Novi pristup projektovanju i optimizaciji cikloidnih prenosnika snage

Rezime: Cikloreduktori pripadaju grupi planetarnih prenosnika snage. Pojavili su se u prvoj polovini XX veka i od tada je njihova upotreba u konstantnoj ekspanziji. Inovativni pristup projektovanju cikloreduktora predstavlja osnovni predmet istraživanja doktorske disertacije. U okviru ovih istraživanja predstavljen je sveobuhvatan pregled literaturnih izvora vezanih za problematiku cikloidnih prenosnika snage. Zatim su veoma detaljno opisane u praksi najčešće korišćene koncepcije jednostepenih i dvostepenih cikloreduktora. Posebna pažnja je posvećena analitičkim i eksperimentalnim modelima za određivanje stepena iskorišćenja. Za jedan konkretan jednostepeni cikloreduktor izvršen je proračun stepena iskorišćenja, a zatim su dobijeni rezultati potvrđeni i eksperimentalnim putem. U okviru disertacije razvijeni su i matematički modeli za određivanje dinamičke stabilnosti svih predstavljenih koncepcija cikloreduktora. Posebna pažnja je posvećena optimizaciji cikloidnih prenosnika snage. U programskom paketu AUTODESK Inventor razvijena je aplikacija za parametarsko modeliranje jednostepenih i dvostepenih cikloreduktora opisanih koncepcija. U okviru aplikacije moguće je izvršiti i kompletan proračun svih vitalnih delova cikloreduktora, kao i proračun stepena iskorišćenja. Razvijena aplikacija predstavlja jedan potpuno novi pristup projektovanju i optimizaciji cikloidnih prenosnika snage. Na kraju disertacije izneta su zaključna razmatranja, kao i pravci budućih istraživanja u oblasti cikloreduktora.Summary: The cycloid reducers belong to a group of planetary power transmissions. They appeared in the first half of the XX century and since then their application has been in constant expansion. An innovative approach to designing a cycloid reducer is the basic subject of doctoral dissertation research. Within this research, a comprehensive overview of the literature sources related to the problem of cycloidal reducers is presented. They are then described in detail in the practice of the most commonly used concepts of single and double stage cycloid reducers. Special attention has been paid to analytical and experimental models for determining efficiency. For one particular cycloid reducer, the calculation of the efficiency was performed, and then the obtained results were confirmed experimentally. In the framework of the dissertation, mathematical models for determining the dynamic stability of all presented concepts of cycloid reducers have been developed. Special attention is paid to the optimization of cycloidal reducers. In the AUTODESK Inventor software package, parametric modeling of the single-stage and doublestage cycloid reducer of the described concepts has been developed. Within the application, it is possible to perform a complete calculation of all cycloid reducer vital parts, as well as a calculation of the efficiency. The developed application is a completely new approach to the design and optimization of power transmission gearboxes. At the end of the dissertation, the final considerations, as well as the directions of future research in the field of cycloid reducer, are presente

Dynamic Behaviour of a Two-Stage Cycloidal Speed Reducer of a New Design Concept

Traditional cycloidal speed reducers (with two cycloid discs per one stage, mutually turned by an angle of 180°) are well known for their remarkable dynamic stability. This paper analyses dynamic behaviour of a two-stage cycloidal speed reducer of a new concept, in which only one cycloid disc is used for each stage in order to further enhance its compactness. Lagrange’s displacement equations have been used to develop independent dynamic models for both the first and the second stage (six degrees of displacement freedom for the first stage, and eight degrees of displacement freedom for the second stage). A normal force acting at the contact of the cycloid disc teeth and the corresponding ring gear roller has been taken as an excitation force. For the newly designed two-stage cycloidal speed reducer, systems of differential displacement equations of the first and second stage have been solved using the Matlab – Simulink software package. A comprehensive analysis of the obtained diagrams of elastic dynamic contact forces of the first and second stage has revealed a certain analogy. In terms of dynamics, the cycloid disc of the second stage behaves similarly to the cycloid disc of the first stage. Since these cycloid discs are mutually turned by an angle of 180°, it can be concluded that from the aspect of the cycloid disc load, the two-stage cycloidal speed reducer of a new design concept exhibits good dynamic balance and stability

Determination of Real Clearances Between Cycloidal Speed Reducer Elements by the Application of Heuristic Optimization

The actual cycloidal speed reducer elements differ from their theoretical ideal due to existing tolerances; therefore, the cycloid disc behaves like a corrected one. This study is oriented towards determining contacts in corrected cycloid speed reducer profiles from the aspect of geometry. Based on this geometry, an objective function was developed for the optimization with some limitations. Heuristic optimization was used to determine the position of the cycloidal drive elements when a contact was established and, consequently, to determine clearances in other places. Some limitations were set so that the model could reflect a real contact. In this study, a TLBO algorithm was used for the optimization of a cycloidal speed reducer. Clearances were analysed for different correction values of the cycloid disc profile of an actual cycloidal drive and the optimization procedure was presented. The results provide a real picture of the contact in the presence of inevitable machining tolerances

INFLUENCE OF THE TEETH NUMBER ON THE GEAR MODULE VALUE AND LOAD CAPACITY OF GEAR PAIR IN UNIVERSAL HELICAL GEAR DRIVES

The basic parameters of the universal gear drives, except the axis height, are not defined by the standard, so the manufacturers of universal gear reducers can define them in their way. Most of the manufacturers followed the parameter values of universal gear reducers of leading world producers in order to ensure their interchangeability and the better positioning of their gear units at the market. This paper deals with the analysis of the influence of the gear pair teeth number on the size of the module, as well as on the load carrying capacity of single-stage universal gear units. For defined gear ratio values, different combinations of teeth number of pinion and driven gear were selected. Further, it was made calculation of the basic geometric dimensions of the gear pair, as well as the load capacity

Novi pristup projektovanju i optimizaciji cikloidnih prenosnika snage

Rezime: Cikloreduktori pripadaju grupi planetarnih prenosnika snage. Pojavili su se u prvoj polovini XX veka i od tada je njihova upotreba u konstantnoj ekspanziji. Inovativni pristup projektovanju cikloreduktora predstavlja osnovni predmet istraživanja doktorske disertacije. U okviru ovih istraživanja predstavljen je sveobuhvatan pregled literaturnih izvora vezanih za problematiku cikloidnih prenosnika snage. Zatim su veoma detaljno opisane u praksi najčešće korišćene koncepcije jednostepenih i dvostepenih cikloreduktora. Posebna pažnja je posvećena analitičkim i eksperimentalnim modelima za određivanje stepena iskorišćenja. Za jedan konkretan jednostepeni cikloreduktor izvršen je proračun stepena iskorišćenja, a zatim su dobijeni rezultati potvrđeni i eksperimentalnim putem. U okviru disertacije razvijeni su i matematički modeli za određivanje dinamičke stabilnosti svih predstavljenih koncepcija cikloreduktora. Posebna pažnja je posvećena optimizaciji cikloidnih prenosnika snage. U programskom paketu AUTODESK Inventor razvijena je aplikacija za parametarsko modeliranje jednostepenih i dvostepenih cikloreduktora opisanih koncepcija. U okviru aplikacije moguće je izvršiti i kompletan proračun svih vitalnih delova cikloreduktora, kao i proračun stepena iskorišćenja. Razvijena aplikacija predstavlja jedan potpuno novi pristup projektovanju i optimizaciji cikloidnih prenosnika snage. Na kraju disertacije izneta su zaključna razmatranja, kao i pravci budućih istraživanja u oblasti cikloreduktora.Summary: The cycloid reducers belong to a group of planetary power transmissions. They appeared in the first half of the XX century and since then their application has been in constant expansion. An innovative approach to designing a cycloid reducer is the basic subject of doctoral dissertation research. Within this research, a comprehensive overview of the literature sources related to the problem of cycloidal reducers is presented. They are then described in detail in the practice of the most commonly used concepts of single and double stage cycloid reducers. Special attention has been paid to analytical and experimental models for determining efficiency. For one particular cycloid reducer, the calculation of the efficiency was performed, and then the obtained results were confirmed experimentally. In the framework of the dissertation, mathematical models for determining the dynamic stability of all presented concepts of cycloid reducers have been developed. Special attention is paid to the optimization of cycloidal reducers. In the AUTODESK Inventor software package, parametric modeling of the single-stage and doublestage cycloid reducer of the described concepts has been developed. Within the application, it is possible to perform a complete calculation of all cycloid reducer vital parts, as well as a calculation of the efficiency. The developed application is a completely new approach to the design and optimization of power transmission gearboxes. At the end of the dissertation, the final considerations, as well as the directions of future research in the field of cycloid reducer, are presente

Volume optimization of gear trains with spur gears using genetic algorithm

Gear train volume optimization presents a complex problem tied to practical application in gear train manufacturing. This paper is oriented on the analysis of the problem of gear train volume minimization from a shaft axes positioning aspect. An original mathematical model has been developed where the objective function gives a minimum volume with changed shaft (spur gear) axes positions, while at the same time complying with all physical constraints. An original optimization software has also been developed using RCGA (Real Coded Genetic Algorithm) optimization methods. The general mathematical model was applied to three real conceptions of gear train as well as a comparative analysis of initial and optimal values. The results show a decrease of volume being directly linked to a decrease of not only space but material used to make the housing, costs, documentation formulation rate, etc

Association of pulmonary histopathological findings with toxicological findings in forensic autopsies of illicit drug users

Background/Aim. Drug abuse remains a significant social problem in many countries. The aim of the study was to estimate association between pulmonary histopathological changes and results of toxicological analyses in forensic autopsies of illicit drug users. Methods. This investigation was performed in the Institute of Forensic Medicine, Belgrade, and in the Clinical Center, Department of Forensic Medicine, Kragujevac, from 2000 to 2004, and included 63 medicolegal autopsies of heroin or other drug consumers who suddenly died. Autopsies, postmortem toxicological examination of drugs and serological analyses of anti- HIV/HBV/HCV antibodies were performed. Results. The deceased persons were mostly male, 46/63 (73.01%), ranged in age from 19 to 49 years (mean 31 years) and all were whites. Postmortem toxicological examination was performed on all of the deceased persons and drugs in the fatal range were identified in only eight of them (12.7%), in the toxic range in ten (15.87%), and in minimal concentrations in 35 (55.56%) of the deceased persons. Drugs identified in the fatal, toxic or minimal range included heroin-morphine (38/53), cocaine (4/53), tramadol (3/53), and lorazepam (1/53). In the 7 remaining subjects, ethanol in combination with heroin was found in 4 cases, and diazepam in combination with heroin in 3 cases. Dominant pathomorphological changes were findings in the lung tissue. Most common histological changes observed in drug users were pulmonary edema - 55/63 (87.3%), acute alveolar hemorrhages - 49/63 (77.78%), hemosiderin-laden macrophages (siderophages) - 52/63 (82,54%), and emphysematous changes - 51/63 (80,95%). Conclusion. Pulmonary edema is the frequent non-specific autopsy finding which is associated with virtually all routes of drug administration. The histopatological study is necessary to determinate a cause of death when a deceased person has the history of dependence or abouse of psychoactive drugs with negative toxicological results

Association of pulmonary histopathological findings with toxicological findings in forensic autopsies of illicit drug users

Background/Aim. Drug abuse remains a significant social problem in many countries. The aim of the study was to estimate association between pulmonary histopathological changes and results of toxicological analyses in forensic autopsies of illicit drug users. Methods. This investigation was performed in the Institute of Forensic Medicine, Belgrade, and in the Clinical Center, Department of Forensic Medicine, Kragujevac, from 2000 to 2004, and included 63 medicolegal autopsies of heroin or other drug consumers who suddenly died. Autopsies, postmortem toxicological examination of drugs and serological analyses of anti- HIV/HBV/HCV antibodies were performed. Results. The deceased persons were mostly male, 46/63 (73.01%), ranged in age from 19 to 49 years (mean 31 years) and all were whites. Postmortem toxicological examination was performed on all of the deceased persons and drugs in the fatal range were identified in only eight of them (12.7%), in the toxic range in ten (15.87%), and in minimal concentrations in 35 (55.56%) of the deceased persons. Drugs identified in the fatal, toxic or minimal range included heroin-morphine (38/53), cocaine (4/53), tramadol (3/53), and lorazepam (1/53). In the 7 remaining subjects, ethanol in combination with heroin was found in 4 cases, and diazepam in combination with heroin in 3 cases. Dominant pathomorphological changes were findings in the lung tissue. Most common histological changes observed in drug users were pulmonary edema - 55/63 (87.3%), acute alveolar hemorrhages - 49/63 (77.78%), hemosiderin-laden macrophages (siderophages) - 52/63 (82,54%), and emphysematous changes - 51/63 (80,95%). Conclusion. Pulmonary edema is the frequent non-specific autopsy finding which is associated with virtually all routes of drug administration. The histopatological study is necessary to determinate a cause of death when a deceased person has the history of dependence or abouse of psychoactive drugs with negative toxicological results

Приручник за енергетске менаџере за област општинске енергетике

Народна скупштина Републике Србије је 15. марта 2013. године усвојила Закон о ефикасном коришћењу енергије са циљем да реализује стратешке циљеве и испуни преузете међународне обавезе, пре свега сходно Уговору о оснивању енергетске заједнице. Овим Законом се по први пут успоставља правни оквир и институционално уређује област ефикасног коришћења енергије у Републици Србији. Иако је главни циљ доношења овог Закона био да обезбеђивањем правне основе подржи рационално и одрживо коришћење енергије, како би се допринело сигурнијем снабдевању енергијом, конкурентности привреде и заштити животне средине, главни разлог је ипак био захтев Енергетске заједнице да се у законодавство Србије пренесу одредбе из три тада актуелне директиве о енергетској ефикасности у финалној потрошњи енергије. Међутим, иако је главни разлог доношења Закона био преношење одредби директива, овај Закон је сасвим аутохтоно, као основни механизам за спровођење ових одредби, али и читавог низа других мера и активности којима се могу остварити уштеде енергије, предвидео увођење Система енергетског менаџмента (СЕМ) у области финалне потрошње енергије.Након усвајања Закона о ефикасном коришћењу енергије, Министарство је 2013. године у сарадњи са Програмом Уједињених нација за развој (УНДП) започело са спровођењем пројекта „Успостављање информационог система за енергетски менаџмент (ИСЕМ) у јавним зградама у Републици Србији“,чији су резултати били увођење и успостављање ИСЕМ и израда овог приручника. У исто је време Министарство са JICA покренуло пројекат „Помоћ за унапређивање система енергетског менаџмента у свим секторима потрошње енергије у Републици Србији“, који је резултирао усвајањем потребног сета подзаконских аката чиме су се почетком 2016. стекли услови да се започне са држањем обуке за енергетске менаџере из области општинске енергетике. Био је то први практичан корак на путу ка успостављању система енергетског менаџмента. Не заустављајући се на томе, Министарство и УНДП су крајем 2015. године почели са спровођењем још једног пројекта под називом “Смањење баријера за промовисање и увођење система енергетског менаџмента у општинама Србије“. Пројекат се надовезује на претходне, чиме се обезбеђује континуитет рада на развоју институционалног и правног оквира за енергетски менаџмент, као и дугорочно јачање капацитета локалних самоуправа за његово спровођење

Приручник за енергетске менаџере за област енергетике зграда

После усвајања Закона о ефикасном коришћењу енергије, од 2013. године, кључни кораци на реализацији успостављања СЕМ-а спроведени су најпре у кроз пројекат „Унапређивање система енергетског менаџмента у свим секторима потрошње енергије у Републици Србији”, кроз који је JICA донирала Министарству лабораторијску опрему и мерне инструменте неопходне за практичну обуку енергетских менаџера. На предлог Министарства, Влада у фебруару 2015. године доноси Закључак о прибављању у својину Републике Србије и давању на коришћење ове опреме Универзитету у Београду, Машинском факултету. Са добијеном опремом, Машински факултет уз помоћ JICА-е формира и опрема Лабораторију за практичну обуку енергетских менаџера. Истовремено, по спроведеном Јавном позиву за избор Организације за обуку, Решењем Министра, 19. октобра 2015. године, Универзитет у Београду, Машински факултет добија овлашћење да обавља послова обуке енергетских менаџера. Приручник за обуку енергетских менаџера за област енергетике зграда, је написан и намењен првенствено полазницима обуке за енергетског менаџера за област енергетике зграда, али може да послужи и као уџбеник за све друге курсеве који се баве проблематиком рационалног коришћења енергије у зградама и системом енергетског менаџмента. Сходно томе, приручник може да буде од користи инжењерима различитих дисциплина, као и студентима техничких факултета који се баве или желе да се баве наведеном тематиком