Robust indirect adaptive control of the electrohydraulic velocity control systems

A robust version of an indirect adaptive
control scheme with self-excitation capability to
the problem of controlling velocity of the
electrohydraulic servosystems subject to
unmodelled dynamics and load disturbances is
proposed. The scheme contains an effective
gradient least squares estimator using a dead zone
technique and a certainty equivalence based
adaptive controller. A design procedure for
synthesising the adaptive controller is formulated
by using the pole-placement technique, where a
signal is created and fed back to the control law
such that it has self-excitation capability and thus
the stability of the closed-loop control system can
be achieved. A series of simulations are
performed to demonstrate the effectiveness of the
proposed scheme. The results show that the
proposed scheme is fairly robust to the control
systems with uncertainties as well as improved
performance characteristics, compared with that
of the suboptimal PID control scheme with
constant feedback gain and that of the adaptive
model following control scheme.