Temperature control based on a modified smith predictor for injectable drug formulations

This paper proposes a modified Smith predictor scheme for temperature control during the formulation of injectable drugs in chemical reactors. The dynamic model of this process is obtained from an identification procedure applied in a real chemical reactor of the pharmaceutical industry. This identification procedure yields a second order with dominant time delay transfer function. A PI controller combined with a modified Smith predictor is therefore designed which behaves robustly against the effect of measured or unmeasured external disturbances. Simulated results compare the performance of the proposed controller with a standard PI controller, also combined with a conventional Smith predictor, and with Astrom modified Smith predictor. Four performance indexes have been used in this comparison: three related to the output performance (settling time, overshooting, and IAE), and a fourth one related to the control effort (EU). The analysis of these indexes shows that the proposed controller provides lower values of the compared indexes.