On applying a generalized Pade approximation to stability analysis - experimental results

The paper verifies by means of experiments the applicability of the generalized Pade approximation of the dead time to stability analysis (estimation of stability margins of the closed-loop system). Initial research carried on the topic revealed that there is a range of fractional orders of the generalized approximators, where the results obtained from fractional-order analysis give conservative results, and the approach is comparable to standard Pade approximation. In the paper, author aims at verifying this on the basis of experiments conducted with the use of FOMCON toolbox to implement fractional-order operators, and the Inteco Modular Servo System, comparing the identified model of the servo drive with added artificial open-loop delay, and the behaviour of the real closed-loop system. The analysis of the use of the generalized approximation, as well as application to a hardware-in-the-loop control problem, is the main novelty of the paper, since all prior approaches of various authors concentrated on time-domain analysis of the generalized approximator, not on stability issues.