A model-based control strategy for batch coffee roasting processes using a novel controlled variable

Abstract

It is desirable that batch coffee roasters be fully automated. This article offers an automation solution for industrial practitioners in the coffee industry, namely a control strategy for rotating-drum batch coffee roasters. The control strategy can be applied to standard PI-PID controller systems to automate artisan coffee roasters. It can consequently be implemented with minor adjustments to artisan batch coffee roasters that are currently in use. Controller parameters were experimentally determined using IMC, Cohen-Coon, and ITAE-based parameter techniques, and they were validated using Simulink®. Bode plots confirmed controller stability. The roasting process was classified as a lag-dominant, first-order plus time delay process and approximated; therefore, it was modeled as a pure integrating system. The batch roasting process was successfully controlled using a novel controlled variable, namely the roast profile derivative, and a final control strategy that switches between two loops is proposed for real-world application.

Keywords

• Coffee roasting
• Model-based control
• PI-PID controllers
• Batch-roaster automation