Abstract
The purpose of this work is to compare, with the same digging diagrams, the velocity, accelerations and dynamic performances of two excavators with different arm configurations. In particular, constructive solutions involving the use of two and three mobile arms will be examined. For excavators the different construction geometry (2-3 arms) is mainly dictated by reasons of use, in fact the 3 arms solution is normally used in areas that allow poor mobility of vehicle and present obstacles during the excavation phase. The dynamic comparison between the two solutions is performed on real working conditions to which they can be subjected during the exercise. The elaborations are performed both analytically and numerically. Essentially the analysis shows that in the condition of leveling and lifting at minimum distance from the rotation axis the dynamic performances are similar, there are significant differences in the lifting condition at the maximum distance. The diversity also implies significant variations in the forces of the hydraulic cylinders used to move both the load and the arms, an aspect which finds greater emphasis even in the case in which the arms are made by adopting unconventional materials for their realization as aluminum and composites.
Highlights
Excavators are very versatile earth-moving machines, they have a wide payload range which obviously corresponds to a different load diagram [1]
The present research concerns the kinematic and dynamic analysis of a two and three excavator arms comparing their behavior on real load conditions evaluated experimentally
The comparison was performed analytically and numerically with two software obtaining a substantial convergence in the values and in the acceleration trends for the different points that identify the arms. These values were used to optimize the weight of the arms of the excavators, focusing on the hydraulic cylinders needed to move the load and the arms
Summary
Excavators are very versatile earth-moving machines, they have a wide payload range (from 5000kg to 50000 kg) which obviously corresponds to a different load diagram (for example digging depth from 3m to 12m and distance from the rotation axis from 4m to 15m) [1]. This choice was made both to simplify as much as possible the model, so to lighten the simulation, and because in this way it is possible to bring back the geometry of the arms of an excavator to the geometry of a SCARA robot taken as a base of study for this comparative work [15,16]. To proceed with the simulation [17,18], once the components have been made and the necessary constraints and couplings have been set, it was decided to place a “motor” at the end of the stick, in correspondence of the fixing pin between the bucket and the stick going to set the law of motion
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