Characterization of Thermal System Performance for Control Applications Using TMG Finite Element Simulation

Successful implementation of temperature control is required in a variety of engineering applications. This paper presents a method for using the TMG finite element thermal solver to characterize the control system performance of a thermal model. Based on the results of a finite element simulation, an appropriate control system compensator may be designed to achieve desired thermal performance.

In order to apply the principles of control theory to a real world system, the response characteristics (i.e., transfer function) of that system must be adequately understood. The transfer function of a system may be derived from its frequency response profile. In order to determine the frequency response of several sample thermal systems, finite element models were constructed using IDEAS, and their thermal behavior was analyzed using the TMG thermal solver. A custom user-defined subroutine was written to interface with the TMG solver and generate Bode plots (frequency response curves). Based on these numerically generated Bode plots, transfer functions could be derived for the sample thermal models, and appropriate control system compensators could be designed using control theory approaches including the root-locus method and the Nyquist stability criterion.

The issues and challenges associated with generating a finite element-based Bode plot are investigated. Numerical accuracy of TMG simulation-based frequency response curves is assessed through comparisons with exact analytical solutions for each sample thermal system.