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Knowledge representation is the necessary process to build an autonomous fault diagnosis expert system for satellites. In order to enhance the knowledge representation ability of time-related rules and r-of-n rules, an improved fault Petri net model for knowledge representation is proposed on the basis theory of fault Petri net model. The alarming threshold function and the fire threshold function is introduced, the alarming conditions and result is given in the form of definition, similarly, the fire conditions and result is redefined. A transition gives an alarm for some time and then could fire, the improved fault Petri net model could present the time-related rules while the fault Petri net model couldn't. Further more, the improved fault Petri net model could present the r-of-n rules much more conveniently than the fault Petri net model, it needs much fewer transitions to present the same rule. The improved fault Petri net model upgrades the knowledge representation abilities and provides basic conditions for the knowledge representation of the diagnosis expert system.

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In order to meet the verification requirement of new technologies for small satellites such as autonomy, fault tolerant control, dynamic uploading of data. A semi-physical simulation platform of OBDH subsystem for small satellites is put forward, the platform provides software and hardware verification environment of OBDH subsystem for small satellites. On-board computer simulator is developed based on the SPARC V7 TSC695, in order to get rid of the limitation of TSC695 programmer a program updating method is proposed for onboard computer simulator by simulation management PC. Dynamic software module on-board loading is implemented. A reliable on-board CAN bus polling algorithm is presented, the thermal control model and power management model are established, which supports the open-loop or closed-loop thermal control and power model calculation. The problems encountered in the process of system integration test are analyzed and resolved, which give lots of inspiration.