Main Article Content
This paper deals with comprehensive robust stability study of a thermal control system encompassing time-invariant communication delays. First, a precise approach is proposed for determining the stable margin/delay margins based on control and system parameters. This approach takes the gain margin (GM) and phase margin (PM) into account. The technique employs a deletion process to convert the transcendental characteristic equation to a new polynomial with a complex plane crossing frequency. The new polynomial equation's positive/real roots are equivalent to the original characteristic equation's purely complex roots. The second approach employs a straightforward graphical approach for determining the stabilizing region of PI control parameters for a given time-invariant delay. The technique is essentially a method for locating the stable region and the Stability Boundary Line (SBL) in the space parameter of a PI controller with user-defined gain and phase margin (GMPM). Extensive simulation studies demonstrate that the proposed techniques provide significantly improved dynamic performance compared to previous results for a thermal control system with time-invariant communication delays.