Development and evaluations of an approach with full utilization of point cloud for measuring the angle of repose

Abstract

The angle of repose (AOR) is an indicator of the fluidity of granular materials. The uncertainty for determining the material AOR includes the deviation in the global shape of repeatedly generated heaps and measurement uncertainty for each heap. A suitable method of measuring the AOR helps to decrease the latter. For this aim, a measurement method with full utilization of a three-dimensional (3D) point cloud was developed. About the approach, there was a sector-shaped domain for batch detection in a cylindrical coordinate system. The progressively rotating domain could calculate the slope AORs. Then the average of total slope AORs was determined as the heap AOR. A series of simulated heaps with varying particle shapes, heap sizes, particle sizes, and known AORs were measured by the approach for evaluating its performance. The heap 3D data from a publicly available dataset was used, which contained fresh corn grains, lignite, wood chips, and limestone with 4 replicate heaps for each material. The two other published 3D methods for calculating the AORs were used as comparison items for the developed method. Factors of measurement uncertainty depended on these three methods. And the first heap data of each material was configured with a gradient of 6 for this factor. The coefficient of variation (CV) of the measurements by each method for 6 gradients of a heap was used to assess its measurement uncertainty. The replicate heaps of each material were measured using these methods. The evaluation of the measurement uncertainty showed that the CV of the measurements by the developed method for 6 gradients of a heap was significantly lower than it was by the two other methods. This article gives and evaluates a method for measuring the AOR, and it can decrease the measurement uncertainty.