Research On Coupling Dynamics Of Motor-Elastic Linkage Mechanism System

With mechanical systems being continually developed to become flexible, high-speed, lightweight and high accurate, the demand for elastodynamic properties of mechanical systems becomes much higher. As the significant improvements of mechanical properties, the advanced composite materials, which have high strength-to-weight ratios and damping properties of advanced composite materials that are superior to the conventional metals, are now used in electromechanical systems and show a promising future for broader rang of application. However, some exceptional phenomena often emerge in the operation of these mechanical systems. The main reasons are that the nonlinear dynamic vibration and the coupling dynamics of the mechanical systems have not been studied deeply. These theoretical problems concerned have become the bottleneck that restricts this new type of composite materials to be popularized and applied in electromechanical systems. So the researches on the nonlinear dynamic vibration and the coupling dynamics of the mechanical systems are more and more important. The researchful purpose of this dissertation is to solve some problems of both the nonlinear dynamic vibration and the coupling dynamics of a motor– elastic linkage mechanism system. The major contents of this dissertation are as follows:The coupling dynamic model of the system are established by the finite element methods (FEM). Firstly, based on the air-gap field of non-uniform airspace of three-phase AC motor caused by the vibration eccentricity of rotor and the relation of electromechanical coupling of its actual running state, the function of air-gap magnetic field energy is introduced and the motor element was established, which defined the transverse vibration and torsional vibration of the motor as its nodal displacement. Secondly, according to the characteristics of metal and 3-dimentional braided composite materials, both the metal beem element and the 3-dimentional braided composite material beem element are obtained. Then based on the motor element, the metal beem element and the 3-dimentional braided composite material beem element, the coupling dynamic equations of the system are established by the finite element methods. The dynamic equations discover the actual relation between macro dynamic characters of the system and electromagnetic parameters of drive motors, material parameters and structural parameters and show the dynamic properties of the system that have not been discovered before. The equations are the base to deeply study the intrinsical relation between macro dynamic characters of the motor–driven elastic linkage mechanism system and electromagnetic parameters of drive motors, material parameters and structural parameters.Using the method of multiple scales, the coupling mechanism of the parameter excitation and the forced vibration of the three-phase AC motor–elastic linkage mechanism system and the conditions under which the parametric resonance and the forced resonance of the system take place are studied deeply. Some helpful conclusions are obtained. The studies show that the nonlinear electromagnetic parameter excitation and the outer excitation exist in the three-phase AC motor– elastic linkage mechanism system, that the electromagnetic parameter excitation is caused by the air-gap field of non-uniform airspace of three-phase AC motor due to the eccentricity of rotor and the outer excitation is caused by the self-excited inertial forces of the system, and that the coupling phenomenon of both the parametric vibration and the forced vibration of the system may take place subjected to both the electromagnetic parameter excitation and the outer excitation.Based on the method of perturbation and the method of numerical analysis, the method of iterative modal superposition-multiple scales is derived which is not only used to deeply study the dynamic properties of the motor– elastic linkage mechanism system but also to calculate highly accurate dynamic responses of the system. Firstly, the first-order approximate solution of the dynamic responses of the system is calculated by the method of multiple scales. Then taken the first-order approximate solution as the initialization of the generalized coordinate of the system, the accurate solution of the dynamic responses of the system is obtained by the method of iterative modal superposition, and the precision of the the solution can be controlled by a tiny positive number which is supposed beforehand.Using the method of multiple scales, the resonances of the motor– elastic linkage mechanism system are studied, such as the primary resonance and the sub-harmonic resonance of the system subjected to the electromagnetic force, the super-harmonic resonance of the system subjected to the self-excited inertial forces of the system, the combination resonance and the multiple resonance of the system subjected to both the electromagnetic force and the self-excited inertial forces of the system, the motive stabity of the system, and so on. The expressions of the first-order approximate solution of the resonance responses of the system are given. An algorithm for determining the stability of resonance is derived. The effects of the parameters of drive motor on the dynamic properties of system are analyzed.By developing an experimental set-up, which can availably test the dynamic responses of the links of the motor–elastic linkage mechanism system, the experimental researches into the dynamic properties of the system are made. The results of theoretical studies in this dissertation are verified by the results of experimental researches.