The Dahlin controller is studied in the complex-frequency domain in terms of performance and robust stability. Several well known digital control algorithms are compared with the Dahlin controller and found to be equivalent to it. The possibility of extending the Dahlin controller to the control of plants with zeros outside the unit circle and unstable plants is discussed. The essential cause of ringing is investigated and some ambiguous formulation is clarified. A new procedure is developed for digital controller design. Compared with conventional methods, it provides a more effective method of eliminating ringing. Finally, numerical examples are given to illustrate the new approach.

In this note, the static output feedback simultaneous stabilization problem is addressed using a matrix inequality approach. A necessary and sufficient condition for simultaneous stabilizability of r proper MIMOplants via static output feedback is obtained. It is proven that the existence of a stabilizing feedback gain which simultaneously stabilizes this set of plants is equivalent to that of the solution of a set of coupled quadratic matrix inequalities. An iterative LMI (ILMI) algorithm based on the linear matrix inequality technique is proposed to obtain the feedback gain. Illustrated examples show its effectiveness.

The paper deals with the robust H∞ control problem for uncertain linear systems with multiple state delays. The parameter uncertainties are time varying and unknown, but are norm-bounded, and the delays are time varying. Based on the LMI approach, a new method for designing a robust memoryless state feedback control law is proposed to stabilise this class of uncertain time-delay systems, and to reduce the effect of the disturbance input on the controlled output to a prescribed level for all admissible uncertainties. The results depend on the size andthe varying rate of the delays and may be less conservative.

ln this paper, the conventional Smith predictor is modified, which leads to significant improvements in its regula- tory capacities for reference inputs and disturbances. The proposed modification utilizes the existing prediction of the conventional time delay compensator and decouples the set- point response from the disturbance response. The setpoint response and the disturbance response of the closed-loop system are adjusted by two parameters, respectively. This allows the designer to optimize them simultaneously. Illustrative examples are provided to show the advantages of the modified scheme.

The optimal service control of an unreliable manufacturing system with random demands is discussed. The system can produce many part types. The objective is to find an optimal policy to minimizing the expected discounted inventory and backlog cost. Structural properties of the optimal control are investigated. It is shown that the optimal policy is of switching structure. For producing one part type case, the optimal control is a threshold policy. For producing two part types case, the optimal control can be described by three monotone switching curves and its asymptote properties are derived. Numeric examples are given to demonstrate the results,