Multipoint Recursive Sequential Three-point Method for On-machine Roundness Measurement

A newtime-domain method, which is called the multipoint recursive sequential three-point method, is proposed for on-machine roundness measurement of cylindrical workpiece. It has the following features: (i) assuming no prior knowledge, (ii) providing more information of the roundness profile than the sequential three-point (S3P) method, (iii) reconstructing the roundness profile including sharp features. In the proposed method, recursion of difference equations in the time domain is used to determine the relationships between different data groups instead of the fast Fourier transform (FFT) algorithm andthe inverse fast Fourier transform(IFFT) algorithm, which is simpler and capable of expressing the discrete roundness profile with sharp features correctly. In the meantime, the establishing conditions of the proposed method are given by theoretical analysis. The eccentric circle, resulting from the inaccurate initial value of the recurrence equation, is removed by the least-squares method. Theoretical analysis and simulations have been conducted to verify the effectiveness of the proposed method.