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MECHANICS AND CONTROL

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Mechanics and Control wydawane w latach 2010-2016, wcześniej pod tytułem Mechanics ukazywało się w latach 2005-2009.

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Now showing 1 - 10 of 171
  • thumbnail.journal.alt
    Item type:Article, Access status: Open Access ,
    Test bed for simulation of magnetic field measurements of low earth orbit satellites
    (Wydawnictwa AGH, 2015) Gallina, Alberto; Zagórski, Paweł; Rachucki, Jakub
    This paper presents a test bed designed to simulate the magnetic environment experienced by a spacecraft in a low Earth orbit. It consists of a spherical air bearing located inside a Helmholtz cage. The spherical air bearing is used for simulating the microgravity conditions of orbiting bodies, while the Helmholtz cage generates a controllable magnetic field resembling the one surrounding a satellite during its motion. Dedicated computer software is used to initially calculate the magnetic field in an established orbit. The magnetic field data is then translated into current values and transmitted to programmable power supplies that energize the cage. The magnetic field within the cage is finally measured by a test article mounted on the air bearing. The paper provides a description of the test bed and test article design. Experimental tests prove the good performance of the entire system.
  • thumbnail.journal.alt
    Item type:Article, Access status: Open Access ,
    On nonlocal modeling in continuum mechanics
    (Wydawnictwa AGH, 2015) Martowicz, Adam
    The objective of the paper is to provide an overview of nonlocal formulations for models of elastic solids. The author presents the physical foundations for nonlocal theories of continuum mechanics, followed by various analytical and numerical techniques. The characteristics and range of practical applications for the presented approaches are discussed. The results of numerical simulations for the selected case studies are provided to demonstrate the properties of the described methods. The paper is illustrated with outcomes from peridynamic analyses. Fatigue and axial stretching were simulated to show the capabilities of the developed numerical tools.
  • thumbnail.journal.alt
    Item type:Article, Access status: Open Access ,
    Shape-memory materials as control elements used in dot Braille actuator
    (Wydawnictwa AGH, 2014) Bryła, Jakub; Martowicz, Adam
    The objective of this paper is to show a designing process for actuators that utilizes shape-memory materials. Analytical studies are carried out to design a dot actuator to be used in an electronic Braille display. Shape-memory materials are a relatively new group of smart materials that exhibit the transformation of their internal structures in solid state phases resulting from external mechanical or thermal excitation. This unique property shows up as three phenomena: one- and two-way memory effects as well as superelasticity, which all significantly influence the change of both the material properties and geometry. Hence, shape-memory materials are used as actuators effectively controlled by the above-mentioned types of excitation. The work presents the design guidelines for a proposed technical solution as well as the phenomenon utilized in the elaborated model of the actuator. The authors derived the mathematical descriptions for the proposed design configuration and an example of the calculations is shown. Moreover, the characteristics of the elaborated configuration are also discussed, taking into account the range of application areas.
  • thumbnail.journal.alt
    Item type:Article, Access status: Open Access ,
    Complete kinematic analysis of the Stewart-Gough platform by unit quaternions
    (Wydawnictwa AGH, 2015) Serrano, Fernando E.; Rossell Garriga, Josep M.
    In this paper, a complete analysis of Stewart-Gough platform kinematics by unit quaternions is proposed. Even when unit quaternions have been implemented in different applications (including a kinematic analysis of the Stewart platform mechanism), the research regarding the application of this approach is limited only to the analysis of some issues related to the kinematic properties of this parallel mechanism. For this reason, a complete analysis of the Stewart-Gough platform is shown. The derivation of the inverse and forward kinematics of the Stewart platform using unit quaternions shows that they are suitable to represent the orientation of the upper platform due to their simplicity, equivalence, and compact representation as compared to rotation matrices. Then, the leg velocities are derived to compute these values under different conditions.
  • thumbnail.journal.alt
    Item type:Article, Access status: Open Access ,
    Time-variant frequency response function for analysis of time-varying mechanical systems
    (Wydawnictwa AGH, 2015) Dziedziech, Kajetan
    System Identification is an important and often complex process in many areas of engineering. This process is not easy when the parameters of the analyzed system vary with time. In such cases, classical methods fail to properly identify the parameters. The work demonstrated in this paper deals with the identification of natural frequencies in time-variant systems. The paper presents the application of the Time-Variant Frequency Response Function for this analysis. The calculation procedure requires division of the output spectrum by the input spectrum, which often leads to division by close-to-zero values, this leads to infinite (or undefined) values of the resulting transfer function. Additional processing is required for interpretation. The major focus and challenge relate to the ridge extraction of the above time-frequency characteristics. The methods presented in the paper are illustrated using an experimental multi-degree-of-freedom system. The results show that the proposed method correctly captures the dynamics of the analyzed time-variant systems.
  • thumbnail.journal.alt
    Item type:Article, Access status: Open Access ,
    Experimental investigations on energy harvesting from mechanical vibrations of buildings using Macro Fiber composite
    (Wydawnictwa AGH, 2016) Grzybek, Dariusz; Micek, Piotr Andrzej
    The monitoring of a structure (e.g., a building) enables safe utilization of such a structure. A large number of sensors that measure selected parameters are often required in applied monitoring systems. Cables or batteries are used to power such sensors. This leads to an increase in utilization costs, as the cables have to be spatially located in a monitored building structure, or batteries have to be changed periodically. The use of the natural properties of piezoelectric materials that convert mechanical energy into electrical energy in places where sensors are mounted is a promising field of wireless monitoring system development. This article presents the results of an experimental study for an energy harvesting system using a piezoelectric composite - the Macro Fiber Composite (MFC). The device used for energy harvesting has a beam structure that was achieved by gluing steel and MFC together. In laboratory research, the characteristics of generated currents and electrical power were obtained for several values of vibration amplitude. The most important conclusion was that the resonant frequency of a piezoelectric beam generator should be established (by the selection of proper dimension or/and mass) both for the vibration frequency of the monitored mechanical structure and the vibration amplitude of this structure.
  • thumbnail.journal.alt
    Item type:Article, Access status: Open Access ,
    Control system preventing thermal gradient development on foils of foil bearing
    (Wydawnictwa AGH, 2015) Lubieniecki, Michał Lucjan; Miodunka, Marek
    This article presents attempts at automating a control system to reduce temperature scatter on the foil of a foil bearing. The control system reads the temperatures at six circumferential locations of the bearing's foil and distributes control currents to the thermoelectric modules integrated into the bearing's bushing. Three basic approaches have been proposed and tested: 1) a simple hot-spot tracking algorithm assigning predefined current values to the modules closest to the hot-spot location, 2) a tracking algorithm reducing abrupt changes in the control currents and, in effect, the local heat flux distribution, and 3) a tracking algorithm enhanced with a PID controller. The proposed controller has been implemented and compared to the performance of a temperature controller that does not have tracking capabilities. The implemented control strategies have proven the feasibility of temperature scatter reduction inside the investigated bearing. In most test cases, the instantaneous gradient reduction exceeded 50% (reaching 63% at its best).
  • thumbnail.journal.alt
    Item type:Article, Access status: Open Access ,
    Physical model of vehicle engine mount with magnetorheological damper
    (Wydawnictwa AGH, 2016) Snamina, Jacek; Sapiński, Bogdan
    A physical model of a vehicle engine mount incorporating a magnetorheological (MR) damper in squeeze mode is investigated and the structural design and operating characteristics of the MR damper are provided. The mathematical model of an engine mount is formulated. Kinematic excitations are assumed to be those emulating road profile-chassis (car body) interactions. Simulations of engine vibration are performed to determine the efficiency of the proposed engine mount. Conclusions are drawn concerning the potential applications of the MR damper in vehicle engine mounts.
  • thumbnail.journal.alt
    Item type:Article, Access status: Open Access ,
    Strength study on soda-lime-silicate-toughened glass
    (Wydawnictwa AGH, 2015) Ładecki, Bogusław
    Toughened soda-lime-silicate glass is a popular material widely used in construction due to its very good functional properties, characterized by its high strength, safety in use, fire resistance, and good thermal insulation. In this study, tests were conducted to describe the dependence between the bending strength of ESG-toughened float glass and the thickness of the sample, state of the sample edge, and application of security film. Tests were also conducted on the influence of the placement of openings needed for mounting glass screens used to secure display cases and other objects of a similar nature. The information obtained was used to design glass security screens and a new type of display case, a closed cassette with a glass screen intended for use in protecting works of art from acts of vandalism and the destructive influence of environmental conditions.
  • thumbnail.journal.alt
    Item type:Journal Issue,
    Mechanics and Control
    2015 - Vol. 34 - No. 4