Research On Modeling Methodologies And Implementation Techniques For Functional-Behavioral Virtual Prototypes Of Spacecrafts

Spacecraft designers are faced with such new challenges as more complex space missions, shorter design durations and more tightening budgets. The traditional design philosophy becomes insufficient for the needs of the economic development and military applications. At the same time, the"faster, better, cheaper"philosophy is spreading in the design community. And the rapid development of virtual prototyping offers a technical basis for the concurrency engineering based innovations in design methodologies. With the goal of constructing functional-behavioral virtual prototypes (VPs) to support spacecraft design, this dissertation discussed the relevant techniques such as modeling/simulation methodologies, realization frameworks, software implementations, etc.In order to model the complex physical systems of multi-energy domain, a novel modeling methodology named the extended multiport approach (XMPA) was presented. In this methodology, the interactions between components are classified as energy interchanging and signal interacting, through the corresponding interfaces, energy ports and signal ports, respectively. The signal ports are further classified as event ports and continuous signal ports. Then, the whole system is constructed by connecting the involved components through their ports. From such concepts, a formal definition of VP was put forward. With this notion, the system hiberarchy can be described definitely. Furthermore, the virtual prototype view model was addressed, and each view is an implementation of the concerned VP.A formalized model of hybrid automata, namely the Multiport Hybrid Automata (MPHA), was introduced. In the MPHA, discrete transitions and continuous dynamics are described by Actions and Variables respectively. And the event interactions between subsystems are realized through the corresponding event ports, while the continuous ones through continuous signal or energy ports. Then, the connection operation between MPHAs was defined. Such notions are capable of describing the various interactions between subsystems, the hybrid dynamics inside a system or a block and the system hierarchy as well.A framework supporting the functional-behavioral modeling and simulation was presented. The Modelica language together with Dymola, a Modelica based software, and the Matlab/Simulink platform compose the modeling layer of the environment. And the DCOM technique was adopted to support distributed simulation. Additionally, the Modelica library was extended and a methodology for quickly translating Simulink models to DCOM components was developed.As an instantiation, one XMPA based functional-behavioral VP of some spacecraft attitude control system was implemented. This VP is composed of four modules as followed, the structures-and-mechanisms subsystem module, the attitude determination and control subsystem (ADCS) module, the C&DH module and the local environment (LoE) module. These modules are connected through their ports. Each module contains several mathematical models, i.e. the sunlight-pressure torques acted on a spacecraft with a cubical body, a planar antenna array and a pair of symmetrical solar sails and the momentum-wheel dynamics with bearing frictions, flywheel imbalances and structural vibrations considered, etc. The spacecraft's hiberarchy was depicted in Modelica. And the MPHA models of all levels of the system were defined. Then, respectively, the above four modules were compiled into DCOM components, of which the VP was constructed. Several simulations were conducted to investigate the sunlight-pressure torques, inner disturbances of reaction wheels, compensation for reaction-wheel frictions, momentum dumping using magnetic torquers and switching between controllers. Through such simulations, the above models and the VP modeling methodologies were validated.A VP environment supporting spacecraft ADCS design and analysis was implemented. This environment contains two parts, the modeling and simulation (M&S) environment and the spacecraft working visualization environment.The M&S environment runs on the basis of associated functional modules. For each module, there are two forms of existence, Simulink blocks and DCOM components. It is easy for the user to add new models, modify and update existing ones. Correspondingly, the software provides two running modes, the single-computer running in a Matlab engine and the distributed running basing on DCOM components. With this software, it is convenient to construct an ADCS configuration and analyze the system's performance.A spacecraft working visualization environment based on the Win32 multi-thread mechanism was realized. The geometric entities used were modeled by OpenGL and MultiGen Creator. Driven by data from other simulation programs, the software is able to provide animations of the orbital and/or attitude motions of spacecrafts, as well as coverage areas of various onboard payloads, either online or offline. The communication between the environment and other programs was accomplished though SOCKETs. This environment has been successfully applied in simulations of multi-satellite systems and spacecraft attitude dynamics.Through the above investigations, the methodologies for constructing functional-behavioral VPs of spacecrafts were established and a feasible implementation approach based on system integration techniques was explored. Such achievements, in the sense of implementing whole functional-behavioral VPs of spacecrafts, are significative and valuable.