Yang Mengfei

Cyber-physical systems modeling method based on Modelica

Cyber-physical systems (CPS) is an integration of computation with physical systems and physical processes. It is widely used in energy, health and other industrial areas. Modeling and simulation is of the greatest challenges in CPS research. Modelica has a great potentiality in the modeling and simulation of CPS. We analyze the characteristics and requirements of CPS modeling, and also the features of Modelica in the paper. In respect of information model, physical model and model interface, this paper introduces a unified modeling method for CPS, based on Modelica. The method provides a reliable foundation for the design, analysis and verification of CPS.

Review and prospect of atmospheric entry and earth reentry technology of China deep space exploration

Review of technology development of atmospheric entry and earth reentry of China deep space exploration is given in the paper, as well as brief review of similar missions by US, USSR/Russia, ESA and Japan. Development of common technology such as aerodynamics, thermal protection, guidance, navigation and control (GN & C), parachute, track, telemetry and control (TT & C) of atmospheric entry and Earth reentry in China is described in detail. At the end, some suggestions for technology development of atmospheric entry and Earth reentry of future China deep space exploration are given.

Attitude control of a spacecraft using self-triggered control approach

Modern spacecraft systems refer to an engineering platform that depend on the integration of physical systems with control, computation, and communication technologies. In this paper, a self-triggered control approach is introduced for the spacecraft attitude control problem. The self-triggered control proposed in this paper guarantees the desirable stabilization behavior of the spacecraft. Besides, it allows a reduction of the computation and communications demand. Furthermore, we derive the equations of attitude motion. A general procedure leading to self-triggered implementations of feedback controllers on a rigid spacecraft has been developed as well. Finally, the efficiency and feasibility of the obtained results is illustrated by means of a numerical example.

Evolutionary Fault Tolerance Method based on Virtual Reconfigurable Circuit with Neural Network Architecture

With the continuous development of computer and electronics, the idea of artificial intelligence has been integrating into the fault tolerance research. As a valuable and prospective intelligent fault tolerance technique in high reliability and high safety applications, the evolvable hardware fault tolerance technique is becoming an important and widely applicable method. However, this technique confronts two difficult problems: evolved circuit scale and evolution efficiency. Toward these problems, we present a programmable architecture called neural network architecture-based virtual reconfigurable circuit (NNA-VRC), and an evolutionary fault tolerance method based on this programmable architecture. The NNA-VRC-based evolution method simplifies the structure and configuration of programmable architecture, avoids illegal interconnections during the circuit evolution, and implements high level (module level) evolution. The experiments of this paper show that a function module scale circuit is evolved efficiently. Furthermore, NNA-VRC-based evolution method can recovery from many injected fault patterns, behaving a strong feature of fault tolerance.

Star extraction based on clustering within a star tracker

The traditional star extraction methods of star tracker need much processing time and large image memory, resulting in slow attitude acquisition and complex electronic circuits. A new star extraction method, star extraction based on clustering, was developed. The analysis of on-line background estimation algorithm and clustering algorithm in the new method was introduced. The method was realized in one of the novel star trackers developed by Beijing Institute of Control Engineering (BICE), on-board circumlunar return and reentry spacecraft of 3rd phase of China lunar exploration program. According to the house-keeping data packages recorded during on-ground real sky test and the flight mission, the processing time of star extraction was reduced by 84% at least and the image memory was reduced by 99% at least, compared with traditional methods. The results indicated that the star extraction based on clustering had advantages in processing time, memory and migration,which made it possible to realize the method in almost all kinds of optical sensors.