双电机消失模铸造振实台振动模式及效果

试验研究了不同振动模式下双电机激振消失模铸造振动紧实台的振动特性。在分析双电机振动数学模型的基础上,测试了多种振动模式下的振动效果,结果表明,在不同振动模式下,双电机振动特性差距较大;为了较好地实现复杂消失模模样振动紧实的目的。紧实过程中,可根据铸件消失模模样的形状特点,进行振动模式的不同组合与变换,以求得满意的紧实效果。     

Permeability of coating in the lost foam casting process

This study measured the pressures developed during a filling experiment using molten grey iron in the lost foam casting (LFC) process. The measured pressures included back pressure and permeable pressure. The back pressure is created in-mould from the metal-foam interface. The permeable pressure was measured on the mould side of the coating, when gases introduced from the decomposing EPS were permeating through the coating. The permeable pressure reflected the permeability of the coating while filling molten iron. Variables, which included particle sizes, types of binders, weight per cent of binder in coatings, influenced the permeability of coating at room temperature and at casting temperature.

Coatings made from flaky alumina developed a greater total length of pore channels than those made from angular silica. Increasing the particle size of the refractory increased the permeability of the coating at room temperature. The highest permeable pressure was measured when the particle size was 74 μm and acrylic resin was used as a binder. The optimum binder content was less than 1% for flaky alumina and acrylic resin binder. The optimum coating thickness was less than 0.5 mm to develop a maximum permeable pressure associated with a minimum back pressure in the mould.     

Application of firefly algorithm with online wavelet filter in automatic generation control of an interconnected reheat thermal power system

This paper presents the implementation of the Firefly Algorithm (FA) with an online wavelet filter on the automatic generation control (AGC) model for a three unequal area interconnected reheat thermal power system. The model includes time delay, dead zone, boiler, Generation Rate Constraint (GRC), and high frequency noise components. A novel filtering technique based on wavelet transform is introduced for the purpose of removing noise(s) from the ACE signal. The performance of the filter is measured by formulating a signal integrity index. The simulation results show that the FA is able to outperform the Particle Swarm Optimization (PSO) in obtaining the minimum objective function based on Integral of Time Weighted Squared Error (ITSE). The results also shows that the proposed online wavelet filter performs with a higher degree of efficiency compared to the conventional low pass filter when the practical model of the AGC is analyzed. Further investigation by varying the GRC and time delay parameter confirms the robustness of the FA tuned controller with the online wavelet filter.     

Robust analysis and design of power system load frequency control using the Kharitonov's theorem

This paper presents a robust decentralized proportional-integral (PI) control design as a solution of the load frequency control (LFC) in a multi-area power system. In the proposed methodology, the system robustness margin and transient performance are optimized simultaneously to achieve the optimum PI controller parameters. The Kharitonov’s theorem is used to determine the robustness margin, i.e., the maximal uncertainty bounds under which the stable performance of the power system is guaranteed. The integral time square error (ITSE) is applied to quantify the transient performance of the LFC system. In order to tune the PI gains, the control objective function is optimized using the genetic algorithm (GA). To validate the effectiveness of the proposed approach, some time based simulations are performed on a three-area power system and the results are then compared with an optimal PI controller. The comparisons show that the proposed control strategy provides the satisfactory robust performance for the wide range of system parameters and load changes in the presence of system nonlinearities and is superior to the other methods.     

EPS消失模数控加工快速成形方法研究

研究了无模具条件下EPS消失模的成形方法。采用数控铣削加工成形方法,进行制动器壳体、从动齿轮轮毂和制动盘的EPS消失模加工成形试验。结果表明,采用数控加工的EPS模型其尺寸精度和表面粗糙度均满足消失模铸造的要求。     

Performance optimization of linear active disturbance rejection control approach by modified bat inspired algorithm for single area load frequency control concerning high wind power penetration

The linear active disturbance approach is employed to deal with the load frequency control issue of a single area wind power system based on doubly fed induction generator, and the performance of the control law is optimized by using the bat-inspired algorithm. The load frequency control issue has become more challenging in a complex power system based on wind energy conversion system due to the varying feature of the wind penetration, and sustaining the balance between the power generation and demand by rejecting the internal uncertainties in the process model and the external disturbances simultaneously. In the framework of the presented linear active disturbance rejection control approach, by constructing an extended state observer, the total disturbance, including all the unmodelled dynamics in the process model and the external disturbances, can be estimated in real time and then compensated by a simple linear PD control law. The controller parameters tuning is then simplified into the optimization of the two bandwidths: observer bandwidth, and the controller bandwidth. Then, this issue can be achieved by employing the heuristic modified bat inspired algorithm based on the optimization of the proposed performance index. The effectiveness of the proposed approach is validated by the extensive simulation examples of the load frequency control issue involved in the single area power system, taking into account different wind penetration, as well as the external disturbances. The performance robustness of the proposed approach against the parameters perturbation in the process model is also demonstrated via the Monte-Carlo method. The performance superiority of the proposed approach over the conventional Proportional Integral and Fuzzy-Proportional Integral based controller even in the presence of external disturbances and uncertainty in power system parameters under different cases of high wind penetration is also validated from the simulation results.     

Smoothing of PV system output by tuning MPPT control

A PV system's power output is not stable and fluctuates depending on weather conditions. Using a battery is one feasible measure to stabilize a PV system's power output, but it requires additional costs and results in additional waste of used batteries. In this paper, we propose a new measure for smoothing the short‐term change in a PV system's power output, which is performed by tuning the characteristics of Maximum Power Point Tracking (MPPT) control without additional equipment. In our proposed measure, when the insolation increases rapidly, the operation point of MPPT control changes to a new point where the maximum power is not generated with the current insolation, so that the rate of increase in the PV system's power output is limited to a certain value. In order to evaluate the effect of the proposed measure on the operation of electric power systems, we evaluated the required capacity of generators for load‐frequency control (LFC). It was revealed that the additional LFC capacity is not required even in the case where penetration of PV systems reaches 5% of the utility system's total capacity if the proposed measure is applied to all PV systems. © 2005 Wiley Periodicals, Inc. Electr Eng Jpn, 152(2): 10–17, 2005; Published online in Wiley InterScience ( www.interscience.wiley.com ). DOI 10.1002/eej.20106     

解答EASE培训课上提出的18个问题

总结了在EASE培训课上被经常提出的18个关键问题。这些问题包括软件安装方面,建模方面,出图方面,计算准确性方面,以及试听功能的调用。针对对于EASE软件有一定了解并且使用EASE软件做过一些设计的设计人员,帮助他们正确理解EASE,找到有可能被长期困扰的一些关键问题的答案。     

水泵叶轮的消失模铸造工艺

指出对于水泵叶轮这种薄壁复杂铸件来说,消失模铸造能够充分发挥其许多独特的工艺优势.阐述了ZG20MnSi钢制水泵叶轮的消失模铸造生产技术及工艺控制要点:在模样制作时,确定泡沫密度非常关键,经过试验,确定轮毂与盖板的泡沫密度为0.020g/cm3,叶片的泡沫密度为0.025g/cm3;合理设计浇注系统;正确选用耐火涂料和型砂;充分提高型砂的填充密度.采取这些工艺措施后能够减轻或消除相关铸造缺陷,从而提高复杂近净形铸钢件的质量.     

消失模法试制6缸发动机铝进气管

介绍了消失模铸造6缸发动机铝进气管的工艺：砂箱内加隔板对解决细长管件变形无明最效果，通过减小振击力和缩短振击时间可消陈铸件娈形；单组分胶粘结的进气管娄模型浇注铝合金时．腔气化滞后，有产生冷隔的危险．大量生产时宜采用热熔胶粘结；铝合金消失模铸件常见缺陷有渣孔和微漏，通过改进浇注系统可以彻底消除渣孔．现有条件下无法彻底解决微漏。