Nonlinear control of an evaporator using an error trajectory technique

This paper outlines the successful application of an adaptive control method in an industrial environment. The control strategy incorporated MRAC (Model Reference Adaptive Control) using an adaptive PID where the adaptive parameter was estimated using a macroscopic energy balance over the control zone based on the concept of a tracking error trajectory. Success is demonstrated in a plant for sugar production where the formation of candy, due to incorrect management, the steam flow to the evaporators prevented the sugar syrups leaving the system to pass to the centrifugal screens. This stopped production three or four times a day for 30min, leading to serious problems in relation to cost and quality, the evaporators being very sensitive to temperature changes.