Optimal Temperature Control Scheme for Milk Pasteurization Process Using Different Tuning Techniques for a Proportional Integral Derivative Controller.

Milk is one of the important dairy foods, which forms an essential building block in the feed formulation for infant and growing children, and adults alike. However, the quality of the final product largely depends on the temperature of the pasteurization process. It is, therefore, a necessity to ensure that optimum temperature is maintained during pasteurization process, as over-temperature kills all the essential nutrients contained in the final product and similarly, low temperature is not desirable as the final product will not yield the desired nutritional value. As a result, the application of optimal temperature control scheme is a critical requirement for milk pasteurization. It is, on this background, that this paper presents the use of a Proportional (P), Integral (I), Derivative (D) abbreviated as PID controller for optimal control of temperature in the milk pasteurization process. The milk pasteurization temperature was modeled based on the first law of thermodynamics, while three different tuning techniques namely; Zigler-Nichols (ZN), Chien-Hrones-Reswick (CHR) and Cohen-Coon (CC) were employed to tune the PID controller for optimal control of the milk pasteurization temperature. The control schemes were simulated in MATLAB/Simulink, and the performance of each tuning technique was evaluated using the rise time, settling time, peak amplitude, and overshoot. Results showed that ZN tuned PID controller gave the lowest rise time, settling time, and peak amplitude of 0.177s, 0.34s, and 0.993, respectively, while the lowest overshoot of 0% was attained by both ZN and CHR. Based on these results, CC tuned PID controller exhibited moderate rise time of 1.02s, settling time of 6.49s, and overshoot of 5.67%, indicating that its performance is comparatively preferred with respect to other tuning techniques investigated. The results of this research find application in diary industries as it provides insight into the appropriate tuning technique for the PID controller to ensure optimum temperature control during milk pasteurization. [ABSTRACT FROM AUTHOR]

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