Deformable Terrain Model for the Real-Time Multibody Simulation of a Tractor with a Hydraulically Driven Front-Loader

A real-time multibody model of an off-road vehicle can be used to analyze the dynamics of tasks, such as loading and/or transferring material from deformable ground. This analysis requires an accurate description of the mechanics, hydraulic actuators, and the terrain. The objective of this paper is to introduce a novel, real-time capable, deformable terrain/soil model that can interact with the mechanics of a multibody system model and the dynamics of a hydraulics model. To this end, a tractor is modeled by using a semi-recursive multibody formulation based on velocity transformation. The hydraulic actuation of the tractor's front-loader is modeled by using the lumped fluid theory. The tractor loads and transfers sand material from a deformable sand field (the ground), which is modeled by combining mesh-based and particle-based soil representation approaches for the real-time simulation of soil deformation. The work cycle of the tractor model follows a 3D maneuver that is used to load and transfer sand material. During the digging and dumping operations, the static sand field is converted into sand particles and vice versa respectively. For the presented work cycle, the real-time capability of the system is analyzed and determined. Furthermore, the dynamic actuator forces in the hydraulic cylinders are compared with the static actuator forces. The introduced real-time capable tractor simulation model can be utilized in product development and other product processes.