On electronic educational resource to search for the most significant causes of self-excitation of oscillation of complex mechanical systems

Abstract

The modern approach to university education aims at developing an integrated system of competences: cultural, generic professional and professional, which characterize professional qualities of a graduate. In forming specifically professional competences the main role is played by taking special courses, performing laboratory works, doing practical assignments and writing the final qualification paper. In order to improve the quality and raise the teaching standards at the Nizhny Novgorod university named after N.I. Lobachevsky electronic educational resources are actively used. In this article, a part of an electronic educational resource is presented in the form of a program complex intended for finding the most significant reasons of oscillation self-excitation in complex mechanical systems. The program complex is written in C++ programming language using the visual programming environment Borland C++ Builder. The article describes physical approaches and search techniques for the most significant reasons of oscillation self-excitation in mechanical systems based on the concept of the geometrical scheme of connections and the theory of sensitivity. Understanding reasons for self-excitation of vibrations at the stage of the choice of idealization and the creation of computation schemes is important not only for coming up with adequate mathematical models, but also later for determining the strategy for creation at the early design stage of new equipment samples that have improved dynamic characteristics. Application of the described technique allows deeper understanding of the physical processes occurring in self-oscillating systems and helps make justified decisions when studying such complex objects. The algorithm realized in a program complex is the result of the analysis of a mathematical model of a certain class of multidimensional oscillating systems that can be viewed as several interconnected oscillators. It includes the following: forming matrices of masses, rigidity, dissipation, mutual and directed connections of the mathematical model that describes self-excitation of oscillations; creating the geometrical scheme of connections;  computing eigenfrequencies and forms of oscillations, finding potentially unstable forms of oscillations; computing sensitivity functions for cycles and negative friction; discovering sensitive cycles and negative friction and determining their share of contribution to work of active forces increasing the total energy of the system.

The problem of investigating reasons for oscillation self-excitation in the dynamic system of the PAZ automobile is considered as an example.