The parameters of the controller (55) are tuned for a particular
operating point. It would be possible to schedule the parameters
according to some signal, e.g. fuzzy gain scheduling could easily be
implemented as reported by many applications in [38]. The results
of experiments have shown that the system behaves quite robustly
with fixed parameters (55). Also, since the controller design was
not the primary objective of the paper, the parameters are fixed in
our approach.