Synthetic Impedance Circuits in Semi-Passive Vibration Control with Piezo-Ceramics - Efficiency and Limitations

Electrical circuits that represent complex impedance connected to the plates of piezo element affect the frequency response function of compound electromechanical systems. The external network consisting of inductance results in absorbing a certain frequency of vibrations. The performance can significantly be increased using negative capacitance. All the negative impedance elements are achievable via semi-passive way with the use of an electronic gyrator realized by operational amplifiers that require power supply. Its performance is limited due to the maximum voltage operational amplifiers can produce. The higher excitation forces require higher output voltages of amplifiers. The aim of the paper is to present the relation between the required voltage on synthetic impedance and force excitation in 1DOF vibrating system regarding parameters of piezo element and mechanical system for absorbing case. (© 2005 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim)     

Impedance Losses in Negative Capacitance Circuits for Semi-Passive Vibration Control with Piezo-Ceramics

Damping or absorbing effect in vibration control applications with piezo elements may be customized by an external impedance shunt branch connected to the plates of the piezo element. The negative capacitance present in the shunt significantly improves the damping and absorbing performance of such systems. The circuit is built up of an electronic gyrator realized by the operational amplifier, which is in reality not the ideal element. Therefore the performance of the proposed systems is limited, concerning the maximum voltages and currents at which the operational amplifiers can operate. In the paper, the finite gain of the operational amplifier, together with the loss impedances and the feedback gain factor is studied. The influence of the certain imperfections in the design of the electronic gyrator is based on 1DOF mechanical oscillator, with a piezo stack. (© 2006 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim)     

Modeling of a vehicle seat suspension system with pneumatic spring and viscous dampers

The paper contains physical and mathematical model of the passive system of seat suspension, used in trucks and buses. Spring force in this system is performed by air spring, whereas damping force is generated by two viscous dampers. Based on the experimental research of characteristic parts of the suspension system, the parameters of mathematical model are determined. Both results of computer simulations and experiments are presented as power spectral density of acceleration courses, measured on seat, in comparison with courses measured on excitation platform in laboratory. Transmissibility of real system and its model are also presented in the paper. (© 2008 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim)     

Poly-optimization: a paradigm in engineering design in mechatronics

The paper deals with the Engineering Design that is a general methodology of a design process. It is assumed that a designer has to solve a design task as an inverse problem in an iterative way. After each iteration, a decision should be taken on the information that is called a centre of integration in a systematic design system. For this purpose, poly-optimal solutions may be used. The poly-optimization is presented and contrasted against the Multi Attribute Decision Making, and a set of the poly-optimal solutions is defined. Then Mechatronics is defined and its characteristics given, to prove that mechatronic design process vitally needs CAD tools. Three examples are quoted to demonstrate a key role of the poly-optimization in the mechatronic design.     

Control design of the vibration reduction systems

The paper deals with an original control algorithm for semi-active and active suspension that are often used in automotive systems. The developed procedure assists in finding the structure of control system, which consists of the primary controller and calculates the desired active force. Then the desired force has to be approximately achieved by the semi-active or active element with calculated input signal using the inverse model. (© 2015 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim)     

Implementation of genetic algorithm for controlling the electromagnetic motor

The paper deals with the problem of implementing a genetic algorithm (GA) to calculate a pareto-optimal function of voltage in time-domain powering solenoids, used to control a linear electromagnetic motor (e.m.). The method proposed assumes minimising two criteria: the time of motion of the linear electromagnetic motor and the energy input. The results have been obtained for a set position with a narrow range of power supply. The work of electromagnetic motor is based on electromagnetic repulsion. (© 2009 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim)     

Optimisation of pneumatic circuit aimed at improving the vibro-isolation properties of seat suspension

The object of a numerical simulation and optimisation is the seat with a visco-elastic passive suspension, with improved vibro-isolation properties by means the multi-criteria optimisation. Basing on the verified passive seat suspension model, a modification of the pneumatic circuit in order to help the working machines operators against vibration is considered. The root mean square (RMS) acceleration measured at the seat and the maximum relative displacement of the seat suspension are minimised as the chosen vibro-isolation criteria. (© 2009 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim)     

Influence of the absorption coefficient and material boundaries distribution on the acoustic pressure in the room with rigid walls

In the paper a problem of distribution of an acoustic absorption materials on room's boundaries has been presented. A room with a harmonic sound source inside has been considered. A pressure distribution was described using modal analysis assumptions. Usually, most of real rooms have enough high boundaries' impedance (absorption coefficient), therefore the modal coupling can be neglected. Hence, pressure can be represented by a sum over a set of room's eigenfunctions and time components i.e. the modal amplitudes. Amplitudes are dependent of eigenfrequencies ω_n, damping coefficients r_n and a source function Q_n. Conducting analysis of the modal amplitude function, in relation to ω_n and r_n, an optimal acoustical damping can be obtained. Taking triple criteria objective function into consideration, absorbtion material optimal distribution on boundaries has been found. In order to find minimum of the objective function genetic algorithm was used. (© 2008 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim)     

Voltage amplification transfer function analysis of the operational amplifier in the negative capacitance circuits for vibration control with piezoceramics

Piezo elements due to their ability of converting mechanical energy into electrical energy and vice versa can be found in numerous mechanical vibration damping and absorbing applications. A desired effect may be customized by an external impedance shunt branch connected to the plates of the piezo element. The negative capacitance connected in serial with the passive shunt significantly improves the damping and absorbing performance of such systems. Negative capacitance circuit is built of an impedance converter realized by the operational amplifier. Since the amplifiers are not the ideal elements, the performance of the proposed systems is limited. This is due to the maximum voltages and currents that the operational amplifiers are able to generate. This effect causes instabilities and limits the operational area of the impedance converter. In the paper, the amplification transfer function of the non-ideal operational amplifier in the negative impedance converter is studied, and the necessary modification with the additional passive elements is proposed. The influence of the certain imperfections in the design, and its improvements are shown on the system consisting of the 1DOF mechanical oscillator, and a shunted piezo element. (© 2008 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim)     

Localization in Nonlinear Mistuned Systems with Cyclic Symmetry

In forced systems with cyclic symmetry localization can occur due toparameter uncertainties. Often, Monte-Carlo simulations are used to findregions, where the system response is sensitive to parameteruncertainties. These simulations require a large computation time.Therefore, an approximate method to calculate the envelopes of thefrequency response functions is developed in this paper. An example of anonlinear system with cyclic symmetry is a bladed disk assembly withfriction dampers. Friction dampers can be installed underneath the bladeplatforms of turbine blades. Due to dry friction and the relative motionbetween blades and dampers, energy is dissipated, which results in areduction of blade vibration amplitudes. By optimizing the mass of thefriction dampers, the best damping effects are obtained, which lead toan increase in the reliability of the turbine. In this paper, thecalculated response of a mistuned bladed disk assembly with frictiondampers is discussed. An approximate method is developed to calculatethe envelopes of the corresponding frequency response function forstatistically varying eigenfrequencies of the blades. Regions wherelocalization can occur with a high probability, are calculated by thismethod.