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ACFA 2020
Active Control of Flexible 2020 Aircraft

Tags: Air

State of the Art - Background

Blended wing-body (BWB) type aircraft configurations, i.e. generally tailless aircraft configurations with aerodynamic wing/fuselage blending, are highly promising concerning improved low fuel consumption. This is mainly achieved by reduced structural weight and through a minimum wetted area which is significantly lower for BWB-type aircraft compared to other configurations. Major design issues of such BWB-type aircraft have already been solved or are currently under investigation in the European funded projects VELA and NACRE. The fuel efficiency of the so-called 750-passenger NACRE flying-wing configuration is comparable to the 1990s BWB concepts in the US. However, the biggest market share in long haul flights today is taken by mid-size aircraft (400-500 passengers). Therefore, there is an urgent need to exploit the advances from the VELA and NACRE projects for the pre-design of a marketable European mid-size flying-wing aircraft with a high fuel efficiency. The challenge created by the complex active control system for BWB-type aircrafts has been identified, but not yet addressed in the European projects VELA and NACRE. The aspects of ride comfort and loads alleviation under consideration of the flexible aircraft structure are of particular interest.


The ACFA 2020 project addresses two main objectives, namely:

1. To provide solutions for the active control system for BWB-type aircrafts to supply the required handling qualities and, in particular, to alleviate gust and manoeuvre loads, as well as to improve ride comfort. BWB-type aircraft set completely new challenges in regards to complexity of control algorithms, control design and optimisation, as well as control system architecture. Instead of various single-channel or single-input-single-output (SISO) controllers, a highly coupled multi-channel or multiple-input-multiple-output (MIMO) controller is required. Moreover, the high interaction between control and system aspects will be taken into account.

2. To provide a pre-design for a marketable European ultra-efficient flying-wing aircraft - the ACFA 2020 aircraft configuration. The ACFA 2020 aircraft configuration structure will be finally sized according to the achieved loads reduction by active control of the flexible aircraft in order to minimise the structural weight. The ACFA 2020 aircraft configuration's airframe will aim for at least half of the 50% reduced fuel consumption compared to current standard aircraft configurations of similar size.

Description of Work

In order to achieve the objectives of ACFA 2020, the work is organised into four technical subsequent work packages (WP). The core of the ACFA 2020 project is WP3 'Development & evaluation of active control concepts', where MIMO active control systems for BWB-type aircraft are designed by a community of partners involved in the NACRE and VELA projects, as well as additional key players in control design from Europe and Israel. The main objective of the designed control systems is to reduce structural vibrations and unwanted rigid body motions on the one hand, and gust and manoeuvre loads on the other. The reduced static and dynamic loads are the basis for a structural resizing performed in WP4 'Assessments and integration for the ultra-efficient 450-passenger ACFA 2020 aircraft configuration' which is designed in WP1 'Aircraft configurations definition and down-selection'. WP2 'Dynamic modelling' generates parameterised reduced-order state-space models (ROM) of the NACRE flying-wing aircraft, as well as the ACFA 2020 BWB. The investigations on the multi-objective MIMO control algorithms will start with the ROM of the NACRE flying-wing aircraft due to their early availability.

Expected Results

The key deliverables of the project are:

Deliverable I: Solutions for active MIMO control for BWB-type aircraft.

Active control systems for the alleviation of structural vibrations as well as of gust and manoeuvre loads have been investigated for conventional aircraft configurations in the European AWIATOR project, as well as in the German national project MODYAS. Such active control systems are an important means for the reduction of critical loads, as well as for the improvement of ride comfort and handling qualities. It is self-evident to also incorporate active structural control into future aircraft configurations. Thus the main deliverable of ACFA 2020 will be robust as well as adaptive MIMO architectures for active control of BWB-type aircraft.

Deliverable II: ACFA 2020 aircraft configuration consisting in the pre-design of an ultra efficient 450-passenger BWB type aircraft.

The active MIMO control strategies developed in ACFA 2020 will be applied to this new 450-passenger aircraft for load reduction as well as for improved ride comfort and handling qualities. Based on the achieved load reduction the ACFA 2020 aircraft configuration structure will be resized to demonstrate the potential weight benefit achieved with an integrated active control of the flexible aircraft.

ACFA 2020
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ACFA 2020 blended wing-body aircraft design