Approximate models to describe real sampling and hold processes based on multirate sampling techniques

We present an explicit description of an innovative technique to treat the real sampling and hold method by considering a real finite pulse instead of an ideal one to sample the signal. Fractional-order sampling and hold devices are considered in general while including the zero-order hold and the first-order hold as particular cases. The discrete model obtained leads to an increment of the degrees of freedom. Therefore the proposed technique may be very useful in adaptive control to improve the stability of the discrete plant zeros. This model affords better results than the one based on the traditional ideal sampling. In addition, the use of multirate sampling, with a fast sampling rate being used to approximate the continuous signal during the real sampling pulse, provides a simple technique to deal with other multirate problems