Synthesis and critical study of sampled-data control systems

In the last few years, there have been few papers1¿9 which discuss methods of analysis and synthesis of sampled-data control systems. In this paper it is shown that the z-transform method is the best as applied to the design of such systems. The z-transform method yields information only on the response of the system at sampling instants. Certain methods have been introduced which modify the z-transform method to obtain information on the system´s behavior between sampling instants. All these proposed methods are mainly directed for analysis purposes. However, none is applied for design procedures which can be consolidated with the z-transform method. In this work, the modified1 z-transform method is further extended and applied for synthesis procedures. It is believed that the method chosen is best applicable for the design of sampled-data control systems. Both the frequency-response and the root-locus approach with the use of this modified z-transform method are discussed. Furthermore, the effect of pole and zero location on the transient response of sampled-data systems is investigated, and certain information on the response obtained.