Helicopter Flight

BK117 prototype by Eurocopter equipped with active Trailing-Edge Flaps (TEF)Picture: © Airbus Helicopters

 


 

Active Rotor Control

Experimental Rotor Blade with Active Trailing Edge flaps © Airbus Helicopters Individual blade control (IBC) offers the possibility to adjust the pitch angle of each rotor blade independently. To this end, Airbus Helicopters developed an advanced system for IBC based on piezo-actuated trailing edge flaps (TEFs) on each blade. This system offers the potential for the reduction of helicopter vibration, the reduction of blade vortex interaction noise and also the possibility to increase lead-lag damping through active control. With our research, we accomplished two world first demonstrations.

In-Flight Tracking Control

Schematic of Tracking Errors A part of helicopter vibration is originated by blade dissimilarities. These dissimilarities cause the rotor blades to travel on different paths leading to static and dynamic imbalances, which in term lead to vibratory loads in the airframe. To minimize these vibrations a control concept was developed, which a continuous adaptation of the rotor tracks over the whole flight regime through control. It was demonstrated the first time (worldwide) with flight tests on a full-scale EC145.
Experimental Demonstrator (EC145) © Airbus Helicopters Time History of Lead-Lag Moment and Body-Fixed Roll and Pitch Rate from Flight Test

Lead-Lag-Stability Enhancement

Time History of Lead-Lag Moment and Body-Fixed Roll and Pitch Rate from Flight Test During the nominal rotation of a rotor, the rotor blades move out of the rotor plane (flapping) and in the rotor plane (lead-lag-motion). The lead-lag motion suffers from low damping which can result in resonance phenomena such as ground- and Air-resonance. In order to prevent such resonances, a control concept was developed that makes use of TEFs such that the damping of the lead-lag-motion is increased. This control concept was implemented on a full-scale EC145 and its functionality was demonstrated for the first time (worldwide) through flight tests.

Scaling of Active Rotor Control Concepts

Schematic of Scaling with Respect to Blade Number Individual blade control has shown its potential for various control tasks like helicopter vibration reduction and lead-lag damping enhancement, on an EC145 (four rotor blades, 3,5t), the rotor of which was equipped with active TEFs. Ongoing work focuses on the scaling of this technology to other helicopter configurations with respect to the IBC actuation system, blade number or the size of the rotorcraft.

 Pictures: © Airbus Helicopters, © iFR

 


 

Slung Load Control

A Fire Helicopter with Bucket on a Slung ©https://commons.wikimedia.org Helicopters are used in missions that require hover or slow flight capabilities. In many of these missions, the payload is carried as external slung load, typically below the helicopter. Examples include the construction of buildings in difficult terrain, fighting forest fires, mountain rescue, or cutting free of overhead power lines. All these missions require a tremendous amount of concentration of the pilot. As a subcontractor to Airbus Helicopters we contribute to measures to fly a helicopter with external load safer and more efficient. This includes simulation models and controller implementations that will eventually lead to flight testing.
Basic mechanisms are investigated and explored with the help of UAVs and transferred to manned helicopters. For that purpose, an ongoing student exchange program with the Australian Research Centre for Aerospace Automation (ARCAA) is maintained, offering aerospace students the possibility to both contribute to latest research activities and work within an international team of scientists. The video below exemplarily shows an outcome of the partnership.
 

Picture: © https://commons.wikimedia.org

  • Notter, S., Heckmann, A., McFadyen, A., Gonzalez, F.: Modelling, Simulation and Flight Test of a Model Predictive Controlled Multirotor with Heavy Slung Load , 20th IFAC Symposium on Automatic Control in Aerospace, Aug. 21-25, 2016, Sherbrooke, Canada.

 


 

 

@2015 iFR - Flight Mechanics and Controls Lab

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70569 Stuttgart
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Fax:        +49 711 685-66670

Mail:       ifr@ifr.uni-stuttgart.de