Abstract: According to the last report of ILO (International Labour Organization), every year 2.2 millions
of people die or loose the working capability because of accidents or work-related diseases. A
considerable percentage of these accidents occur during the execution of motion and transportation
tasks and during human-machine interaction involving heavy duty machines. The causes for this
phenomenon are several and complex. For sure, the insufficient degree of interaction between the
human operator and the guided machine is one of the major problems, as report underlines.
The safety of the operator of an earthmoving machine is a very important issue. The dangerousness
of the working environment forces the worker to consider several parameters at the same
time, often using the sensitivity matured by experience. In fact, depending on the working task, on
the weather conditions, on the surrounding obstacles, on the cargo’s weight, the motion of machine
actuators must be limited to avoid machine tipping over or knocking the surrounding environment.
In this work, an estimation of the center of mass of a telescopic handler is introduced, in order to
predict its behavior in static conditions. Our main goal is to reduce the working load of the machine
control system in order to employ low cost electronic devices. In fact, the use of the simplified
model presented in this paper would allow the control system to predict in real-time a forthcoming
unsteady condition of the machine at a very low computational cost.
The work started with the development of a simulation model, considering the machine as a
system of interconnected rigid bodies (multi-body model). By means of this model, the position of
the machine center of mass during the operative phase is studied and a simplified expression of its
coordinates is obtained. Finally, the results achieved by means of the new equations are compared
with the ones calculated with the full model. Simulation results show that the difference between
theoretical and estimated coordinates is not relevant to the task.
In this first work, the strain of the ground, the dynamics of the machine and the residual vibration
of the boom are not considered because their effects are never included in the load charts provided
by manufacturers. Future work will aim to extend this study to account for the dynamics of the
machine. The goal of our work will be to obtain a simplified real-time estimation of these effects in
order to develop a stability control system, which will exploit the first results provided by the present
work and extend them to dynamics.