On-line thermal regulation of a capillary pumped loop via state feedback control using a low order model

This study focuses on the regulation of a two-phase capillary pumped loop. The aim is to adjust the temperature and therefore the pressure in the reservoir in real time in order to reject the disturbance which occurs in the evaporator due to high-power cycles of electronic equipment. Regulation is achieved through a state feedback approach, which appeared to be very efficient for other fields of application. A very fast model of the thermal behavior of the loop is required. Low order models are elaborated via the Modal Identification Method. This model, built from in situ measurements, is valid around a nominal operating point where we can consider the behavior of the loop linear. A Kálmán filter is introduced in order to estimate the state of the system in real time. Two types of disturbance are considered: a slow and a fast one, in order to simulate a real power cycle. Results show that the control of the evaporator temperatures, adjusting the reservoir temperature, is quite satisfying when the disturbance variations are smooth in time. In this case, the objective, which is to limit the temperature variations at the evaporator, in order to avoid deterioration of the high-power electronics, is reached.