IT—Information Technology: Simulation of Automatic Tray-unloading Operations for Rice Seedlings

In Taiwan, rice nursery centres widely adopt gantry transport systems for transferring seedling trays to/from the hardening field. To facilitate the loading and unloading procedures, a tray-unloading machine riding on top of a gantry has been developed which can orderly lay down the trays on the ground for field hardening and also pick up the trays of grown seedlings onto the loading conveyer in sequence when they are ready for transplanting. The whole system can be run automatically in an open field for seedling preparation. A simulation model for seeded tray-unloading operations by the automatic tray-unloading machine has been developed and verified with six operational conditions. Judging by the slight difference between the simulated and observed results, it was concluded that the model can accurately predict the real tray-unloading operations and, therefore, can be used as a tool for further sensitivity analysis on the maximum operation patterns. A model simulation for the total system was set up and analysed by various operation combinations. The results indicate that the system throughput can be increased from 771 to 957 trays h−1 with 20 trays in a working row which represents an increase of 24·8%. Longer working rows will result in higher system throughput. The simulated results show that the system throughput changes from 771 trays h−1 for 10 trays per row to 1140 trays h−1 for 60 per row, with a significant increase of 48%.