Two-Channel Relay Feedback Method under Static Disturbances

We propose a two-channel relay feedback method in order to guarantee a prespecified phase angle of the estimated model under a large input disturbance of which the magnitude is possibly bigger than the magnitude of the relay. The proposed method uses the conventional relay followed by two channels, a proportional channel and an integrator plus relay channel. The ratio of the two gains of the two channels specifies the phase angle of the estimated model. We do not need to define deviation variables initially before we apply the proposed relay feedback method, which is very attractive from a practical point of view.