Reliable control using equivalent transfer function for control system with multiple minor-loop

In this paper, a control method is proposed for minor-loop failure in a multi-loop control system. If a minor-loop fails, because of a problem with the sensor, the character of the whole system changes greatly and becomes unstable. For this situation the proposed method changes to a new compensator using an equivalent transfer function (ETF) after the minor-loop failure. The equivalent transfer function is designed so that it does not change the transfer function of the whole system before and after the minor-loop failure. Using this method, the stability of the control system in the minor-loop failure is guaranteed.