Feedforward Tracking Controller Design Based on the Identification of Low Frequency Dynamics

Several methodologies are proposed for identifying the dynamics of a machine tool feed drive system in the low frequency region. An accurate indentification is necessary for the desing of a feedforward tracking controller, which achieves unity gain and zero phase shift for the overall system in the relevant frequency band. In machine tools and other mechanical systems, the spectrum of the reference trajectory is composed of low frequency signals. Standard least squares fits are shown to heavily penalize high frequency misfit. Linear models described by the output-error (OE) and Autoaggressive Miving Average with eXogeneous Input (ARMAX) models display better closeness-of-fit properties at low frequency