Research On Reliability Design Theory And Methods Of NC System

The ultima reliability of NC system is decided fundamentally by its design and the reliability design of NC system is one of main aspects of research on NC technology reliability. Reliability design theory and methods of NC system are discussed deeply in this dissertation and its main contents are listed as follows.According to the Waterfall Model of software system development, the reliability engineering process of embedded NC software system on the base of SDLC is studied and it is divided into 3 phases: early phase, middle period phase and later period phase reliability engineering, the contents of which are discussed in detail.The structure reliability of NC system in the early phase of reliability engineering is studied and modeled and the hierarchy-module structure of NC system based on RTOS is put forward. The Improve-Littlewood model is brought forward from the traditional Littlewood model through analyzing the NC system functions and the new model is applied in the structure reliability analysis of real NC system.That the reliability design importance of different function modules of NC system are different is proposed and the factors that influence the importance of module reliability design are discussed, including module size, module complexity, hardware's influence on module design and failure index of the structure reliability, and the methods how these factors are computed are studied. Fuzzy mathematics is maken used of in judging the importance of module reliability design. Under the conditions of considering all the factors, fuzzy synthetical judgments of module importance are done and the judgment results are collated.The Minimum Deviation Interpolation Method is improved effectively through studying its characteristics. Lots of arithmetic formulae in the different quadrants are transformed into few uniform ones, which can improve the interpolator module design reliability because it simplify the configuration and code size of interpolator program. And the running-time characteristic of interpolator program is also studied in the paper. It is proposed that NC system can become unreliable in real time when interpolation period approaches the interpolation-program running time.Some reliability design methods used in the particular design and programming phases of NC system design are discussed and the examples are given how to apply them in the real system design.How to enhance the NC system reliability in the testing phase is studied and the NC system testing is divided into 2 parts: function reliability testing and real-time reliability testing. The research on the function reliability testing is mainly how to design some testing examples that can cover with testing all the functions of NC system. In the research on real-time reliability testing, it is put forward that interpolation module and position control module are the testing emphases and the methods how to test the real-time reliability of them are discussed.