This study is directed toward establishing a DDCalgorithm which gives better control performance than the usual analog PID controller. The fundamental concept of this DDCalgorithm is based on the minimal prototype algorithm. Its control seems to be ideal, but the response has a hidden oscillation. The reason is that the control works too rapidly on the manipulated variable to settle to the reference value. In this paper, the desired response is madeto settle slowly to the reference value, that

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... s, it needs one or more samplings comparedwith the minimal prototype algorithm. This nonminimal algorithm has one or two adjustable parameters, like the analog PID controller. With suitable values of these parameters the nonminimal prototype DDC algorithm shows excellent performance compared with the analog or the discrete digital PID. These adjustable parameters are optimized for the 2nd-order system with time delay and are related to the process parameters. Once approximate values of the process parameters are known, the optimumDDCcan then be obtained.