|venue:||University of Bath|
Bifurcation analysis of nonlinear ground handling of aircraft - EPSRC Case Award with Airbus UK at the Faculty of Engineering of the University of Bristol
Postgraduate student, James Rankin,started working on this project in October 2006 under the supervision of Professor Bernd Krauskopf and Dr Mark Lowenberg (University of Bristol) in collaboration with Sanjiv Sharma and Etienne Coetzee (Airbus UK).
Airbus is a global enterprise with industrial facilities in France, Germany, Spain and the UK; additional design and engineering satellite offices in the USA, Russia and China; fully-owned subsidiaries in the United States, China, Japan and the Middle East; spare parts centres in Hamburg, Frankfurt, Washington, Beijing, and Singapore; training centres in Toulouse, Miami, Hamburg and Beijing; and more than 130 field service offices around the world. Over the past decade Airbus' Landing Gear Systems Group at its UK Filton site has been increasing its use of computer-based modelling and simulation technologies. In this context the use of dynamical systems theory is playing an increasingly important role in identifying stability boundaries quickly and efficiently.
The EPSRC Case Award "Bifurcation analysis of nonlinear ground handling of aircraft" with Airbus UK is concerned with developing and applying advanced mathematical and computational tools for the analysis of high-speed taxiing, which is crucial for an efficient operation of aircraft at busy airports.
How the project fits in Airbus's research plans. The mid-term goal of Airbus is to develop the requirements for a, potentially, fully automated system that steers an aircraft along the shortest route, orchestrated by Air Traffic Control, as fast as possible between the gate and the runway. To achieve safe and efficient performance of aircraft ground handling, nonlinear effects need to be taken into account, which arise because:
- the tyres deform significantly during normal taxiing operations;
- there is the possibility of slippage while braking or due to changing friction of the taxiway;
- geometric effects may introduce nonlinearities, for example due to non-symmetric thrust at turns;
- active components, such as brakes and actuators, feature their own nonlinearities.
Scope of the project. The project draws on the considerable expertise of the Departments of Engineering Mathematics and Aerospace engineering at the University of Bristol. Its goal is to develop and study a hierarchy of increasingly complex models of aircraft ground dynamics, where the mass/forces balance and other parameters are calibrated from existing aircraft models at Airbus.
The model that is presently being studied is that of a generic Airbus aircraft with nonlinear tyre/ground interaction. Specifically, turning solutions and their stability boundaries are being identified with the method of numerical continuation.
The image above shows an example of dynamics of the aircraft during an attempted specific high-speed turning manoeuvre, where the constant radius solution is already unstable. Stability diagrams in dependence on key parameters, such as the steering angle and thrust level, are being developed in a systematic way.
Follow-on activities. The Case Award has lead to the Airbus UK funded follow-on project `Analysis of nonlinear ground handling models', which employs a three-year Postdoctoral Research Assistant from April 2007 within the research team at the University of Bristol's Engineering Faculty. This new project focuses on the stability of tyre/ground interactions under different types of loading, a problem that was presented by Etienne Coetzee of Airbus UK at the 57th European Study Group with Industry in April 2006. The problem attracted the interest of academics from eight Universities. The one week-long interaction between Airbus and these academics was instrumental to the company taking this research further.
"The Study Group provided us with two main outcomes. The immediate outcome was the discovery of the network of people, who were interested in the topic area and were looking to take the study forward. As a result, we set up a 3-year Research Associateship at the University of Bristol, to extend the study. The by-product is that our relationships, between the University of Bristol and Airbus, are further strengthened" - Sanjiv Sharma, Systems Engineer, Airbus (UK).
As further evidence of the strategic long-term relationship that Airbus has developed with the University of Bristol, Airbus UK are also supporting the related Industrial Mathematics KTN CASE Award "Optimisation of aircraft taxi operations". Since October 2006 Ph.D. student Gillian Keith is working at this project under the co-supervision of Dr Arthur Richards (University of Bristol) and Sanjiv Sharma. The aim is to investigate the use of autonomous operation to achieve faster air-to-gate-to-air transit at airports.