A communication disturbance observer with a band-pass filter for delay time compensation

A delay time in a feedback control system deteriorates stability and performance. So, Smith predictor or communication disturbance observer (CDOB) has been proposed to compensate the dead time. However, Smith predictor requires the models of a plant and a dead time. Although the CDOB does not require the model of the dead time, the modeling error of the plant causes a steady state error against a step input. To avoid the steady state error, this paper proposes a novel CDOB using a band-pass filter. The proposal method has an effect to reduce the error against a step input, ramp input, or acceleration input.