Relay feedback method under large static disturbances

None of the previous relay feedback methods can provide a desired cyclic steady state in the case of large static disturbances, of which the magnitude is bigger than the magnitude of the relay. The proposed relay feedback method overcomes this limitation by placing a relay before a proportional-integral (PI) controller of which the integral part plays an important role in rejecting the large static disturbances. This is very attractive from a practical point of view because we do not need to define deviation variables in order to apply the proposed relay test. Furthermore, the proposed method can provide the frequency data of the process for a pre-specified phase angle by adjusting the integral gain.