On positivity and stability of a class of time-delay systems

In this paper, the properties of positivity and stability dependent on and independent of the delays as well as the closed-loop stabilization under linear feedback of continuous-time linear time-invariant multi-input multi-output dynamic systems subject to point constant delays are discussed. A main attention is paid to provide joint stability and positivity results which are shown to be conflictive objectives in the general case. Links with positive realness are given for the single-input single-output case. Illustrative examples are also given.