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1
On engineering verifications of external and internal fixators for traumatology and orthopaedics
Frydrysek K., Ucen O., Fojtik F., Poruba Z., Theisz G., Sejda F., Michenkova S.
Modelowanie Inżynierskie
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2014
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T. 21, nr 52
42--50
EN
In this article the authors draw attention to the possibilities of treatment for complicated bone fractures. They present their own design, laboratory tests and numerical solutions (i.e. strength analyses and reliability assessments) of the various types of internal and external fixators applied in traumatology and orthopaedics (i.e. intended for fractures of limbs, pelvis and calcaneus). The new design of external fixators is based on the development of Ilizarov and other techniques (i.e. shape and weight optimization based on composite materials, application of smart materials, nanotechnology, low x-ray absorption, antibacterial protection, patient comfort, reduction in the duration of surgical treatment, and cost). Similarly, the new intramedullary nail C-NAIL (i.e. an example of an internal fixator) is intended for minimal-invasive fixation of intra articular calcaneal fractures.
2
Modal properties of theatre lifting platform - experiment versus FEM
Poruba Z., Szweda J.
Modelling and Optimization of Physical Systems
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2011
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z. 10
65--68
EN
The presented paper deals with the dynamic properties analysis of the steel structure. The construction consists of the stationary and movable parts, the significant dynamic loading caused by the change of motion state during run up and run down is expected. The three ways of the dynamic analysis realizations - by finite element method for two types of 3-D finite elements and by experimental verification of modal properties using experimental modal analysis are presented.
CS
Pfedlozena prace se zabyva analyzou dynamickych vlastnosti konstrukce, ktera sestava ze stacionarni a pohyblive ćasti a u niz je v provozu oćekavan yyznamny podil dynamickeho zatezovani vyvolaneho zmenou pohybcweho stavu pfi rozjezdu a zastavovani. Je prezentewano troji provedeni analyzy dynamickych vlastnosti, ktera była feśena jednak metodou konećnych prvku pro dva typy 3D modelu, a to pro nosnikovo-skofepinovy a pro objemovy model, a jednak experimentalnim ovefenim modalnich vlastnosti vybrane skupiny vlastnich tvaru.
3
Analysis and optimization of the spatial mechanism
Frantisek O., Szweda J., Poruba Z.
Modelling and Optimization of Physical Systems
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2010
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z. 9
21--28
EN
The paper deals with an analysis and an optimization of the truck shifting mechanisms. The aim of the work is to optimize the trajectory of a shifting lever hand-grip in order to obtain an acceptable ergonomic trajectory. A mathematical surrogate of the shifting mechanism has been constructed and the following use of the optimization algorithms resulted in several modifications of mechanism dimensions.
4
Content available Numerical simulation of feedback controlled fluid-induced instabilities in rotor system supported by hydrodynamic bearings
Ferfecki P., Sikora R., Poruba Z.
Archives of Control Sciences
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2010
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Vol. 20, no. 3
287-301
EN
In certain operating conditions, the oil-film forces, by which the hydrodynamic bearings act on the rotor, destabilize and induce a self-excited vibration. There are many solution based on modifications of the bearing geometry to enlarge the operational range of the hydrodynamic bearing as a tilting pad bearing, lemon bore, etc. or usage of the dampers whose operation is based only on the dissipation of mechanical energy. In this paper several concepts based on controlled kinematic excitation of the bearing shells is investigated by computer simulation and by experimental test. The mathematical model of the uncontrolled and controlled rotor system contains the nonlinear hydrodynamic forces determined by the solution of the Reynolds equation assuming short case of bearing. To solve the equation of motion the Runge-Kutta method of the 4th order with Dormand-Prince modification and variable length of the integration step is used. The computer simulations were performed for rotor system without feedback control and with feedback controller. The main objectives of the numerical analysis were determination of the stability regions of the vibration excited by the imbalance forces. Results of the computer simulations proved that the analyzed approaches reduce amplitude of the rotor vibration caused by the imbalance forces. Experimental test and computer simulations demonstrate that the active vibration control increases considerably the rotation speed when the self-excited vibration of the oil-film occurred.
5
Shape optimization of the electromotor frame ribs
Szweda J., Poruba Z.
Modelling and Optimization of Physical Systems
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2009
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z. 8
107--112
EN
The contribution presents the cooling rib optimization on the two numerical models with the aim to show the influence of used model geometry on the optimization problem properties. The parameters of used computational models (the models differ in used symmetry conditions) and the application of boundary conditions are presented. The obtained results show the necessity to take into account the authentic rib space arrangement in model simulations of optimization problem.
CS
Článek prezentuje optimalizaci chladicího žebrování na dvou výpočtových modelech, s cílem poukázat na vliv rozdílnosti modelů na vlastnosti optimalizační úlohy. Jsou popsány parametry použitých počítačových modelů (modely se liší v užitých podmínkách symetrie) a aplikace okrajových podmínek. Získané výsledky dokumentují nutnost zohlednění věrného prostorového uspořádání žeber v modelových simulacích úlohy optimalizace.
6
Active vibration reduction of rigid rotor supported by journal bearings
Ondrouch J., Ferfecki P, Poruba Z
Modelling and Optimization of Physical Systems
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2009
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z. 8
85--90
EN
The contribution describes the possibilities of active reduction of lateral vibration of symmetric, rigid rotor supported by journal bearings on the base of computational modelling. The efficiency of the feedback P, PD and PID controllers in stable revolution area is examined. To do it the linearized rotor system model is used. The results of the theoretical analysis will be used for the testing stand where the bearing shells motions are controlled by the piezoelectric actuators connected with controllers.
CS
Článek se zabývá možnostmi aktivního snížení příčného kmitání symetrického, dokonale tuhého rotoru uloženého na hydrodynamických ložiskách, na základě počítačového modelování. Je zkoumána účinnost zpětné vazby s regulátory P, PD a PID ve stabilní otáčkové oblasti. Κ tomu je využit linearizovaný model rotorové soustavy. Výsledky teoretické analýzy budou využily u zkušebního stavu, u kterého jsou pohyby ložiskových pouzder ovládány pomocí piezoaktuátorů napojených na regulátory.
7
Determination of steady-state response of active controlled rotor system with fatigue crack
Ferfecki P., Poruba Z., Ondrouch J.
Modelling and Optimization of Physical Systems
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2008
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z. 7
23--28
EN
The influence of feedback control of radial active magnetic bearing (AMB) on steady-state component response of rotor system with the shaft damaged by fatigue crack by numerical simulations is examined in this contribution. It was found out that in case of assumed conditions is the influence of the controller’s parameters on the response on excitation by centrifugal forces not significant. More significant torsion response is excited in case of rotor with slant oriented crack to the direction on rotation axis.
CS
V příspěvku je pomocí numerických simulací zkoumán vliv zpětnovazebního řízení radiálních aktivních magnetických ložisek na ustálenou složku odezvy rotorové soustavy s hřídelem poškozeným únavovou trhlinou. Zjistilo se, že za zkoumaných podmínek je vliv změn parametrů regulátoru aktivních magnetických ložisek na odezvu na buzení odstředivými silami nevýznamný. Ukázalo se, že výraznější torzní odezva se vybudí u rotoru se šikmo než příčně orientovanou trhlinou k ose rotace.
8
Dynamic properties of the rotor system supported by radial active magnetic bearings
Ferfecki P., Poruba Z., Ondrouch J.
Modelling and Optimization of Physical Systems
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2007
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z. 6
41--46
EN
The contribution deals with the research of the lateral vibration of rotor system supported by radial active magnetic bearing (AMB) controlled by current PD controller on the base of Campbell’s diagram, eigenshapes of vibration, vibration responses, diagrams of stability of steady-state excited by imbalance forces and frequency spectra. For determination of the steady-state component of rotor system response on excitation by centrifugal forces of rotating parts the method of trigonometric collocation was used.
CS
V predlozenem prispevku je pricne kmitani rotorove soustavy ulozene v radialnich aktivnich magnetickych loziskach rizenych s proudovym PD regulatorem zkoumano na zaklade Campbellova diagramu, vlastnich tvaru kmitani, rezonacnich krivek, diagramu stability ustaleneho vynuceneho kmitani a frekvencnich spekter. K vypoctu ustalene slozky odezvy rotorove soustavy na buzeni odstredivymi silami rotujicich casti je pouzita metoda trigonometricke kolokace.
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