Saturday, 8 December 2012

Journal Paper: Cooperative distributed MPC

I'm pleased to learn that our latest paper is now available on the Automatica website:

Paul Trodden, Arthur Richards, Cooperative distributed MPC of linear systems with coupled constraints
Automatica, Available online 4 December 2012,

Thanks to Paul Trodden for all his hard work on this paper, which reports on his PhD findings on how inter-agent cooperation can improve performance, e.g. by breaking deadlocks between greedy agents.  Congratulations as well to Paul on his recent move to the University of Sheffield's Automatic Control and Systems Engineering department.

Tuesday, 21 August 2012


Pillsbury A Mill and Stone Arch Bridge, 4th of July

I'm just back from the AIAA Guidance Navigation and Control (GNC) Conference in Minneapolis.  There were many interesting things to see and I can't do justice to it all here, but if only for my own memory, here are a few of the most relevant papers.  (Note on referencing: there doesn't seem to be an easy way to link into the AIAA database.  Instead, I'll just provide paper numbers, AIAA-2012-XXXX.  You can search by number in the AIAA Electronic Library.)

Starting with the Air Traffic Management domain, it was interesting to see nonlinear trajectory optimization applied (AIAA-2012-4755) and EADS' work on modeling noise in trajectory optimizers (4482).  Meanwhile UCSC presented some work on formation flight for civil airliners (4524) and our own Tom Kent did a good job of presenting his recent PhD work in this area (4769).  Finally, MITRE's work on flow contingency management (4976) nicely complements our own work on the ONBOARD SESAR project.

Heading into space, Iowa State made a very elegant job of rendezvous optimization by using conic programming (4924), solving many of the challenges we encountered in the ORCSAT project while still having a convex optimization at the core. In the very next paper, a consortium including ESA and the University of Exeter proposed methods for verification and validation of spacecraft rendezvous controllers based on both numerical and analytical methods for finding worst case behaviour.  Louis Breger presented an elegant approach to fault detection (4611) which I'm sure should be in an optimizer somehow...

There was an enormous range of work in the UAV area.  Starting at the practical end, it was interesting to see indoor flight testing using the same fixed-wing Night Vapor aircraft as in our experiments (4464), including gust response work.  Adaptive control seems to work nicely for MIT's quadrotors (4551) and others from Seoul with attached manipulator arms (4835).  There were whole sessions on vision-based control (5048 to 5051) including Steve Waslander's dampening experiences of chasing icebergs (5049): it was also interesting to see latency handled by simple linear approximations in these works.  Moving to higher level control of teams and tasking, there were developments in optimization from Toronto (4680) and planning based on data-driven learning from MIT (4682).

And let's not forget the discovery of the bizarre love of lawn green bowls in Minneapolis - quite surreal.

Friday, 20 July 2012

Optimal Transatlantic Routes for Formation Flight

View Larger Map

The map above illustrates the results of Tom Kent's work on formation flight for airliners. These are the optimized routes for 210 eastbound transatlantic flights, allowed to fly in pairs in formation in order to save fuel.  The optimization does not consider the timing of the flights - it is assumed that they coordinate to achieve their rendezvous.  However, it does determine which pairs should be formed and where each pair should join and then break apart.  Interestingly, many formations share the same departure point: zoom in on Atlanta or Heathrow, for example, or observe the LAX-Dublin teaming with the SFO-Dublin flight.  There are also some curiosities like the Newark-Lisbon flight joining up with the flight from Boston to Lajes in the Azores.

Tom's methods and initial results will be presented at the AIAA Guidance Navigation and Control conference this August.

Thursday, 10 May 2012

Bristol Robotics Lab now officially open

The Bristol Robotics Lab (BRL) was officially opened this morning by the Universities and Science Minister, David Willetts.  BRL is a joint venture between UWE and the University of Bristol, located at UWE's Frenchay Campus.  Aerospace colleague Tom Richardson and I are particularly excited about our newly-equipped flying arena, one of the biggest in Europe at about 15m x 12m x 4m high.  Thanks to funding from DSTL and support from Vicon and dSpace, it is now instrumented for real-time flight control and enclosed with protective nets and curtains.

Coverage of the BRL opening can be found at:

The introductory video also includes some of our flight demonstrations:

More about our Unmanned Air Systems project can be found at

Special thanks to postdoc Colin Greatwood for his hard work in getting the flight demonstrations ready for the opening.

Thursday, 12 April 2012

Two fully funded PhD opportunities

UPDATE: these posts have now been filled.

Two fully-funded PhD studentship opportunities are available for EU nationals starting between now and October 2012.  Updated with links - see below.

Routing and Tasking Optimization for UAVs
This project will develop novel optimization techniques for the joint task allocation and routing of a small team of Unmanned Air Vehicles (UAVs).  Given a number of surveillance tasks, times to travel between task locations, available UAVs and remaining fuel levels, we have an initial method of finding the best routes and allocations.  This project will look for ways of making this faster and more robust, by combining different types of optimization (e.g. branch-and-bound, genetic algorithms, simulated annealing).  The project will also look at applying machine learning techniques to try and predict the user's requests before they're even made: make the answer available before the question's even asked.  Applicants should have a good first degree (2:1 or higher) in engineering, mathematics, computer science or a related subject.  Experience of optimization, operations research, machine learning or other relevant techniques would be beneficial. More information can be found at:

Multifunctional Air Deployed Exploration Nodes (MAiDENs)
(Applicants are free to suggest a better acronym!)  Imagine a micro UAV exploring a building.  Its battery is made up of many small cells, and whenever one is getting low on charge, it is dropped.  The UAV now has less weight so its flight time is extended.  Meanwhile, some extra electronics on each dropped cell makes use of the remaining charge: (a) it relays communications back to the outside world (b) it uses a small acoustic sensor to alert the UAV to changes in the world (c) when the UAV is ready to leave, it turns on a small beacon to act as a breadcrumb for the trail back out.  Now, all we have to do is see how well this can be achieved in, say, a gram, and figure out how best to deploy the idea.  For this project, applicants should have a good degree in electronics, robotics, engineering or similar, and experience of low power electronics will be a great help.  THis project will be jointly supervised by myself and colleague Steve Burrow.  More information can be found at:

Both studentships will be held in the Department of Aerospace Engineering, part of Bristol’s Faculty of Engineering. The projects will be affiliated with the Bristol Robotics Lab, utilizing the large indoor flying arena for experiments. Stipends will be at the standard level of £13,590 p.a. plus a top-up of £3,000 p.a. 

To apply, visit . On your application form, identify “PhD in Aerospace Engineering” as your chosen degree programme, Dr Arthur Richards as your proposed supervisor, and either (or both) of the two projects above as your proposed topic. Please use the “Proposed Research” section of the application to discuss your interest in the particular project(s). 

New UAV Exploration Project

We are beginning a new project on indoor exploration using small Unmanned Air Systems (UAS).  Colin Greatwood (shown right) is staying on after his PhD to develop new algorithms for exploring unknown environments without the use of GPS.  These techniques will allow UAS to investigate hazardous environments such as collapsed buildings or damaged nuclear or chemical plants.  This is a missing piece in a very big puzzle: we have worked on getting from A to B in cluttered environments and figuring out where the vehicle is without GPS: this project will help when we don't even know where B is and we need to explore.

A significant part of this project, funded by DSTL via the Centre for Defence Enterprise, is the equipment and commissioning of our large flying area at the Bristol Robotics Lab (BRL).  Colin is shown in the arena flying a AR Drone Parrot quadrotor in the photo.  With support from Vicon and dSpace, we will be equipping the arena with video tracking cameras and real-time control computing hardware.  The result should be one of the largest instrumented flying arenas in Europe.

Tuesday, 3 January 2012

New Air Traffic Management Projects

Left-to-right: Gillian Clare, Ollie Turnbull and Tom Kent
I'm delighted to welcome three new members to our research group, all working in the area of Air Traffic Management (ATM) and air traffic operations.  I must admit that "new" is a relative description here, as two of the three are rejoining us after spells away.

Gillian Clare rejoins us to work as a postdoctoral researcher on the "ONBOARD" project.  ONBOARD is a research project within the WP-E Long Term and Innovative Research Work Package of SESAR, the Single European Sky ATM Research joint undertaking.  Led by Spanish technology group GMV and in collaboration with Swiss ATM developers Skysoft, ONBOARD stands for "Probabilistic Network Based Operations ATM R&D".  The goal of the project is to improve large scale operations planning by incorporating probabilistic models of the uncertainty in the system.  Gillian's role will be to develop the "Network Manager" that solves the ATM flow problem robustly, to suit the uncertainty information available.  The work will also involve research into the development of the probability models themselves, to cover capacity factors including weather and scheduled demand.  Read more about the ONBOARD project at its page on the ComplexWorld ATM research network.  Gillian herself is familiar to this blog, having done her PhD with us, studying optimization of airport taxi operations, and rejoins us after a spell in industry.

Like Gillian, Ollie Turnbull also did a PhD here, using decision trees to clone the behaviour of trajectory optimizers, before moving to industry.  Ollie rejoins us now as the postdoctoral researcher on our second SESAR WP-E project, SUPEROPT.  This project is led by and completely performed by ourselves at Bristol.  SUPEROPT stands for "Supervision of Route Optimizers" and seeks to enable more intuitive human interactions with optimizers.  As many frustrated Sat-Nav users will know, route optimizers are often worryingly good at finding the loopholes in the problems we set them, especially when we try and modify the routes using our own experience.  SUPEROPT aims to develop forms of constraints that enable the supervisor to easily influence the outcome, but without overconstraining the result.  Likewise, enhanced information on the result will be developed to convey the rationale to the supervisor: why is the result the way it is?  With this two-way interaction, we hope to leverage the power of computer optimization without losing the hard-earned experience of human operators.  Read more about SUPEROPT on the HALA! ATM research network page.

Finally, Tom Kent joins us to study for a PhD in future air traffic operations.  Supported by Airbus UK at Filton and EPSRC, Tom is exploring the mathematics underlying novel concepts for aircraft operations with reduced environmental impact and cost, starting with formation flight.  This idea is described in this Future by Airbus video and was demonstrated on a small scale by NASA.  It worked for two F/A-18s following the same route, but what about airliners on different routes?  Tom's work looks at when and where airliners should meet, if at all, to save fuel by flying in formation.  Tom joined us after completing a Maths degree at Edinburgh.  His background serves him well, as these problems are turning out to involve some very elegant geometry: watch this space to see how it all relates to Fermat...