Robust model predictive control of processes with large uncertainty in deadtime

A theoretical formulation of the deadtime window approach to deadtime compensation is presented and investigated. The central idea in this approach is to use a specified uncertainty band in the deadtime to create a time domain uncertainty window. The feedback signal is changed only if the measurement is outside the expected region. Simulations results for the closed-loop integral square error as a function of model parameters and controller parameters compare the expected performance of the proposed approach to standard deadtime compensation structures. For a perfect model of the deadtime-free part of the process and step changes in disturbances or the set point value of the output, the controller in the deadtime window structure need not be de-tuned to compensate for uncertainty in the deadtime, as long as the true process deadtime is within the specified uncertainty region. In a more general sense, these results show that the proposed approach can be used to favorably affect the classic tradeoff between performance and robustness.