Motion analysis of a semi-legged vehicle with soil deformation taken into account
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A semi-legged vehicle was designed for forestry use. The equation of motion for the machine coupled with the equation of motion for soil was derived. Furthermore, the motion of the machine was analyzed taking into account soil deformation. The Extended Distinct Element Method, which can analyze both continuous and non-continuous materials, was used as a soil model. The effects of foot area and spike length were simulated by using two kinds of uniform soil. The specific power of a foot area of 3,200 cm2 was smaller by 0.025 than that of a foot area of 1,600 cm2 on soft soil. This was equal to the consumption energy for moving 2.5% of the machine weight, about 140 kgf. The maximum values of the forces acting on the second hydraulic cylinder were 300 kN and 500 kN, and the weights of the hydraulic cylinder generating these forces were 121 kgf and 229 kgf with spikes that were 0 cm and 30 cm long on hard soil, respectively. In a walking motion, such as lowering the boom to the ground, raising the stabilizers, and advancing the machine, the machine with a larger foot area and shorter spikes was more suitable for lightening the total weight and improving energy efficiency.
Key wordsenergy efficiency extended distinct element method semi-legged vehicle
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