SIMSCRIPT Solutions


Health Care


Automated Guided Vehicle System in a Hospital

University of Zagreb; Zagreb, Yugoslavia

The model simulates an automated guided vehicle system (AGVS) with an automated vertical transportation system in a new 1100 bed hospital in Yugoslavia. The goal of the study was to determine the allocation and size of storage space for vehicles, the minimum number of vehicles required, the accomplishment of a transportation network timetable and the queuing situation in the system.

Large quantities of several types of materials have to be transported on a daily basis through the transportation network, including food, linen, sterile materials, medicines, and waste. The quantity of materials that has to be transported and the transportation distribution depend mainly upon the number and spatial distribution of patients, in-patient units and various processing units in the hospital. The dimension of the transportation problem can be seen from the approximate figures of about 35 tons of materials that have to be transported daily and transportation paths that occasionally exceed 400 meters.

The transportation schedule devised for the hospital transportation system has to ensure the accomplishment of the transportation requirements. The transportation schedule sets forth the desired start and finish times for both directions of transportation and for each type of material transported. It also includes the number of shipments of various types with origin and destination nodes for each shipment. The possibility of achieving the transportation schedule depends upon the transportation system capacity, number and characteristics (e.g. speed and capacities) of available transportation devices as well as processing capabilities of the transportation system services (e.g. container wash stations). For some types of materials (e.g. food), the transportation times from central to terminal service station have to be within acceptable limits.

Taking into account the various materials that have to be transported by the system and the technological characteristics of their transportation, the following nine shipment types were identified:

1. Food for patients and return of their dishes
2. Food for personnel and return of their dishes
3. Departure of food remains
4. Clean and dirty linen
5. Sterile materials and return of materials for sterilization
6. Departure of waste
7. Different materials (main to process storages)
8. Different materials (process to main storage)
9. Other materials

Each of these shipments requires different kinds of transportation including special transportation nodes, modes of releasing vehicles, processing, number of processing cycle repetitions, etc. Each day more than 350 shipments have to be undertaken in order to fulfill the hospital transportation requirements.

The simulation study met the expectation of engineers and managers conducting the AGVS construction and enabled them to design and validate the hospital transportation system properly. The simulation study helped also to alter the preconceived plan of vehicle base positions for which it was shown that a higher vehicle base capacity was required.

During the whole simulation study, the simulation team had a number of meetings with the client's managers and engineers discussing the simulation study goals, AGVS operation logic, the simulation modeling approach, and the simulation results. At the end of the study, the clients accepted the results of the study, which became part of the hospital transportation system documentation. It was explicitly stated by the clients that the simulation modeling helped them both to acquire a new view of transportation system analysis and to obtain more efficient and reliable results than with the classical engineering approach. Since the hospital construction was finished more than six months after the AGVS simulation study, the implementation of the study results is expected in the hospital equipping phase which is planned in the near future.

Alternatives Considered: GPSS

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