Inference of thermal models for sensors

The presence of thermal diffusivity in a spherical thermal anemometer gives it long-memory dependence. The identification problem and state realisation of this model is addressed by using diffusive representation (DR). In order to do that, an ideal thermal sphere quadrupole model and its corresponding finite differences model are proposed and simulated. From those models and the non-rational Cole-Cole transfer function, the identification problem is discussed. PRBS as an input signal is also discussed. The best choice in the number of poles and their position is found by analysing frequency response. For the 5 decades bandwidth used here, it has been found that 8 poles geometrically spaced by a scale factor of 5 is a good choice. Finally, 8 poles DR is verified as a good option to model a complex spherical thermal anemometer prototype which is being developed in Universitat Politècnica de Catalunya, by means of open loop and sigma-delta closed loop control simulations

Heat flow dynamics in thermal systems described by diffusive representation

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 time-varying 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 systems described by any arbitrary number of poles. This allows for the first time the analysis of lumped and distributed systems without any limitation on the number of poles describing it.Peer ReviewedPostprint (author's final draft

Inference of thermal models for sensors

The presence of thermal diffusivity in a spherical thermal anemometer gives it long-memory dependence. The identification problem and state realisation of this model is addressed by using diffusive representation (DR). In order to do that, an ideal thermal sphere quadrupole model and its corresponding finite differences model are proposed and simulated. From those models and the non-rational Cole-Cole transfer function, the identification problem is discussed. PRBS as an input signal is also discussed. The best choice in the number of poles and their position is found by analysing frequency response. For the 5 decades bandwidth used here, it has been found that 8 poles geometrically spaced by a scale factor of 5 is a good choice. Finally, 8 poles DR is verified as a good option to model a complex spherical thermal anemometer prototype which is being developed in Universitat Politècnica de Catalunya, by means of open loop and sigma-delta closed loop control simulations