Closed loop analysis of control systems under scarce measurements

In this paper, the analysis of the closed-loop dynamics of a control system with scarce random sampling is addressed. The control strategy is based on the use of a conventional single-rate controller combined with a model based output estimator that estimates the unmeasured intersampling outputs at the control (fast) rate. The proposed estimator takes into account the past measured outputs, as a difference with inferential control schemes. The separation principle between the estimator dynamics and the closedloop one is demonstrated. The design of the control system is simplified, since the controller and the estimator can be designed separately. Some examples illustrate how an adequate estimator design improves the closed-loop performance with respect to the inferential control scheme (open loop estimator), solving the problem of instability that appears when the open loop system is unstable.