| Summary: | 碩士 === 國立臺灣科技大學 === 機械工程系 === 91 === The regular elliptical method and the average angle method are used to evaluate the circumferential discrepancy of the piston skirt profile of a four-stroke motorcycle engine. These methods were also currently applied to evaluate the circumferential discrepancy of the piston skirt profile of a two-stroke motorcycle engine in industry. However, the piston skirt profile of a two-stroke motorcycle engine is an irregular elliptical shape, theoretically, the above mentioned methods cannot applied directly to evaluate the piston skirt profile of a two-stroke engine.
The objective of this study is to introduce the fitness method to evaluate the circumferential discrepancy of the piston skirt profile for a two-stroke engine based on the data points measured on a CNC coordinate measuring machine. This method utilized the Closed B-Spline Curve method to interpolate the internal data points based on the designed profile data points which have an interval of ten degrees, and the concept of minimum sum of error squares to determine the angular deviation of the piston skirt profile. According to the test results, the proposed method could improve the analytic accuracy and had good consistency with the measurement result of the roundness measuring machine.
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