Persistency of excitation in continuous-time systems (Q1093599)

This paper derives time-domain conditions on the input of a linear time- invariant single-input continuous-time system, which are necessary and sufficient for the system state vector to be persistently exciting. The advantage of the present study over previous ones lies in its generality: the boundedness of the input is not assumed; in fact the input wave is not constrained in any way save for assuming it to be locally integrable. The paper adds a useful piece of information to the literature on ``persistency of excitation'' which developed rapidly in the past few years in relation to the active research in the adaptive control systems and their convergence and robustness properties.