Sensitivity considerations for time-varying sampled-data feedback systems

A synthesis procedure for linear time-varying sampled-data feedback systems is described. Just as in the continuous system case, one of the advantages of feedback in a sampled-data system is that it can potentially reduce the effect of plant variations on the system performance. To a certain extent, load disturbance and instrument noise may be simultaneously reduced also. A time-domain sensitivity matrix is defined and used in the design of the digital compensators for prescribed insensitivity of the system to plant variation. In addition, two optimization criteria are presented for the design of these compensators when load disturbance and instrument noise have to be reduced as well. The procedure is also applicable to fime-invariant sampled-data systems.