Transfer function identification in a fast steering mirror system

A transfer function identification method is provided. In combination of nonlinear least squares curve fitting and choosing the initial parameter based on the transfer function model, this method implements curve fitting for different sections with different frequency characteristics. With this method the frequency characteristic of complex control system can be converted to accurate transfer function, thus ±1dB magnitude and ±1degree phase measurement accuracy of transfer function can be obtained in low and middle frequency range. The digital compensator based on the identified transfer function not only effectively eliminates the mechanical resonance but also expands the closed loop bandwidth of the system. The identification of transfer function can facilitate the design of a digital compensator to get rid of manual debugging and provide complex digital compensator for a high performance control system.