Considerations on nonlinear model predictive control techniques

The nonlinear model predictive control (NMPC) is an on-line application based on nonlinear convolution models. It is an appealing control methodology, but it is difficult to implement and its solution is not so performing since it unavoidably means to solve a usually large-scale, constrained, and multidimensional optimization. To increase the difficulty, this optimization problem is subject to computationally heavy differential and algebraic constraints constituting the same convolution model and the least squares nature of the objective function easily leads to narrow valleys and multimodality issues.Beyond a short review of the state-of-the-art, the paper is aimed at highlighting the possibility to exploit at best the intrinsic features of the specific system one is going to control using the NMPC. The idea is to give the NMPC the possibility to automatically select the best combination of algorithms (differential solvers and optimizers) in accordance with the specific problem to be solved. From this perspective, the NMPC could be easily extended to many scientific fields traditionally far from process systems and computer-aided process engineering and the user has not to worry about which specific differential solvers and optimizers are needed to solve his/her problem.     

塑料管道国际标准新进展

介绍了国际标准化组织ISO/TC138"流体输送用塑料管材、管件及阀门技术委员会"2010年年会情况及相关国际标准工作新进展, 旨在为我国塑料管道标准制修订及行业发展提供参考, 使中国实质性参与到塑料管材的国际标准化工作中。     

Impact of biodiesel bulk modulus on injection pressure and injection timing. The effect of residual pressure

As the demand for energy rises fossil fuel reserves are depleted daily, increasing the interest in alternative fuels. Biodiesel is one of the best candidates in this class and its use is expected to expand rapidly throughout the world. Numerous researchers have been investigating how biodiesel affects combustion, pollutant formation and exhaust aftertreatment. There is general agreement that its combustion characteristics are similar to those of standard diesel fuel, except for a shorter ignition delay, a higher ignition temperature, and greater ignition pressure and peak heat release. Engine power output is similar with both fuels. As regards emissions, reductions in particulate matter (PM) and carbon monoxide (CO) and increases in nitrogen oxides (NOx) are described with most biodiesel blends. The latter is referred to as the ‘biodiesel NOx effect’. The vast majority of researchers who explored the effect of biodiesel did so in mechanical injection engines. They found that the primary mechanism by which biodiesel increases NOx emissions is by an inadvertent advance in the start of injection timing, caused by a higher modulus and viscosity. However, more recent studies show that NOx emissions also increase in biodiesel-fuelled common rail engines, and that in some cases they actually decrease in engines with mechanically controlled fuel injection systems. This cannot be explained solely by differences in compressibility and remains an open question. The present study provides a contribution to the discussion in this field by describing a new method to evaluate the injection advance in engines with mechanically controlled pumps. The experimental data show that the advances in the start of injection timing, using biodiesel rather than mineral diesel, are smaller than those calculated with standard methods and may even not occur at all, depending on injection system design. In addition, they demonstrate that, contrary to common belief, injection pressure does not always increase when using biodiesel. These data may help explain why some researchers have found similar or even reduced NOx emission also with mechanical injection systems.     

Dynamics and control of aggregate thin film surface morphology for improved light trapping: Implementation on a large-lattice kinetic Monte Carlo model

This work demonstrates the use of feedback control, coupled with a suitable actuator design, in manufacturing thin films whose surface morphology is characterized by a desired visible light reflectance/transmittance level. The problem is particularly important in the context of thin film manufacturing for thin film solar cells where it is desirable to produce thin films with precisely tailored light trapping characteristics. Initially, a thin film deposition process involving atom adsorption and surface migration is considered and is modeled using a large-lattice (lattice size=40,000) kinetic Monte Carlo simulation. Subsequently, thin film surface morphology characteristics like roughness and slope are computed with respect to different characteristic length scales ranging from atomic to the ones corresponding to visible light wavelength and it is found that a patterned actuator design is needed to induce thin film surface roughness and slope at visible light wavelength spatial scales, which lead to desired thin film reflectance and transmittance levels. Then, an Edwards–Wilkinson-type equation (a second-order stochastic partial differential equation) is used to model the surface evolution at the visible light wavelength spatial scale and form the basis for the design of a feedback controller whose objective is to manipulate the deposition rate across the spatial domain of the process. The model parameters of the Edwards–Wilkinson equation are estimated from kinetic Monte Carlo simulations and their dependence on the deposition rate is used in the formulation of the predictive controller to predict the influence of the control action on the surface roughness and slope throughout the thin film growth process. Analytical solutions of the expected surface roughness and surface slope at the visible light wavelength spatial scale are obtained by solving the Edwards–Wilkinson equation and are used in the control action calculation. The cost function of the controller involves penalties on both surface roughness and slope from set-point values as well as constraints on the magnitude and rate of change of the control action. The controller is applied to the large-lattice kinetic Monte Carlo simulation. Simulation results demonstrate that the proposed controller and patterned actuator design successfully regulate aggregate surface roughness and slope to set-point values at the end of the deposition that yield desired levels of thin film reflectance and transmittance.     

基于预测电流控制的有源功率滤波器的研究

通过分析APF的数学模型和预测电流理论,推导出了预测电流控制在有源滤波器中的应用.利用预测电流控制的数学推导过程,对反馈调节和最优化处理做了分析,并对控制参数与系统性能之间的关系进行了讨论.     

Applying Model Predictive Control to Dividing Wall Columns

The technology of dividing wall columns can offer enormous energy savings compared to common distillation columns and configurations. The technology of model predictive control is also advantageous since such a controller minimizes the future deviation of the predicted controlled variable from the reference point. The practical application of model predictive controllers for dividing wall columns is still limited due to limited experience with high interactions among the process variables. The scope of this work is the development and analysis of a method for the design of model predictive controllers for dividing wall columns. An experimental investigation verifies the practicability of the applied approach. The methods generated are transferable to other applications. Thus, the industrial acceptance of model predictive controllers for dividing wall columns is enhanced.     

Study on the closed-loop properties of GPC

Based on the coefficient mapping of eigenpolynomial from plant to GPC closed-loop system in the IMC structure, the solvability of the optimal control law of GPC and some properties of GPC in relationship with tun ing parameters are discussed Theorems on GPC resulting in deadbeat control are given by properly choosing the design parameters. Furthermore, new result about reducing GPC closed-loop system is derived, which extends the former conclusions. It also provides a new way to study the properties of GPC system based on coefficient mapping     

G.718音频编码器核心层的一种低延时编码方案

语音编码器不仅要求提供高质量的语音,同时还要具有较低的编解码延时。较大的编码延时不仅会降低语音通信的服务质量,同时还可能减小系统容量。由于G.718编码器的延时主要由核心层算法引入,为了降低G.718编码器核心层的延时,提出了一种帧长为5ms的低延时编码方案,通过改变语音分类、开环基因搜索、线性预测系数的求解和量化方法,成功将编码延时在G.718基础上降低了25ms。主客观语音评测结果表明,该方案接近G.718核心层的重建语音质量。     

一种RVM的INS参数长期稳定性预测与补偿方法

为提高惯导系统参数长期稳定性,降低人工标定成本,增强惯导系统使用效能,提出一种基于相关向量机的惯导系统参数长期稳定性预测和补偿方法,选择均值和标准差作为参数稳定性的性能指标.而对于均值随时间变化具有明显规律的参数,采用RVM方法对存贮时间较长的参数稳定性均值进行回归建模,根据模型对存贮时间较短的参数稳定性进行性能预测和标定参数补偿．最后对惯导系统中重要参数加速度计标度因数长期稳定性进行建模预测和参数补偿,补偿后结果显示,间隔时间约6个月的参数稳定性均值性能提高了50.90％,验证了所提方法具有很好的实际应用价值,且表明使用该方法能够代替人工标定,以增强惯导系统使用效能．     

Thermal efficiency characteristics of hydrogen internal combustion engine

To study the economic advantages of hydrogen internal combustion engine,an experimental study was carried out using a 2.0Lport fuel-injected(PFI)hydrogen internal combustion engine.Influences of fuel-air equivalence ratioΦ,speed,and ignition advance angle on heat efficiency were determined.Test results showed that indicated thermal efficiency(ITE)firstly increased with fuel-air equivalence ratio,achieved the maximum value of 40.4%(Φ=0.3),and then decreased whenΦ was more than 0.3.ITE increased as speed rises.Mechanical efficiency increased as fuel-air equivalence ratio increased,whereas mechanical efficiency decreased as speed increased,with maximum mechanical efficiency reaching 90%.Brake thermal efficiency(BTE)was influenced by ITE and mechanical efficiency,at the maximum value of 35%(Φ=0.5,2 000r/min).The optimal ignition advance angle of each condition resulting in the maximum BTE was also studied.With increasing fuel-air equivalence ratio,the optimal ignition angle became closer to the top dead center(TDC).The test results and the conclusions exhibited a guiding role on hydrogen internal combustion engine optimization.