  Non-linear discrete-time state-feedback regulators are widely used in passive
unidirectional systems. Offline system identification is required for tuning
parameters of these regulators. However, offline system identification is
challenging in some applications. Furthermore, the parameters of a system may
be slowly changing over time, which makes the system identification less
effective. Many adaptive regulators have been proposed to tune the parameters
online when the offline information is neither accessible nor time-invariant.
Stability and convergence of these adaptive regulators are challenging,
especially in unidirectional systems. In this paper, a novel adaptive regulator
is proposed for first-order unidirectional passive systems. In this method, an
associated search element checks the eligibility of the update law. Then, a
stochastic hill-climbing algorithm updates the parameters of the discrete-time
state-feedback regulator. Simulation results demonstrate the effectiveness of
the proposed method. The experiments on regulating of two passive systems show
the ability of the method in regulating of passive unidirectional system in the
presence of noise and disturbance.
