Development of a fuzzy controller for tubers post-harvest storage system

Abstract

In many countries, substantial amount of agricultural products, including root and tuber crops, which cannot be consumed, processed, commercialized, transported or exported are produced on daily basis. However, facilities for adequate and efficient post-harvest storage and preservation of these products are not readily available, especially in most developing countries, resulting in considerable losses. Hence, the need for improved, adequate and efficient food storage and preservation systems. Nowadays, traditional methods for post-harvest storage and preservation of tropical roots and tubers such as yam barn, underground pits, leaving matured tuber buried in the ground until need arises, and trench silos are employed for the storage and preservation of these crops. Unfortunately, all these storage techniques leads to undesirable results as the stored products are susceptible to uncontrollable environmental conditions such as temperature and relative humidity, which leads to significant losses, reduction in quality and quantity of the products as well as their market prices. Sustaining appropriate temperature and relative humidity of the storage environment is crucial to achieving better storage objectives. However, at present, only few studies have utilized the unique advantages of intelligent techniques to improve the conditions of indigenous roots and tubers post-harvest storage and preservation system. An intelligent post-harvest tropical root and tuber crops storage system is proposed and developed in this research work. The post-harvest storage system adopts the fuzzy logic control (FLC) strategy for optimum control of temperature and relative humidity of selected tropical tuber crop. In this thesis, yam (Dioscorea spp.) is considered for optimum control of its storage temperature and relative humidity (tracking of its desired storage temperature and relative humidity). In order to maintain optimum storage conditions, forced-air cooling is employed to ensure proper ventilation within the storage compartments. Temperature and relative humidity sensor was used to determine the property of the conditioned air supplied by the cooling system and provides necessary feedback. To test the performance of the intelligent controller for keeping the produce (yam tubers) storage temperature and relative humidity requirements within acceptable range, simulation studies were carried out in MATLAB/SIMULINK simulation environment and experimental validation on existing post-harvest tropical food storage system prototype using DSP chip as interfacing module was performed. Results obtained show that the developed controller is able to track the desired temperature and relative humidity set-points for each product under storage with a settling time of 5.6s and 4.63s respectively, and responds accordingly to input disturbances to ensure better storage objectives are achieved successfully.