STABILITY OF VIBRATIONS OF THE TRACTOR AS A TWO-MASS MODEL WITH TWO NONLINEARITIES OF THE TYPE OF DRY FRICTION IN RESONANCE MODES

Abstract

Purpose of the study is to assess the possibility of calculating the stability of tractor oscillations as a system with nonlinearities such as dry friction due to the inverse problem. Research methods. The methodological basis of the work is the generalization and analysis of known scientific results regarding the dynamics of two-mass systems in resonance modes and the use of a systematic approach. The analytical method and comparative analysis were used to form a scientific problem, determine the goal and formulate the research objectives. When creating empirical models, the main provisions of the theory of stability of systems, methodology of system analysis and research of operations were used. The results of the study. Oscillations of the system with harmonic excitation by its base are considered (for example, the movement of a tractor on an uneven supporting surface). Oscillations of this system are described by nonlinear differential equations. To solve this equation, instead of friction dampers with friction forces, linear dampers with corresponding drag coefficients are included in the system. By solving the obtained system of linear inhomogeneous differential equations for the steady-state mode of oscillation, the amplitudes of oscillations of masses and deformation of springs with certain stiffness are determined. To clarify the effect of friction forces on mass oscillations in resonance modes, the obtained expressions were analyzed. A diagram of stability of mass oscillations in resonance modes is obtained. Conclusions. It has been established that if the coefficients of relative friction have such values that the point that is determined by them lies within the region bounded by segments 1-2 and 2-3 and coordinate axes, then during oscillations in the low-frequency resonance mode, the friction forces do not limit the increase in amplitudes fluctuations of masses, but only reduce the rate of their growth. If the point, which is determined by the coefficients of relative friction, lies in the region 1-1'-2'-3 '3-2-1, then the springs have intermittent deformation, that is, during the period of oscillation, one mass of the system has stops relative to another mass, or the last has stops relative to the support surface, or both masses move part of the period as a whole with the support surface. At resonance with a high frequency, the friction forces limit the amplitudes of mass oscillations if the coefficients of relative friction have such values that the point that is determined by them does not lie in the region bounded by segments 4-5 and 5-6 and the coordinate axes. Sections 4-5 and 5-6 define the boundaries of vibration stability at resonance (lines of critical ratios of the coefficients of relative friction).