The dynamics of a wheel loader handling unbound granular material

A wheel loader is a heavy equipment used to perform granular material handling operations. The complete machine model is developed in Simulink, meanwhile a discrete element method (DEM) solver, modelling unbound granular materials is developed in Demify. Virtual development technologies allow for more efficient testing of the machine and its sub-systems. The implementation of models between different software is required, though there is a lack of standardized interfaces. At this step, FMUs are the leading component making up for a possible integration between different working environments. The work focuses in creating an interface between the two software so the sharing of information is possible. The granular material was previously modelled with the DEM solver GRAPE, collaborating with Fraunhofer ITWM , which is based on a spherical shaped particle representation to model soil material. On the other hand, crushed rock aggregates which we are working with, require a well-resolved rock particles' representation of the irregular and angular shape. A new GPU solver for complex particle shape based on non-convex polyhedral triangulations has been implemented, allowing for high fidelity rock shape representation. In this project, the created FMU files contain the information needed to relief the communication issue between the software and make the co-simulation possible. The DEM solver Demify provides high fidelity results in terms of material contact force detection, while Multi-Body Dynamics (MBD) Simulink integrates the equations of motion. The computational performance, involving the computational cost and the physical fidelity, is a pivotal factor used to evaluate and optimize the design of a new level machine-particle interaction. Reliable and computationally effective results are obtained in the interaction between machine and non-convex shaped rock particles. In addition, a realistic and an efficient communication between the two software is reached. ​