CONSTRUCTION OF A PROTOTYPE GREENHOUSE AND USE OF DISCRETE PROCESSING TECHNIQUES FOR TEMPERATURE CONTROL

Abstract

This article presents the construction of a prototype greenhouse and the development of an experimental temperature control system as an application of discrete control of a thermal system. The generation and control of temperature is present in the industrial environment, where there are various levels of complexity for the satisfactory use of thermal energy. The structure consists of a wooden box, a 60 W light bulb as a heat source and a cooler for cooling. The temperature was measured using a thermocouple sensor and the data was processed by an Arduino. The Least Squares Method was used to estimate the gray box of the temperature system in the form of a discrete-time transfer function. The conversion of temperature into sensor voltage was determined using mathematical expressions, which allowed the system to be calibrated. The results were promising, since this is a first-order thermal plant with hysteresis and the controller is generic. However, the experimental analysis of the temperature control proved challenging. The main challenge in the project was the existence of intrinsic hysteresis in this type of system. Its clear presence was observed at higher temperatures, as well as the difference between the lamp's heating speed and the cooler's response. Even so, the system maintained the temperature within the specified parameters. One proposal for improvement is to implement a power control for the lamp, to provide more gradual heating.