Modeling and experimental validation of the implement-chassis interaction for construction machines

Wheel loaders are everyday off-road machines heavily used worldwide for several different reasons.?? ??This thesis aims in the development of both a numerical and an analytical model for the digging system of a generic wheel loader. Knowing the geometric configuration (boom and bucket angles or lift and tilt cylinders extensions) at each instant, both the models are able to compute the location, in a two-dimensional plane, of a set of points belonging to the system. These points are then used to calculate the forces required at the hydraulic cylinders to balance the external forces which can be either, in the simplest case, just the component weights, or the forces exchanged at the bucket during a normal loading cycle. The models are subsequently validated through a comparison between experimental field test data and data generated through the models. ??Finally, the aforementioned models serve for computing external forces acting on the bucket. The models will start from the geometric configuration (boom and bucket angles sensed from the machine) and the tilting and lifting cylinder pressures (sensed from the cylinder rods and pistons) to compute the forces acting at the bucket. This is the inverse procedure with respect to the one that gives the cylinder pressures. Thus, in addition, with this work it would be possible to estimate how the forces exchanged at the bucket are reflected into the vehicle dynamics since these models are able to compute the reactions forces acting at the chassis connections.\\?? ??In conclusion, the models developed will not be just useful for having a general idea of the excavation system behavior by itself, but might also be used for improving other currently ongoing investigations, such as: developing better traction control models, vehicle dynamic models, active oscillations damping, etc. ??As part of a further work, a concept for a work pile model able to express all the forces exchanged between bucket and pile itself during digging operations is investigated here. Thus, a future work proposed here is trying to validate, through the utilization of the digging force models, this new concept of pile model that focuses on the pile-bucket interaction forces.