## TaxiBot: Ricardo Engineered Robotic Vehicle Concept To Reduce Aircraft Fuel Consumption and Noise on the Ground

##### 18 November 2009
 CAD model of TaxiBot showing aircraft nose wheel and landing gear fully engaged. Click to enlarge.

Taxiing to and from the airport terminal gate and runway is a major source of CO2 emissions. Aircraft are currently required to use their main propulsion jet engines in a highly inefficient manner for slow speed ground movements; the consequence is greater local air and noise pollution, as well as wasted fuel and hence increased carbon emissions.

Ricardo has successfully engineered and delivered a demonstrator robotic, pilot-controlled towing vehicle known as ‘TaxiBot’ for Israel Aerospace Industries (IAI). The TaxiBot concept is capable of operating with both wide and narrow bodied commercial airliners; it requires no modification to the aircraft, taxiways or runways, and only minor changes to airport infrastructure.

Ricardo has been working for the past 15 months with IAI to develop the Taxibot concept. After an initial feasibility study, Ricardo developed a detailed program for IAI to take the concept to the level of a working demonstrator vehicle with full capability. Ricardo’s involvement in this work included requirements capture, conceptual design and detailed specification design, manufacture and demonstration of the first TaxiBot demonstrator vehicle.

Following the successful build and initial testing of the first vehicle, IAI has now signed a Memorandum of Understanding with Airbus Industries and a Memorandum of Agreement with international ground support equipment provider TLD, covering the next stages of development of the TaxiBot concept.

After further testing and development, Taxibot has the potential to play a significant role in the reduction of fuel costs and emissions. According to IAI and Airbus, Taxiing at airports using aircrafts’ main engines results in a huge consumption of fuel (forecasted to cost around $7 billion by 2012), a large emission of CO2 (approximately 18 million tonnes per year), and a significant source of foreign object debris damage (costing around$350 million per year).

The first TaxiBot vehicle—a full size, fully operational demonstrator—is based on a Krauss Maffei PTS-1 aircraft towbarless tractor originally owned by Lufthansa LEOS. This donor vehicle has been heavily redesigned, modified and rebuilt by Ricardo to install IAI’s patented and innovative ideas of a turret and energy absorption systems and controls. The key modifications to the base vehicle by Ricardo were the installation of the turret to which the aircraft nose wheel is clamped and that can rotate as the pilot steers the nose wheel; a platform that can tilt and move axially; and chassis extensions to the existing vehicle including an additional axle set, enabling the TaxiBot components to be incorporated. The resulting now six-wheeled vehicle is capable of towing Boeing 747 and Airbus A340 airliners.

The demonstrator vehicle weighs 52 tonnes and is powered by twin, 500 hp (373 kW) V8 diesel engines which operate a complex hydrostatic drive system as well as hydraulic systems handling the 4-wheel steering and aircraft pick-up and clamp actuators. Dual Ricardo ‘R-Cube’ electronic controllers manage the forces applied to the nose landing gear as well as vehicle speed and all the communications with the customer’s electronic systems for navigation, speed setting and control tower integration as well as the operational logic of the vehicle systems and the pilot interface.

TaxiBot has been an interesting program that has brought together leading edge automotive simulation, electronics, control technologies and special vehicle engineering skills to address one of the key environmental challenges facing the aerospace sector. It has set some industry firsts too, including the full dynamic modelling of an aircraft being towed under pilot control (using the ADAMS multibody dynamics and motion analysis software) and the physical demonstration of pilot controlled taxiing using the TaxiBot demonstrator vehicle and test trailer.

—Eric White, Ricardo chief engineer for TaxiBot

 The nose wheel of the aircraft enters the vehicle turret and is clamped into position. The turret can rotate freely and hence take steering and braking requests directly from the nose wheel. The flight crew can thus manoeuvre the aircraft without using the main engines. Click to enlarge.

Operation. On engaging with the TaxiBot, the nose wheel of the aircraft enters the vehicle turret and is quickly clamped securely into position. The turret is able to rotate freely and can hence take steering and braking requests directly from the nose wheel in such a way that the pilot should not notice the presence of the tug whilst being towed normally by TaxiBot.

A crucial aspect of the TaxiBot design is that the aircraft brakes slow the aircraft down, not the tug. This, coupled with the management of the nose landing gear forces makes operational towing possible. With the TaxiBot engaged the flight crew can manoeuvre the aircraft around the taxi-ways of the airport, relying solely on auxiliary power units for on-board power and air conditioning needs.

To orchestrate the technology, IAI has developed and provided a “high-level” vehicle controller that will integrate with airport control towers and provide speed target, towing force and other mission data while constantly monitoring geographical position. While the current prototype assumes that an operator is present in the vehicle, the control architecture of the vehicle is already in place to support autonomous tug operation so that in the near future no tug driver would be needed for taxiing.

 TaxiBot and Test Trailer. Click to enlarge.

Initial testing. To test the TaxiBot prototype demonstrator vehicle, Ricardo has designed and built, in parallel with the vehicle program, a 100-tonne test trailer equipped with a hydrostatic dynamometer capable of simulating large passenger aircraft tyre drag. The test trailer is designed with a genuine Boeing 747 cockpit and nose landing gear in order to fully replicate the processes both of towing and flight deck control of the tug. This highly flexible test trailer has enabled extensive testing of the prototype TaxiBot vehicle to be carried out by Ricardo at the Dunsfold aerodrome close to London, UK.

Next steps. Following signature of the Memorandum of Understanding between IAI and Airbus Industries on future development of TaxiBot at the 2009 Paris Air Show, and subsequent Memorandum of Agreement with TLD, development tests are continuing to be carried out by Ricardo using the demonstrator TaxiBot vehicle and test trailer at Dunsfold. Once this testing is completed it is planned that the demonstrator vehicle will be shipped to Toulouse airport where the TaxiBot will be used in further tests in February 2010 with an Airbus owned A340-600 airplane weighing approximately 350 tonnes. The Ricardo team on the TaxiBot program will continue to support the development work throughout this next phase based at Toulouse.

This seems to be a fine a logical idea.

This is a horrible idea. Commercial airports, especially the bigger ones, have a constant rush-hour like flow of baggage vehicles, security, firefighting, maintenance and other vehicles moving around all the time. The last thing they need to add to the mix is a bunch of these taxibots to add to the aggravating airport experience. European countries (esp. Spain, UK) might get conned into mandating these, but I hope its an idea that never takes flight here in the US. Focus on renewable jet fuel...don't make airports more dreadful than they already are.

You could have these taxibots taking an aircraft to the runway, going by themselves to the other end of the runway, then take another aircraft back to the terminal. The only part of the journey where there is extra traffic, ie taxibot with no plane, is the part along the runway which is not the busiest part of an airport.

This seems all quite rational but I am astonished that this vehicle weighs 52 tons and requires two (2) 500 hp engines.

One would think that 45 mph max speed and 0-45 mph in 30 sec and 2% grade would require about 8 tons and 250 hp - or less.

But do they need me to tell them this? Sigh, - no. Of course not.

Airlines might jump at this though as a way to pay their pilots less.

Reduced fuel consumption and emissions. What's ejj missing here??

??
It looks like a win-win.

I think it's a misplaced priority, and I'm not seeing the benefits vs. costs. Fuel prices are killing the airlines; logic would follow that getting the fuel issue figured out should be the biggest priority. I also support simplified airfields - the fewer moving parts the better. How much fuel is really burned while taxiing? Planes have their engines idling a lot of the time. Airports are complicated enough...taxibot makes them worse.

Toppa,

At only fifty two tonnes and twice 500 ponies,

Lets hope the wind gusts stay away and no pilot hits any reverse button (accidentally) 0r forgets to enable the hand brake.
If any of the above let loose or a belated 'abort landing' command were given, this little 50 tonne buggy could be in for a hell of a ride.

Engines idle with the inner (high speed, high pressure) rotor at about 30% of maximum rpm. At taxi thrust, it is worse. And unlike an ICE, the compresion ratio plummets greatly as speed drops. The fuel consumption at taxi thrust is almost comparable to cruise.

The world is complicated. Adding Taxibots to airports is like adding EVs to highways.

ToppaTom: But it's not win-win...passengers lose more, because passengers are already losing at airports with delays & lost productivity. Think of all the energy that could be saved at airports if there weren't any delays and entire terminals could be shut down for longer periods.

Luckily, these taxibots will have a brutally difficult time becoming reality at American airports, if they ever do, because airports are generally run by their own governing entities which will have to approve the taxibots and unions which will be scrutinizing them. Who is going to pay for the taxibots? Airlines? No...the airport authorities will have to buy them & staff them, adding significant costs and complexity to an already complicated mess that is our aviation system.

Replacing 50% of the daily flights with ultra high speed electric trains could nolify the need of those questionnable gadgets and be much better for environment.

ejj, What do you mean;
"But it's not win-win...passengers lose more, because passengers are already losing at airports with delays & lost productivity. Think of all the energy that could be saved at airports if there weren't any delays and entire terminals could be shut down for longer periods. " ?

ToppaTom: My point is that you don't become more efficient by adding complexity. More efficient = more green. I've had enough bad experiences at airports that I'm extremely skeptical of taxibot.

Of course more complexity can mean more efficiency.

Even the Luddites did knew this.

Autos with VVT (or even hybrid with regen and batteries) are ICE vehicles made more efficient and more complex.

More efficient does not = more green, and more green does not = more efficient.

And walking or biking across the country is hardly more efficient than flying.

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