Heat Flow Dynamics in Thermal Systems Described by Diffusive Representation

Abstract

Abstract-The objective of this paper is to analyze the dynamics of heat flow in thermal structures working under constant temperature operation. This analysis is made using the tools of sliding mode controllers. The theory is developed considering that the thermal system can be described using diffusive representation. The experimental corroboration has been made with a prototype of a wind sensor for Mars atmosphere being controlled by a thermal sigma-delta modulator.This sensor structure allows to analyze experimentally the timevarying case since changes in wind conditions imply changes in the corresponding thermal models. The diffusive symbols of the experimental structures have been obtained from openloop measurements in which pseudo-random binary sequences of heat are injected in the sensor. With the proposed approach it is possible to predict heat flux transient waveforms in many applications.

Thermal dynamics modeling of a 3D wind sensor based on hot thin film anemometry

“…The objective of this paper is to obtain time-varying thermal dynamics models using recent aplication of Diffusive Representation (DR), [1], of a proof of concept prototype of the REMS (Rover Environmental Monitoring 5 Station) wind sensor. The REMS sensor suite is an instrument from the Mars Science Laboratory (MSL) on board the Curiosity rover that landed in Mars in 2012.…”

“…A first analysis of heat flow dynamics described by diffusive representation in a hot thin film anemometer was described in [1], where thermal models were obtained for a spherical 3D wind anemometer for different wind velocities. These models provide the temperature dynamics of the components of the system under study as a function of the power delivered to the heat sources.…”

“…These state-space models have proven to be very well suited for thermal applications [9]. In [1], each thermal dynamics model was 75 extracted from a constant wind speed experiment. In this paper, however, the method is different, as the thermal dynamics models are extracted from a single experiment with wind velocity switching due to the working principle of the wind tunnel used.…”

“…For the experimental setup, a five meter linear wind tunnel has been used. The wind tunnel 95 operation mode is different from the hypobaric chamber used in [1] where a fan set the wind velocities. In this case, the tunnel has a rail inside where the sensor is positioned.…”

“…In this paper, the analysis of the closed-loop dynamics has been undertaken using the tools of equivalent control, typical of sliding mode controllers for the infinite sampling frequency approximation. These types of controllers alter the dy-215 namics of the system by applying a discontinuous control signal so that under some conditions the system 'slides' on a certain control surface [1,15]. For the general case of finite order thermal systems, the following control surface is defined:…”