The Fault Diagnosis Approach For The On-orbit Satellite Based On The Transition System Model

Fault diagnosis technology is an important part of the spacecraft autonomouscontrol and management system, it may provide the necessary support for thespacecraft autonomous control, and the security for its safe and reliable on-boardoperation. In this thesis, based on the background of spacecraft fault diagnosistechnique, the diagnosis theory and its applications which focus on the transitionsystem model and the first principle diagnosis method were conducted deeply inorder to satisfy the demand for the fault diagnosis system from the spacecraftautonomous control and the existing problems. The main research contents andresults are as follows:According to the real-time requirements for the algorithm from the spacecraftautonomous diagnosis technique, the separation strategy of conflict recognition iscarried out and the calculation method of analytical redundancy is put forward, thatmakes the main calculation of the conflict recognition to be completed in theoff-line phase. Meanwhile, the state memory mechanism which introduces thehistorical diagnosis result is researched in the candidate generation process in orderto avoid unnecessary computation. Applying the diagnosis framework to a primaryelectrical power system, and compared with traditional methods, it is verified thatthe proposed method can effectively improve the efficiency of diagnosis.In order to improve the accuracy of the diagnosis system, the structure of thetransition system model and types of the diagnostic knowledge are studied. Byintroducing the causality diagnosis knowledge into the model and using thehierarchical structure to organize the diagnosis knowledge, the hierarchicaltransition system model and the corresponding diagnosis method are proposed.When diagnosing through this method，the causality diagnosis knowledge is used toimprove the the completeness of the model and guide the reason process in order toreduce the state matching space, and it will cause the improvement of the efficiencyof diagnosis, the accuracy and the resolution of the diagnosis result. Applying thismethod to the telemetry and command subsystem of a satellite, the accuracy of thediagnosis and efficiency of diagnosis are verified better than those of the traditionaldiagnosis method.Aiming at the fuzzy problem of the diagnosis result due to the fact that thetraditional diagnosis method based on transition system model cannot match theobservation and the target state completely, the distance function based on theviewpoint of energy is defined to evaluate the similarity between the two states.Based on the distance function， the fuzzy transtion system model and the corresponding diagnosis method are proposed, and the distance function is used tocalculate the distances between the observation and each target state in order toevaluate the current trend of state transition. Using the typical failure modes of theprimary electrical power system as example, the effectiveness for solving theproblem of incomplete matching and the improvement of the accuracy of thediagnosis result are verified.Through the research of the existing analysis method for the diagnosability ofmodel, aiming at the problem that these methods are only limited to the staticanalysis based on the sensor layout and structure of the model which causes that theanalysis for the transition system model is accurate, a diagnosability analysismethod for the transition system model is proposed. This method carries on thediscussion about diagnosability from the structure and the function of model,preserves the static analysis process and the dynamic process of system operation isalse considered. Using this method, if a component is confirmed that satisfies thediagnosability, that means, the failure effect can be detectable, and withoutannihilation producted by the functional outcome of other components. In addition,it can also ensure that the failure effect among the various failure modes cannot beconfused for the function. This method is applied on the primary electrical powersystem, and its effectiveness can be verified.