Multi-Objective Design of a Decentralized Structured H∞-Based Controller for Longitudinal Helicopter Flight Dynamics

This paper introduces a multi-objective design approach for an Attitude Command-Attitude Hold (ACAH) and vertical velocity flight control system for the MBB Bo-105 helicopter longitudinal model. The design employs a decentralized structured H∞ dynamic controller using a PI-based and feed-forward control architecture, similar to the PID-based architecture commonly used in rotorcraft flight control design. The proposed design methodology integrates multi-objective approaches within the framework of structured H∞ control design. The uncertain model verifies the controller’s performance under different flight configurations for a helicopter at 40 kts, using mu-analysis which assesses robustness against model uncertainties. The multi-objective approach is employed in the control design process to tune parameters that balance handling qualities with robustness and stability. The performance of the resulting flight control system is investigated and evaluated against the required closed-loop time/frequencydomain criteria, as defined by ADS-33. The resulting design achieves Level 1 handling qualities, for which the advantages and limitations of the proposed methodology are discussed.