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In recent years, electric power steering (EPS) has been developing rapidly abroad, and some domestic cars have adopted imported products, and there appeared an upsurge in development of EPS. But, EPS with independent intellectual property hasn’t been marketed till today at home. It is one of the important reasons that car’s reliability and safety isn’t ensured when being steered. So before EPS is industrialized, it must have a complete system with fault self-diagnosis, on-board monitor and safe-guard measures. The paper analyzes and identifies all kinds of trouble, and then establishes a complete fault self-diagnostic system of column-drive electric power steering.At first, according to EPS’s working principle, the paper analyzes all the familiar faults and modes of its parts such as torque sensor, motor and ECU, etc. Then, based on EPS’s dynamic model and the self-diagnostic principle of electric control system, it develops the fault self-diagnostic processes which comprise sign collecting, fault identification and fault disposal. At the same time, by comparison of several fault disposals, it advances some new methods, especially, such as the assistant steering-aid control after torque sensor trouble and protective control to avoid motor overheat. These new methods make the EPS excel imported ones of the same kind in some aspects.Secondly, according to the fault self-diagnostic strategy, the paper designs relevant hardware and software. The hardware includes single-chip system, all kinds of circuits and its anti-jamming design. The software design is mainly to compile a complete program to dispose of the collected sign and identify all the trouble, then control the correlatively executive parts to finish the whole work.Finally, the paper advances evaluation targets about the reliability of fault self-diagnostic system, completes some correlative tests on the bench, and evaluates the validity of the self-diagnostic strategy and its safe-guard measures. In addition, considering the near correlation between EPS and driving safety, it points out it necessary to take into account the influence of EPS’s trouble to car’s lateral distance. So the self-diagnostic strategy developed is proved to be reasonable and effective again.
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