Brian Smyers

Variable Camber Compliant Wing - Wind Tunnel Testing

This paper describes initial wind tunnel testing of a Variable Camber Compliant Wing developed by the U.S. Air Force Research Laboratory. The current version of the Variable Camber Compliant wing has a two foot chord length and was designed to demonstrate the ability to actively change wing section camber at low flight speed. The intent of the design was to adjust the wing camber by six percent chord while holding maximum camber location, and maximum thickness constant (emulating a change from a NACA 2410 to NACA 8410 profile) using a single continuous outer skin. The design is unique; the entire skin is seamless, continuous, and made of a single piece of non-stretchable composite skin. Smooth elastic deformation of the wing is attained by the underlying compliant mechanism. 2D camber change is achieved by a single actuation direction to control both leading and trailing edge deflection. 3D shape change is also capable through variation of camber along the span wise direction using a distributed actuation system along the span. Relatively low speed design and testing conditions were chosen to support air vehicle noise modeling efforts, for which low speed flight results in lower noise. Wing shape change without aerodynamic load was measured using an optical measurement system, indicating nearly six percent camber change measured at the middle rib. The wing was tested in the U.S. Air Force Vertical Wind Tunnel Facility in order to demonstrate operation of the wing under aerodynamic load. Increasing the profile camber resulted in an increase in section lift coefficient and vice versa. The variable camber wing is an inherently flexible structure that deforms under aerodynamic load. Digital image correlation of the model with wind off and wind on was used to understand the flexibility of the structure and its effect on aerodynamic forces. Aerodynamic modeling of the wings actual windoff shape and wind on shape are used to provide insight into the wind tunnel results and discuss the complexity of aerodynamic measurements on a flexible structure.

Aerodynamic parameters from distributed heterogeneous CNT hair sensors with a feedforward neural network

Distributed arrays of artificial hair sensors have bio-like sensing capabilities to obtain spatial and temporal surface flow information which is an important aspect of an effective fly-by-feel system. The spatiotemporal surface flow measurement enables further exploration of additional flow features such as flow stagnation, separation, and reattachment points. Due to their inherent robustness and fault tolerant capability, distributed arrays of hair sensors are well equipped to assess the aerodynamic and flow states in adverse conditions. In this paper, a local flow measurement from an array of artificial hair sensors in a wind tunnel experiment is used with a feedforward artificial neural network to predict aerodynamic parameters such as lift coefficient, moment coefficient, free-stream velocity, and angle of attack on an airfoil. We find the prediction error within 6% and 10% for lift and moment coefficients. The error for free-stream velocity and angle of attack were within 0.12 mph and 0.37 degrees. Knowledge of these parameters are key to finding the real time forces and moments which paves the way for effective control design to increase flight agility, stability, and maneuverability.

Aerodynamic Parameter Prediction on a Airfoil with Flap via Artificial Hair Sensors and Feedforward Neural Network

Gust alleviation and flutter suppression are essential elements of an effective fly-by-feel system. Knowledge of real-time forces and moments can have huge effect on designing an effective controller for flutter suppression and gust rejection. One unique method of predicting forces and moments is to use distributed arrays of artificial hair sensors that are capable of sensing the environment and therefore capturing important flow features. In this paper, the local flow measurement from the artificial hair sensor is used with feed-forward neural network to predict the aerodynamic parameters (angle of attack, freestream velocity, lifte coefficient and moment coefficient per unit span, and flap angle) on an airfoil containing control surface. These aerodynamic parameters can be combined with the airfoil’s physical parameters to predict the real time lift and moment. Also, the effect of artificial hair sensor integration location on prediction of aerodynamic parameters is studied.

Aerodynamic Characteristics Prediction via Artificial Hair Sensor and Feedforward Neural Network

Fly by feel is a concept in which distributed sensors and actuators are integrated on an aerial system for state awareness or sensation of the environment, and make use of distributed control to increase the system maneuverability, stability and safety. Artificial hair sensors are good candidates as sensors for the fly by feel concept because they are lightweight, have low manufacturing costs and can easily be integrated on the surface of air-vehicle without affecting the flow. We investigate an application of artificial hair sensors considering its capability of measuring the local flow velocity combined with a Feedforward Artificial Neural Network to predict the aerodynamic quantities such as lift coefficient, moment coefficient, angle of attack and free-stream velocity in real-time. These quantities, when combined with the physical and unsteady aerodynamics parameters, will make a framework for designing and implementing an active controller for gust alleviation in a pitch and plunge airfoil system.Copyright

Thermal Properties of Magnetite Nanoparticle and Carbon Fiber Doped Epoxy Shape Memory Polymer

Presented are the results of an experimental investigation into the effects of particle and carbon fiber (CF) doping in epoxy shape memory polymer (SMP). Motivation for the work originates from the need to increase the thermal performance, and thus decrease the time required to transition the polymer given a finite amount of thermal energy, of a SMP link in a bi-stable linkage. Such a multi-functional link is responsible for structural support, mechanism reconfigurability, as well as system damping. Thus any improvement in thermal properties must be weighed against increases in brittleness and weight as well as altered mechanical properties as a result of the chosen method. Two part epoxy SMP by CRG Industries is doped with Fe3 O4 (magnetite) nanoparticles (20–30nm spheres) at a weight fraction of 10% as well as 3mm and 10mm carbon fibers at a weight fraction of 5.4%; resulting in all dopants having a volume fraction of approximately 2.5%. The thermal conductivity, specific heat, and diffusivity are experimentally measured by a Hot Disk Thermal Constants Analyser from ambient through transition and the results compared with several thermal composite models. Changes in the thermal properties of the composites and neat polymers with respect to temperature are presented and the effects these changes have on the predictions of thermal models discussed, specifically the effect of changes in thermal properties near the transition temperature and the resulting change in predicted energy required for transition. The effects of adhesion between the particles and the matrix and particle dispersion on conductive paths and material thermal properties are also discussed.Copyright

Design, modeling, and optimization of a thermally activated reconfigurable wing system

Reconfigurable structures such as morphing aircraft generally require an on-board energy source to function. At high speeds, however, frictional heating generated at the nose of a morphing aircraft can provide a large amount of thermal energy during a short period of time. This thermal energy can be collected, transferred, and utilized to reconfigure the aircraft. Direct utilization of thermal energy has the ability to significantly decrease or eliminate the losses associated with converting thermal energy to other forms, such as electric. The following work describes possible system designs and components that can be utilized to transfer the thermal energy harvested at the nose of the aircraft to internal components for direct thermal actuation of a reconfigurable wing structure. Previously reported topology optimized heat collectors, vehicle trajectories, and the deployment mechanism are combined with the presented analytical model of a heat pipe for a system level model used to optimize the system based on weight and the desired wing deployment time.

System Design and Modeling of a Thermally Activated Reconfigurable Wing

Abstract : Reconfigurable structures such as morphing aircraft generally require an on board energy source to function. Frictional heating during the high speed deployment of a blunt nosed low speed reconnaissance air vehicle can provide a large amount of thermal energy during a short period of time. This thermal energy can be collected, transferred, and utilized to reconfigure the deployable aircraft. Direct utilization of thermal energy has the ability to significantly decrease or eliminate the losses associated with converting thermal energy to other forms, such as electric. The following work attempts to describe possible system designs and components that can be utilized to transfer the thermal energy harvested at the nose of the aircraft during deployment to internal components for direct thermal actuation of a reconfigurable wing structure. A model of a loop heat pipe is presented and used to predict the time-dependant transfer of energy. Previously reported thermal profiles of the nose of the aircraft, calculated based on trajectory and mechanical analysis of the actuation mechanism, are reviewed and combined with the model of the thermal transport system providing a system level feasibility investigation and design tool. The efficiency, implementation, benefits, and limitations of the direct use thermal system are discussed and compared with currently utilized systems.

Thermally-Activated Reconfigurable Wing Design Using a Non-monolithic Compliant Mechanism

Morphing aircraft and reconfigurable structures are multidisciplinary systems that require efficient integration of actuation systems, mechanisms, and structures to achieve the desired functionality and the state change of the vehicle to accomplish a wide range of mission roles. Typically, the actuation required to achieve this functionality comes from an on-board energy source, converted to mechanical force and motion. In this case, the ability to operate in response to environment change requires radically new structural concepts for system level capability. This paper seeks to understand new concepts that utilize environmental thermal energy to trigger reconfiguration and employ a fundamental bistable effect of compliant mechanisms for shape change. For this study, available heat energy on the surface of the re-entry vehicle with a blunt fuselage shape is investigated including the duration of the heat generation to determine the best energy conversion. A compliant mechanism will be designed to change its configuration by opening the heat shield and deploying a folded wing as the induced heat load expands elements to reach an unfolded stable position. The size and shape of the mechanism are explored and analyzed using an energy method and the material selection of the flexible link is discussed.