Analysis of Temperature Controller in Thermal Chambers for Arbitrary References

Abstract

The temperature control of a thermoelectric module used in the construction of thermal cameras for the characterization of materials is proposed, including smart materials such as shape memory alloys, among others. A current amplifier controller model is used together with the corresponding model of the thermoelectric module and the thermal camera. This set is considered as a non-linear load with a variable impedance that must be controlled. In order to achieve effective temperature control, a temperature controller is implemented in the thermoelectric module designed in closed loop, thus ensuring the maintenance of the desired temperature. To measure the temperature in the thermoelectric module or in the chamber, a thermistor type sensor is used due to its fast response compared to other types of sensors. In the analysis of the temperature controller, various disturbances are taken into account, such as the ambient temperature that can vary between 15 and 35 degrees Celsius, the temperature range of the system between -10 and 100 degrees Celsius, the possibility of varying the impedance of the thermoelectric module, the delays produced in the thermistor response and the effect of the heat sink on the cooling temperature. A stability analysis is carried out for the temperature controller of the system in discrete time using the Root Locus method. The results of the transient response analysis demonstrate the effectiveness of the proposed controller. Simulations are presented showing how the system can cope with sudden or arbitrary temperature variations, and even follow sinusoidal references. Thisshows that it is possible to satisfactorily control the assembly consisting of the amplifier, the thermoelectric module and the thermal camera.