Chemical Engineering Research & Design, Vol.86, No.A2, 153-163, 2008
Minimizing the effects of unmeasured disturbances in an open-loop unstable chemical plant containing measurement dead times
The dynamic behavior of many processes is characterized by time delays due to measurement delays, which put strict limitations on the performance of the control system. In this paper a time-delay factorization strategy for the nonlinear model predictive control (NMPC) and state estimation of multiple-input multiple-output (MIMO), nonlinear, open-loop unstable processes having output-measurement delays, and subject to unmeasured disturbances is proposed. At first, the NMPC algorithm based on a nonlinear programming approach is presented. Then, on-line parameter-identification and state-estimation schemes are combined with the NMPC algorithm to maintain the process at a steady-state which is unstable for the open-loop system. Finally, the effectiveness of the proposed method is demonstrated via simulation on the control of a catalytic continuous stirred tank reactor (CSTR). (c) 2007 The Institution of Chemical Engineers. Published by Elsevier B.V. All rights reserved.
Keywords:prediction;estimation;nonlinear programming;dynamic optimization;collocation on finite elements;nonlinear model predictive control;measurement dead times;open-loop unstable systems;unmeasured disturbances