Integration of digging forces in a multi-body-system model of an excavator

The digging process using an excavator bucket was modelled, with the objective of introducing the interaction with the environment into the multi-body-simulation method. With today’s software tools, the dynamic behaviour of complex machinery can be effectively simulated. However, interaction with the environment, especially with soil is very challenging. This paper aims to contribute to meeting the challenges in this field of simulation. The given implementation makes use of analytical approaches originating from classical soil mechanics. After an analysis of the digging process, excavating tools, digging mechanisms and existing force calculation methods, approaches based on the ‘fundamental earthmoving equation’ and the ‘cavity expansion theory’ were used to model bucket filling, soil transport and bucket emptying along with accompanying forces throughout the described process. The simulation results are compared with experimental data available in publications. The main finding of this paper is a co-simulation, with a multi-body-simulation model capable of estimating the digging forces dynamically, with very high accuracy for low cohesion soil. Furthermore, the model also visualises the geometry of the soil surface, and the bucket contents, during the excavation cycle, in 2D, and can be extended for use in 3D.