Consistent pile-shape quantification for autonomous wheel loaders

Abstract

Abstract-This paper presents a study of approaches for selecting an efficient attack pose when loading piled materials with industrial construction vehicles. Automated handling of piled materials is a highly desired goal in many construction and mining applications. The main contributions of the paper are an experimental study of two novel approaches for selecting an attack pose from 3D data, compared to previously published approaches and extensions thereof. The outcome is based on quantitative validation, both with simulated data and data from a real-world scenario with nontrivial ground geometry. I. Introduction A. OverviewHandling heterogeneous piled materials is a core component in many construction and mining applications. A typical work cycle of a wheel loader working in these applications (see Fig. 1) consists of three repeated tasks: loading, hauling, and dumping. Hauling between the load and dump points can be handled in a number of ways, whether by GPS-waypoint following, or some more flexible approach from the rich literature on mobile-robot navigation. Dumping is relatively straightforward and can, in principle, be performed with preprogrammed motions. Efficient loading is a harder problem than the dumping sequence, and no practical solution for fully autonomous vehicles exists today. For economical and environmental reasons, it is important that the bucket is filled maximally in each load cycle and that the mechanical stress on the machine is minimised. When an automated wheel loader approaches a gravel pile, then, it should first analyse the shape of the pile (from a 3D range scan) and evaluate potential attack poses along the pile edge; i.e., positions and orientations at which it is efficient to approach the pile. This paper presents a comparison of previously published approaches and also presents the results of two novel methods for selecting attack poses. The outcome is based on quantitative experimental validation, both with simulated data and data from a real-world site.The present paper contains several contributions. a) Head-to-head comparison: Prior work on automated loading has only described single methods. This paper presents a comparative evaluation of two previous methods as well as two novel methods.b) Real-world evaluation: Prior publications only present experiments in simulation or in lab-like setups. This paper presents evaluations on real-world data from an asphaltproduction site with nontrivial ground geometry.c) 3D extension of Singh and Cannon [12]: A 3D extension of the 2D method that was published by Singh and Cannon [12] has been implemented and evaluated.