Frequency domain identification of transfer function model of a disk drive actuator

In this paper, we present a method of identifying the transfer function model of a linear time-invariant (LTI) dynamic system from its frequency response data. The presented algorithm is based on the principle of least-square fit on the complex plane. It fits the frequency response data to the response of a transfer function model, minimizing the sum of square of residual errors. Thus a transfer function model is extracted from the measurement of the frequency response at a discrete set of frequencies. We select the order of the transfer function model through the interpretation of the cost functions obtained from least-square estimation (LSE) for different orders of the transfer function.The effectiveness of the proposed technique is verified by estimating the transfer function model of a hard disk drive actuator.