振动沉拔桩机系统参数估计的计算机仿真

对振动沉拔桩机的振动进行了分析,建立了系统的动力学数学模型,用MATLAB语言编写了系统参数估计的仿真程序,以实例进行了计算,验证了系统参数估计的可行性。     

Prediction and simulation errors in parameter estimation for nonlinear systems

This article compares the pros and cons of using prediction error and simulation error to define cost functions for parameter estimation in the context of nonlinear system identification. To avoid being influenced by estimators of the least squares family (e.g. prediction error methods), and in order to be able to solve non-convex optimisation problems (e.g. minimisation of some norm of the free-run simulation error), evolutionary algorithms were used. Simulated examples which include polynomial, rational and neural network models are discussed. Our results—obtained using different model classes—show that, in general the use of simulation error is preferable to prediction error. An interesting exception to this rule seems to be the equation error case when the model structure includes the true model. In the case of error-in-variables, although parameter estimation is biased in both cases, the algorithm based on simulation error is more robust.     

基于非线性最小二乘法的热电厂状态估计

目前,状态估计技术广泛运用于以数学、控制工程和自动化为基础理论的各个行业中。为了解决热电系统运行参数采集过程中出现的数据不全、精度不高、数据不和谐和出现坏点的问题,对状态估计技术在热电系统中的应用进行了研究,提出了一套以非线性最小二乘法为基础的状态估计算法,并进行了实例分析。研究结果表明,通过运用状态估计技术可以补平采集数据的缺失点,提高数据采集精度,节省采集终端投资和项目工程实施量,保障后续高级软件对热电系统分析评估的可靠性。     

Unmanned coaxial rotor helicopter dynamics and system parameter estimation

A numerical model that estimates the parameters of a small, unmanned coaxial rotor helicopter with a takeoff mass of 11.9 kg was developed. The modeled coaxial rotor helicopter did not have any additional damping to its dynamics such as a stabilizer bar or external gyro, which are common in commercial hobby helicopter models. Therefore, any sinusoidal actuator input from manual flight led to a large deviation of attitude rates, resulting in uncontrollable situations. A feedback attitude controller was included during test flights and parameter estimation to address this problem. Time domain experimental data were used to help estimate and validate the parameters of the helicopter. Attitude responses predicted by the model show extremely small discrepancies with experimental data. Therefore, the developed numerical model can be used for coaxial rotor helicopter controller design and other simulation purposes.     

基于参数估计的光纤水听器解调系统研究

研究并实现了可工程应用的光纤水听器解调系统,采用相除查找表的PGC解调方案和逐步参数估计的参数提取方法.从理论上详细阐述了参数提取方法原理,并从实验上分析了该方法的稳定性和有效性.实验测试表明1倍频/2倍频相位延迟的提取精度优于5％.光强、伴生调幅和角度修正因子的估算精度分别达到0.5％,2.5％和5％,能够满足实际工程应用要求.所研制的光纤水听器解调系统解调结果谐波分量较少,失真小.相比于标准压电水昕器系统,具有很好的线性度.解调系统噪声本底达到- 90 dB/Hz@ 100 Hz和- 95 dB/Hz@1 kHz.10 h连续测试,SINAD方差小于1 dB,THD方差约为2 dB,表明系统具有较好的稳定性.上述技术指标,达到了目前工程应用要求.     

基于 IESPSO 的舵机倾转矢量动力系统建模与参数辨识

针对在旋翼动态时产生的外力矩影响下,倾转矢量动力系统中的舵机系统模型辨识精度低、实际响应难以估计的问题,本文将舵机外力矩作为扰动噪声纳入辨识环节,构建系统模型,并提出了一种基于改进生态系统粒子群优化(IESPSO)的倾转旋翼舵机系统参数辨识方法。为确保试验稳定安全进行,本文设计了倾转矢量动力系统辨识平台,进行参数辨识试验。试验结果表明,在旋翼动态时产生的外力矩噪声影响下,IESPSO相对于粒子群优化法、生态系统粒子群优化法与递推最小二乘法,均方根误差降低了1.46%,1.79%与56.37%,辨识精度有明显提升,并具备更快的寻优收敛速度。在修改搜索空间后,IESPSO仍具有较高的寻优精度,避免了在宽搜索空间下无法快速搜索至较优可行解的问题。     

火电厂热工参数软测量技术的发展和现状

影响火力发电运行安全和经济性的重要因素之一是许多重要技术参数和经济参数，难以在线实时测量。针对某些热工参数难以准确在线实时测量的影响，概括和总结了国内火电厂热工变量软测量技术的发展和现状。以烟气含氧量、飞灰含炭量、球磨机负荷为例，着重分析和总结了其测量的现状、软测量建模方法和二次变量的选取，并概括了国内现有的其他热工参数软测量技术，对火电厂热工参数软测量技术的发展具有一定的指导意义，对热工控制系统的优化具有一定的参考价值。     

Development of enhanced ESP system through vehicle parameter estimation

In this research, an enhanced lateral stability control system has been developed for a vehicle. The system consists of a vehicle parameter estimation part and an enhanced ESP control logic part. The vehicle parameter estimation was conducted by considering the physical relationship among the longitudinal dynamic components. The enhanced ESP logic was designed so that the controller gains change adaptively to the vehicle parameter variation. All the system components were tested in a simulation environment, while the vehicle mass estimation algorithm was also tested in the field. The results indicated that the lateral vehicle stability limit can be improved with the designed ESP system. This paper was presented at the 4th Asian Conference on Multibody Dynamics(ACMD2008), Jeju, Korea, August 20–23, 2008. Kihong Park received his B.S. degree in Mechanical Design & Production Engineering from Seoul National University in 1986. He then received his M.S. and Ph.D. degrees in Mechanical Engineering from Cornell University in 1990 and 1994, respectively. He is currently a professor at the School of Mechanical and Automotive Engineering at Kookmin University in Seoul, Korea. His main research interest is chassis control and intellegent vehicle design.     

Integrated power and single axis attitude control system with two flywheels

The existing research of the integrated power and attitude control system(IPACS) in satellites mainly focuses on the IPACS concept,which aims at solving the coupled problem between the attitude control and power tracking.In the IPACS,the configuration design of IPACS is usually not considered,and the coupled problem between two flywheels during the attitude control and energy storage has not been resolved.In this paper,an integrated power and single axis attitude control system using two counter rotating magnetically suspended flywheels mounted to an air table is designed.The control method of power and attitude control using flywheel is investigated and the coupling problem between energy storage and attitude control is resolved.A computer simulation of an integrated power and single axis attitude control system with two flywheels is performed,which consists of two counter rotating magnetically suspended flywheels mounted to an air rotary table.Both DC bus and a single axis attitude are the regulation goals.An attitude & DC bus coordinator is put forward to separate DC bus regulation and attitude control problems.The simulation results of DC bus regulation and attitude control are presented respectively with a DC bus regulator and a simple PD attitude controller.The simulation results demonstrate that it is possible to integrate power and attitude control simultaneously for satellite using flywheels.The proposed research provides theory basis for design of the IPACS.     

Optimal thermo-economic design of a PAFC-ORC combined power system

Journal of Mechanical Science and Technology - Phosphoric acid fuel cells (PAFCs) are appropriate for applications that require high-quality power because of their high reliability. We propose a...     

Constitutive parameter estimation of a viscoelastic model with internal variables

The present work is aimed at estimating the constitutive parameters of viscoelastic materials. The constitutive equation addressed takes internal dissipation into account by means of internal variables. The identification method is built on an optimization problem where the minimum of an error function is sought. The error function is based on the difference between the experimental response and the model one and on the parameter constraints as well. The constitutive parameters are estimated by means of a modified Levenberg–Marquardt algorithm. The viscoelastic material characterization was assessed through an experimental set-up consisted of a sandwich beam with a viscoelastic core.     

电厂热工智能控制系统的研究

火电厂的主汽温是大惯性、大滞后的对象,并且动态特性随机组符合变化而变化,运行过程中扰动多.采用模型参考自适应控制的思想,将模糊控制方法和内模控制方法结合在一起,提出了一种模型参考模糊自适应内模控制方法.此方法综合了模糊控制,内模控制和自适应控制的优点,增强了系统的鲁棒性,针对电厂热工过程系统的仿真研究结果证明了此方法的有效性.     

Investigation on thermal characteristics of heat sinks for power module using STM

The device that controls dynamic motions in a washing machine is called as MICOM. This device includes an IPM that controls the rotation of a tub. Also, the overheating of IPM gives cause for lowering the service life of an applied chip and is directly linked with its faults. A heat sink that is larger than the volume of the applied chip more than 50 times is installed to prevent such overheating. In the operation of the IPM, the temperature specification of the heat sink can be determined as 80°C under the air temperature of 25°C. However, the heat sink used at the present time cannot satisfy this condition, so it is necessary to redesign such a heat sink to satisfy this condition. This study proposes an STM that is able to precisely calculate the temperature applied to IPM in a system level prior to redesigning the heat sink. The STM can be considered as a model that complements a JEDEC analysis model. This model implements a parameter analysis to perform the optimization of a heat sink and verifies the priority of parameters to reduce material costs. Furthermore, it investigates a counterproposal that replaces the conventional cooling methods in which it seeks a counterproposal that performs heat dissipation in a device according to the SoC of chips and is able to suppress EMI. This paper was recommended for publication in revised form by Associate Editor Jae Dong Chung Chung-Hyo Jung acquired the doctoral degree in the Dept. of Science for Open and Enviromental Systems at Keio University in 2003. The specialty in the doctoral course was GSMAC-FEM and studied on MHD (magnetohydrodynamics). Dr. Jung joined Samsung Electronics Co., Ltd. as a CFD engineer in 2003. Also, he has worked at Samsung Advanced Institute of Technology and has charged in the thermal analysis of semi-conductors (system LSI). One of the Dr. Jung’s major concerning fields is the mechanical application of Lie-Groups.     

Influence of steam injection and hot gas bypass on the performance and operation of a combined heat and power system using a recuperative cycle gas turbine

The influence of steam injection and hot gas bypass on the performance and operation of a combined heat and power (CHP) system using a recuperative cycle gas turbine was investigated. A full off-design analysis was used to investigate not only the change in performance but also the variation in engine operation caused by steam injection. The performance improvement capability and operating limitations of full steam injection was examined. Selected operations (partial steam injection and underfiring) that secure minimum compressor surge margin were comparatively analyzed. Partial steam injection was found to be a better option than underfiring in all thermodynamic aspects. Under ISO condition, power and efficiency improvements in the partial injection targeted at a 10% surge margin are 27% and 7.4%, respectively. This study also investigated the increase in steam generation brought by the bypass of turbine exhaust gas around the recuperator. This bypass provided high operational flexibility by varying the capacity of thermal energy supply in both the pure CHP operation and the steam-injected operation. In particular, in the steam-injected operation, the capacity of thermal energy supply can be largely increased by the said bypass, while producing a greater power output than the pure CHP system.     

Distributed and decentralized state estimation in gas networks as distributed parameter systems

In this paper, a framework for distributed and decentralized state estimation in high-pressure and long-distance gas transmission networks (GTNs) is proposed. The non-isothermal model of the plant including mass, momentum and energy balance equations are used to simulate the dynamic behavior. Due to several disadvantages of implementing a centralized Kalman filter for large-scale systems, the continuous/discrete form of extended Kalman filter for distributed and decentralized estimation (DDE) has been extended for these systems. Accordingly, the global model is decomposed into several subsystems, called local models. Some heuristic rules are suggested for system decomposition in gas pipeline networks. In the construction of local models, due to the existence of common states and interconnections among the subsystems, the assimilation and prediction steps of the Kalman filter are modified to take the overlapping and external states into account. However, dynamic Riccati equation for each subsystem is constructed based on the local model, which introduces a maximum error of 5% in the estimated standard deviation of the states in the benchmarks studied in this paper. The performance of the proposed methodology has been shown based on the comparison of its accuracy and computational demands against their counterparts in centralized Kalman filter for two viable benchmarks. In a real life network, it is shown that while the accuracy is not significantly decreased, the real-time factor of the state estimation is increased by a factor of 10.     

Effect of thermal radiation on convection heat transfer in cooling channel of photovoltaic thermal system

The effect of thermal radiation on convection heat transfer in flat-box type cooling channel of photovoltaic thermal system with tilt angle of 30 degree was studied by 3D numerical simulation under constant heat flux boundary condition. The temperature contours and velocity fields of fluid near the outlet were obtained. The variations of wall temperature and convection Nusselt number along flow direction for all the separate walls composing the cooling channel were compared and analyzed. The results show that due to thermal radiation, the deflection of the maximum velocity region to heated top wall, together with the asymmetry of temperature field is weakened. For natural convection, radiation promotes the formation of multi-vortices. For mixed convection, heat transfer on all the cooling channel walls is enhanced under the condition of lower heat flux while heat transfer on heated top wall is deteriorated when the heat flux is relative high. Also, pressure re-rising is promoted by thermal radiation.     

多波段共口径红外系统光机热一体化设计

针对红外系统对热辐射比较敏感的特点,即除了来自系统外部的杂散热辐射会影响系统的性能,系统内部的热辐射也会降低系统的灵敏度,在研制某型号红外系统中,根据技术指标对其光学系统、机械结构以及热辐射抑制进行了详细论述和设计.系统口径1000mm,采用可见光、中波红外、长波红外3个光谱波段共用口径的光学结构,可见光波段焦距2000 mm,目视鉴别率690 lp/mm,中波红外波段焦距为2000 mm,长波红外波段焦距为2000 mm.采用地平式二维转动机构以实现对成像头部组件俯仰、方位的调整,保证对目标的瞄准和跟踪.重点对系统内部杂散辐射进行了分析,包括机械内壁不同表面不同发射率对像面接收辐射能的影响,以及光机内壁不同温度不同发射率对像面接收辐射能的影响.设计了水冷循环系统制冷光机系统的温度,降低系统内部杂散辐射.测试结果表明,可见光波段焦距及目视鉴别率达到了预先设计的要求值,各红外分系统的焦距也分别到达了预先设计的要求值,所摄取的图像对比度清晰.     

基于无线SCADA的电网参数采集系统设计应用

设计完成基于SCADA的电网参数采集系统,实现基于无线系统的远程通讯.通过罗克韦尔自动化PowerMoniter3000对电网参数进行采集,应用SQLserver2000对数据存储,实现以太网远程实时监控,扩展了系统功能,优化了系统结构.     

A spectral estimation method for nonstationary signals analysis with application to power systems

In this paper we analyze a new method for estimating the spectral content of frequency and amplitude modulated waveforms in the context of power line signals where, as well known, the frequency of the fundamental component (50 Hz or 60 Hz) slightly changes over time. The method, proposed here in two distinct implementations, is based on a different choice of the harmonic functions that are usually used in the DFT as a basis to analyze signals. Indeed their frequency is allowed to change over time, according to the output of an instantaneous frequency detector. The orthogonality of the basis is preserved by performing a change of reference in the time. The theory is developed in continuous time and subsequently implemented in discrete time. Simulations and experimental results are provided in order to verify and characterize preliminarily the proposed method.     

Event triggered state estimation techniques for power systems with integrated variable energy resources

For many decades, state estimation (SE) has been a critical technology for energy management systems utilized by power system operators. Over time, it has become a mature technology that provides an accurate representation of system state under fairly stable and well understood system operation. The integration of variable energy resources (VERs) such as wind and solar generation, however, introduces new fast frequency dynamics and uncertainties into the system. Furthermore, such renewable energy is often integrated into the distribution system thus requiring real-time monitoring all the way to the periphery of the power grid topology and not just the (central) transmission system. The conventional solution is two fold: solve the SE problem (1) at a faster rate in accordance with the newly added VER dynamics and (2) for the entire power grid topology including the transmission and distribution systems. Such an approach results in exponentially growing problem sets which need to be solver at faster rates. This work seeks to address these two simultaneous requirements and builds upon two recent SE methods which incorporate event-triggering such that the state estimator is only called in the case of considerable novelty in the evolution of the system state. The first method incorporates only event-triggering while the second adds the concept of tracking. Both SE methods are demonstrated on the standard IEEE 14-bus system and the results are observed for a specific bus for two difference scenarios: (1) a spike in the wind power injection and (2) ramp events with higher variability. Relative to traditional state estimation, the numerical case studies showed that the proposed methods can result in computational time reductions of 90%. These results were supported by a theoretical discussion of the computational complexity of three SE techniques. The work concludes that the proposed SE techniques demonstrate practical improvements to the computational complexity of classical state estimation. In such a way, state estimation can continue to support the necessary control actions to mitigate the imbalances resulting from the uncertainties in renewables.