytical Analysis on the Structure of a Typical Fuzzy On - Off Controller  
   丁永生  任立红  邵世煌《东华大学学报(英文版)》,1999年第1期
   The analytical structure of a typical fuzzy on - off controller that employs three or more triangular Input fuzzy sets, Zadeh fuzzy logic AND operator, fuzzy rules with singleton output fuzzy sets, and the centriod defuzzifier is Investigated in this paper. The analytical expressions of the variable gains of the fuzzy controller are derived. The resulting explicit structure shows that the fuzzy controller is accurately a nonlinear PD - like controller with gains continuously changing with system output in different regions of input space.    

7.  Improved genetic operator for genetic algorithm  
   林峰 杨启文《浙江大学学报(自然科学英文版)》,2002年第3卷第4期
   The mutation operator has been seldom improved because ressearchers hardly suspect its ability to prevent genetic algorithm(GA) from converging prematurely.Due to its importance to GA,the authors of this paper study influence on the diversity of genes in the same locus,and point out that traditional mutation,to some extent,can result in premature convergence of genes(PCG) in the same locus.The above drawback of the traditional mutation operator causes the loss of critical alleles.Inspired by digital technique,we introduce two kinds of boolean operation into GA to develop a novel mutation operator and discuss its contribution of preventing the loss of critical alleles.The experimental results of function optimizatioin show that the improved mutation operator can effectively prevent premature convegence,and can provide a wide selection range of control parameters for GA.    

8.  SELF-LEARNING FUZZY CONTROL RULES USING GENETIC ALGORITHMS  
   Fang Jian'an Shao Shihuang《东华大学学报(英文版)》,1995年第1期
   This papcr presents a new genetic algorithms(GAs)-based method for self-learniag fuzzy control rules. An improved GA is used to learn to optimally select the fuzzy membership functions of the linguistic labels in the condition portion of each rule, and to automatically generate fuzzy control actions under each condition. The dynamics of the controlled system is unknown to the GA. The only information for evaluating performance is a failure signal indicating that the controlled system is out of control. We compare its performance with that of other learning methods for the same problem. We also examine the ability of the algorithm to adapt to changing conditions. Simulation results show that such an approach for self-learning fuzzy control rules is both effective and robust.    

9.  A Neurocomputing Model for Binary Coded Genetic Algorithm  
   Gong Daoxiong  Ruan Xiaogang《中国工程科学》,2004年第2卷第3期
   A neurocomputing model for Genetic Algorithm (GA) to break the speed bottleneck of GA was proposed. With all genetic operations parallel implemented by NN-based sub-modules, the model integrates both the strongpoint of parallel GA (PGA) and those of hardware GA (HGA). Moreover a new crossover operator named universe crossover was also proposed to suit the NN-based realization.This model was tested with a benchmark function set, and the experimental results validated the potential of the neurocomputing model.The significance of this model means that HGA and PGA can be integrated and the inherent parallelism of GA can be explicitly and farthest realized, as a result, the optimization speed of GA will be accelerated by one or two magnitudes compered to the serial implementation with same speed hardware, and GA will be turned from an algorithm into a machine.    

10.  Intelligent coordinated control of power-plant main steam pressure and power output  
   刘红波  李少远  柴天佑《系统工程与电子技术(英文版)》,2004年第15卷第3期
   An intelligent coordinated control strategy has been proposed and successfully applied to a 300MW boiler-turbine unit i. e. Unit 1 of Yuanbaoshan power plant in China. Load following operation of coal-fired boiler-turbine unit in the power plant leads to changes in operating points which result in nonlinear variations of the plant variables and parameters. For the variation of operating condition and slowly varying dynamics, an intelligent control scheme has been developed by combining fuzzy self-tuning with adaptive control and auto-tuning techniques. As there exist strong couplings between control loops of main steam pressure and power output in the unit, a new design for static decoupler aimed at decoupling for setpoints and unmeasured pulverized coal disturbance of the system at the same time is presented. Satisfactory industrial application results show that such a control system has enhanced adaptability and robustness to the complex process, and better control performance and high economic benefi    

11.  Immune Genetic Algorithm for Optimal Design  被引次数:3
   杨建国  李蓓智  项前《东华大学学报(英文版)》,2002年第19卷第4期
   A computing model employing the immune and genetic algorithm (IGA) for the optimization of part design is presented. This model operates on a population of points in search space simultaneously, not on just one point. It uses the objective function itself, not derivative or any other additional information and guarantees the fast convergence toward the global optimum. This method avoids some weak points in genetic algorithm, such as inefficient to some local searching problems and its convergence is too early. Based on this model, an optimal design support system (IGBODS) is developed. IGBODS has been used in practice and the result shows that this model has great advantage than traditional one and promises good application in optimal design.    

12.  Risk Control of Transmission Line Overload for Wind-Integrated Power Systems  
   李雪  ;路攀  ;王春亮《东华大学学报(英文版)》,2014年第2期
   With the rapid development of the wind generation, uncertainties of random wind and load bring some inevitable impacts on the security of power system. Once the uncertainty causes line power to exceed its limit, line overload will occur. The paper presents the risk control of transmission line overload for windintegrated power systems. Firstly, a risk control model of line overload is proposed considering the uncertainties of loads , generator outputs and wind powers. The generation cost and security level of system associated with overload can be optimally controlled. Then path following interior point method is employed to carry out the optimal control. Finally the simulation is made on the modified IEEE-30 bus system. Results show that the risk of line overload is effectively reduced through the optimization of control variables.    

13.  Temperature Control and Simulation of TemperatureAltitude Test System  
   Yuan Lingshuang  Liu Meng  Wang Jun《中国工程科学》,2007年第5卷第3期
   The temperatureAltitude Test System (TATS) supplies various testing environments. The traditional PID method controls the temperature in TATS TemperaturePressure Cabin (TPC) over a long adjusting time and with a large overshoot. In order to solve this problem simply, a temperature control strategy with temperature difference corresponding factors is presented through a dynamic analysis and modeling of TPC temperature change. The TPC temperature descending process is simulated, and the results show that this control strategy can allot the proportion of PID heating controller and PID cooling controller in the whole control process and TPC temperature can be controlled at a set point quickly and effectively.    

14.  Effects of natural covers on soil evaporation of the shelterbelt along the Tarim Desert Highway  
   《科学通报(英文版)》,2008年第Z2期
   The control of soil evaporation is one of important approaches to save water. The artificially simulated evaporation experiments have been conducted in the hinterland of the Taklimakan Desert to reveal the effects of the natural covers on the soil evaporation of the Tarim Desert Highway shelterbelt as well as provide some insights in the efficient utilization of water resources and optimization of irrigation systems. The results showed that (1) All the covers, including the sand deposit, the salt crust, the litter, the sand-litter mixed layer and so on, can significantly inhibit the soil water evaporation. Specifically, the daily evaporation, the total evaporation, and the evaporation rate in covered sands were much smaller than that of sands without cover. The cover inhibition effects increased with the cover thickness. Particularly, the soil evaporation of the covered sands was less affected by external and internal factors than that of the bare sands. Moreover, the variation of daily evaporation of covered sands was smaller than that of bare sands. The cumulative evaporation varied linearly with time in the covered sands whereas it varied logarithmically in the bare sands. In addition, the soil evaporation in the bare sands showed significantly different characteristics in the early and late stages of the evaporation. (2) All the covers exhibited the significant inhibiting effect on the soil evaporation, and the inhibition efficiency increased logarithmically with the cover thickness. However, as the cover thickness was above a certain value, the increase in the inhibition efficiency was slow. Particularly, at a cover thickness of 2 cm, there was no obvious difference in the inhibition efficiency among all kinds of covers. The maximum inhibition efficiency as calculated from the daily evaporation on the first day of irrigation was: sand-litter mixed layer (79.92%) > litter layer (78.96%) > salt crust (75.58%) > sand bed (74.11%), whereas the average inhibiting efficiency as calculated from the cumula    

15.  A Maximum Principle for Fully Coupled Forward-Backward Stochastic Control System Driven by Lvy Process with Terminal State Constraints  
   Hong Huang  Xiangrong Wang  Meijuan Liu《系统科学与复杂性》,2018年第31卷第4期
   This paper is concerned with a fully coupled forward-backward stochastic optimal control problem where the controlled system is driven by L′evy process, while the forward state is constrained in a convex set at the terminal time. The authors use an equivalent backward formulation to deal with the terminal state constraint, and then obtain a stochastic maximum principle by Ekeland's variational principle. Finally, the result is applied to the utility optimization problem in a financial market.    

16.  LINGUISTIC SELF-ORGANIZING PROCESS CONTROLLER USING GENETIC ALGORITHM  
   方远  丁纪凯《东华大学学报(英文版)》,1997年第2期
   A linguistic self-organizing controller using genetic algorithm is presented, whose control policy is able to generate, develop and improve. The scaling factors can be chosen automatically.Optimizing the scaling factors by genetic algorithm instead of trial or experimental method which is often used in conventional linguistic self-organizing controller eliminates the drawback of an exhausive search of the GE*GC*GU space by human operator, and also produces the better system response and a set of better control rules. A number of simulations on linear dynamic systems as well as non-linear systems such as second order process with a random disturbance, third order process with time lags and the cart-pole balancing problem etc. are described in this paper, which shows that the controller has strong adaptive properties and gives better performance than that of the conventional linguistic self-organizing controller.    

17.  Stochastic maximum principle for mixed regular-singular control problems of forward-backward systems  
   Feng Zhang《系统科学与复杂性》,2013年第26卷第6期
   This paper considers a stochastic optimal control problem of a forward-backward system with regular-singular controls where the set of regular controls is not necessarily convex and the regular control enters the diffusion coefficient. This control problem is difficult to solve with the classical method of spike variation. The authors use the approach of relaxed controls to establish maximum principle for this stochastic optimal control problem. Sufficient optimality conditions are also investigated.    

18.  Sampled-data Iterative Learning Control for Singular Systems  
   孙鹏  FANG Zhong  Han Zhengzhi《高技术通讯(英文版)》,2004年第10卷第3期
   Sampled-data iterative learning control (SILC) for singular systems is addressed for the first time. With the introduction of the constrained relative degree, an SILC algorithm combined with a feedback control law is proposed for singular systems. Convergence of the algorithm is proved in sup-norm, while the conventional convergence analysis is in λ-norm. The final tracking error uniformly converges to a small residual set whose level of magnitude depends on the system dynamics and the sampling-period. Due to inequalities to estimate the level of the existing results of SILC, convergence is guaranteed not only at the sampling instants but on the entire operation interval, so that the inter-sample behavior is guaranteed, which is more practical for real implementation.    

19.  Vital basic research on modern power systems geared to 21st century  被引次数:1
   LU Qiang  MEI Shengwei《自然科学进展(英文版)》,2000年第10卷第8期
   Through analysis of the demand on national modern power systems, a proposal is made to establishand develop basic theories for collapse prevention and optimal operation of large power systems in the 21st century, including three main parts: large system stability theory, nonlinear control theory, and real time simulation and strategic decision systems. The basic features of large power systems are first discussed. Then, by summarizing the research results in this field, the main framework of the above basic theories and the related important scientific problems are systematically described. Their current development conditions and possible research directions are also discussed.    

20.  Heuristic based data scheduling algorithm for OFDMA wireless network  
   Guo Kunqi  Sun Lixin  Jia Shilou  Yu Xiaoyang《系统工程与电子技术(英文版)》,2008年第19卷第1期
   A system model based on joint layer mechanism is formulated for optimal data scheduling over fixed point-to-point links in OFDMA ad-hoc wireless networks. A distributed scheduling algorithm (DSA) for system model optimization is proposed that combines the randomly chosen subcarrier according to the channel condition of local subcarriers with link power control to limit interference caused by the reuse of subcarrier among links. For the global fairness improvement of algorithms, a global power control scheduling algorithm (GPCSA) based on the proposed DSA is presented and dynamically allocates global power according to difference between average carrier-noise-ratio of selected local links and system link protection ratio. Simulation results demonstrate that the proposed algorithms achieve better efficiency and fairness compared with other existing algorithms.    

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