FREQUENCY-DOMAIN IDENTIFICATION OF LINEAR TIME-INVARIANT SYSTEMS UNDER NONSTANDARD CONDITIONS

This paper presents a frequency-domain identification method for param etric transfer function models of linear time invariant systems that t akes into account the nonzero initial condition and/or the transient e ffects in the response of the system when excited by periodic or time- limited signals. The method is useful for systems with large settling times where it takes too much time for the system to reach a steady st ate so that measurements can begin. In the special case of free decay experiments the presented technique is a frequency-domain version of f itting exponentially damped sinusoids embedded in noise, The theory is illustrated by simulations and a real measurement example.