Pallet routing strategies for a reconfigurable conveyor.

Havenga, Pieter-Jan (2017-03)

Thesis (MEng)--Stellenbosch University, 2017.


ENGLISH ABSTRACT: A reconfigurable manufacturing system is characterized by high customizability and a high throughput rate. The research presented in this thesis considers a reconfigurable approach to the path planning of a palletized conveyor. Reconfigurability here implies minimizing pallet transportation time by selection of the quickest routes. Previous research by the Mechatronics, Automation and Design Research Group of Stellenbosch University developed a holonic controller for a palletized, modular conveyor. The focus in this thesis was to adapt this controller to include the functionality of path optimization. Simulation software was used to simulate the palletized conveyor and construct a path optimization tool. Simio was the simulation software used. The virtual conveyor setup was constructed in Simio and, together with the Simio application programming interface (API), enabled predicting the travelling times of pallets on the conveyor. For the virtual conveyor the PLCs operating the conveyor were substituted by DLLs which were written in C#. This substitution of the hardware was to ensure that with only minor changes, the existing controller could also control the virtual conveyor. The predicted travelling times for the different routes were recorded, from which the quickest path was selected. Experiments were conducted on an experimental setup of a reconfigurable assembly system to verify that reconfigurability was rapid and reliable. A traffic junction was set up to compare performances of the controller without path optimization with the controller which has the path optimization installed. The results confirmed that simulation can be considered as a way to add reconfigurability to the path planning of a conveyor in a manufacturing system. Latency, however, proved to be a concerning factor when utilizing a holonic controller in running simulations. The holonic controller integrated with the simulations, was substituted with a controller that was developed in the simulation software itself. This approach alleviated the problem of latency found in the previous approach, and lent credibility to having a simulation controller as an optimizing tool to the path planning of a reconfigurable conveyor.

AFRIKAANSE OPSOMMING: ‘n Herkonfigureerbare vervaardigingstelsel word gekenmerk deur hoë aanpasbaarheid en ‘n hoë deurset. Die navorsing in hierdie tesis oorweeg ‘n herkonfigureerbare benadering tot die roetebeplanning van ‘n vervoerband met pallette. Herkonfigureerbaarheid impliseer hier die minimering van die tyd wat dit ‘n pallet neem om van een punt na ‘n volgende te beweeg, deur gebruik te maak van die vinnigste roetes. Vorige navorsing, gedoen deur die Megatronika, Outomatisasie en Ontwerp Navorsingsgroep van die Universiteit van Stellenbosch, was om ‘n holoniese beheerder te ontwikkel vir ‘n modulêre vervoerband met pallette. Die fokus in hierdie tesis was om hierdie beheerder aan te pas om die roete optimering funksionaliteit in te sluit. Simulasie sagteware is gebruik om die vervoerband met pallette te simuleer en ‘n roete optimering strategie te ontwikkel. Simio is die sagteware wat gebruik was. Die virtuele vervoerband was opgestel in Simio en het, tesame met die Simio program se programmeerbare intervlak, dit moontlik gemaak om die vervoertye van pallette op die vervoerband te voorspel. Vir die virtuele vervoerband is die PLCs wat die vervoerband beheer het, met DLLs vervang wat in C# geskryf was. Hierdie vervanging van hardeware het verseker dat, met min aanpassings, die bestaande beheerder ook die vervoerband kan beheer. Die vervoertye wat voorspel is vir die verskillende roetes, is opgeneem en die vinnigste roete is gekies. Eksperimente is uitgevoer op ‘n eksperimentele opstelling van ‘n herkonfigureerbare monteringstelsel om vas te stel dat herkonfigureerbaarheid vinnig en betroubaar geskied. ‘n Verkeersaansluiting is gebruik om die beheerder met roete optimering funksionaliteit te demonstreer. Die resultate het aangedui dat simulasie wel as ‘n moontlikheid oorweeg kan word om herkonfigureerbaarheid toe te voeg tot die roete beplanning van ‘n vervoerband met pallette in ‘n vervaardigingstelsel. Vertragings van programme was ‘n beduidende faktor wat geobserveer was gedurende die gebruik van ‘n holoniese beheerder in simulasies. Die holoniese beheerder wat geïntegreerd was met simulasies, is vervang met ‘n beheerder wat ontwikkel is slegs in die simulasie sagtware. Hierdie benadering het die probleem van vertragings aangespreek, en kredietwaardigheid verleen aan die benadering van simulering tot die optimering van roetebeplanning vir ‘n herkonfigureerbare vervoerband met pallette.

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