Thesis (MSc (Logistics))--University of Stellenbosch, 2009. / ENGLISH ABSTRACT: Technological advances made over the past century have had a major impact on traditional
wineries. Software solutions for management issues are widely available and give rise to the
prospect of computerized decision support systems assisting in various aspects of managing a
winery. The most popular applications seem to be concerned with supply chain management
or harvest scheduling. Such projects are under way all over the globe and great success has
been achieved to this e ect. However, prior to this study no such project has been considered
in South Africa.
The phrase active cellar scheduling problem refers to the assignment of grape batches to processors
inside the cellar where bottlenecks often occur during the busy harvesting period. The
phrase harvest scheduling problem, on the other hand, refers to selecting the best possible dates
to harvest the respective vineyard blocks in order to preserve grape quality.
A mixed integer programming model for the active cellar scheduling problem is derived in
this thesis, but proves to be too time consuming to solve exactly via the branch-and-bound
method. A meta-heuristic tabu search approach is therefore designed to solve the problem
approximately instead. When applied to a small, ctitious cellar, it is found that the tabu
search method often solves the problem optimally. The computer processing time associated
with the tabu search approach also constitutes a signi cant (often thousand-fold) improvement
over that of the branch-and-bound approach for realistically sized problem instances.
A generic tabu search is also designed to solve the over-arching harvest scheduling problem for
a general winery. This schedule is found by referring to the smaller tabu search of the active
cellar scheduling in order to verify the impact that harvesting moves have on activities in the
cellar. One harvesting schedule is considered a better schedule than another when it has a lower
harvest evaluation score, determined by the placement of the vineyard blocks in the harvesting
schedule. The harvest evaluation score takes into account the combination of vineyard blocks
selected for harvesting on the same day (and their e ect on the active cellar) as well as the
ripeness and quality of the grapes.
Both tabu searches are nally included in a
exible, computerized decision support system,
called VinDSS. This system is found to produce good harvesting schedules when compared
to an actual ve day schedule during the 2009 harvesting period at Wamakersvallei, a winery
serving as case study for this thesis. / AFRIKAANSE OPSOMMING: Tegnologiese vooruitgang oor die afgelope eeu het 'n groot invloed op tradisionele wynkelders
gehad. Sagteware-oplossings wat besluitsteun tot bestuursaangeleenthede bied, is algemeen
beskikbaar en het gelei tot die rekenaarmatige implementering van besluitsteunstelsels vir
wynkelders. Dit blyk dat die mees popul^ere besluitsteuntoepassings in die wynindustrie te
make het met besluite rakende van voorsieningskettings en oes-skedulering. Sulke besluitsteunprojekte
is w^ereldwyd onderweg en het alreeds groot sukses behaal. Daar is egter tot dusver
geen so 'n projek in Suid-Afrika onderneem nie.
Die frase aktiewe kelderskeduleringsprobleem verwys na die toekenning van druifvragte aan
masjiene binne die kelder waar bottelnekke algemeen tydens die besige parstydperk voorkom.
Die frase oes-skeduleringsprobleem, daarenteen, verwys na die seleksie van bes moontlike oesdatums
vir elk van die wingerdblokke om sodoende druifkwaliteit te verseker.
'n Gemengde heeltallige programmeringsmodel is vir die aktiewe kelderskeduleringsprobleem
ontwikkel, maar die rekenaaroplossingstyd van hierdie benadering blyk te lank te wees om die
probleem eksak deur middel van 'n vertak-en-begrens metode op te los. 'n Meta-heuristiese tabu
soektog is dus ontwikkel om die probleem benaderd op te los. Wanneer hierdie benadering op 'n
klein, ktiewe kelder toegepas word, word optimale oplossings dikwels verkry. Verder toon die
rekenaaroplossingstyd van die tabu soektog 'n groot (in sommige gevalle byna 'n duisendvoudige)
verbetering op di e van die eksakte oplossingsmetode.
'n Generiese tabu soektog is ook ontwikkel om die oorkoepelende oes-skeduleringsprobleem vir
'n algemene wynkelder op te los. So 'n oes-skedule word gevind deur na die kleiner tabu soektog
vir die aktiewe kelderskedulering te verwys om sodoende die e ekte van veranderinge in die oesskedule
op die prosesse binne die aktiewe kelder na te speur. Een oes-skedule word beter as 'n
ander skedule beskou wanneer dit met 'n beter oes-evalueringswaarde gepaard gaan, soos deur
die plasing van die wingerdblokke in die skedule bepaal. Die oes-evalueringswaarde neem die
moontlike kombinasies van wingerblokke wat op dieselfde dag geoes word, in ag (en ook die
e ek wat dit op aktiwiteite in die kelder het), asook die rypheid en kwaliteit van die druiwe.
Beide tabu soektogte word in 'n plooibare, rekenaar-ge mplementeerde besluitsteunstelsel, bekend
as VinDSS, ingesluit. Daar word gevind dat hierdie stelsel goeie oes-skedules lewer
wanneer dit vergelyk word met 'n werklike vyf-dag skedule tydens die 2009 parsseisoen van
Wamakersvallei, die kelder wat as gevallestudie vir hierdie tesis gedien het.
| Identifer | oai:union.ndltd.org:netd.ac.za/oai:union.ndltd.org:sun/oai:scholar.sun.ac.za:10019.1/3046 |
| Date | 12 1900 |
| Creators | Van der Merwe, Adri |
| Contributors | Van Vuuren, J. H., Van Wyk, F. E., University of Stellenbosch. Faculty of Economic and Management Sciences. Dept. of Logistics. |
| Publisher | Stellenbosch : University of Stellenbosch |
| Source Sets | South African National ETD Portal |
| Language | English |
| Detected Language | Unknown |
| Type | Thesis |
| Rights | University of Stellenbosch |
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