Solid State Phenomena Vol. 164

Abstract: Problem of ball bearing and roller bearing noise generation is important in present technology level, and its solution stands in front for a new machine designer. New materials of bearings create new problems of bearing noise generation, so research of noise and vibration generation mechanism in necessary. Problem of lubrication gives significant influence to vibration and noise generation in bearings, so in common task of bearing work vibration is quite complex and requires experimental verification of theoretical ideas. This paper is intended to cover noise generation mechanism of ceramic bearings in comparison to steel ones and evaluate influence of bearing lubricant with different properties. There are presented design of experimental workbenches, experimental research procedure and results from research. Experimental results material is presented graphically and numerically. Finally, conclusion on problem and results of experimental research are made.

Abstract: The paper is devoted to vibration monitoring of rotating tools in modern milling machines. Dynamic analysis of slender ball-end milling process was performed and dynamics of the controlled structure was described. Instantaneous change in the spindle speed is applied in order to reduce vibration level. The method of vibration monitoring by means of spindle speed optimal-linear control was developed and implemented with success. Vibration monitoring during high speed milling was performed on the basis of results of computer simulation. These results were verified during experimental investigation on the Alcera Gambin 120CR milling machine.

Abstract: This paper deals with modeling of a vibrational power generator and verification of a complex generator model for prediction of harvested power. The power generator is an electromagnetic device, which uses ambient energy of mechanical vibrations for generating useful electrical energy. This energy harvesting device constitutes a complex mechatronic system consisting of a resonance mechanism, electromechanical converter, power management (electronics and energy storage) and a powered device. When this system is placed in environment with sufficient mechanical vibration, the generator harvests energy and it can be used as autonomous source of electrical energy for powering of wireless sensors in remote applications. The verified simulation model of this device can provide a prediction of possible harvested power without any physical position of this device in a vibratory environment (only acceleration measurement is used as input).

Abstract: The paper deals with the numerical analysis of electromechanical systems. The system consists of a DC motor supplied from a half-wave, single phase, thyristor rectifier, and of a flexible rod fixed to the axis of armature. Discretization of rigid segments is used to model flexibility of the rod. The discrete structure is considered as a multibody system, i.e. as a single kinematical chain of rigid bodies connected by massless joints. Significant drift rotation is included in the rod model. Numerical integration is performed in order to predict behavior of the system. Two working conditions are tested: steady-state motion and transient braking of the system. The attention in the paper is concentrated on interactions between the mechanical and electrical systems.

Abstract: Vibrations of a mass are analyzed when the mass is connected with the support in succession of two elastic elements characterized by stiffness and damping coefficients. It is demonstrated that upon harmonic excitation of the mass and considering different values of stiffness and damping coefficients the system can respond differently in comparison to the case when the mass is connected to the support by means of single elastic element. Reduction of stiffness and damping coefficients of a pair of elements to a single one (as it is proposed in calculations of considered systems) can lead to incorrect results. This is confirmed by presented calculations and dependences.

Abstract: Theoretical analysis of vibrations of a system in which the mass is connected with the support in series of more than one elastic element had shown that there is possibility to provoke additional resonances. Condition of it is change of damping values of the system near the supposed resonance frequency defined calculations. Feed mechanism of cylindrical grinding machine of older design was researched from that point of view. The mechanism consists of chain of elastic elements in series connecting the wheelhead with the bed of machine. Large friction forces exist in the chains of elements and in the wheelhead ways. Analysis results are presented in the paper.

Abstract: The paper presents the sensitivity and stability margin analyses of the flexible rotor supported by active magnetic bearings (AMBs) with the robust optimal vibrations control. The modal representation of the rotor finite element model (FEM) is investigated. Then, the open-loop system of the AMBs flexible rotor is established and critical speed analysis due to variation of bearing stiffness is performed. For the open-loop setup, the non-collocation effect of displacement sensors and magnetic actuators due to control stability problem is considered. The frequency mode analysis of the collocation and non-collocation system is presented. Next, the -synthesis control of 4-DOF AMBs rotor is investigated. The design process of -controllers, which cover uncertainty design and performance shape by chosen weighting function is shortly described. Then, the sensitivity function is calculated and used to evaluate the AMBs rotor stability margin for the -control and the PID control. The performance of the -controller are verified in experimental tests.

Abstract: This paper is a continuation of earlier publications of the authors related to the analysis of mechatronic systems including piezoelectric materials used as sensors or actuators for stabilization and damping of mechanical vibration. It was demonstrated that only very accurate mathematical model of the system with the piezoelectric transducers and external electric circuit attached to a mechanical system like a beam or a shaft by a glue layer allows the engineers to design the system with required dynamic parameters. Geometrical and material parameters of all the components have to be taken into account because neglecting the influence of one of them results in erroneous analysis results [1-4]. The paper presents the improved mathematical model of the considered mechatronic system. The assumption of pure shear of the connection layer is rejected during modeling and deformation of the layer is taken into consideration. The purpose of the reported enhancement of the mathematical model of the considered mechatronic system is to improve accuracy of computational results.

Abstract: This paper deals with the analysis of mechatronic systems including piezoelectric materials used as sensors or actuators for stabilization and damping of mechanical vibration. This work presents the analysis of the flexural vibrating one-dimensional mechatronic system – a cantilever beam and the piezoelectric transducer bonded on the beam surface by means of a glue layer. The external RC circuit is connected to the transducer clamps. Dynamic equations of motion of the considered mechatronic system were written down using the discrete-continuous mathematical model, taking into consideration the influence of the connection layer and the external electric circuit. Dynamic flexibility of the mechatronic system was assigned on the basis of the approximate Galerkin method.

Abstract: Dynamics of two models (simplified and complex) of a small, typical vibrating table is considered in the paper. The table consists of vibrating plate and electrical vibrator, mounted in the central position of the plate, which excites the vibrations of the table. The coefficient of transversal stiffness of the spring has been determined on the basis of numerical simulation. The spring is an essential element of the system. The results of performed numerical simulations are presented in the graphical form.