Diesel engine air path control based on neural approximation of nonlinear MPC

This paper deals with a control design problem for a diesel engine air path system that has strong nonlinearity and requires multi-input and multi-output control to satisfy requirements and constraints. We focus on a neural network based approximation of nonlinear model predictive control (NMPC) for high-speed computation. Most neural approximation methods are verified only through simulation; further, the influence of approximation on the closed-loop performance has been not sufficiently discussed. In this study, we discuss this influence, and propose a new method to improve stability against degradation due to an approximation error. The control system is assembled using a neural network based controller, obtained by the proposed method, and an unscented Kalman filter. This system is verified both numerically and experimentally; the results demonstrate the capability of the proposed method to track the boost pressure, EGR rate, and pumping loss according to the reference values, and satisfy the constraints of compressor surge and choke. The high computation speed that can be achieved using a standard on-board ECU is also demonstrated using the approximated controller.     

发动机冷却系统的建模与仿真

该文在基于MATLAB/SIMULINK的环境中建立了某重型汽车柴油发动机冷却系统模型。该系统主要由发动机、节温器、散热器、水泵以及空气冷却系统组成。模型着重考虑了节温器的迟滞和热惯性等非线性特点，并建立了风扇的风速控制逻辑。在不同运行状况下仿真结果与相应的发动机实测数据基本一致，表明所建立的模型具有较好的温度预测能力。     

内燃机中吸气和压缩过程的二维模拟

进行了发动机中空气吸气和压缩过程的二维计算机模拟．使用二维正交曲线坐标系以考虑燃烧室的复杂形状．采用SIMPLEC算法求解流体力学模型方程．论文中分别采用4个湍流模型：标准的k-ε模型,Realizable k-ε模型,雷诺应力模型和亚网格尺度模型．论文中对模拟计算的预测值进行了分析．计算出的流场与实验测定值进行了对比．通过模拟计算得到了内燃机中重要的流动图象．     

Time and frequency domain identification and analysis of a gas turbine engine

The nonlinear autoregressive moving average model with eXogenous inputs (NARMAX) approach is used to analyse the dynamics of a gas turbine engine. The fuel flow-shaft speed relationship is analysed by identifying both time and frequency domain models of the system. The frequency domain analysis is studied by mapping the discrete-time NARMAX models into the generalised frequency response functions (GFRFs) to reveal the nonlinear coupling between the various input spectral components and the energy transfer mechanisms in the system. A continuous-time nonlinear differential equation model is also estimated using the GFRFs.     

LAMOST焦面板数学建模与仿真

焦面板是大天区面积多目标光纤光谱天文望远镜的一个重要部件,它是一个球面孔群结构,孔的位置精度直接影响到系统的成像质量.建立焦面板孔群中心点位置的数学模型并进行仿真不仅是进行优化孔群分布的需要,也是进行后续数控加工的需要.空间球坐标投影算法,解决了在球面上近似均匀分布孔群的难题,并利用科学计算工具MATLAB进行了数学建模与仿真.最后给出了仿真结果和孔群中心点位置的三维坐标,并提出了其他的改进方案.结果表明,该算法能有效地提高焦面板的孔位精度,满足了LAMOST的需要.     

弹库系统弹列运动建模与仿真

弹库系统是向舰炮发射系统补弹、供弹的复杂机电系统。该文以某型弹库系统为例，介绍了弹库系统的组成与功能，弹库系统的建模目标与内容，研究了弹库操控逻辑，弹列运动的基本规律，采用离散系统的分析方法，从弹列的状态描述变量、事件的描述函数和动作的功能函数三个方面，建立了弹列运动的模型，编制了仿真程序，实现了弹库操控与弹列运动基本算法。该仿真系统可用于弹库系统总体设计、弹列运动调度算法研究。     

Generic model identification framework for thermodynamic engines for use in hybrid power stations control and simulation

Thermodynamic engines are focusing increasing attention in the context of solar-based electric power generation. Knowledge-based models of such engines are sometimes difficult to derive and when they are available, their simulation may be numerically a rather heavy task given the control updating period that may be needed. In the present work a generic nonlinear identification framework that enables the dynamics of the key quantities of a thermodynamic engine to be captured is proposed. Such a fast model can then be used in the simulation and the control design stage of the whole electric power generation station. The proposed identification framework is validated on a recently developed knowledge-based model of a beta-type Stirling engine with rhomic-drive mechanism.     

Modelling and simulation of a copper electrolysis cell group

The energy consumption of the copper electrolysis process is relatively high. Electrical disturbances – like contact failures and short circuits – even increase the energy consumption and also reduce the quality of copper produced. To better understand and improve the process, a computationally feasible and reliable model of copper electrolysis cell group is of great importance. In this paper a multiphysical FEM model of copper electrolysis cell group is presented. A number of simplifications are proposed to make the model computationally feasible.     

Predictive control of a real-world Diesel engine using an extended online active set strategy

In order to meet tight emission limits Diesel engines are nowadays equipped with additional hardware components like an exhaust gas recirculation valve and a variable geometry turbocharger. Conventional engine control units use two SISO control loops to regulate the exhaust gas recirculation valve and the variable geometry turbocharger, although their effects are highly coupled. Moreover, these actuators are subject to physical constraints which seems to make an advanced control approach like model predictive control (MPC) the method of choice. In order to deal with MPC sampling times in the order of milliseconds, we employed an extension of the recently developed online active set strategy for controlling a real-world Diesel engine in a closed-loop manner. The results show that predictive engine control based on online optimisation can be accomplished in real-time – even on cheap controller hardware – and leads to increased controller performance.     

Numerical simulation of a plate-gap biosensor with an outer porous membrane

A plate-gap model of a porous enzyme doped electrode covered by a porous membrane has been proposed and analyzed. The two-dimensional-in-space mathematical model of the plate-gap biosensor is based on the reaction–diffusion equations containing a nonlinear term related to Michaelis–Menten kinetics of the enzymatic reaction. The model involves four regions: the enzyme-filled gaps where the enzymatic reaction as well as the mass transport by diffusion take place, the porous membrane, a diffusion limiting region where only the mass transport by diffusion takes place, and a convective region where the analyte concentration is maintained constant. Using numerical simulation, the effect of the biosensor geometry on the biosensor response was investigated. The simulation was carried out using the finite difference technique. The mathematical model as well as numerical solution were validated using analytical solutions existing for specific cases of the model parameters.     

Modeling and control of an airbrake electro‐hydraulic smart actuator

In this paper, an accurate model of an airbrake electro‐hydraulic smart actuator is obtained by physical considerations, and then different control strategies (variable‐gain proportional control, PT₁ control with switching integrator, and second order sub‐optimal sliding mode control) are proposed and analyzed. This application is innovative in the avionic field, and is one of the first attempts to realize a fly‐by‐wire system for airbrakes, oriented to its immediate employment and installation on current aircraft. The project was carried on with the participation of the Italian Ministry of Defense, and was commissioned to MAG, a leading provider of integrated systems and aviation services for aerospace. Copyright © 2011 John Wiley and Sons Asia Pte Ltd and Chinese Automatic Control Society     

发动机装配仿真教学软件的设计与实现

为帮助学生经济、有效地学习发动机装配知识和技能,基于Solidwlorks和Authorware开发出一套发动机装配的教学仿真软件,实现对发动机装配教学的计算机仿真。对软件的设计思想、结构、流程和界面设计进行阐述,并介绍开发软件所用的主要技术。     

IGM弧焊机器人工作站三维造型与仿真

分析了IGM弧焊机器人工作站的结构特点,在VC++开发环境下,使用OpenGL图形开发工具,建立了基本体素;采用面向对象的思想完成了工作站各个组成部分的三维实体造型,系统中分别建立了环境类、机架类、机器人类、变位机类及其派生类,并实现了该工作站基于微机的运动仿真。     

Modeling and identification of a PEM fuel cell humidification system

A theoretical model of a humidifier of proton exchange membrane （PEM） fuel cell systems is developed and analyzed first in this paper. The model shows that there exists a strong nonlinearity in the system. Then, the system is identified using a wavelet networks method. To avoid the curse-of-dimensionality problem, a class of wavelet networks proposed by Billings is employed. The experimental data acquired from the test bench are used for identification. The one-step-ahead predictions and the five-step-ahead predictions are compared with the real measurements, respectively. It shows that the identified model can effectively describe the real system.     

The development of a model and simulation of an aviation maintenance technician task performance

This paper describes the model of an aircraft maintenance technician (AMT) behaviour working in a real world environment and the application of this model in a computer simulation. The model was derived from the combination of two existing models of cognition (SHELL and RMC/PIPE), based on the paradigm of an information processing system. The simulation structure was developed by transforming the model into an action-execution structure and implementing this model in a computer program based on an object-oriented programming language. An error generation system was coupled to a simple taxonomy of causal correlations between socio-technical and contextual factors operating in an environment defined by a comprehensive task analysis. The simulator can be applied to many aviation maintenance tasks to assist in the design of aviation maintenance training systems through the analysis of the interaction of performance influencing factors and possible AMT performances during the execution of normal maintenance operations. A number of sample outputs from the simulator show the potential of the results to assist in training development. A discussion is also made of other potential applications and the future directions the simulator structure can take.     

Neural modelling and control of a Diesel engine with pollution constraints

The paper describes a neural approach for modelling and control of a turbocharged Diesel engine. A neural model, whose structure is mainly based on some physical equations describing the engine behaviour, is built for the rotation speed and the exhaust gas opacity. The model is composed of three interconnected neural submodels, each of them constituting a nonlinear multi-input single-output error model. The structural identification and the parameter estimation from data gathered on a real engine are described. The neural direct model is then used to determine a neural controller of the engine, in a specialized training scheme minimising a multivariable criterion. Simulations show the effect of the pollution constraint weighting on a trajectory tracking of the engine speed. Neural networks, which are flexible and parsimonious nonlinear black-box models, with universal approximation capabilities, can accurately describe or control complex nonlinear systems, with little a priori theoretical knowledge. The presented work extends optimal neuro-control to the multivariable case and shows the flexibility of neural optimisers. Considering the preliminary results, it appears that neural networks can be used as embedded models for engine control, to satisfy the more and more restricting pollutant emission legislation. Particularly, they are able to model nonlinear dynamics and outperform during transients the control schemes based on static mappings.     

Modelling and simulation of a fore-and-aft driver''s seat suspension system with road excitation

This paper describes a simplified simulation of two configurations of the fore-and-aft seat suspension system. A fore-and-aft suspension system model was proposed based on the laboratory measurements of the seat vibration isolation performance. Friction was identified as an important parameter, so different approaches to simulating the suspension friction were investigated. Predicted seat vibration mitigation properties were compared with those measured in the laboratory in response to the recordings of the fore-and-aft vibration measured at the base of the driver's seat in an on-road tractor–trailer combination (articulated truck). Optimisation of the suspension elements parameters was then performed to identify the maximum attainable attenuation. A solution incorporating supercritical suspension damping predicted to give an improvement of the order of 10% in the x-direction mitigation properties as compared to a fixed (locked) horizontal suspension system.

Relevance to the industry

Simulations conducted in this study are of use to seat manufacturers in developing the fore-and-aft seat suspension systems with improved vibration mitigation properties and for predicting its dynamic performance. The optimisation study shows the attainable vibration mitigation limits for a horizontal suspension system.     

Modelling and simulation of Rayleigh fading,path loss,and shadowing fading for wireless mobile networks

In this paper, we first derive two explicit mathematical expressions of bit error rates (BERs) with Rayleigh fading for differential phase shift keying (DPSK) and quadrature amplitude modulation (QAM), and establish corresponding simulation models to realize the effect of Rayleigh fading. Next, we propose a mathematical expression to define the effect of shadowing fading and an approach to computing it. Then, we optimize the effect of path loss through adapting the value of the path loss exponent to different environments. Finally, using a packet-oriented simulation tool, OPtimized Network Engineering Tool (OPNET), we realize the effects of Rayleigh fading and shadowing fading, optimize the effect of path loss, and investigate the integrated impact of these effects on the performance of wireless mobile networks including wireless local area networks (WLANs) and mobile ad hoc networks (MANETs). Simulation results not only coincide with the experimental results in present literature, but also show that these effects exert a non-negligible impact on the performance of wireless mobile networks. Accordingly, our new models and approaches make the present over-optimistic simulation results more accurate and reasonable.     

Specification,analysis and simulation of the dynamics within an organisation

In this paper a modelling approach to the dynamics within a multi-agent organisation is presented. A declarative, executable specification language for dynamics within an organisation is proposed as a basis for simulation. Moreover, to be able to specify and analyse dynamic properties within an organisation, another declarative specification language is put forward, which is much more expressive than the executable language for simulations. Supporting tools have been implemented that consist of a software environment for simulation of organisation models and a software environment for analysis of dynamic properties against traces of dynamics within an organisation.