Pub Date : 2013-01-01DOI: 10.7494/MECH.2013.32.2.60
D. Grzybek
The ability to damp vibrations is important in many structures, in which trusses are one of the main elements. The increase of the damping of the truss vibrations is possible by passive means or by the use of an active vibration control system integrated with the structure of the truss. The control system can affect the truss structure by specially designed actuators, which generate active forces in appropriate nodes of the truss. Piezoelectrics can be used to build such actuators. The design of the control system encompasses the structure of the actuating active truss member, the spacing of active members inside the truss structure, the design of the control algorithm and the spacing of measurement sensors generating feedback signals. In this article, the application of the LQR algorithm to the node displacement control in a spatial truss has been presented. The spacing of active members in the truss structure on the basis of the force distribution in the truss members has been suggested.
{"title":"LQR CONTROL OF THE NODAL DISPLACEMENTS IN A SPATIAL TRUSS WITH ACTIVE PIEZOELECTRIC MEMBERS","authors":"D. Grzybek","doi":"10.7494/MECH.2013.32.2.60","DOIUrl":"https://doi.org/10.7494/MECH.2013.32.2.60","url":null,"abstract":"The ability to damp vibrations is important in many structures, in which trusses are one of the main elements. The increase of the damping of the truss vibrations is possible by passive means or by the use of an active vibration control system integrated with the structure of the truss. The control system can affect the truss structure by specially designed actuators, which generate active forces in appropriate nodes of the truss. Piezoelectrics can be used to build such actuators. The design of the control system encompasses the structure of the actuating active truss member, the spacing of active members inside the truss structure, the design of the control algorithm and the spacing of measurement sensors generating feedback signals. In this article, the application of the LQR algorithm to the node displacement control in a spatial truss has been presented. The spacing of active members in the truss structure on the basis of the force distribution in the truss members has been suggested.","PeriodicalId":38333,"journal":{"name":"International Journal of Mechanics and Control","volume":"9 1","pages":"60"},"PeriodicalIF":0.0,"publicationDate":"2013-01-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"89635515","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2013-01-01DOI: 10.7494/MECH.2013.32.2.52
O. Gagrica, W. Kling, T. Uhl
Low voltage (LV) residential grids are generally not designed for high penetration of photovoltaic (PV) distributed generation. Maximization of PV output is not only opposed by solar energy intermittency, but also by grid impacts in form of reverse power flow and overvoltage. More intelligent control of PV inverters is required to balance the voltage requirements of the grid and maximum energy yield wanted by the end user. This paper discusses how micro-inverter topology could be utilized to handle overvoltage problem and avoid power output losses by applying an innovative control method. Control is realized as partial generation shedding at PV module level which is an optimized alternative comparing to conventional, entire PV array tripping in the event of overvoltage.
{"title":"Control of micro-inverters as an overvoltage prevention method under high PV penetration","authors":"O. Gagrica, W. Kling, T. Uhl","doi":"10.7494/MECH.2013.32.2.52","DOIUrl":"https://doi.org/10.7494/MECH.2013.32.2.52","url":null,"abstract":"Low voltage (LV) residential grids are generally not designed for high penetration of photovoltaic (PV) distributed generation. Maximization of PV output is not only opposed by solar energy intermittency, but also by grid impacts in form of reverse power flow and overvoltage. More intelligent control of PV inverters is required to balance the voltage requirements of the grid and maximum energy yield wanted by the end user. This paper discusses how micro-inverter topology could be utilized to handle overvoltage problem and avoid power output losses by applying an innovative control method. Control is realized as partial generation shedding at PV module level which is an optimized alternative comparing to conventional, entire PV array tripping in the event of overvoltage.","PeriodicalId":38333,"journal":{"name":"International Journal of Mechanics and Control","volume":"1 1","pages":"52-59"},"PeriodicalIF":0.0,"publicationDate":"2013-01-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"79824853","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2013-01-01DOI: 10.7494/MECH.2013.32.4.143
Anna Perduta
This paper describes enhancing mesh adaptation capabilities of GetFEM++ library. GetFEM++ is a versetile software package in C++ for implementing FEM based solvers for partial differential equations. Although GetFEM++ offers a wide range of mathematic tools for model descripion and discretization, it does only provide basic mesh refinement facilities. To enhance GetFEM++ capabilities, a mesh adaptation package MAdLib is used. The paper discusses basic requirements for mesh adaptation packages and presents MAdLib basic usage. The paper discusses implementation issues related to integration of both libraries. Examples illustrate capabilities of mesh adapation package and FEM framework extended by mesh adaptation facilities.
{"title":"ENHANCING MESH ADAPTATION CAPABILITIES OF GetFEM++ “FEM ENGINE” WITH MAdLib LIBRARY","authors":"Anna Perduta","doi":"10.7494/MECH.2013.32.4.143","DOIUrl":"https://doi.org/10.7494/MECH.2013.32.4.143","url":null,"abstract":"This paper describes enhancing mesh adaptation capabilities of GetFEM++ library. GetFEM++ is a versetile software package in C++ for implementing FEM based solvers for partial differential equations. Although GetFEM++ offers a wide range of mathematic tools for model descripion and discretization, it does only provide basic mesh refinement facilities. To enhance GetFEM++ capabilities, a mesh adaptation package MAdLib is used. The paper discusses basic requirements for mesh adaptation packages and presents MAdLib basic usage. The paper discusses implementation issues related to integration of both libraries. Examples illustrate capabilities of mesh adapation package and FEM framework extended by mesh adaptation facilities.","PeriodicalId":38333,"journal":{"name":"International Journal of Mechanics and Control","volume":"228 1","pages":"143"},"PeriodicalIF":0.0,"publicationDate":"2013-01-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"74469863","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2013-01-01DOI: 10.7494/MECH.2013.32.3.110
J. Tuma, M. Mahdal, P. Šuránek
This article deals with the simulation of the active vibration control of a cantilever beam. For these purposes, a lumped parameter model has been developed and the simplest controller has been designed to ensure the structural stability of the control loop. The controller is of a proportional velocity feedback type. The control loop can also be stable in the case of a very small inherent damping of the cantilever beam. The lumped-parameter model is based on the Euler-Bernoulli beam theory. The developed tools can be used to simulate the collocated and non-collocated active vibration control. Since this article is intended to study the behaviour of a non-collocated control system of the transducer is sensing the vibration of the free end of the beam, while the actuator force acts near the fixed end.
{"title":"Simulation study of the non-collocated control of a cantilever beam","authors":"J. Tuma, M. Mahdal, P. Šuránek","doi":"10.7494/MECH.2013.32.3.110","DOIUrl":"https://doi.org/10.7494/MECH.2013.32.3.110","url":null,"abstract":"This article deals with the simulation of the active vibration control of a cantilever beam. For these purposes, a lumped parameter model has been developed and the simplest controller has been designed to ensure the structural stability of the control loop. The controller is of a proportional velocity feedback type. The control loop can also be stable in the case of a very small inherent damping of the cantilever beam. The lumped-parameter model is based on the Euler-Bernoulli beam theory. The developed tools can be used to simulate the collocated and non-collocated active vibration control. Since this article is intended to study the behaviour of a non-collocated control system of the transducer is sensing the vibration of the free end of the beam, while the actuator force acts near the fixed end.","PeriodicalId":38333,"journal":{"name":"International Journal of Mechanics and Control","volume":"45 1","pages":"110"},"PeriodicalIF":0.0,"publicationDate":"2013-01-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"74062961","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2013-01-01DOI: 10.7494/MECH.2013.32.2.69
M. Manka, Ł. Ambroziński, Tadeusz Uhl
In recent years an intensive research activity into the application of guided waves (GWs) for structural health monitoring (SHM) can be observed. For instance, Lamb waves (LWs) have shown a great potential in monitoring of thin, planar structures. However, due to the dispersive and multimodal nature of the LWs, their snapshots can consist of many pulses even for an intact structure, which makes damage detection very complex. Moreover, small PZT transducers, most commonly used in SHM systems, act normally as omni-directional wave sources; therefore, dense or sparse transducers networks are required for damage localization. Some of the above-mentioned drawbacks of single PZT emitters and sensors can be overcome using interdigital transducers (IDT) designed to excite and sense a single, selected mode. The mode-tuning is performed by changing the span of finger electrodes to match the wavelength of the excited mode for the selected frequency. An IDT is a directional source, therefore, it generates a wave steered to the direction perpendicular to the electrodes. The width of the excited main lobe can be determined by the length of the electrodes. Since many parameters of the IDTs influence the LWs propagation, techniques for the simulation of the wave excitation and propagation are needed. In the paper, numerical tools for the computer aided design and virtual prototyping of the IDTs are presented. The simulation technique is based on the frequency-dependent transfer function of the structure, and due to its computational efficiency it can be used for fast testing of IDTs’ performance and for preliminary transducer design for further finite element simulations, and prototyping.
{"title":"Computer-aided prototyping of interdigital transducers for the structural health monitoring of planar structures","authors":"M. Manka, Ł. Ambroziński, Tadeusz Uhl","doi":"10.7494/MECH.2013.32.2.69","DOIUrl":"https://doi.org/10.7494/MECH.2013.32.2.69","url":null,"abstract":"In recent years an intensive research activity into the application of guided waves (GWs) for structural health monitoring (SHM) can be observed. For instance, Lamb waves (LWs) have shown a great potential in monitoring of thin, planar structures. However, due to the dispersive and multimodal nature of the LWs, their snapshots can consist of many pulses even for an intact structure, which makes damage detection very complex. Moreover, small PZT transducers, most commonly used in SHM systems, act normally as omni-directional wave sources; therefore, dense or sparse transducers networks are required for damage localization. Some of the above-mentioned drawbacks of single PZT emitters and sensors can be overcome using interdigital transducers (IDT) designed to excite and sense a single, selected mode. The mode-tuning is performed by changing the span of finger electrodes to match the wavelength of the excited mode for the selected frequency. An IDT is a directional source, therefore, it generates a wave steered to the direction perpendicular to the electrodes. The width of the excited main lobe can be determined by the length of the electrodes. Since many parameters of the IDTs influence the LWs propagation, techniques for the simulation of the wave excitation and propagation are needed. In the paper, numerical tools for the computer aided design and virtual prototyping of the IDTs are presented. The simulation technique is based on the frequency-dependent transfer function of the structure, and due to its computational efficiency it can be used for fast testing of IDTs’ performance and for preliminary transducer design for further finite element simulations, and prototyping.","PeriodicalId":38333,"journal":{"name":"International Journal of Mechanics and Control","volume":"102 1","pages":"69"},"PeriodicalIF":0.0,"publicationDate":"2013-01-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"88027519","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2012-09-22DOI: 10.7494/MECH.2012.31.2.72
D. Jasińska, M. Janus-Michalska, J. Smardzewski
This paper presents numerical study of deformation and stresses in seat skeleton elements subject to static and dynamic pressure loads. Elastic skeleton made of polyamide or elastomer is taken as an example of a seat material. Auxetic type of seat structure ensures the reduction of real contact stresses between human body and seat, making it more comfortable than typical. FEM analysis is performed using ABAQUS system. Numerical calculations are carried out to determine the nonlinear stiffness characteristics of seat springs. The study makes possible the selection of material and structural topology fulfilling design constraints and additional recommendations concerning structural flexibility, stability and optimal reduction of contact stresses. This paper presents an application of the problem.
{"title":"A STUDY ON THE DESIGN OF AUXETIC STRUCTURE OF SEAT SKELETON","authors":"D. Jasińska, M. Janus-Michalska, J. Smardzewski","doi":"10.7494/MECH.2012.31.2.72","DOIUrl":"https://doi.org/10.7494/MECH.2012.31.2.72","url":null,"abstract":"This paper presents numerical study of deformation and stresses in seat skeleton elements subject to static and dynamic pressure loads. Elastic skeleton made of polyamide or elastomer is taken as an example of a seat material. Auxetic type of seat structure ensures the reduction of real contact stresses between human body and seat, making it more comfortable than typical. FEM analysis is performed using ABAQUS system. Numerical calculations are carried out to determine the nonlinear stiffness characteristics of seat springs. The study makes possible the selection of material and structural topology fulfilling design constraints and additional recommendations concerning structural flexibility, stability and optimal reduction of contact stresses. This paper presents an application of the problem.","PeriodicalId":38333,"journal":{"name":"International Journal of Mechanics and Control","volume":"15 1","pages":"72-76"},"PeriodicalIF":0.0,"publicationDate":"2012-09-22","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"73981059","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2012-09-22DOI: 10.7494/MECH.2012.31.2.77
M. Jankowska, G. Sypniewska-Kamińska
In this paper the transient bioheat transfer problem given by the one-dimensional Pennes equation with mixed boundary conditions is considered. The model assumes the heat transfer between the skin and its surroundings in the case of a natural and forced convection. For computations the interval finite difference method of Crank- -Nicolson type together with the floating-point interval arithmetic is used. In this way, uncertain geometric and thermophysical parameters can be represented in the form of intervals as well as the resultant temperature distribution over time.
{"title":"AN INTERVAL FINITE DIFFERENCE METHOD FOR THE BIOHEAT TRANSFER PROBLEM DESCRIBED BY THE PENNES EQUATION WITH UNCERTAIN PARAMETERS","authors":"M. Jankowska, G. Sypniewska-Kamińska","doi":"10.7494/MECH.2012.31.2.77","DOIUrl":"https://doi.org/10.7494/MECH.2012.31.2.77","url":null,"abstract":"In this paper the transient bioheat transfer problem given by the one-dimensional Pennes equation with mixed boundary conditions is considered. The model assumes the heat transfer between the skin and its surroundings in the case of a natural and forced convection. For computations the interval finite difference method of Crank- -Nicolson type together with the floating-point interval arithmetic is used. In this way, uncertain geometric and thermophysical parameters can be represented in the form of intervals as well as the resultant temperature distribution over time.","PeriodicalId":38333,"journal":{"name":"International Journal of Mechanics and Control","volume":"1 1","pages":"77-84"},"PeriodicalIF":0.0,"publicationDate":"2012-09-22","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"89580703","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2012-09-22DOI: 10.7494/MECH.2012.31.2.63
A. Czerwiński, J. Łuczko
This paper is concerned with the analysis ofa model describing the vibrations of simply supported straight pipes conveying periodically pulsating fluid. The vibrations of the hydraulic system are described by a fourth-order partial diflerential equation, with the inclusion of geometrical non-linearities. Through the application of the Galerkin method, the non-linear problem is reduced to the solution of’/our ordinary differential equations. The influence of several significant parameters of the model on the rms value of velocity is investigated. The possibility ofexciting sub-harmonic and chaotic excitations at certain intervals ofcxcitation frequency andflow velocity is presented.
{"title":"Vibrations of steel pipes and flexible hoses induced by periodically variable fluid flow","authors":"A. Czerwiński, J. Łuczko","doi":"10.7494/MECH.2012.31.2.63","DOIUrl":"https://doi.org/10.7494/MECH.2012.31.2.63","url":null,"abstract":"This paper is concerned with the analysis ofa model describing the vibrations of simply supported straight pipes conveying periodically pulsating fluid. The vibrations of the hydraulic system are described by a fourth-order partial diflerential equation, with the inclusion of geometrical non-linearities. Through the application of the Galerkin method, the non-linear problem is reduced to the solution of’/our ordinary differential equations. The influence of several significant parameters of the model on the rms value of velocity is investigated. The possibility ofexciting sub-harmonic and chaotic excitations at certain intervals ofcxcitation frequency andflow velocity is presented.","PeriodicalId":38333,"journal":{"name":"International Journal of Mechanics and Control","volume":"4 1","pages":"63-71"},"PeriodicalIF":0.0,"publicationDate":"2012-09-22","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"80502033","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2012-09-22DOI: 10.7494/MECH.2012.31.2.85
J. Snamina
This study briefly outlines the structure of the test facility for investigating the behaviour of a sandwich plate filled with magnetorheological (MR) fluid. The plate has two outer layers made of aluminium and the space between them is filled with MR fluid. The test facility is engineered within the framework of the research project focused on vibration reduction in beams and plates using MR fluids. The paper outlines the design of the test facility and the measurement equipment. Measurement data are summarised, including the free and forced vibration of the plate.
{"title":"FACILITY FOR INVESTIGATING THE VIBRATION OF THE PLATE WITH MAGNETORHEOLOGICAL FLUID","authors":"J. Snamina","doi":"10.7494/MECH.2012.31.2.85","DOIUrl":"https://doi.org/10.7494/MECH.2012.31.2.85","url":null,"abstract":"This study briefly outlines the structure of the test facility for investigating the behaviour of a sandwich plate filled with magnetorheological (MR) fluid. The plate has two outer layers made of aluminium and the space between them is filled with MR fluid. The test facility is engineered within the framework of the research project focused on vibration reduction in beams and plates using MR fluids. The paper outlines the design of the test facility and the measurement equipment. Measurement data are summarised, including the free and forced vibration of the plate.","PeriodicalId":38333,"journal":{"name":"International Journal of Mechanics and Control","volume":"9 1","pages":"85-89"},"PeriodicalIF":0.0,"publicationDate":"2012-09-22","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"76173366","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2012-09-22DOI: 10.7494/MECH.2012.31.2.90
A. Stręk
This paper presents a comprehensive, systematic approach on experimental investigations of structure and mechanical properties of metal foams. Based on a thorough state of the art study, the existing solutions have been synthesised with recent developments in the discussed field to become a proposition of a possibly complete methodology for observation and testing of cellular metals. Material properties acquired in the described manners can constitute reliable reference result base e.g. for identification and verification of failure criteria. This paper describes sample preparation procedures and next discusses techniques which enable one to characterise foam structure. There are also presented procedures for determining strength limits in different load cases: uniaxial tension or compression, shear and torsion as well as multiaxial states. The tests are discussed in terms of their specific application to study cellular metallic materials.
{"title":"Methodology for experimental investigations of metal foams and their mechanical properties","authors":"A. Stręk","doi":"10.7494/MECH.2012.31.2.90","DOIUrl":"https://doi.org/10.7494/MECH.2012.31.2.90","url":null,"abstract":"This paper presents a comprehensive, systematic approach on experimental investigations of structure and mechanical properties of metal foams. Based on a thorough state of the art study, the existing solutions have been synthesised with recent developments in the discussed field to become a proposition of a possibly complete methodology for observation and testing of cellular metals. Material properties acquired in the described manners can constitute reliable reference result base e.g. for identification and verification of failure criteria. This paper describes sample preparation procedures and next discusses techniques which enable one to characterise foam structure. There are also presented procedures for determining strength limits in different load cases: uniaxial tension or compression, shear and torsion as well as multiaxial states. The tests are discussed in terms of their specific application to study cellular metallic materials.","PeriodicalId":38333,"journal":{"name":"International Journal of Mechanics and Control","volume":"21 1","pages":"90-96"},"PeriodicalIF":0.0,"publicationDate":"2012-09-22","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"82626337","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
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