This model illustrates the repetitive control concept. A servo drive system is selected as the case study. It should be noted that the very basic repetitive compensator introduces integration in the pass to pass direction. Such an approach is not robust. You just cannot do that in a physical control system. To observe possible consequences of doing that please set the forgetting factor gamma=0. The most simple, yet not the most effective, way to robustify the scheme is to use 0<gamma<1. This obviously replaces the pure integrator in the k-direction with a first-order lag element. The system is now more robust, however, its tracking performance has been compromised. More elaborate solutions involve frequency dependent forgetting, i.e. filtering of control signal. More on this will be available soon from Michal Malkowski -- check him out at Matlab Central in late December 2014. This submission does not contain any groundbreaking findings but we hope that some models co-authored by Michal and me will, so stay tuned :)