Design And Onboard Faul Diagnosis Of Orbit Cintrol System For Pico-Satellite

Micro satellite technology is developing beyond our imagination. In order to complete the tasks such as satellite formation flying and constellation, the orbit maneuver ability would be necessary. Consequently, the study and development of technology of the micro propulsion system is quite essential and should be first to be taken into consideration.In this paper, on the basis of domestic and international researches on micro propulsion, combined with the actual pico-satellite mission requirements and platform constraints, the liquefied ammonia propulsion system is designed, which has the advantages of small volume, light weight, integrated multifunction, etc. Combining propulsion system characteristics and mission requirements, this paper have completed the appropriate hardware and software design. In order to improve the security of orbit control system(OCS), the hierarchical fault diagnosis method is proposed and simulation shows that the method can effectively locate the fault source.After describing the design of orbit control system, combining with the design index and domestic selection experience, the selection scheme of liquid ammonia propulsion system is determined ultimately. With the mass0.835kg and volume0.6L, The final design of liquid ammonia propulsion system meets various function indexes as well as the reliability and safety.With the propulsion system as the core, the design of hardware circuit and software is completed. The hardware circuit is divided into information monitoring module, control switch module and communication module. The hardware circuit uses MCU as processor, and the corresponding MCU software design, according to the function module, is divided into five parts:initialization module, data acquisition module, communication module, instruction execution module and emergency fault processing module. The max power consumption of OCS reaches5.72W.This thesis presents a method of hierarchical fault diagnosis for OCS on-orbit. According to the features of the OCS, the level architecture is established and the OCS is divided into three layers. Based on the relationship between components established by the characteristics of each component, fault location algorithm is proposed. Then take an specific OCS as an example, with the knowledge base built by production rule expressed by the knowledge which is obtained through analysis on fault detection for the components at each layer separately, and the basis of establishing inference engine using the level architecture, the fault diagnosis expert system based on rules is designed. Finally, a numerical simulation on the proposed method is conducted using MATLAB, and the results show that the method can effectively locate the fault source with the characteristics such as intuitive and unity knowledge expression, higher efficiency and so on.