From Handling Qualities Requirements to the Design of Robust Control Laws for Helicopters

The complexity of helicopter flight dynamics combined to an increasing demand to improve its mission performance are two sources of difficulties for the efficient design of helicopter flight control systems. Handling qualities requirements, as specified in ADS-33 standards (Ref. 1) provide a useful guideline for control laws design. The right selection of the criteria in relation with the helicopter planned missions (MTEs) and the usable cues to realize them (UCE) can ensure an optimized design of the control system. However, designing robust control laws with such constrained requirements remains a challenging task. Recent activities at ONERA have led to the development of an approach to integrate handling qualities requirements in robust control design techniques. As a first step Handling Qualities charts are generated using an equivalent model of a conventional PID controller for an Attitude Command Attitude Hold (ACAH) control law. After what the charts are used to feed robust control design tools. The paper presents the charts, their validation process and their use in ONERA robust control design environment.