A simple and intelligent nonlinear PID temperature control with ambient temperature feedback for nonlinear systems

Abstract

Modern day innovations for applications in Life Sciences and Health Care are revolutionizing the public healthcare sector. Long gone are the days when advanced diagnostics were available only for the elite. Bringing these advancements in diagnostics and medical analysis has become the prime focus of governments in developing and under developed countries where the risks of epidemics and poor hygiene are prevalent due to their supernumerary population. The PCR (Polymerase Chain Reaction) machine is one such invaluable tool in diagnostics that can be used to detect a variety of diseases and abnormal medical conditions. This paper presents a simple algorithm for nonlinear PID (Proportional Integral Derivative) temperature control of a Peltier based TEC (Thermo Electric Cooler) that incorporates an additional ambient temperature feedback for optimum operation in a variety of environments with different temperatures. The algorithm uses PID constants that are characterized using polynomial regression from a discrete database of measurements to choose the right value for the right target temperature. The ambient feedback has two roles. Firstly, it is used to divide the control region into two zones for optimum control. Secondly, it is used to slide the entire characteristic appropriately to provide seamless operation in a variety of thermal environments. The proposed algorithm can be used for easy temperature control with an overshoot of less than 0.1° C and an accuracy of +/- 0.1°C for any such similar system, without the mathematical rigor for modelling the entire system.