A Generalized Multi-Loop Controller With Enhanced Robustness and Its Design Guideline

Feedback control is ubiquitous in engineering applications and is a powerful tool to achieve automatic regulation of the outputs of a system. Existing closed-loop control methods typically employ a single feedback loop to regulate each output. This article proposes a new generalized multiloop control structure, which utilizes more than one feedback loops to control one output. The control performance of an existing single-loop controller can be boosted by closing extra feedback loops outside the original loop. The main advantage of the multiloop structure is enhanced robustness without necessarily sacrificing the stability and dynamics of the original control system. The proposed multiloop structure is a general control technique that can potentially be combined with any existing control methods. A straightforward design guideline for minimum-phase systems is provided to implement the multiloop controller and determine the control parameters. The proposed idea is illustrated with a power-factor-correction circuit and is validated in simulation and experiments.