Projektovanje i ispitivanje struktura baza podataka u upravljanju održavanjem vazduhoplovanih sistema

Abstract

Visoki zahtevi koji se postavljaju sistemu za odrzavanje vazduhoplova izmedu ostalog zahtevaju temeljnu analizu postojece strategije odrzavanja i njeno znacajno unapredenje. Savremeni sistemi odrzavanja obuhvataju i upravljanje odrzavanjem, tj. zasnovani su na automatizovanoj podrsci odrzavanju primenom racunara (Computer Integrated Maintenance Management). U osnovi automatizovane podrske odrzavanju primenom racunara je model podataka. Veoma je vazno da je model podataka dovoljno bogat da bi mogao, na relativno lak nacin prihvatiti i u sebe ukljuciti razlicite koncepte realnog sistema zajedno sa svojim atribu- tima i medusobnim vezama. Hijerarhijske strukture podataka (strukture podataka tipa stablo) su posebno interesantne u sistemu odrzavanja vazduhoplova i one su predmet istrazivanja u ovom radu. Postavlja se sledeci zahtev. Obezbediti takvu implementaciju hijerarhijske struk- ture koja pruza mogucnost njene ekasne obrade. Rekurzija koja je u osnovi hijerarhijske strukture podataka odnosno stabla koji je reprezent ovakve strukture podataka, moze biti problem u ekasnom upravljanju sistemom odrzavanja vazduhoplova. U radu su date nove karakterizacije stabla, koje daju osnov za nerekurzivne modele hijerarhijske strukture poda- taka. U kontekstu ogranicenih resursa u sistemu za odrzavanje vazduhoplova posebno su intere- santne optimalne strategije odrzavanja. Bitan segment sistema za upravljanje odrzavanjem je planiranje odrzavanja. Jedan od osnovnih problema izmedu ostalog je neizvesnost dogadaja koji znacajno uticu na samo planiranje. Rec je o dogadajima koji su po svojoj prirodi slucajni. Posebno analizira se planiranje odrzavanja u slucaju kada skup aktivnosti ima hijerarhijsku strukturu i pri tome je trajanje pojedinih aktivnosti iz datog skupa aktivno- sti slucajna velicina. Pod pretpostavkom da aktivnost na visem nivou hijerarhije ne moze zapoceti pre nego sto su zavrsene sve aktivnosti na nizem nivou hijerarhije i da su poznati gubici koji nastaju u slucaju da se sa nekim aktivnostima kasni, odnosno da su poznati gu- bici u slucaju da su neke aktivnosti preuranjene, potrebno je formirati optimalnu strategiju aktiviranja aktivnosti iz datog skupa. U slucaju hijerarhije visine jedan problem se svodi na poznati newsboy problem, ali je u opstem slucaju isuvise komplikovan. U radu se predlaze heuristicki pristup kojim se do resenja dolazi iterativnom primenom jednostavnog resenja problema na dvononiovskoj hijerarhiji. Vazduhoplovi su savremena saobracajna sredstva vrhunske tehnologije sa velikim bro- jem komponenti i kompleksnom strukturom. Pojedine komponente vazduhoplova se koriste na razlicit nacin, trpe razlicita opterecenja i odrzavaju po programu koji je njima najbolje prilagoden. Jedan od nacina savladavanja slozenosti je takozvana hijerarhijska dekompozi- cija. Slozeni koncept se na jednom nivou apstrakcije posmatra kao jedinstvena celina. Na nizem nivou apstrakcije se posmatra kao koncept koji se sastoji od delova (komponenti). Uzastopnom primenom opisanog postupka dobija se takozvana hijerarhijska sastavnica. Da- kle jedan od bitnih koncepata u sistemu odrzavanja vazduhoplova jeste sastavnica. Poseban problem je obezbediti kvalitetan sadrzaj hijerarhijske strukture podataka, odnosno u sistemu za upravljanje odrzavanjem vazduhoplova treba obezbediti kvalitetnu sastavnicu. U radu je predlozena eksibilna struktura sastavnica koja u velikoj meri podrzava njeno sadrzajno rasirenje...

The high demands that are placed to aircraft maintenance systems among other things require thorough analysis of existing maintenance strategy and its signicant improvement. Modern maintenance systems include the management of maintenance, i.e. they are based on automated maintenance support by computer - Computer Integrated Maintenance Mana- gement. The basic component in automated maintenance support account is data model. It is important that the data model is rich enough to accept in a relatively easy way a variety of real system concepts together with their attributes and interrelations. Hierarchical data structure ( textit tree type data structure) are of special interest in the aircraft maintenance systems, and they are the subject of this study. This raise the following request. Implement hierarchical data structure which allows ecient processing. Recursion which is essential in implementation of hierarchical data structure, i.e., of the tree, which is typical representative of these data structures, can be a problem in ecient aircraft maintenance management. This study gives a new characterizations of tree, which provide a basis for nonrecursive models of hierarchical data structures. In the context of limited resources in the aircraft maintenance systems, optimal mainte- nance strategies are of special interest. An important segment of the maintenance manage- ment system is maintenance planning. One of the major problems is uncertainty of events which signicantly aect maintenance planning. These events are random by its nature. In particular, the planning of maintenance is analyzed in the case when the set of activities has a hierarchical structure and duration, of each activity from a given set of activities, is random value. Assuming that the activity at a higher level of hierarchy can not begin before the completion of all activities at a lower level of hierarchy, and that losses incurred in the case of delayed activities, i.e., losses incurred in the case of premature activity are known, it is necessary to establish optimal activating strategy for each activity from given set of activities. In the case of one level hierarchy, problem is reduced to the well known newsboy problem, but it is too complicated in general. In this study, a heuristic approach is proposed for the solution of general problem that is based on iterative application of the solution of a simple two levels hierarchy problem. Aircrafts are modern high-tech means of transport with a large number of components and complex structure. Components of aircraft are used in dierent ways, they suer dierent loads and are maintained by the programs that are best suited for them. One way to overcome this complexity is so-called hierarchical decomposition. Complex concept at one level of abstraction is seen as unied. At the lower level of abstraction it is seen as a concept that consists of parts (other components). Repeated application of described procedure gives the so-called hierarchical bill of material. So one of the important concepts in the aircraft maintenance systems is bill of material. A particular problem is to provide quality hierarchical data structures to the aircraft maintenance management system, i.e., to provide quality bill of material. This study proposes a exible structure of the bill of material which greatly supports disseminate its content...