Robust stable speed control system based on doubly coprime factorization and disturbance observer

For the purpose of realizing a high performance robust servo system, the conventional control system is often designed by disturbance observer. However, when the frequency band width of disturbance rejection characteristics is narrow, this control system sometimes does not maintain the robust stability. In order to overcome this problem, this paper proposes a new two-degrees-of-freedom control system which considers the robust stable condition and the disturbance rejection characteristics systematically. The structure of the proposed system is based on doubly coprime factorization and disturbance observer. In this paper, it is applied to the robust speed control system of DC servo motor. The experimental results show that the proposed speed control system well regulates a motor speed robustly for wide speed range, in comparison with the conventional robust speed control systems.