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Abstract
Test Problem 1. This problem involved the combination of flow and level control. The results obtained using the PD, PID, and DI controllers are discussed. With this problem, the tunable parameters K^sub p^, K^sub i^, and K^sub d^, which are very sensitive, were obtained using the Ziegler-Nichols method (Ziegler & Nichols, 1942). The values for ultimate gain (K^sub u^) and period of oscillation (P^sub u^) were 0.001 and 750, respectively.