Generalized multi-scale control scheme for cascade processes with time-delays

• Generalized cascade multi-scale control (CMSC) scheme is proposed.
• The scheme is applicable to stable and integrating/unstable dead-time cascade processes.
• The scheme provides improved nominal performance/performance robustness.
• Numerical studies show the applicability and usefulness of the CMSC scheme.

The cascade control is a well-known technique in process industry to improve regulatory control performance. The use of the conventional PI/PID controllers has often been found to be ineffective for cascade processes with long time-delays. Recent literature report has shown that the multi-scale control (MSC) scheme is capable of providing improved performance over the conventional PID controllers for processes characterized by long time-delays as well as slow RHP zeros. This paper presents an extension of this basic MSC scheme to cascade processes with long time-delays. This new cascade MSC scheme is applicable to self-regulating, integrating and unstable processes. Extensive numerical studies demonstrate the effectiveness of the cascade MSC scheme compared with some well-established cascade control strategies.