3.3. Instantaneous harmonic control
This control law originates from the standard HC
(Fuller et al., 1995), whose biggest drawback is the
slow convergence resulting from the requirement to
wait for a steady state before updating the control
effort (Daley et al., 2008). This problem is addressed
and overcome in the IHC approach. The IHC was initially
proposed by Knospe et al. (1997) as a frequency
domain adaptive control law and was later revised by
Daley et al. (2008) and Tammi (2007) with some modifications
and different names (convergent control (CC)
and IHC). The derivation of the control law is done in
the frequency domain, where it can be considered as a
frequency domain adaptive feedforward control law.
The structure and the goal of the control law are
rather simple. Firstly, the instantaneous estimates of