Hans Peter Monner

Realization of an optimized wing camber by using formvariable flap structures

Abstract According to market research predictions, a large growth in the number of passengers as well as airfreight volume can be expected for the civil transport aircraft industry. This will lead to an increased competition between aircraft manufacturers. To stay competitive it will be essential to improve the efficiency of new generation of aircraft. Transonic wings of civil aircraft with their fixed geometry offer an especially large potential for improvement. Such fixed geometry wings are optimized for only one design point, characterized by the following parameters: altitude, mach number and aircraft weight. Since these vary permanently during the mission of the aircraft the wing geometry is rarely optimal. As aerodynamic investigations have shown, one possibility to compensate for this major disadvantage lies in the chordwise and spanwise differential variation of the wing camber for mission duration. This paper describes the design of a flexible flap system for an adaptive wing to be used in civil transport aircraft that allows both a chordwise as well as a spanwise differential camber variation during flight. Since both lower and upper skins are flexed by active ribs, the camber variation is achieved with a smooth contour and without any additional gaps. This approach for varying the wings camber is designed to be used for replacement and enhancement of a given flap system. In addition, the kinematics of the rib structure allows for adaptation of the profile contour to different types of aerodynamic and geometric requirements.

DESIGN OF A SMART LEADING EDGE DEVICE FOR LOW SPEED WIND TUNNEL TESTS IN THE EUROPEAN PROJECT SADE

Purpose – The purpose of this paper is to describe the pre‐design and sizing of a smart leading edge section which is developed in the project SADE (Smart High Lift Devices for Next Generation Wings), which is part of the seventh framework program of the EU.Design/methodology/approach – The development of morphing technologies in SADE concentrates on the leading and trailing edge high‐lift devices. At the leading edge a smart gap and step‐less droop nose device is developed. For the landing flap a smart trailing edge of the flap is in the focus of the research activities. The main path in SADE follows the development of the leading edge section and the subsequent wind tunnel testing of a five meter span full‐scale section with a chord length of three meters in the wind tunnel T‐101 at the Russian central aero‐hydrodynamic institute (TsAGI) in Moscow.Findings – The presented paper gives an overview over the desired performance and requirements of a smart leading edge device, its aerodynamic design for the ...

Design of a Smart Droop Nose as Leading Edge High Lift System for Transportation Aircrafts

A seamless and gapless high lift device at the wing’s leading edge has the potential for reduction of airframe noise as well as for drag. A concept of a smart leading edge device was developed, which, due to systems solutions, delivers an alternative to the droop nose device as used for the A380. The main emphasis of this new device is to realize a structure/system solution for a smooth leading surface, which can be deflected into a typical high lift application. With respect to the fact that laminarity is the only technology which has the potential for step changes in drag reduction within a suitable timeframe, smart seamless and gapless high lift devices are a mandatory enabler for future wings of significantly increased aerodynamic efficiency

Development and design of flexible Fowler flaps for an adaptive wing

Civil transport airplanes fly with fixed geometry wings optimized only for one design point described by altitude, Mach number and airplane weight. These parameters vary continuously during flight, to which means the wing geometry seldom is optimal. According to aerodynamic investigations a chordwide variation of the wing camber leads to improvements in operational flexibility, buffet boundaries and performance resulting in reduction of fuel consumption. A spanwise differential camber variation allows to gain control over spanwise lift distributions reducing wing root bending moments. This paper describes the design of flexible Fowler flaps for an adaptive wing to be used in civil transport aircraft that allows both a chordwise as well as spanwise differential camber variation during flight. Since both lower and upper skins are flexed by active ribs, the camber variation is achieved with a smooth contour and without any additional gaps.

Modeling of carbon nanotube actuators: Part I -Modeling and Electrical properties

The outstanding electrical and mechanical properties of single carbon nanotubes (CNT) are the motivation for an intensive research in various fields of application. The actuation effect constitutes the foundation for any application as a multifunctional material and within the field of adaptronics. The effect is in the majority of cases investigated by a CNT configuration of stochastically aligned CNT, so-called bucky-paper, in an electrolytic environment. The article presents an analytical model for a detailed understanding and investigation of the actuation process. The complete description and parameterization of the model is documented in two parts. In the first part the model is developed, the test setup for the model validation and parameter identification is elucidated, and the electrical parameters are determined. In the second part the mechanical system and the actuating effect will be examined. Finally the applicability of the model will be examined.

Development of active twist rotors at the German Aerospace Center (DLR)

Helicopter main rotors are characterized by complex unsteady aerodynamic conditions, which are causing vibrations and noise in and around rotary wing aircrafts. The aerodynamic conditions also cause increased drag, which leads to higher fuel consumption. Even modern helicopters still suffer from these drawbacks. This is why there are many efforts to influence the flow conditions by passive and active means. Active means have the advantage to adapt to varying demands, which can change significantly. A first attempt is to perform a sinoidal variation of the pitch angle of the blades with a frequency that is an integer multiple of the rotor frequency, the so called higher harmonic frequencies. This can be done by additional displacements of the swash plate or by a variation of the pitch link length using actuated pitch links. Since both designs have several drawbacks, one of the most promising approaches is the realization of a secondary control via the deformation of individual blades. Such an actuation can be realized by blade flaps or by the integration of piezoelectric actuators in the blade itself, which causes the blade to twist. At the DLR such twist blades have been investigated intensively. A series of blades has been built using thin skin integrated actuators. This Paper gives an overview of all active twist blades with skin integrated actuators that have been designed and manufactured at the DLR so far. Different design philosophies have lead to different geometrical setups. A comparison of the blades power consumption for given control laws for noise and vibration reduction is also given. Finally, a unique testing technique for nondestructive measurement of mass distribution is discussed in this paper. are characterized by complex unsteady aerodynamic conditions, which are causing vibrations and noise in and around rotary wing aircrafts. The aerodynamic conditions also cause increased drag, which leads to higher fuel consumption. Even modern helicopters still suffer from these drawbacks. This is why there are many efforts to influence the flow conditions by passive and active means. Active means have the advantage to adapt to varying demands, which can change significantly. A first attempt is to perform a sinoidal variation of the pitch angle of the blades with a frequency that is an integer multiple of the rotor frequency, the so called higher harmonic frequencies. This can be done by additional displacements of the swash plate or by a variation of the pitch link length using actuated pitch links. Since both designs have several drawbacks, one of the most promising approaches is the realization of a secondary control via the deformation of individual blades. Such an actuation can be realized by blade flaps or by the integration of piezoelectric actuators in the blade itself, which causes the blade to twist. At the DLR such twist blades have been investigated intensively. A series of blades has been built using thin skin integrated actuators. This Paper gives an overview of all active twist blades with skin integrated actuators that have been designed and manufactured at the DLR so far. Different design philosophies have lead to different geometrical setups. A comparison of the blades power consumption for given control laws for noise and vibration reduction is also given. Finally, a unique testing technique for nondestructive measurement of mass distribution is discussed in this paper.

Modeling of Carbon Nanotube Actuators: Part II -Mechanical Properties, Electro Mechanical Coupling and Validation of the Model

Carbon nanotubes have the potential to become one of the actuating materials of the future. Since the discovery of the actuating effect a lot of experimental data was collected to describe the electro-mechanical coupling. With this paper a model for the system behavior is available to enhance the understanding of the effect. An analytical model is introduced in the first part of the article. The electrical parameters of the model are determined by impedance spectroscopy. Furthermore, the mechanical parameters and the electro-mechanical coupling have to be examined. The main subject of the second part of the article is to validate the model and to compare measured and simulated responses to several excitations.

Compliant structures-based wing and wingtip morphing devices

Purpose The purpose of this paper is to provide an overview of the design and experimental work of compliant wing and wingtip morphing devices conducted within the EU FP7 project NOVEMOR and to demonstrate that the optimization tools developed can be used to synthesize compliant morphing devices. Design/methodology/approach The compliant morphing devices were “designed-through-optimization”, with the optimization algorithms including Simplex optimization for composite compliant skin design, aerodynamic shape optimization able to take into account the structural behaviour of the morphing skin, continuum-based and load path representation topology optimization methods and multi-objective optimization coupled with genetic algorithm for compliant internal substructure design. Low-speed subsonic wind tunnel testing was performed as an effective means of demonstrating proof-of-concept. Findings It was found that the optimization tools could be successfully implemented in the manufacture and testing stage. Preliminary insight into the performance of the compliant structure has been made during the first wind tunnel tests. Practical implications The tools in this work further the development of morphing structures, which when implemented in aircraft have potential implications to environmentally friendlier aircrafts. Originality/value The key innovations in this paper include the development of a composite skin optimization tool for the design of highly 3D morphing wings and its ensuing manufacture process; the development of a continuum-based topology optimization tool for shape control design of compliant mechanisms considering the stiffness and displacement functions; the use of a superelastic material for the compliant mechanism; and wind tunnel validation of morphing wing devices based on compliant structure technology.

Smart-Structures Technology for Parallel Robots

Industrial robots play an important role in automation technology. A further increase of productivity is desired, especially in the field of handling and assembly, the domain of industrial robots. Parallel robots demonstrated their potential in applications with needs for high-dynamic trajectories in the recent years. Within the scope of the Collaborative Research Center (SFB 562)—‘Robotic Systems for Handling and Assembly’ the German Aerospace Center (DLR) and the Technical University of Braunschweig investigate smart-structures technology for parallel robots. In this paper the results of the main topics new active components, Finite-Element based elastic position dependent modeling and vibration control are summarized. The latest parallel robot called is equipped with new active rods. The design as well as the dimensioning of the rod with surface mounted piezo patch actuators is described. For trajectory based robot control, rigid body models are required. In parallel robots with vibration reduction a coupled approach is necessary in which elastic and rigid body equations are combined. The derivation of the equations for parallel robot is presented. Finally, the implemented vibration control is explained. In a position-dependent approach several robust controllers are switched to gain optimal control performance. A stability proof for the switching process is derived.

Evolution of Active Twist Rotor Designs at DLR

Unsteady flow conditions in the rotor disk are causing intense vibrations and noise in rotary wing aircrafts. Even modern helicopters still suffer from these drawbacks. This decreases the on board comfort, causes material fatigue and reduces the public acceptance of helicopters. For this reason there are many affords towards an active manipulation of the flow conditions to decrease noise and vibrations. This could also lead to a reduction of fuel consumption. One of the most promising approaches to do so is a secondary control by deformation of the individual blades. Such an actuation can be realized by the integration of piezoelectric actuators in the blade itself, which causes the blade to twist. The German Aerospace Center (DLR) started to work with active twist rotor blades in the early 90. Ever since, the technology of actuation has evolved drastically, opening new ways to twist blades by means of actuators. This paper presents the evolution of blade design in the last years.