Research On Roundness Evaluation Algorithm And Programming

Roundness error is the variation between the ideal circle and the profile of the cross section, which is perpendicular to the axial line of solid rotation, the value of roundness error affect the rotary precision, the centring precision and the reliability of fastened conjunction directly. Roundness error is an important parameter to judge the geometrical quality of turning parts. It is generally measured by the roundness measuring instrument. The national standard (GB/T 7235) defines four kinds of roundness evaluating methods, such as the least squire circle method (LSC), the minimum circumscribed circle method (MCC), the maximum inscribed circle method (MIC) and the minimum zone circle method (MZC). Among the newly issued standards—Geometrical Product Specifications, by the International Standard Organization (ISO), there is a new evaluating method—Chebyshev fitting method. Studying on the algorithms of evaluating methods and developing relative software are the primary task to carry out automatic measuring of roundness error, it is very important for designing or modifying of the roundness measuring instrument.First of all, this thesis introduces the evaluating theory of LSC, establishes the mathematical model of the least squire circle. With the platform of Virtual Instrument development software (LabVIEW), combined with the subroutine algorithm written in C language, the design and develop of LSC evaluating software are fulfilled.Then, it represents the evaluating theory and judge criterions of the MIC, the MCC and the MZC, presents detail methods of solving and judging and calculating procedure, and actualize the roundness calculating of non-analytic expressions using moving center algorithm. Fulfill the design and develop of relative evaluating software.Finally, the Chebyshev fitting method of circle is presented, and the Chebyshev fitting model of roundness evaluating is established base on the Chebyshev fitting theory. After simplified, the solution of the simplified model is studied, and relative evaluating software is developed.The roundness evaluating software developed in this thesis is actualized on the platform of LabVIEW, it has the same operating environment and friendly manipulation interface of Virtual Instrument. The accuracy of the evaluating program is examined by calculating the example data, and the reliability of the program is tested and verified by loop calculation of the input random. The roundness evaluating program can be used practically.