Abstract:
This report proposes using a discrete event simulation approach to investigate the application
and integration of Low Cost Intelligent Automation (LCIA) at a local automotive manufacturer
located in Rosslyn, Pretoria. Low cost automation solutions are implemented in the form of
Automated Guided Vehicles (AGVs) which are used as material handling mechanisms. Critical
factors pertaining to the design and operation of these systems are the guide-path layout, the
number of AGVs required and the vehicle dispatch rules. Literature on the subject matter
showed that these design problems can be solved by using analytical models or simulation models.
AGV systems are large and complex with various interrelating components that make up
the complete system. Therefore, simulation modelling is chosen as the tool for this application
as it is capable of handling these complex systems. The three main issues pertaining to the
AGV system design are presented and analysed in this report. The conventional and tandem
guide paths are analysed together with the workload-based Maximum Remaining Outgoing
Queue Size (MROQS) dispatch rule and time-base Modified First Come First Serve (MFCFS)
dispatch rule. These guide paths and dispatch rules are combined in four scenario models, each
focussing on a specific combination of a guide path and dispatch rule. For each of the scenario
models, the number of AGVs are varied and the changes in system performance are observed
and documented. These scenario models are developed with discrete event simulation models,
and are evaluated based on key performance indicators. The specific performance indicators
comprised of the total throughput of the AGV system, the utilisation of AGVs and the buffer
sizes at three stations. From the scenarios it is found that both the conventional and tandem
guide path have similar results for both dispatch rules. Of the two guide paths, the conventional
is more sensitive to the changes in dispatch rules. It is concluded that the best performing system
is the tandem guide path with a MFCFS dispatch rule and a total of three AGVs in the
system. It provided, on average a total output of 135 front and rear end bumpers. The AGVs in
the loop are also fully utilised with a high utilisation of 85%. The proposes system also reduced
the total walking distance by 37% and streamlines the material supply process to the station
by eliminating unnecessary motions.
