Abstract
KEYWORDS:
root harvester, dynamic model, mathematical model, computer-aided simulation
ABSTRACT:
The quality indicators that characterise the functioning of most mobile aggregates are significantly determined by the type of their plane-parallel motion. The paper present method to constructing calculated model of plane-parallel motion of root harvester. The equations in Lagrange form of the second degree were adopted as initial equations. On results of numerical solution of obtained system of differential equations on computer and investigation by Lyapunov method were determined the dynamic characteristics of root harvester.
The system of differential equations (matematical model) includes the constructive parameters of the machine, the modification of which generates modifications of the kinematic parameters, which reach values ensuring an improved stability of the machine in the horizontal plane. Further more, the values of the soil reactions on the tyres of the rolling and copying systems can be adopted, using the known equations from the theory of motor vehicles, tractors or other digging machines. This allows also optimisation of the plane-parallel motion parameters, that is improvement of the qualitative parameters of the technological process carried out by the machine. By solving the system of equations the time related variation of the generalised coordinates was obtained, what allowed the plotting of the graphs of the roots harvesting machine mass centre trajectory, and also of the digging working element centre placed marginally, for various values of the travelling velocity.
The obtained results show that the trajectory of the roots harvesting machine is close to the harmonic one, as during the technological harvesting process the machine is permanently subjected to the modification of the value and orientation of the external disturbing forces. Initially the trajectory of the motion has a soft (uncontrolled) variation until a certain value, then, by (manual or by means of the automated row-wise control system) turning of the direction wheels the lateral and vertical reactions are redistributed and the motion takes place in the reversed sense.
The amplitude of these oscillating motions does not exceed 0.23 m. During the stabilised motion the frequency of these oscillations increases up top a certain value,of 0.6 Hz. For higher travelling velocities the intervals of the deviation from linear motion increase.