Comparative Assessment of PID Controller Tuning Methods for Coffee Roasting Process

Mohamad Taib Miskon, Mohd Hezri Fazalul Rahiman*, Mohd Nasir Taib Ramli Adnan

Abstract

Time-temperature progression of a batch of coffee beans during roasting has been one of the most critical parameters. The roast operator uses it to replicate particular flavour profiles that come to their mind.  Therefore the replication of the temperature progression is done mainly using a widely available PID controller. However, the controller is rarely optimized to its best performance due to the difficulty of the PID parameter tuning. This paper presents a comparative performance evaluation of PID controller design using different tuning methods, including Ziegler-Nichols, Cohen-Coon and approximate M-constrained Integral Gain Optimization (AMIGO). The evaluation includes step responses, set-point tracking and disturbance rejection aspects of the controller. The performance indices used in this work incorporate rise time, per cent overshoot, settling time, and integral indices, including ISE, IAE and ITEA. Simulation results indicated that PID-AMIGO had been the best performing controller in all performance assessments except for slow varying set point tracking. The PID-CC controller offered better performance than the PID-AMIGO controller with a 99.8% and 92.5% improvement of the ISE and IAE index, respectively, subject to ramp input.