This paper studies the properties of the zeros of sampled-data systems. Since the basic study by Åström et al. that showed there can exist unstable zeros that have no relevance to the original continuous-time plant, there have been various studies that circumvent this effect by introducing various techniques. The present paper studies zeros of sampled-data systems from the standpoint of lifting. We will show the following: a) such unstable zeros are an artifact induced by the combination of the zero-order hold and the synchronous sampling; b) such zeros disappear when considered in the lifted plant; c) further, such an effect can be bypassed by a multirate technique. We will also review relationships with the existing techniques such as two-delay control. Analysis of some examples is given.
All Science Journal Classification (ASJC) codes
- Control and Systems Engineering