Abstract
Results of theoretical studies of dynamics of the machine-tractor assembly taking into account the influence of a bearing surface profile were presented. It was established that in the course of operation, the machine-tractor assembly is exposed to a number of external factors leading to a change of vertical loads on the chassis and the engine. Mathematical models of dynamics of a tractor and a machine and a tractor unit consisting of a tractor of pivotally connected arrangement and a trailed sower were constructed. Such models make it possible to study dynamics and oscillatory processes of multi-element units. A mathematical model of tractor wheel dynamics was formed. Speeds and angles of orientation of elements of the machine-tractor assembly in space were determined. Influence of profile of the bearing surface on the unit elements when moving in the field prepared for sowing and the field after plowing was calculated. Theoretical studies of the influence of the bearing surface profile on dynamics of the machine-tractor assembly were performed on the example of KhTZ-242K tractor and Vega-8 Profi sower (Ukraine). When moving, the sower frame has a smaller amplitude of vibration accelerations than that of the tractor. Accordingly, the tractor has higher oscillation energy because it rests on the ground through its wheels having appropriate stiffness. The sower moves with its working bodies immersed into the soil which leads to a decrease in the amplitude of oscillations. The highest energy of amplitude of oscillation accelerations of the sower frame in the vertical direction was observed at frequencies of 15.9; 23.44; 35.3 and 42.87 Hz. It was found that the increase in working speeds of agricultural units leads to the fact that oscillations of all components reach significant values. This entails an increase in dynamic loads on soil and, as a consequence, its compaction
Highlights
The operating procedure of a machine-tractor assembly (MTA) is influenced by many external factors causing the action of extra vertical loads on the unit chassis and engine
The random nature of field surface irregularities is the main feature of conditions of movement of mobile units and, the dynamic forces transmitted by movers to the ground
Dynamic wheel model: XOYZ is global coordinate system; xoyz is connected coordinate system; ωk is the angular speed of rotation; υ is translation movement speed; hk is the height of the soil profile; rd is the dynamic radius of the wheel; drk is dynamic deformation of the wheel in the vertical direction; Px, Py, Pz are the forces acting on the wheel and applied to its center; Pk is the tangential traction force; Mk is the torque; Pf, Mf are the force and moment of rolling resistance, respectively; Pδ is the force of lateral skid; kw and Сw are yield and rigidity of the tire in the vertical direction, respectively
Summary
The operating procedure of a machine-tractor assembly (MTA) is influenced by many external factors causing the action of extra vertical loads on the unit chassis and engine. These factors include heterogeneity of physical and mechanical properties of the cultivated soil, unevenness of road surface, uneven traction resistance of a unitized agricultural machine. These impacts are random and described by random functions. Studies dedicated to the assessment of the impact of the bearing surface profile on dynamics of the machine-tractor assemblies are relevant
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