A novel performance synthesis method for unknown mismatched disturbances with finite-frequency specifications

Area of Science:

• Control Systems Engineering
• Robust Control Theory
• System Identification

Background:

• Equivalent-input-disturbance (EID) control systems often assume known disturbance characteristics.
• Existing methods may require prior knowledge of disturbances or lack guaranteed performance.
• Achieving robust disturbance rejection in both single-input, single-output (SISO) and multi-input, multi-output (MIMO) systems remains a challenge.

Purpose of the Study:

• To develop a novel synthesis method for disturbance-rejection performance in EID-based control systems.
• To guarantee prescribed finite-frequency performance irrespective of unknown or mismatched disturbances.
• To remove the prior assumption on the existence of an EID on the control input channel.

Main Methods:

• Introduction of an auxiliary indicator (intermediate variable) by treating the Luenberger observer as an ideal dynamic.
• Analysis of disturbance-rejection control mechanisms using a commutative condition for SISO and MIMO systems.
• Development of a practical commutative condition and a performance-oriented design algorithm.

Main Results:

• The commutative condition is inherently satisfied for SISO systems.
• A practical commutative condition was developed to address challenges in MIMO systems.
• The proposed algorithm ensures finite-frequency and entire-frequency disturbance-rejection performance requirements.

Conclusions:

• The novel synthesis method offers robust disturbance rejection for EID-based control systems.
• The developed approach guarantees performance without prior disturbance knowledge.
• Case studies demonstrate the superiority of the method for vehicle suspension and MIMO systems.