Development of a grain size distribution evaluation system for thermal storage rocks using an RGB-D camera

A simple evaluation system for the grain size distribution of rocks has been developed using an RGB-D camera. The system uses a camera to acquire color and depth images of rocks stacked randomly, and then estimates the surface area and volume of individual rocks within the angle of view through image area segmentation and shape completion processing to obtain a detailed grain size distribution. The accuracy of the average diameter estimation was evaluated by comparing the diameter obtained by proposed method with the diameter experimentally obtained by the conventional methods. As a result, the error in the volume equivalent diameter was 3.4 mm from the value obtained by the conventional method (39.1 mm), and the error in the surface area equivalent diameter was 0.5 mm from the value obtained by the conventional method (42.3 mm). It was confirmed that the average diameter obtained by developed method agrees with that by the conventional method within the expected systematic error of 5 mm for the entire developed system.