TWO KINDS OF HARMONIC PROBLEMS IN CONTROL SYSTEMS

Zhisheng DUAN; Lin HUANG

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Journal of Systems Science & Complexity ›› 2009, Vol. 22 ›› Issue (4) : 587-596.

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TWO KINDS OF HARMONIC PROBLEMS IN CONTROL SYSTEMS

Zhisheng DUAN, Lin HUANG

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Abstract

This paper discusses the harmonic problems in control systems from two aspects: One is the harmonic control among different subsystems, and the other is the harmonic control among multiple inputs. Some intrinsic problems in such systems are discussed. It is pointed out that some subsystems must be unstable to stabilize the whole interconnected system by an example. Especially for discrete-time multi-input systems, a necessary and sufficient condition is presented for the strict decrease of the quadratic optimal performance index with the control input extensions. This shows an essential difference between single-input and multi-input control systems. Finally, some future research directions are discussed in harmonic control of interconnected systems, allocation of multi-control inputs, fault-tolerant control, and fault-diagnosis.