Research On Compiling And Solving Of The Unified Multi-domain Model For Engeneering Systems

With the development of science, technology and engineering practice, modern electromechanical products are increasingly complex and usually become complex engineering systems consisting of a variety of mechanical, electronic, hydraulic and control subsystems. Simulation based on unified multi-domain models has become a new generation of CAE technology supporting innovative design of complex engineering systems. The key of the technology is to achieve compiling and solving of unified multi-domain models. Based on the unified multi-domain modeling language Modelica, in order to build a new generation of unified multi-domain modeling platforms and develop the key enabling technology for the platforms, the paper investigates a number of key technologies in compiling and solving unified multi-domain models. The paper is funded by the National High Technology Research and Development Program of China (863 Program) and the National Natural Science Foundation of China. The main contribution of the paper includes the following.First, the Modelica semantic constraints the paper analyzes in detail and systematically summarizes the mapping rules of multi-domain models. Based on compiling principles and Modelica standards, the paper analyzes in depth the key Modelica semantics from the perspective of semantic constraints, provides an analysis table of associated semantic constraints of the key semantics and determines the Modelica compiling framework based on it. Further, the paper systematically summarizes the mapping rules from Modelica hierarchy models to flat hybrid equation systems and analyzes typical features of Modelica equations systems.Second, the paper explores the symbolic index reduction and its consistent initialization in high index differential-algebraic equations (DAEs), and proposes the processing frame of numerical solving. For flat hybrid equation systems consisting of large-scale differential equations, algebraic equations and discrete equations, the paper introduces an analysis approach based on the method of Block Lower Triangular (BLT), focusing on dummy derivative based symbolic reduction and its consistent initialization in high index DAEs. For the ordered equation subset sequences obtained from the analysis of equation systems, the paper analyzes the continuous-discrete solving methods of hybrid differential-algebraic equation systems and presents the processing frame of solving based on numerical computation.Third, the paper solves the symbol processing problem of consistent residue constraints in multi-body modeling in Modelica. Centered on the contradiction between consistent redundant constraints and the Modelica single assignment rule in multi-body modeling, the paper derives the multi-body dynamics formula based on the general Kirchhoff's law by the Newton-Euler method, and then divides the consistent residue constraints into over-determined connection redundant constraints and repeatedly-constrained degree of freedom redundant constraints. For the former, the paper analyzes the sources of redundant constraints and proposes the determination and elimination of redundant constraints based on virtual connection graphs. For the latter, the paper presents the determination and elimination of redundant constraints in the common mechanisms with planar loops.Finally, based on the aforementioned findings, the paper achieves the complier and solver of the unified multi-domain modeling and simulation platform MWorks. The paper describes briefly the features, functions and framework of MWorks platform and illustrates the effectiveness of the platform by some practical engineering applications.