Computer-aided physical multi-domain modelling: Some experiences from education and industrial applications

For the purposes of this paper, computer-aided physical modelling means a type of modelling in which a computer-aided approach is used, with the basic aim being to maintain the physical structure of a real system or its topology as much as possible in the model. Bond graphs represent a very efficient and traditional approach. However, new, object-oriented and multi-domain tools based on the Modelica language are more appropriate for industrial staff or for the people who do not have a deep insight into modelling and simulation. In this paper we describe several educational and industrial application projects in the Dymola–Modelica environment: a process-systems library, two mechanical systems (an inverted pendulum and a laboratory helicopter), a model of thermal and radiation flows in buildings and two models of processes in mineral-wool production, i.e., a pendulum system and a recuperator system. We describe some experiences from these projects, but also from a more general use of the Matlab–Simulink and Dymola–Modelica environments over many years. One simple conclusion is that we need to educate with two approaches: a more physical and advanced acausal Modelica-like approach, but also a more traditional causal or block-oriented approach according to the historical CSSL standard. The important advantages and disadvantages of both approaches are described. The Modelica-based approach enables true ‘physical’ modelling with fully reusable components. However, there is a particular danger, i.e., users occasionally forget some basic modelling principles when using sophisticated libraries. The result is a very complex modelling structure that is relatively inefficient for the simulation and sometimes has many numerical problems. It is usually very difficult to detect the real reasons for that.     

Computational modular model library of gas turbine

Designing and developing new aircraft engine is time-consuming and expensive. Computational simulation is a promising means for alleviating this cost, but constructing flexible simulation software capable of evaluation of integrated aircraft engine system architectures is hard work. This paper addresses the design of a tool—a generic modular-modeled library of air gas turbine, this library is based on object-oriented technology and hierarchical decomposition and provides a flexible component-based representation for defining, modifying, and simulating the aircraft gas turbine system, subsystem and components. It enables users to customize and extend the framework to add new functionality or adapt the simulation behavior as required, and it allows new models to be composed programmatically or graphically to form more complex models. The model library can be used in steady-state and transient analysis of the aero-engine. It is also a user-friendly, accurate, fast PCbased and easily reusable simulating tool. The advanced object-oriented simulation language Modelica is used to construct this library. Modelica provides a powerful tool to design the library. All of the work described in this paper is developed based upon Dymola/Modelica.     

基于Modelica的多领域建模与联合仿真

为实现多领域建模仿真环境与其他仿真环境的联合仿真,提出基于Modelica多领域建模的联合仿真方案.该方案基于Modelica多领域模型的连接机制,通过Modelica模型与Simulink模块的转换机理,实现在S-Function联合仿真框架下的联合仿真.基于Modelica的多领域物理系统建模仿真工具MWorks与...     

Integrated relative position and attitude control of spacecraft in proximity operation missions

This paper addresses an integrated relative position and attitude control strategy for a pursuer spacecraft flying to a space target in proximity operation missions. Relative translation and rotation dynamics are both presented, and further integratedly considered due to mutual couplings, which results in a six degrees-of-freedom (6-DOF) control system. In order to simultaneously achieve relative position and attitude requirements, an adaptive backstepping control law is designed, where a command filter is introduced to overcome "explosion of terms". Within the Lyapunov framework, the proposed controller is proved to ensure the ultimate boundedness of relative position and attitude signals, in the presence of external disturbances and unknown system parameters. Numerical simulation demonstrates the effect of the designed control law.     

Constraint based approach for the steady-state simulation of complex systems: Application to ship control

When the steady states are largely predominant with respect to transitional phases, steady-state simulation seems sufficient to predict the behavior of a complex system. Over the past 20 years, different modeling languages and dedicated tools have been developed to improve steady state simulation.In this paper, focus is made on steady-state simulation for system control and design. A model combining an emission sub-model with a ship propulsion sub-model was implemented in a constraint programming (CP) approach. It will help to determine the efficiency (i.e. the ability to model and solve the problem) and complexity of implementation (i.e. difficulties encountered during the implementation) of this approach.First, requirements for the steady-state simulation of complex systems are defined. Then, CP approach is shown to be able to answer these issues through experiments. This approach is then compared to one of the main simulation languages: Modelica.Although the two approaches (i.e Modelica and CP) are able to reverse models, the study shows that the use of Modelica principles for steady-state simulation involves some crippling limitations, such as the non-management of under/over-constrained systems, or inequalities.This study also shows that the constraint programming approach permits to meet some needs for steady-state simulation not yet covered by current approaches.     

基于VC+ +的航天器姿态控制系统设计与仿真

针对采用结构化方法设计航天器仿真软件效率低的问题,基于VC 采用面向对象思想提出了一种航天器姿态动力学与控制的仿真框架。设计了一种航天器的姿态控制器,并给出了系统稳定性证明;在理论上证明了控制律的全局渐近稳定后,在所设计出的VC 仿真软件上验证了控制算法。所提出的航天器仿真软件设计方法成功应用于某型航天器姿态控制系统,实现了仿真软件的可重用性,提高了软件的可扩充性,优化了代码,取得了明显的效果。     

Implementation of a Modelica compiler using JastAdd attribute grammars

We have implemented a compiler for key parts of Modelica, an object-oriented language supporting equation-based modeling and simulation of complex physical systems. The compiler is extensible, to support experiments with emerging tools for physical models. To achieve extensibility, the implementation is done declaratively in JastAdd, a metacompilation system supporting modern attribute grammar mechanisms such as reference attributes and nonterminal attributes.This paper reports on experiences from this implementation. For name and type analyses, we illustrate how declarative design strategies, originally developed for a Java compiler, could be reused to support Modelica’s advanced features of multiple inheritance and structural subtyping. Furthermore, we present new general design strategies for declarative generation of target ASTs from source ASTs. We illustrate how these strategies are used to resolve a generics-like feature of Modelica called modifications, and to support flattening, a fundamental part of Modelica compilation. To validate that the approach is practical, we have compared the execution speed of our compiler to two existing Modelica compilers.     

支持网络建模和仿真的Modelica模型管理框架

针对基于Modelica的多领域仿真模型组织方式不能支持模型的网络化共享控制及网络环境下在线建模仿真的问题,提出一种支持网络环境下建模与仿真的Modelica模型管理框架。首先分析了现有Modelica模型组织方式在支持网络多用户模式下的模型共享及建模仿真方面的问题,然后提出了基于数据库与文件仓相结合解决方案,既支持Modelica知识模型的网络共享,又支持网络环境在线建模与仿真。最后基于该模型管理框架开发实现基于网络的多领域统一建模仿真平台。     

基于Lyapunov稳定性及CPSO的航天器姿轨控制

针对在轨服务航天任务中轨道与姿态动力学耦合问题,提出一种基于Lyapunov稳定性分析的反馈控制方法,采用基于对偶四元数的一体化耦合动力学模型来描述航天器的相对位置和相对姿态,利用速度陀螺仪与激光雷达的量测信息构建Lyapunov能量函数,得到满足系统全局渐进稳定的控制率。并用混沌粒子群算法（Chaos Particle Swarm Optimization algorithm,CPSO）优化控制器参数以便达到良好的控制效果。仿真结果表明,该方法不仅保证了航天器的相对轨道、相对姿态和跟踪速度在较短的时间内收敛至期望值,而且具有较高的跟踪精度。     

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.     

Robust fuzzy 3D path following for autonomous underwater vehicle subject to uncertainties

This paper addresses a three-dimensional (3D) path following control problem for underactuated autonomous underwater vehicle (AUV) subject to both internal and external uncertainties. A two-layered framework synthesizing the 3D guidance law and heuristic fuzzy control is proposed to achieve robust adaptive following along a predefined path. In the first layer, a 3D guidance controller for underactuated AUV is presented to guarantee the stability of path following in the kinematics stage. In the second layer, a heuristic adaptive fuzzy algorithm based on the guidance command and feedback linearization Proportional-Integral-Derivative (PID) controller is developed in the dynamics stage to account for the nonlinear dynamics and system uncertainties, including inaccuracy modelling parameters and time-varying environmental disturbances. Furthermore, the sensitivity analysis of the heuristic fuzzy controller is presented. Against most existing methods for 3D path following, the proposed robust fuzzy control scheme reduces the design and implementation costs of complicated dynamics controller, and relaxes the knowledge of the accuracy dynamics modelling and environmental disturbances. Finally, numerical simulation results validate the effectiveness of the proposed control framework and illustrate the outperformance of the proposed controller as well.     

基于Modelica的半物理仿真硬件接口控制技术

针对半物理仿真（Hardware in Loop Simulation,HILS）中Modelica模型无法直接控制硬件设备的问题,基于Modelica研究硬件板卡接口控制模块与多领域仿真模型的统一表达技术.分析可视化模型方程表达机理,建立硬件板卡的接口模型库,从而在同一建模环境中实现多领域物理模型与硬件设备的关联,并实现Modelica离线数字仿真模型至HILS模型的直接转换,为基于Modelica的HILS应用提供技术支持.电机转速控制HILS结果表明该方法可行.     

Evaluation and comparison of models and modelling tools simulating nitrogen processes in treatment wetlands

In this paper, two ecological models of nitrogen processes in treatment wetlands have been evaluated and compared. These models were implemented, simulated, and visualized using the Modelica modelling and simulation language [P. Fritzson, Principles of Object-Oriented Modelling and Simulation with Modelica 2.1 (Wiley-IEEE Press, USA, 2004).] and an associated tool. The differences and similarities between the MathModelica Model Editor and three other ecological modelling tools have also been evaluated. The results show that the models can well be modelled and simulated in the MathModelica Model Editor, and that nitrogen decrease in a constructed treatment wetland should be described and simulated using the Nitrification/Denitrification model as this model has the highest overall quality score and provides a more variable environment.     

An agent-monitored framework for the output-oriented design of experiments in exploratory modelling

Exploratory modelling is an approach for modelling under uncertainty based on the generation and analysis of computational experiments. The results of exploratory modelling are sensitive to the way that experiments are designed, such as the way that the uncertainty space is delineated. This article introduces an agent-monitored framework—i.e. a design metaphor of the interactions among modellers and stakeholders and the simulation process—for controlling the design of experiments based on monitoring model behaviour in the output space. To demonstrate the benefits of the suggested framework in the exploratory modelling process, the article shows how the use of the framework with an output-oriented approach informs the delineation of an appropriate uncertainty space with an illustrative example in the decision-making context. The article concludes that the design of experiments based on feedback from the output space can be a useful approach: to control simulations in exploratory modelling; to build more confidence in final results; and to inform the design of other aspects of experiments, such as selecting policy levers and sampling method.     

基于Modelica的虚拟远程实验室

为了弥补传统实验教学模式的不足,介绍一种使用新型的、面向对象的多领域统一建模语言Modelica进行建模及仿真的电工电子虚拟远程实验室,并详述了其架构及远程实验的操作流程。构建两个子系统——模电实验系统及吹摆控制实验系统。通过调用Modelica标准模型库,实现了模电实验系统的建模;根据模块化建模的思想,对吹摆控制实验系统进行系统分解,利用Modelica编写每个模块的仿真模型,建立了可扩展的系统模型库,并基于该模型库实现了吹摆系统的构建。将两个子系统放在虚拟实验平台上仿真,仿真结果符合理论推算。     

MSC Adams/View二次开发技术在航天器太阳翼展开过程动力学分析中的应用

利用MSC Adams软件的参数化建模和二次开发功能,建立专为航天器太阳翼展开分析设计的仿真模块,为用户提供自动、快速的建模环境,使得进行航天器太阳翼展开过程的运动学和动力学分析工作效率更高、扩展方便,通过优化设计为设计者提供最优的设计参数.     

Reusability of model components for environmental simulation – Case studies for integrated coastal zone management

Model constructs in environmental models are seldom reused beyond the project lifetime or in other modelling studies. A library of reusable model components could facilitate the maintenance of existing models and make the design of new models more efficient. Although component-based design is the common standard in software engineering and manufacturing few examples are yet found in environmental science. The multi-disciplinary project SPICOSA used a common, component-based simulation framework for environmental modelling, based on 18 case studies through Europe. The development of high-quality model components with potential for reuse turned out to be a challenge despite of the guidelines and tutorial examples provided. Well-designed components are of appropriate granularity, encapsulated, with a limited use of connectors and proper data handling. Ultimately, the success of a model library depends on a sufficient set of quality components with complementary functionalities, a framework for quality control, and support of the environmental modelling community.     

Full-state prescribed performance pose tracking of space proximity operations with input saturation

This paper investigates the relative position tracking and attitude synchronization control for spacecraft close-range proximity missions with input saturation and model uncertainties. A robust saturated relative motion controller is proposed for this purpose. Prescribed performance functions are designed to guarantee the transient and steady-state response of the system and the full-state constraints. Then, a nonlinear disturbance observer is developed to estimate the lumped disturbance that comprises the effects of parametric uncertainties and kinematic couplings. At the same time, a linear compensator system is incorporated into the controller design to deal with the control input saturation. Finally, it can be proved via the Lyapunov theory that the closed-loop system is uniformly ultimately bounded stable. Simulation results on the spacecraft close-range rendezvous and docking mission validate the effectiveness of the proposed control approach.