The HELIACT project
Summary - The Helicopter Active Control Technology project was started in 2003. The aim of the project is to develop advanced control laws for helicopters and tilt-rotors. The goal of these novel control laws is to improve handling qualities, to provide structural load alleviation and to provide flight envelope protection. The primary aircraft of interest is the Bell 412 Advanced Systems Research Aircraft (ASRA) of the NRC Canada. This aircraft is equipped with a full authority simplex fly-by-wire system. New control laws can rapidly be implemented and tested on this aircraft. Besides this research aircraft, use is also made of two high fidelity nonlinear simulation models of the XV-15 tilt-rotor and the UH-60 Black Hawk helicopter. Up to date, the main achievements of the project are: (1) the development and validation of a high fidelity nonlinear simulation model of the Bell 412 ASRA and (2) the design and flight test of several novel control laws on the Bell 412 ASRA.
Background and project aim
Rotorcraft exhibit handling qualities that make them difficult and tiring to fly and while their remarkable capabilities enable them to undertake a wide variety of difficult tasks, often these require very high pilot workload. To this end, there are sound reasons for replacing mechanical and hydraulic control systems with electrical and optical ones, as is the trend, with task-tailored control laws. How best to use the freedom that this tailoring gives is now one of the main questions.
The introduction of active control technology (ACT) makes the implementation of new and potentially better control laws possible, and with these comes the possibility of utilizing the full potential of a given aircraft: higher performance, the ability to operate more safely, more economically, in worse conditions, and closer to the extremes of the flight envelope. Better control systems, designed more quickly and with less trial-and-error and flight test development, will be achievable if the complexity of the helicopter's dynamics are accurately modeled and taken into account ab initio.
We aim to address this by developing and integrating techniques for modeling, identification and control. The emphasis on multi-disciplinary design and optimization provides a rich new focus to this theme. The project involves collaboration with NRC Canada. The project will use a sophisticated six-axis Flight Simulator at the University of Liverpool, and the Bell 412 Advanced systems Research Aircraft (ASRA) of the NRC Canada. This aircraft is equipped with a full authority simplex fly-by-wire flight control system and with a wide range of sensors.
The project has two strands, one related to model development, the other to control for handling qualities, flight envelope protection and load alleviation, possibly using RSF. Use of a fully instrumented research helicopter with rotor blade measurements will enable us to investigate some of the deficiencies in existing mathematical models and to produce better models. It will enable us to investigate the advantages that result from feeding back rotor states, and to investigate the extent to which, given better models, these advantages could be realized by estimating, as opposed to measuring, rotor states.
The project uses both ground-based and airborne simulation to test new types of control law. The Bibby Flight Simulator at Liverpool features six-axis motion, 6-channel visuals and a programmable force feel system. This will enable sophisticated testing and analyses to be performed prior to flight test. We will conduct experiments to shed light on basic issues relating to modeling, robust stability and performance. Our prime objective is to investigate the benefits of novel active control concepts applied to the mutual improvement of HQs, FEP and SLA. We will use flight test data from NRC, and develop linear and non-linear models. These will help us to further the understanding of some of the effects of feedback control on the rotor, and thereby to develop improved design procedures.
Click on the links below to find out more about a particular aspect of the HELI-ACT project:
Dr. Daniel J. Walker
Dr Binoy Manimala
Dr Ridwan Kureemun