Empirical modelling, simulation and control of coffee brewing

Coffee brewing is a complex process governed by various parameters, such as water temperature, extraction time, and particle size of ground coffee. These parameters affect the quality of brewed coffee in terms of flavour and intensity of aromatic compounds. This research focused on studying the effect of water temperature on caffeine concentration in brewed coffee. This was done by varying the water temperature (80°C, 85°C and 90°C) in infusion coffee brewing while keeping other parameters such as coffee type (Arabica), coffee particle size (500 µm), and coffee-to-water ratio constant. The results showed that the concentration of caffeine in the brewed coffee increased as the water temperature increased, with the highest concentration observed at 90°C with 210.58 g/L. An empirical model, represented as a first-order model with time delay (FOPTD), was developed to study the effect of temperature in the brewing process. The model was then simulated and controlled using a Proportional Integral (PI) controller tuned using different methods. Performance and robustness analysis were conducted, and the best results were obtained using the fractional-order controller with an Integral of Absolute Error (IAE) of 64.67. In conclusion, the effect of water temperature on caffeine concentration during coffee brewing was determined, and a brewing model at different water temperatures was developed and simulated with different tuning rules for the PI controller.