Model-Free Control for Greenhouse Automation with Hardware-in-the-Loop and Raspberry Pi Implementation †

This paper presents the design, implementation, and experimental validation of a model-free control strategy for greenhouse climate automation. The proposed approach integrates a real-time embedded controller based on a Raspberry Pi within a Cyber-Physical System (CPS) framework. A Hardware-in-the-Loop (HIL) simulation architecture was developed, where the physical controller interacts with a high-fidelity digital twin (DT) of the greenhouse modeled in MATLAB/Simulink. This configuration allows a realistic assessment of the control performance, enabling the evaluation of system dynamics, actuator limitations, and response to disturbances before actual deployment. The control strategy is based on an intelligent Proportional–Integral (iPI) model-free algorithm, which avoids reliance on explicit process modeling and is well-suited for nonlinear and time-varying environments. Experimental results demonstrate the effectiveness, robustness, and practical feasibility of the proposed approach for real-time greenhouse automation. The use of low-cost hardware and the modular nature of the system make it scalable and attractive for precision agriculture and educational applications.