1 - Adaptive internal model control

Abstract

Internal model control (IMC) schemes, where the controller implementation includes an explicit model of the plant, continue to enjoy widespread popularity in industrial process control applications. These schemes guarantee internal stability for only open loop stable plants. Because most plants encountered in process control are already open loop stable, this really does not impose any significant restriction. This chapter develops a systematic theory for the design and analysis of adaptive internal model control schemes. The principal motivation stems from the fact that despite the reported industrial successes of adaptive internal model control schemes, a design methodology capable of providing theoretical guarantees of stability and robustness does not currently exist. The ubiquitous certainty equivalence principle of adaptive control is used to combine a robust adaptive law with robust internal model controllers to obtain adaptive internal model control schemes that can be proven to be robustly stable. Specific controller structures considered include those of the model reference, “partial” pole placement and optimal control types.