Rotorcraft simulation modelling and validation for control law design

Abstract

This paper describes the development and validation of a high fidelity simulation model of the Bell 412 helicopter for handling qualities and flight control investigations. The base-line model features a rigid, articulated blade-element formulation of the main rotor, with flap and lag degrees of freedom. The Bell 412 HP engine/governor dynamics are represented by a second-order system. Other key features of the base-line model include a finite-state dynamic inflow model and lag damper dynamics. The base-line model gives excellent agreement with flight-test data over the speed range 15-120kt for on-axis responses. Prediction of off-axis responses is less accurate. Several model enhancement options were introduced to obtain an improved off-axis response. It is shown that the pitch/roll off-axis responses in transient manoeuvres can be improved significantly by including wake geometry distortion effects in the Peters-He finite-state dynamic inflow model.

Investigation of rotorcraft-pilot couplings under flight-path constraint below the minimum-power speed

“…In Ref. 19, Hodgkinson et al conducted a study to determine whether longitudinal, low-order, equivalent (linear) system parameters could be used to predict PIOs. In another study, Hess and Kalteis (20) employed the optimal control model to predict the susceptibility of an aircraft to longitudinal PIOs in pitch attitude tracking tasks, by providing a formal procedure for generating this form of pilot model.…”

Helicopter load alleviation using active control

“…In 2005, the first successful flight test of an Hinfinity control law on a Bell 412 helicopter was demonstrated in the HELI-ACT project in 2005 (17) . This control law was based on a rotorcraft model (3) with uncertainties present. This demonstrates that Hinfinity control is a useful technique applicable to a real helicopter.…”

“…The ability to fly throughout the operational flight envelope without concern for structural, aerodynamic or control limits is referred to as 'carefree handling' (CFH) (2) . The research presented in this paper is part of the helicopter active control technology (HELI-ACT) project (3,4) , which involves collaboration between the University of Liverpool and the National Research Council (NRC) of Canada. The project, which lasted from 2003 until 2007, has had access to a six-axis motion base flight simulator HELI-FLIGHT (5) at the University of Liverpool and a flyby-wire research Bell 412 helicopter at the NRC (6,7) .…”

Condition-based flight control for helicopters: An extension to condition-based maintenance

“…The development of this model is thoroughly described by Manimala et al [30]. The main features of the simulation model are the following.…”