Abstract
Abstract— Due to the lack of advanced controller systems in post-harvest storage facilities, Ethiopia losses 30–40% of fruit and vegetables which adversely affect food security and economic growth. The objective of this research is to design and develop a self-tuning fuzzy PID control system by considering the needs of smallholder farmers in Ethiopia who produce perishable goods. The research provides an efficient and cost-effective system by utilizing a self-tuning fuzzy logic controller to adaptively adjust PID parameters tailored to varying environmental conditions of Ethiopia. The finding from MATLAB Simulink of the transient and steady state performance parameter for PID step response of temperature has the rise times of 0.4428 seconds, settling time is 0.8029 seconds, and settling max. is 22.0030 and overshoot is 0.0133%, while fuzzy PID step response of temperature has the rise time of 0.1495 seconds, settling time is 0.8003 seconds, settling max. of 22.0 seconds, and had 0% overshot. Furthermore, PID step response of relative humidity has the rise time of 4.7231 seconds, settling time is 8.4860 seconds, and step response of fuzzy PID of relative humidity has a rise time of 4.7316 seconds, settling time is 8.4821 seconds, and both controls had an overshot approximately to 0%. The controllers further validated to the sudden change of temperature and humidity by varying gain to ± 50%, and the self-tunning fuzzy PID controller track the desired setpoint with approximately zero error. The desired set points of 22°C and 93% humidity also successfully achieved in closed-loop experimental tests on developed prototype by adjusting airflow and water flow rates based on the feedback from ambient conditions of 28°C and 58% humidity. This research offers a robust solution for preservation agricultural produce, food and beverage, contribute agricultural engineering with potential applications in various storage and transportation environments.

Key words: Keywords— Experimental validation; Evaporative cooling system; MATLAB Simulink; Post-harvest Preservation; Self-tunning Fuzzy PID.