The self-tuning robust servomechanism problem with control input constraints

In this paper, which is an extension of [1], we present a self-tuning regulator for an unknown, asymptotically stable, linear, time-invariant, multivariable plant which will carry out asymptotic error regulation for constant references and disturbances under a constraint on the amplitude of the applied control signal. The only assumptions made about the plant are that it has no transmission zeros at the origin, that it has as many inputs as outputs, and that an estimate of the steady-state DC gain matrix is available in the case when the plant has more than one output. The self-tuning regulator consists of a multivariable integral compensator together with a tuning mechanism which "tunes" the parameters of this compensator. It is shown that for a "large" class of constant reference and disturbance signals, asymptotic error regulation occurs. Several simulation examples are included to illustrate the behaviour of the controller when applied to "unknown" plants.