Fish Bone Active Camber Research Articles

Modelling and analysis of two-dimensional static and dynamic aeroelasticity of Fish Bone Active Camber morphing aerofoils

As a continuous and smooth morphing concept for aerofoils, the Fish Bone Active Camber (FishBAC) concept has demonstrated significant aerodynamic efficiency improvements over traditional hinged flaps. In this paper, to investigate the static and dynamic aeroelasticity of FishBAC aerofoils, an unsteady two dimensional coupled fluid-structure interaction model is developed, which includes the structural response of the FishBAC spine, skin, stringers, tendons and actuator, coupled to an unsteady aerodynamics model. The structural dynamic model is Timoshenko beam-theory-based, while the aerodynamic model is based on Peters’ unsteady model. The static and dynamic aeroelasticity is studied after the model is validated. Results show that the increase in pulley rotational angle reduces the zero-lift angle of attack, while keeping the slope between the lift coefficient and angle of attack the same. A shorter morphing region closer to the trailing edge is beneficial for generating larger lift coefficient with the same tendon moment and angle of attack. Flutter occurs with the increase of the air speed. When the morphing end position is fixed at 0.9 chord, increasing the morphing length reduces the critical flutter speed significantly, with the second bending mode tending to drive instability. With the same morphing length, moving the morphing region closer to the leading edge increases the critical flutter speed, and the unstable mode changes from the second mode into the first mode.

Dynamic modeling of curved fish bone active camber morphing concept using shallow shell theory and negative-stiffness artificial springs

Dynamic modeling of curved fish bone active camber morphing concept using shallow shell theory and negative-stiffness artificial springs

Unleashing the Potential of Morphing Wings: A Novel Cost Effective Morphing Method for UAV Surfaces, Rear Spar Articulated Wing Camber

The implementation of morphing wing applications in aircraft design has sparked significant interest as it enables the dimensional properties of the aircraft to be modified during flight. By allowing manipulation of the 2D and 3D parameters on the aircraft’s wings, tail surfaces, or fuselage, a variety of possibilities have arisen. Two primary schools of thought have emerged in the field of morphing wing applications: the mechanisms school and the smart surfaces approach that uses shape-memory materials and smart actuators. Among the research in this field, the Fishbone Active Camber (FishBAC) approach has emerged as a promising avenue for controlling the deflection of the wing’s trailing edge. This study revisits previous research on morphing wings and the FishBAC concept, evaluates the current state of the field, and presents an original design process flow that includes the design of a unique and innovative UAV called the Stingray within the scope of the study. A novel morphing concept developed for the Stingray UAV, Rear Spar Articulated Wing Camber (RSAWC), employs a fishbone-like morphing wing rib design with rear spar articulation in a cost-effective manner. The design process and flight tests of the RSAWC are presented and directly compared with a conventional wing. Results are evaluated based on performance, weight, cost, and complexity. Semi-empirical data from the flight testing of the concept resulted in approximately a 19% flight endurance increment. The study also presents future directions of research on the RSAWC concept to guide the researchers.

Development of an analytical model for the flexural vibration of fish bone active camber structures with truncated, variable thickness partitions

The need for smooth, gapless mechanisms that offer superior aerodynamic performance has been the prime mover for a wide range of studies on the morphing concepts from the early years of the twenty-first century. In light of the importance of novel analytic means for inspecting such structures, this article describes a comprehensive dynamic model for the flexural vibration of a special type of morphing structure known as fish bone active camber (FishBAC). In view of the shortcomings of previous models, the developed procedure considers the variable thickness of the central spine of FishBAC as well as the possibility of arbitrary truncations in its numerous partitions to offer more accurate results. A general idea is first proposed based on the assumptions of classical plate theory for such partitioned structures. The equations are derived using the energy method and the assumption of artificial springs to satisfy the continuity of shear force and bending moment along the connecting lines between partitions. A robust Rayleigh-Ritz method along with a set of fast-converging admissible functions is presented to solve the governing equations of motion. Combined with the power of Mathematica and validated by other analytic models and finite element codes, this technique can be used to deal with a plethora of similar systems while paving the path for the dynamic analysis of FishBAC built around various airfoils.

Design, Manufacture and Wind Tunnel Test of a Modular FishBAC Wing with Novel 3D Printed Skins

This paper introduces a new modular Fish Bone Active Camber morphing wing with novel 3D printed skin panels. These skin panels are printed using two different Thermoplastic Polyurethane (TPU) formulations: a soft, high strain formulation for the deformable membrane of the skin, reinforced with a stiffer formulation for the stringers and mounting tabs. Additionally, this is the first FishBAC device designed to be modular in its installation and actuation. Therefore, all components can be removed and replaced for maintenance purposes without having to remove or disassemble other parts. A 1 m span, 0.27 m chord morphing wing with a 25% chord FishBAC was built and tested mechanically and in a low-speed wind tunnel. Results show that the new design is capable of achieving the same large changes in airfoil lift coefficient (approximate ΔCL≈0.55) with a low drag penalty seen in previous FishBAC work, but with a much simpler, practical and modular design. Additionally, the device shows a change in the pitching moment coefficient of ΔCM≈0.1, which shows the potential that the FishBAC has as a control surface.

Experimental Aerodynamic Comparison of Active Camber Morphing and Trailing-Edge Flaps

Unlike hinged flaps (for example, ailerons, elevators, and rudders), camber morphing devices vary camber distribution in a smooth and continuous way, resulting in aerodynamic efficiency improvements due to the absence of sharp changes in airfoil camber. One such camber morphing concept, the Fish Bone Active Camber (FishBAC) device, has shown significant aerodynamic benefits when compared to a flap. In this work, a quasi-two-dimensional wind-tunnel test was performed to investigate the aerodynamic performance of a FishBAC device and compare it to a trailing-edge plain flap. A combination of quasi-steady force balance and wake rake pressure measurements was used to determine aerodynamic force coefficients. These measurements are complemented by a flow visualization study performed using particle image velocimetry, allowing for comparison of the near-field wakes in terms of size and vortical structure. Additionally, displacement measurements were performed on the FishBAC to track deformed shapes under aerodynamic loads. Results show that the FishBAC achieves greater than a 50% improvement in lift-to-drag ratio for moderate to high lift coefficients where the device is significantly deflected and an at least 16% higher lift-to-drag ratio at all lift coefficients, even when the device deflections are low.

Structural Modeling of Compliance-Based Camber Morphing Structures Under Transverse Shear Loading

A parametrically driven structural model based on Mindlin–Reissner plate theory is developed to capture the three-dimensional deflections of a compliance-based morphing trailing edge device with severe structural discontinuities. The model is used to study the Fish Bone Active Camber (FishBAC) device, which is represented as a discontinuous plate structure that captures the step changes in stiffness created by the concept’s geometrical configuration. Courant’s penalty method is implemented in the form of artificial penalty springs to account for stiffness discontinuities. A numerical validation is performed using finite element analysis, followed by experimental validation under actuation loads. This analytical model represents a robust, efficient, mesh-independent, and parameter-driven solution to modeling discontinuous plate structures. These traits make it useful for ongoing fluid–structure interaction analysis and optimization of the FishBAC concept and also for application to other complex composite structures.

Switchable stiffness morphing aerostructures based on granular jamming

One of the persistent challenges facing the development of morphing aerostructures is the need to have material and structural solutions which provide a compromise between the competing design drivers of low actuation energy and high stiffness under external loads. This work proposes a solution to this challenge in the form of a novel switchable stiffness structural concept based on the principle of granular jamming. In this article, the concept of using granular jamming for controlling stiffness is first introduced. Four-point bending tests are used to obtain the flexural rigidity and bending stiffness of three different granular materials under different levels of applied vacuum loading. Nonlinear finite element analysis simulations using experimentally derived nonlinear material properties show good agreement with experiment. A specific application of this concept is then proposed based on the Fish Bone Active Camber morphing airfoil. A unit cell of this concept is built, tested and analysed, followed by the first prototype of a complete switchable stiffness Fish Bone Active Camber morphing airfoil, which is experimentally shown to be able to achieve an increase in stiffness of up to 300% due to granular jamming.

Parametric structural modelling of fish bone active camber morphing aerofoils

Camber morphing aerofoils have the potential to significantly improve the efficiency of fixed and rotary wing aircraft by providing significant lift control authority to a wing, at a lower drag penalty than traditional plain flaps. A rapid, mesh-independent and two-dimensional analytical model of the fish bone active camber concept is presented. Existing structural models of this concept are one-dimensional and isotropic and therefore unable to capture either material anisotropy or spanwise variations in loading/deformation. The proposed model addresses these shortcomings by being able to analyse composite laminates and solve for static two-dimensional displacement fields. Kirchhoff–Love plate theory, along with the Rayleigh–Ritz method, are used to capture the complex and variable stiffness nature of the fish bone active camber concept in a single system of linear equations. Results show errors between 0.5% and 8% for static deflections under representative uniform pressure loadings and applied actuation moments (except when transverse shear exists), compared to finite element method. The robustness, mesh-independence and analytical nature of this model, combined with a modular, parameter-driven geometry definition, facilitate a fast and automated analysis of a wide range of fish bone active camber concept configurations. This analytical model is therefore a powerful tool for use in trade studies, fluid–structure interaction and design optimisation.

Structural and Aerodynamics Studies on Various Wing Configurations for Morphing

The current aircraft industry, specially unmanned aerial vehicles, is shifting from fixed wing vehicles to morphed wing. Morphing wings can create smoother aerodynamic surfaces, making an aircraft more agile and efficient than an aircraft that flies with many discrete moving surfaces. In present study, a double corrugated variable camber configuration of morphing wing with trailing edge morphing sections are proposed. The two configurations available from literature; one Fish Bone Active camber concept and other is variable camber morphing wing composed of single corrugated structure is considered for comparison of structural and aerodynamic analysis. The structural analysis of all prototype models is done using finite element analysis with actuation mechanism. Aerodynamic analysis is done using two methods; one analytical approach based on thin airfoil theory, and the other one is numerically using XFOIL, which couples a potential-flow panel method with viscous boundary-layer solver. A comparison is done on the basis of stress and deformation developed in various parts of the models. The results show that the double corrugated variable camber morphing configuration can take more structural load without harmful deformation. The aerodynamic analysis also shows that the aerodynamic efficiency of double corrugated variable camber morphing configuration is higher compared to other configurations.

Multi-objective geometry optimization of the Fish Bone Active Camber morphing airfoil

This work presents the development of a design optimization code for the geometry of the Fish Bone Active Camber morphing airfoil concept, which has been under development at Swansea University. This concept employs a biologically inspired architecture to provide highly anisotropic structural compliance, which creates smooth and continuous camber changes of large magnitude. Previous work has shown that this concept is capable of large lift coefficient control authority and significant reductions in drag over traditional trailing edge flaps. Further development of the concept requires a more robust design methodology that allows for an automated and thorough search of the available design space in order to optimize the aero-structural and system-level performance of the concept. To this end, this research extends a previously developed fluid–structure interaction analysis into a useful design tool by embedding it within a multi-objective structural optimization routine based on a genetic algorithm. The three objective functions of aerodynamic drag, added mass, and actuation energy are minimized concurrently. Example results from a specific operating condition are shown. Examination of the Pareto frontiers and the objective values of the population at large give insight into the structural behavior of the morphing concept. The objectives of mass and energy are found to be strongly competing, but good compromise points exist. The drag objective is found to be less sensitive than the others, with low drag being achievable across a range of designs with both low mass and low energy requirements, although the Pareto frontiers formed are not as well populated with regard to drag.

Performance Comparison between Optimised Camber and Span for a Morphing Wing

Morphing technology offers a strategy to modify the wing geometry, and the wing planform and cross-sectional parameters can be optimised to the flight conditions. This paper presents an investigation into the effect of span and camber morphing on the mission performance of a 25-kg UAV, with a straight, rectangular, unswept wing. The wing is optimised over two velocities for various fixed wing and morphing wing strategies, where the objective is to maximise aerodynamic efficiency or range. The investigation analyses the effect of the low and high speed velocity selected, the weighting of the low and high velocity on the computation of the mission parameter, the maximum allowable span retraction and the weight penalty on the mission performance. Models that represent the adaptive aspect ratio (AdAR) span morphing concept and the fish bone active camber (FishBAC) camber morphing concept are used to investigate the effect on the wing parameters. The results indicate that generally morphing for both span and camber, the aerodynamic efficiency is maximised for a 30%–70% to 40%–60% weighting between the low and high speed flight conditions, respectively. The span morphing strategy with optimised fixed camber at the root can deliver up to 25% improvement in the aerodynamic efficiency over a fixed camber and span, for an allowable 50% retraction with a velocity range of 50–115 kph. Reducing the allowable retraction to 25% reduces the improvement to 8%–10% for a 50%–50% mission weighting. Camber morphing offers a maximum of 4.5% improvement approximately for a velocity range of 50–90 kph. Improvements in the efficiency achieved through camber morphing are more sensitive to the velocity range in the mission, generally decreasing rapidly by reducing or increasing the velocity range, where span morphing appears more robust for an increase in velocity range beyond the optimum. However, where span morphing requires considerable modification to the planform, the camber change required for optimum performance is only a 5% trailing edge tip deflection relative to cross-sectional chord length. Span morphing, at the optimal mission velocity range, with 25% allowable retraction, can allow up to a 12% increase in mass before no performance advantage is observed, where the camber morphing only allows up to 3%. This provides the designer with a mass budget that must be achieved for morphing to be viable to increase the mission performance.

Aerodynamic optimisation of a camber morphing aerofoil

An aircraft that has been carefully optimised for a single flight condition will tend to perform poorly at other flight conditions. For aircraft such as long-haul airliners, this is not necessarily a problem, since the cruise condition so heavily dominates a typical mission. However, other aircraft such as UAVs, may be expected to perform well at a wide range of flight conditions. Morphing systems may be a solution to this problem, as they allow the aircraft to adapt its shape to produce optimum performance at each flight condition. Optimisation of morphing aerofoils is typically performed separately to the morphing mechanism design. In this work, an optimisation strategy is developed to account for a known possible morphing system within the aerodynamic optimisation process itself. This allows for the limitations of the system to be considered from the start of the design process. The Fishbone Active Camber (FishBAC) camber morphing system is chosen as the example mechanism, and it is shown that the FishBAC can achieve large improvements in performance over non-morphing aerofoils when multiple flight conditions are considered. Additionally, its performance is compared to an aerofoil whose shape can change arbitrarily (as if a perfect morphing mechanism can be designed), and it is shown that the FishBAC performs nearly as well, despite being a relatively simple mechanism.

Wind tunnel testing of the fish bone active camber morphing concept

This work presents comparative experimental investigations into the aerodynamics of the recently proposed Fish Bone Active Camber morphing structure. This novel, biologically inspired concept consists of four main elements: a compliant skeletal core, a pre-tensioned elastomeric matrix composite skin, an antagonistic pair of tendons coupled to a non-backdriveable spooling pulley as the driving mechanism, and a non-morphing main spar. The Fish Bone Active Camber concept is capable of generating large changes in airfoil camber and is therefore proposed as a high-authority morphing solution for fixed-wing aircraft, helicopters, wind turbines, tidal stream turbines, and tilt-rotors. This testing compares a baseline airfoil employing a conventional trailing edge flap to a continuous morphing trailing edge using the Fish Bone Active Camber concept. Testing is performed in the low-speed wind tunnel at Swansea University over a range of camber deformations and angles of attack. Both approaches are capable of generating similar levels of lift coefficient; however, comparison of the drag results shows a significant reduction for the Fish Bone Active Camber geometry. While purely two-dimensional flow was not achieved due to restrictions of the tunnel, the two airfoils operated in similar flow environments, allowing for a direct comparison between the two. Over the range of angles of attack typically used in fixed and rotary wing applications, improvements in the maximum obtainable lift-to-drag ratio on the order of 20%–25% are shown.

Advanced Kinematic Tailoring for Morphing Aircraft Actuation

Morphing aircraft concepts require powerful, compact, and lightweight actuators in order to realize the significant changes in the shape and aerodynamics desired. One source of inefficiency and lost performance common to all types of actuators is the mismatch between the force-versus-stroke profile available from the actuator and that required by the load. This work investigates a novel spiral spooling pulley mechanism that allows for kinematic tailoring of the actuator force profile to better match the force required to drive a given load. To show the impact of kinematic tailoring on actuator efficiency, a representative case study is made of a pneumatic artificial muscle-driven morphing camber airfoil employing the fish bone active camber concept. By using an advanced spiral pulley kinematic mechanism, the actuator force profile is successfully tailored to match the morphing actuation torque required, with an additional torque margin added to account for any unmodeled effects. Genetic algorithm optimization is used to select the geometric parameters of the spiral pulley that maximize the energy efficiency of the actuator while ensuring it is able to produce the required torque levels. The performance of the optimized spiral pulley is compared to a baseline case employing an optimized circular pulley, which does not alter the shape of the actuator force profile, to show the performance improvement provided by the kinematic tailoring.