Synthesis of Sampled Data Control Systems by Time Delay Approximation

Abstract

In this paper, a synthesis of sampled data control system by continuos compensating networks is described. In this method, the sample and hold operation of the system is replaced approximately by a pure time delay of half a sampling period, then, appling the “Roots Specifying Method”, parameters of a compensating networks of the approximated system are calculated to achieve specified roots which satisfy the specified response. To show this procedure concretely, an illustrative example is considered.
The accuracy and the limitation of this method are also discussed and it is obtained that the compensating table and compensating chart which have been prepared already for continuous system synthesis can be used to simplify compensating calculation and residue limit can be also used as in continuous system.
As a conclusion, specification can be satisfied within 10% error, when the product of actual angular frequency and sampling period is smaller than 90°, by this method.