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A problem of electro-acoustic plant identification for active noise control is discussed. It is assumed that data from identification experiment are contaminated by a primary noise that should be attenuated later. Three examples of such a noise are considered: sine (discrete spectrum), noise generated by a motor (narrowband time-varying spectrum) and broadband noise (pseudorandom). It is shown that...
Active control of vibration suppression of a circular fluid-loaded plate is analytically studied. The purpose of this theoretical work is to present a general model of a planar vibrating structure located in a finite baffle and interacted with fluid as well as its time response on harmonic excitation when a control strategy is applied. The structure under study is a vibrating circular plate of radius...
Modern structures are light and compliance. Therefore, they are strongly influenced by external and internal perturbations. To reduce the structure vibrations the active vibration controls systems are designed. When active control of flexible structures is sought, three items must be individually and simultaneously considered. 1) The creation of reduced-order models. 2) Placement of sensors and actuators...
The purpose of this work is to present methods for designing semiactive vibration systems, which include mathematical models of vibrating structures. Thus aspects of model building, identification and verification are described in the paper as well as determination of the performance indices, choice of the damping technique, shock absorber modeling and algorithm selection. The article presents a semiactive...
The paper is concerned with linearized characterization of a magnetorheological fluid (MR) damper. Two basic damping models, the equivalent viscous damping and the complex modulus, were used to linearize MR damper behaviour. The relationships between the parameters of the damping models were investigated experimentally in terms of the current applied to the damper coil and the maximal piston velocity.
The paper presents nonlinear Model Predictive Control algorithm applied to full-active four-dimensional magnetic bearing system MBC500 being produced by Magnetic Moments, USA. The system is nonlinear due to the measurement units and the current amplifiers (actuators). Nonlinear model of the system has been established basing on the phenomenological description with parameters identified. The model...
The paper presents vibroacoustic tests of power transformers with regard to active reduction of their noise. Basic sources of vibroacoustic energy are determined and a system of active reduction of noise (ANC) emitted by power transformers, developed by CIOP-PIB, is presented. Moreover, the results of preliminary tests of the system in real conditions are presented.
The physical value of a backlash in a kinematic pair of a mechanical system can be determined using a number of methods; still the problem is considered to be difficult. The identification may involve employing a modelling function, which allows also finding out about other properties of a given mechanical system. A modelling function constitutes a mathematical model for the relationship between the...
The paper deals with Virtual Distortion Method (VDM) in frequency domain. VDM method is addressed to problems, where steady state response can be the base of the dynamical analysis. The VDM methodology allows fast modification of the original structures without need of modifications of their stiffness, damping and mass matrices. The present work contains the methodology of the new approach, some numerical...
Problem of estimation of damping parameters of a structure by analysis of wave propagation in the structure, is addressed. The task is formulated for a cantilever multi-layer beam undergoing random excitation. Since different methods of solution of the problem have been developed the need arises to discuss and compare results obtained by means of the latter ones. Stress is laid on Inhomogenous Wave...
Pulsation forming of metallic materials (also referred to as stresscycling) is a novel forging method based on the application of a variable pulsation frequency during the metal forming process. This paper presents some new results obtained after pulsation forming of steel grade Cr18Ni1O. The experimental works suggested that the value of summary deformation of 25% (at the pulsation frequency of 30...
In the paper the dynamic behaviour of the systems composed of active human body models (AHBM) and passive isolation systems (VIS) subjected to sinusoidal and random excitations was discussed. The two active human body biomechanical models ("back-off" and "back-on ") obtained several years ago by the first author of the presented paper can be considered as active, linear, stable,...
Active elements in power machine may be controlled with a signals from diagnostic system to stabilize it's operating in a case of emergency work. It needs to identify specific indicators for particular classes of defects. The paper presents possibilities to define such indicators for transverse crack occurring in the rotor of 200 MW turbo-set. The investigations were performed in the way of computer...
The work presents an algorithm for active control of vibrations of a three-axis gyroscopic platform during pre-programmed and stabilised operation on board of a flying object. The considerations focus on disturbances resulting from the flying object manoeuvres and short-duration pulses of external forces under the conditions of friction in the bearings and non-linear platform operation range.
Sliding mode control of a single-axis type bang-bang megnetic bearing actuator is reported in this paper. The two electromagnets are driven by switching between a positive and a negative constant voltage. Sliding mode control using these switching surfaces in turn is shown to be possible. The sliding mode turns out to take place in a subregion of state space defined by s1(x)s2(x) lessim 0 rather than...
The paper presents a method of optimal reduction of vibrations of a one-or two-axis gyroscopic platform mounted on board of a flying object. The included algorithm allows one to select optimal parameters of the platform as well as optimal coefficients of the controller, and, in consequence, minimise the deviations from the preset motion. The investigations focused on the platform operation affected...
The application of vibro-acoustic analysis methods in naval technology has been presented in the paper. This element of Base Diagnosing System (BDS) is accepted and used in the ships, which are powered by the COGAG power plant. The paper presents investigations of permissible in-service unbalance and appropriate assemblage of turbine rotors on the basis of selected vibroacoustic parameters, and finally...
It has been long recognized that the inertia and compressibility of the fluid have a significant effect on the dynamic behavior of Magneto-Rheological (MR) dampers. Previous studies have revealed the nature of the effect through the analysis of a comprehensive, albeit fairly complex, state-space model of the MR monotube damper hydraulies. The present paper outlines a simpler model of the damper and...
The study concerns 2 DOF and 3 DOF pitch-plane models of a semi-active vehicle suspension comprising magnetorheological (MR) dampers. The 2 DOF pitch-plane model with two independent spring - MR damper suspension sets enables us to study bounce and pitch motions of the suspended body. The 3 DOF pitch-plane model takes into account also a model of driver's seat and for this reason the third spring...
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