Robust Helicopter Control using Structured H∞-based Multi-Objective Design

Application to Hingeless Rotorcraft

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Abstract

This thesis 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 𝜇-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/frequency domain criteria, as defined by ADS-33.