Special Session O-10/P-6
Biomimetic Morphing of  Unmanned Aerial Vehicles


O-10/P-6:IL01  Bio-inspired State Sensing and Awareness for Morphing Fly-by-feel UAVs
F. KOPSAFTOPOULOS, R. NARDARI, YU-HUNG LI, FU-KUO CHANG, Department of Aeronautics and Astronautics, Stanford University, Stanford, CA, USA

Bio-inspired intelligent materials with state-sensing and awareness capabilities constitute the future of morphing aerospace structures. The objective of this work is the development of innovative technologies that will lead to the next generation of morphing “fly-by-feel” UAVs. These UAVs will be able to feel, think, and react in real time based on high-resolution state-sensing and awareness capabilities. They will be able to sense the environmental conditions and structural state, effectively interpret the sensing data in real time, and appropriately adjust their shape and geometry under dynamic operational environments. In this paper, the design, integration, and wind-tunnel experimental assessment are presented for a smart “fly-by-feel” UAV wing. Bio-inspired stretchable sensor networks are monolithically embedded in the composite layup to provide the sensing capabilities. Signal processing and machine learning techniques are employed to accurately interpret the sensing data and enable morphing functions. The experimental assessment is demonstrated via a series of wind tunnel experiments under varying conditions. The obtained results demonstrate the successful integration of the developed technologies towards a paradigm shift for the next generation of fly-by-feel UAVs.

O-10/P-6:IL02  Shape Memory Alloy- and Piezoelectric-based Adaptive Structures for Morphing Aircraft and Wind Turbine Rotors
D.A. SARAVANOS, Department of Mechanical Engineering & Aeronautics, University of Patras, Patras, Greece

Shape memory alloys (SMA) and piezoelectric materials provide common solid state actuators with reliable and unique characteristics. SMA actuators are based on a reversible phase transformation and can provide high power density, induced strain and block forces which render them indispensable for actuating morphing structures requiring large shape changes and space and weight restrictions are imposed. On the other hand, piezoelectric actuators provide high rates of response and precision, yet with low strains and block forces. Yet, their implementation into morphing structures faces challenges related to their complex multi-disciplinary behavior, their interaction with geometrical structural nonlinearity, and lack of modelling tools which may robustly simulate their complex behavior and make feasible their design. Developed specialty finite elements are presented capable to model the complex thermomechanical response of SMA actuators and the electromechanical response of piezoelectric actuators in morphing structures undergoing large shape shapes under severe geometric nonlinearity, which substantially changes their anticipated behavior. To demonstrate the morphing capabilities and opportunities, three different morphing applications are subsequently presented: a morphing chevron with SMA wire actuators to attenuate jet noise in aircraft engines; a morphing turbine blade airfoil for unsteady aerodynamic load control and fatigue alleviation; and finally a curved multi-stable morphing composite skin shell with piezoelectric actuators.  The challenging task to adapt the structural shape to time varying demands, dictates the use of antagonistic actuator configurations to maximize and control the range of morphing. The previously mentioned advanced modelling techniques have been adopted to overcome the raised obstacles regarding the multiple target morphing shapes and the controlled time trajectory response.

O-10/P-6:L03  Vision-based Fuzzy Controller for the Quadrotor Tracking a Ground Target
XUCHAO CHEN1, ZHIQIANG CAO1, YUEQUAN YANG2, CHAO ZHOU1, MIN TAN1, 1Institute of Automation, Chinese Academy of Sciences, Beijing, China; 2College of Information Engineering,Yangzhou University, China

Quadrotors are a special type of UAV, which finds a wide variety of applications including aerial photography, traffic surveillance, resource exploration. In this paper, a vision-based fuzzy controller for a quadrotor is proposed to realize ground target tracking. Due to the underactuated property of quadrotors as well as the coupled dynamics in the image plane, it is more challenging to design an image-based visual servoing controller for the quadrotor. Because of the nonlinear relationship between the control variable (image features) and the target variable (tilt angles) as well as the complexity of aerodynamics, the traditional model-based controllers are not feasible anymore. Since the fuzzy control does not require an accurate model, a fuzzy-based approach is presented to solve the image-based tracking problem. Fuzzy controllers take the corresponding image feature as input and its output is used to control the quadrotor in a form of tilt angles adjustment. The task requires that a quadrotor tracks a ground target. The target is attached with an image identifier and its feature points are extracted to compute image features. The output of the proposed controller is sent wirelessly to the quadrotor to control its position. The proposed approach is verified by experiments.

O-10/P-6:L04  Parylene Flapping-wings with Self-organized Micro Wrinkles
H. TANAKA, Tokyo Institute of Technology, Tokyo, Japan; Y. SHIMASUE, I. KITAMURA, H. LIU, Chiba University, Chiba, Japan

Flapping-wing aerial robots inspired from natural flyers such as birds, bats, and insects have been widely studied aiming for small and agile unmanned aerial vehicles. The flapping wings must be light in weight in order to reduce the inertia force acting at the timing of stroke reversals, while the wing structure should be sufficiently stiff in order to maintain the wing shape. Typical artificial wings are composed of a lightweight and thin polymer film. The wing film, however, needs to be supported with stiff framework such as CFRP (carbon fiber-reinforced plastic) ribs which are source of the weight gain. In this study, a Parylene wing film with unidirectional micro wrinkles was designed and fabricated. Like barbules of a bird feather or corrugations of an insect wing, the micro wrinkles enhance the flexural stiffness of the film with the minimum increase in weight. A self-organisation phenomenon was exploited in the fabrication of the micro wrinkles such that microscale wrinkles spanning a broad wing area were spontaneously created. Experiments using a hummingbird-sized tethered flapping mechanism revealed that the chordwise wrinkles prevent fluttering near the trailing edge resulting in increase in lift and efficiency.

O-10/P-6:IL05  Artificial Hair Sensors - Bioinspired Flight Control Feedback
B. DICKINSON, United States Air Force Research Laboratory, Eglin Air Force Base, FL, USA

Unmanned aircraft maneuverability and stability is challenged by unsteady aerodynamic forces and moments, uncertainty in aerodynamic data, and external disturbances due to wind or turbulence. Biological studies connect arrays of microscale flow-sensitive hair to the controlled and stable flight of the bat, locust, and other animals. The response of hair structures may be mathematically related to various flow properties and numerous research groups have established distinct materials and methods for microscale artificial hair sensor (AHS) fabrication. This presents a new opportunity to explore distributed flow sensing for flight control. The outstanding challenge is how to construct a control architecture that relates distributed flow information to an appropriate aircraft control action. We will present a carbon nanotube forest based AHS for unmanned aircraft applications. We will compare and contrast the AHS array concept to modern aerodynamic measurement technology. Finally, we will discuss how distributed flow feedback may be an alternative or complementary approach to aircraft control and the implications for system level performance and robustness.

O-10/P-6:IL06  Aquatic Micro Aerial Vehicles (AquaMAV): From Diving Birds and Flying Fish to Aerial-aquatic Robots
M. KOVAC, Aerial Robotics Laboratory, Imperial College London, London, UK

Most robots are designed to either move in air or in water. Multi-modal mobility in both air and water and across fluid boundaries would allow for unprecedented mission capabilities that can not be done with only flying or swimming robots. For example, it would enable autonomous water sampling in inaccessible coastal areas, between floating ice in the arctic sea and during urban flooding situations where obstacles in the water inhibit access with single-mode robots. However, the conflicting design requirements for operation in air and water has prevented the demonstration of a fully functional aerial-aquatic robot. In this talk, I will present how biological inspiration can help in the design of such vehicles and what we can learn from aerial-aquatic animals to build multi-modal robots. I will also present the current state of the Aquatic Micro Aerial Vehicle (AquaMAV) research at Imperial College London where we demonstrated successful transition principles from air to water and back to air enabling aerial-aquatic mobility in robotics.

O-10/P-6:L07  Hybrid Fiber Reinforced Composite with Embedded Functionality
M.H. MALAKOOTI, Department of Aerospace Engineering, University of Michigan, Ann Arbor, MI, USA; B.A. PATTERSON, HYUN-SIK HWANG, Department of Materials Science and Engineering, University of Florida, Gainesville, FL, USA; H.A. SODANO, Department of Aerospace Engineering, Department of Materials Science and Engineering, University of Michigan, Ann Arbor, MI, USA

Here, a novel hierarchical composite with embedded functionality is developed. The unique design of this composite has integrated nanostructured piezoceramics that enables energy harvesting from vibrations while increasing the mechanical strength of the fiber reinforced polymer composite. The fabrication methodology of these multifunctional composites is simple, versatile, and cost effective. In this process, zinc oxide nanowires are grown on aramid fibers to serve as energy harvesting units while improving the interfacial properties. The modified aramid fabric is sandwiched between carbon fabrics, as top and the bottom electrodes as well as polymer matrix reinforcement. The increased weight due to the interface modification is negligible; however, this augmentation enables the composite to be an energy harvester capable of continuous power generation under a harmonic base vibration. Furthermore, the structural performance of the developed composite is examined through tensile tests. The results indicate that significant enhancements in both tensile strength and elastic modulus of the composite are due to the embedded nanostructures. The developed composite is the first demonstration of materials where an integrated functionality increases the load-bearing capability.

O-10/P-6:L08  Yaw Control of a Smart Morphing Tailless Aircraft Concept
L.L. GAMBLE, D.J. INMAN, University of Michigan, Ann Arbor, MI, USA

Aircraft morphing with regard to UAVs has become a popular concept; however, only a limited amount of research has been conducted on its effect on tailless aircraft. This is partly due to aerodynamic compromises such as instabilities that arise in the absence of a vertical stabilizer. Yet, birds readily adapt to adverse flight conditions without vertical stabilizers and are unhindered with respect to stability and maneuvering due to their smooth continuous shape change and rapid muscle response. This research, motivated by the discrepancy between manmade and natural flight designs, focuses on the development and analysis of a smart morphing horizontal tail. The physical model was developed using piezoelectric Macro Fiber Composites (MFCs), coupled with thin fiber laminates to achieve bending-twisting coupling capable of mimicking the shape change of bird tails. Unlike many other smart materials, MFC’s large bandwidth properties allow for a response time comparable to muscle, making it an excellent choice for the following experiments. Experimental tests were conducted on the morphing tail section in a wind tunnel to determine its control derivatives at a variety of deflection configurations. Forces were measured and three-dimensional deformation was recorded with a Vicon system. 

O-10/P-6:IL09  Bioinspired Morphing Systems and Multi-functionality
J. KUDVA, NextGen Aeronautics, Inc., Torrance, CA, USA; G. Spedding, University of Southern California; R. Kornbluh, SRI International

The basic idea of a morphing aircraft wherein the vehicle changes its shape and state to perform optimally in multiple flight segments holds the promise of unprecedented levels of efficiency. Multiple concepts have been studied by a wide variety of researchers – materials scientists, zoologists, aerospace engineers, and others – over the past 2 decades. Many were inspired by bird flight and motivated by continuing the development of multifunctional materials. Bird wings morph in 3-D with large changes in wing camber, span, and other geometric parameters. With such morphing, birds can efficiently deal with multiple flight conditions. While morphing technologies have been extensively studied in the US and EU for large military and commercial aircraft, the combination of birdlike flight and multifunctional materials are better suited for UAVs with weights and sizes similar to birds. Such UAVs would be able to fly and maneuver in urban and indoor environments, which is difficult to do with the current generation of fixed wing UAVs. Also, with lower power requirements, multifunctional materials become more attractive. This talk will address challenges and benefits of developing bioinspired morphing systems enabled by multifunctional materials and present a few design concepts.

O-10/P-6:IL10  Morphing Aircraft Skin Based on a Woven Strip Structure
H. TOKUTAKE, Kanazawa University, Kanazawa, Japan

Recently, shape-adaptive aircrafts have been widely researched. Several morphing techniques using smart materials or mechanical structures have been proposed. However, these methods are difficult to apply to shape-adaptive aircrafts. A shape-adapting system with low weight and high loadability, which transforms the shape of the body and wing smoothly and to a large extent, is required to be implemented. We propose a new morphing device, called Woven Strip Structure (WSS), which comprises a three-dimensional structure constructed using tailored woven composite strips that allow the slip between materials. The shape of this structure can be adjusted using small actuators. This morphing device is applied to the aerodynamic control of an Unmanned Aerial Vehicle (UAV). The morphing device is implemented at the sensitive position of the UAV surface, which results in the advantageous aerodynamic phenomena. In this study, the proposed morphing device is constructed, and deformation experiments and load testing are performed. The initial shape, stiffness, and damping ratio can be designed by tailoring the composite strips. A fundamental model and design tools of the proposed system are constructed and validated.

Cimtec 2016

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