Study on surface roughness evaluation method of inner surface of engine bore by RANSAC method and least squares method

The internal surfaces of automobile engine bores should have strong resistance against friction and wear to reduce environmental impact. Surfaces with smoothed tops of surface irregularities are used to meet this requirement. Such surfaces are known as plateau surfaces because of their plateau-like shape. The roughness parameters obtained by analyzing the surface roughness of the plateau surface can assist in evaluating the frictional state and performance of the plateau surface. In addition, the understanding of the plateau surface conditions can contribute to the realization of fuel efficiency. Currently, plateau surface analysis methods are defined in ISO standards and JIS. However, these methods require complex computational algorithms and a significant amount of analysis time. Therefore, previous studies have proposed several methods using simple computational algorithms to solve this problem. Sakakibara et al., the authors of the previous study, proposed a method based on the concept of RANSAC. This method achieved high analysis accuracy for the plateau surface by setting detailed conditions. However, the optimal conditions are set manually, the productivity is low owing to the manpower and time required. This study proposes a new method that automates the setting of the conditions. This method does not require human intervention and is expected to contribute to the improvement of productivity at production sites.