A robust spline filter algorithm based on M-estimate theory

In surface assessment, the reference line extracted using the profile filter are always distorted by freak characteristics of the scratches and peaks of the profile. In order to overcome this problem, the robust spline filter and the Gaussian regression filter were recommended by ISO standards. However, their different algorithms and different filtering characteristics lead to the different mean lines for the assessment of the same surface. A novel robust spline filter based on the M-estimate theory is developed, which possesses the same filtering characteristic as the Gaussian regression filter. It is available for use and transfer of the international standards, as well as the comparison of the surface assessment results.