Generalised hold functions for fast sampling rates

It is well-known that generalised hold functions can be used to shift the zeros of sampled-data models for continuous-time systems. In this paper, we consider the use of generalised holds to deal with sampling zeros only. We propose a hold design that places the sampling zeros asymptotically to the origin, when the sampling period tends to zero. The resulting generalised hold is only a function of the process relative degree. We also investigate the robustness of the procedure with respect to both finite sample periods and unmodelled plant dynamics.