Online monitoring of controller performance from servo information

With the recent advent of relay feedback technique, a number of relay based online monitoring procedures has been reported. However, the range of their application may be constrained due to the two inherent limitations: 1) the relay experiments may interfere with the process to a certain extent; 2) some of nonlinear systems may fail to present the indispensable stationary oscillations. In this work, a set point change based method is proposed, which can not only overcome such limitations but also cut down the long computing time and trivial experiment procedures. Simulation examples demonstrate the successful applications of proposed method to both linear and nonlinear systems