Pulse-compression probing of small signal characteristics for nonlinear systems in dynamic operating conditions

This paper is concerned with real-time monitoring of a nonlinear system using pulse-compression probing, which evaluates the pulse response produced by compressing a small elongated random probing sequence around an operating point. The focus is to study the extent and the condition under which the pulse-compression principle is upheld when the system undergoes transients between equilibria. The paper uses an incremental, linear time-varying representation of the nonlinear system not only to establish the validity of the pulse-compression principle under the uniform bounded-input bounded-output condition, but also to assist in determining the parameters of probing signals. Using the incremental representation, probing outputs are accurate regardless of knowledge about the trim condition. The results from pulse-compression probing in the longitudinal axis dynamics of the NASA Generic Transport Aircraft Model (GTM) are reported. The probing algorithm proves effective during changing operating conditions caused by a thrust command and by stuck faults in the outer elevators.