FFT-based monitoring procedure for intelligent control

Performance monitoring plays an important role in intelligent control system. A Fast Fourier Transform (FFT)-based monitoring method is proposed. Compared with the previous monitoring methods, it has several advantages. Firstly, it is a frequency domain method, which can evaluate the performance of the controller before the disturbance comes into the system. Secondly, the method is very effective and convenient, and the testing time can be saved greatly, since only one ideal relay experiment is involved. Lastly, the frequency search range for on-line identification of maximum closed-loop log modulus (L c,max ) is extended, whereas Chiang and Yu's method (1993) is restricted to the third quadrant. Simulation also shows that the proposed method can handle the process noise to some extent. All these features will make this FFT-based monitoring method very attractive in the intelligent control area.