Sequential Multisine Excitation Signals for System

Linear system identification of complex nonlinear systems, such as large space structures, can be difficult because such systems are often lightly damped, have dense modal spacing, respond to disturbances over a large frequency bandwidth, and exhibit nonlinear responses. Many excitation signals used to collect frequency response data for linear system identification are poorly suited to systems that exhibit nonlinear responses. Specifically, random noise, burst random noise, pulse-impact, and multisine excitation signals can create undesired nonlinear distortions in the frequency response data that are generally indistinguishable from the linear frequency response. Thus, sine dwell (also called stepped sine) excitation signals are often used to obtain frequency response data since sine dwell excitation signals allow the base tone response to be separated from higher order harmonics. However, sine dwell testing can be very time consuming. In this paper, we present a novel sequence of multisine excitation signals that are more time efficient than sine dwell excitation while eliminating the effects of nonlinearity induced harmonics from the frequency response data. The sequential multisine excitation signal is demonstrated on the Deployable Optical Telescope testbed at Air Force Research Laboratory.